Lecture 4 - Embryogenesis

Question 1

Embryonic Germ Layers

Answer 1

1. Endoderm
2. Mesoderm
3. Ectoderm

Question 2

embryonic origins from the ectoderm

Answer 2

Reproductive Tract
- external vagina or penile sheath
- clitoris or penis

Nervous System
- hypothalamus
- pituitary

Oral cavity

Nasal cavity

Question 3

embryonic origins from the mesoderm

Answer 3

Repro System
- gonads
- uterus, cervix, internal vagina
- epididymus, ductus, deferens, accessory sex glands

Urinary System
Skeletal System
Blood Vessles
Muscle

Question 4

embryonic origins from the endoderm

Answer 4

Digestive System
Respiratory System
Glandular Systems

Question 5

embryonic development of the reproductive system

Answer 5

1. development of hypothalamic-hypophyseal systems
2. primordial germ cells migrate from yolk sac
3. sex cord development in the gonad and mesonephric renal system regression/transformation
4. sexual differentiation
5. development of female tract and ovaries
6. formation of broad ligament

Question 6

Gestation period of cattle

Answer 6

280-290 days

Question 7

gestation period of sheep

Answer 7

145-150 days

Question 8

gestation period of swine

Answer 8

114 days

Question 9

gestation period of dog

Answer 9

60-65 days

Question 10

gestation period of cat

Answer 10

63-67 days

Question 11

Why are the anterior and posterior pituitary so different?

Answer 11

• posterior originates from infundibulum coming from the 3rd ventricle (neural tissue)
• anterior originates from Ratheke’s pouch which was apart of the embryonic mouth (glandular)

Question 12

Why do germ cells migrate into the gonadal ride of the embryo?

Answer 12

to form any tissue type

Question 13

What does the repro system develop in close proximity to?

Answer 13

renal system

Question 14

Three embryonic renal systems

Answer 14

1. pronephroes
2. mesonephros
3. metanephros

Question 15

Pronephros

Answer 15

most primitive form of kidney found in developing embryo- limited fxn and eventually degenerates

Question 16

Mesonephros

Answer 16

• early kidneys of emrbyo regresses and gives way to metanephros
• remnants of regressing mesonephric renal system become portions of repro tract

Question 17

What do remnants of regressing mesonephric renal system become?

Answer 17

1. mesonephric ducts = male repro tract
2. paramesonephric ducts = female repro tract

Question 18

Metanephros

Answer 18

final renal system that becomes fxning kidneys

Question 19

Sex determining factors

Answer 19

Female
- no TDF
- ovaries develop
- no AMH
- Paramesonephric duct becomes the oviducts, uterus, cervix and part of the vagina
- complete female tract

Question 20

Where is AMH secreted from

Answer 20

sertoli cells of the testis

Question 21

What female organ does the paramesonephros duct turn into?

Answer 21

• oviducts, uterus, cervix, cranial vagina

Question 22

What female organ does the mesonephros duct turn into

Answer 22

regresses

Question 23

What female organ does the urogenital sinus turn into?

Answer 23

urethra, caudal vagina

Question 24

Gonadal dysgenesis

Answer 24

• incomplete development of gonads
• ex. Turner syndrome; only 1 X chromosome so ovary doesn’t fully develop

Question 25

Hermmaphrodites

Answer 25

-have both ovarian and testicular tissues
- ex. FREEMARTIN