Embryonic Period Weeks 3-8

Question 1

Tissues and organs derived from embryonic ectoderm

Answer 1

1. neuroectoderm- which gives rise to all neural tissues
2. Epidermal covering of the body
   (epidermis, sweat glands, sebaceous glands, mammary glands, hair, nails, cornea, anterior pit., enamel, internal ear, lens of eye)

Question 2

Describe the process of Neurulation

Answer 2

1. BMP4 is blocked- allows induction of neural plate by notochord and prechordal plate
2. Neural plate rounds up to form neural tube
3. Fusion of neural tube proceeds (cranial to caudal)
4. Neural tube forms CNS
5. Cranial neuropore closes day 25
6. Caudal neuropore closes day 27

Question 3

Neuroectoderm includes

Answer 3

Neurulation and neural crest cells

Question 4

What are the origins of neural crest cells

Answer 4

from neural folds
migrates into mesenchyme
from PNS

Question 5

Neural Crest Cell Derivatives

Answer 5

1. connective tissue and bone of the face and skull
2. Cranial nerve ganglia
3. C cells of the thyroid gland
4. conotruncal septum in the heart
5. odontoblasts
6. dermis in the face and neck
7. spinal (dorsal root) ganglia
8. sympathetic chain and preaortic ganglia
9. Parasympathetic ganglia of the gastrointestinal tract
10. adrenal medulla
11. schwann cells
12. glial cells
13. arachnoid and pia mater (leptomeninges)
14. Melanocytes

Question 6

What are the types of mesoderm derivatives

Answer 6

1 axial mesoderm
2 paraxial mesoderm
3 intermediate mesoderm
4 lateral plate mesoderm
5 mesodermal contribution to the chorion

Question 7

What tissues and organs are derived from axial mesoderm

Answer 7

prechordal plate, notochord, caudal eminence

Question 8

What tissues and organs are derived from paraxial mesoderm

Answer 8

Somitomeres and somites

Question 9

What are the two types of somitomeres

Answer 9

• in the head- somitomeres 1-7 + neural plate -> neuromeres -> wonderful things
• in body- somitomeres become somites

Question 10

Describe what somites form

Answer 10

• occipital region–> caudally
• can be used to approximate age of embryo
• forms sclerotome- vertebrae, ribs, base of skull
• forms dermatomyotome

Question 11

sclerotome

Answer 11

vertebrae, ribs, base of skull

Question 12

What are the parts of dermatomyotome

Answer 12

a. dermotome- dermis of the skin

b. myotome- skeletal muscle of the body and limbs

Question 13

What tissues and organs are derived from intermediate mesoderm

Answer 13

• forms most organs (CT, smooth muscle and epithelial linings) in both the urinary and genital systems
• the endoderm provides the remaining epithelial linings of some UG organs

Question 14

What tissues and organs are derived from lateral plate mesoderm

Answer 14

In body splits into two arms
1. somatic- ct and smooth muscle of body wall, bones, and cartilage of limbs and limb girdles
2. splanchnic- ct and smooth muscle of all endoderm-lined organs and all tissues of cardiovascular system
formation of the intraembryonic cavity
in the head it acts differently

Question 15

What is different about the lateral plate mesoderm in the head?

Answer 15

the lateral plate does not split

Question 16

somatic lateral plate mesoderm becomes

Answer 16

ct and smooth muscle of body wall, bones, and cartilage of limbs and limb girdles

Question 17

Splanchnic lateral plate mesoderm becomes

Answer 17

ct and smooth muscle of all endoderm-lined organs and all tissues of cardiovascular system

Question 18

What is the significance of the dermatomyotome?

Answer 18

each one retains its own segmental innervation form its origin

Question 19

Which is the 1st major organ system to be fully developed and functional prenatally?

Answer 19

cardiovascular system

Question 20

What are the 3 phases of embryonic development?

Answer 20

1. growth - cell division
2. morphogenesis- development of form and includes mass cell movements
3. differentiation- maturation of physiological processes

Question 21

describe the important morphological changes that occur b/w the 3rd and 9th weeks

Answer 21

embryonic period

• early development of the nervous and cardiovascular systems
• by end of this period all major organ systems have begun to develop
• -the f(x) of most of them is minimal
• -except for the cardiovascular system

Question 22

What drives cephalocaudal folding?

Answer 22

• primitive streak and notochord establish a cephalocaudal axis, right/left side and a dorsal and ventral surface
• rapid head and tail growth causes the embryo to curl toward the ventral surface.

Question 23

what are the types of embryonic folding

Answer 23

cephalocaudal folding and lateral folding

Question 24

Describe lateral folding in the embryo

Answer 24

• endoderm becomes folded into a long narrow tube w/in the embryo
• mesoderm continues to separate out ectoderm from endoderm
• the ectoderm and amniotic cavity completely encircle the embryo
• -the ectoderm forming the outercovering of the embryo

Question 25

List the tissues and organs derived from embryonic endoderm?

Answer 25

- during the folding process, endoderm is formed into epithelial tube which runs the length of the body - endoderm tube forms the epithelial lining of the GI tract - mesoderm and endoderm induce each other to forms specific GI organs - epithelial components of several other organs: pharyngeal buds, lung buds, liver, pancreas, and gall bladder

Question 26

the endoderm tube forms ___________

Answer 26

the epithelial lining of the GI tract

Question 27

What types of tissue form GI organs?

Answer 27

Mesoderm and endoderm

Question 28

The number of somites is correlated to what?

Answer 28

The approximate age of the embryo in days 20 days- 1-4 somites 21 days 4-7 somites 22 days 7-10 somites 30 days 34-35 somites. somites continue to divide after this point but they are not used to approximate age since there is a better tool.