Chapter 5 Skeletal System Organization Bones is composed

Chapter 5 Skeletal System

Organization • Bones is composed of osseous tissue. Bones comprise the skeleton. • The skeleton functions in: – Support – Protection – Movement – Storage

Organization • The skeleton is comprised of 206 bones divided into sections: – Axial: head, neck, and trunk TOTAL: approx. 80 • Skull – two sets of bones: Cranium (8) & Facial bones (14) • Hyoid Bone • Vertebral Column (24 vertebrae, Sacrum (5 fused), Coccyx (4 fused) • Sternum, Ribs (12 pairs) – Appendicular: limbs and connecting bones TOTAL: 126 • • Pectoral Girdle: clavicle & scapula Bones of the arm – 30 bones Pelvic Girdle: 2 coxal bones Bones of the leg – 29 bones

Bone Structure • Long bones are the most common in the skeletal system. Their major parts are: – Externally • • Diaphysis – shaft – compact bone Periosteum – covers shaft – connective tissue Epiphysis – ends – spongy bone Articular cartilage – covers ends - connective tissue – Internally • Medullary cavity – Yellow marrow – adipose tissue – Red marrow – red blood cells • Matrix – Osteocytes (mature bone cells)

Bone tissue • There are two types of bone tissue found within long bones: – Compact bone – dense & looks smooth – Spongy bone – small needlelike pieces of bone & lots of open space

Bone Tissue • Microscopic structure of compact bone: – Compact bone contains a matrix where the bone cells live. It is composed of collagen, phosphorus, calcium, and magnesium. – There are tiny chambers within the matrix called lacunae where the mature bone cells live. These mature bone cells are called osteocytes. The osteocytes are connected to each other through tiny canals called the canaliculi. – The osteocytes form rings called the osteon (matrix) around canals that house blood vessels and nerves. These canals are called Haversian canals are connected to each other by Volkmann’s canal.

Bone Development & Growth • The formation of bone is called ossification. • There are two types of bones in the skeleton as far as growth is connected: – Intramembranous (flat bones – form from flat connective tissue) – Endochondral (all other bones)

Bone Development & Growth • All bones start as hyaline cartilage. Within a long bone there are two areas of growth. – Appositional growth – increase in diameter – Interstitial growth – increase in length • The epiphyseal plate, also known as the growth plate, is found between the epiphysis and the diaphysis of a long bone. In this area bone cells ossify and growth in length occurs. These growing bone cells are called OSTEOBLASTS (bone forming cells). • CARTILAGE becomes OSTEOBLASTS which becomes OSTEOCYTES. • When minerals are needed by the body, osteoclasts dissolve bone tissue to release the minerals. This process is called mineral resorption.

Types of Joints • There are three basic types of joints: 1. Fibrous joints (not movable) Ex: Sutures of the Skull 2. Cartilaginous joints (slightly movable) Ex: Pubic synthesis, Intervertebral joints 3. Synovial joints (freely movable) Contain synovial fluid to lubricate the joint Ex: Plane joints, hinge joint, pivot joint, condyloid joint, saddle joint, ball-and-socket joint

Fractures 1. Complete fracture: the bone snaps into two or more parts 2. Greenstick: one side of the bone is broken and the other only bent. 3. Single: bone is broken in one place into two pieces 4. Comminuted: bone is broken or crushed into three or more pieces 5. Bowing: incomplete fractures of tubular long bones usually in pediatric patients 6. Open: broken bone that penetrates the skin

Abnormal Bone Conditions 1. Bone spurs: bony projections that develop along the edges of bones 2. Osteoporosis: bone-thinning disease in which the bones become fragile & easy to fracture 3. Disorders of the spine a) Scoliosis: sideways curvature of the spine that occurs most often during the growth spurt just before puberty b) Kyphosis: exaggerated rounding of the back c) Lordosis: excessive curvature of the lower back inward d) Ankylosis: abnormal stiffening and immobility of a joint due to fusion of the bones

Bone Spur

Osteoporosis

Scoliosis

Kyphosis

Lordosis

Ankylosis