BMS2011 Lecture Notes - Lecture 4: Muscular System, Synovial Joint, Medullary Cavity
30 May 2018
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Week 2. Musculoskeletal and Axial
Musculoskeletal system
MUSCULOSKELETAL SYSTEM
• Skeletal tissues and muscles are derived from mesoderm
Paraxial -> somite -> dermatome (dermis/epidermis), myotome (muscle), sclerotome
(bone/cartilage)
• Both blood and bone are connective tissue, what differentiates them is composition of
extracellular matrix
• Bone: tissue composition:
o 1. Fibres (organic): collagen, provides tensile strength
o 2. Ground substance (extracellular matrix: inorganic): calcium phosphate, hydroxide and
carbonate -> forms hydroxyapatite crystals (mineral components), most of compressive
strength
o Osteoblasts: cells that produce extracellular matrix (osteoid), found on surface of any
developing bone area
-original cell, creates bone
o Osteocytes: osteoblasts that have become surrounded by matrix, lie in space within matrix
called lacunae (maintain bone matrix)
-mature cell surrounded by osteoid
o Osteoclasts: capable of degrading and reabsorbing matrix, found on surface of any bone
undergoing remodelling
-destroys bone
• Bones are alive, receive nutrients through diffusion
find more resources at oneclass.com
find more resources at oneclass.com
• Bone tissue organisation:
Compact (Lamellar) bone
o Osteon (haversian system) consists of:
o Central haversian canal and lamellae (concentric rings)
-blood vessels and nerves inside (blood supply for cells)
-osteocytes between lamellae
o Lacunae: spaces between lamellae containing osteocytes
-like a lake
o Canaliculi: canals radiating from lacunae
-channels between adjacent cells
o Perforatig Volka’s caals: join osteon central
canals (perpendicular)
Spongy (Trabecullar) bone
o Lamellae form trabeculae (branching plates) not osteons
-no canals/haversian
o Nutrients via diffusion along canaliculi from the endosteum
o Red bone marrow in proximal humerus and femur, vertebrae,
sternum, ribs and pelvis (used as nursery for differentiation of cells
eg. RBC, WBC)
o Organised to minimise stress and strain
(there are internal pathways that follow the way that loads are
being born in the joints)
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find more resources at oneclass.com
• Bone tissue variation: classification
Long
o Elongated shaft and enlarged end
o Eg. humerus, femur, tibia
o Landmarks and regions:
o Diaphysis: cylinder of compact bone (shaft) with medullary cavity (yellow
marrow, fat -> makes it long)
-hollow inside
o Metaphysis: between diaphysis and epiphysis
-band of cartilage serving as growth plate
-stays open during growth
o Epiphysis: enlarged end with compact and trabeculae bone: supports
articular cartilage
-end of bone, smooth appearance
o When diaphysis and epiphysis connect -> stop growing
Irregular
o Complex shape
o Eg. vertebrae and some skull bones
Short
o Geometrically equivalent in all directions
o Eg. carpals and tarsals
Flat
o Parallel layers of compact bone with trabecular
o Eg. cranium, sternum, ribs, scapula
Sesamoid
o Develop in tendons
o Eg. patella
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Musculoskeletal system: skeletal tissues and muscles are derived from mesoderm. Paraxial -> somite -> dermatome (dermis/epidermis), myotome (muscle), sclerotome (bone/cartilage: both blood and bone are connective tissue, what differentiates them is composition of extracellular matrix, bone: tissue composition, 1. Fibres (organic): collagen, provides tensile strength: 2. Ground substance (extracellular matrix: inorganic): calcium phosphate, hydroxide and carbonate -> forms hydroxyapatite crystals (mineral components), most of compressive strength: osteoblasts: cells that produce extracellular matrix (osteoid), found on surface of any developing bone area. Original cell, creates bone: osteocytes: osteoblasts that have become surrounded by matrix, lie in space within matrix called lacunae (maintain bone matrix) Mature cell surrounded by osteoid: osteoclasts: capable of degrading and reabsorbing matrix, found on surface of any bone undergoing remodelling. Destroys bone: bones are alive, receive nutrients through diffusion, bone tissue organisation: Compact (lamellar) bone: osteon (haversian system) consists of, central haversian canal and lamellae (concentric rings) Blood vessels and nerves inside (blood supply for cells)
