The Skeletal System Anatomy and Physiology

Bone A connective tissue Contains bone tissue, cartilage, fibrous connective tissue, blood, and nervous tissue It is alive!

Functions Provides points of attachment for muscles Protection Support House blood producing cells Store inorganic salts and minerals

A typical bone Epiphysis: large knob on the ends Diaphysis: long shaft Periosteum: covering over all Compact bone: hard and rigid outside Spongy bone: spongy and contains marrow Articular cartilage: smooth surface on bone ends

Spongy bone and marrow Spongy bone is near the ends in the epiphyses Contains red marrow, which produces blood cells (fills an infant’s) Yellow marrow is in the medullary cavity, and stores fat, more in an older adult

Compact Bone Tightly packed Cells are called osteocytes Surrounded by fibers and cemented by hard background The structure forms around an osteonic canal, with blood vessels and nerves in the center osteocyte Osteonic canal

Osteonic Canals: bone grows in concentric circles Only in the compact bone!

Bone Cells Osteoblasts: are bone forming cells When they mature and become surrounded with the hard matrix, they are osteocytes Osteoclasts: break down bone

Osteoblasts and Osteoclasts When would osteoblasts be working? When forming new bone for growth, repair, replacement of aging or dying bone When would osteoclasts be working? When dissolving older bone containing dead cells, or to release calcium into the bloodstream if needed

Calcium Levels If too low, parathyroid gland senses this and secretes parathyroid hormone (PTH) PTH stimulates osteoclasts to break down bone and release calcium into blood Calcium levels in the blood return to normal Bone is sacrificed to keep blood calcium levels within normal

Calcium Levels If too high, thryoid gland senses this and secretes calcitonin Calcitonin stimulates osteoblasts to form new bone, depositing calcium in the new bone Calcium levels in blood return to normal

Why do we need calcium in the blood? For muscle contraction Nerve impulse conduction Blood clotting Other processes

Orange: is axial Yellow: is appendicular

Types of Skeletal Joints p.165 Fibrous: immovable, ex: sutures of skull Cartilaginous: bones connected by cartilage; limited movement; ex: vertebrae Synovial: bones surrounded by capsule and synovial membranes; ends of bones are covered in cartilage and surrounded by synovial fluid; lots of movement

Fibrous Connected by thin layer of fibrous connective tissue Sutures of skull, and distal ends of tibia and fibula

Cartilaginous Connected by cartilage Limited movement, as when back is twisted or bent

Synovial: 6 types

Synovial #1 Ball and Socket Hip and shoulder Ball shaped head joints with the cup of the other bone Circumduction

Synovial #2 Condyloid: oval shape of one bone joints with elliptical cavity of the other Between metacarpels and phalanges

Synovial #3 Gliding: surfaces are nearly flat Wrist, ankle Ribs 2-7 with the sternum

Synovial #4 Hinge: convex surface joins with a concave surface Flexion and extension Elbow, knee, and phalanges

Synovial #5 Pivot: can rotate around a central axis Proximal ends of radius and ulna Atlas and axis ( all other vertebrae are cartilaginous)

Synovial #6 Saddle: surface of bones are both convex and concave; fits in Only occurs in the joint between the carpal and the metacarpal of the thumb

Movement Flexion is forward movement of a body part Extension is backward movement of a body part

Movement Flexion also means bending a joint Extension also means straightening a joint Accomplished by a pair of muscles, working opposite to each other

Movement Abduction is lifting an a body part out away from the body to the side Adduction is bringing it back to your side