Embryology

Question 1

What happens in the third week of embryonic development?

Answer 1

Gastrulation.

Question 2

what does gastrulation involve?

Answer 2

The embryoblast develops into three distinct germ layers: Ectoderm, Mesoderm and Endoderm.

Question 3

Give some examples of what the ectoderm forms:

Answer 3

1. Epidermis of skin, hair and nails
2. Mammary, sweat, sebaceous and pituitary glands
3. Central + peripheral nervous system
4. enamel of teeth
5. sensory epithelium of nose, ear and eye
6. some of eye (lens + inner parts)

Question 4

Give some examples of what the mesoderm forms:

Answer 4

1. Musculoskeletal system
2. Deep layers of skin
3. Abdominal and chest walls + lining
4. walls (not lining) of bowl
5. Urogenital system

Question 5

Give some examples of what the endoderm forms:

Answer 5

1. Epithelial lining of GI tract, respiratory tract and urinary bladder
2. Parenchyma of (para)thyroid gland, liver and pancreas
3. Epithelial lining of tympanic cavity and auditory tube
   $. Plays a part in development of notochord

Question 6

What are the three main layers of the mesoderm:

Answer 6

1. Paraxial plate
2. Intermediate plate
3. Lateral plate

Question 7

When and how does the primitive heart tube form?

Answer 7

Days 19-21, from the fusion of the two endocardial tubes.

Question 8

What are the five parts/bulges the primitive heart develops?

Answer 8

1. Aortic sac
2. Bulbus cordis
3. Primordial ventricle
4. Primordial atrium
5. Sinus Venosus

Question 9

What does the bulbos cordis go on to form?

Answer 9

The right ventricle, the smooth outflow portions of the ventricles and the proximal aorta and pulmonary trunk.

Question 10

What has side of the heart has greater pressure in the developing fetus?

Answer 10

The right side as the lungs and pulmonary circulation are not fully functional.

Question 11

What are the two foramen that occur before foramen ovale.

Answer 11

Foramen primum -> foramen secundum.

Question 12

Which out of atria and ventricles are the first to have a left and a right?

Answer 12

Atria.

Question 13

At what time does the ventricular septum grow?

Answer 13

The end of the fourth week.

Question 14

What are conotruncal ridges (truncoconal swellings)?

Answer 14

Ridges of tissue on the sides of the truncus arterioses that will grow in a spiral and fuse to form a septum to divide the aorta and pulmonary trunk (aorticapulmonary septum).

Question 15

Which aortic arch develops into the actual aortic arch?

Answer 15

The 4th arch (left one - right one forms right subclavian).

Question 16

Which aortic arch disappears completely?

Answer 16

The 5th.

Question 17

Which arches form:

a. the stapedial?
b. the carotid?
c. the maxillary?

Answer 17

a. 2
b. 3
c. 1

Question 18

What period of development is when the aortic arches develop?

Answer 18

4-7 weeks.

Question 19

Which aortic arch forms a pulmonary artery and the ductus arterioses?

Answer 19

The 6th arch (left).

Question 20

Which vessel carries oxygenated blood from the placenta to the fetus?

Answer 20

The umbilical VEIN.

Question 21

How does blood bypass the liver?

Answer 21

With the ductus venosus.

Question 22

What shunts blood from the pulmonary trunk to the aorta?

Answer 22

The ductus arteriosus.

Question 23

What does the umbilical vein eventually become?

Answer 23

Ligamentum teres.

Question 24

What causes the foramen ovalis to close?

Answer 24

Lungs open up at birth decreasing pressure, so pressure is now greater in left side. Thus blood tries to flow back through the foramen ovali which pushes it shut.