T4: Sex Differentiation

Question 1

what are the seven sexual differentiation items

Answer 1

genetic, gonadal, internal genitalia, external genitalia, hypothalamic, secondary sex traits , psychological, behavioral

Question 2

describe the differences for genetic sex

Answer 2

mammals
-male XY (heterogametic)
-female XX (homogametic)

birds
-males ZZ (homo)
-females ZW (hetero)

Question 3

what is the difference with reptiles and genotype

Answer 3

have no heteromorphic pair, sex is determined by temperature

Question 4

why can female cats be calico

Answer 4

-one of the X’s is inactivated (tortie)
-appears as the Barr body in the somatic cells of females

Question 5

what are some abnormal gene types

Answer 5

XXY: sterile male, Klinefelter syndrome
XO “missing” : turners syndrome, sterile female
-happens around the time of oogenesis or spermatogenesis

Question 6

What is the Sry gene

Answer 6

sry= sex-determining region of the Y chromosome
Sry is the gene on the Y chromosome responsible for male development
-production of TDF or SRY protein (which causes the indifferent gonad to be organized as a testes)

Question 7

what can be used to accurately sex embryos

Answer 7

SRY gene

Question 8

describe the male developing process

Answer 8

-XY, TDF, or SRY protein is present
-testes develop
-Sertoli cells secrete anti-Mullerian hormone (AMH)
-(degeneration of paramesonephric duct)
-AMH causes Leydig cells to differentiate to
1. testosterone- development of male duct system
2.Dihydrotesterone- development of penis, scrotum and accessory sex glands

Question 9

describe the female developing process

Answer 9

-XX, no TDF
-ovaries develop, no AMH
-paramesonephric ducts become the oviducts, uterus, cervix, and part of the vagina
-complete female tract

Question 10

what layer does the repro tract come from

Answer 10

mesoderm

Question 11

describe the development of the gonads

Answer 11

• bipotential (undifferentiated gonad) develops from the gonadal *gential ridge
  -PGCs (primordial germ cells) migrate to and inhabit gonadal ridge
  -chemotactic agent (telopheron) stimulates movement to genital ridge

Question 12

describe the development of the gonads part 2

Answer 12

-undifferentiated gonad will become either testis or ovary
-PGCs will become either spermatogonia or oogonia

Question 13

describe the role of primordial germ cells

Answer 13

-wander in a amoeboid manner from the primary ectoderm into the yolk sac wall and collect near the base of the allantois and hindgut

Question 14

PGCs vs somatic cells

Answer 14

-larger (12-20 microns)
-large round nuclei containing prominent nucleoli
-pseudopodia
-secrete lytic enzymes
-migrate by ameboid movement
-use telopheron to help migrate to the gonad

Question 15

describe how the ducts develop for male and females

Answer 15

a starting conceptus has both male and female components
starting: gonad, mesonephros, Mullerian duct, wolffian duct, urogenital sinus

female: (mullerian duct) develops from the paramesonephric system

Male: (wolffian duct) develops from the mesonephric system

Question 16

describe how the testis are formed

Answer 16

1. SRY gene is expressed in cell precursors in XY gonad, sertoli cells differentiate, sex cords persist in development to organize a testis
2. undifferentiated sex cords align with rete tubules
   -mesonephric tubules have not interconnected with rete tubules
   -surface of undifferentiated gonad covered with albuginea
   -paramesonephric duct present but serves no function

Question 17

describe how the testis formed part 2

Answer 17

-rete and mesonephric tubules now interconnected to provide continuity b/w undifferentiated sex cords now developing into epithelial cords
-epithelial cords will become seminiferous tubules
-paramesonephric duct regressing due to AMH produced by setoli cells of developing testis

Question 18

describe how the testis are formed part 3

Answer 18

-seminiferous tubules are now formed
-Rete testis and efferent ducts continuous
-mesonephric duct becoming epididymis
-parames duct has regressed

Question 19

describe how the female repro system develops

Answer 19

-paramesonephric and mesonephric ducts intact
-coelomic epithelium will become ovarian cortex
-remnants of mesonephric tubules do not make contact with rete tubules

Question 20

describe how the female repro system develops pt 2

Answer 20

-rete testis have disappeared and paramesonphric duct continues to develop and enlarge
-sex cords regress but primitive germ cells do not
-primordial follicles begin to develop
-paramesonephric ducts continue to develop and mesonephric ducts continue to regress

Question 21

escribe how the female repro system develops pt 3

Answer 21

-distinct clusters of follicles surrounded by a single layer of cells develop at periphery of ovary
-sex cords have completely disappeared
-ovary has distinct cortex (region containing primordial oocytes) and medulla
-mesonephric tubules and ducts have regressed

Question 22

how do the testes drop (part one)

Answer 22

-before they lie retroperitoneal and are attached caudally to the gubernaculum
-cells of the peritoneum infiltrate the gubernaculum in the inguinal region and form a junction and form a junction w/ it
-allows vaginal process to form as the distal gubernaculum grows towards and into the scrotal region

-after the gubernaculum penetrates the inguinal ring, there is rapid growth.
-this growth is the force for mechanically pulling the testes into the inguinal canal

Question 23

how do the testes drop (part two)

Answer 23

• once testes are in the inguinal canal, they are pulled through as gubernaculum regresses
  -gubernaculum regresses pulling testes deeper into scrotum and causing encapsulation by visceral vaginal tunic
  -inner (visceral) layer covers testis and outer (parietal) layer lines scrotum

Question 24

what are the times of testicular decent for the species

Answer 24

bull: 1/2 gestation
Ram: 1/2 gestation
Boar: last 1/4 gestation
stallion: just before or just after birth
man: 7th month of gestation

Question 25

what are the potential problems associated with testicular descent

Answer 25

-cryptochidism: failure of testicular descent, may be unilateral or bilateral
-scrotal hernia: passage of intestines into scrotum (often removed from herd)

Question 26

what species are abnormalities common

Answer 26

-may occur in any species but is especially common in boars

Question 27

what is going on in the first trimester

Answer 27

-migration of primordial germ cells from yolk sac
-sex cords develop in gonad, paramesonephric ducts develop
-sex evident from structures are visual

Question 28

what happens in the second trimester (bull and ram)

Answer 28

-development of make ducts and testes or development of female ducts and ovaries
-formation of broad ligament

Question 29

what happens in the 3rd trimester

Answer 29

-testicular descent
then parturition