The Skeletal System THE GENERAL framework of the body is built up mainly of a series of bones, supplemented, however, in certain regions by pieces of cartilage; the bony part of the framework constitutes the skeleton. The skeleton supports the body, protects vital organs, and works in conjunction with the muscles to cause movement.

Functions of the Skeletal System ________________ strong structural frame; every other part of the body is “hung” on bones like a hanger _ _______________ internal organs (brain by cranium, heart & lungs by ribs & sternum, spinal cord by spinal column) ________________ attachment for muscles that move us; lever systems; bones are hinged with muscles crossing the joints

Functions of the Skeletal System ________________ red marrow produces blood cells within internal structures of long bones________________ calcium & phosphate storage; needed for muscle contraction, nerve cell function, & movement of materials across cell membranes________________ relatively unique shape to organisms; height/weight/width; structure sub-serves function

The Sexes A baby's skeleton has 350 bones, but many of these fuse to give an adult a total of 206 bones. ________________ ________________has broader shoulders than a woman's, a longer ribcage, and a narrow pelvic girdle optimized for walking/running/jumping. ________________ ________________has the same bone complement as a man's but is slightly smaller (lighter) and less robust, with a wider pelvic opening to assist childbirth. There is a list of the major criteria shown in the chart on the following page to further distinguish between the sexes.

MaleFemale Skull is heavy and roughLighter and smoother Forehead is usually slopingMore vertical Sinuses are largeSmaller Cranium is largeSmaller (by about 10%) Mandible is large and robustLighter and smaller Teeth are largeSmaller PELVIS Narrow, robust, heavy, roughBroad, light, smooth Pelvic inlet is heart shapedOval to round shape Iliac fossa is deepRelatively shallow Ilium extends further above the sacrum More vertical, less above the sacroiliac Angle under the symphysis is usually much less than 90 degrees Angle is often greater than 100 degrees Sacrum is long, with a pronounced sacral curvature Broad, short less curvature Coccyx points anteriorlyPoints inferiorly Bone weight is heavyLighter Bone markings are prominentLess prominent

Axial & Appendicular Skeleton ________________ the joints make it possible for a considerable degree of freedom for the upper and lower limbs. includes the pectoral and pelvic girdles and the bones of the arms, forearms, wrists, hands, thighs, legs, and feet. Fractures and dislocations are more common in this part of the skeleton. _________ principle supportive structure of the body and is oriented along its medial longitudinal axis. includes the skull, vertebrae, sternum, ribs, and hyoid bone.

206 The skeletal system accounts for about 14% of our body weight. In the adult skeleton the 206 distinct bones, are allocated as follows: Axial Skeleton Vertebral column Skull Hyoid Bone Ribs & Sternum Appendicular Skeleton Upper Extremities Lower Extremities Auditory Ossicles TOTAL

BONES ____________ Skeletal actually means “ ____________ ”, bones appear lifeless but are living systems that grow, mature, repair & recycle (remodel) Bones are composed of living tissue (bone cells, fat cells, blood vessels) and non-living tissue (H 2 O and minerals) Bones are classified into 5 main types based on shape Long bones Short bones Flat bones Irregular bones Sesamoid bones

________________ Greater in length than width Designed to absorb stress from body & leverage (used in locomotion & weight bearing) – STRUCTURE SUBSERVES FUNCTION! Diaphysis (shaft) and epiphyses (ends of bone) Bone marrow activity (production of blood cells)

________________ Equal in length & width Form a shape roughly equal to a cube No bone marrow activity Examples –

________________ Thin & flat Offer protection & considerable surface area for muscle attachment No bone marrow activity Examples –

________________ Complex shapes Not easily grouped into other 3 categories No bone marrow activity Examples –

________________ Unusual bones Small, flat bones wrapped within tendons Move over bony surfaces