Week 3 Embryonic Dev. - Ach

Question 1

What are the functions of a notochord?

Answer 1

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

Question 2

What does the neural tube induce?

Answer 2

formation of the somites

Question 3

What is mesenchyme?

Answer 3

embryonic connective tissue

multipotent

derived from mesoderm and neural crest

Question 4

What week do limb buds appear??

Answer 4

WEEK FOUR!

Question 5

Why is week 4 a critical period?

Answer 5

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

Question 6

How are somites formed? How many pairs are formed?

Answer 6

Somitomeres become compacted and bound by epithelium to become somites.

42-44 paris are formed

Question 7

Which pairs remain somitomeres and do not compact into somites?

Answer 7

Pairs 1- 7

Question 8

What are somitomeres?

Answer 8

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

Question 9

What happens in intramembranous ossification?

Answer 9

Mesenchymal cells differentiate directly into osteoblasts

EX: flat skull bones

Question 10

What happens in endochondral ossifications?

Answer 10

• 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

Question 11

How is bone age determined?

Answer 11

presence/absence of ossification centers and status of growth plate

Question 12

Achondroplasia

Answer 12

can’t covert all the cartilage into bone

most common form of dwarism (limbs short)

Question 13

Acromegaly

Answer 13

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

Question 14

Gigantism

Answer 14

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

Question 15

Marfan Syndrome

Answer 15

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

Question 16

Osteogenesis imperfecta

Answer 16

Type 1 collagen gene
Extreme bone fragility
Sponateous fractures

Question 17

Congenital Hip DYsplasia/ Dislocation

Answer 17

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

Question 18

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

Answer 18

Originates from splanchnic mesoderm of the lateral plate

Question 19

Explain resegmentation of the vertebral column during development

Answer 19

• 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

Question 20

Describe formation of the intervertebral discs

Answer 20

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

Question 21

Spinda bifida

Answer 21

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

Question 22

Spinda bifida occulta

Answer 22

least severe

marked by tuft of hair

Question 23

Spina bifida meningocele

Answer 23

meninges protrude through defect in spindal cord or skull

cyst, but cord is not in cyst

Question 24

Spinda bifida meningomyelocele

Answer 24

meninges and spinal cord protrude through defect. Most severe

Question 25

Congenital dermal sinus

Answer 25

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

Question 26

hemivertebra

Answer 26

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

Question 27

Congenital brevicollis

Answer 27

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

Question 28

Pectus excavatum

Answer 28

excess cartilage in sternum. Repairable. Concave chest

Question 29

Thoracic outlet syndrome

Answer 29

C7 forms rudimentary rib that can compress neurovascular structures

Question 30

What do myoblasts in epimere form? What innervates them?

Answer 30

deep muscles of the back. Erector spinae

-innervated by the dorsal primary rami

Question 31

What do myoblasts in the hypomere from? what innervated them?

Answer 31

the trunk wall.

-ventral primary rami

Question 32

Poland syndrome

Answer 32

underdevelopment of absence of pectoralis muscles

Question 33

Prune belly syndrome

Answer 33

poor development of abdominal muscle wall causing skin to wrinkle

Question 34

Congenital torticollis

Answer 34

spasm of shortening of one side of sternocleidomastoid muscle. Head twisted to one side.

Question 35

apical ectodermal ridge (AER)

Answer 35

growth proximal to distal
cells further from AER differentiate
-AER also induced apoptosis to get rid of webs between fingers

Question 36

Zone of polarizing activity (ZPA)

Answer 36

• responds to FGFs from AER

- determines anterior vs. posterior (thumb vs. little finger)

Question 37

Amelia

Answer 37

absence or malformation of one or more limbs

Question 38

Meromelia or Phocomelia

Answer 38

partial absence of one or more limbs. Reduction in long bone length

Question 39

Polydactyly

Answer 39

duplication of digits

most common is little finger

Question 40

Syndactyly

Answer 40

failure of apoptosis resluts in webbed finers and or/toes. Can be inherited or develop in isolation.

Question 41

Clubfoot

Answer 41

unusal positioning of foot