4 - Female Embryogenesis

Question 1

Three embryonic germ layers

Answer 1

Endoderm, mesoderm, ectoderm

Question 2

What is developed from the endoderm?

Answer 2

Digestive system, lungs, endocrine system

Question 3

What is developed from the mesoderm

Answer 3

Muscle, skeleton, cardiovascular, reproductive system

Question 4

What is developed from the ectoderm

Answer 4

Nervous system, skin, hair

Question 5

What is the ICM?

Answer 5

Inner cell mass
Mesoderm

Question 6

What part of the reproductive tract is developed by the ectoderm? What other system?

Answer 6

External vagina or penile sheath
Clitoris or penis

Nervous system: hypothalamus, anterior & posterior pituitary

Oral and nasal cavities

Question 7

What part of the reproductive tract develops from the mesoderm? What other systems?

Answer 7

Gonads, uterus, cervix, internal vagina
Epididymus, ductus deferens, accessory sex glands in males

Urinary, skeletal systems
Blood vessels, muscle

Question 8

What systems develop from the endoderm?

Answer 8

Digestive, respiratory, glandular

Question 9

Six steps of female embryonic development

Answer 9

1. Development of hypothalamic-hypophyseal systems
2. Migration of primordial germ cells from the yolk sac
3. Sex cords develop in the gonad & mesonephric renal system transformation
4. Sexual differentiation (Sex from structure)
5. Development of female tract & ovaries
6. Formation of broad ligament

Question 10

Average gestation period for cattle, sheep, swine, dogs and cats

Answer 10

Cattle = ~280-290 days

Sheep = ~145-150 days

Swine = 3 months, 3 weeks, 3 days

Dog = 60-65 days

Cat = 63-67 days

Question 11

How does the development of the hypothalamic-hypophyseal system occur?

Answer 11

Infundibulum hooks around Rathke’s pouch to become the pituitary gland

Infundibulum becomes posterior, Rathke’s pouch is anterior
= diff embryonic origins

Question 12

What is migration of primordial germ cells?

Answer 12

Primordial germ cells are gametes that become oocytes during puberty
Migrate from yolk sac into genital region (gonadal ridge that eventually becomes the ovary)

Question 13

Three stages of the embryonic renal system

Answer 13

1. Pronephros
2. Mesonephros
3. Metanephros

Question 14

What is the pronephros

Answer 14

Most primitive form of the kidney found in developing embryo
Limited function, eventually degenerates

Question 15

What is the mesonephros

Answer 15

Early kidneys of mammalian embryo; regresses to give way to Metanephros

Question 16

The remnants of the mesonephros become what?

Answer 16

Portions of the reproductive tract:

Mesonephric ducts (Wolffian ducts) = male repro tract
Paramesonephric ducts (Mullerian ducts) = female repro tract

Question 17

What is the metanephros

Answer 17

Final renal system that eventually becomes the functioning kidneys in adult animal

Question 18

Male sex determination is dependent on…

Answer 18

Testis determining factor (TDF) which develops testes
Testes sertoli cells secrete anti-mullerian hormone which degenerates the paramesonephric duct and causes leydig cells to differentiate, leading to testosterone production and development of repro syste

Question 19

How does female sex determination work?

Answer 19

No testis determine factor -> ovaries develop -> no anti-mullerian hormone -> paramesonephric ducts become the oviducts, uterus, cervix and vagina

Question 20

The paramesonephric ducts become what parts of the female repro tract? Why are there different tissues in the cranial and caudal vaginas?

Answer 20

Para form oviducts, uterine horn, cervix and cranial vagina

Caudal vagina develops from the urogenital sinus

Question 21

Gonad in male vs female

Answer 21

Male = testis
Female = ovary

Question 22

What does the mesonephros duct become in males?

Answer 22

Epididymis, ductus deferens

Question 23

What does the urogenital sinus become in males vs females?

Answer 23

Male = urethra, male accessory sex glands

Female = urethra, caudal vagina - vestibule

Question 24

Slide 24**

Answer 24

Important

Question 25

Describe broad ligament formation

Answer 25

Repro tract begins to drop into the body cavity as BL (mesometrium) forms
Tract is then suspended in the abdominal cavity

Question 26

Two kinds of anomalies during sexual differentiation in females and give example

Answer 26

Gonadal dysgenesis: incomplete development of gonads
e.g. Turner syndrome (only one X chromosome, one ovary does not fully develop)

Hermaphrodites: both ovarian and testicular tissues
e.g. Freemartin

Question 27

Three causes of Hermaphrodism

Answer 27

Sex chromosome translocation
Mutation of sex linked genes
Hormonal exposure in utero (Freemartin)

Question 28

What is freemartinism? In calves?

Answer 28

In female calves of heterosexual twins, embryonic membranes fuse prior to organ development so both calves share the same cotyledons & blood supply mixes
Female is exposed to testes determining factor (TDF) and anti-mullerian hormone (AMH) from male and development of fem repro tract from paramesonephros is inhibited

Occurs 90% of the time in hetero twins

Question 29

Characteristics of a freemartin calf

Answer 29

• Incomplete development of female tract
• vestigial ovarian formation
• no estradiol production
• abnormally high testosterone
• bull-like behaviour and appearance
• infertile