Physiology of Bone

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Physiology of Bone

• Dr. Usama ALAlami

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Bone Physiology
www.ama-assn.org
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Bone cells

• As for all connective tissue, bone consists of
  cells and extracellular matrix. 
• There are three types of cells in mature bone
  tissue 
• Osteoblasts
• Osteocytes
• Osteoclasts

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• Osteoblasts and osteocytes are involved in
  deposition of bone matrix
• Osteoblasts are located at the surface of bone
  tissue, whereas osteoclasts are located within
  the calcified matrix 
• Osteoclasts are involved in the resorption of
  bone tissue. 

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Histology of bone tissue

• Like other connective tissues, bone is a matrix
  containing cells as opposed to a structure made
  of cells
• The matrix is made of hydroxyapatite which is
  predominately tricalcium phospahe
• Ca3 (PO4)2

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Bone structure

• A typical long bone (greater length than width)
  consists of the following parts
• The diaphysis. The bones shaft or body
• The epiphyses. The distal and proximal ends of
  the bone
• The metaphyses. Regions in a mature bone where
  the diaphysis joins the epiphyses
• The articular cartilage. This is a thin layer of
  hyaline cartilage

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Functions of bone and the skeletal system

• Bone tissue and the skeletal system perform
  several functions
• Support
• Protection
• Movement
• Mineral homeostasis
• Blood cell production
• Triglyceride storage

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Support

• The skeleton is a structural framework for the
  body supporting soft tissues and provides
  attachment points for the tendons of most
  skeletal muscles

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Protection

• The skeleton protects many internal organs from
  injury. For example, the skull (cranial bones)
  protects the brain and the vertebrae protect the
  spinal cord.

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Movement

• As skeletal muscles attach to bones, when
  muscles contract they pull on bones. Thus,
  muscles and bones can produce movement

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Mineral homeostasis

• Bone tissue stores important minerals,
  especially calcium and phosphorus. Bone releases
  these minerals (on demand) to different parts of
  the body to maintain homeostasis

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Blood cell production

• In some bones, red bone marrow (a connective
  tissue) produces erythrocytes, leucocytes and
  platelets, via a process called haemopoiesis.

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Triglyceride storage

• Triglycerides stored in the adipose cells of
  yellow bone marrow form an important energy
  reserve
• Yellow bone marrow consists mostly of adipose
  cells, which store triglycerides
• In the newborn, all bone marrow is red and is
  involved in haemopoiesis
• As we age, much of the bone marrow changes from
  red to yellow

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• www.eskeletons.org/