Third to Eight Weeks- The Embryonic Period Flashcards Preview

Anatomy > Third to Eight Weeks- The Embryonic Period > Flashcards

Flashcards in Third to Eight Weeks- The Embryonic Period Deck (21):
1

When does the embryonic disc form a head fold, tail ford, and lateral fold?

the 4th week, due to rapid growth

2

Derivatives of the ectoderm layer

the central and peripheral nervous systems, the sensory epithelium of the eye, ear, and nose, the epidermis and epidermal derivatives

3

Cells of the neural plate make up the _____.

neuroectoderm

4

Between 25 and 27 days the cranial and caudal neuropores close, formed a closed central nervous system consisting of what?

brain vesicles and spinal cord

5

Derivatives of the mesoderm

by the 17th day the shealth of mesoderm begins to differentiate and form 3 subdivisions, the paraxial, intermediate, and lateral mesoderm

6

Paraxial mesoderm

forms the occipital, cervical, throacic, lumbar, sacral, and coccygeal pairs of somites

7

Intermediate mesoderm

forms the urogenital organ components

8

Lateral mesoderm

splits into 2 layers, parietal (somatic) and visceral (splanchnic) mesoderm

9

Mesoderm cells of the parietal layer form what? (from the lateral mesoderm)

mesothelial serous membranes that line the pleural, pericardal, and peritoneal cavities

10

Mesoderm cells of the visceral layer form what? (from the lateral mesoderm)

thin, serous membrane around the organs

11

Vasculogenesis

blood islands appear in the mesoderm that surrounds the umbilical vesicle around the 3rd week of development

12

Blood islands arise from mesoderm that forms hemangioblasts that differentiate into what?

angioblasts, that form blood vessels

13

Angiogenesis

once vessels are formed by vasculogenesis, new vessels are added from sprouting from the existing vessels

14

Blood cell formation

first blood cells arise from hemangioblasts in the center of the blood islands in the umbilical vesicle that form hematopoietic stem cells

15

Derivatives of the endodermal layer

the GI tract

16

What does the midgut communicate with?

the umbilical vesicle via the vitelline duct

17

What is the foregut closed off by?

the oropharyngeal membrane (ruptures in week 4)

18

What is the hindgut closed off by?

the cloacal membrane (ruptures in week 7)

19

What does the endodermal germ layer give rise to?

epithelial lining of organs such as the respiratory and urinary tracts, the parenchyma of the thyroid, liver, and pancreas

20

How is the age of the embryo determined starting in the second month?

the crown-rump length

21

When are the most structural birth defects likely to occur?

the third to eight week period of organogenesis (where the organs are formed)