Early embryology

Question 1

What is a blastomere?

Answer 1

When the fertilised oocyte splits into two cells

Question 2

What is a morula?

Answer 2

When there are 16 cells- 4 cell divisions

Question 3

What is the trophoblast?

Answer 3

The outer cell mass- contacts with the endometrium of the uterus to facilitate implantation and the formation of the placenta

Question 4

What is the embryoblast?

Answer 4

The inner cell mass- responsible for the formation of the embryo itself

Question 5

What are the two cell types that form from the trophoblast?

Answer 5

Syncytiotrophoblast and cytotrophoblast

Question 6

What are the two layers of the bilaminar disc?

Answer 6

Epiblast and hypoblast (divisons of the embryoblast)

Question 7

What layer of the embryo becomes continuous with the uterus?

Answer 7

Syncytiotrophoblast

Question 8

What is the primitive streak?

Answer 8

A groove in the midline of the epiblast.

Question 9

Where is the primitive pit?

Answer 9

Within the primitive node, which lies at the cranial end of the primitive streak

Question 10

What layer of the bilaminar disc does the trilaminar disc form from?

Answer 10

The epiblast

Question 11

What are layers of the trilaminar disc?

Answer 11

Endoderm, mesoderm, ectoderm

Question 12

What structures are derived from the endoderm?

Answer 12

Lining of digestive, respiratory, and urogenital tract, liver and pancreas

Question 13

What structures are derived from the mesoderm?

Answer 13

Notochord, musculoskeletal system, muscular layer of stomach, intestine etc, circulatory system, urogenital system

Question 14

What structures are derived from the ectoderm?

Answer 14

Epidermis of skin, cornea and lens of eye, nervous system

Question 15

What are the somites derived from?

Answer 15

Paraxial mesoderm

Question 16

How many pairs of somites are formed?

Answer 16

44- but 13 break down leaving 31

Question 17

What is a dermatome?

Answer 17

A strip of skin innervated by a single spinal nerve

Question 18

What is a myotome?

Answer 18

A group of muscles innervated by a single spinal nerve root

Question 19

What nerve roots give rise to achilles reflex?

Answer 19

S1,S2

Question 20

What nerve roots give rise to the patellar reflex?

Answer 20

L3,L4

Question 21

What nerve roots give rise to biceps and brachiradialis reflex?

Answer 21

C5,C6

Question 22

What nerve roots give rise to the triceps reflex?

Answer 22

C7,C8

Question 23

How many pharyngeal clefts are there?

Answer 23

4

Question 24

Which pharyngeal cleft gives rise to a permanent structure?

Answer 24

1

Question 25

What does the 1st pharyngeal cleft give rise to?

Answer 25

The external auditory meatus

Question 26

What do the 2nd, 3rd and 4th pharyngeal clefts form?

Answer 26

Temporary cervical sinuses

Question 27

How many pharyngeal arches are there?

Answer 27

5

Question 28

What does the 1st pharyngeal arch give rise to?

Answer 28

Eustachian tube and middle ear cavity

Question 29

What does the 2nd pharyngeal arch give rise to?

Answer 29

Lining of the palatine tonsils

Question 30

What does the 3rd pharyngeal arch give rise to?

Answer 30

Inferior parathyroid glands and thymus

Question 31

What does the 4th pharyngeal arch give rise to?

Answer 31

Superior parathyroid glands and ultimobranchial body

Question 32

What does the 5th pharyngeal arch give rise to?

Answer 32

Nothing!

Question 33

What nerve is the first pharyngeal arch associated with?

Answer 33

Trigeminal

Question 34

What nerve is the second pharyngeal arch associated with?

Answer 34

Facial

Question 35

What nerve is the third pharyngeal arch associated with?

Answer 35

Glossopharyngeal

Question 36

What nerve is the fourth pharyngeal arch associated with?

Answer 36

Superior laryngeal branch of vagus

Question 37

What nerve is the sixth pharyngeal arch associated with?

Answer 37

Recurrent laryngeal branch of vagus