Skeletal System Functions Supports the body protects organs

Skeletal System Functions: Supports the body, protects organs, site of blood cell formation Components: Bones, joints, ligaments

Skeletal System: Bone Structure Bones are a solid network of living cells and protein fibers that are surrounded by deposits of calcium salts.

Skeletal System: Bone Structure Periosteum: tough outer layer Haversian canals: where nerves and blood vessels run Spongy bone: less dense tissue under the outer layer Bone marrow: soft tissue that stores fat and produces blood cells

Skeletal System: Bone Development - Cartilage is connective tissue without blood vessels. Human embryos have skeletons made of cartilage. - Cartilage is replaced by bone during ossification (bone formation). This begins 7 months before birth as cells secrete minerals that replace cartilage.

Skeletal System: Bone Repair Osteoblasts: cells that build bone tissue. Osteoclasts: cells that break down bone minerals. Osteoporosis: disorder in which osteoclasts break down bone faster than osteoblasts build it.

Skeletal System: Joints - location where two bones “connect”

Skeletal System: Ligaments - tissue that holds bones together in a joint

Skeletal System: Injury Torn ACL (Anterior Cruciate Ligament) - in center of knee - prevents tibia (shin) from moving too far forward - if torn, knee is unstable and easily injured

Muscular System Function: Movement (voluntary and involuntary) Components: skeletal muscle, smooth muscle, cardiac muscle

Muscular System: Skeletal Muscle: - Attached to bones - Allow for voluntary movements - Controlled by nervous system (motor neurons)

Muscular System: Smooth Muscle - Involuntary movements - Controls: pupil size, food movement, blood flow - Functions without stimulus from nervous system (electrical impulses travel between cells)

Muscular System: Cardiac Muscle - Found in the heart - Functions without stimulus from the nervous system (electrical impulses travel between the cells)

Muscular System: Muscle Contractions - Motor neuron releases neurotransmitter (acetylcholine, ACh) - ACh received by muscle cell - Muscle cell contracts (see picture) until ACh is no longer received.

Bone and Muscle Interactions Tendons - Skeletal muscles are joined to bones by tendons. - Tendons pull on the bones to make them move.

Flexibility: range of movement in a joint or joints, and length in muscles that cross the joints.