Lec: 64 Early Embryogenesis

Question 1

Embryo

Answer 1

until the end of the 8th week

Question 2

Zygote

Answer 2

2-cell stage to morula

Question 3

Morula

Answer 3

day 3

Question 4

Blastocyst

Answer 4

days 4 - 6

Question 5

Fetus

Answer 5

week 9 to birth

Question 6

Ovulation

Answer 6

• Completes first meiotic division.
• Arrests at metaphase of meiosis II.
• Oocyte has a haploid number (1n) of chromosomes but is diploid in DNA content (2d).
• It is 23, X.

Question 7

Uterine Tube Mucosa

Answer 7

• Peg cells secrete nutritive material for ovum.

- Ciliated cells move fluid down the tube.

Question 8

Ovum viable in female reproductive tract

Answer 8

24 hours

Question 9

Sperm

Answer 9

• Consists of a nucleus and a tail

* Contains a haploid number (1n) of chromosomes and is haploid in DNA content (1d). 23, X or 23, Y

Question 10

Sperm viability:

Answer 10

24-48 hrs

Question 11

Epididymis

Answer 11

Sperm:

• Gain motility
• Storage

Question 12

Fertilization

Answer 12

From contact to mingling of genetic material
Takes 24 hours
1. Penetration of Corona Radiata
2. Penetration of Zona Pellucida
3.Ovum Sperm Membrane Fusion
4. Male Pronucleus forms
5. Pronuclei replicate their DNA.
6. Pronuclear membranes degenerate
7. Chromosomes line up for mitosis and first cleavage

Question 13

Notochord

Answer 13

• Cord of cells that is located between the ectoderm and endoderm: from primitive node/pit to the region of the oropharyngeal membrane (consists of two layers: ectoderm and endoderm)
• Functions as the primary signaling center in the early embryo
• Induces the overlying ectoderm to thicken and form the neural plate (primordium of CNS)