ILS_Practical_4

Question 1

Week 3

Answer 1

• brain, spinal cord, heart

Question 2

Week 4/5

Answer 2

• limb development

Question 3

Week 6

Answer 3

• ears, palate
• eyes

Question 4

Week 7

Answer 4

• ears, palate
• teeth
• external genetelia

Question 5

Ectoderm

Answer 5

1. epidermis of skin & derivatives (sweat glands, hair follices)
2. lining of mouth and rectum
3. epidermal sensory receptors
4. cornea & lens
5. nervous system
6. adrenal medulla
7. tooth enamel
8. pineal and pituitary

Question 6

Mesoderm

Answer 6

1. notocord
2. skeletal muscle
3. muscular lining
4. excretory
5. circular & lymphatic
6. reproductive germ cells
7. dermis of skin
8. lining of body cavities
9. adrenal cortex

Question 7

Endoderm

Answer 7

1. lining of digestive tract
2. lining of respiratory
3. lining of urethra, bladder, reprductive system
4. liver
5. pancreus
6. thymus
7. thyriod glands

Question 8

Week 4 Development

Answer 8

1. limbs appear

Question 9

Week 3 Development

Answer 9

• trilaminar germ disc
• Paraxial mesoderm that forms along the notochord and neural tube divides and forms paired cuboidal bodies called somites starting in week three.
  • Somites develop in a caudal direction = rise to most of the axial skeleton, skeletal muscles, dermis
• development: brain, spinal chord, heart

1. •The dorsal germinal layer becomes the ectoblast/-derm.
2. •The middle germinal layer (3rd germinal layer) becomes the mesoblast/-derm.
3. •The ventral germinal layer receives the name endoblast/-derm.

Question 10

Week 2 Development

Answer 10

trophoblast → syncytiotrophoblast and the cytotrophoblast, as well as the extraembryonic mesoderm. The ectoderm is a derivative of the epiblast.

(bilaminar germ disc):

1. Epiblast is the more dorsal mass. It will give rise to all three germ layers of the trilaminar embryonic disc in the third week.
2. Hypoblast is the layer of cells located ventral to the epiblast and which will contribute to the formation of the primary yolk sac.

Question 11

β-HCG

Answer 11

• detectable in maternal serum only after the blastocyst successfully implants.
• implant is 5-6 after ovulatio
• 6 days after ovulation, significant hCG secretion from the blastocyst begins.
• detectable about 8 days after ovulation​