Embryology; Musculoskeletal System Flashcards
The skeletal system originates from ______ and _____ ____ cells, which revert to a _______ state
mesoderm
neural crest
mesenchymal
The mesenchymal cells will differentiate into ________ or _______ to eventually form bone
osteoblasts
chondroblasts
The ________ model of ossification begins with mesenchyme —> chondroblasts —-> cartilage —–> bone
endochondral
The _______ model of ossification beings with mesenchymal cells —–> osteoblasts ——> bone
intramembranous
True or False
The endochondral method of ossification ultimately forms the facial bones (viscerocranium), and some flat bones of skull
False; the endochondral method forms most bones; limbs and base of skull (chondrocranium)
The intramembraneous method forms the facial bones and flat skull bones
The formation of joints appears at week _____, as condensed mesenchyme appears in _____ ______
6
joint interzones
Name the three types of joints
fibrous (sutures)
cartilaginous (costochondral joints)
synovial (knee)
The _____ _____ is the space between bones that will become the joint
joint interzone
_____ _____ 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)
Paraxial mesoderm (sclerotome)
Each somite differentiates into a ________, _______, and ______
dermatome
myotome (muscle)
sclerotome
Sclerotome cells surround the _____ _____ and _____
neural tube
notochord
Each sclerotome segment (forming vertebrae) has a less dense portion _____ and a dense portion _____
cranially
caudally
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 ______ ______
resegmentation
annulus fibrosus
vertebral body
The _____ ______ _____ break through the sclerotomes from the neural tube and separates the dense from not dense portion and giving rise to the _______ ____
cervical spinal nerves
intervertebral discs
There are ____ cervical sclerotomes which give rise to _____ cervical vertebrae and ______ cervical spinal pairs
8
7
8
True of False
The cranial and caudal portions of adjacent sclerotomes fuse to form each vertebral body
True; the caudal portion of one fuses with the cranial portion of another
_______ are formed from sclerotome of paraxial mesoderm. Grow out as lateral extensions of _______ _______ developing from thoracic vertebrae and wrap around anteriorly
Ribs
costal processes
_____ _____ form where costal process meets vertebrae (due to apoptosis of cells)
synovial joints
_______ is induced to form by ribs at ventral midline from _____ _____ _____ ______
sternum
lateral plate somatic mesoderm
True or False
The sternum forms as one unit
False; the sternum develops as two bars that will fuse cranially to caudally
True or False
The sternum is formed during the 10th week
True
The primary curvatures of the spine are the ______ and _______, and they develop duing the _____ period
thoracic
sacral
fetal
The secondary curvatures of the sone are the _____ and ______, and they develop ____ ____
cervical
lumbar
after birth
The ________ is mostly formed from the neural crest of the first _____ pharyngeal arches, and is formed by __________ ossification
viscerocranium
two
intramembranous
______ are fibrous joints uniting the flat bones of the skull, during fetal period, are membraneous and flexible joints
sutures
_______ are enlarged membraneous spaces where 2+ bones meet
fontanelles
The sutures and fontanelles fuse at ___-___ years
5-7
__________ is the premature closure of sutures
craniosynostosis
True or False
brachycephaly is the premature closing of the sagital suture
False; brachycephaly is the premature closing of the coronol suture; scaphocephaly is the premature closing of the sagital suture
The appendicular skeleton arises from _____ cartilage, which differentiates from mesenchyme of lateral plate somatic mesoderm
hyaline
Endochondral ossification of limb bones begins at the end of embryonic period; end of the _____ week
8th
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 _______ ______
neural crest
The vertebral column, ribs + portion of neurocranium (occipital, parietal, petrous portion of temporal, posterior sphenoid) form from mesenchyme deriving from ______ ______
paraxial mesoderm (sclerotome)
The pectoral and pelvic girdles, limb bones, and sternum (aka appendicular skeleton and sternum) form from mesenchyme derived from ______ ______ _______
lateral plate mesoderm
Skeletal muscles are derived from _____ _____, of the somites, but specifically ______
paraxial mesoderm
myotome
Cardiac muscle is derived from _______ _______ ______ surrounding developing heart
intraembryonic splanchnic mesoderm
Smooth muscle (of GI tract) is derived from ______ _______ ______ surrounding gut tube
intraembryonic splanchnic mesoderm
Smooth muscles such as _______ _____ and _____ ______ of the iris arise from __________
sphincter pupillae
dilator pupillae
neuroectoderm
Smooth muscles such as ______ ______ of mammary, salivary and sweat glands arise from _____ _______
myoepithelial cells
surface ectoderm
Somites (paraxial mesoderm) give rise to most of the axial skeleton and _______ ______ + overlong dermis of back
associated musculature
_____ ______ ______ separates paraxial mesoderm from lateral plate somatic mesoderm
lateral somitic frontier
Some ventrolateral lip (VLL) myoblasts will migrate across the frontier into lateral plate somatic mesoderm to form ______ _____ of the ______
skeletal muscle
limb
Each myotome divides into _____ group and _____ group
epaxial group (dorsal) hypaxial group (ventral)
Each spinal nerve divides into a _______ and _______ primary rams
ventral
dorsal
True or False
Epaxial muscles are innervated by ventral primary rami
False; the dorsal primary rams innervates the epaxial muscles; the ventral primary rami innervates the hypxial muscles
Deep intrinsic back muscles are ______ muscles
epaxial
The muscle belly of skeletal muscle forms from the ______ _____, while the muscle tendons from from _____ _____ near myotomes
paraxial mesoderm
sclerotome cells
All muscles are derived from ______ (except those few from ectoderm)
mesoderm
Limb buds emerge toward end of week ______
4
True or False
The upper limbs appear before the lower limbs
True; lower limbs appear roughly 1-2 days after upper limbs
Limb buds have a core of ______ lined by _____ ______
mesenchyme
surface ectoderm
The mesenchyme of limb buds forms the ____ of the limb
connective tissue (blood, bone, cartilage, dermis, etc)
______ ______ _____ sends signaling factors to nearby mesenchyme of ______ _____; it is located at tip of new limb
apical ectodermal ridge (AER)
progress zone
The _____ _____ keeps cells undifferentiated and rapidly dividing to form more limb tissue;
progress zone
Limb buds initially grow straight out laterally, followed by a upper limb _____ rotation by 90º an lower limb _______ rotation by 90º
lateral
medial
By the end of week ___, mesenchyme is condensing to form ____ ______
6 digital rays (outlines of future digits)
Organized ______ of cells in AER divides paddle into 5 digits; the _______ will differentiate as ______ cartilage in digits
mesenchyme
hyaline
The digits are fully separated by week ____
8
The absence of part of a limb
meromelia
the absence of an entire limb
amelia
Fewer digits
syndactyly
Between 1957 and 1962, the role of the drug _______ was causing an absence or malformation of long bones of limbs
thalidomide
