Lecture 15: Basic Body Plan

Question 1

notochordal process

Answer 1

cells of mesodermal layer migrate cranially down the midline to form the notochordal process, until it reaches the prechordal plate

Question 2

function of notochord

Answer 2

primary inductor of the embryo
defines cranial caudal axis
formation of vertebral column
Induces overlying ectoderm to form neural plate

Question 3

paraxial mesoderm

Answer 3

is found directly next to the notochord on either side, running down the same axis. Eventually gives rise to somites

Question 4

Intermediate mesoderm

Answer 4

Immediately lateral to the paraxial mesoderm, gives rise to some of the urinary tract and reproductive system

Question 5

Lateral Plate mesoderm

Answer 5

Lateral to intermediate mesoderm. has two parts, somatopleuric mesoderm and splanchopleuric mesoderm. The somatopleuric mesoderm is continuos with the extraembryonic mesoderm

Question 6

Somatopleuric mesoderm

Answer 6

Gives rise to dermis, continuous with extra-embryonic mesoderm, top layer

Question 7

splanchnopleuric mesoderm

Answer 7

Gives rise to walls of developing organs. associated with yolk sac, bottom layer

Question 8

neurulation

Answer 8

Formation of neural tube

Question 9

Neural Plate

Answer 9

The ectoderm overlying the notochord is induced by the notochord to thicken, creating neuro-ectoderm that makes up the neural plate

Question 10

neural folds

Answer 10

Folds that grow up from neural plate on either side of neural groove. Eventually grow towards each other and join, forming neural tube

Question 11

Fusion of neural folds

Answer 11

Happens in the mid-region and then migrates cranially and caudally.

Question 12

neural crest cells

Answer 12

Present on the tips of the neural folds, and after fold fusion these cells are pinched off and migrate laterally and superficial to the neural tube

Question 13

Neural tube migration

Answer 13

Dis-connects from ectoderm and migrates below into mesoderm

Question 14

Neuropores

Answer 14

Present in anterior and posterior. Rostral closes day 24-25, caudal day 27. Not closing is called spina bifida

Question 15

neural tube function

Answer 15

gives rise to CNS

Question 16

neural crest cells function

Answer 16

gives rise to PNS, face muscles and bones, and adrenal medulla

Question 17

cranial-caudal fold

Answer 17

Caused by very quick proliferation of neural tube cells at the cranial end to create forebrain/midbrain

Question 18

Oropharyngeal membrane (prechordal plate)

Answer 18

Site of mouth

Question 19

Cloacal membrane

Answer 19

site of anus

Question 20

Somites

Answer 20

paired blocks of mesoderm that develop from paraxial mesoderm end of week 3. first appear cranially. By end of week 5 42-44 pairs

Question 21

somite’s function

Answer 21

give rise to skeletal muscles, dermis and axial skeleton

Question 22

coelemic spaces

Answer 22

Form within lateral mesoderm and cardiogenic mesoderm, shapes coalesce into embryonic coelem

Question 23

purpose of embryonic coelem

Answer 23

pericardial cavity, pleural cavity, peritoneal cavity

Question 24

Angiogenesis begins when and where

Answer 24

Begins week 3
Begins 
Extraembryonic mesoderm
Yolk sac
Connecting stalk
Chorion

Question 25

angioblasts

Answer 25

mesenchymal cells in the yolk sac, which aggregate to form blood islands

Question 26

blood vessel formation

Answer 26

small cavities form within blood islands, the angioblasts flatten to form endothelium, some endothelium breaks off and form red blood cells, cavities fuse to form vessels

Question 27

heart tube

Answer 27

endocardial tubes arise from cardiogenic mesenchyme week 3, fuse to create heart tube. The heart tube fuses with vessels to create primitive cardiovascular system

Question 28

Allantois

Answer 28

Out-pouching of yolk sac into connecting stalk, associated with development of bladder