Embryology

Question 1

Layers of trilaminar embryo

Answer 1

Ectoderm, mesoderm and endoderm (Top to bottom)

Question 2

Regions of mesoderm

Answer 2

Medial to lateral - Paraxial, intermediate and lateral plate

Question 3

Somatic vs visceral mesoderm

Answer 3

Somatic mesoderm is on top of visceral mesoderm

Question 4

Which part of gut is the last to close

Answer 4

Midgut

Question 5

What is lateral folding of the embryo

Answer 5

Converts the open coelom into a closed cavity, creating thoracic and abdominal cavities also closing fore and hind gut

Question 6

What forms the foregut and developing heart tube

Answer 6

Cranial folding

Question 7

What forms the hindgut, anus and umbilical cord

Answer 7

Caudal folding

Question 8

What month can sex of foetus be determined

Answer 8

3 months

Question 9

When does rapid increase in length happen

Answer 9

4 - 5 months

Question 10

When does increase in weight happen

Answer 10

6 months - birth

Question 11

What is phocomelia

Answer 11

Limbs are attached close to the trunk, are underdeveloped or absent

Question 12

What can cause phocomelia

Answer 12

Thalidomide taken during pregnancy

Question 13

What is spina bifida

Answer 13

Incomplete closure of the backbone and membranes around the spinal cord

Question 14

What can help protect against spina bifida

Answer 14

Folic acid

Question 15

Period of greatest sensitivity to teratogenesis

Answer 15

3 to 8 weeks

Question 16

What is the truncus arteriosus

Answer 16

Structure in primitive heart that develops into the aorta and pulmonary trunk

Question 17

How do the atria seperate

Answer 17

Septum primum grows downward into the single atrium. Small perforations in the atria lead to the formation of a foraman secumdum or ostium secumdum. A semilunar shape septum secundum grows downward to the right of septum primum and foramen secundum. A foramen ovale develops in beween septum secundum and ostium secundum.

Question 18

When do the septum primum and septum secundum fuse?

Answer 18

Shortly after birth

Question 19

Communication between right and left atria

Answer 19

Foramen ovale

Question 20

What causes closure of foramen ovale

Answer 20

Change in pressure difference after birth, higher pressure in left atria than right pushes the septum primum against foramen ovale.

Question 21

Common atrial septal defects

Answer 21

Excessive resorption of septum primum, absent septum secundum

Question 22

Common ventricular septal defects

Answer 22

Transposition of great vessels - Aorta exists right ventricle and pulmonary trunk exists left ventricle, patent ductus arteriosus

Question 23

Tetralogy of Fallot

Answer 23

Pulmonary stenosis, right ventricular hypertrophy, ventricular septal defect, overiding aorta (Aorta above VSD)