The Skeletal System Bones and Joints Functions Supports

The Skeletal System Bones and Joints

Functions • Supports and give shape to the body • Protects internal organs • Helps make movements possible when bones at moveable joints are pulled by muscles • Stores calcium – hormones regulate calcium storage: – calcitonin (CT) increases storage – parathyroid hormone (PTH) reduces store of calcium • Hematopoiesis – blood cell formation in red bone marrow

Types of Bones Classified according to overall shape Long Short humerus carpals Flat frontal Irregular Sesamoid (round) bone patella vertebrae

Structure of Long Bones Diaphysis – shaft – hollow tube of hard compact bone Medullary cavity – hollow area inside diaphysis, contains yellow bone marrow Epiphyses – ends – spongy bone that contains red bone marrow Articular cartilage – covers epiphyses and functions as cushion Periosteum – strong membrane covering bone everywhere except joint surfaces Endosteum – thin membrane lining medullary cavity

Structure of Flat Bones • Spongy bone layer sandwiched between two compact bone layers • Diploe – spongy bone layer of a flat bone

Quick Check 1. Name some of the organs of the skeletal system. 2. What are the five major functions of the skeletal system? 3. What are the four categories of bone in the skeletal system? 4. Describe the major features of a long bone. 5. How does the typical flat bone differ?

Cancellous Bone Spongy (cancellous) bone • Texture results from needlelike threads of bone called trabeculae surrounded by open spaces • Found in epiphyses of bones • Spaces contain red bone marrow

Compact Bone • Hard, dense and appears solid to the naked eye • Structural unit is an osteon – calcified matrix arranges in layers of rings called concentric lamella • Bone cells are called osteocytes – Found between hard layers of the lamellae in little spaces called lacuanae • Are connected by tiny tubes called canaliculi

Cartilage • • Cell is called a chrondocyte Has the flexibility of plastic Matrix is gel-like Lacks blood vessels so healing is slow after an injury

Bone Formation and Growth • Long bone grows from small centers located in both ends (epiphyses) and from the large center (diaphysis) • Epiphyseal plate – cartilage that indicates a bone is still growing in size • Epiphyseal line – remains to mark the location where the two centers of ossification have fused together

Quick Check 1. What is the basic structural unit of compact bone tissue called? 2. What are osteocytes? 3. Where would you find them in bone tissue? 4. What is ossification? 5. What is the role of the osteoblast?

Divisions of the Skeleton Axial • • Skull Spine (vertebral column) Thorax Hyoid bone Appendicular • Upper extremities, including shoulder (pectoral) girdle • Lower extremities, including hip (pelvic) girdle

Skeletal Differences Male • Generally larger • Pelvis -deep and narrow Female • Pelvis – shallow and broad • Wider pelvic inlet to allow for childbirth • Wider pubic angle

Types of Joints Synarthroses • No movement – fibrous connective tissue grows between bones Amphiarthroses • Slight movement – cartilage connects articulation bones

Types of Joints Diarthroses – permit free movement • Joint capsule and ligaments hold adjoining bones together but permit movement • Articular cartilage cover joint ends of bones where they form joints with other bones • Synovial membrane – lines joint capsule and secretes lubricating fluid • Joint cavity – space between joint ends of bones • Bursa – fluid-filled pouch that absorbs shock

Types of Diarthrotic Joints Ball and Socket • A ball shaped head of one bone fits into a concave socket of another • Widest range of movement Hinge • • • Movement in 2 directions Flexion and extension Elbow Knee Fingers

Types of Diarthrotic Joints Pivot • A small projection from one bone pivots in an arch of another • Rotation • Atlas and axis (1 st and 2 nd vertebrae) Saddle • Permit great mobility • Flexion, extension, abduction, adduction, circumduction • Only between metacarpal of thumb and carpal bone of wrist

Types of Diarthrotic Joints Gliding • Least movable diarthrotic joint • Flat, articulating surfaces permit limited gliding movement Condyloid • A condyle, or oval projection fits into an elliptical socket

Types of Movement Flexion • Reduces the angle of the joint • Ex. Bending the elbow Extension • Increases the angle of a joint • Ex. Straightening a bent elbow

Types of Movement Rotation • Spins one bone relative to another • Ex. Rotating the head at the neck joint Circumduction • Moves the distal end of a bone in a circle while keeping the proximal end relatively stable • Ex. Circumducting the shoulder joint

Types of Movement Abduction • Moving away from the midline • Ex. Moving the arm to the side away from the body Adduction • Moving toward the midline • Ex. Moving the arm towards the body

Quick Check 1. What are the 3 major types of joints in the skeleton? Give an example of each. 2. What membrane in a diarthrotic joint provides lubrication for movement? 3. What is a ligament? 4. List and describe the 6 types of movement and give an example of each.