The Skeleton & Muscles Chapter 37

The human skeleton Divided in to 2 regions 1.AXIAL SKELETON---skull, spine, ribs & sternum 2.APPENDEDICULAR SKELETON---- limbs, pectoral girdle & pelvic girdle

Main Bones of our Skeleton

The Skull Protects the brain The Spine Made up of 33 bones( vertebrae) which are arranged in to 5 regions Vertebrae protect & enclose the spinal cord

Disc of cartilage are located between the vertebrae and act as shock absorbers and distribute the load within the vertebral column

Section of the spine 1.Cervical ( 7 vertebrate) 2.Thoracic ( 12 vertebrae) 3.Lumber ( 5 vertebrae) 4.Sacrum ( 4 vertebrae) 5.Coccyx ( 4 vertebrae)

OUR SPINE -- VERTEBRAE

Rib cage Protects the heart & lungs Consists of the sternum & 12 pairs of ribs 7 true ribs– attach to the breastbone & spine 3 false ribs – attach to the spine and each other at the front of the chest 2 floating ribs– attached to the spine

Appendicular skeleton Pectoral girdle, pelvic girdle & limbs The Pectoral Girdle( shoulder) Consists of collar bone (clavicle) & shoulder blades (scapulas) Attaches the arms to the rib cage and allows movement Attached to the pectoral girdle are the humerus, radius, ulna, carpals (wrist bone) & metacarpals( containing phalanges)

The Pelvic Girdle Consists of the hip bones attached to the sacrum Attaches the trunk to the legs Attached to the pelvic girdle are the femur, patella ( knee cap) tibia, fibula, tarsals (ankle bones) & metatarsals ( containing phalanges)

Functions of the skeleton Maintains body shape Gives support Protects organs Allows movement Makes blood cells

Bone EXTERNAL STRUCTURE The periosteum is a membrane that encloses long bones The diaphysis is the long shaft of a bone The epiphysis is at either end of the bone

Internal structure Compact bone Gives strength & stiffness to the bone, contains living cells which are supplied by blood vessels & nerve fibres Spongy bone Gives strength & stiffness, consists of bony bars & plates that are separated by red and yellow marrow

Bone marrow Found within bone ends, it produces blood cells Yellow marrow Found within shaft, contains fat storage tissue Medullary cavity Hollow area through centre of bone, surrounded by layer of compact bone, then spongy bone, then more compact and finally cartilage

Cartilage Is found in movable joints, in rings around the trachea & in the discs between vertebrae It is made up of protein fibres It acts as a shock absorber

Bone Growth Higher Level Only Before wk8 of embryonic development there is no bone, only cartilage From Wk8 onwards bone forming cell ( osteoblasts) make bone cells to replace the cartilage As growth continues until the end of puberty, cartilage keeps multiplying on the side of the growth plate near the epiphysis When the cartilage cells in the growth plate are all replaced by bone, growth stops

Bone renewal HIGHER LEVEL ONLY Bone is constantly being broken down inside the medullary cavity by osteoclasts & built up by osteoblasts, in order to stop the bone from becoming too heavy Osteoclasts absorb broken down bone, remove worn cells & deposit calcium into the blood

Bone renewal depends on Physical activity Hormone levels Diet

Ligaments/ tendons/joints LIGAMENTS: Connect bone to bone TENDONS: Connect muscle to bone JOINTS: Where two or more bones meet

Types of joints IMMOVABLE Fused or fixed joints such as in the skull SLIGHTLY MOVABLE Between vertebrae FREELY MOVABLE (synovial joints) Ball & socket joints --- shoulder and hip Hinge joint--- elbow and knee

Antagonistic muscles Are pairs of muscles that work opposite each other eg biceps & triceps The BICEPS contracts and pulls on the radius causing the lower arm to bend upwards. It is a flexor The TRICEPS contract and pulls on the ulna causing the lower arm to straighten out. It is an extensor

Arthritis Is a disorder of the musculosketal system Is result from the inflammation of joints Prevention: by reducing damage to joints in sports Treatment: rest, exercise, drugs & surgery

Osteoporosis Cause: inadequate intake of calcium and vitamin D Prevention: weight bearing exercise Treatment: surgery to fix/replace broken bones