1. Protection, Support, and Locomotion
Chapter 37

2. 37.1 Skin: The Body’s Protection
Your skin is your largest organ
Derived from the ectoderm layer of an embryo

3. 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.

4. 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

5. 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.

6. 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.

7. 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

8. 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

9. 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

10. 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.

11. 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.

12. 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

13. 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.

14. 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