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Flashcards in Embryology Deck (44)
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1

The fetal kidneys develop from which of the following embryonic structures? a. Paraxial (somite) mesoderm b. Intermediate mesoderm c. Neural tube d. Lateral mesoderm

B. Intermediate mesoderm

2

At what gestational time point does the metanephros development begin?

a. 2 weeks b. 3 weeks c. 4 weeks d. 5 weeks

C. 4 weeks

3

Which of the following statements is TRUE of the metanephric development?

a. It requires the reciprocal inductive interaction between Müllerian duct and metanephric mesenchyme.

b. The calyces, pelvis, and ureter derive from the differentiation of the metanephric mesenchyme.

c. Older, more differentiated nephrons are located at the periphery of the developing kidney, whereas newer, less differentiated nephrons are found near the juxtamedullary region.

d. In humans, although renal maturation continues postnatally, nephrogenesis is completed by birth

D. IT requires the inductive interaction between the ureteric bud and metanephric mesenchyme. the calyces pelvis and ureter derive from the ureteric bud. Older more differentiated nephros are located at the inner part of the kidney near the juxtamedullary region. 

4

The fused lower pole of the horseshoe kidney is trapped by which of the following structures during the ascent?

a. Inferior mesenteric artery

b. Superior mesenteric artery

c.Celiac artery

d. Common iliac artery

A. IMA

5

The homozygous gene disruption (gene knockout) in which of the following molecules does NOT lead to a significant renal maldevelopment in mice?

a. WT-1

b. Pax-2

c. GDNF

d. p53

D. P53

Mutant Wt-1 do not form ureteric buds

PAX-2 gene knockout mice -> no nephric duct, mullerian duct, ureteric bud, metanephric mesenchyme form, animals die 1 day from birth

GDNF knockout mice -> ureteric bud is impaired

6

Which of the following statements is NOT TRUE of GDNF?

a. It is a ligand for the RET receptor tyrosine kinase.

b. GDNF gene knockout mice demonstrate an abnormal renal development.

c. It is expressed in the metanephric mesenchyme but not in the ureteric bud.

d. GDNF arrests the ureteric bud growth in vitro

D. GDNF arrests the ureteric bud growth in vitro

 

7

The bladder trigone develops from which of the following structures? a. Mesonephric ducts b. Müllerian ducts c. Urogenital sinus d. Metanephric mesenchyme

C Urogenital sinus

8

The urachus involutes to become:

a. verumontanum.

b. the median umbilical ligament.

c. appendix testicle.

d. epoophoron

b. at 12 weeks, the urachus involutes to become the median umbilical ligament

9

Which of the following statements is NOT TRUE of bladder development?

a. The bladder body and trigone is derived from the urogenital sinus and not the terminal portion of the mesonephric ducts.

b. Bladder compliance seems to be low during early gestation, and it gradually increases thereafter.

c. Epithelial-mesenchymal inductive interactions appear to be necessary for proper bladder development.

d. Histologic evidence of smooth muscle differentiation begins near the bladder neck and proceeds toward the bladder dome.

D. at 7-12 weeks, the surrounding connective tissues condense and smooth muscle fibers begin to appear, first at the region of the bladder dome and later proceeding toward the bladder neck

10

The primordial germ cell migration and the formation of the genital ridges begin at which time point during gestation?

a. Third week b. Fifth week c. Seventh week d. Ninth week

B. During 5th week, primordial germ cells migrate from the yolk sac along the dorsal mesentery to populate the mesenchyme of the posterior body wall near the 10th thoracic level. , the arrival of primordial germ cells in the area of future gonads serves as the signal for the existing cells of the mesonephros and the adMacent coelomic epithelium to proliferate and form a pair of genital ridges Must medial to the developing mesonephros.

11

Which of the following statements is NOT TRUE of the paramesonephric (müllerian) ducts? a. Both male and female embryos form paramesonephric (müllerian) ducts.

b. In male embryos, the paramesonephric ducts degenerate under the influence of the MIS (müllerian-inhibiting substance) produced by the Leydig cells.

c. In male embryos, the paramesonephric ducts become the appendix testis and the prostatic utricle.

d. In female embryos, the paramesonephric ducts form the female reproductive tract, including fallopian tubes, uterus, and upper vagina

B. In male embryos, the paramesonephric ducts degenerate under the influence of the MIS (müllerian-inhibiting substance) produced by the Leydig cells. A new pair of ducts, called the paramesonephric (müllerian) ducts, begins to form Must lateral to the mesonephric ducts in both male and female embryos. These ducts arise by the craniocaudal invagination of thickened coelomic epithelium, extending all the way from the third thoracic segment to the posterior wall of the developing urogenital sinus. The caudal tips of the paramesonephric ducts adhere to each other as they connect with the urogenital sinus between the openings of the right and left mesonephric ducts. The cranial ends of the paramesonephric ducts form funnel-shaped openings into the coelomic cavity (the future peritoneum). As developing Sertoli cells begin their differentiation in response to the SRY (sexdetermining region of the Y chromosome), they begin to secrete MIS, which causes the paramesonephric (müllerian) ducts to regress rapidly between the 8th and 10th weeks. Small müllerian duct remnants can be detected in the developed male as a small tissue protrusion at the superior pole of the testicle, called the appendix testis, and as a posterior expansion of the prostatic urethra, called the prostatic utricle. In female embryos, MIS is absent, so the müllerian ducts do not regress and instead give rise to fallopian tubes, uterus, and vagina.

12

Which of the following structures in the male reproductive tract develops from the urogenital sinus? a. Vas deferens b. Testis c. Prostate d. Appendix epididymis

B. Prostate. Vas deferens and appendix epididymis all develop from the mesonephric ducts. Testis from the gonadal ridge. The prostate and bulbourethral glands develop from the urogenital sinus.

13

Which of the following statements is NOT TRUE of normal prostate development?

a. It requires the conversion of testosterone into dihydrotestosterone by 5α-reductase. b. It is dependent on epithelial-mesenchymal interactions under the influence of androgens. c. It is first seen at the 10th to 12th week of gestation. d. It requires the effects of MIS.

The prostate gland begins to develop during the 10th to 12th week as a cluster of endodermal evaginations budding from the pelvic urethra (derived from the urogenital sinus). These presumptive prostatic outgrowths are induced by the surrounding mesenchyme, and this process depends on the conversion of testosterone into dihydrotestosterone by 5α-reductase. Similar to renal and bladder development, prostatic development depends on mesenchymal-epithelial interactions but under the influence of androgens. There is no evidence that MIS plays a direct role in prostate development.

14

In female embryos, the remnants of the mesonephric ducts persist as the following structures EXCEPT:

a. epoophoron. b. paroophoron. c. hymen. d. Gartner duct cysts

C. hymen

15

Which of the following statements is NOT TRUE of the external genitalia development? a. The appearance of the external genitalia is similar in male and female embryos until the 8th week. b. The external genital appearance of males who are deficient in 5α-reductase is similar to that of females. c. In males, the formation of distal glandular urethra may occur by the fusion of urethral folds proximally and the ingrowth of ectodermal cells distally. d. In females, the urethral folds become the labia majora, and the labioscrotal folds become the labia minora

d. In females, the urethral folds become the labia majora, and the labioscrotal folds become the labia minora. The early development of the external genital organ is similar in both sexes until 8 weeks gestation. Early in the fifth week, a pair of swellings called cloacal folds develops on either side of the cloacal membrane. These folds meet Must anterior to the cloacal membrane to form a midline swelling called the genital tubercle. During the cloacal division into the anterior urogenital sinus and the posterior anorectal canal, the portion of the cloacal folds flanking the opening of the urogenital sinus becomes the urogenital folds, and the portion flanking the opening of the anorectal canal becomes the anal folds. A new pair of swellings, called the labioscrotal folds, then appears on either side of the urogenital folds. In the absence of dihydrotestosterone, the primitive perineum does not lengthen, and the labioscrotal and urethral folds do not fuse across the midline in the female embryo. The phallus bends inferiorly, becoming the clitoris, and the definitive urogenital sinus becomes the vestibule of the vagina. The urethral folds become the labia minora, and the labioscrotal folds become the labia maMora. The external genital organ develops in a similar manner in genetic males who are deficient in 5α-reductase and therefore lack dihydrotestosterone.

16

The testicles descend to the level of internal inguinal ring by which time point during gestation?

a. Sixth week b. Third month c. Sixth month d. Ninth month

B third month

The two stages of testicular descent. (A) Before descent, the developing testis is held in the urogenital ridge by the cranial suspensory ligament (CSL) cranially and the gubernaculum (G) caudally. The adjacent Wolffian duct (WD) forms the epididymis and vas deferens in the male, and the Müllerian duct (MD) forms the uterus and tubes in the female. (B) At the end of the transabdominal phase (*15 weeks or 3rd month), the testis is held near the future inguinal ring by the swelling reaction in the gubernaculum. The skin just beyond the gubernaculum is over the future external inguinal ring, as the scrotum is remote in the perineum of humans. (C) The inguinoscrotal phase requires the gubernaculum to elongate to the scrotum, under control of androgens and calcitonin gene–related peptide (CGRP) released from the genitofemoral nerve (GFN). After migration is complete, the peritoneum of the processus vaginalis (PV) closes and then completely involutes and disappears.

17

Which of the following statements is NOT TRUE of the sexdetermining region of the Y chromosome (SRY)?

a. Its expression triggers the primitive sex cord cells to differentiate into the Sertoli cells. b. Approximately 25% of sex reversal conditions in humans are attributable to SRY mutations. c. It is located on the short arm of the Y chromosome. d. It causes the regression of mesonephric ducts.

D. It causes the regression of mesonephric ducts. When the Ylinked master regulatory gene, called SRY, is expressed in the male, the epithelial cells of the primitive sex cords differentiate into Sertoli cells, and this critical morphogenetic event triggers subsequent testicular development. Analysis of DNA narrowed the location of the SRY to a relatively small region within the short arm of the chromosome. It is now clear that only about 25% of sex reversals in humans can be attributed to disabling mutations of the SRY.

18

The glomerulus, proximal tubule, loop of Henle, and distal tubule are derived from the ___

metanephric mesenchyme

19

The Weigert-Meyer rule states that the most lateral and cephalad ureteric orifice arises ____  and may demonstrate reflux whereas the most medial and caudad orifice drains the ____ and may be associated with a ____

from the lower pole, upper pole, ureterocele.

20

Sertoli cells produce ____, which causes regression of the ___

müllerian-inhibiting substance, müllerian ducts

21

Testosterone is secreted by the ___ and stimulates the ____ ducts to form the _

Testosterone is secreted by the Leydig cells and stimulates the wolffian ducts to form the vas deferens and seminal vesicles

22

When ____ is deficient, prostatic growth and development is severely compromised.

When 5α-reductase is deficient, prostatic growth and development is severely compromised.

23

In the absence of müllerian-inhibiting substance and androgens, the wolffian ducts ____ and the müllerian ducts give rise to the _____.

In the absence of müllerian-inhibiting substance and androgens, the wolffian ducts degenerate and the müllerian ducts give rise to the fallopian tubes, uterus, and upper two-thirds of the vagina.

24

Boys with spina bifida have a 23% incidence of _____.

Boys with spina bifida have a 23% incidence of cryptorchidism.

25

If the _____ complex is translocated to an X chromosome, an XX female will have male characteristics.

If the SRY gene complex is translocated to an X chromosome, an XX female will have male characteristics.

26

The ______ is important for the normal development and growth of the kidney.

The renin-angiotensin system is important for the normal development and growth of the kidney.

27

Circulating ____ and the conversion of ____ are critical to the normal development of the prostate and male external genitalia.

Circulating androgens and the conversion of testosterone to dihydrotestosterone (DHT) are critical to the normal development of the prostate and male external genitalia.

28

A defect in the ____ may result in hypospadias, cryptorchidism, and ambiguous genitalia (disorders of sex development).

A defect in the WT1 gene may result in hypospadias, cryptorchidism, and ambiguous genitalia (disorders of sex development).

29

Defects in the ____ result in abnormal masculinization of the external genitalia

Defects in the androgen receptor result in abnormal masculinization of the external genitalia

30

______ appears to be important for the transit of the testis through the inguinal canal and into the scrotum.

Abdominal pressure appears to be important for the transit of the testis through the inguinal canal and into the scrotum.