Protection, Support, and Locomotion Chapter 37

37.1 Skin: The Body’s Protection Your skin is your largest organ Derived from the ectoderm layer of an embryo

37.1 Skin: The Body’s Protection Two overall layers (p. 936): Epidermis- Outer most layer is dead cells, but includes a layer of live cells below that Dead skin cells contain keratin. This makes your skin waterproof, and provides your live cells with some protection. The live cells of the epidermis have melanin, or pigment. This pigment protects the cells from some solar damage. Dermis- Inner portion of the skin. Thickness of this layer varies based on what that part of the body does. Feet- 3-4 mm, Eye- 0.5 mm. Blood vessels, nerves, nerve endings, hair follicles, sweat glands and oil glands are found in the dermis.

Skin’s Vital Functions Regulate Temperature When you get hot: capillaries dilate to release heat and you secrete water (sweat) When you get cold: hair stands up and small muscles flex to generate heat (shivering) Protection Prevents physical and chemical damage as well as preventing the invasion of microbes Sense Organ Nerve cells detect pressure, pain, and temperature Chemical Regulation Sunlight causes the production of vitamin D, which out body needs in order to absorb calcium

Skin Injury When small injuries damage the epidermis, the remaining cells undergo mitosis in order to repair the injury Injuries that go down to the dermis often cause bleeding First, a blood clot forms to restore the continuity of the skin Next, a scab forms. This prevents bacteria from getting into the wound Finally, skin cells beneath the scab divide to fill the gap until the scab falls off.

Skin Injury Burns- are categorized by their severity. First-degree- redness and mild pain in epidermal cells. Second-degree- damage to the dermis with blistering and scarring. Third-degree- destroys the epidermis and the dermis. Skin function is lost. Scarring is severe. Skin grafts are often required.

Skin Injury Aging- as we age, our skin loses elasticity (gets wrinkly) This is related to a lower production of oils in the skin Can be made worse by ultraviolet rays

37.2 Bones: The Body’s Support 206 bones broken down into two categories Axial Skeleton- Skull, Vertebral Column, Ribs, Sternum, Inner Ear Bones Appendicular Skeleton- Bones of the limbs and associated bones Bones are connected to each other at joints Joints are supported by ligaments Some joints need a cushion to absorb shock. This cushion is called a bursa. Tendons are connective tissue that hold muscles to bones

37.2 Bones Types of Joints Fixed Joints- places where two bones meet but there is no movement Ex: Skull Gliding- Allow bones to slide past each other Ex: Wrist and ankle Hinge- Allow back and forth movements Ex: Elbow, knees, fingers, toes Pivot- Allow bones to twist against each other First two vertebrae form a pivot joint Ball and Socket- Allow rotational movements Ex: Hips and shoulders

37.2 Bones How do bones form? Types of Bone Tissue Our skeleton starts out as cartilage. Cells called osteoblasts create the collagen cells that can eventually develop into bones when minerals, like calcium, are deposited Bones only get longer at the ends Types of Bone Tissue Compact Bone- Outer layer of bone. Covered by nerves and blood vessels. Spongy Bone- Less dense than compact bone. Found between compact bone and marrow. Marrow- Center cavity of certain bones. Makes blood.

37.2 Bones Functions on the Skeleton Framework- gives our body its overall shape Protection- Ribcage, hips, skull, vertebrae protect internal organs Movement- Muscles must be able to pull on a bone in order to cause movement Make Blood Cells- Red Marrow makes red blood cells, white blood cells, and platelets. Yellow Marrow produces red blood cells and kicks into high gear to help replenish blood in the event of major blood loss. Store Minerals- Calcium and phosphorus are stored in our bones.

37.3 Muscles for Locomotion Types of Muscles Involuntary- muscles that are not under conscious control Smooth- Line organs and Blood vessels Cardiac- The muscle tissue that makes up the heart Voluntary- Under conscious control Skeletal- attached to bone and moves the skeleton

37.3 Muscles Skeletal Muscles Contraction- Sliding Filament Theory Myofibrils- Small fibers that make up muscle fibers Myosin- Thick filaments that make up myofibrils Actin- Thin filaments that make up myofibrils Sarcomere- Each section of myofibril is called a sarcomere.

37.3 Muscles Strength varies by thickness of muscle fibers, not number of muscle fibers Muscle cells use a lot of ATP when you are being active When oxygen supply is high enough, the cells undergo aerobic respiration If oxygen supply becomes inadequate, then the muscle cells will begin undergoing anaerobic respiration in the form of lactic acid fermentation Lactic acid builds up in the muscles