embryo MSK

Question 1

Derivation: Skeleton and voluntary muscle systems are derived from ____

Answer 1

Mesoderm

Question 2

Notochord →

Answer 2

nucleus pulposus of intervertebral discs

Question 3

. Paraxial mesoderm →

Answer 3

somites → vertebrae/ribs, muscles (limbs, trunk) skin (limbs, trunk)

Question 4

Intermediate mesoderm →

Answer 4

urogenital system

Question 5

Lateral (plate) mesoderm →

Answer 5

limb skeleton

Question 6

Paraxial mesoderm forms ______ give rise to the ____

Answer 6

somites; segments

Question 7

The limbs _____ during development, changing the orientation of the dermatomes in the limbs from the original orientation in the embryo.

Answer 7

rotate

Question 8

Each somite divides into three parts in order to form all the structures in the segment:

Answer 8

Dermatome → dermis

Myotome → skeletal muscle

Sclerotome → cartilage, bone

Question 9

Lateral plate mesoderm is divided by the coelom (body cavity) into…

______ that forms GI wall and _____ that forms limb skeleton and Anterolateral body wall

Answer 9

An inner splanchnic (visceral) layer ; An outer somatic layer (B,C)

Question 10

Bones are formed from mesoderm in one of 2 ways:

Answer 10

intramembranous ossification and endochondrial ossification

Question 11

Intramembranous Ossification are drived from ____ when ______ cells differentiate directly into bone forming cells = ______ that make up ____ bones of the skull

Answer 11

mesoderm; Mesenchymal; osteoblasts; Flat bones of the skull (C)

Question 12

Starts with cartilage model of a bone. Then must kill the cartilage and replace with bone = _______

Answer 12

endochondral ossification

Question 13

1st step in forming Endochondral Ossification

Answer 13

Embryonic hyaline cartilage model develops.

Question 14

2nd step in endochondrial ossification

Answer 14

“Bone collar” forms around cartilage diaphysis. Chondrocytes within die. (B)

Question 15

3rd step in endochondrial ossification

Answer 15

1.From the periosteum, blood vessels, osteoblasts and osteoclasts invade and form the primary ossification center. Bone formation begins and spreads from here. (C)

Question 16

4th step in endochondral ossification

Answer 16

4.Secondary ossification centers form in epiphyses → bone formation in each. (D)

•Some begin just before birth, most after birth.

Question 17

Bone replaces ______ throughout the cartilage model, except the ______ and epiphyseal plates. (E)

Answer 17

hyaline cartilage; articular cartilages

Question 18

_____ cartilages remain throughout life for joint movement

Answer 18

Articular hyaline

Question 19

_____ needed for bone growth; remain until adulthood. Then replaced with bone.

Answer 19

Epiphyseal plates (aka growth plates)

Question 20

limb development begins as limb buds which have begun to gorw by _____

Answer 20

week 4

Question 21

Each upper & lower limb bud arises as lateral/medial extensions of _____

Answer 21

lateral extension of trunk somites

Question 22

Upper limb from somites

Answer 22

C5-T1

Question 23

Lower limb from somites

Answer 23

L2-S2

Question 24

Initial outgrowth of the limb bud begins with mitosis of ______ in response to mesodermal Fibroblast Growth Factors (FGFs).

New cells are added primarily at the proximal/distal end of the limb bud under the influence of the ______ which produce FGFs coded by FGF gene.

Answer 24

mesoderm cells; distal; apical ectodermal ridge cells

Question 25

Endochondral ossification. Growth follows \_\_\_\_\_

Answer 25

Proximal → Distal rule

Question 26

Limb grows distally by mitosis of cells beneath the \_\_\_\_\_\_\_

Answer 26

apical ectodermal ridge (AER).

Question 27

Proximal cells then differentiate into ______ and form a hyaline cartilage model of each bone.

Answer 27

chondroblasts (hyaline cartilage)

Question 28

All cartilage models are formed by end \_\_\_\_\_

Answer 28

Week 8.

Question 29

Distal end of each limb forms wide paddle. Digital rays develop where each digit will form. \_\_\_\_ occurs and separates the individual digits.

Answer 29

Apoptosis

Question 30

Polydactyly =

Answer 30

Extra digits on hand and/or foot.

Question 31

Syndactyly = \_\_\_

Answer 31

Fused digits

Question 32

Achondroplasia Epidemiology: Etiology: Pathogenesis: Clinical:

Answer 32

Epidemiology: common type of dwarfism. Etiology: AD; ~ 80% are spontaneous …..paternal mutations of FGFR 3 gene Pathogenesis: decreased endochondral ….ossification in limb bones → short limbs. ….No effect on membranous ossification → ….large head relative to limbs. Clinical: short limbs with large torso and ….head relative to limbs. Prominent ….forehead and flattened nasal bridge.

Question 33

As the forelimb/upper limb bud arises as extension of trunk somites, \_\_\_\_extend into the limb bud. This → Brachial Plexus. Innervates muscle and skin of upper limb.

Answer 33

ventral rami of C5-T1

Question 34

As the hindlimb/lower limb bud arises from trunk somites, _______ extend into the limb bud. This → Lumbosacral Plexus. Innervates muscle and skin of lower limb.

Answer 34

ventral rami of L2-S2

Question 35

Limb musculature derived from mesoderm (A) (paraxial → somite → \_\_\_\_\_) Cells of the myotomes ______ migrate into the limb bud. (B) The myoblasts divide into ______ masses in the limbs. (C) Spinal nerve ventral rami grow with them for innervation. (C)

Answer 35

myotome; (myoblasts); extensor and flexor muscle

Question 36

Agenesis and partial development

Answer 36

Muscles may not develop at all or a part may not develop. The most common muscles include these muscles of the upper limb: * Palmaris longus * Part of pectoralis major * Serratus anterior

Question 37

Sclerotome cells (mesoderm → somite → \_\_\_\_\_) migrate … toward _____ and _____ **medially/laterally**

Answer 37

sclerotome; midline notochord and neural tube; laterally

Question 38

Sclerotome cells surround the neural tube, forming the \_\_\_\_\_ Notochord becomes _____ of intervertebral discs

Answer 38

vertebrae; nucleus pulposis

Question 39

Sclerotome cells that migrate **laterally** form the \_\_\_

Answer 39

ribs

Question 40

\_\_\_\_\_\_\_ Occurs by endochondral ossification (i.e. forms a cartilage model, kills the cartilage, replaces with bone). \_\_\_\_\_ cells form a cartilage model. Later, ossification centers develop. Ossification **does not/does** continue until adulthood.

Answer 40

vertebra develoment; Sclerotome; does

Question 41

Vertebral development is complex. Vertebrae and Spinal nerves develop together. Each sclerotome forming vertebrae has to divide into _____ parts (along the intrasegmental boundary to allow spinal nerves space to exit vertebral column. Cranial and caudal parts of adjacent sclerotomes join and create a \_\_\_\_\_\_

Answer 41

cranial and caudal; VERTEBRA

Question 42

Hemivertebra

Answer 42

Lack of formation of part of a vertebra. Arises from either: * failure of an ossification center to form properly * improper subdivision of sclerotomes The presence of hemivertebra is one cause of scoliosis (lateral curvature of vertebral column).

Question 43

Neural Tube Defects (NTD)

Answer 43

* Also called Spina bifida (= cleft spine) * Mild and moderate forms arise from lack of development of **dorsal vertebral arch** from the sclerotome.

Question 44

Rib Congenital Anomalies

Answer 44

•Usually small, rudimentary rib immediately above or below the 12 normal ribs. **•Lumbar rib** : An extra rib or pair of ribs may develop in the lumbar area from the L1 vertebra. **No symptoms**. **•Cervical rib** : An extra rib or pair of ribs may develop in the cervical area from C7 vertebra. (B) .5-1% of population. **May compress brachial plexus +/- subclavian artery** (this is one etiology of Thoracic outlet syndrome) • **Lumbar are more common than cervical**

Question 45

Myotome cells migrate… **ventrally/dorsally,** to form the intrinsic (deep) back muscles innervated by dorsal rami of spinal nerves. (B,C)

Answer 45

dorsally

Question 46

Myotome cells migrate… **ventrally/dorsally**, to form the anterolateral body wall (and limb muscles) innervated by ventral rami of spinal nerves.

Answer 46

ventrally

Question 47

development of the skull: derived from

Answer 47

mesoderm

Question 48

skull forms from **endochondral/intramembranous ossification**

Answer 48

**intramembranous ossification**

Question 49

intramembranous ossification process

Answer 49

Begins with mesenchymal cells ↓ Mesenchymal cells differentiate directly into bone forming cells = osteoblasts NOTE: there is no cartilage model. ↓ These cells make bone matrix (osteoid). ↓ Flat bones of the skull (C)

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Question 60

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