Anatomy & Physiology for Midwives 3: Third Edition

Chapter 2. The reproductive and urinary systems

Learning objectives

• To describe the structure and function of the urinary system.

• To compare the structure of the female and male reproductive systems.

• To identify differences between the male and female reproductive tracts in relation to reproduction and adaptations to facilitate childbirth.

Introduction

This chapter reviews the basic anatomy of human reproductive and urinary systems. The human urinary system differs only slightly between the male and female, mostly in relation to the structure of the external genitalia. The function of the urinary system is also essentially the same in men and women. However, the renal system can be severely stressed by pregnancy, mostly because of its close proximity to the reproductive organs and the major changes in fluid balance resulting in fluid retention during pregnancy. The midwife needs to know the basics of normal renal physiology in order to understand the changes that take place in the renal system during pregnancy and how these may affect the general condition of the woman. For example, not only are the regulation and retention of fluid altered in pregnancy but also excretion of glucose and other substances is affected by these changes. Drug excretion via the kidneys may also be affected, so long-term medication may need to be changed as pregnancy progresses. The effectiveness of medication may be reduced and altered drug dosage may also be required. (Specific changes in the renal system in pregnancy are covered in Chapter 11.)

Chapter case study

Zara, during the booking appointment, is asked by the midwife to provide a mid stream specimen of urine to screen for infection. The midwife notes that the specimen appears cloudy although Zara does not have any other signs of a urinary tract infection.

• Are there any reasons apart from infection that could explain the cloudiness of the specimen?

• If the culture of the specimen proves positive, how will this be managed and what advice should the midwife give to Zara?

• If the analysis of the specimen showed a bacteraemia of group B haemolytic streptococcus what would be the significance of this, how should it be managed and what are the possible future consequences for Zara and her baby?

The urinary system

The urinary system is composed of two kidneys, which produce urine, two ureters running from the kidneys to the bladder, which collects and stores the urine, and a urethra from which urine is discharged to the exterior (Fig. 2.1). The uroepithelium which lines the renal pelvis, ureters and bladder is not just a passive impermeable barrier; it can modulate the composition of urine and also transmit information about pressure and composition of the urine to the underlying nervous and muscular tissue (Khandelwal et al., 2009).

The kidneys have a broad range of other functions (see Box 2.1) as well as producing urine. The kidneys are situated upon the posterior wall of the abdominal cavity, one on either side of the vertebral column at the level of the thoracic and lumbar vertebrae (just below the rib cage). The right kidney is slightly lower than the left owing to its relationship to the liver. Each kidney is about 10 cm long, 6.5 cm wide and about 3 cm thick (about the size of a clenched fist). Each kidney weighs about 100 grams (a small proportion of the total body mass), but they receive about 25% of the cardiac output (which per unit of tissue is about eight times higher than the blood flow to muscles undergoing heavy exercise). The renal blood supply arises from the aorta via the renal arteries and returns to the inferior vena cava via the renal veins. Each kidney is enclosed by a thick fibrous capsule and has two distinct layers: the reddish-brown cortex, which has a rich blood supply, and the inner medulla, within which the structural and functional units of the kidney, the nephrons, are found (Fig. 2.2).

Box 2.1

Functions of the kidney

• Regulation of water balance

• Regulation of pH (acid-base balance) and inorganic ion balance (sodium, potassium and calcium)

• Excretion of metabolic and nitrogenous waste products (urea from protein, uric acid from nucleic acids, creatinine from muscle creatine and haemoglobin breakdown products)

• Hormone secretion (erythropoietin, renin, 1,25-dihydroxyvitamin D3 (1,25-dihydroxycholecalciferol, also called calcitriol) and prostaglandins)

• Removal of toxic chemicals (drugs, pesticides and food additives)

• Regulation of blood pressure (renin–angiotensin system)

• Control of formation of red blood cells (via erythropoietin)

• Vitamin D activation and calcium balance

• Gluconeogenesis (formation of glucose from amino acids and other precursors)

The nephron

Each kidney has approximately a million nephrons (though the number declines with increasing age), each of which is about 3 cm long. The nephron is a tubule that is closed at one end and opens into the collecting duct at the other. The nephron has six distinct regions, each of which is adapted to a specific function (Fig. 2.3). There are two types of nephron. Most nephrons (85–90%) are cortical nephrons; these have short loops of Henle and are mainly concerned with the control of plasma volume during normal conditions. The juxtamedullary nephrons, which have longer loops of Henle extending into the renal medulla, facilitate increased water retention (and thus the production of hyperosmotic or concentrated urine) when the availability of water is restricted.

The renal corpuscle comprises the Bowman's capsule, a blind-ended tube, and the glomerulus, a coiled arrangement of capillaries around which the Bowman's capsule is invaginated. The glomerulus provides a large area of capillary vessels from which substances can leave, crossing the specialized flattened epithelial cells to enter the capsule of the nephron. There is a double capillary arrangement (see Fig. 2.3) whereby afferent arterioles supply the glomerular capillaries and efferent arterioles lead from the glomerulus to a second capillary bed supplying the rest of the nephron. Differential vasoconstriction of the afferent and efferent arterioles maintains a constant blood pressure within the glomerulus, which results in a constant rate of filtration. Urine production relies on three steps: simple filtration, selective reabsorption and secretion (Fig. 2.4).

Filtration

Filtration is a non-selective passive process that occurs through the semipermeable walls of the glomerulus and glomerular capsule. All substances with a molecular mass of less than 68 kilodaltons (kDa) are forced out of the glomerular capillaries into the Bowman's capsule. Therefore, water and small molecules such as glucose, amino acids and vitamins enter the nephron whereas blood cells, plasma proteins and other large molecules are usually retained in the blood. The content of the Bowman's capsule is referred to as the ‘glomerular filtrate’ and the rate at which this is formed is referred to as the ‘glomerular filtration rate’ (GFR). The kidneys form about 180 L of dilute filtrate each day (a GFR of about 125 mL/min). Most of it is selectively reabsorbed so the final volume of urine produced is about 1–1.5 L/day.

Box 2.2 describes an example of disrupted renal function in pregnancy that is detected by abnormal urine composition.

Box 2.2

Hypertension in pregnancy

Hypertensive disorders in pregnancy can disrupt renal function. The detectable presence of protein within the urine (proteinuria) may indicate that larger molecules than normal are being forced into the Bowman's capsule. This is caused by the increased blood pressure resulting in abnormal ultrafiltration. Women who have a degree of renal damage prior to pregnancy are less likely to be able to adapt to the pregnancy-induced physiological changes as effectively as women with normal renal function. These women tend to develop high blood pressure during early pregnancy and so do not normally demonstrate such a marked physiological reduction in blood pressure parameters, putting both the mother and fetus at risk.

Selective reabsorption

Substances from the glomerular filtrate are reabsorbed from the rest of the nephron into the surrounding capillaries. The proximal convoluted tubule (PCT in Fig. 2.6) is the widest and longest part of the whole nephron (approximately 1.4 cm long). The epithelial cells lining the nephron contain a large number of mitochondria to provide energy for facilitating active transport as most of the reabsorption of the glomerular filtrate takes place here. Some substances, such as glucose and amino acids, are completely reabsorbed and are not normally present in urine. Reabsorption of waste products is largely incomplete, so, for instance, a large proportion of urea is excreted. The reabsorption of other substances is under the regulation of several hormones. Antidiuretic hormone (ADH) controls the insertion of aquaporins, pore-forming membrane proteins, into the walls of the distal convoluted tubule (DCT in Fig. 2.6) and collecting ducts (CD in Fig. 2.6), which allows water to leave the filtrate, thus producing less urine (Fig. 2.5). The formation of concentrated urine is facilitated by the physical arrangement of the loop of Henle and its surrounding capillaries, which create and maintain the conditions for the reabsorption of water by osmosis (Fig. 2.6, Box 2.3). Calcitonin increases calcium excretion and parathyroid hormone enhances reabsorption of calcium from renal tubules. Aldosterone affects the reabsorption of sodium (Fig. 2.7). Atrial natriuretic peptide (ANP) inhibits NaCl reabsorption in the DCT and cortical collecting duct of the nephron. ANP also increases the GFR by dilating the afferent glomerular arterioles and constricting the efferent glomerular arteriole, thus increasing NaCl excretion.

Box 2.3

Hypertonic urine

The evolution of the mammalian kidney has enabled mammals to become highly adapted to terrestrial living. The kidney aids water conservation by producing urine that is able to be concentrated far more than the internal body fluid environment. The scarcer water is within the environment, the longer the nephron to conserve water.

Secretion

Some waste products may be actively transported directly into the tubules from the surrounding blood capillaries. These include hydrogen and potassium ions, creatinine, toxins and drugs. The cells of the renal tubules synthesize some substances, such as ammonia ions and peptides, which can be secreted into the filtrate.

The ureters, which are tubes about 25–30 cm long and 3 mm in diameter, transport the urine from the kidneys to the bladder. From each kidney the collecting ducts open into the renal pelvis, which leads to the ureter. The walls of the renal pelvis have smooth muscle, which has intrinsic activity (i.e. not controlled by nerves), generating peristaltic waves of contraction every 10 s. These waves of contraction propel urine along the ureters to the bladder. Each ureter is also lined with smooth muscle and transitional epithelium; the lumen has a star-shaped cross-section.

The ureters lie upon the posterior abdominal wall outside the peritoneal cavity, entering the bladder at an oblique angle, one at each side of the base of the specialized muscle area called the trigone which has its apex at the urethral opening. As urine accumulates in the bladder, the ureters are compressed, effectively forming a valve (the vesicoureteral valve), which prevents urinary reflux.

The bladder is a distensible hollow organ, also composed of smooth muscle, which acts as a reservoir for urine. It is intermittently emptied under conscious control. Stretch receptors within the muscle and trigone provide the signals that indicate that the bladder is full. The normal capacity of the bladder is approximately 700–800 mL; however, the natural desire to void urine becomes conscious when the level of urine in the bladder reaches approximately 300 mL. Inflammation in the trigone region caused by infection and or trauma often results in a frequent and urgent desire to void urine but on voiding only small amounts of urine are passed.

As the bladder lies below the uterus, its capacity is compromised by the growing uterus in early pregnancy. Later on, once the pregnant uterus has become an abdominal organ, the pressure on the bladder is relieved. Finally, at the end of pregnancy, bladder capacity is again compromised as the presenting part of the fetus engages, occupying space within the true pelvic cavity and thus restricting the space available to the bladder.

Urine is voided via the urethra. The female urethra is considerably shorter and straighter than the male urethra: only 4 cm in length compared with about 20 cm. This anatomical difference predisposes women towards an increased incidence of ascending urinary tract infections (UTIs). Thus, a colony count of more than 100000 bacterial cells per millilitre of urine is considered to be pathologically significant and is often referred to as bacteraemia. There are small mucus-secreting glands in the urethra that help to protect the epithelium from the corrosive urine. The upper internal sphincter, at the exit from the bladder, is composed of smooth muscle and is under autonomic control. The external sphincter is composed of skeletal muscle and is under voluntary control. The urethra in the man has a dual role as the route for urine and the delivery of spermatozoa, via coitus. Structural differences related to the development of the external genitalia are covered in Chapter 5. Trauma to the pelvic floor during childbirth may result in neurological damage affecting the function of the internal sphincter resulting in urgency of micturition. Urgency to void is increased by the degree of weakness in the sphincter and the amount of urine held in the bladder. Treatment options range from a variety of surgical procedures to drug treatment such as anti-cholinergic drugs (NCCWCH, 2006).

Urine

Urine has a specific gravity of 1.010–1.030 and is usually acidic. The volume and final concentration of urea and solutes depend on fluid intake. Sleep and muscular activity also inhibit urine production. The amber colour is due to urobilin, the bile pigment. Urine has a characteristic smell, which is not unpleasant when fresh. Odour or cloudiness generally indicates a bacterial infection (Box 2.4).

Box 2.4

Urinary tract infections (UTIs)

Pregnancy further increases the risk of UTIs in pregnancy and so routine culture and sensitivity test to detect bacteraemia is a common practice. Some women with bacteraemia may be asymptomatic, for example, group B haemolytic streptococcus. If group B streptococcus is present within the urine, antibiotic therapy is recommended (Royal College of Obstetricians and Gynaecologists, 2006) as this represents a high bacterial load which could put the neonate at risk of infection following birth (see Chapter 10).

Control of micturition

Micturition (urination) is a coordinated response that is due to the contraction of the muscular wall of the bladder, reflex relaxation of the internal sphincter of the urethra and voluntary relaxation of the external sphincter (Fig. 2.8). It is assisted by increased pressure in the pelvic cavity as the diaphragm is lowered and the abdominal muscles contract. Over-distension of the bladder is painful and can cause involuntary relaxation of the external sphincter resulting in urgency of micturition, incontinence and overflow. The tone of this sphincter is also affected by psychological stimuli (such as waking or getting ready to leave the house) and external stimuli (such as the sound of water or the feel of the lavatory seat). Any factor that raises the intraabdominal and intravesicular pressures (such as laughter or coughing) in excess of the urethral closing pressure can result in stress incontinence.

Accumulation of urine increases bladder wall tension, stimulating the stretch receptors of the bladder, which relay parasympathetic sensory impulses to the brain, generating awareness. However, there is conscious descending inhibition of the reflex bladder contraction and relaxation of the external sphincter. Entry of urine into the urethra irritates and stimulates stretch receptors, augmenting the sensory pathways as the bladder fills. Micturition is postponed until a socially acceptable time and place. This inhibition of the spinal reflex and contraction of the external sphincter is learned. Infants tend to develop bladder control when they are about 2 years old. Irritation of the bladder or urethra, for instance as a result of infection, can also initiate the desire to urinate regardless of the bladder capacity.

Normal physiological control of micturition requires an intact nerve supply to the urinary tract, normal muscle tone (of bladder, urethral sphincters and pelvic floor muscles), absence of any obstruction to flow, normal bladder capacity and, finally, the absence of psychological factors that may inhibit the micturition cycle (such as embarrassment and discomfort).

The female reproductive tract

The main features of the female reproductive tract distinguishing it from the male are that the female reproductive organs are internal and in the non-pregnant state are situated within the true pelvic cavity. The female reproductive tract consists of two ovaries, two uterine (fallopian) tubes, the uterus and cervix, the vagina and external genitalia. The female reproductive system undergoes considerable changes throughout life from childhood through reproductive life (see Box 2.5) to the menopause. Superimposed on these changes are the effects of the menstrual cycle (see Chapter 3). Prevention of infection in the female reproductive tract is essential; the cervix, endometrium and uterine tubes all produce natural antimicrobial secretions with production peaking about the time when implantation would occur (King et al., 2007).

Box 2.5

Changes to the genital tract at puberty

• Hair appears on mons veneris and subcutaneous fat accumulates

• Secretory glands mature and become active

• Labia majora and minora become pigmented with melanin

• Enlargement of the clitoris occurs

• Vaginal epithelium thickens and becomes responsive to oestrogen

• Vaginal pH decreases as lactobacilli metabolize glycogen from cell secretions

• Uterus grows and cervix doubles in length

The ovaries are dull-white almond-shaped bodies, approximately 4 cm long. They lie posteriorly and laterally relative to the body of the uterus and below the uterine tubes. They are anchored by the ovarian ligaments and attached to the posterior layer of the broad ligament, a fold within the peritoneum that extends from the uterus (Fig. 2.9). The blood supply to the ovary is via the ovarian artery, which runs alongside the ovarian ligament, and the ovarian branch of the uterine artery (see Fig. 2.12). This dual blood supply is important in maintaining reproductive function; if the ovary becomes twisted, for instance because it is displaced by a tumour or cystic growth, the ovarian ligament may occlude the blood supply from the ovarian artery. This torsion of the ovary can cause ischaemia of the tissues and intense pain.

The ovaries are composed of two distinct layers: the outer layer is the cortex and the inner section is referred to as the medulla. The ovary is contained within a sheath of connective tissue, the tunica albuginea. The cortex contains the developing follicles that contain the primary oocytes and is also responsible for the production of the female steroid hormones oestrogen and progesterone (see Chapters 4 and 5). The medulla is composed primarily of connective tissue and blood vessels and provides precursors to facilitate steroid production within the cortex. The ovary has two main functions: to produce fertilizable oocytes which can undergo full development and to secrete the steroid hormones which prepare the reproductive tract for fertilization and to establish and support the pregnancy.

The long-held belief that all oocytes in adults are formed in the fetal and perinatal period (prenatal ‘total endowment’) has been challenged (Bukovsky et al., 2009) as studies of oogenesis have demonstrated that follicular renewal continues through much of female reproductive life and oocyte renewal probably only totally ceases at the onset of natural menopause. This has important clinical significance particularly for the many young women rendered infertile by chemotherapy.

The uterine tubes (also known as the fallopian tubes or oviducts) are approximately 12 cm long and have walls of smooth muscle lined with ciliated epithelial and secretory cells. The uterine tubes are mobile and not fixed to the ovaries. The distal end of the uterine tube has specialized structures called fimbriae, which surround the opening into the tube. The fimbriae lie in close proximity to the ovary and, at ovulation, assist the entry of the ovum into the uterine tube by a wafting action, which facilitates movement of the interperitoneal fluid. The lining of the uterine tubes lies in many folds (called plicae) and is composed of ciliated columnar epithelial cells interspersed with goblet cells that secrete pyruvate to nourish the ovum. The cilia facilitate the movement of the ovum down the uterine tube; this is augmented by coordinated peristaltic contractions of the smooth muscle. The distal end of the uterine tube has a slightly wider area, called the ampulla, where fertilization of the ovum by the sperm usually occurs.

If both uterine tubes are completely blocked, fertilization is prevented as the sperm are unable to access the ovum. If one uterine tube is patent or only partially blocked then sperm may encounter and fertilize an ovum within the peritoneal cavity. However, if a fertilized ovum enters a partially or totally blocked uterine tube its passage to the uterus will be impeded and so the pregnancy may develop within the uterine tube or peritoneal cavity (see Case Study 2.1 and Box 2.6). Infection of the genital tract with Chlamydia trachomatis is becoming more common and can often be asymptomatic (Carey and Beagley, 2010). Undetected or multiple infections can lead to pelvic inflammatory disease which is the main cause of ectopic pregnancy and tubal infertility. Although the prime site of chlamydial infection is the columnar epithelial cells of the cervix, the infection can quickly ascend to the upper reproductive tract probably by attaching to sperm or by being transported in the flow of fluids. Infection leads to production of proinflammatory cytokines which interact with the infected woman's immune system (see Chapter 10) causing inflammation and tissue destruction. The incidence of infection is increasing because the organism is developing antibiotic resistance and the development of effective vaccines in very early stages.

Case study 2.1

Julie, during the booking appointment, informs the midwife that she had previously suffered an ectopic pregnancy with her last pregnancy, which was treated conservatively with methotrexate. What does the midwife need to do to ensure that Julie's pregnancy is progressing normally? What are the signs and symptoms of an ectopic pregnancy; and when are they most likely to become apparent?

Box 2.6

Ectopic pregnancy

An ectopic pregnancy is one that implants in the uterine tubes or, more rarely, the cervix, ovaries or abdomen. It is relatively common as it occurs in about 1% of all pregnancies and although the fatality rate is much reduced, ectopic pregnancy still remains a significant cause of maternal morbidity and mortality (Raine-Fenning and Hopkisson, 2009). It is usually confirmed by an ultrasound scan revealing an empty uterine cavity and a positive pregnancy test. Raised human chorionic gonadotrophin (hCG) levels confirm pregnancy but levels are lower in ectopic pregnancy than in uterine pregnancy. The term ‘pregnancy of unknown location’ (PUL) is used to describe a pregnancy where there is a positive pregnancy test but no intra- or extra-uterine pregnancy can be visualized on an ultrasound scan (Kirk and Bourne, 2009). In these cases, it is recommended that serial hCG measurements be made to monitor whether the PUL is failing (the hCG ratio is used to compare initial hCG levels with those 48 h later) and also that serum progesterone measurements are made to predict the likely outcome (higher levels are associated with pregnancies subsequently demonstrated to be viable).

The usual first warning sign of an ectopic pregnancy is abdominal pain at around 8 weeks' gestation which may present with symptoms mimicking gastrointestinal disease (misdiagnosis of ectopic pregnancy as gastroenteritis is associated with maternal mortality). Ectopic pregnancy should be suspected in all women of childbearing age who present with fainting or sudden unexpected collapse (Neilson, 2007); no form of contraception is 100% effective, so pregnancy should not be excluded in women who use contraception. If the uterine tube ruptures, the woman may become clinically shocked owing to excessive bleeding into the peritoneal cavity. The growing fetus can be surgically removed together with the damaged uterine tube if necessary (this is referred to as a salpingectomy). Occasionally, an abdominal pregnancy may ensue if implantation occurs on the peritoneum. The pregnancies rarely go to term; however, delivery of live infants via abdominal surgery has been documented. This phenomenon underpins scientific interest enabling men to have babies through a process of peritoneal implantation. The main causes of tubal blockage are infection (usually due to pelvic inflammatory disease), the formation of scar tissue from surgery or trauma and congenital malformation. High levels of steroid hormones can also affect cilia movement. If a tubal pregnancy is diagnosed early before trauma occurs, it can be treated by the intramuscular administration of the drug methotrexate. Methotrexate is a chemotherapeutic drug which inhibits folic acid metabolism (by inhibiting difolate reductase so DNA synthesis ceases) thus targeting rapidly dividing tissue such as the trophoblast; the embryo is eventually reabsorbed. Methotrexate has side effects on mucosal surfaces as they also have a fast rate of cell division and can cause conjunctivitis, gastrointestinal disturbances and stomatitis (inflammation of the mucous membranes in the mouth). Women may experience some degree of abdominal pain because of tubal miscarriage; it can be difficult to distinguish this from tubal rupture. Although the uterine tube is saved, the risk of another ectopic pregnancy is high. As the rate of sexually-transmitted disease is increasing and there are more assisted conceptions, the rate of ectopic pregnancy is expected to increase (Raine-Fenning and Hopkisson, 2009).

The functions of the uterus are to prepare to receive the fertilized ovum, to provide a suitable environment for growth and development of the fetus and to assist in the expulsion of the fetus, placenta and membranes at delivery. In the non-pregnant state the pear-shaped uterus is situated within the true pelvic cavity. It is described as being anteverted (tilted forwards) and anteflexed (curved forward), situated in a superior position to the urinary bladder (Fig. 2.10). A uterus in an abnormal position, such as a retroverted uterus, is not in an optimal position to expand in pregnancy and surgical intervention may be required to adjust its position to allow the pregnancy to proceed. The anatomical position of the uterus is maintained by the uterine ligaments, which are important in supporting the weight of the uterus, particularly during contractions (Fig. 2.11). Its blood supply is shown in Fig. 2.12.

The non-pregnant uterus weighs approximately 50 g with a cavity of approximately 10 mL and is composed of three layers (Fig. 2.13). The inner layer of the uterus is the endometrium. This layer is markedly different in the body of the uterus compared with the cervix. The cells of the endometrium are ciliated and the entire cell layer undergoes considerable growth changes during the menstrual cycle; the superficial decidual layers are shed in menstruation at the end of the cycle (see Chapter 4). The vascular connective tissue, or stroma, contains many glands that secrete alkaline mucus into the uterine cavity.

The middle layer is composed of smooth muscle, called the myometrium, which is arranged in three muscle layers (see Box 2.7). In the non-pregnant state, these layers are not very distinctive.

Box 2.7

The uterine muscle layers

1. Inner layer: fibres in the longitudinal plane that run from the anterior cervix, up over the fundus and back to the posterior edge of the cervix

2. Middle layer: interlaced spiral fibres concentrated in, and originating from, the fundal region of the uterus and getting less dense approaching the cervical region; the circular arrangement of the fibres is accentuated at the junctions with the uterine tubes and the cervix (internal os), thus providing closures to the expanding pregnant uterus

3. Outer layer: combination of longitudinal and circular fibres

The uterus has an outer layer of peritoneum that drapes over the uterus anteriorly to form a fold between the uterus and bladder, and over the uterine tubes to cover the myometrium. This is referred to as the perimetrium; it forms the broad ligament, thus maintaining the anatomical position of the uterus. The body of the uterus is about 5 cm in both length and width (excluding the dimensions of the cervix).

Arterial blood to the uterus is supplied by left and right uterine arteries which branch along their length giving rise to arcuate arteries which penetrate the myometrium. Branches of the arcuate arteries anastomose freely ensuring that the blood supply to the uterus is robust. Radial arteries branching from the arcuate arteries supply the tissue towards the lumen of the uterus. The radical arteries branch at the myometrial-endometrial boundary into the basal arteries that supply the myometrium and continue as spiral arteries. The spiral arteries are tightly coiled in the basal layer of the uterine lining but markedly narrow as they near the uterine lumen and divide into smaller straighter branches before terminating in capillary beds under the uterine surface and surrounding the uterine glands. The walls of the spiral and radical arteries are rich in smooth muscle and are innervated by the autonomic nervous system, so they are responsive to adrenergic stimuli, particularly the segments of the spiral arteries close to the myometrial-endometrial junction. These parts of the spiral arteries may spontaneously constrict before menstruation, and may induce menstruation (Burton et al., 2009).

The uterus is innervated by both parasympathetic nerves (arising from the second, third and fourth sacral segments) and sympathetic nerves via the presacral nerve (branching from the aortic plexus) and branches from the lumbar sympathetic chain. Both types of innervation to the uterus are via the Lee–Frankenhäuser plexus, which is situated in the lower region of the pouch of Douglas.

The cervix is the neck of the uterus at the top of the vagina. It has an important role in protecting the uterus from infection and undergoes important changes preceding labour (see Chapter 13). The isthmus, an indistinct layer of tissue that forms the lower uterine segment in pregnancy (see Chapter 13), separates the body of the uterus and the cervix. The cervix is about 2.5 cm in length and is composed of dense collagenous circular fibres. The cervix is spindle-shaped with an os (smooth muscle arrangement forming a constriction) at the top and bottom. The internal os forms the inner opening of the cervix at the junction with the body of the uterus. The external os is located at the bottom of the cervical canal where it projects into the vagina. Two different types of cell meet at this junction: the columnar cells of the cervical canal and the squamous epithelial cells of the outer cervix. Abnormal precancerous cells are most likely to arise at this junction. Cervical cancer is one of the more common cancers affecting women of reproductive age. One of the risk factors for cervical cancer is the presence of antibodies to certain strains of human papilloma virus (HPV). HPV itself is benign but it is thought to trigger changes in the cells of the cervix such as cervical dysplasia. HPV is one of the most common sexually transmitted diseases and is thought to infect the majority of sexually active women. Vaccination of girls and young women (usually aged 9–25 years) against certain types of high-risk HPV has recently been introduced in many countries to reduce the incidence of cervical cancer, some genital cancers and genital warts and also reduce the need for colposcopy-based surgical treatments (RCOG, 2007). The Pap smear (named after Georgios Papanikolaou) is a cervical swab which samples cells and allows checking for precancerous changes but many women who develop cervical cancer have never had a cervical smear. The shape of the spatula used to take cell samples during a cervical smear accommodates the curve of the external part of the cervix. About 5–7% of cervical smears identify abnormal results such as dysplasia indicating the need for increased vigilance and further examination. The lining of the cervix does not undergo cyclical changes in growth rate although glandular activity changes. The inner tissue lies in folds that appear branched, giving it the name arbor vitae. These folds allow dilatation during delivery.

The vagina is a distensible fibromuscular tube, about 8–10 cm long, situated within the true pelvic cavity, extending through the pelvic floor from the cervix to the vulva. The vagina is described as a potential tube because its walls are in contact but easily separated, but the walls of the vagina are not uniform. The distal and the proximal parts of the vagina have different embryonic origins; the distal vagina forms an integrated entity with the urethra and the clitoris (O'Connell et al., 2008). The cervix protrudes into the vagina, normally pointing to the posterior wall of the vagina because of the anteverted and anteflexed position of the uterus. The spaces between the cervix and the upper portion of the vaginal wall are referred to as the anterior, lateral and posterior fornices (singular: fornix). The vagina has three main functions: the facilitation of coitus, as a passage for the release of the menses and as the route for the baby to be born, commonly referred to as the birth canal. It also helps to support the uterus and prevent ascending infection through the release of antibacterial secretions favouring the growth of commensal bacteria.

The vagina is lined by a layer of moist epithelial cells folded into ridges (called rugae) that distend during intercourse and childbirth, thus facilitating the stretching of the vagina. There is also a lining of smooth muscle, which maintains the tone of the vagina. The opening of the vaginal canal, the introitus, is protected by the external genitalia. The introitus lies below the urethral opening, which is situated below the clitoris (see Fig. 2.14). The vagina does not have glands but is maintained in a moist state by secretions from the cervical glands and transudate of fluid from the blood vessels that lie below the vaginal lining.

The external genitalia (also known as the vulva) are those structures that can be seen (Fig. 2.14). Most of the structures are well innervated; therefore, they are very sensitive and are a source of sexual arousal responses. The external genitalia are well vascularized, which means they bleed easily if subjected to trauma but also heal rapidly.

The mons veneris (or mons pubis) is a pad of subcutaneous fat covered by skin lying over the pubic bone; it provides support to the clitoris and urethra and functions as a cushion during intercourse. At puberty it becomes covered with a triangular area of pubic hair, which is coarse and curly because of the unusually oblique hair follicles. The labia majora (singular: labium majus) are two fatty folds of tissue extending from the mons veneris in which the round ligaments terminate. The labia majora narrow where they come together between the vagina and anus. The outer surface is covered in pubic hair; the inner surface is rich in sebaceous and sweat glands. The labia majora enclose and protect the urogenital cleft. The labia minora are two smaller longitudinal fleshy folds of tissue; they are erectile and very vascular. They are pigmented, hairless and have some sweat and sebaceous glands. The labia minora enclose the clitoris anteriorly and unite posteriorly at the fourchette, which is commonly torn at the first delivery. The functions of the labia minora are probably to increase the depth of the vaginal canal during intercourse and to increase retention of the ejaculate following intercourse.

The clitoris is a highly sensitive erectile body that is about 2.5 cm long exteriorly but projects internally for up to 9 cm forming the body and root of the clitoris (O'Connell et al., 2008) before diving into two arms, the crura, which extend around to the interior of the labia majora. The external part of the clitoris, the clitoral glans, is covered and protected by a fold of skin called the clitoral hood, or prepuce which is homologous with the foreskin in males. The erectile bodies, analogous to the spongy tissue structures of the penis, become erect and engorged on stimulation. The clitoris is an important source of sexual arousal, generating reflex lubrication responses from the surrounding tissue. When the labia are held open, the vestibule (the area from the glans clitoris to the fourchette) can be seen. It contains the external orifice of the urethra and the vaginal introitus. The urinary orifice or meatus lies about 2.5 cm below the clitoris and is a characteristic vertical slit with prominent margins formed by a horseshoe shaped arrangement of the erectile tissue of the bulbs of the clitoris (O'Connell et al., 2008). It is important to clearly identify the urinary orifice in women requiring catheterization of the bladder. To each side, slightly behind the urinary meatus, are the dimple-like exits of the Skene's ducts, which produce mucus and are useful landmarks for the urinary orifice. The Skene's ducts are the source of the urethral secretions that are produced in states of sexual arousal; these secretions may have an antimicrobial function (Moalem and Reidenberg, 2009) and contain components such as ‘prostate’ specific antigen (PSA; Zaviacic and Ablin, 2000) at similar levels to those found in male seminal fluid.

The vaginal introitus is almost closed in children but in adult women is extremely elastic; it can stretch to allow the passage of the baby's head and subsequently return to a small size of about 3 cm. The vaginal introitus is partly occluded by the protective hymen, which is probably most important in preventing ascending infection before puberty when the pH of the vagina is less acidic. Once ruptured, the skin tags are referred to as hymen remnants. The appearance of an intact hymen can have important significance in some societies as it is considered to indicate virginal status. The Bartholin's glands lie posteriorly, each side of the vagina. These mucus-producing glands are the size and shape of haricot beans and, unless inflamed, cannot normally be seen. Their rate of secretion increases with the erection of the clitoris. The vestibular bulb posterior to the vagina is also formed of erectile spongy tissue.

Box 2.8 describes an example of problems caused by mutilation of the external genitalia.

Box 2.8

Female genital mutilation (FGM; ‘female circumcision’ or ‘cutting’)

Many ethnic groups, particularly those of Muslim origin in North Africa, Indonesia and other countries, regard female genital mutilation as essential to moderate sexual desire or to increase hygiene. It is important to note that pressure for women to undergo FGM may be considerable and that many women who have undergone FGM consider it normal practice and could be offended by the term ‘mutilation’. The surgery, performed in infancy, early childhood or puberty, may involve removal of the prepuce of the clitoris, removal of the labia minora and clitoris or removal of most of the labia and clitoris. The procedures may be carried out without anaesthetics and under unclean conditions such as using thorns to form stitches of the vaginal walls which increase the risks of infection, scarring and infertility. Genital mutilation may be accompanied by infibulation, the surgical closure of the labia majora (apart from a small opening for urine and menses) to ensure chastity. Although the practices are unacceptable and illegal in Western Europe, they may be undertaken illicitly or girls may be mutilated in other countries. At delivery, the urogenital tissue is extremely vulnerable to trauma, which can be minimized by anterior and mediolateral episiotomy incision. Failure to deliver vaginally may result in rejection of the woman from her family. Infibulation will require surgical division to facilitate vaginal birth and although there may be pressure from the woman and her family to have the infibulation restored, this is illegal in many countries. Following division of infibulations, the introitus is restored by the suturing of the skin edges on the same side together.

The pelvic floor is composed primarily of the muscle fibres of the levator ani and soft tissues suspended within the outlet of the pelvis, forming a sling-like sheet of tissue that encloses and supports the pelvic contents (Box 2.9). In women, the main characteristic distinguishing it from that of the pelvic floor of the man is that there are three openings instead of two. As well as the anal canal and urethra, the woman also has a vaginal opening. This is why women are much more likely to suffer from pelvic inflammatory disease (PID) as there is a direct route from the external environment via the genital tract, uterine cavity and uterine tubes to the internal pelvic cavity lined by the peritoneum.

Box 2.9

Functions and characteristics of the pelvic floor

• Its muscles are arranged in two layers: superficial and deep (see Fig. 2.15)

• It supports and maintains the anatomical position of the internal female reproductive organs

• It provides voluntary muscle control for micturition and defecation

• It facilitates birth by resisting descent of the descending presenting part, so forcing the fetus to rotate forward in the presence of strong regular uterine contractions. The human pelvic floor plays an essential role in delivery as the fetus would not otherwise be able to rotate to negotiate its passage through the pelvic girdle because of the morphology of the pelvis influenced by the evolution of our upright stance

The pelvis is a girdle composed of a number of bones held together by ligaments and cartilaginous and fused joints (Fig. 2.16). The dimensions of the inlet, cavity and outlet affect the passage of the fetus. This means that the fetus has to negotiate the pelvic cavity by undergoing a rotational manoeuvre. The sling-like arrangement of the gutter-shaped pelvic floor muscles means that the fetus is forced to rotate in a forward position. This arrangement has evolved because of humans adopting an upright stance.

The female pelvis is wider and shallower than the male pelvis. Each half of the pelvis is known as the innominate bone, which is composed of ilium, ischium and pubic. Traditionally, pelvic morphology has distinguished four major categories (Fig. 2.17). In practice, there is a wide variation in pelvic form combining features from all four of the categories. There are also recognized abnormalities of the pelvis including justominor pelvis (normal shape but overall dimensions smaller than normal), Nägele's pelvis (asymmetrical due to abnormal bone formation on one side) and Robert's pelvis (similar to Nägele's pelvis but the abnormal bone formation is bilateral). Pelvic shape can also be affected by disease, for example rachitic pelvis due to rickets, which is an extreme form of the platypelloid pelvis. The shape of the pelvis affects the mechanism of labour (see Chapter 13); abnormal pelvic shape is associated with problems at delivery as the rotation of the presenting part may be suboptimal.

The male reproductive tract

The male reproductive tract comprises a number of structures that permit gamete formation to occur below body temperature and provide conditions that allow sperm maturation and ejection (Fig. 2.18).

The testes are suspended within the scrotal sac or scrotum. Optimal spermatogenesis in humans is achieved 2–3°C below the body's core temperature. There are a number of mechanisms to regulate the temperature of the testes. The testes are suspended outside the abdominal cavity but can be retracted upwards towards the warmth of the body by contraction of the cremaster muscle which covers the testes. This muscle will also reflexly raise the testes towards the body if the inner thigh is stroked or scratched; this cremaster reflex is used as a neurological test. The pigmented skin of the scrotum lies in rugae (folds), which increase the surface area. The scrotum is well vascularized but has no insulating hair or subcutaneous fat. It is lined by dartos muscle, which contracts in response to cold. Blood flow to the testes allows heat to be transferred from the descending testicular arteries to the ascending pampiniform venous plexus forming a countercurrent heat-exchange mechanism, which helps to maintain the lower temperature of the testes relative to the body.

The testes are a pair of glandular organs, analogous to the ovaries, that produce gametes (spermatozoa) and male sex hormones. Within the scrotum, the testes are surrounded by a thick fibrous capsule called the tunica albuginea, which penetrates internally dividing the testes into lobules. Each testis has about 200 lobules, each containing about three seminiferous tubules, about 0.2 mm in diameter and up to 70 cm long (Fig. 2.19). The seminiferous tubules are the site of spermatogenesis (sperm production). Within the tubules are spermatogenic cells (germ cells) and their supporting Sertoli cells which cordon off the spermatogenic cells and the developing sperm into distinct compartments. Between the tubules are the interstitial cells of Leydig, which produce testosterone.

The sperm produced from the seminiferous tubules are stored in the epididymis where they are concentrated, becoming mature and motile. The epididymis is a comma-shaped convoluted tube, about 6 cm long, leading into the vas deferens. The vas deferens provides the conduit for sperm delivery during emission and ejaculation. It is a thick-walled tube leading from the tail of the epididymis to the ejaculatory duct. The vas deferens dilates into a storage reservoir, or ampulla, just before it joins with the exit of the seminal vesicle to form the ejaculatory duct. Just as infection or trauma can cause blockage of the uterine tubes, the male reproductive capacity can be also affected by blockage, of the epididymis or vas deferens for instance, impeding the passage of spermatozoa. The vas deferens, blood vessels and cremaster muscle lie closely together forming the spermatic cord.

The seminal vesicles are two pyramid-shaped membranous sacs, about 4 cm long, lying between the base of the bladder and the rectum. They produce semen, a fructose-rich viscous fluid, which facilitates sperm transport and nourishment. The fluid component of semen is principally produced by the seminal vesicles and prostate gland. Secretory activity of the seminal vesicles depends on the level of testosterone. The ejaculatory ducts begin at the base of the prostate gland and terminate in the single prostatic urethra. These muscular ducts carry sperm and seminal fluid through the prostate gland. The prostate gland is a walnut-sized exocrine gland lying just below the neck of the bladder, between the rectum and pubic bone. It is a compound gland, formed of about 20–40 smaller glandular units each with its own exit into the ejaculatory duct. Prostatic fluid is a thin lubricating secretion that mixes with the sperm and seminal fluid. The prostatic gland can be palpated through the rectal wall. In elderly men, the prostate gland may undergo hypertrophy causing benign prostatic hyperplasia which can compress the urethra and impede micturition. Prostatitis or inflammation of the prostate gland can affect men of all ages. Prostatic carcinoma is one of the most common cancers affecting elderly men in developed countries; it is a major cause of death if it is not detected early. Prior to ejaculation, the bulbourethral glands (or Cowper's glands) secrete clear lubricating fluid into the urethra just below the prostate gland.

The penis carries the urethra, which provides a shared passage for sperm and urine, and allows intromission: the delivery of sperm into the vagina. Unlike other mammalian species, the human penis does not have an erectile bone and relies entirely on engorgement to achieve erection; it also cannot be withdrawn into the groin. Humans have one of the largest penis:body size ratios. The penis has three columns of erectile tissue: two lateral corpora cavernosa and a ventromedial corpus spongiosum (Fig. 2.20). The corpus spongiosum contains the urethra and does not engorge as much as the corpora cavernosa. This prevents trauma to the urethra and generates an appropriate angle for intromission. The expanded cone-shaped end of the corpus spongiosum forms the glans penis where the urethra opens. The penis is covered with a fold of skin or prepuce (foreskin), which can be retracted in an adult and older child to expose the glans. The foreskin attaches to the underside of the penis at a small fold of tissue called the frenum. The prepuce and shaft skin are not attached to underlying tissue so they are free to glide along the shaft of the penis, which reduces friction, abrasion and loss of lubricating fluid during intercourse. On the underside of the penis, there is a small ridge called the raphe which runs from the opening of the urethra across the scrotum to the perineum (between the scrotum and anus). The spongy bodies of the penis become distended with blood during an erection (see Chapter 6).

Gametogenesis

The process of gametogenesis is achieved through a specialized form of cellular division called meiosis (Fig. 2.21). The stages of meiosis are reviewed in Chapter 7. Gametogenesis is remarkably different in the male and female reproductive systems, both representing adaptation of the process of meiosis to facilitate reproduction. Gametes are specialized sex cells that contain half the genetic material (and, therefore, half the number of chromosomes) of the normal cell content. Their fusion, referred to as fertilization, is described in detail in Chapter 6.

The production of spermatozoa begins at puberty in the male and results in the continual production of millions of sperm. Spermatozoa have completed all the meiotic divisions prior to ejaculation and fusion with the oocyte. In this sense, they are true gametes containing the haploid number of chromosomes. (These terms are explained in Chapter 4.)

The differences between male and female gamete formation have evolved with the development of sexual reproduction and internal fertilization. Oocytes are relatively protected within the abdominal cavity and so it is not necessary for a large number to be produced. Movement of oocytes is passive, influenced by the structure of the uterine tube. Sperm, in contrast, must become highly motile in order to travel along the female reproductive tract. Many are lost and, of the millions contained within the ejaculate, only a few hundred will make it to the vicinity of the oocyte. In addition, sperm have to survive transplantation into the female reproductive tract which is effectively equivalent to a foreign host in order to perform their physiological role of fertilizing the oocyte. Thus, they have to be adapted to evade the innate immune defence mechanisms which protect the female reproductive tract such as the complement (see Chapter 10) which is present in the secretions; both sperm and seminal fluid have complement regulators which enhance sperm survival (Harris et al., 2006).

Spermatogenesis begins at puberty and continues into senescence, albeit less efficiently. It is a complex process, well-organized temporally and spatially, which takes place in the epithelium of the seminiferous tubules; groups of cells progress in clearly defined stages of cell division within a particular tubule, which is described as a ‘spermatogenic wave’. There are three processes involved in spermatogenesis: (1) the renewal of the stem cells and the formation and expansion of undifferentiated progenitor germ cells (spermatogonia) around the inner circumference of the seminiferous tubule, which divide and replicate by a process called mitosis (see Chapter 4), forming many spermatogonia (Fig. 2.22); (2) the reduction of the number of chromosomes in each progenitor cell by meiosis; and (3) the differentiation of the haploid cells into spermatozoa (spermiogenesis). Each spermatogonium first divides into two diploid primary spermatocytes. The primary spermatocytes then undergo meiosis producing two genetically diverse secondary spermatocytes and then, after the second meiotic division, four haploid spermatids. For each cell undergoing meiosis, therefore, four gametes are produced. The round spermatids undergo spermiogenesis (nuclear and cytoplasmic changes) producing the characteristic morphology (shape) of a spermatozoon. As meiosis progresses, the immature sperm are supported within Sertoli cells (Griswold, 1998), which then release the sperm into the lumen of the seminiferous tubule by degrading the cell-cell junctions (Hogarth and Griswold, 2010). Sertoli synthesize and secrete a number of glycoproteins involved in Sertoli-germ cell interactions including bioprotective proteins, proteases and protease inhibitors involved in tissue remodelling processes, glycoproteins that form the basement membrane and other regulatory glycoproteins (Box 2.10).

Box 2.10

The role of Sertoli cells

• Support (‘nurse’) spermatogenic cells and move them inwards

• Provide nutrients to spermatocytes and spermatids (hence their former name of ‘nurse cells’)

• Secrete fluid to aid release of sperm into lumen

• Act as a barrier between sperm-producing areas and lumen, forming environmentally distinct compartments of the seminiferous epithelium

• Engulf and digest cellular debris left from spermiogenesis

• Produce inhibin and activins, which regulate follicle-stimulating hormone (FSH) secretion

• Produce androgen-binding protein (ABP, also known as testosterone binding globulin), which increases seminiferous tubule testosterone concentration and thereby spermiogenesis

• Produce aromatase which converts testosterone to oestradiol, a step essential in the induction of spermatogenesis (note that this enzyme is also produced by adipose tissue which is one of the reasons why obesity in men is associated with altered sex hormone profiles)

• Produce anti Müllerian-inhibiting hormone, which affects sexual differentiation (see Chapter 5)

• Produce glial cell line-derived neurotrophic factor (GNDF), a small protein which regulates kidney development and spermatogenesis

• Produce Ets-related molecule (ERM), a member of the Ets transcription factor family essential for spermatogonium stem cell maintenance and self-renewal

• Synthesis and secrete several proteins found in serum including the iron and copper binding proteins, transferrin and ceruloplasmin, which seem to be involved spermatogenesis (Gupta, 2005)

The spermatozoa are stored in the epididymis, where they mature acquiring both motility and the capability for fertilization, for 2 weeks and may stay for up to 6 months. The shortest time between the initial meiosis and ejaculation is about 10 weeks, which is therefore the critical preconception period in men. Spermatogenesis is regulated by gonaodotrophins and steroid hormones, the interaction of these hormones with the somatic cells of the testis (Leydig and Sertoli cells) and by vitamin A (Hogarth and Griswold, 2010). It is affected by temperature, malnutrition, alcohol, cottonseed oil (a potential source of contraception), some drugs and heavy metals.

The interstitial cells of Leydig interspersed between the seminiferous tubules produce 90% of the circulating testosterone (the remainder has an adrenal origin). Testosterone is responsible for male secondary sex characteristics (see Chapter 3) and, together with follicle-stimulating hormone (FSH), controls production of sperm. Testosterone production is stimulated by luteinizing hormone (LH) from the pituitary gland (Fig. 2.23). Testosterone binds to androgen-binding protein (ABP) in the seminiferous tubules, which means that testosterone levels within the tubule can be very high while maintaining a concentration gradient that drives diffusion from outside to inside. Testosterone exerts a negative feedback mechanism on the hypothalamic–pituitary axis in a manner analogous to the feedback control by oestrogen in the female cycle (see Chapter 4). FSH stimulates the production of ABP by the Sertoli cells. Inhibin produced from the Sertoli cells inhibits FSH production. Illness and stress affect male reproductive capacity probably via the hypothalamic–pituitary axis.

The controls of gametogenesis and steroidogenesis in the man and woman have some similarities. The hypothalamus regulates reproduction by secreting gonadotrophin-releasing hormone (GnRH; see Fig. 2.23). This stimulates both FSH and LH production from the anterior pituitary gland. FSH stimulates gametogenesis: spermatogenesis in men and follicular development in women. Luteinizing hormone plays a pivotal role in steroidogenesis: increasing testosterone production from the Leydig cells in men and stimulating the increases in progesterone and oestrogen secretion in the second half of the menstrual cycle in women (see Chapter 4).

Key points

• The renal system regulates water and electrolyte balance and is important in the maintenance of pH and the regulation of blood pressure. Waste products and foreign chemicals are excreted by the kidneys. The kidneys also have an endocrine role such as the regulation of the number of circulating erythrocytes.

• Glomerular filtrate is formed from continuous processing of plasma and contains water and substances such as amino acids and glucose that are small enough to be filtered.

• The filtrate is modified in the nephron by reabsorption of substances into the blood and secretion of waste products into the filtrate. Reabsorption and secretion are regulated by hormones and many systems have transport maxima that can be exceeded in pregnancy, leading to urinary excretion of substances not usually present in the urine.

• Micturition (urination) is stimulated by bladder stretch receptors and controlled by learned inhibitory pathways.

• The female reproductive system produces female gametes, receives male gametes, and provides the optimum environment for fertilization, implantation and nurture of the fetus. It remains quiescent in pregnancy and generates the forces required for delivery at the end of gestation. The system is quickly restored to a fertile state at the end of pregnancy.

• Gametogenesis begins with mitosis of the primordial germ cells followed by meiosis, which reduces the chromosome number and creates infinite variation in the genetic complement of the gametes.

• The male gonads produce gametes from the seminiferous tubules and testosterone from the Leydig cells. Gametogenesis has a relatively short time-span in the man.

• The hypothalamus regulates reproduction by secreting gonadotrophin-releasing hormone (GnRH), which stimulates production of FSH and LH from the anterior pituitary, which in turn have effects on the gonads. The sex steroids produced by the gonads exert negative feedback inhibition at the hypothalamic–pituitary axis.

Application to practice

Why is an in-depth knowledge of the female genitalia required by the midwife and how will this knowledge affect the decisions made by the midwife within practice?

You might consider what the midwife needs to know in order to suture the peritoneum, to catheterize a woman during labour or to recognize the sex of a baby at birth (see Chapter 5). There are many signs and ‘symptoms’ in pregnancy that are indicative of changes occurring within the renal system; knowledge of this will help the midwife to explain these fully to the woman.

During routine antenatal check-ups, the midwife routinely performs urinalysis. Are you able to explain the significance of the findings as a whole or do you think it is appropriate that midwives just observe for evidence of proteinuria?

The hormones of pregnancy affect muscle tone and relax ligaments, so bladder control is often less effective in pregnancy and these effects may continue after pregnancy. In such cases, muscle tone can be improved by encouraging pelvic floor exercises to promote optimal continence following childbirth. Displacement of the pelvic organs resulting in anterior and posterior prolapses becomes increasingly common as the parity due to the loss of effective muscle tone and ligament support is higher, and so pelvic floor exercises should be encouraged to minimize these problems.

Application to practice

Women with pre-existing renal disease need careful monitoring and maternity care should include expert renal care. For some women, underlying renal disease may only become apparent in pregnancy when a woman fails to have the normal expected physiological fall in blood pressure in the first trimester and subsequently develops hypertension during the pregnancy. The earlier the hypertension develops, the higher is the risk for long-term problems for the mother. The fetus is also at increased risk of severe intrauterine growth retardation.

Women who have had a kidney transplant may become pregnant; however, the risk to the pregnancy must be carefully managed against the risk of reducing or modifying anti-rejection medication. It is important to consider that the anatomical placement of the donor kidney is usually much lower in the abdominal cavity. This is particularly important should the woman require surgical intervention for delivery to ensure that the donor kidney is not damaged during the procedure.

Annotated further reading

Braddy, C.M.; Files, J.A., Female genital mutilation: cultural awareness and clinical considerations, J Midwifery Womens Health 52 (2007) 158–163.

A review, written for health professionals, which describes the cultural background surrounding the practice of FGM, the different types of procedures used and the complications.

Johnson, M.H., Essential reproduction. ed 6 (2007) Blackwell Science, Oxford .

An integrated and well-organized research-based textbook that explores comparative reproductive physiology of mammals, including anatomy, physiology, endocrinology, genetics and behavioural studies.

Leeson, S., Abnormal cervical smears: a practical guide, Obstet Gyn Reproduc Med 18 (2008) 163–167.

A clear description of the colposcopy (the diagnostic procedures for detecting abnormalities of the cervix and vagina) illustrated with case studies, together with consideration of the issues associated with the examination, treatment and quality control.

O'Connell, H.E.; Eizenberg, N.; Rahman, M.; et al., The anatomy of the distal vagina: towards unity, J Sex Med 5 (2008) 1883–1891.

A comprehensive, objective and unambiguous factual presentation of female sexual anatomy which is clearly-presented and well-illustrated.

Raynor, M.D.; Morgan, M., Female genital mutilation: unveiled and deconstructed, 2000 In: (Editor: Fraser, D.) Professional studies for midwifery practice (2000) Churchill Livingstone, Edinburgh.

This chapter gives an excellent overview of female genital mutilation, the different classifications and prevalence and explores racial, ethnic and cultural aspects of this phenomenon. Guidance is provided for the midwifery care of women who have undergone mutilation and the health problems related to these practices.

Royal College of Obstetrics and Gynaecology (RCOG), The management of tubal pregnancies (clinical guideline 21). (2004) RCOG, London .

This guideline provides a detailed account of methotrexate in the non-surgical management of ectopic pregnancy.

Stoker, J., Anorectal and pelvic floor anatomy, Best Pract Res Clin Gastroenterol 23 (2009) 463–475.

This well-illustrated review provides detailed descriptions of the layers of the pelvic floor based on magnetic resonance imaging (MRI).

Thomas, R.; Stanley, B.; Horton-Szar, D., Crash course: renal and urinary systems. ed 3 (2007) Mosby, St Louis .

This well-illustrated book provides a useful reference text for students requiring more details of the renal and urinary systems.

Tilly, J.L.; Telfer, E.E., Purification of germline stem cells from adult mammalian ovaries: a step closer towards control of the female biological clock? Mol Hum Reprod 15 (2009) 393–398.

An interesting commentary about the evidence suggesting mammals retain the capacity to generate oocytes throughout adulthood.

Readers are recommended also to read chapters on the renal and reproductive systems in a physiology textbook, such as those listed at the end of the previous chapter.

References

Bennett, V.R.; Brown, L.K., In: Myles' textbook for midwives ed 13 (1999) Churchill Livingstone, Edinburgh, p. 940; 941, 942, 949.

Bogin, B., Patterns of human growth. ed 2 (1999) Cambridge University Press, Cambridge .

Brooker, C.G., In: Human structure and function ed 2 (1998) Mosby, St Louis, p. 344; 345, 363, 470, 471, 473, 476, 483.

Bukovsky, A.; Caudle, M.R.; Virant-Klun, I.; et al., Immune physiology and oogenesis in fetal and adult humans, ovarian infertility, and totipotency of adult ovarian stem cells, Birth Defects Res C Embryo Today 87 (2009) 64–89.

Burton, G.J.; Woods, A.W.; Jauniaux, E.; Kingdom, J.C., Rheological and physiological consequences of conversion of the maternal spiral arteries for uteroplacental blood flow during human pregnancy, Placenta 30 (2009) 473–482.

Carey, A.J.; Beagley, K.W., Chlamydia trachomatis, a hidden epidemic: effects on female reproduction and options for treatment, Am J Reprod Immunol 63 (2010) 576–586.

Griswold, M.D., The central role of Sertoli cells in spermatogenesis, Semin Cell Dev Biol 9 (1998) 411–416.

Gupta, G.S., Proteomics of Spermatogenesis. (2005) Springer, New York .

Harris, C.L.; Mizuno, M.; Morgan, B.P., Complement and complement regulators in the male reproductive system, Mol Immunol 43 (2006) 57–67.

Hogarth, C.A.; Griswold, M.D., The key role of vitamin A in spermatogenesis, J Clin Invest 120 (2010) 956–962.

Khandelwal, P.; Abraham, S.N.; Apodaca, G., Cell biology and physiology of the uroepithelium, Am J Physiol Renal Physiol 297 (2009) F1477–F1501.

King, A.E.; Kelly, R.W.; Sallenave, J.M.; et al., Innate immune defences in the human uterus during pregnancy, Placenta 28 (2007) 1099–1106.

Kirk, E.; Bourne, T., Pregnancy of unknown location, Obstet Gyn Reproduc Med 19 (2009) 80–83.

Moalem, S.; Reidenberg, J.S., Does female ejaculation serve an antimicrobial purpose? Med Hypotheses 73 (2009) 1069–1071.

NCCWCH, Urine incontinence: the management of urinary incontinence in women. (2006) National Institute for Health and Clinical Excellence, London .

Neilson, J., Early pregnancy deaths, In: (Editor: Lewis, G.) Saving mother's lives: reviewing maternal deaths to make motherhood safer 2003–2005. The seventh report of Confidential Enquiries into Maternal Deaths in the United Kingdom, London (2000); Available from: www.cemach.org.

Royal College of Obstetricians and Gynaecologists, Prevention of group B streptococcus (GBS) infection in newborn babies. (2006) RCOG, London ; (amended 2007).

O'Connell, H.E.; Eizenberg, N.; Rahman, M.; et al., The anatomy of the distal vagina: towards unity, J Sex Med 5 (2008) 1883–1891.

Raine-Fenning, N.; Hopkisson, J., Management of ectopic pregnancy: a clinical approach, Obstet Gyn Reproduct Med 19 (2009) 19–25.

RCOG Royal College of Obstetricians and Gynaecologists (Scientific Advisory Committee), The Changing Role of the Gynaecologist in the Management of Women with Cancer (Opinion Paper 10). (2007) .

Sweet, B., In: Mayes' midwifery ed 12 (1996) Baillière Tindall, London, p. 29.

Zaviacic, M.; Ablin, R.J., The female prostate and prostate-specific antigen. Immunohistochemical localization, implications of this prostate marker in women and reasons for using the term “prostate” in the human female, Histol Histopathol 15 (2000) 131–142.