Anatomy Midterm 2 - Embyology

Question 1

What does the trophoblast turn into?

Answer 1

Cytotrophoblast and synctiotrophoblast

Question 2

What does the hypoblast give rise to?

Answer 2

primary/primitive endoderm

Question 3

What developes during the second week?

Answer 3

Amniotic cavity and yolk sac form
Bilaminar embryonic disc
Epiblast - faces amniotic cavity
Hypoblast - faces primary yolk sac

Question 4

What forms during gastrulation?

Answer 4

Bilaminar disc becomes trilaminar disc
Primitive streak (primitive groove)
Primitive node
intraembryonic endoderm - forms at roof of yolk sac
intraembryonic ectoderm - between endoderm and epiblast

Question 5

What are the layers of the trilaminar disc and their derivatives?

Answer 5

Ectoderm - nervous system, epidermis, hair, nails, tooth enamel
Endoderm - epithelium of GI and respiratory tracts, some glands
Mesoderm - muscle, CT, vessels, blood, skeleton, reproductive and excretory gland

Question 6

How does the notochord form?

Answer 6

Forms during 3rd week
Neural plate -> neural groove -> neural tube
Process is called neuralation

Question 7

How do the somites form?

Answer 7

Embryo becomes segmented (somite)

Question 8

What are the somites associated with?

Answer 8

Spinal nerve
Myotome - developing muscle tissue
Sclerotome - developing skeletal muscle
Dermatome - area of skin innervated by segment’s spinal nerve

Question 9

Differentiation of mesoderm (in early somite)?

Answer 9

Paraxial mesoderm - nearest notochord
Lateral plate mesoderm - furthest lateral
Intermediate mesoderm - between Paraxial and Lateral plate

Question 10

What is the differentiation of the somite?

Answer 10

Sclerotome - ventromedial part of somites, mesenchymal cells that develop into vertebrae and ribs

Demomyotome - develops into skin and muscle cell precurssors

Question 11

What happens during the first week?

Answer 11

zygote -> morula -> blastocyst w/blastocyst cavity -> trophoblast -> inner cell mass

Question 12

What is mesenchyme?

Answer 12

Embryological CT that gives rise to other CT

Question 13

How does the vertebral centrum form?

Answer 13

Develops from 2 adjacent sclerotomes that surround the notochord

Question 14

How do neural arches form?

Answer 14

They form from sclerotomal mesenchyme surrounding the neural tube

Question 15

How do the costal processes form?

Answer 15

Form from sclerotomal mesnchyme in the body wall

Question 16

What do costal processes become?

Answer 16

Ribs in thoracic region
Part of the TP of cervical and lumbar regions
Lateral sacral masses (ala)

Question 17

How many primary ossification centers are in the vertebrae?

Answer 17

3 primary ossification centers

Question 18

How many secondary ossification centers are in the vertebrae?

Answer 18

5 secondary ossification centers

Question 19

How do the ribs form?

Answer 19

Form from costal processes and are composed of mesenchyme in the body wall or thoracic vertebrae

Question 20

Hoe does the sternum develop?

Answer 20

Develops from a pair of vertically oriented mysenchymal sternal bars that form in the ventrolateral body wall

Question 21

What are some malformations?

Answer 21

Accessory ribs, fused ribs, hemivertebra, spina bifida