Embryology: Principles of medical embryology

Question 1

Gamete

Answer 1

mature haploid male or female germ cell able to unite with another of the opposite sex in sexual reproduction to form a zygote

Question 2

Embryonic period

Answer 2

3-8 weeks in humans

Question 3

Teratogen

Answer 3

cause irreversible, deleterious structural malformations in fetuses

Question 4

Pregnancy week 0-3

Answer 4

conceptous/embryo

Question 5

Pregnancy week 3-8

Answer 5

Embryonic period
(highest risk)

Question 6

Pregnancy week 9-40

Answer 6

Foetal period

Question 7

Phases of embryogenesis (6 GFC GFO)

Answer 7

1. Gametogenesis
2. Fertilisation
3. Clevage
4. Gastrulation
5. Formation of body plan (embryonic folding)
6. Organogenesis

Question 8

1. Gametogenesis

Answer 8

• Formation of gametes
• 23 chromosomes (haploid)

Question 9

What is spermatogenesis in gametogenesis?

Answer 9

• Formation of male gametes
• Occurs at puberty, continues throughout life
• outcome: 22+X, 22+Y

Question 10

What is oogenesis in gametogenesis?

Answer 10

• formation of female gametes
• Primary oocytes begin meiosis by week 28-30 but arrest in prophase until puberty

Question 11

2. Fertilisation

Answer 11

Union of gametes - fusion of sperm and oocyte to form zygote.

Question 12

3. Cleavage

Answer 12

• Period of rapid mitotic cell division
• No increase in size!
• Formation of morula then blastocyst (days 1-4)

Question 13

Each cell in cleavage is known as…

Answer 13

Blastomere

Question 14

4. Gastrulation

Answer 14

• Formation of germ layers
• Body axis established

Question 15

What are the 3 germ layers established in Gastrulation?

Answer 15

1. Ectoderm - skin
2. Mesoderm - muscle tissue
3. Endoderm - GI tract

Question 16

5. Embryonic folding

Answer 16

Formation of body plan
“tube within tube” - check photo NOTION

Question 17

6. Organogenesis

Answer 17

• Formation of organs and organ systems,
• Basis in place by end of embryonic period, development continues through fetal period

Question 18

7. Fetal period

Answer 18

• From week 9 until birth
• Overt sexual differentiation
• Bone laid down, connections made in CNS

Question 19

When does growth and weight gain take place in fetal period?

Answer 19

growth - during 2nd trimester
weight gain during 3rd trimester

Question 20

Primary processes of embryonic development: differentiation

Answer 20

specialisation

Question 21

Primary processes of embryonic development: cell attachment

Answer 21

formation of tissues

Question 22

Primary processes of embryonic development: apoptosis

Answer 22

programmed cell death

Question 23

Primary processes of embryonic development: Induction

Answer 23

Ability of one cell to cause another to differentiate

Question 24

Primary processes of embryonic development: cell migration

Answer 24

movement from one location to another

Question 25

Secondary processes of embryonic development

Answer 25

Axis formation/ polarity

Question 26

What are *genetic* factors responsible for regulation of embryonic development?

Answer 26

gene expression regulated in time and space

Question 27

What are *epigenetic* factors responsible for regulation of embryonic development?

Answer 27

Environmental influences, they have impact on which copy of gene is expressed

Question 28

What is Trisomy 21 (Down syndrome)?

Answer 28

Additional copy of chromosome 21

Question 29

What causes Trimosy 21 (Down syndrome)

Answer 29

Caused by nondisjunction - separation of chromosomes not occurred