skin and the integumentary system chapter six. membranes 1.) serous membrane – line the body...
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Skin and the Integumentary System
Chapter Six
Membranes
1.) Serous Membrane – line the body cavities that lack openings to the outside.
Ex. Thorax and abdomen
2.) Mucous Membrane
• Line cavities and tubes that open to the outside of the body.
Ex. Oral and nasal cavity
3.) Synovial Membrane
• Forms the inner linings of the joint cavities between the ends of bones at freely movable joints.
Ex. Any movable joint
4.) Cutaneous membrane –
skin
Functions of Skin
• Helps Maintain Homeostasis• Provides Protective Covering• Regulates Body Temperature
• Houses Sensory Receptors
• Synthesizes Various Biochemicals
• Excretes Small Quantities of Waste
Two Tissue Layers
• 1.) Epidermis is the outer layer and is composed of stratified squamous epithelium.
• Four parts of the epidermis are distinguishable:– 1. Stratum basale– 2. Stratum spinosum– 3. Stratum granulosum– 4. Stratum coreum
Skin Growth
• The stratum basale is nourished by the dermis.
• New cells are formed in this area which pushes old cells to the surface.
• When these cells are closer to the surface they experience a large amount of keratin protein (Keratinization).
• This caused the old cells to die and eventually shed.
Melanin
• Melanocytes are specialized cells that absorb UV radiation. They are in the deepest portion of the epidermis.
Dermis
• Largely composed of dense connective tissue.
• It connects the epidermis to the underlying tissue it contains nerve cells, touch receptors, hair follicles, and glands.
Subcutaneous Layer
• Made of loose connective tissue and adipose tissue.
• Helps insulate the body and contains major blood vessels.
Accessory Organs
• Nails – protective coverings that cells divide in the white area then are keratinized.
Nails
• A nail bed lies over the area of the skin known as the nail bed.
• The white area of the nail (lunula) is the area of most rapid division. These moved upward, keratinize and die.
Hair Follicles
• Hair is formed by a group of epidermal cells at the base of a tubelike depression known as a hair follicle.
• Color is determined by the amount of melanin.
Sebaceous Glands
• These glands contain specialized epithelium and secrete an oily mixture (sebum) that helps keep the hair soft and water proof.
Sweat Glands
• Exocrine glands that are widespread through the skin.
• Sweat is made of mostly water, but contains small amounts of salt and waste.
Body Temperature Regulation
• When warm blood enters the brain it responds in two ways.– It stimulates dermal blood vessels to dilate so
more blood is near the surface releasing some heat.
– It also stimulates sweat glands. When the sweat reaches the surface and evaporates it also releases heat.
Cold Weather
• Dermal blood vessels can be contracted which keeps blood from flowing through the skin.
• Muscle fibers and muscles can be caused to contract rhythmically to produce heat.
Healing
• Blood vessels dilate flooding a damaged area with fluid to provide nutrients and oxygen.
• Cuts stimulate the epithelium cells to divide more rapidly than normal and new cells fill the gap.
• A deep cut provides clotting by escaping blood. Then fibroblast form new collagenous material to bind the edges of the wound.
• Blood vessels will then grow in this area and phagocytic cells will clear debris and new tissue will be formed as a scar.
Skin Trivia• About 2 million sweat glands are in the
hands.• If the skin of a 150-pound person were
spread out flat, it would cover approximately 20 square feet.
• Skin cells help produce vitamin D, which is necessary for normal bone and tooth development.
• Just above the base of the hair follicle are stem cells that can be used to grow hair or new epidermal cells for burn patients.
• Most of the body’s heat (80%) escapes through the head.
More Skin Trivia
• The average square inch of skin holds 650 sweat glands, 20 blood vessels, 60,000 melanocytes, and more than a thousand nerve endings.
• The thumbnail grows the slowest; the middle nail grows the fastest.
• When a person lies in one position for a prolonged period, the weight of the body pressing against the bed blocks the skin’s blood supply, causing cells to die, tissues to breakdown, and a pressure ulcer (bedsore) may form.
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