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Bone and cartilage, The most characteristic feature of compact bone is…
Bone and cartilage
Histology of Bone
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- Surrounded by matrix (25%water, 25% protein 50 % mineral salts
- 4 cell types that make up osseous tissue
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Shape of Bones
Long bones e.g. humerus, femur
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Sesamoid e.g. patella, pisiform
Pneumatic e.g. frontal, sphenoid, ethmoid, maxilla
Irregular bones e.g. vertebrae, hip bones
Short bones e.g. carpals, tarsals
Flat bones e.g. rib, sternum, scapula, parietal
Functions
Movement (provide leverage/support system for skeletal muscles, tendons, ligaments and joints)
Mineral homeostasis (bones act as reserves of minerals important for the body like calcium and phosphorus)
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- The most characteristic feature of compact bone is lamella structure
- In the intervals between the lamellae lie osteocytes in lacunae
- the lamella are arranged in 3 series
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Perichondrium
A dense membrane of connective tissue that covers cartilage in different parts of the body EXCEPT for the cartilage of the joints
Functions
The perichondrium is both fibrous and porous in nature. Because of this, blood flow is easily facilitated. It helps transport oxygen from one part of the body to another
Apart from this, nutrients are also supplied to the different parts of the body. This helps nourish the cartilage and keeps it strong and healthy.
Protects growing and developing bones against any trauma or injury. It is basically a protective membrane and in case an injury does occur, it promotes cellular regeneration which helps in fast recovery
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- derived from mesenchyme
- all connective tissue is derived
- unspecialized stem cells
- undergo mitosis and develop into osteoblasts
- found in the (inner portion of periosteum, endosteum & canals (perforating and central) in bone that contain blood vessels
- believed to develop from circulating monocytes
- multinucleated giant cell
- settle on the surfaces of bone
- function in bone resorption(destruction of matrix)-important in the development,growth, maintenance and repair of bone
- derived from osteoblast
- principle cells of bone tissue
- no mitotic potential
- do not secrete matrix material
- maintain daily cellular activities of bone tissue .e.g. exchange of nutrients and wastes with the blood
- derived from osteogenic cells
- found on the surface of the bone
- no ability to mitotically divide
- secrete collagen and their organic components needed to build bone tissue
- Has active and inactive osteoblasts
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- covered externally by periosteum and internally its cavities are filled with marrow and is lined by a thin endosteum
- structural elements are composed of bone cells/osteocytes embedded within calcified matrix in spaces called lacunae
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- Chnodrocytes : cartilage producing cells
- Lacunae: small cavities where the chondrocytes are encased
- Extracellular matrix : jellylike ground substance
- Perichondrium : layer of dense irregular connective tissue that surrounds the cartilage
- Avascular, nourished by diffusion
- No lymph vessels/ nerves
Fibrous in nature and is made of dense connective tissue. It contains fibroblasts which secrete collagen
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- occurs from chondrogenic cells in the perichondrium differentiating into chondroblasts,
- Later, forming a new layer of cartilage around the peripheral of the existing cartilage
- Occurs only in young cartilage from cell divisions within cartilage. This process increases the length of cartilage.
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- The process is called ossification
- Occurs in 4 situations
- bone continually renews itself
- never metabolically at rest
- enables Ca to be pulled from bone when blood levels are low
- osteoclasts are responsible for matrix destruction
- produce lysosomal enzymes and acids
- spongy bone replaced every 3-4 years
- compact bone every 10 years
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- Cartilage formation and ossification occurs during 6-8th week of embryonic development
- Flat bones of the skull and mandible; clavicle are formed in this way
- "Soft spots' that help fetal skull pass through the birth canal later become ossified forming the skull
- The replacement of cartilage by bone
- Most bones of the body are formed in this way including long bones