Embryology; Musculoskeletal System

Question 1

The skeletal system originates from ______ and _____ ____ cells, which revert to a _______ state

Answer 1

mesoderm
neural crest
mesenchymal

Question 2

The mesenchymal cells will differentiate into ________ or _______ to eventually form bone

Answer 2

osteoblasts

chondroblasts

Question 3

The ________ model of ossification begins with mesenchyme —> chondroblasts —-> cartilage —–> bone

Answer 3

endochondral

Question 4

The _______ model of ossification beings with mesenchymal cells —–> osteoblasts ——> bone

Answer 4

intramembranous

Question 5

True or False

The endochondral method of ossification ultimately forms the facial bones (viscerocranium), and some flat bones of skull

Answer 5

False; the endochondral method forms most bones; limbs and base of skull (chondrocranium)
The intramembraneous method forms the facial bones and flat skull bones

Question 6

The formation of joints appears at week _____, as condensed mesenchyme appears in _____ ______

Answer 6

6

joint interzones

Question 7

Name the three types of joints

Answer 7

fibrous (sutures)
cartilaginous (costochondral joints)
synovial (knee)

Question 8

The _____ _____ is the space between bones that will become the joint

Answer 8

joint interzone

Question 9

_____ _____ forms the majority of the axial skeleton (except for the sternum and a portion of the skull) and the somites (which form at day 23)

Answer 9

Paraxial mesoderm (sclerotome)

Question 10

Each somite differentiates into a ________, _______, and ______

Answer 10

dermatome
myotome (muscle)
sclerotome

Question 11

Sclerotome cells surround the _____ _____ and _____

Answer 11

neural tube

notochord

Question 12

Each sclerotome segment (forming vertebrae) has a less dense portion _____ and a dense portion _____

Answer 12

cranially

caudally

Question 13

Sclerotomes undergo ________; some of the dense portion forms ______ ______ of intervertebral discs, remaining dense portion fuses with less dense portion of sclerotome immediately inferior to form the ______ ______

Answer 13

resegmentation
annulus fibrosus
vertebral body

Question 14

The _____ ______ _____ break through the sclerotomes from the neural tube and separates the dense from not dense portion and giving rise to the _______ ____

Answer 14

cervical spinal nerves

intervertebral discs

Question 15

There are ____ cervical sclerotomes which give rise to _____ cervical vertebrae and ______ cervical spinal pairs

Answer 15

8
7
8

Question 16

True of False

The cranial and caudal portions of adjacent sclerotomes fuse to form each vertebral body

Answer 16

True; the caudal portion of one fuses with the cranial portion of another

Question 17

_______ are formed from sclerotome of paraxial mesoderm. Grow out as lateral extensions of _______ _______ developing from thoracic vertebrae and wrap around anteriorly

Answer 17

Ribs

costal processes

Question 18

_____ _____ form where costal process meets vertebrae (due to apoptosis of cells)

Answer 18

synovial joints

Question 19

_______ is induced to form by ribs at ventral midline from _____ _____ _____ ______

Answer 19

sternum

lateral plate somatic mesoderm

Question 20

True or False

The sternum forms as one unit

Answer 20

False; the sternum develops as two bars that will fuse cranially to caudally

Question 21

True or False

The sternum is formed during the 10th week

Answer 21

True

Question 22

The primary curvatures of the spine are the ______ and _______, and they develop duing the _____ period

Answer 22

thoracic
sacral
fetal

Question 23

The secondary curvatures of the sone are the _____ and ______, and they develop ____ ____

Answer 23

cervical
lumbar
after birth

Question 24

The ________ is mostly formed from the neural crest of the first _____ pharyngeal arches, and is formed by __________ ossification

Answer 24

viscerocranium
two
intramembranous

Question 25

______ are fibrous joints uniting the flat bones of the skull, during fetal period, are membraneous and flexible joints

Answer 25

sutures

Question 26

_______ are enlarged membraneous spaces where 2+ bones meet

Answer 26

fontanelles

Question 27

The sutures and fontanelles fuse at ___-___ years

Answer 27

5-7

Question 28

__________ is the premature closure of sutures

Answer 28

craniosynostosis

Question 29

True or False | brachycephaly is the premature closing of the sagital suture

Answer 29

False; brachycephaly is the premature closing of the coronol suture; scaphocephaly is the premature closing of the sagital suture

Question 30

The appendicular skeleton arises from _____ cartilage, which differentiates from mesenchyme of lateral plate somatic mesoderm

Answer 30

hyaline

Question 31

Endochondral ossification of limb bones begins at the end of embryonic period; end of the _____ week

Answer 31

8th

Question 32

The bones of the face (viscerocranium) and a portion of neurocranium (frontal, squamous portion of temporal, anterior sphenoid), and hyoid form from mesenchyme deriving from _______ ______

Answer 32

neural crest

Question 33

The vertebral column, ribs + portion of neurocranium (occipital, parietal, petrous portion of temporal, posterior sphenoid) form from mesenchyme deriving from ______ ______

Answer 33

paraxial mesoderm (sclerotome)

Question 34

The pectoral and pelvic girdles, limb bones, and sternum (aka appendicular skeleton and sternum) form from mesenchyme derived from ______ ______ _______

Answer 34

lateral plate mesoderm

Question 35

Skeletal muscles are derived from _____ _____, of the somites, but specifically ______

Answer 35

paraxial mesoderm | myotome

Question 36

Cardiac muscle is derived from _______ _______ ______ surrounding developing heart

Answer 36

intraembryonic splanchnic mesoderm

Question 37

Smooth muscle (of GI tract) is derived from ______ _______ ______ surrounding gut tube

Answer 37

intraembryonic splanchnic mesoderm

Question 38

Smooth muscles such as _______ _____ and _____ ______ of the iris arise from __________

Answer 38

sphincter pupillae dilator pupillae neuroectoderm

Question 39

Smooth muscles such as ______ ______ of mammary, salivary and sweat glands arise from _____ _______

Answer 39

myoepithelial cells | surface ectoderm

Question 40

Somites (paraxial mesoderm) give rise to most of the axial skeleton and _______ ______ + overlong dermis of back

Answer 40

associated musculature

Question 41

_____ ______ ______ separates paraxial mesoderm from lateral plate somatic mesoderm

Answer 41

lateral somitic frontier

Question 42

Some ventrolateral lip (VLL) myoblasts will migrate across the frontier into lateral plate somatic mesoderm to form ______ _____ of the ______

Answer 42

skeletal muscle | limb

Question 43

Each myotome divides into _____ group and _____ group

Answer 43

``` epaxial group (dorsal) hypaxial group (ventral) ```

Question 44

Each spinal nerve divides into a _______ and _______ primary rams

Answer 44

ventral | dorsal

Question 45

True or False | Epaxial muscles are innervated by ventral primary rami

Answer 45

False; the dorsal primary rams innervates the epaxial muscles; the ventral primary rami innervates the hypxial muscles

Question 46

Deep intrinsic back muscles are ______ muscles

Answer 46

epaxial

Question 47

The muscle belly of skeletal muscle forms from the ______ _____, while the muscle tendons from from _____ _____ near myotomes

Answer 47

paraxial mesoderm | sclerotome cells

Question 48

All muscles are derived from ______ (except those few from ectoderm)

Answer 48

mesoderm

Question 49

Limb buds emerge toward end of week ______

Answer 49

4

Question 50

True or False | The upper limbs appear before the lower limbs

Answer 50

True; lower limbs appear roughly 1-2 days after upper limbs

Question 51

Limb buds have a core of ______ lined by _____ ______

Answer 51

mesenchyme | surface ectoderm

Question 52

The mesenchyme of limb buds forms the ____ of the limb

Answer 52

connective tissue (blood, bone, cartilage, dermis, etc)

Question 53

______ ______ _____ sends signaling factors to nearby mesenchyme of ______ _____; it is located at tip of new limb

Answer 53

apical ectodermal ridge (AER) | progress zone

Question 54

The _____ _____ keeps cells undifferentiated and rapidly dividing to form more limb tissue;

Answer 54

progress zone

Question 55

Limb buds initially grow straight out laterally, followed by a upper limb _____ rotation by 90º an lower limb _______ rotation by 90º

Answer 55

lateral | medial

Question 56

By the end of week ___, mesenchyme is condensing to form ____ ______

Answer 56

``` 6 digital rays (outlines of future digits) ```

Question 57

Organized ______ of cells in AER divides paddle into 5 digits; the _______ will differentiate as ______ cartilage in digits

Answer 57

mesenchyme | hyaline

Question 58

The digits are fully separated by week ____

Answer 58

8

Question 59

The absence of part of a limb

Answer 59

meromelia

Question 60

the absence of an entire limb

Answer 60

amelia

Question 61

Fewer digits

Answer 61

syndactyly

Question 62

Between 1957 and 1962, the role of the drug _______ was causing an absence or malformation of long bones of limbs

Answer 62

thalidomide