Chapter 3 - Embryogenesis and Development

Question 1

Explained the two mechanisms that twins can occur

Answer 1

1) Dizygotic / fraternal twins :
- two different eggs are fertilized
- both zygotes implant into uterine wall
- no more genetically similar than siblings

2) monozygotic / identical twins:
- single zygote splits into two

Question 2

What is cleavage? (No joke)

Answer 2

When a zygote undergoes rapid mitosis cell divisions

Question 3

After the zygote is cleaved it becomes a ________.

Answer 3

Morula

• same size but solid ball of cells

Question 4

What is a blastocyst?

Answer 4

A hollow ball of cells with a fluid filled inner cavity (formed from the morula)

Question 5

What is implantation?

Answer 5

When the blastula moves through the Fallopian tube to the uterus where it burrows into the endometrium

Question 6

After implantation comes _____________. What happens in this process?

Answer 6

Gastrulation: génération of three distinct cell layers

Gastrula: when the blastula forms a hollow tube

Question 7

List three primary germ layers , what do they consist of?

Answer 7

Ectoderm: outermost layer

• integument (epidermis, hair nails, epithelia of nose mouth and lower anal canal
• lens of eye
• NERVOUS SYSTEM
• inner ear

Mesoderm: several different systems

• musculoskeletal, circ, extcretory systems
• gonads
• muscular and connective tissue layers of digestive and respiratory systems + adrenal cortex

Endoderm:

• forms epithelial linings of digestive and respiratory tracts (including lungs)
• pancreas, thyroid, bladder, distal urinary tracks, parts of liver

Question 8

Where does the notochord form from?

Answer 8

Mesoderm