Embryogenesis

Question 1

What is differentiation?

Answer 1

A group of unspecialized cells that develop into recgonizable groups with common functions

Question 2

What does the Endoderm contain?

Answer 2

1. The digestive system
2. Lungs
3. Endocrine System

Question 3

What does the Mesdoderm Contain?

Answer 3

1. Muscle
2. Skeleton
3. Cardiovascular
4. Reproductive system

Question 4

What does the Ectoderm contain?

Answer 4

1. Nervous system
2. Skin
3. Hair

Question 5

What is the male in sex determination? What is the determination based off of? What species does this apply to?

Answer 5

1. The male is a heterogametic sex
2. The sperm determines the sex of the embryo (X,Y)
3. Mammals

Question 6

What is the female in sex determination? What species does this apply to? What are the sex determining letters for these species?

Answer 6

1. The female is the heterogametic sex
2. Applies to birds and some reptiles
3. ZW=Females , ZZ=Male

Question 7

What can determine the sex in reptiles such as turtles, and crocodiles? Which steroid hormone is different in reptiles?

Answer 7

1. The environment is what determines the sex
2. Estradiol is what works differently in reptiles compared to other animals.

Question 8

What does the primordial germ do to initiate sex determination?

Answer 8

Primodrial germ cell migrates to the genital ridge during embryo development and then resides on the bipotential gonad

Question 9

What can the Bipotential gonad turn into?

Answer 9

It can develop into ovaries or testis

Question 10

What occurs during the trimester?

Answer 10

1. Migration of primodrial germ cells from yolk sac
2. Sex cords develop in gonad, paramesonephric ducts develop
3. Sex evident from structures

Question 11

What occurs during the time that the first trimester goes into the second trimester?

Answer 11

1. Development of male/female ducts and testes/ovaries (depending on the sex)

Question 12

What occurs during exclusively to the 2nd Trimester? Which species of animal contains testicular descent during the second trimester?

Answer 12

1. The formation of a broad ligament
2. Bull & Ram

Question 13

What occurs during the third trimester and for which animals?

Answer 13

1. Testicular descent
2. Colt, Boar & Human

Question 14

What is the Mesonephric ducts? What is another name for them?

Answer 14

1. They are part of the male tract
2. Another name for them are the Wolffian duct

Question 15

What are the Paramesonephric ducts? What is another name for them? What must happen to them in order for the male to form?

Answer 15

1. They are part of the female tract
2. Another name is the Müllerian ducts
3. They must regress in order to make the male

Question 16

What is the indicator that tells the mullerian ducts to regress in order to form the male reproductive tract?

Answer 16

The Y chromosome is what regresses the Muellerian duct

Question 17

What does the y chromosome contain in itself that retracts the mullerian duct? When is it normally expressed? What does it initiate?

Answer 17

1. Y chromosome contains a gene called the sex determing region which is called SRY
2. It is expressed in the early embryo
3. It initiates the development of the male reproductive tract.

Question 18

What can produce sertoli cells and what do they secerete?

Answer 18

1. Testis development produces sertoli cells
2. Secretes anti-Mullerian hormone (AMH) and dihydrotestosterone

Question 19

What is the specific hormone that regresses the Mullerian (paramesonephric) ducts?

Answer 19

AMH or the anti-Mullerian hormone

Question 20

What does the Dihydrotestosterone do or what is it responsible for?

Answer 20

Responsible for the penis, scrotum, and accessory sex gland formation

Question 21

What occurs when a chromosomal pair of XX are together?

Answer 21

One of the X chromosomes will become inactivated

Question 22

How does the process of the female occur during gestation?

Answer 22

Starts with
1. No SRY
2. Ovaries Develop
3. No AMH
4. Paramesonephric ducts become the oviducts, uterus, cervix, and part of the vagina
5. Complete female tract

Question 23

How does the process of the male occur during gestation?

Answer 23

Starts with
1. Sex determining region Y (SRY)
2. Testes develop
3. Sertoli cells secrete anti-müllerian hormone (AMH)
At this point AMH does 2 things
* AMH causes leydig cells to differentiate
* Causes degeneration of the paramesonephric duct
1. After leydig cells differentiate they produce testosterone and Dihydrotestosterone
2. Testetosterone Develops the male duct system
3. Dihydrotestosterone Develops the penis, scrotum and accessory gland

Question 24

What is the process of the formation of the female tract using paramesonephric ducts?

Answer 24

1.The paramesonephric ducts fuse to form the cervix and the uterine body
2. The cervix and vagina continue to form
3. Definitive cervix, vagina and vagina vestibule form along with the uterine horns and body

Question 25

What occurs to the gubernaculum when the testers are formed?

Answer 25

The gubernaculum must grow and then shrink

Question 26

What occurs in the Transabdonimal phase?

Answer 26

1. The cells of the peritoneum bind the gubernaculum to allow vaginal process to form 2. The distal gubernaculum grown into the scrotal region

Question 27

What occurs in the Inguinal-Scrotal phase?

Answer 27

1. The gubernaculum penetrates the inguinal ring 2. Rapid grwoth of the distal gubernaculum forces testicular descent.

Question 28

What occurs after the iguinal-scrotal phase?

Answer 28

The gubernaculum then shrinks, driving testis into the scrotum

Question 29

What occurs after testis are in the scrotum?

Answer 29

Continuied gubernaculum shrinkage encapsulates each teste by the visceral vaginal tunic and the outer layer (pariental)

Question 30

When does the descent of testis occur for the bull, ram, boar, human and stallion?

Answer 30

1.Bull, Ram: mid-gestation 2.Boar, Human: Last quarter of gestation 3.Stallion: Just before or after birth

Question 31

What is a boar inguinal herniation?

Answer 31

It is when the intestine reaches the testis and it applies pressure

Question 32

What occurs to a twin heifer when it is born with a twin bull?

Answer 32

1. The female becomes sterile because it is exposed to testoesterone & AMH (usually makes female almost always sterile) 2. Blocks the formation of the female tract (no cervix, uterus, oviducts, and ovaries) 3. The vulva and caudal vagina still remain 4. Testosterone programs to look/act "male-like"

Question 33

What are freemartin heifer normally?

Answer 33

They are normall chimeric

Question 34

In embryogenesis what are chimeras? How rare are they naturally?

Answer 34

1. They are individuals with more than one population of cells from multiple zygotes 2. They are Rare

Question 35

What are mozare cats normally?

Answer 35

1. They are almost always female 2. Mostly Sterile

Question 36

How are hybrids formed? How is there fertility?

Answer 36

1. Hybrids are produced by natural mating between species 2. They can be fertile or infertile