● Average adult has 206 bones.● Baby has over 300.● Longest bone: “Femur” (thighbone).● Smallest bone: 3 bones in middle ear.● Skeletal System: Bones and tissues.

Supports, protects, and moves body.● Parts of skeletal system: Bones,

cartilage, joints, ligaments, and tendons.● Appendicular skeleton: Legs, arms, feet,

and hands.● Axial skeleton: Skull, rib cage, spinal

column.● Bones are living tissue.● Bones are made of cells called osteoblasts.● Osteoblasts work in groups o form the living part of

the bone.● These groups of cells deposit minerals, such as

calcium, into the mineralized portion of the bone.● Compact bone is hard and dense.

o Rigid with no open spaces.o Contains tiny canals where blood vessels are

located.● Spongy bone protects red and yellow bone marrow.

o Has many open spaces.● Marrow is the soft tissue inside of bone.● There are two kinds of marrow:

o Red marrow: Makes red and white blood cells.

o Yellow marrow: Stores fat.

● Cartilage is the soft tissue of the skeletal system.

● When you are born, you don’t have much true bone, it’s mostly cartilage.

● Some cartilage covers the ends of bones for cushioning.

● Some cartilage is never replaced by bone end of your nose, top of your ear).● The place where two or more joints meet are joints● Gliding Joints:

o Bones glide over each other for some flexibility (wrist and hand)● Ball and Socket joints:

o Allows movement in all directions (Shoulder and hip).

● Hinge Joints:o Allows backward and

forward motion or flexion and extension (Knee and elbow).

● Joints are held together by ligaments.

● Ligaments are strong bands of connective tissue.

● Ligaments connect bone to bone.● Dislocated Joint:

o One or more bones move out of place.● Sprain:

o A ligament is stretched too far or torn.● Fracture: Cracked but not fully broken.● Osteoporosis:

o Bones become less dense, weak, and break easy (disease).

● Muscles are tissue that contract, which enables movement.● Muscles make up bulk of body.● 1/3 of weight● 3 types: Skeletal, smooth, cardiac● Muscles are made of thousands of small fibers.● Move substances throughout the body.

o Food through digestiveo Blood through circulatoryo Fluids through excretory

● Smooth muscle lines organs and is involuntary.● Cardiac muscle found only in the heart.● Smooth muscle:

o In the digestive tract and walls of blood vessels.

● Skeletal muscles:o Attach to your bones for movement

and helps to protect inner organs.● Voluntary muscle action is under your

control.● Involuntary muscle action is not under

your control.● Some actions could be both.

o You can blink your eyes, but they’ll also blink automatically.

● When you want to move, a chain of events happens:o A nerve impulse travels from your brain to the skeletal muscle.o The muscle cells contract.o The muscle contraction pulls the bones in the direction they need to move.