Physiology of BonePhysiology of BoneCITRA ROSYIDAH

Bone PhysiologyBone Physiology

www.ama-assn.org

Features of a Long Bone:

Epiphysis: Ends of the bone.

Diaphysis: The shaft of the bone which surrounds the medullary cavity.

Articular Cartilage: Cushions the ends of the bones and allows for smooth movement.

Epiphyseal Plate:Areas made of cartilage allowing for the growth of the bone.

Bone cellsBone cellsAs for all connective tissue, bone consists of cells and extracellular matrix. 

There are three types of cells in mature bone tissue: 

OsteoblastsOsteocytesOsteoclasts

FunctionFunctionOsteoblasts 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. 

An osteoclast cell attached to the bone surface. Where it is in contact with the bone it forms a ‘ruffled zone’ under which resorption takes place.

                         

     

MicrostructureMicrostructure of bone tissue 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 phosphate

Ca3 (PO4)2

Functions of bone and Functions of bone and the skeletal systemthe skeletal system

Bone tissue and the skeletal system perform several functions:SupportProtectionMovementMineral homeostasisBlood cell productionTriglyceride storage

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

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

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

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

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

Triglyceride Triglyceride storagestorageTriglycerides 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

RegulationRegulationGrowth hormone (GH): stimulates the liver

to produce insulin-like growth factor 1 (IGF-1), and then IGF-1 promotes cartilage and bone growth

Calcitonin inhibits bone resorption.

RegulationRegulationParathyroid hormone and 1,25-

dihydroxyvitamin D3 stimulate bone resorption.

Estrogen that produced within epiphyseal disc is needed for the disc to seal. Also, estrogen is used for prevention of osteoporosis.