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1 Urogenital System Kidney Systems Three slightly overlapping kidney systems are formed in a cranial to caudal sequence: the pronephros, mesonephros, and metanephros. Pronephros The pronephros is the type of kidney found only in the lowest of vertebrates. In humans the first evidence of a urinary system consists of the pronephros, a few segmentally arranged set of epithelial cords that differentiate from the anterior intermediate mesoderm at about 22 days gestation. These sets cords in the cervical region are called nephrotomes: a set on each side of the embryo. The nephrotomes connect laterally with a pair of primary nephric (pronephric) ducts which grow toward the cloaca. As the primary nephric ducts extend caudally, they stimulate the intermediate mesoderm to form additional segmental sets of tubules: mesonephric tubules. Mesonephros From the upper thoracic to the upper lumbar region the mesonephros appears, while the cervical pronephric system regresses. A typical mesonephric unit consists of a vascular glomerulus surrounded by an epithelial glomerular capsule. Each mesonephric tubule empties separately into the continuation of the primary nephric duct (from the pronephros), which becomes the mesonephric (wolffian) duct. The formation of mesonephric tubules occurs in a cranial to caudal direction. By the end of the fourth week the mesonephric ducts attach to the cloaca. Very near its attachment to the cloaca, the mesonephric duct develops an epithelial outgrowth called the ureteric bud. Early in the fifth week the ureteric bud begins to grow into the most posterior region the intermediate mesoderm. It then sets up a series of continuous inductive interactions leading to the formation of the definitive kidney, the metanephros. Urine formation in the mesonephros begins with a filtrate of blood from the glomerulus into the glomerular capsule. This filtrate then flows into the tubular portion of the mesonephros where there is selective resorption of ions and other substances. The mesonephros does not develop into a sophisticated system for concentrating urine as in the adult kidney. Its principal functions are to remove waste and there is no need to conserve water. Although most of the mesonephric tubules rapidly degenerate after the metanephric kidneys become functional, the mesonephric ducts persist in the male. The ducts and a few caudal tubules become incorporated as integral parts of the male genital system. In the female, they all disappear. Medial to the mesonephros a gonad is developing. The gonad and the mesonephros form an elevation on both sides of the embryo called the urogenital ridge. Metanephros Development of the metanephros begins in the fifth week when the ureteric bud (metanephric diverticulum) expands into the posterior portion of the intermediate mesoderm. Mesenchymal cells of the intermediate mesoderm condense around the metanephric diverticulum to form the metanephric blastema. 2 The morphological basis for the development of the metanephric kidney is (1) the elongation and branching (up to 15 times) of the ureteric bud, which becomes the collecting (metanephric) duct system of the metanephros, and (2) the formation of renal (excretory) tubules from mesenchymal condensations of the metanephric blastema at the tips of the branching collecting system. The formation of individual tubules (nephrons) in the developing metanephros involves three mesodermal cell types: (1) epithelial cells of the ureteric bud, (2) mesenchymal cells of the metanephric (metanephrogenic) blastema, and (3) ingrowing vascular cells. The earliest stage is the condensation of mesenchymal blastemal cells (metanephric tissue cap) around the terminal parts (collecting tubules) of the ureteric bud. Influenced by the collecting tubule, cells of the tissue cap form small vesicles, the renal vesicles, which give rise to small S – shaped tubules. Capillaries will grow into the pocket of one end of the S [like in the lower pocket here for example > S] and differentiate into glomeruli. The renal tubules, together with their glomeruli, form nephrons (the excretory units). The proximal end of each nephron (the pocket) forms Bowman's capsule and the distal end forms an open connection with the collecting tubule, which was derived from the ureteric bud. During differentiation of the nephron, a portion of the renal tubule develops and elongated hairpin loop that extends into the medulla of the kidney as the loop of Henle. There are about 15 successive generations of nephrons in the peripheral (cortical) zone of the kidney. While many sets of nephrons are differentiating, the kidney becomes progressively larger. The branched system of ducts also becomes much larger and more complex forming the pelvis and the calyces. Hence, the kidney develops from two sources of intermediate mesoderm. (1) The ureteric bud (off the mesonephric duct) forms the renal pelvis, major and minor calyces, and 1 million to 3 million collecting tubules. (2) the metanephric blastema provides for the excretory units that include Bowman's capsule [parietal and visceral (podocytes) epithelium] plus the proximal and distal convoluting tubules. Mesangial cells are derived from the mononuclear phagocyte system that differentiated from hematopoietic cells (mesoderm). The basement membrane is derived from secretions of both podocytes and adjacent endothelial cells of the glomeruli. Urine production begins by the 10th week with about 1 million functional nephrons in each kidney. Positioning of the Kidney Initially, the metanephric kidneys are located deep in the pelvic region. During the late embryonic and early fetal period, they undergo a shift in position that moves them into the abdominal cavity. There are two components to their migration. One is caudocranial shift from the 4th lumbar to the 1st lumbar vertebrae. The other is a lateral displacement. Both changes of positions bring the kidneys in contact with the adrenal glands. During their migration, the kidneys also undergo a 90-degree rotation, with the pelvis ultimately facing the midline. As they are migrating out of the pelvic cavity, the kidneys slide over the large umbilical arteries. These changes occur behind the peritoneum, thus the 3 kidneys are retroperitoneal. During the migration, the mesonephric kidneys regress. The mesonephric ducts are retained for the developing gonads. Formation of the Urinary Bladder The cloaca is divided into a urogenital sinus and rectum is by means of the urorectal septum. The urogenital sinus is continuous with the allantois, which has a tubular process extending into the body stalk or umbilical cord. The dilated upper part of the urogenital sinus forms the urinary bladder and superior to it, the distal end of the allantois solidifies as the cordlike urachus. The urachus forms the median umbilical ligament. The next lower part of the urogenital sinus (below the bladder) is narrow and forms the pelvic part of the urogenital sinus. Here, the prostatic and membranous parts of the urethra are formed in the male. In the female there is a membranous part of the urethra. As the bladder grows, it incorporates the mesonephric ducts and ureteric buds. The result is that these structures open separately into the posterior wall of the bladder. The mesonephric ducts enter into the prostatic urethra close together as the ejaculatory ducts. The region bounded by the ureters and the ejaculatory ducts is the trigone of the bladder. Problems In Renal Formation Anomalies of the urinary system are relatively common (3% - 4% of live births). Renal Agenesis Renal agenesis is the unilateral or bilateral absence of any trace of kidney tissue. Unilateral agenesis is seen in about 0.1% of adults. Bilateral agenesis occurs in roughly 1/3500 newborns. The ureter may be present. Individuals with unilateral renal agenesis are often asymptomatic and the single kidney undergoes compensatory hypertrophy. An infant born with bilateral renal agenesis dies in a few days. Because of a lack of urine output, reduction in the volume of amniotic fluid (oligohydramnios) during pregnancy is often an associated feature. Infants born with bilateral renal agenesis characteristically exhibit Potter facies, consisting of a flattened nose, receding chin, wide interpupillary space, and large, low set ears. This problem is due to mechanical pressure of the uterus on the fetus. Renal Hypoplasia This is an intermediate renal agenesis and a normal kidney, where one kidney or both are substantially smaller than normal. A certain degree of normal function is maintained. If one kidney is affected, the other will undergo compensatory hypertrophy. Renal Duplications Renal duplications range from a simple duplication of the renal pelvis to a completely separate supernumerary kidney. Anomalies of Renal Migration and Rotation 4 The most common disturbance of renal migration is its failure to depart from the pelvis. This is usually associated with malrotation of the kidney as well, so the hilus of the pelvic kidney faces anteriorly instead of toward the midline. Another category of defective migration is crossed ectopia, where one kidney and its associated ureter are on the same side of the body as the other kidney. The horseshoe kidney occurs in as many a 1 / 400 individuals, where the kidneys are fused at their inferior poles. Horseshoe kidneys cannot migrate out of the pelvic cavity because the inferior mesenteric artery blocks them. In most cases, the horseshoe kidney is asymptomatic, but occasionally pain or obstruction of the ureters may occur. Anomalies of the Renal Arteries Duplication of the renal arteries is common. Polycystic Disease of the Kidney Congenital polycystic disease of the kidney, an autosomal recessive condition of infants, is manifest by a large number of cysts in the kidney. Here, the pathogenesis has not been ascertained. In adults, an autosomal dominant form of the disease results from mutations in two genes encoding the transcription factors, ADPKD-1 and ADPKD-2 (autosomal dominant polycystic kidney disease), which produce the proteins polycystin -1 and polycystin 2. Cysts occur in other organs, especially the liver and pancreas. Cysts, Sinuses, and Fistulas of the Urachus If parts of the lumen of the allantois fail to obliterate, urachal cysts, sinuses, or fistulas can form. In the urachal cyst, urine seeps from the umbilicus. Exstrophy of the Bladder Exstrophy of the bladder is a major defect where the urinary bladder opens broadly onto the abdominal wall. Rather than being a primary defect of the urinary system, it is commonly attributed to an insufficiency of tissue in the ventral abdominal wall. In males, exstrophy of the bladder commonly involves the phallus and a condition called epispadius. --------------------------------------------------------------------------------------------------------------Genital System and Gonads Sexual determination begins at fertilization, when a Y chromosome or an additional X chromosome is joined to the X chromosome already in the egg. Although genetic gender is determined at fertilization, the gross phenotypic gender is not manifested until the 7th week of development. During this morphologically indifferent stage of sexual development, the gametes migrate into the gonadal promordia from the yolk sac. The female phenotype is the baseline, or default condition, that must be acted on by male influences to produce a male phenotype. Genetic Determination of Gender 5 The testes determining gene is at the SRY (sex-determining region on Y) gene. The SRY gene on the Y chromosome is located on its short arm. The SRY protein made by the gene determines if there will be male or female development. Migration of Germ Cells into the Gonads Experimental studies have shown that primordial germ cells can be demonstrated in the epiblast of the mouse. These cells pass through the early primitive streak and are located as a small cluster of cells in the extraembryonic mesoderm near the base of the allantois. They become associated with the endoderm of the posterior wall of the yolk sac. During the 3rd week, human primordial germ cells can be observed in the yolk sac. In the embryo, primordial germ cells migrate from the posterior wall of the yolk sac along the wall of the hindgut and through the dorsal mesentery until they reach the region of the genital ridges. As the germ cells approach the genital ridges late in the 5th week, they may be influenced by chemotactic factors secreted by the newly forming gonads. About 1000 to 2000 primordial germ cells enter the genital ridges. Once the primordial germ cells have penetrated the genital ridges, their migration ceases. Some germ cells inappropriately migrate to extragonadal sites and they degenerate. In rare instances they may persist, such as in the mediastinum and give rise to teratomas (a tumor containing the three primary embryonic germ layers). Origin of the Gonads The gonads arise from an elongated region of mesoderm along the ventromedial border of the mesonephros. Cells in the cranial part of this region condense to form the adrenocortical primordia, and those in the caudal part become the genital ridges. The genital ridges are identifiable midway through the 5th week. The early genital ridges are composed of two cell populations: (1) cells from coelomic epithelium and (2) cells arising from the mesonephric ridge. Differentiation of the Testes When the genital ridges first appear, those of males and females are indistinguishable or indifferent gonads. The principle foundation for gonadal differentiation is the influence of the SRY gene and its elaboration of testes-determining factor on the gonads to have them develop into testes. In its absence, the gonads differentiate into ovaries. Neither the expression of SRY nor later differentiation of testes depends on the presence of primordial germ cells. The sex-determining genes act on the somatic portion of the testes and not the germ cells. Testis develop more rapidly than the ovary. Precursors of supporting or Sertoli cells (sustentacular cells) must be prepared to receive genetic signals for testicular differentiation by a certain time. If not, the primordial germ cells begin to undergo meiosis and the gonad differentiates into an ovary. Supporting cells are derived from surface epithelium of the gonad as are the follicular cells of the ovary. Evidence shows that the genital ridges first appear midway in the 5th week through the proliferation of coelomic epithelial cells along the medial border of the mesonephros. Later in the 5th week the primordial germ cells enter the early genital ridge and the coelomic epithelium sends short epithelial pillars toward the interior or medullary portion 6 of the gonad. Early in the 6th week a set of primitive sex cords takes shape in the genital ridge, and the primordial germ cells migrate into the primitive sex cords. Late in the 6th week the testes shows evidence of differentiation. The primitive sex cords (derived from surface epithelium) enlarge, get better defined, forming the Sertoli cells. As the sex cords differentiate, they are separated from the surface of the surface epithelium (germinal epithelium) by a dense layer of tissue called the tunica albuginea. The deepest portions of the testicular sex cords are in contact with the fifth to twelfth sets of mesonephric nephrons. The outer portions of the testicular sex cords form the seminiferous tubules, and the inner portions become the mesh-like rete testis. The rete testis ultimately joins the efferent ductules, which are derived from the mesonephric tubules. Leydig cells do not appear until the 8th week and soon begin to synthesize androgenic hormones (testosterone and androstenedione) and have receptors for luteinizing hormone (LH) produced by the pituitary gland. The interstitial cells of Leydig are derived from the original mesenchyme of the gonadal ridge. Fetal Leydig cells secrete their hormones during the ninth to fourteenth weeks while the genital ducts differentiate. Soon after, they involute and do not reappear until puberty as an adult isoform. By 8 weeks the embryonic Sertoli cells produce müllerian inhibiting substance, which causes involution of the precursors of the female genital duct system, the müllerian or paramesonephric ducts. Sertoli cells have receptors for follicle stimulating hormone (FSH), from the pituitary gland to make androgen-binding protein. During the late embryonic and fetal periods and after birth, the primordial germ cells divide slowly by mitosis. Differentiation of the Ovaries In contrast to the testes, the presence of viable germ cells is essential for ovarian differentiation. If primordial germ cells fail to reach the genital ridges or if they are abnormal (e.g., XO) or degenerate, the gonad regresses and streak ovaries (vestigial ovaries) result. After the primordial germ cells have entered the genital ridges, they remain in the outer cortical or near the corticomedullary region of the future ovary. Ovarian sex cords in the medullary part of the ovary do not develop as well as those in the testes. The origin of the follicular epithelial cells that surround the primordial germ cells appears to come from coelomic epithelium. In the case of the ovary, coelomic epithelium continues to proliferate and produces secondary sex cords that in contrast to the testes, remains in the cortex of the gonad. These cells then surround the primordial germ cells (now called oogonia). The oogonia proliferate by mitosis from the time they enter the gonad until the start of the 4th month. At that time, some of the oogonia enter prophase of the 1st meiotic division. The meiotic oogonia are now called primary oocytes and with their surrounding follicular cells they form primordial follicles. The oocytes continue in meiosis until they reach the diplotene stage of prophase I. Meiosis is arrested at this stage and the oocytes remain at this point until the block is removed. In the adult, meiosis continues just before ovulation. In the fetal ovary an inconspicuous tunica albuginea forms at the corticomedullary junction, with the gametes external to it. The cortex of the ovary is the dominant 7 component and contains the majority of oocytes. The medulla is filled with connective tissue and blood vessels derived from the mesonephros. On the other hand, the medullary region of the testes is the major gamete producing area, surrounded by the tunica albuginea. The Sexual Duct System Like the gonads, the sexual ducts pass through an early indifferent stage. In males, testicular secretory products develop the male duct system. In females, absence of testicular products results in the preservation of the default female structures and regression of the male structures. Indifferent Sexual Duct System The indifferent sexual duct system consists of the mesonephric (wolffian) ducts and the paramesonephric (müllerian) ducts. The paramesonephric ducts arise from longitudinal invaginations of the surface epithelium on the anterolateral surface of the urogenital ridge. The invaginations soon become epithelial cords, which grow caudally and terminate on the urogenital sinus between the ends of the mesonephric ducts without breaking into the sinus. These cords develop a lumen. The cranial end of each paramesonephric duct opens into the coelomic cavity as a funnel-shaped structure. Their fates depend on the gender of the gonad. Sexual Duct System if Males Development of the sexual duct system in the male depends on secretions from the testes. Under the influence of müllerian inhibiting substance (MIS), secreted by the Sertoli cells at eight weeks gestation, the paramesonephric ducts degenerate leaving only their remnants at their cranial and caudal ends. This "antimüllerian hormone" influences the surrounding mesenchyme to instruct the epithelial cells to regress. Under the influence of testosterone, secreted by the Leydig cells, the mesonephric ducts continue to develop. The mesonephric ducts differentiate into the paired ductus deferens, which transports sperm from the testis to the urethra. The most cranial portion of the mesonephric ducts regress, except for a vestige known as the appendix epididymus. Portions of the degenerating excretory mesonephric tubules (paragenital tubules) may persist near the caudal pole of the testis as the paradidymus. A few intermediately situated mesonephric excretory tubules will form the efferent ductules of the testis that join the rete testes (from seminiferous tubules). The efferent tubules merge into a highly convoluted (ductus) epididymus that continues as the vas (ductus) deferens, ultimately draining into the prostatic urethra as the ejaculatory ducts. Associated with the male genital tract is formation of the male accessory sex glands: the seminal vesicles, the prostate, and the bulbourethral (Cowper's) glands. These glands arise as epithelial outgrowths from their associated duct systems. The seminal vesicles arise from the ductus deferens. The prostate and bulbourethral glands derive from the urogenital sinus. These glands depend on androgenic stimulation for development. Below the bladder, mesenchymal cells develop intracellular receptors for circulating androgens (dihydrotestosterone, DHT). Incomplete masculinization occurs when testosterone fails to convert to DHT or when DHT fails to act within the cytoplasm or nucleus of the cells of the external genitalia and urogenital sinus. Actually, the 8 mesonephric duct and its derivatives need testosterone to develop, while the accessory glands and external male genitalia need dihydrotestosterone. Mesodermal cells having the enzyme 5α – reductase, convert testosterone into dihydrotestosterone. If intracellular androgen receptors are not present or if tissues lack receptors for DHT complexes, then external male differentiation fails to take place. Such is the case of males (46, XY) with androgen insensitivity syndrome (AIS) or testicular feminization syndrome. Because, müllerian inhibitory factor is produced by the Sertoli cells, the uterus and upper part of the vagina do not form. Here, the male has the appearance of a normal female due there is unresponsiveness to androgens. The basic etiology of the (AIS) is a loss-of-function mutation in the androgen receptor (AR) gene. Sexual Duct System of Females If either the ovaries are present or the gonads are absent or defective, the sexual duct system differentiates into a female phenotype. In the absence of testosterone the mesonephric ducts regress, leaving only rudimentary structures. In the absence müllerian inhibitory substance the paramesonephric (müllerian) ducts continue to develop into the major structures of the female genital tract. The cranial portions of the paramesonephric ducts become the uterine tubes, with their cranial parts opening into the coelomic cavity. Fimbria are located at their intraperitoneal terminations. Toward their caudal ends the paramesonephric ducts begin to approach the midline and cross the mesonephric ducts ventrally. This crossing and ultimate meeting in the midline are caused by the medial swinging of the entire urogenital ridge. The region of midline fusion of the paramesonephric ducts ultimately becomes the uterus, and the ridge of tissue that is carried with the paramesonephric ducts forms the broad ligament of the uterus. The fused paramesonephric ducts give rise to the both the corpus and cervix of the uterus. Shortly after the paramesonephric ducts reach the urogenital sinus, two solid evaginations grow out from that part of the urogenital sinus. These evaginations (sinovaginal bulbs) proliferate and form a solid vaginal plate (uterovaginal plate). At the cranial end of the plate there is proliferation of tissue that elongates the potential vagina. This increases the distance between urogenital sinus and its cranial end united to the caudal paramesonephric ducts. In the 5th month the solid vagina is canalized. Thus, the vagina has two origins: (1) the upper portion that has the fornices around the cervix, both derived from the paramesonephric ducts, and (2) the lower portion derived from the urogenital sinus. The lumen of the vagina is separated from the urogenital sinus by a thin tissue called the hymen, usually with a small opening in it around birth. Remnants of the cranial excretory tubules (mesonephros) may be retained in the mesovarium (peritoneal folds containing the ovary). These remnants are the epoöphoron and paroöphoron. Occasionally, a small portion of the mesonephric duct may be found in the wall of the uterus or vagina that later forms a Gartner's cyst, which feels like a round hard bump. Descent of the Testicles The testicles are retroperitoneal and they descend behind the peritoneal epithelium. Before descending, their cranial parts are anchored to the diaphragmatic (cranial) 9 suspensory ligament of the mesonephros and caudally to the inguinal (caudal) ligament of the mesonephros: the gubernaculum. First, under the influence of androgens acting through androgen receptors in the cranial suspensory ligament, the ligament regresses, releasing its attachment to the testes. Secondly, the testes then make a transabdominal descent down to the inguinal ring. In a third phase, the transinguinal descent, the testes are brought into the scrotum. This phase involves both the action of testosterone and the guidance of the inguinal ligament of the mesonephros. Testicular descent begins in the 7th month and descent may not be completed until birth. As it descends into the scrotum, the testes slide behind an extension of the peritoneal cavity, the vaginal process. This is a potential weak point, prone to intestinal herniation into the scrotum. Descent of the Ovaries While the paramesonephric ducts cross over medially, the ovaries move laterally. Their positions are stabilized by two ligaments, both remnants of the mesonephros. Cranially, the diaphragmatic ligament of the mesonephros becomes the suspensory ligament of the ovary (containing the ovarian vessels). The superior portion of the inguinal ligament of the mesonephros develops into the round ligament of the ovary, and its inferior portion becomes the round ligament of the uterus. The round ligament of the uterus terminates in the labia majora. External Genitalia Indifferent Stage A very early midline elevation called the genital eminence is situated just cephalic to the proctodeal depression. This structure soon develops into a prominent genital tubercle, which is flanked by a pair of genital (urethral) folds extending to the proctodeum (an ectodermal depression that will form the anal canal when ruptured). Between the genital folds is the urogenital sinus. [The urogenital sinus area will become the urethral groove in the male, and the vestibule in the female.] Somewhat lateral to the genital folds are paired genital swellings. When the original cloacal membrane breaks down during the 8th week, the urogenital sinus opens up to the outside between the genital folds. An endodermal urethral plate lines much of the open genital sinus. During the indifferent stage, these structures are virtually identical in male and female embryos. External Genitalia of Males Under the influence of dihydrotestosterone (DHT), the genital tubercle undergoes a second phase of elongation to form the penis or phallus, and the genital swellings enlarge to form the scrotal pouches. During this elongation, the phallus pulls the urethral (genital) folds forward so that they form the lateral walls of the urethral groove. The epithelial lining of the groove, which is endodermal, forms the urethral plate. The male urethra forms in a proximodistal direction by ventral folding and midline fusion of the urethral folds. At the end of the 3rd month the folds close over the urethral plate, forming the penile urethra. The most distal part of the urethra is formed in the 4th month when ectodermal cells penetrate its tip, thus forming the external urethral meatus. After the urethra has formed, the line of fusion of the urethral folds is marked 1 0 by the persistence of a ventral raphe that passes between the scrotal swellings. The scrotal swellings are separated by a scrotal septum. External Genitalia of Females In females the pattern of external genitalia is similar to the indifferent stage. The genital tubercle becomes the clitoris and the genital folds, which do not fuse, become the labia minora. The genital swellings become the labia majora. As mentioned earlier, the urogenital groove in the female is open and forms the vestibule. The female urethra, developing from the more cranial part of the urogenital sinus, is equivalent to the prostatic urethra of the male. Fetal sex determination can usually be done accurately at 16 weeks or later with expert ultrasound. Abnormalities of Sexual Differentiation Turner's syndrome – Turner's syndrome (gonadal dysgenesis) results form a chromosomal anomaly (45, XO). Individuals with this syndrome, which are phenotypically female, possess primordial germ cells that degenerate shortly after reaching the gonads. Differentiation of the gonad fails to occur, leading to the formation of a streak gonad. These people have short stature, high arched palates, webbed neck, shieldlike chest, renal abnormalities, and inverted nipples. Klinefelter syndrome - Klinefelter syndrome people have a karyotype of 47,XXY or variants of XXXY. Its occurrence is 1/500 males. Patients are characterized by infertility, gynecomastia, and varying degrees of impaired sexual maturation. Nondisjunction of the XX homologues is the most causative factor. True hermaphroditism – Individuals with true hermaphroditism, which is extremely rare, possess both testicular and ovarian tissue, Most cases are genetic mosaics. In some case the gonad is both ovary and testis (ovotestis). Most are 46,XX and reared as females. Female pseudohermaphroditism – The people are genetically female (46,XX) and are sex chromatin positive. The internal genitalia are female, but the external genitalia are masculinized. These cases occur to either an excessive production of androgen hormones from the adrenal cortex (congenital virulizing adrenal hyperplasia) or form inappropriate hormonal treatment of pregnant women. Male pseudohermaphroditism – These persons are sex chromatin negative or 46,XY. Because this condition commonly results from inadequate hormone production by the fetal testes, the phenotype can vary (i.e., internal and external parts vary as to male or female). 1 1 Testicular feminization (androgen insensitivity) syndrome – Here, individuals are genetic males (46, XY), possess internal testes, but have a normal female external phenotype, this they are raised as females. Often, this is not discovered until the person seeks treatment for amenorrhea or is tested for sex chromatin before athletic events. The testes produce testosterone, but there is a gene mutation on the X chromosome that manufactures androgen receptors. Questions 1. Which of the embryonic excretory systems is the first to regress and stop functioning? a. pronephros b. mesonephros c. metanephros d. metanephric blastema 2. The ureteric bud is an outgrowth of the ___________. a. paramesonephric duct b. metanephric blastema c. mesonephric duct d. cloaca 3. Several ____________ tubules will be incorporated into the metanephric blastema and become part of the adult kidney. a. pronephros b. mesonephros c. metanephros d. cloaca 4. The excretory units (glomeruli, tubules) of the kidney are derived from the __________. a. mononuclear phagocyte system b. metanephric blastema c. mesonephric duct d. urogenital sinus 5. The distal end of the __________ will form the urachus. a. urogenital sinus b. mesonephric duct c. metanephric blastema d. allantois 1 2 6. The solidified urachus will for the __________ ligament in the adult. a. median umbilical b. medial umbilical c. lateral umbilical d. falciform 7. The wolffian duct is the alternative name for the ___________. a. paramesonephric duct b. urogenital sinus c. mesonephric duct d. allantois 8. The area flanked where the ureteric buds enter the bladder, and the mesonephric ducts also enter the bladder, but at a lower and more medial position, is called the ________. a. cloaca b. trigone c. urachus d. allantois 9. _____________ can result in oligohydramnios and Potter facies. a. renal agenesis b. horseshoe kidney c. exstrophy of the bladder d. adult polycystic kidney disease 10. Defects in the production of polycystin proteins are seen in _______________. a. renal agenesis b. horseshoe kidney c. exstrophy of the bladder d. adult polycystic kidney disease -------------------------------------------------------------------------------------------------------------11. In the female, sex chromatin results in the creation of a _________ due to extra Xchromosomal DNA not needed. a. Sry gene b. Y chromosome c. Barr bodies d. antimüllerian protein 12. The testes-determining factor gene is located on the _____________ chromosome. 1 3 a. b. c. d. long arm of the X long arm of the Y short arm of the X short arm of the Y 13. Gender is determined when __________. a. fertilization occurs b. primordial cells migrate from the epiblast c. primordial germ cells are in the yolk sac d. oogonia are formed in the indifferent gonads 14. Sertoli cells (males) and the sex cords (male and female) are derived from __________. a. mesenchyme of the gonadal ridge b. genital ridge surface (coelomic) epithelium c. differentiated germ cells d. mesonephric ducts 15. Interstitial cells of Leydig are derived from _______________. a. mesenchyme of the gonadal ridge b. genital ridge surface (coelomic) epithelium c. differentiated germ cells d. mesonephric ducts 16. Müllerian inhibiting substance is secreted by ___________. a. Leydig cells b. oogonia c. Sertoli cells d. thecal cells 17. In the female, follicular cells appear to be derived from __________ a. mesenchyme of the gonadal ridge b. genital ridge surface (coelomic) epithelium c. differentiated germ cells d. mesonephric ducts 18. If the gender permits, the ___________ develop into the female genital duct system. a. wolffian ducts b. ureteric bud c. urogenital sinus d. müllerian ducts 19. In the male, the epididymus and vas deferens need _________ to develop and the external genitalia need __________ to develop. 1 4 a. b. c. d. dihydrotestosterone / testosterone estrogen / dihydrotestosterone testosterone / dihydrotestosterone testosterone / diethylstilbestrol 20. Androgen insensitivity syndrome is, mostly in part, due to lack of ___________. a. testosterone receptors that help develop the vas deferens b. androgen receptors in mesoderm that form the external male genitalia c. estrogen receptors that form the external female genitalia d. testes determining factor that form the testes 21. The vagina is formed from tissue of both the _________ and the ___________. a. paramesonephric ducts / urogenital sinus b. paramesonephric ducts / cloaca c. mesonephric ducts / urogenital sinus d. mesonephric ducts / cloaca 22. A Gartner's cyst in the uterus or vagina is a remnant of the ____________. a. müllerian duct b. peritoneum c. wolffian duct d. ureteric bud 23. Which of the following forms the clitoris in the female? a. genital swellings b. urethral folds c. genital tubercle d. urethral plate 24. Which of the following is 45, XO? a. Turner's syndrome b. Klinefelter's syndrome c. true hermaphroditism d. testicular feminization 25. Which of the following is 47, XXY or 48, XXXY? a. Turner's syndrome b. Klinefelter's syndrome c. true hermaphroditism d. testicular feminization