Introduction to the Skeletal System

Objectives Be able to list the general functions of the skeletal system Identify the parts of the skeletal system Discuss the active tissues found in bone Classify bones according to shape

Human Skeleton Facts Makes up 1/5 of a healthy body’s weight Adults have 206 bones on average We are born with 270 bones, but many of fuse together as we grow Longest bone in the body is the femur Smallest bone in the body is the stapes bone in the middle ear

Divisions of the Human Skeleton Axial Skeleton: includes the bones of the skull, ribs, spine, and sternum Appendicular Skeleton: includes the bones of the arms, legs, scapula, clavicle, and pelvis

Axial vs. Appendicular

Functions of the skeletal System Support: gives shape & structure to the body Movement: provides a rigid framework against which muscles can pull Protection: protects delicate internal organs such as the rib cage protecting the heart & lungs

Functions of the skeletal System Blood Cell Production: site of hematopoiesis, which is the process that produces red blood cells, platelets and some white blood cells from the bone marrow Storage: stores minerals such as calcium & phosphorus Endocrine Regulation: bone cells release the hormone osteocalcin which controls the regulation of blood sugar and fat deposition

Tissues of the Skeletal System Bone Cartilage Dense connective tissue Blood nervous

4 Classifications of Bones Long bones: have long longitudinal axes and expanded ends Examples: radius, ulna, femur Short bones: are cube-like, with roughly equal lengths and widths Examples: carpals and tarsals Sesamoid (round) bone: is a special type of short bone that is small and nodular and embedded in a tendon adjacent to a joint Example: patella (knee cap)

4 Classifications of Bones Flat bones: are plate-like structures with broad surfaces Examples: ribs, scapula, and parts of the skull Irregular bones: have a variety of shapes and most are connected to several other bones Examples: vertebrae and many facial bones

Parts of the Skull

Parts of the Skull

Differences b/w Males & Females Males have slightly thicker and longer legs and arms Males have longer and thicker phalanges Females have a wider pelvis and a larger space within the pelvis Females have narrower rib cages, smaller teeth, less angular mandibles, less pronounced cranial features, and carrying angle of the forearm is more pronounced