Development of the Musculoskeletal System Flashcards
What is included in the axial skeletal system?
Ribs, vertebra, sternum, and skull
What is included in the appendicular skeleton?
Pectoral girdle, pelvic girdle, and limb bones
What are the two divisions of mesoderm that the skeletal system is derived from?
Paraxial mesoderm (somites), and lateral plate somatic mesoderm
Paraxial mesoderm differentiates into what?
Mesenchyme then vertebral column, ribs, and neurocranium
Lateral plate somatic mesoderm differentiates into what?
Mesenchyme then pectoral girdle, pelvic girdle, ribs, and sternum (appendicular skeleton)
Neural crest cells differentiates i
Mesenchyme then viscerocranium and hyoid bone
What is all of the axial skeleton derived from, except what exception?
Sclerotome forms all of the axial skeleton except the sternum and a portion of the skull
The nucleus pulposus is derived from what?
The notocord
At the fourth week of development the sclerotome cells do what?
Surround the neural tube and notocord
How are each sclerotomes divided?
A less dense cranial portion and a dense caudal portion
The dense portion of the sclerotome form what?
Annulous fibrosus of IV discs
The dense portion of a sclerotome fuses with what structure to form what?
The less dense portion of the sclerotome immediately inferior to form the vertebral body
When does chondrification of the vertebral bodies occur?
6th week
When does ossification of vertebral bodies begin?
7th week
When do vertebral arch halves fuse?
3-5 years
When does the vertebral arch fuse with the body?
3-6 years
When is ossification of vertebral bodies complete?
About 25 years
The sclerotome differentiates into what that will become the annulous fibrosus?
Intersegmental mesenchyme
The sternum starts off as what two things that will fuse cranial to caudal?
Sternal bars
What is the neurocranium?
Bones that encase the brain
Where is the viscerocranium?
Anterolateral facial bones
What parts of the skull are formed by endochondral ossification?
Sphenoid, petrous portion of temporal bone, portion of occipital bone
How is the rest of the skull formed that does not develop from endochondral ossification?
Intramembranous ossificaiton
Intramembranous ossification forms what kind of bones that surround the brain?
Flat bones
Where is the cartilaginous neurocranium?
Base of the skull
Where is the membranous neurocranium?
Flat bones that surround the brain
The bregma takes place of what in a newborn?
The anterior fontanelle
The pterion takes place of what in a newborn?
Anterolateral or sphenoidal fontanelle
The lambda takes place of what in a newborn?
Posterior fontanelle
What fontanelle in a newborn does not have a special name that takes its place?
Posteriolateral or mastoid fontanelle
When does ossification of long bones begin?
7/8th week
Skeletal muscle is derived from what?
Paraxial mesoderm
Cardiac muscle is derived from what?
Intraembryonic splanchnic mesoderm surrounding developing heart
Smooth muscle of the GI tract is derived from what?
Intraembryonic splanchnic mesoderm surrounding gut tube
Somites give rise to what?
Axial skeleton (most), Associated musculature, Overlying dermis of back
Somites differentiate into what three initial things?
Sclerotome, myotome, and dermatome
What are myoblasts?
Specialized mesoderm cells that fuse together to form skeletal muscle and can actively contract by week seven
Progenitor cells for muscle tissues derived from the 1)________ and 2)________ lips of the 3)________
1) Ventrolateral
2) Dorsalmedial
3) Dermomyotome
What separates the paraxial mesoderm from lateral plate somatic mesoderm?
Lateral somitic frontier
What domain surrounds neural tube and contains only somite-derived cells?
Primaxial domain
What domain is the parietal layer of lateral plate mesodem with somite-derived cells
Abaxial domain
The ventrolateral lip cells left at the myotome will form what?
Musculature of the back, Shoulder girdle muscles, Intercostal muscles
Most Ventrolateral lip (VLL) myoblasts migrate across the frontier into lateral plate somatic mesoderm to form what?
Infrahyoid muscles, Pectoralis major & minor muscles, Abdominal wall muscles, and Limb muscles
Each myotome divides into what two things?
Epaxial group (dorsal/posterior)(back) and hypaxial group (ventral/anterior)(includes limbs)
Each spinal nerve divides into what two things?
Dorsal primary ramus and ventral primary ramus
The sphincter pupillae m. and dilator pupillae m. of the iris are developed from what?
Neuroectoderm
Myoepithelial cells of mammary, salivary, & sweat glands are derived from what?
Surface ectoderm
Limb buds emerge around the end of what week?
4th
Do upper or lower limbs develop first?
Upper followed by lower 1-2 days later
What is the distal most end of a developing limb called?
Apical ectodermal ridge (AER)
Just proximal to the AER is what zone of the developing limb?
Progress zone
Melanocytes of the developing limb come from what?
Neural crest
Sensory axons and Schwann cells of the developing limb come from what?
Neural crest
Myoblasts of the developing limb come from what?
From myotome of VLL
Motor axons of the developing limb come from what?
From neural tube
When does limb rotation occur?
Week seven
How do the upper limbs developmentally rotate?
Lateral rotation of 90 degrees
How do the lower limbs developmentally rotate?
Medial rotation of 90 degrees
When is the paddle stage of limb development?
6th week
What are digital rays?
Outlines of future digits
When will a fetus have fully developed digits?
End of eighth week
What is meromelia?
Absence of part of a limb
What is amelia?
Absence of an entire limb (absence of AER)
What is polydactyly?
Extra digits
What is syndactyly?
Two or more fused digits
