The SKIN, MUSCLE & BONES OBJECTIVES SKIN

1. The SKIN, MUSCLE & BONES OBJECTIVES SKIN 1. Explain the functions of the integumentary system. Describe the composition of the two layers of skin MUSCLE 1. Describe the three types of muscle tissue Show the molecular mechanisms for contraction BONES Summarize the functions of the skeletal system. 2. List and point to different types of joints.

2. Integumentary system

3. - The epidermis is the outermost layer of the skin, composed of terminally differentiated stratified squamous epithelium, acting as the body's major barrier against an inhospitable environment At the bottom of the epidermis is a very thin membrane, called the basement membrane, which attaches the epidermis firmly, though not rigidly, to the layer below.    The second layer lies deeper and is called the dermis. It contains blood vessels, nerves, hair roots and sweat glands.    Below the dermis lies a layer of fat, the subcutaneous fat. The depth of this layer differs from one person to another. It contains larger blood vessels and nerves, and is made up of clumps of fat-filled cells called adipose cells.

4. - Keratinis an extremely strong protein which is a major component in skin, hair, nails, hooves, horns, and teeth. The amino acids which combine to form keratin have several unique properties, and depending on the levels of the various amino acids, keratin can be inflexible and hard, like hooves, or soft, as is the case with skin - Human skin color can range from almost black (due to very high concentrations of the dark brown pigment melanin) to nearly colorless (appearing reddish white due to the blood vessels under the skin) in different people. Skin color is determined by the amount and type of melanin, the pigment in the skin - A hair follicle is part of the skin that grows hair by packing old cells together. Attached to the follicle is a sebaceous gland, a tiny sebum-producing gland found everywhere except on the palms, lips and soles of the feet. The thicker density of hair, the more sebaceous glands are found.

5. When skin or organs are damaged, the body naturally wants to heal itself. Since the body cannot re-create healthy skin or tissue, it puts together new fibers that are not as functional as the original tissue, but that serve as a protective, useful barrier. When this barrier is completely healed, it is known as a scar. Scar tissue in the skin is inferior to healthy, normal skin for several reasons: sweat glands are damaged or destroyed, hair does not grow back, and there is less resistance to ultraviolet radiation. Skin scars are normally flat and pale, illustrating the history of the injury which caused them, yet often a body will produce too much fibrous tissue, resulting in an extra thick or raised scar A sunburn is a burn to living tissue such as skin produced by overexposure to ultraviolet (UV) radiation, commonly from the sun's rays. Usual mild symptoms in humans and animals are red or reddish skin that is hot to the touch, general fatigue, and mild dizziness. An excess of UV-radiation can be life-threatening in extreme cases. Exposure of the skin to lesser amounts of UV radiation will often produce a suntan

6. Muscular system Skeletal muscle contraction

7. Animals use muscles to convert the chemical energy of ATP into mechanical work. Three different kinds of muscles are found in vertebrate animals • Heart muscle(cardiac muscle)— makes up the wall of the heart. Throughout life, it contracts some 70 times per minute pumping about 5 liters of blood each minute.

8. - Smooth muscle is found in the walls of all the hollow organs of the body (except the heart). Its contraction reduces the size of these structures. Thus it • - regulates the flow of blood in the arteries • - moves your breakfast along through your gastrointestinal tract • - expels urine from your urinary bladder • - sends babies out into the world from the uterus • - regulates the flow of air through the lungs • The contraction of smooth muscle is generally not under voluntary control.

9. - Skeletal muscle, as its name implies, is the muscle attached to the skeleton. It is also called striated muscle. The contraction of skeletal muscle is under voluntary control.

10. Skeletal system

11. Bone marrow is the flexible tissue found in the hollow interior of bones. In adults, marrow in large bones produces new blood cells. It constitutes 4% of total body weight, i.e. approximately 2.6 kg (5.7 lbs.) in adults. There are two types of bone marrow: red marrow (consisting mainly of myeloid tissue) and yellow marrow (consisting mainly of fat cells). Red blood cells, platelets and most white blood cells arise in red marrow. Both types of bone marrow contain numerous blood vessels and capillaries A tendon (or sinew) is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments as they are both made of collagen. Tendons and muscles work together and can only exert a pulling force. Ligamentsare fibrous bands or sheets of connective tissue linking two or more bonesor cartilages, together. One or more ligaments provide stability to a joint during rest and movement.