SKELETAL SYSTEM

Functions of the Skeletal System Bones are made of OSSEOUS TISSUE Support and Protection Body Movement Blood Cell Formation Storage of Inorganics (salt, calcium, potassium….)

ORGANIZATION About 206 bones 2 Main Divisions – Axial & Appendicular

Axial Skeleton Head, neck, trunk Skull Hyoid Bone Vertebral Column Thoracic Cage (ribs, 12 pairs) Sternum

Appendicular Skeleton Limbs & Bones that connect to the o Pectoral Girdle (shoulders) o Pelvic Girdle (hips)

BONE STRUCTURE - Long Bone 1.Epiphysis 2.Diaphysis 3.Articular Cartilage 4.Periosteum

Inside the Long Bone Medullary Cavity – hollow chamber filled with bone marrow Red Marrow (blood) Yellow Marrow (fat) Endosteum – lining of the medullary

Types of Bone Tissue Compact (wall of the diaphysis) Spongy (cancellous, epiphysis)

Microscopic Structure MATRIX - where the bone cells live OSTEOCYTES - mature bone cells, enclosed in tiny chambers called LACUNAE OSTEOCYTES form rings (LAMELLAE) around a HAVERSIAN CANAL which houses blood vessels Osteocytes are linked by CANALICULI Haversian Canals are linked by VOLKMAN's CANALS

BONE DEVELOPMENT & GROWTH 1.Intramembranous bones – flat, skull 2. Endochondral bones – all other ALL BONES START AS HYALINE CARTILAGE, areas gradually turn to bone PRIMARY OSSIFICATION CENTER (shaft) SECONDARY OSSIFICATION CENTER (ends)

Bone Development & Growth EPIPHYSEAL DISK (growth plate) is a band of cartilage between the epiphysis and diaphysis These areas increase bone length as the cells ossify Cartilage becomes OSTEOBLASTS become OSTEOCYTES

RESORPTION OSTEOCLASTS - dissolve bone tissue to release minerals, process is called RESORPTION

Types of Joints (articulations) 1.Synarthrotic (not moveable, aka sutures) 2.Amphiarthrotic (slightly moveable, vertebrae) 3.Diarthrotic (moveable joint, aka synovial joints)

BONES OF THE SKULL 1. Frontal - anterior portion above eyes 2. Parietal - one on each side of the skull, just behind frontal bone 3. Occipital - forms the back of the skull and base of the cranium 4. Temporal - forms parts of the sides and base of cranium 5. Sphenoid - wedged between several other bones in anterior portion of the cranium 6. Maxilla - forms upper jaws 7. Mandible - lower jaws, only moveable bone of the skull 8. Zygomatic Bone - cheekbone

TOPOGRAPHY OF THE SKULL Foramen - refers to any tiny opening, nerves and blood vessels leave this opening to supply the face Suture - refers to any connection between large bones (in fetal skulls, these are called fontanels) Fissure - any wide gap between bones

Sutures 1. Coronal - between frontal and parietal bones 2. Lambdoidal - between occipital and parietal bones 3. Squamosal - between temporal and parietal bones 4. Sagittal - between parietal bones

Abnormal Bone Conditions BONE SPURS: abnormal growth. Can occur on any bone (e.g. heel). OSTEOPOROSIS: Increased activity of osteoclasts cause a break down bone, and the subsequent fewer minerals in the extracellular matrix make it fragile. The spongy bone especially becomes more porous. Men get it as well as women. What’s the best way to prevent osteoporosis? Exercise! What does exercise do? Makes bones bigger. The most common bone used for a bone graft is the iliac bone of the hip.

ABNORMALITIES OF THE SPINE SCOLIOSIS is a lateral curve in the spine KYPHOSIS is a hunchback curve LORDOSIS is a swayback in the lower region. ANKYLOSIS is severe arthritis in the spine and the vertebrae fuse.

FACTS ABOUT BONES Bone is made of the same type of minerals as limestone. Babies are born with 300 bones, but by adulthood we have only 206 in our bodies. The giraffe has the same number of bones in its neck as a human: seven in total. The long horned ram can take a head butt at 25 mph. The human skull will fracture at 5mph.