The SkeletalSystem

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.

Male Female

Skull is heavy and rough Lighter and smoother

Forehead is usually sloping More vertical

Sinuses are large Smaller

Cranium is large Smaller (by about 10%)

Mandible is large and robust Lighter and smaller

Teeth are large Smaller

PELVIS

Narrow, robust, heavy, rough Broad, light, smooth

Pelvic inlet is heart shaped Oval to round shape

Iliac fossa is deep Relatively 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 anteriorly Points inferiorly

Bone weight is heavy Lighter

Bone markings are prominent Less 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.

The skeletal system accounts for about 14% of our body weight. In the adult skeleton the 206206 distinct bones, are allocated as follows:

Axial Skeleton

Vertebral column

Skull

Hyoid Bone

Ribs & Sternum

Appendicular Skeleton Upper Extremities

Lower Extremities

Auditory OssiclesTOTAL

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 (H2O 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