Exam 3 embryology

Question 1

What layer does the skull and face bones come from?

Answer 1

Neuroectoderm

Question 2

What layer does the base of the skull, vertebrae and ribs come from?

Answer 2

paraxial mesoderm

Question 3

What layer does the appendicular skeleton come from?

Answer 3

lateral plate mesoderm

Question 4

What week does the skeleton begin forming?

Answer 4

Week 4

Question 5

What is the immature form of somites?

Answer 5

somitomeres

Question 6

What induces the formation of somites?

Answer 6

Neural tube

Question 7

How does development of somites progress (direction)?

Answer 7

Rostral to caudal

Question 8

What genes induce the formation of somites?

Answer 8

Hox (homeobox)

Question 9

What is mesenchyme?

Answer 9

Loosely organized embryonic connective tissue derived from mesoderm

Question 10

What is intramembranous ossification? What kind of bones?

Answer 10

Mesenchymal cells differentiate directly into osteoblasts to form flat bones

Question 11

What is endochondral ossification? What kind of bones?

Answer 11

Mesenchymal cells transform into chondroblasts, lay down hyaline cartilage. Osteoblasts come in and continue laying down bone. Long bones (femur, phalanges, sternum, vertebrae)

Question 12

What is bone growth complete?

Answer 12

when epiphyseal plate disappears

Question 13

What is marfan syndrome?

Answer 13

autosomal dominant disorder due to mutation for fibrilin that affects connective tissue; results in long thin limps and CV/lung problems

Question 14

What layer does skeletal muscle form from?

Answer 14

paraxial mesoderm > somites > dermomyotome > myotome

Question 15

What layer does smooth and cardiac muscle form from?

Answer 15

Lateral plate mesoderm–> splanchnic mesoderm

Question 16

Explain steps of myogenesis

Answer 16

mesoderm >mesenchyme >myoblasts >myotubes >multinucleated muscle fibers > striated skeletal muscle

Question 17

What gives rise to myoepithelial cells of mammary and sweat glands and iris muscle?

Answer 17

ectoderm

Question 18

What is unique about the formation of vertebrae?

Answer 18

They are intersegmental, formed by caudal part of one and the rostral part of another somite

Question 19

What forms the nucleus pulposis?

Answer 19

The notochord

Question 20

What forms the annulus fibrosis of the vertebrae?

Answer 20

sclerotome

Question 21

How does spina bifida develop?

Answer 21

failure of the neural tube to close, meaning vertebral arch fails to fuse

Question 22

Describe Spina bifida occulta, meningocele, meningomyelocele

Answer 22

Occulta: least severe, lumbosacral region, tuft of hair. Meningocele: meninges protrude through defect in spinal cord or skull. Meningomyelocele: most severe, meninges and spinal cord protrude through defect

Question 23

Describe congenital dermal sinus

Answer 23

Neural ectoderm fails to completely separate from surface ectoderm, meaning spinal cord may be tethered/open to environment

Question 24

Describe hemivertebrae; what does it cause?

Answer 24

failure of one ossification center on side of vertebral body. Causes congenital scoliosis.

Question 25

Describe congenital brevicollis (Klippel-Feil sequence)

Answer 25

shortened neck due to non-segmentation of cervical vertebrae

Question 26

What is pectus excavatum

Answer 26

concave chest due to defect in sternal development, can compress lungs, shift heart

Question 27

Where do ribs start to form?

Answer 27

costal processes of thoracic vertebrae

Question 28

What causes thoracic outlet syndrome?

Answer 28

cervical C7 rib, can compress neuromuscular structures supplying upper limb

Question 29

What does the epimere develop in to?

Answer 29

Erector spinae/spinal muscles

Question 30

What structure leaves the spinal cord to innervate the erector spinae?

Answer 30

Dorsal primary rami

Question 31

What does the hypomere develop into?

Answer 31

Thoracic muscles

Question 32

What structure innervates the hypomere muscles?

Answer 32

ventral primary rami

Question 33

Describe poland syndrome

Answer 33

Failure in the development of the pectoralis muscles, usually unilateral

Question 34

Describe prune belly syndrome

Answer 34

poor development of abdominal muscle wall causing skin to wrinkle, usually urinary tract abnormalities and descent of the testicles

Question 35

Describe congenital torticollis

Answer 35

spasm or shortening of sternocleidomastoid muscles

Question 36

What forms first, upper limbs or lower limbs?

Answer 36

Upper limbs form first

Question 37

What genes control positioning of the limbs?

Answer 37

Homeobox (Hox) genes

Question 38

Where does the upper limb bud first form?

Answer 38

C5-T1 somite levels

Question 39

Where does the lower limb bud first form?

Answer 39

L2-S2 somite levels

Question 40

What category does the apical ectodermal ridge (AER) fall into?

Answer 40

a placode

Question 41

What is the apical ectodermal ridge?

Answer 41

thickening at the distal end of the limb bud which secretes FGFs

Question 42

What polarity does the AER help the limbs form into?

Answer 42

Proximal and distal axis

Question 43

How does the zone of polarizing activity (ZPA) form?

Answer 43

respond to FGFs from the AER

Question 44

What genes does the ZPA express?

Answer 44

sonic hedgehog gene

Question 45

What axis does the ZPA help to develop?

Answer 45

anterior-posterior axis (pinky vs thumb)

Question 46

What is absence of malformation of one or more limbs called?

Answer 46

Amelia

Question 47

What is partial absence of a limb called?

Answer 47

Meromelia or phocomelia

Question 48

What is syndactyly?

Answer 48

Failure of apoptosis resulting in webbed fingers or toes

Question 49

What is polydactyly?

Answer 49

duplication of digits