Week 3 Embryonic Dev. - Ach Flashcards Preview

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Flashcards in Week 3 Embryonic Dev. - Ach Deck (41)
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1

What are the functions of a notochord?

define axes
mechanical role in folding process
Induces signaling for the neural tube

2

What does the neural tube induce?

formation of the somites

3

What is mesenchyme?

embryonic connective tissue

multipotent

derived from mesoderm and neural crest

4

What week do limb buds appear??

WEEK FOUR!

5

Why is week 4 a critical period?

Neural tube begins to close
Appearance of somites
Limb buds appear
Organ systems start developing

6

How are somites formed? How many pairs are formed?

Somitomeres become compacted and bound by epithelium to become somites.

42-44 paris are formed

7

Which pairs remain somitomeres and do not compact into somites?

Pairs 1- 7

8

What are somitomeres?

paired blocks of loose mesoderm derived from paraxial mesoderm. They form segmentally along each side of neural tube at the end of the 3rd week

9

What happens in intramembranous ossification?

Mesenchymal cells differentiate directly into osteoblasts
EX: flat skull bones

10

What happens in endochondral ossifications?

- long bone formation
-Mesenchymal cells transforms into chondroblasts

-chondroblasts hyaline cartilanginous model

-deposition of ca+
-Osteoblasts in diaphysis form primary ossification center
-osteoblast replace cartilage with bone
-Growth plate (epiphyseal) continues to lay down hyaline cartilage, lengths bone from diaphysis toward epiphysis
-Secondary ossification centers are in epiphysis (most form postnatally). Growth toward daiphysis

11

How is bone age determined?

presence/absence of ossification centers and status of growth plate

12

Achondroplasia

can't covert all the cartilage into bone

most common form of dwarism (limbs short)

13

Acromegaly

excess growth hormone secretion after closure of growth plates. INCORRECT PORPORTIONS. Big head, feet, and hands

14

Gigantism

excess growth hormone before growth plase closure. NORMAL PORPORTIONS. Big overall

15

Marfan Syndrome

Mutations in fibrillin-1
Affects connective tissue
Results in long limb, cardio and lung problems (Abe lincoln)

16

Osteogenesis imperfecta

Type 1 collagen gene
Extreme bone fragility
Sponateous fractures

17

Congenital Hip DYsplasia/ Dislocation

Incomplete formation of acetabulum (femurs can't stay in place). Legs help at different positions, less movement, uneven leg length

18

Where do smooth muscles of the gut and respiratory come from?

Originates from splanchnic mesoderm of the lateral plate

19

Explain resegmentation of the vertebral column during development

-sclerotome cells surround notocord.
-Each segment is divided by an intersclerotomic fissure (von Ebner's)
-this is where the spinal nerves will go through
-then each vertebra is formed by the dense part of one somite and the loose of another

20

Describe formation of the intervertebral discs

The von ebners fissures become the discs.
Nucleus pulposis is derived from the notochrod.
The annulus fibrosis derived from the sclerotome

21

Spinda bifida

failure of the neural tube to close. (occulta, meningocele, meningomyelocele)

22

Spinda bifida occulta

least severe
marked by tuft of hair

23

Spina bifida meningocele

meninges protrude through defect in spindal cord or skull
cyst, but cord is not in cyst

24

Spinda bifida meningomyelocele

meninges and spinal cord protrude through defect. Most severe

25

Congenital dermal sinus

neural ectoderm fails to completely separate from the surface ectoderm. Spinal cord may be tethered

26

hemivertebra

caused by failure of ossification center on one side of vertebral body (can cause congenital scoliosis)

27

Congenital brevicollis

shortened neck due to non-segmentation of cerical vertebrae. Limited movement of neck, low hairline.

28

Pectus excavatum

excess cartilage in sternum. Repairable. Concave chest

29

Thoracic outlet syndrome

C7 forms rudimentary rib that can compress neurovascular structures

30

What do myoblasts in epimere form? What innervates them?

deep muscles of the back. Erector spinae

-innervated by the dorsal primary rami