MSK embryology

Question 1

hemivertebra is one cause of ____

Answer 1

scoliosis

Question 2

lack of development of the dorsal vertebral arch from the sclerotome can form

Answer 2

neural tube defects

like spina bifida

Question 3

rib congenital anomalies

Answer 3

supernumeray or accessory ribs

Question 4

lumbar rib congenital anomaly

Answer 4

an extra rib or pair of ribs may develop in the lumbar area from the L1 vertebra

no symptoms

more common than cervical rib anomalies

Question 5

cervical rib congenital anomaly -

how many people does it affect?

Answer 5

• an extra rib or pair of ribs may develop in the cervical area from the C7 vertebra.
• 0.5 to 1% of the population
• may compress brachial plexus and subclavian artery! SYMPTOMATIC

Question 6

Answer 6

boy has achondroplasia - lack of endochondrial ossification in distal areas of bone, so bone doesn’t grow -> short ribs

Question 7

week that all cartilage models are formed in utero

Answer 7

week 8

Question 8

week that all 4 limb buds have begun to form

Answer 8

week 4

Question 9

Answer 9

syndactyly

Question 10

Answer 10

polydactyly

Question 11

notochord becomes the

Answer 11

nucleus pulposus of intervertebral discs

Question 12

paraxial mesoderm becomes

Answer 12

somites - that then form vertebrae/ribs, muscles of the limbs and trunk, skin of the limbs and trunk

Question 13

lateral plate mesoderm

Answer 13

limb skeleton

Question 14

paraxial mesoderm forms ____ and they give rise to the body’s ____

Answer 14

somites

segments

Question 15

each body segment includes

Answer 15

dermatome - skin

muscle, skeleton, and blood vessels

Question 16

the limbs ____ during development, changing the orientation of the _______ from thne original orientation of the embryo

Answer 16

rotate

dermatomes

Question 17

sclerotome

Answer 17

cartilage and bone

Question 18

the lateral plate mesoderm is divided by the coelom into

Answer 18

an inner splanchnic visceral layer

an outer somatic layer (forms limb skeleton and anterolateral body wall)

Question 19

intramembranous ossification

Answer 19

forms the skill

mesenchymal cells differentiate directly into bone forming osteoblasts, then the cells make a bone matrix (osteoid)

NO CARTILAGE MODEL

Question 20

endochondral ossification

Answer 20

starts with hyaline cartilage and then kills the cartilage when a bone collar forms around the diaphysis (long shaft of bone).

then from the periostem, blood vessels, osteoblasts an clasts invade and form the primary ossification center, where bone formation spreads from here

then secondary ossification center forms epiphyses

all other bones of the body besides the skull

Question 21

bone replaces hyaline carticlage throughout the cartilage model except the _____ and ____

Answer 21

articular cartilages (around joints of bone)

epiphyseal plates (growth plates needed for bone growth in puberty)

Question 22

accessory ribs are most likely to develop from which vertebra?

Answer 22

L1

Question 23

neural tube defects

Answer 23

also called spina bifida

mild and moderate forms arise from lack of development of dorsal vertebral arch from sclerotome (no arch so cord protrudes through where the spinous process would be

Question 24

hemivertebra

Answer 24

lack of formation of part of a vertebra

• failure of ossiciation center to form properly
• improper subdivision of sclerotomes

Question 25

the presence of ___ could be a cause for scoliosis

Answer 25

hemivertebra

Question 26

cranial and caudal parts of adjacent sclerotomes that join together to create

Answer 26

vertebra

Question 27

most common muscles for agenesis of upper limb

Answer 27

palmaris longus

part of pectoralis major

serratus anterior

Question 28

etiology of achondroplasia

Answer 28

autosomal dominant

80% are spontaneous patermal mutations of FGFR 3 gene

Question 29

clinical signs of achondroplasia

Answer 29

short limbs with large torso and head relative to limbs, prominant forehead and flattened nasal bridge

Question 30

development of digits

Answer 30

forms wide paddle, then digital rays develop where each digit will form, then apoptosis occurs and separates individual digits

Question 31

limbs grow distally by mitosis of cells beneath the

Answer 31

apical ectodermal ride (AER)

Question 32

type of cartilage in limb skeleton during endochondral ossification

Answer 32

hyaline cartilage model

Question 33

endochondral ossification follows this direction

Answer 33

proximal to distal, so distal elements are added progressively

Question 34

most common cause of dwarfism

Answer 34

achondroplasia