Chapter 2, Human biology.  8-E

Skeletal System.  Has five major functions: provides shape and support, enables you to move, protects your internal organs, produces blood cells, and stores certain materials until your body needs them.  Vertebrae- 26 small bones that make up your backbone.

Bones  Bone strength- strong and lightweight, can absorb more force without breaking then concert or granite.  Bone growth- start out as cartilage when you are a infant and by age 5 most cartilage is turned to bone. You continue to grow new bone tissue until adult hood.  For structure of bones see figure 3, and slide 2.

The structure of bones.  Bones include-  Marrow: soft tissue where red and white blood cells are made.  Cartilage: connective tissue that is more flexible than bone. Acts as a cushion.  Outer membrane: allows nerve and blood cells to pass through the bone.  Compact bone: hard and dense but not solid. Contains canals that hold blood vessels.  Spongy bone: found at the end of the bone, helps cushion the joints.

Joints of a skeleton.  Immovable joints: connect joints in the body that allows little or no movement.  Movable joints: allow the body to make a wide range of movements. The tissue in movable joints are called ligaments.  Ligament: cartilage that covers the ends of the bones and keeps them from rubbing against each other.

Movable joints.  Ball and socket joint: allow the greatest range of motion. Example: shoulder.  Hinge joint: allows extensive forward backwards motion. Example: knee.  Pivot joint: allows one bone to rotate around another. Example: neck.  Gliding joint: allows one bone to slide over another. Example: wrist.

Bone care.  A combination of a balanced diet and regular exercise can start you on the way to a lifetime of healthy bones.  Osteoporosis: a condition in which the body’s bones become weak and break easily.

Diagnosing bone and joint injuries.  Fracture: a break in the bone.  Sprain: when ligaments are stretched too far and tear in places.  Dislocation: occurs when a bone becomes out of it’s joint.  X-ray: a form of energy that travels in waves passes through soft tissue but not through bone.  MRI: uses short burst of magnetic energy causing the atoms inside the body to vibrate allowing them to create images.

The muscular system. Two types of muscle actions: o Involuntary: muscles that are not under your control. Responsible for activities such as breathing and digesting food. o Voluntary: muscles that are under your control.

Types of muscles  Skeletal muscles: voluntary muscle that attach to the bones of your skeleton. Attached by tendons, and provide the force that moves your bones, is striated.  Tendon: strong connective tissue that attaches muscle to the bone.  Smooth Muscle: involuntary muscle that works automatically to control many types of movements inside your body.  Cardiac Muscle: has characteristics of both smooth and skeletal muscles, and is involuntary. Cardiac muscle, or the heart, is striated.

Muscles at work  Muscle cells can only contract, not extend. While one muscle contracts the other muscle in the pair returns to its original length. Muscles must work in pairs.

The skin  Skin functions include:  Covers the body.  Prevents loss of water.  Protects the body from injury and infections.  Regulates body temp.  Eliminates waste.  Gathers info. About the environment.  Produces vitamin D.

Epidermis  Epidermis: is the outer most layer of skin.  No nerves or blood vessels.  Made of dead skin cells.  Protects the body, sheds bacteria.  Contains melanin- a pigment or colored substance that gives skin its color.

Dermis  Dermis- lower layer of skin, which contains blood vessels, nerves, sweat glands, hair follicle, & oil glands.  Pores- openings of skin for sweat.  Acne: bacterial infection of the skin.  Cancer- disease in which cells divide uncontrollably.