Development Flashcards
Derived from paraxial mesoderm
Skeletal muscle
Smooth muscle from ECTODERM
Pupillary, mammary gland and sweat gland muscles
Sphincter and dilator muscles of the pupil, muscle tissue of mammary gland, sweat glands
Smooth muscle differentiates from
Splanchnic mesoderm surrounding the gut and its derivatives
Cardiac muscle differentiates from
Splanchnic mesoderm surrounding the heart tube
From the musculature of the axial skeleton, body wall, limbs and head
Somites and Somitomeres
Striated skeletal muscle from the occipital region caudally.. Somites form and differentiate into
1) sclerotome
2) dermatome
3) 2 muscle forming regions (VLL & DML)
Domain that comprises the regions around the neural tube and contains only somite-derived cells
Primaxial domain
Domain that consists of the parietal layer of lateral plate mesoderm together w/ somite cells that have migrated across the lateral somitic frontier
Abaxial domain
Two muscle forming regions
Dorsolateral region of the somite (VLL) Dorsomedial region (DML)
Dorsolateral region of the somite expresses the muscle specific gene
MyoD
Dorsomedial region expresses the gene
Myf5
Migrates to provide progenitor cells for limb and body wall musculature
Dorsolateral region
Migrates ventral to cells that form dermatome
Dorsomedial region
Also forms the myotome, myf5
Sonic Hedgehog (SHH) is secreted by
1) Notochord
2) floor plate of neural tube
Causes the ventral part of the somite to form sclerotome and express PAX1
SHH
Function of PAX1
Control chondrogenesis and vertebral formation
Activate PAX3 which in turn demarcates dermayotome
WNT PROTEINS
Directs the dorsomedial portion of the somite to form epaxial (back) muscles and express Myf5
WNT PROTEINS
Mid dorsal portion of the somite is directed to become dermis by
Neurotrophin 3 (NT3), expressed by the neural tube
Hypaxial musculature (derived from dorsolateral portion of somite) is influenced by
Wnt proteins and inhibitory BMP-4 protein =activates myoD
Hypaxial musculature
Limb and body wall
Presence of cross striations in skeletal muscle
End of 3rd month
Formation of patterns
Controlled by connective tissue into which myoblast migrate
Head region is derived from
Neural crest cells
Cervical and occipital regions are from
Somatic mesoderm
Origin of body wall and limbs
Somatic mesoderm
Small dorsal portion, formed from the dorsomedial cells of the somite
Epimere
end of 5th week muscle cells are collected into two: epimere and hypomere
Nerve innervating the epimere
Dorsal primary ramus
Nerve innervating the hypomere
Ventral primary ramus
Myoblasts of the epimeres form the
Extensor muscles of vertebral column
Gives rise to muscle of limbs and body wall
Hypomeres
Myoblasts from cervical hypomeres form
Scalene, Genihyoid, prevertebral muscles
All voluntary muscles of the ehad region derived from (includes tongue, eye, pharyngeal arches) .. Except the iris, optic cup ectoderm
Paraxial mesoderm
In the head
Derived from neural crest cells
Limb muscles observed in what week of development?
7th week
Elongation of the limb buds, the muscle tissue splits into
Flexor and extensor components
Form the conducting system of the heart
Purkinje fibers
Muscular system develops from the
Mesodermal germ layer
