Embryology - Principles of Medical Embryology

Question 1

How long is in utero human development?

Answer 1

9 months (38-40 weeks)

Question 2

What are weeks 0-3 called in human gestation?

Answer 2

conceptus/embryo

Question 3

What are weeks 3-8 called in human gestation?

Answer 3

embryonic period

Question 4

What are weeks 9-40 called in human gestation?

Answer 4

fetal period

Question 5

How many stages of embryogenesis are there?

Answer 5

6 (gametogenesis, fertilisation, cleavage, gastrulation, formation of a body plan and organogenesis)

Question 6

What is the chromosome complement of a gamete?

Answer 6

23 chromosomes (half of a typical somatic cell)

Question 7

What are the two stages of gametogenesis?

Answer 7

Mitosis and meiosis

Question 8

What does mitosis and meiosis lead to?

Answer 8

genetic variation

Question 9

When does spermatogenesis occur?

Answer 9

At puberty and continues throughout life

Question 10

How long does each cycle of spermatogenesis take?

Answer 10

around 64 days

Question 11

What is the average production rate of sperm?

Answer 11

6.5 million sperm per gram of testicular tissue per day (decreases with age)

Question 12

What is the outcome of spermatogenesis on the chromosomes in sperm ?

Answer 12

either 22 + X (will create female) or 22 + Y (will create male)

Question 13

When does oogenesis start and end?

Answer 13

Starts in development and ends at menopause

Question 14

When do primary oocytes begin meiosis?

Answer 14

week 28-30 but it is arrested in prophase until puberty

Question 15

When is reproductive life span determined in females?

Answer 15

In foetal life ie dependent on number of ova produced during foetal development

Question 16

What causes Trisomy 21 (Down Syndrome)?

Answer 16

An additional copy of chromosome 21 caused by non disjunction

Question 17

What is fertilisation?

Answer 17

The fusion of a sperm and an oocyte

Question 18

What does fertilisation produce?

Answer 18

A diploid zygote (single cell embryo)

Question 19

What are the 2 options of sex determination in zygotes?

Answer 19

46 XX or 46 XY

Question 20

What is cleavage?

Answer 20

A period of rapid mitotic cell division with no increase in size

Question 21

What does cleavage form?

Answer 21

A morula (16+) cells then a blastocyst (days 1-4)

Question 22

What is gastrulation?

Answer 22

The formation of the germ layers which establishes body axes

Question 23

When does gastrulation happen?

Answer 23

Week 3

Question 24

What are the 3 germ layers?

Answer 24

Ectoderm, Mesoderm and Endoderm

Question 25

What is formation of the body plan?

Answer 25

Embryonic folding (gut tube within a skin/body wall/tube)

Question 26

What in organogenesis?

Answer 26

the formation of organs and organ systems

Question 27

When is the basis of all organs/their systems in place by?

Answer 27

The end of the embryonic period but continues throughout the foetal period

Question 28

What trimester does the foetus lengthen most?

Answer 28

2nd

Question 29

What trimester is the most weight gained?

Answer 29

3rd

Question 30

What are the main events that occur during the foetal period?

Answer 30

Tissues mature and become functional, overt sexual differentiation and bone laid down, connections in the central nervous system

Question 31

What are some of the primary processes involved in development from zygote to human?

Answer 31

cell division, differentiation, cell attachment (eg tissue formation), apoptosis, induction (ability of one cell type to cause another to differentiate) and cell migration

Question 32

What are some of the secondary processes involved in development from zygote to human?

Answer 32

axis formation/polarity (so cells know where they are in relation to one another and the whole embryo) and folding/rotation

Question 33

What are the 2 types of control of development?

Answer 33

genetic control (gene expression) and epigenetic control

Question 34

What is epigenetic control?

Answer 34

the preferential expression of either the maternal or the paternal copy of the gene