Chapter 24

Support and Movement of the Body

Human Skin

• Your skin is one of your body’s major defenses.• Few disease causing organisms can penetrate

your skin unless it is somehow broken.

Structure of the Skin

• Skin is made of two layers.• The outer layer is the epidermis.• It has dead cells at the surface.• It has living cells underneath with nerve

endings such as pain receptors.• The dead cells come off on a regular basis and

are replaced by new cells from underneath.

Structure of the Skin

• The inner, thicker layer of the skin is the dermis.

• It contains blood vessels, nerve receptors, and hair follicles.

• Sweat glands, oil glands, and wax glands are also found in the dermis.

Structure of the Skin

• Hair develops from the cells of hair follicles.

• As these cells divide, the hair grows!

• New growth deep in the skin is alive, but as hair grows out of follicle, it is dead.

• The subcutaneuous layer below the dermis is not really a part of the skin.

• It is really a layer of fat cells and tissue.

Skin Color

• A pigment called Melanin cause the color of human skin.

• Special cells produce melanin.• Skin that produces little melanin is more pink.• Some people groups also produce a pigment

called carotene, which is more yellowish.

Protection of the Skin

• Skin can burn when exposed to too much radiation from the sun.

Protection of the Skin

• The ultraviolet light from the sun can also cause mutations to occur in your skin cells and this causes cancers.

Protection of the Skin

• Find out your risk of skin cancer!

http://coolshade.tamu.edu/stNA.htm

How Your Skin Protects You!!

• You skin is a barrier to harmful chemicals and disease causing organisms.

• Nerve receptors warn you to move away from hazards.

• Calluses from to create a barrier from friction.• Blisters can also form from water building up

under the epidermis due to friction.

Regulating Body Temperature

• Your skin regulates your body temperature.

Bones

• Few bones are solid!• Most have a hard

coverings with spongelike spaces inside.

• This is called spongybone.

• Inside are cavities filled with bone marrow which produces blood cells.

The Skeletal System

• Functions:1. Framework for support and movement2. Protection3. Storage of minerals4. Production of blood cells

Bones

• The bone is covered with a tissue called perisoteum.

• The periosteum forms new bone as you grow!

• Joined to the periosteum are ligaments and tendons.

• Ligaments connect bones to other bones.

• Tendons connect muscle to bones.

The Structure of Bone

• Bones contain living bone cells, blood vessels, and nerves.

• There are two main types of tissue for the skeleton: Bone and Cartilage

• Bone is hard!• Cartilage is softer and more flexible!

The Muscular System

• Types of Muscle:1. Voluntary Muscles – Muscles you can

control!2. Involuntary Muscles – Muscles that you can’t

control!

Voluntary Muscles

• Skeletal Muscle• Skeletal muscle is

muscle that is attached to and moves your skeleton!

• It is said to be “striated muscle” because it has a bands known as “striations”.