Embryo Ch12 PBL

Further branching is controlled by both (1) transcription factors and (2) growth factor signals. These are?

(1) Emx2, Pax2 (2) Wnt, FGF, BMP

5. C. The transitional epithelium lining the ureter is derived from mesoderm because the ureter develops from the ureteric bud. The ureteric bud is a diverticulum from the mesonephric duct whose origin can be traced back to the intermediate mesoderm. 6. C. The podocytes of Bowman's capsule develop from the metanephric vesicles, which are of mesodermal origin.

(c) mesoderm

The mesonephric duct in male embryos gives rise to

(formerly called wolffian ducts) epididymis, vas deferens, ejaculatory duct, and seminal vesicles. In females, the cranial end of the mesonephric duct may persist as a cystic appendix vesiculosa. Other parts of this duct may persist as the duct of the epoophoron or as a Gartner duct in the broad ligament along the lateral wall of the uterus and vagina. Remnants of the duct may give rise to Gartner duct cysts.

1. A. Reduced levels of androgens during fetal development of a XY male fetus cause feminization of the male external genitalia such that the baby can be phenotypically mistaken for female. Parents raise the XY male baby as a girl until puberty or other medical problems bring the child to medical attention

1. One day a 9-year-old girl surprisingly announces to her mother, "Guess what, mommy, I'm not a girl; I'm a boy." The mother is shocked but does not act on the comment. During the next few years, the mother notices some tomboyish behavior and difficulty in social adjustment at school. When the girl is 12 years old, puberty starts with a striking virilization of the external genitalia. The mother is extremely concerned and seeks medical attention. What is the most likely cause? (A) Male pseudointersexuality (B) Female pseudointersexuality (C) Congenital adrenal hyperplasia (D) Testicular feminization (E) Illegal use of anabolic steroids

1. C. The embryo during weeks 1-6 remains in an indifferent or undifferentiated stage. The embryo begins phenotypic sexual differentiation during week 7. 2. E. By week 12, female and male characteristics can be recognized. By week 20, phenotypic sexual differentiation is complete.

1. The indifferent embryo begins phenotypic sexual differentiation during (A) week 3 of development (B) week 5 of development (C) week 7 of development (D) week 12 of development (E) week 20 of development 2. The indifferent embryo completes phenotypic sexual differentiation during (A) week 3 of development (B) week 5 of development (C) week 7 of development (D) week 12 of development (E) week 20 of development

The permanent kidneys develope from 2 sources, what two?

1. metanephric diverticulum (ureteric bud) 2. The metanephrogenic blastema or metanephric mass of mesenchyme

When do nephrons begin to form?

10th week, and until birth. Kidneys have lobulated appearance at birth!

2. D. Female pseudointersex individuals have a 46,XX genotype. This condition is most commonly caused by congenital adrenal hyperplasia, in which the fetus produces excessive amounts of androgens. The high androgen level masculinizes the female genitalia. 3. C. Male pseudointersex individuals have a 46,XY genotype. This condition is most commonly caused by inadequate production of testosterone and MIF by the fetal testes. The low testosterone and MIF levels stunt the development of the male genitalia.

2. The most common cause of female pseudointersexuality is (A) a 46,X0 genotype (B) a 47,XXY genotype (C) lack of androgen receptors (D) congenital adrenal hyperplasia (E) inadequate production of testosterone and miillerian-inhibiting factor (MIF) 3. The most common cause of male pseudointersexuality is (A) a 45,X0 genotype (B) a 47,XXY genotype (C) inadequate production of testosterone and MIF (D) congenital adrenal hyperplasia (E) lack of androgen receptors

3. D. The sinovaginal bulbs proliferate, fuse, and form the vaginal plate under the inductive influence of the paramesonephric ducts. The vaginal plate then canalizes to form the inferior two thirds of the vagina. 4. C. The round ligament of the uterus and the ovarian ligament both form from the gubernaculum.

3. After the sinovaginal bulbs have proliferated and fused, they form a solid core of endodermal cells called the (A) vestibule of the vagina (B) uterovaginal primordium (C) urogenital sinus (D) vaginal plate (E) clitoris 4. A structure found within the adult female pelvis formed from the gubernaculum is the (A) broad ligament (B) suspensory ligament of the ovary (C) round ligament of the uterus (D) medial umbilical ligament (E) median umbilical ligament

How many stages of kidney development?

3: pronephros, mesonephros, and the metanephros (final). From craniocaudal!

4. E. The most common cause of testicular feminization syndrome is the lack of androgen receptors in the urogenital folds and labioscrotal swellings. Because these tissues lack androgen receptors, they are blind or unresponsive to androgens. Consequently, these tissues develop into female external genitalia even though the fetus has a 46,XY genotype. 5. A. Failure of the urethral folds to fuse completely results in the external urethral orifice opening onto the ventral surface of the penis, a condition known as hypospadias

4. The most common cause of testicular feminization syndrome is (A) a 45,X0 genotype (B) a 47,XXY genotype (C) inadequate production of testosterone and MIF (D) congenital adrenal hyperplasia (E) lack of androgen receptors 5. In the male, failure of the urethral folds to fuse completely results in (A) hypospadias (B) epispadias (C) cryptorchidism (D) congenital inguinal hernia (E) hydrocele

5. D. In the female, the urogenital folds remain unfused and form the labia minora. 6. C. The cranial portion of the paramesonephric ducts form the uterine tubes

5. The labia minora arise embryologically from which of the following structures? (A) Phallus (B) Labioscrotal swellings (C) Sinovaginal bulbs (D) Urogenital folds (E) Paramesonephric duct 6. The uterine tubes of the adult female are derived embryologically from which of the following? (A) Mesonephric duct (B) Mesonephric tubules (C) Paramesonephric duct (D) Paramesonephric tubules (E) Uterovaginal primordium

6. C. The gene product that is coded on the short arm of the Y chromosome is called the testesdetermining factor (TDF). 7. B. Sterility is a common result of bilateral cryptorchidism. When both testes fail to descend into the scrotum, the increased temperature they are exposed to in the abdominal cavity inhibits spermatogenesis.

6. The Y chromosome carries a gene on its short arm that codes for (A) testosterone (B) MIF (C) testes-determining factor (TDF) (D) progesterone (E) estrogen 7. Bilateral cryptorchidism usually results in (A) impotence (B) sterility (C) male pseudointersexuality (D) female pseudointersexuality (E) testicular feminization syndrome

8. A. This is a classic case of testicular feminization syndrome. A karyotype analysis would reveal that this normal-appearing 17-year-old girl actually has a 46,XY genotype. The mobile masses within the right and left labia majora are the testes and should be surgically removed because this tissue has a propensity toward malignant tumor formation. The most common cause of this syndrome is a lack of androgen receptors in the phallus, urogenital folds, and labioscrotal swellings

8. A 17-year-old girl presents with a complaint of amenorrhea. Physical examination reveals good breast development and normal amount of pubic hair. A rudimentary vagina and a mobile mass within both the right and left labia majora are found on pelvic examination. Ultrasound reveals the absence of a uterus. What is the diagnosis? (A) Testicular feminization syndrome (B) Gonadal dysgenesis (C) Cryptorchidism (D) Female pseudointersexuality (E) Hypospadias

Urachal sinus

A Failure of closure of a portion of the intraembryonic part of the allantois may result in the formation of a urachal sinus that opens at the umbilicus or into the urinary bladder. These sinuses usually are not detected unless they become infected and produce a discharge at the umbilicus or a bladder infection.

Passes through the inguinal canal

A The round ligament of the uterus passes through the inguinal canal and inserts in the labium majora. It is continuous with the ovarian ligament because they are both derived from the embryonic gubernaculum.

Derivative of the gubernaculum

A The round ligament. It descends obliquely through the developing abdominal wall (future site of the inguinal canal) and attaches to the labioscrotal fold (future labium majus).

A patient has been diagnosed as having a supernumerary ovary. This condition is due to - absence of the paramesonephric ducts - delayed migration of the primordial germ cells - the testis-determining factor - H-Y antigen - absence of the secondary sex cords

A supernumerary ovary is an extremely rare gynecologic condition. About 20 cases have been reported in the medical literature. It results from an arrest in the migration of primordial germ cells along the dorsal mesentery of the hindgut to the genital ridges. An ectopic ovary may develop from these primordial germ cells and the surrounding mesenchyme. The paramesonephric ducts give rise to the female genital tract. The testis-determining factor influences gonadal sex differentiation; and the H-Y antigen is involved in the formation of seminiferous tubules from the primary sex cords.

Name the labeled structures

A. Allantois (becomes median umbilical ligament) B. Urogenital SInus C. mesonephros (degenerates in female) D. metanephric diverticulum (primordium of renal pelvis an calices) E. urorectal septum

A seriously injured young man suffered a cardiac arrest. After cardiopulmonary resuscitation, his heart began to beat again, but spontaneous respirations did not occur. Artificial respiration was instituted, but there was no electroencephalographic evidence of brain activity. After 2 days, the man's family agreed that there was no hope of his recovery and asked that his kidneys be donated for transplantation. The radiologist carried out femoral artery catheterization and aortography (radiographic visualization of the aorta and its branches). This technique showed a single large renal artery on the right, but two renal arteries on the left, one medium in size and the other small. Only the right kidney was used for transplantation because it is more difficult to implant small arteries than large ones. Grafting of the small accessory renal artery into the aorta would be difficult because of its size, and part of the kidney would die if one of the arteries was not successfully grafted. • Are accessory renal arteries common? • What is the embryologic basis of the two left renal arteries? • In what other circumstance might an accessory renal artery be of clinical significance?

Accessory or supernumerary renal arteries are very common. Approximately 25% of kidneys receive two or more branches directly from the aorta; however, more than two is exceptional. Supernumerary arteries enter either through the renal sinus or at the poles of the kidney, usually the inferior pole. Accessory renal arteries, more common on the left side, represent persistent fetal renal arteries that grow out in sequence from the aorta as the kidneys "ascend" from the pelvis to the abdomen. Usually, the inferior vessels degenerate as new ones develop. Supernumerary arteries are approximately twice as common as supernumerary veins. They usually arise at the level of the kidney. The presence of a supernumerary artery is of clinical importance in other circumstances because it may cross the ureteropelvic junction and hinder urine outflow, leading to dilation of the calices and pelvis on the same side (hydronephrosis). Hydronephrotic kidneys frequently become infected (pyelonephritis); infection may lead to destruction of the kidneys

Corresponds to the epididymis

B The epoophoron appears in the broad ligament between the ovary and the uterine tube. It is a remnant of the mesonephric duct and some mesonephric tubules and homologous with the epididymis in males. It may become cystic and give rise to a large parovarian cyst.

Epoophoron

B The epoophoron is a vestigial structure that lies in the broad ligament between the ovary and the uterine tube. It consists of a few blind tubules connected to a short duct. If the epoophoron becomes distended with fluid, it forms a parovarian cyst. Most are small, but some enlarge to an enormous size.

Becomes the median umbilical ligament

C The urachus, a derivative of the allantois,

Cells of the cortical cords derived from the coelomic epithelium differentiate into - follicular cells - stromal cells - oogonia - theca folliculi - primordial germ cells

Cells of the coelomic (germinal) epithelium give rise to cortical cords in female embryos that surround the primordial germ cells from the yolk sac. The primordial germ cells become oogonia, and the coelomic epithelial cells become the follicular cells that surround the oogonia. The coelomic epithelium originally was called the germinal epithelium because it was believed to give rise to the oogonia; however, the term germinal epithelium is so firmly entrenched in the literature and in people's minds that it probably will be called by this name for some time.

Where is the pronephros, and do they function?

Cervical region, no, they degenerate by 4th week

Gives rise to the suprarenal cortex

Coelomic epi. The fetal suprarenal (adrenal) cortex is derived from mesenchymal cells that arise from the coelomic epithelium. These large cells make up most of the suprarenal cortex before birth, forming the massive fetal cortex. The fetal cortex gradually involutes after birth and usually is not recognizable after the first year.

Congenital Polycystic Kidney and Multicystic Dysplastic Kidney disease

Congenital polycystic disease of the kidneys is transmitted on an autosomal recessive basis. Hundreds of small cysts.. usually fatal Multicystic dysplastic kidney disease ..outcome is good since typically unilateral.. Fewer cyst than above these cysts are dilations of the nephrons, particularly of the loops of Henle.

Medullary secondary sex cords (cortical cords) do what?

Degenerate into connective tissue

A 4-year-old girl was still in diapers because she was continually wet. The pediatrician saw urine coming from the infant's vagina. An intravenous urogram showed two renal pelves and two ureters on the right side. One ureter was clearly observed to enter the bladder, but the termination of the other one was not clearly seen. A pediatric urologist examined the child under general anesthesia and observed a small opening in the posterior wall of the vagina. He passed a tiny catheter into it and injected a radiopaque solution. This procedure showed that the opening in the vagina was the orifice of the second ureter. • What is the embryologic basis for the two renal pelves and ureters? • Describe the embryologic basis of the ectopic ureteric orifice. • What is the anatomic basis of the continual dribbling of urine into the vagina?

Double renal pelves and ureters result from the formation of two metanephric diverticula (ureteric buds) on one side of the embryo. Subsequently, the primordia of these structures fuse. Both ureters usually open into the urinary bladder. Occasionally, the extra ureter opens into the urogenital tract inferior to the bladder. This occurs when the accessory ureter is not incorporated into the base of the bladder with the other ureter; instead, the extra ureter is carried caudally with the mesonephric duct and opens with it into the caudal part of the urogenital sinus. Because this part of the urogenital sinus gives rise to the urethra and the epithelium of the vagina, the ectopic (abnormally placed) ureteric orifice may be located in either of these structures, which accounts for the continual dribbling of urine into the vagina. An ectopic ureteral orifice that opens inferior to the bladder results in urinary incontinence because there is no urinary bladder or urethral sphincter between it and the exterior. Normally, the oblique passage of the ureter through the wall of the bladder allows the contraction of the bladder musculature to act like a sphincter for the ureter, controlling the flow of urine from it

Derivative of the urogenital sinus

E a pair of sinovaginal bulbs that grow out from the urogenital sinus and fuse to form a solid cord of endodermal cells called the vaginal plate. The central cells of this plate subsequently degenerate, forming the lumen of the vagina.

Composed of endodermal cells

E The vaginal plate, cells derived from the urogenital sinus.

Lining of the bladder, epithelium derived from Ecto? Endo ? Meso?

Endoderm

What does congenital inguinal hernia result from?

Failure of vaginal process to seal of from peritoneum, along route for intestines to pass into scrotum

Derivatives of the mesonephric tubules?

Female nothing. Male, the caudally placed ones will remain as the efferent ductules

What is female pseudohermaphrodism?

Female pseudohermaphroditism, failure of external genitalia to develop. Can result from hormonal difficulties relating to adrenal gland androgen difficulties

What is a main difference between male and female sex cords?

Female sex cords (cortical cords) result from secondary proliferation of mesothelia.

Descent of the testis occurs when?

From second month to after birth

A Gartner duct cyst was diagnosed in a young patient on routine pelvic examination. This condition develops from which of the following embryonic structures? - Mesonephric duct - Mesonephric tubules - Paramesonephric duct - Urogenital folds

Gartner duct cyst is formed from a vestigial remnant at the caudal end of the mesonephric duct. It is usually asymptomatic and is found in the wall of the vagina on routine pelvic examination. The mesonephric tubules regress in the female, leaving some rudimentary tubules, the epoophoron and paroophoron. The uterine tubes, uterus, and vagina are derived from the paramesonephric ducts. The labia minora develop from the urogenital folds.

What is male pseudohermaphrodism?

Genetically male, but not enough testosterone (either production or receptors). Results in female sexual differentiation

What pulls the male testis down?

Gubernaculum testis that conencts developing testis to the scrotum

Hypospadias

Hypospadias is a common abnormal condition of the urethra (about 1 in 300 males) resulting from failure of fusion of the urogenital folds. In some cases, the labioscrotal folds also fail to fuse and result in severe forms of hypospadias (e.g., penoscrotal and perineal hypospadias). This arrest of development is the result of an inadequate production of androgens by the fetal testes.

During the physical examination of a newborn male infant, it was observed that the urethra opened on the ventral surface of the penis at the junction of the glans and body. The penis was curved toward the undersurface of the penis. • Give the medical terms for the anomalies described. • What is the embryologic basis of the abnormal urethral orifice? • Is this anomaly common? Discuss its etiology.

Hypospadias of the glans is the term applied to an anomaly in which the urethral orifice is on the ventral surface of the penis near the glans penis. The ventral curving of the penis is called chordee. Hypospadias of the glans results from failure of the urogenital folds on the ventral surface of the developing penis to fuse completely and establish communication with the terminal part of the spongy urethra within the glans penis. Hypospadias may be associated with an inadequate production of androgens by the fetal testes, or there may be resistance to the hormones at the cellular level in the urogenital folds. Hypospadias is thought to have a multifactorial etiology because close relatives of patients with hypospadias are more likely to have the anomaly than the general population. Glanular hypospadias, or hypospadias of the glans, a common anomaly of the urogenital tract, occurs in approximately one in every 300 male infants

Incomplete division of the metanephric diverticulum (ureteric bud) results in - bifid ureter - supernumerary kidney - duplication of the ureter - partial ureteral duplication - bifid ureter and supernumerary kidney

Incomplete division of the metanephric diverticulum (i.e., before the renal pelvis forms) usually results in the development of two ureters. One of the ureters may have an ectopic orifice; that is, it may open into the urethra in males or the vagina in females. Complete division of the ureteric bud (before the calices form) results in incomplete ureteral duplication (i.e., bifid or Y-shaped ureter or double renal pelvis).

Two sources of vaginal plate (derivative of sinovaginal bulbs)?

Intermediate mesoderm of paramesonephric ducts at cranial end, and the endoderm of the urogenital sinus

How does the uterus (and its round ligament) divide the pelvic cavity?

Into uterorectal and uterovesical pouches

What is peculiar about female development?

It is default

What are the primary sex cords?

Male development, proliferation of mesenchyme on the gonadal ridge, cells divide and penetrate into underlying mesenchyme

Genital ducts during indifferent phase?

Mesonephric (Wolffian) and paramesonephric (Mullerian) ducts. Mullerian ducts open cranially into peritoneal and caudally into urogenital sinus

What are Wolffian ducts?

Mesonephric ducts, eventually to develop into epididymis, vas deferens, seminal vesicles

Structures of the mesonephros?

Mesonephric tubules (become the efferent ductules of the testes), mesonephric ducts (Wolffian ducts, distally connected to the urogenital sinus) and also forms trigone of bladder

What is the urethra derived from?

Middle pelvic part of urogenital sinus (entire urethra in female and prostatic urethra in male)

Tunica albuginea in females?

None

Positioning of primary sex cords?

Outer (Cortex) region. Inner (medullary) region

What does estrogen and no anti-mullerian hormone do?

Paramesonephric duct becomes uterine tube, uterus, and upper portion of vagina

What are Mullerian ducts?

Paramesonephric ducts, eventually to develop into Fallopian tubes, uterus, cervix, and upper vagina

Expression of what 3 transcription factors is required for GDNF to be expressed in the metanephric mesenchyme.

Pax2, Eya1, Sall1

Things that can go wrong with kidney rotation or ascension? What is Extrophy of Bladder

Pelvic kidney, or ectopic kidney (really not a serious problem a lot of times). or Horseshoe kidney when inferior poles merge. Exposure of mucosa surface of post wall of bladder, caused by incomplete median closure of inf part of ant abdominal wall due to absence of mesenchymal cells migrating b/w ectoderm and endoderm of abdominal wall (cloacal membrane)

What will also descend with the male gonad?

Process vaginalis (outgrowth of the peritoneum

How do gonads initially develop?

Retroperitoneal

A 32-year-old woman with a short history of cramping lower abdominal pain and tenderness underwent a laparotomy because of a suspected ectopic pregnancy. The operation revealed a pregnancy in a rudimentary right uterine horn. The gravid uterine horn was totally removed. • Is this type of uterine anomaly common? • What is the embryologic basis of the rudimentary uterine horn?

Rudimentary horn pregnancies are very rare; they are clinically important, however, because it is difficult to distinguish between this type of pregnancy and a tubal pregnancy (see text). In the present case, the uterine anomaly was the result of retarded growth of the right paramesonephric duct and incomplete fusion of this duct with its partner during development of the uterus. Most anomalies resulting from incomplete fusion of the paramesonephric ducts do not cause clinical problems; however, a rudimentary horn that does not communicate with the main part of the uterus may cause pain during the menstrual period because of distention of the horn by blood. Because most rudimentary uterine horns are thicker than uterine tubes, a rudimentary horn pregnancy is likely to rupture much later than a tubal pregnancy.

What does the Y-chromosome have that determines male sex?

SRY (sex-determining region Y), which encodes the Testis-Determining Factor (TDF). TDF encourages development of seminiferous tubules, and later the testis, which then secretes testosterone and Mullerian inhibiting factor

Where does the metanephric system initially develop?

Sacral region, but it will ascend to the upper lumbar region

What are the ureters derived from?

Stalk of the metanephric diverticulum, while the cranial portion of the diverticulum undergoes repetitive branching events to differentiate into collecting tubules

From what does the metanephros develop?

Starts developing at 5th week, from two different sources of intermediate mesoderm: ureteric buds (a diverticulum from the distal mesonephric duct), and the metanephric blastema

A 10-year-old boy suffered pain in his left groin while attempting to lift a heavy box. Later he noticed a lump in his groin. When he told his mother about the lump, she arranged an appointment with the family physician. After a physical examination, a diagnosis of indirect inguinal hernia was made. • Explain the embryologic basis of this type of inguinal hernia. • Based on your embryologic knowledge, list the layers of the spermatic cord that would cover the hernial sac.

The embryologic basis of indirect inguinal hernia is persistence of the processus vaginalis, a fetal outpouching of peritoneum. This fingerlike pouch evaginates the anterior abdominal wall and forms the inguinal canal. A persistent processus vaginalis predisposes to indirect inguinal hernia by creating a weakness in the anterior abdominal wall and a hernial sac into which abdominal contents may herniate if the intra-abdominal pressure becomes very high (as occurs during straining). The hernial sac would be covered by internal spermatic fascia, cremaster muscle, and cremasteric fascia.

Gives rise to the clitoris

The genital tubercle elongates in both sexes to form a phallus. In females, growth of the phallus normally slows after the eighth week; it becomes the clitoris.

An imperforate hymen was diagnosed in an infant. This structure - is a mucous membrane at the entrance to the vestibule - ruptures during the embryonic period - separates the lumen of the vagina from the urogenital sinus in the fetus - develops from the labia minora - is formed by the paroophoron

The hymen is a thin fold of mucous membrane at the entrance to the vagina. It usually ruptures during the perinatal period. A condition known as imperforate hymen results when this fails to occur. The incidence of imperforate congenital hymen is about 0.1 % or less. Fluid accumulation (hydrocolpos and hydrometrocolpos), especially at menarche, leads to a characteristic protruding of the membrane at the entrance to the vagina. The paroophoron is not involved in the formation of the hymen. It is a mesonephric remnant in females.

The interstitial cells (of Leydig) - are derived from the surface epithelium - secrete mullerian-inhibiting factor - influence the differentiation of the ovary - produce testosterone - secrete progesterone

The interstitial cells (of Leydig) are derived from mesenchymal cells. By the eighth week, these cells begin to produce the androgenic hormone testosterone, which is responsible for the differentiation of the male genital ducts and external genitalia. Progesterone is secreted by the corpus luteum. Müllerian-inhibiting factor, which is produced by the sustentacular cells (of Sertoli), suppresses the development of the paramesonephric duct in the male. The development of the ovary is not influenced by the interstitial cells.

Which of the following cells are derived from mesenchyme? - Oogonia - Interstitial cells - Sertoli cells - Follicular cells - Spermatogonia

The interstitial cells (of Leydig) develop from the mesenchyme located between the developing seminiferous tubules. Some cells of this embryonic connective tissue enlarge and become grouped together to form clusters of interstitial cells. These cells produce androgens during fetal life that masculinize the genital ducts and external genitalia of males. The oogonia and spermatogonia develop from primordial germ cells; the follicular and Sertoli cells develop from the primary sex cords derived from the coelomic epithelium.

The metanephric diverticulum appears as a dorsal outgrowth from the - mesonephric duct - intermediate mesoderm - urogenital sinus - metanephric mesoderm - cloaca

The metanephric diverticulum (ureteric bud) develops as a dorsal outgrowth from the mesonephric duct near its entry into the cloaca. The pronephric duct, which becomes the mesonephric duct, originally developed as an outgrowth from the intermediate mesoderm.

The metanephric diverticulum (ureteric bud) is derived from the - urogenital sinus - splanchnic mesoderm - metanephric mesoderm - somatic mesoderm - mesonephric duct

The metanephric diverticulum develops as a hollow outgrowth from the mesonephric duct near its junction with the urogenital sinus. Shortly after it forms, the distal end of this outgrowth, often called the ureteric bud, expands and comes into contact with the metanephric mesoderm of the most caudal part of the nephrogenic cord.

As the metanephric diverticulum grows dorsocranially, it becomes covered by __________ mesoderm - splanchnic - mesonephrogenic - somatic - metanephric - intermediate

The metanephric mass of mesoderm (metanephric blastema), derived from the nephrogenic cord, forms a mesenchymal cap over the expanded end or ampulla of the ureteric bud. This mesenchyme gives rise to the nephrons. Differentiation of the nephrons is induced by an inductor substance produced by the ampulla of the ureteric bud and, later, the collecting tubules.

Embryologically, each uriniferous tubule consists of two parts, which become confluent at the junction of the - renal corpuscle and the proximal convoluted tubule - proximal convoluted tubule and the loop of Henle - descending and ascending limbs of the loop of Henle - ascending limb of the Henle loop and the distal convoluted tubule - distal convoluted tubule and the collecting tubule

The nephron, consisting of a renal corpuscle (glomerulus and Bowman capsule) and its associated tubules, develops from the metanephric mass of mesoderm around the collecting tubules. The end of a distal convoluted tubule of the nephron contacts and soon becomes confluent with a collecting tubule to form a uriniferous tubule.

Primary sex cord

The primary sex cords give rise to the seminiferous tubules, tubuli recti, and rete testis. They lose their connections with the surface epithelium as the tunica albuginea forms.

Primary sex cords in males

The primary sex cords in male embryos condense and extend into the medulla of the developing testis. Here they branch, and their ends anastomose to form the rete testis.

Primordial germ cells are first recognizable early in the fourth week in the - dorsal mesentery - primary sex cords - wall of the yolk sac - gonadal ridges - wall of the allantois

The primordial germ cells are visible early in the fourth week between the endoderm and the mesoderm of the yolk sac, near the origin of the allantois. Later during the fourth week, as the yolk sac is partially incorporated into the embryo, the primordial germ cells migrate along the dorsal mesentery of the hindgut and enter the developing gonads. They give rise to the oogonia and spermatogonia in the ovaries and the testes, respectively.

The human pronephros, a transitory nonfunctional "kidney," appears early in the fourth week as a few cell clusters in the region __________ of the embryo. - occipital - cervical - thoracic - abdominal - pelvic

The rudimentary pronephric "kidneys" appear in the cervical region. They have pronephric ducts that run caudally and open into the cloaca. The caudal parts of these ducts persist as the mesonephric ducts of the next set of kidneys that develop (the mesonephroi). In lower vertebrates, the pronephric ducts play an essential part in the induction of mesonephric tubules. They probably exert a similar influence in human embryos.

The feminization of the external genitalia is determined by the - sinovaginal bulbs - H-Y antigen - ovaries - absence of androgens - epoophoron

The sinovaginal bulbs give rise to the vagina. The H-Y antigen directs the formation of seminiferous tubules from the primary sex cords; its absence in the female embryo results in the development of the ovaries. Sexual differentiation of the female external genitalia results from a lack of androgens or from androgen insensitivity. The epoophoron is a mesonephric remnant in females.

Navicular fossa

The terminal portion of the penile urethra, the navicular fossa, is derived from the glandular plate. This plate is formed by an ectodermal ingrowth into the glans penis from the surface epithelium. Subsequent splitting of this plate forms a groove on the ventral surface of the glans. Closure of the urethral groove moves the external urethral orifice to the tip of the glans penis and joins this part of the spongy urethra with that formed by fusion of the urogenital folds.

Which of the following folds give rise to labia minora? - Genital - Labioscrotal - Urogenital - Urorectal - Labial

The urogenital folds in the female fetus usually do not fuse but develop into the labia minora. In the presence of androgenic substances, they may fuse. In males, the urogenital folds fuse, closing the urethral groove and forming the spongy (penile) urethra.

The urethral groove in the female fetus usually becomes the - urethral orifice - urethra - fossa navicularis - frenulum of clitoris - vestibule of vagina

The urogenital folds usually do not fuse in females, and the urethral groove between them persists as the vestibule of the vagina (the space between the labia minora). The urethra and vagina open into the vestibule.

The most common cause of female pseudohermaphroditism is

The usual congenital form of the adrenogenital syndrome results from an inborn error of metabolism. The pituitary gland secretes excess corticotropin, causing hyperplasia of the fetal cortex of the suprarenal glands and an overproduction of androgens. These hormones cause masculinization of female fetuses (female pseudohermaphroditism).

A bicornuate uterus was diagnosed in a 20-year-old patient who had been referred to a gynecologist on account of several miscarriages. This uterine anomaly results from - failure of fusion of the mesonephric ducts - failure of the sinovaginal bulbs to fuse - failure of fusion of the paramesonephric ducts - absence of the urogenital sinus - none of the above

The uterus develops from the lateral fusion of the paired paramesonephric ducts, followed by degeneration of the intervening septum. Duplication of the uterus results from a failure of this process, and it may result in two separate uteri. The mesonephric duct does not contribute to the development of the female genital tract, except for some vestigial remnants. The sinovaginal bulbs fuse and form the vaginal plate. The urinary bladder, urethra, vagina, urethral and paraurethral glands, as well as the greater vestibular glands, are derived from the urogenital sinus.

A 16-year-old girl with a history of primary amenorrhea and cyclic pelvic pain was referred to the gynecologist. Careful examination revealed the presence of an imperforate hymen. This condition results from which of the following? - Failure of the vaginal plate to canalize - Cervical atresia - Processus vaginalis - Androgen insensitivity syndrome - Failure of the sinovaginal bulbs to develop

The vaginal plate, which is formed from the sinovaginal bulbs, gives rise to the vagina and the hymen. Imperforate hymen results from a failure of the inferior end of the vaginal plate to canalize. An imperforate hymen leads to hematocolpos, the accumulation of blood produced each month by the cyclic changes of a functional endometrium. The hymen usually presents itself on examination as a bulging, bluish membrane at the entrance to the vagina.

Differentiates after birth

The zona reticularis of the adrenal cortex. zona glomerulosa and zona fasciculata are present at birth but not fully differentiated.

Tunica albuginea in males?

Thick

A 20-year-old woman was prevented from competing in the Olympics because her buccal smear test was chromatin negative, indicating that she had a male sex chromosome complement. • Is she a male or a female? • What is the probable basis for her failing to pass the sex chromatin test? • Is there an anatomic basis for not allowing her to compete in the Olympics?

This young woman is female, although she has a 46, XY chromosome complement. She has the androgen insensitivity syndrome. Failure of masculinization to occur in these individuals results from a resistance to the action of testosterone at the cellular level in genitalia

BEFORE any induction occurs, what transcription factor is expressed in the metanephrogenic blastema in order to support the survivial uninducted mesenchyme

WT1

What is external female genitalia development dependent on?

absence of testosterone, presence of estrogens

A 14-year-old girl was admitted because of bilateral inguinal masses. She had not begun to menstruate but showed normal breast development for her age. Her external genitalia were feminine, the vagina was shallow, but no uterus could be palpated. Her sex chromatin pattern was negative. What is the most likely diagnosis?

androgen insensitivity syndrome, often considered a form of male pseudohermaphroditism, but these females do not have ambiguous external genitalia (that would be called partial AIS); x linked recessive, resistance to action of testosterone in genital tubercle and labioscrotal an urethral folds

When is the mesonephros functional? And, whats the purpose?

appears late in the 4th week, but functional b/w 6-8 weeks. Its an interm kidney for about 4 weeks

What are the ureteric buds, and what of their components?

arose from mesonephric duct (Wolffian duct) ..adult ureter, renal pelvis, major and minor calyces, and 1-3 million collecting tubules

Where is the intermediate mesoderm positioned?

between somites (paraxial mesoderm) and lateral plate mesoderm

When is the metanephros functional?

by the 11-13 weeks

When does most of the mesonephros system go away by?

by the end of second month of development.. degenerate towards the end of the first trimester

remnant of the urachus

c Remnants of the urachus that do not become fibrous and form the median umbilical ligament may accumulate fluid and become cystic. Small cysts commonly are detected in sections of the urachus or median umbilical ligament, but most cysts are not detected in living people unless they become infected and enlarge.

Derivative of paramesonephric duct

c The uterine tube The fused portions of these ducts give rise to the uterus.

What is the receptor for GDNF? Where is this recepotor 1st expressed?

c-ret mesonephric duct.. later on the metanephric diverticulum

What forms the uterus?

caudal ends of the paramesonephric ducts fusing in the midline, with accompanying mesentery forming the broad ligament of the uterus

a neonate was found to have chromatin-positive nuclei, ambiguous external genitalia, and an elevated 17-ketosteroid output. What is the most likely diagnosis?

congenital adrenocortical hyperplasia in 21 hydroxylase deficiency: defective conversion of progesterone to 11-deoxycorticosterone due to gene inactivation of CYP21A2 via recombination wth neighboring psegdogene on chromosome 6p21 (CYP21A1)

Cortex sex cords, what do they become?

degenerate into tough connective tissue called the tunica albuginea

Labia minora

develop from the urogenital folds. In male embryos that receive adequate amounts of androgenic hormones, the urogenital folds fuse to form the spongy urethra.

What is external male genitalia development dependent on?

dihydrotestosterone (metabolite of testosterone)

When does the pronephros develop? Distinguishing characteristic?

early in 4th week. made up of segemented nephrogenic cords, excretory units (pronephric tubules) that empty into pronephric duct which runs caudally to open in the cloaca. degenerates by end of 4th week

When does the metanephros appear?

early in the fifth week... functional about 4 weeks later

By what time does the pronephros system disappear?

end of 4th week

Exstrophy of the bladder (ectopia vesicae) often is associated with

epispadias, a condition in which the urethra opens on the dorsal surface of the penis. This severe anomaly is very rare. In females with epispadias, there is a fissure in the urethra that opens on the dorsal surface of the clitoris.

What purpose does the metanephric blastema have?

excretory components. eventually become the nephrons of the kidneys (proximal convoluted tubule, Henle's loops, distal convoluted tubule, and Bowman's capsule)

What does hypospadias develop from?

failure of the urogenital folds to fuse normally in males

Derivatives of the mesonephric ducts?

female nothing. male the epididymis, and the vas deferens Distal portion makes trigone of bladder

What is the clitoris derived from?

genital tubercle

What gives rise to the penis?

genital tubercle (glans penis, shaft of penis), urethral folds (body of the penis)

Indifferent phase of external genitalia, superior to inferior?

genital tubercle, paired urethral folds, paired genital swellings (labioscrotal), and the paired anal folds

What happens during descent of the ovaries?

gubernaculum helps descend the ovaries a little.

What does bicornate uterus or double uterus result from?

incomplete or non-fusion of paramesonephric ducts

What sources does the urogenital system develop from?

intermediate mesenchyme derived from the dorsal body wall

SO, whats the point in GDNF?

its essential role in induction and branching of metanephric diverticulm (branching morphogenesis)

Labia majora comes from?

labioscrotal swellings

What happens to the intermediate mesoderm as a result of horizontal folding?

longitudional elevation- forms the urogenital ridge on each side of the dorsal aorta

Where do interstitial cells of Leydig come from? What do they do?

mesenchymal cells within the gonadal ridge, secrete testosterone

What kind of tissue are paramesonephric ducts?

mesoderm

What tissue layer does erectile tissue come from (male and female)?

mesoderm

Where does the nephron come from?

metanephric blastema

What is reciprocal induction

metanephric diverticulum and metanephrogenic blastema interact an induuce each other. Branching of the metanephric diverticulum is dependent on induction by the metanephric mesenchyme . Differentiation of the nephrons depends on induction by the collection tubules

How do kidneys ascend and rotate?

metanephric kidneys in pelvis, ventral to sacrum, then abdomen where they move apart. The embryo grows CAUDALLY (essentially down an away from kidneys)..the hilum, which was initially ventral, rotates medially appx 90 degrees..kidneys end up retroperitoneal on post abdominal wall by week 9

What are the kidneys derived from?

nephrogenic cord of the urogenital ridge..URETERIC BUD from mesonephros except for the nephrons which are from metanephric blastema

What part of the urogenital ridge gives rise to the urinary system and which part to the genital system?

nephrogenic cord= urinary gonadal ridge= genital system

Suprarenal medulla derived from

neuroectoderm. Neural crest cells, comparable to those that form sympathetic ganglia, invade the mesodermal suprarenal cortex on its medial side and soon become surrounded by it.

What is too little amniotic fluid called?

oligohydramnios

Derivatives of female gubernaculum?

ovarian ligament (upper portion), roudn ligament (lower portion)

Cortex secondary sex cords do what?

proliferate and surround primordial germ cells forming ovarian follicles

Medullary sex cords, what do they become?

proliferate and surround primordial germ cells, and form seminiferous tubules (site of spermatogenesis)

Roles of sustentacular cells of Sertoli?

secretion of anti-mullerian hormone (AMH): seminiferous tubule and rete testis development from sex cords, Leydig cell development (production of testosterone), develpoment of mesonephric ducts, degeneration of paramesonephric ducts

Where does the smooth muscle of the bladder come from?

surrounding mesoderm

Supernumerary renal arteries are

terminal or end arteries. If such an artery is damaged or ligated, the part of the kidney supplied by it becomes ischemic. As the kidney "ascends" from the pelvis into the abdomen, it continually acquires new branches from the aorta. Variations of the renal arteries reflect the persistence of these vessels, which normally disappear. Supernumerary renal arteries are compatible with postnatal life and play no part in the rotation of the kidneys.

What is the bladder derived from?

the CRANIAL VESICAL portion of the urogenital sinus.. which then continues with allantois

A neonate with an apparent perineal hypospadias was found to have chromatin-negative nuclei. Gonads were palpable in the inguinal canals. The mother previously had given birth to an apparent female child with ambiguous external genitalia. This girl, now 12 years old, shows strong signs of virilization. What is the most likely diagnosis of the condition in the present infant?

the apparent female infant was a male pseudohermaphrodite. Were it not for the family history of intersexuality, the most likely diagnosis would be hypospadias. The cause of this condition is either a deficiency in the production of androgens or a defect in end-organ responsiveness to androgens.

External spermatic fascia is an extenson of

the external oblique aponeurosis.

What is cryptorchidism?

undescended testes, results from abnormalities with testicular descent, can be found anywhere along route of testicular descent. individuals are sterile

Unilateral renal agenesis vs Bilateral

unilateral renal agenesis is relatively common and asymptomatic, bilateral renal agenesis is rare and fatal. associated with oligohydraminos (small amt of amniotic fluid), dies almost immediately after birth. Characteristic facial appearance: eyes wide apart w/epicanthic folds, ears low, nose broad an flat

What is the mesonephros system derived from?

upper thoracic to upper lumbar (L3) segments of intermediate mesoderm

What forms the penile urethra?

urethral groove between the urethral folds. Distal Glans urethra formed by solid cord of ectodermal cells. Epithelium of terminal part of the urethra is derived from surface ectoderm

Labia minor comes from?

urogenital folds

The paramesonephric ducts in female embryos give rise to the

uterine tubes and uterus