Embryology

Question 1

what is the main embryonic layer that contributes to the kidney?

Answer 1

mesoderm

Question 2

urogenital ridges

Answer 2

thickened portion of the intermediate mesoderm, lateral side becomes the nephrogenic ridge, medial side becomes the gonadal ridge

Question 3

pronephros

Answer 3

primitive kidney that is non-functional in mammals and disappears over time

Question 4

mesonephros

Answer 4

intermediate kidney in the thoracolumbar region that is functional in the fetus and disappears over time

Question 5

metanephros

Answer 5

definitive, permanent kidney

Question 6

how does the kidney develop from the metanephros?

Answer 6

• ureteric bud elongates until it reaches the metanephric caps
• expanded cranial portion becomes the renal pelvis or calcyies
• metanephric caps develop into nephrons

Question 7

cloaca

Answer 7

expanded, caudal part of the hindgut caudal to the origin of the allantois

Question 8

urorectal septum

Answer 8

wedge of the mesoderm that grows down between the hindgut and the allantois

divides the cloaca into dorsal and ventral portions

Question 8

allantois

Answer 8

embryonic extension of the urinary bladder that develops into the urachus

Question 9

2 parts of the cloaca

Answer 9

ventral
- urogenital sinus and membrane

dorsal
- anorectal canal
- anal membrane

Question 10

3 divisions of the urogenital sinus

Answer 10

1. cranial: develops into the bladder
2. middle (pelvic) develops into prostate and prostatic urethra or caudal vagina
3. caudal (phallic): develops into penile urethra, BUG, vaginal vestibule

Question 11

what causes the indifferent gonad to develop into either testes or ovaries?

Answer 11

SRY gene on the Y chromosome– codes for testis - determining factor that promotes development of testes

Question 11

indifferent gonad

Answer 11

gonad precursor that develops from the intermediate mesoderm (urogenital ridge) that is neither ovary or testes yet

Question 12

once testes are formed, what causes further development of the rest of the male reproductive tract?

Answer 12

1. mullerian inhibiting factor (sertoli cells): suppresses the paramesonephric duct, preventing the development of uterine tubes and uterus
2. testosterone (leydig cells) –stimulate the development of external genitalia and the mesonephric duct (develops into ductus deferens and epididymis

Question 13

once the ovaries are formed, what causes further development of the rest of the female reproductive tract?

Answer 13

estrogens!!

• stimulate development of the paramesonephric duct (uterine tube, uterus and cranial vagina)
• stimulates development of female external genitalia

Question 14

3 components of the indifferent gonad

Answer 14

1. gonadal ridge (intermediate mesoderm) : gives rise to the stroma of the testes or ovary
2. coelomic epithelium (mesoderm) : forms primitive sex (epithelial) cords (serve as a nest for germ cells)
3. primordial germ cells (endoderm) : from the yolk sac, migrate to the gonadal ridge and lie in between primitive sex cords

Question 15

teratoma

Answer 15

neoplasm of the testis or ovary containing multiple tissues from other sites in the body due to improper migration of germ cells to extragonadal regions

Question 16

in males, the epithelial cords develop into the __ and __

Answer 16

seminiferous tubules and rete testes

Question 17

in females, the epithelial cords develop into __ that are later replaced by the __

Answer 17

primary medullary cords, stroma of the ovary

Question 18

in females the coelemic epithelium develops into __ that develop into __

Answer 18

ovary cords, primary follicles

Question 19

3 phases of descent of the testes into the scrotum

Answer 19

1. regression of the cranial gonadal ligament to release testis from abdominal wall
2. transabdominal descent guided by the gubernaculum
3. transinguinal descent guided by gubernaculum and testosterone

Question 20

in what species do ovaries migrate caudally? where do they end up?

Answer 20

ruminants and pigs – migrate close to the pelvic inlet

Question 21

Remnants of the mesonephric duct in females

Answer 21

Gartner’s duct - small pieces of tissue on each side of the floor of the vagina that are not normally seen but can be enlarge and develop cysts

Question 22

How is the vagina formed during development?

Answer 22

• fused Müllerian ducts at the caudal end of the mullerian tubercle
• mullerian tubercle grows and fuses with the vaginal plate forming the vagina

Question 23

Uterus masculinus

Answer 23

Remnant of the mullerian (paramesonephric) duct present in the genital fold of males between the Ducati’s deferents

Question 24

2 components of indifferent external genitalia

Answer 24

1. Cloacal fold - bilateral swellings on either side of the cloacal membrane
2. Genital tubercle - fusion of the cloacal folds at the ventral comissure

Question 25

In indifferent external genitalia, the cloacal membrane divides into __ and __

Answer 25

anal membrane (ruptures to form anus) and the urogenital membrane

Question 26

Cloacal folds divide into __ and __ folds

Answer 26

Anal and urogenital

Question 27

Labioscrotal swellings

Answer 27

pair of elevations of tissue on either side of the urethral folds in the indifferent genitalia

Question 28

In females, the urethral (urogenital) folds become what structures?

Answer 28

labia of the vulva and genital tubercle

Question 29

In males the urogenital folds develop into the __

Answer 29

penis

Question 30

In males the scrotal swellings __ and develop into the __

Answer 30

fuse, scrotum

Question 31

true hermaphrodites

Answer 31

rare individuals who have both ovarian and testicular tissue in their bodies; external genitals may be male, female or both

Question 32

Pseudohermaphrodites

Answer 32

Individuals with gonads of one sex with the external genitalia of the opposite sex