Development

Question 1

What are the layers of the blastocyst?

Answer 1

Inner cell mass (embryoblast)
Trophoblast (placenta)
Blastocoele (fluid-filled space)

Question 2

How are cell fates specified during development?

Answer 2

short and long range signalling (contact-dependent, paracrine, endocrine, or synaptic)

Question 3

What differentiates embryo from a fetus?

Answer 3

embryo - no anatomical form that can be recognized as a specific species
fetus - recognizable (marked by placentation development)

Question 4

Which organized layer becomes the repro tract (vagina/vestibule, penis/clitoris), mammary glands, and nervous system?

Answer 4

Ectoderm

Question 5

What does mesoderm develop to?

Answer 5

Gonads (testes and ovaries), uterus, cervix, cranial vagina, epididymis, and ductus deferens

Question 6

What organized layer gives rise to the endocrine system?

Answer 6

Endoderm

Question 7

What animal spends the longest time within the embryonic portion of gestation?

Answer 7

dogs (46-50%)

Question 8

Where does organogenesis occur?

Answer 8

outside the embryo; palpation before 42d can damage the fetus

Question 9

What is the rare and congenital, but not heritable, disorder that causes exposure of abdominal viscera due to a fissure, limb anylosis, and spinal inversion?

Answer 9

Schistosomus reflexus (developmental abnormality)

Question 10

What disorder is heritable during the periparturient period?

Answer 10

Vaginal prolapse (cull the cow)

Question 11

Differentiate chimera and mosaic

Answer 11

chimera - two different zygotes (freemartin)

mosaic - two different cell lines from the same zygote

Question 12

What 3 stages does sexual differentiation rely on?

Answer 12

Chromosomal sex (karyotype), gonadal sex, and phenotypic sex

Question 13

What are the key players of sexual determination?

Answer 13

Testis Determining Factor (TDF) and Sex-Determining region Y (SRY) on the Y chromosome (cause the development of testes to produce testosterone early in the embryonic development), Anti-Mullerian hormone (AMH from sertoli cells prevents development of ovaries) and Dihydrotestosterone (testosterone from leydig cells forms DHT)

Question 14

What makes an indifferent gonad develop into an ovary?

Answer 14

By default (no Y chromosome), the lack of AMH, T2, and DHT results in the regression of mesonephric ducts and the paramesopnehric ducts differentiate into oviducts, uterus, and cranial 1/3 of vagina

Question 15

What cell line does different embryological tissue originate?

Answer 15

Ectoderm