Bone

Main points in this lecture

• To identify the Specialized form of connective tissue and describe their functions.

• Different bone cells must be known .

• To Differentiate the types of bone .

• Nice to know some term of changes in bone , and must remember at least 2 of them .

• Bones are :

• Specialized form of connective tissue:

• mineralized collagen matrix, therefore very

• rigid and strong while still retaining some

• degree of flexibility

Function of Bones

1. Protection- of soft tissues and organs. 2. Movement – muscles attached to bones

,contraction causes movement.

3. Storage – of minerals (Calcium and Phosphorous) and lipids ( yellow marrow)

4. Blood Cell Formation- hematopoiesis- occurs within the marrow of the bone.

5. Support- for the entire body; Individual bones provide a framework for attachment of soft tissues and organs.

• Matrix composed:

• 1. organic compound: protein- polysaccharides containing condroitin sulfate

• 2. Inorganic component: calcium, phosphate and calcium carbonate with small amount of mangnesium, fluoride, sulfate. The organic matter in bone matrix is type I collagen and ground substance

• Specialized CT

• •Cells of bone :

• –Osteoblasts

• –Osteocytes

• –Osteoclasts

• •Bone matrix

–Calcified material, lacunae

• •And more….

• –Canaliculi

• –Periosteum

• –Endosteum

Types of Bone Cells

• 1. Osteoblasts:(mononucleated) are responsible for synthesis of the organic components of bone matrix (type I collagen) .

• 2. Osteocytes: (mononucleated )which derive from osteoblasts lie in the lacunae situated between matrix, cylindrical matrix canaliculi house cytoplasmic processes of osteocytes.

• 3. osteoclasts:(multinucleated) are very large branched motile cells. Contain from 5 to 50 nuclei. Osteoclasts lie within enzymatically atched depressions in the matrix .

Structures of a Long Bone • Periosteum

– Outside covering of the diaphysis

– Fibrous connective tissue membrane

• Sharpey’s fibers – Secure periosteum to

underlying bone. – play important roles in bone

histogenesis and in the healing of fractures

• Arteries – Supply bone cells with

nutrients

Types of bone

• 1. compact bone

• 2. cancellons ( spongy) bone

Bones of the Human Body • The adult skeleton has 206 bones

• Two basic types of bone tissue

– Compact bone

• Long Bones

– - Spongy bone

• Short Bones

• Many open spaces

Bone tissue cell types

Compact bone

• Osteon (Haversian System) – A unit of bone

• Central (Haversian) canal – Opening in the center of an osteon

– Carries blood vessels and nerves

• Perforating (Volkman’s) canal – Canal perpendicular to the central canal

– Carries blood vessels and nerves

Bone

Tissue

Microscopic Anatomy of Bone

Microscopic Anatomy of compact Bone

• Canaliculi

– Tiny canals

– Radiate from the central canal to lacunae

– Form a transport system

Microscopic Anatomy of compact Bone

• Lacunae

– Cavities containing bone cells (osteocytes)

– Arranged in concentric rings

• Lamellae

– Rings around the central canal

– Sites of lacunae

Histology of compact bone

Terminology of changes in bone

• osteopenia: decreased calcification or density of bone • • osteoporosis: progressive reduction in quantity of bone • • osteopetrosis: excessive formation of dense trabecular

bone • • osteosclerosis: abnormal hardening or eburnation of

bone • • osteohypertrophy: overgrowth of bone • • osteosarcoma: tumor of the bone • • osteochondrodysplasia: extreme bending of long bones • • osteochondroma (exostosis): benign cartilaginous neoplasma • • osteoblastoma: benign tumor of osteoblasts

Pathological changes of the joints • arthrosis: general term for degenerative affection of a joint • rheumatoid arthritis: systemic disease affecting connective tissue of joint, accompanied by inflammation and erosion of cartilage and bone due to synovial overgrowth • osteoarthritis: destruction of joints due to erosions of articular cartilage, accompanied by inflammation, eburnation of subchondral bone • gout: inflammation of the joint • synovitis: inflammation of synovial membrane • bursitis: inflammation of bursa (german: Schleimbeutel)

Anatomy of a Long Bone

summary • Bones are specialized form of connective tissue

composed of cells and matrix with organic and inorganic component . Bones covered by layer of collagen fibers.

• There are tow kind of bones and their cells , also some terms of changes in bone and Pathological changes of the joints .