Development of Musculoskeletal Systems Flashcards
- Mesoderm accumulates on each side of notochord
- Transverse fissures divide the paraxial mesoderm into blocks progressing from rostral to caudal
- Each block is a somite
- Rostral to the notochord, mesenchyme forms less developed somites called ____
somitomeres
is a gelatinous substance with star shaped
mesenchymal cells
Mesenchyme
connective tissue fiber forming cells and the mature cells are fibrocytes
Fibroblast-
cartilage forming cells
Chondroblast-
Bone forming cells
Osteoblasts-
muscle forming cells
Myoblasts-
- During the ____ in domestic animals, the outlines of somites first become visible
- Differentiation of somites commences around ____
- By the ____, when somite formation is complete, those formed at an earlier stage have undergone further differentiation
third week of gestation
fourth week of gestation
fifth week of gestation
- Ventromedial part
- Forms most of the axial skeleton (vertebrae, ribs, and base of the skull)
Sclerotome
- Dorsolateral part
- Form dermis of the skin
Dermatome
- Middle
- Forms skeletal musculature
Myotome
- Like somites, but smaller and less distinctly organized.
- Develop rostral to the notochord in the head.
- Migrate into pharyngeal arches and form muscles of the jaw, face, pharynx, and larynx.
Somitomeres
Two further regions of the this have been recently postulated:
* Syndetome, from which the tendons rise
* Somite cells that will form the vascular walls of the aorta and the intervertebral blood vessels
somites
type of muscle
Paraxial mesoderm that forms somites
and in the rostral region of the head,
somitomeres
Skeletal muscle
type of muscle
Splanchnic mesoderm
Cardiac muscles and Smooth muscles
type of muscle
Splanchnic mesoderm
Smooth muscles
muscle formation
Myogenesis:
- Fibers : striated, tubular and multi nucleated
- Voluntary
- Usually attached to skeleton
Skeletal muscle
- Fibers : non-striated, spindle-shaped, and uninucleated.
- Involuntary
- Usually covering wall of internal organs.
Smooth muscle
- Fibers: striated, branched and uninucleated.
- Involuntary
- Only covering walls of the heart.
Cardiac muscle
*Which Division of the trunk muscles
Dorsomedial margin
Dorsal trunk muscles
Epaxial myotome
*Which Division of the trunk muscles
Dorsolateral margin
Forms the limb muscles and ventral trunk muscles (diaphragm and abdominal muscles)
Hypaxial muscle
Three distinct lineages generate the skeleton:
Somites
Lateral plate mesoderm
Cranial neural crest
*Three distinct lineages generate the skeleton:
Axial (vertebral) skeleton
Somites
*Three distinct lineages generate the skeleton:
Limb skeleton
Lateral plate mesoderm
*Three distinct lineages generate the skeleton:
Branchial arches
Craniofacial bones and cartilage
Cranial neural crest
Cartilage formation
Chondrogenesis:
Osteogenesis
Two major methods of bone formation:
Intramembranous
Endochondral
- Bone is preformed in a cartilaginous model, after which the cartilage is destroyed by chondroblasts
(cartilage destroying cells)
Endochondral ossification
- Bone is formed in an environment of mesenchymal cells which differentiate into osteoblasts to osteocytes when entrapped by their own secretions
- Clavicle and bones of the skull (flat bones) are examples of bones formed
Intramembranous ossification
Limb development Begins towards the end of the ____ of gestation in cats, sheep and pigs, and during the ____ in dogs and cattle.
third week
fourth week
Development of the fore and hind limbs is similar except that morphogenesis of the hind limbs is approximately ____ behind that of the forelimbs.
1 to 2 days
Limb buds
* From body wall somatopleure
* Bone, cartilage, and connective tissue of the limb arise from the _____ of the limb bud
* Dermis and skeletal muscle come from the ____ and _____ migrations into the limb
somatic mesoderm
dermatome
myotome
*Limb Development
A limb begins as ____.
limb field
*Limb Development
A _____ is produced by localized proliferation and condensation of mesenchyme, covered by ectoderm.
limb bud
*Limb Development
The distal end of the limb bud (____) is flattened like a paddle and ectoderm along its outer margin thickens to form the so-called _____ (AER).
footplate
apical ectodermal ridge
*Limb Development
Regions of the limb develop in ____ as the
limb bud elongates (the shoulder/hip appears first, the manus/pes is the last to be added)
Proximodistal order
*Limb Development
Separation of digits are produced by ____ (species with fewer digits undergo further degeneration and/or fusion of digits)
interdigital necrotic zones
Impaired cell division within growth plates and interfere with endochondral ossification resulting in dwarfism
Achondroplasia
Characterized by extreme fragility of bones
Osteogenesis imperfecta
Characterized by abnormally dense bones
Osteopetrosis
Failure of the left and right vertebral arches to fuse during development of vertebrae
SPINA BIFIDA OCCULTA
Results from the fusion of two or more adjacent vertebrae
BLOCK VERTEBRA
Only one half of a vertebra develops
Usually confined to the thoracolumbar region
HEMIVERTEBRA
A sagittal cleft of the vertebral body is produced that extends through the body dorsoventrally
BUTTERFLY VERTEBRA
Lateral deviation of the vertebral column
Scoliosis
Abnormal ventral curvature of the vertebral column
Lordosis
Abnormal dorsal curvature of the vertebral column
Kyphosis
Abnormal twisting of the cervical vertebrae
TORTICOLLIS/ WRY NECK
Presence of one or more extra digit
POLYDACTYLY
Partial or complete duplication of one limb
BIMELIA
Limbs growing from the back
NOTOMELIA
Ectopic limb projecting from the perineum
PERINEOMELIA
Complete absence of limbs
AMELIA
Partial or complete absence of a limb or its parts
ECTROMELIA
A limb reduced in size but all its parts are present
Eg. dwarf
MICROMELIA
Absence of all or part of the distal half of the limb
HEMIMELIA
Absence of the proximal portion of a limb or limbs, the distal part being attached to the trunk by a small, irregularly shaped bone
PHOCOMELIA
Fusion of the claws or digits
SYNDACTYLY/ SYNDACTYLYISM
Shortened digits
BRACHYDACTYLY
Absence of all or any part of a digit
ECTRODACTYLY/ ECTRODACTYLIA
Affected animals exhibit joints in abnormal positions Most frequently reported in cattle, particularly the Charolais
ARTHROGRYPOSIS
- Abnormal maturation of the hip joint
- Most commonly reported in large muscular breeds of dog like the German Shepherd, Golden Retriever, or Mastiffs
Hip dysplasia
- Double muscle phenotype
- Primary results from an increase in the number of muscle fibers
- Belgian Blue and Piedmontese cattle have
mutations of the myostatin gene
Muscular hypertrophy
