LQB185 Lecture Notes - Lecture 10: Dense Irregular Connective Tissue, Bone Marrow, Hyaline Cartilage
Week 10: The Skeletal System
➢ Skeletal System Functions:
1. Support
2. Protection
3. Assistance in movement
4. Mineral homeostasis (storage and release)- Ca+ and phosphorus,
99% of ody’s aliu
5. Blood cell production- red bon marrow in certain bones produces red
blood cells, white blood cells and platelets (HEMOPOIESIS)
6. Triglyceride storage- yellow bone marrow consists of adipose cells
that store triglycerides (energy reserve)
➢ Diaphysis- oe’s shaft
➢ Epiphyses- proximal and distal ends of the bone
➢ Metaphysis- regions between the diaphysis and the epiphyses
➢ Articular Cartilage- thin layer of hyaline cartilage converging the part of
the epiphysis.
➢ Periosteum- connective tissue sheath that surrounds the bone surface.
Consists of a OUTER fibrous layer of dense irregular connective tissue
and an INNER osteogenic layer of cells.
➢ Medullar Cavity- hollow cylindrical space within the diaphysis that
contains fatty yellow bone marrow and blood vessels. Minimises bone
weight
➢ Endosteum- thin membrane that lines the medullar cavity, single layer
of bone-forming cells and connective tissue.
➢ Extracellular matrix
- 15% water
- 30% collagen fibres
- 55% crystallized mineral salts (mostly calcium phosphate and Calcium
hydroxide= Hydroxyapatite
- This crystalizing causes tissue to harden called Calcification
➢ A oe’s hardness depends on crystallized inorganic mineral salts
➢ A oe’s flexibility depeds o it’s ollage fires
➢ 4 types of cells found in bone tissue
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1. Osteogenic cells- unspecialized bone stem cells, undergo cell division
that develop into osteoblasts
2. Osteoblasts- bone-building cells, secrete collagen fibres and other
organics to build the extracellular matric of bone tissue. They trap
themselves in their own secretion and become osteocytes
3. Osteocytes- mature bone cells, maintain daily metabolism
4. Osteoclasts- huge ells, it’s plasa erae is deeply folded ito a
ruffled border that releases powerful lysosomal enzymes that digest
proteins of extracellular bone matrix= Resorption
➢ Osteoblasts- build bone
➢ Osteoclasts- carve out bone
➢ 80% compact bone, 20% spongy bone
➢ Compact Bone Tissue
- Makes up bulk of diaphysis
- Provides protection and support resists from stresses
- Comprised of repeating structural units called Osteons
- Each Osteons consists of concentric lamellae arranged around a
central canal
- Concentric lamellae are circular plasters of mineralized extracellular
matrix of increasing diameter
➢ Spongy Bone Tissue
- does not contain osteons, provide nourishment to the osteocytes
Blood and nerve supply of bone
➢ Passes into bones from the periosteum
➢ Periosteal arteries enter the diaphysis through perforating canals
➢ Nutrient artery passes through a hole in compact bone called nutrient
foramen
➢ Metaphyseal arteries enter the metaphysis of a long bone
➢ Epiphyseal arteries enter the epiphyses of a long bone
Bone Formation
➢ Bone forms= Ossification/Osteogenesis
➢ 2 ways of bone formation in birth.
1. Intramembranous ossification- bones form directly within
mesenchyme
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Document Summary
Skeletal system functions: support, protection, assistance in movement, mineral homeostasis (storage and release)- ca+ and phosphorus, 99% of (cid:271)ody"s (cid:272)al(cid:272)iu(cid:373: blood cell production- red bon marrow in certain bones produces red blood cells, white blood cells and platelets (hemopoiesis, triglyceride storage- yellow bone marrow consists of adipose cells that store triglycerides (energy reserve) Epiphyses- proximal and distal ends of the bone. Metaphysis- regions between the diaphysis and the epiphyses. Articular cartilage- thin layer of hyaline cartilage converging the part of the epiphysis. Periosteum- connective tissue sheath that surrounds the bone surface. Consists of a outer fibrous layer of dense irregular connective tissue and an inner osteogenic layer of cells. Medullar cavity- hollow cylindrical space within the diaphysis that contains fatty yellow bone marrow and blood vessels. Endosteum- thin membrane that lines the medullar cavity, single layer of bone-forming cells and connective tissue. 55% crystallized mineral salts (mostly calcium phosphate and calcium hydroxide= hydroxyapatite.