Chapter 3 Presentation

Presentation By Francine King Integumentary System Chapter 3

The Integumentary System Integumentary System Includes:
Skin (cutaneous membrane)
Subcutaneous tissue below the skin
Accessory Structures
Sweat glands
Sebaceous or oil glands
Hair
Nails

Layers Of The Skin
Epidermis outer
composed of stratified squamous epithelium
Dermis inner
anchored to a subcutaneous

Epidermis
Composed of stratified squamous epithelium
Avascular as it has no blood supply of its own
Oxygen and nutrients diffuse from the underlying dermis
The epidermis is a keratinized stratified squamous epithelium. Oxygen and nutrients diffuse from the underlying dermis. Five structurally different layers can be identified:

First Layer of the Epidermis The stratum basale is the deepest layer of the epidermis (closest to the dermis). It is found close to the dermal blood supply. It consists of a single layer of columnar or cuboidal cells which rest on the basement membrane. Basal cells are the stem cells of the epidermis. Their mitotic activity replenishes the cells in more superficial layers as these are eventually shed from the epidermis. The renewal of the epidermis takes about 3 to 4 weeks in humans as millions of cells are produced daily. Cells die as they are pushed away from the source of nourishment. Cells undergo keratinization as a tough protein, keratin, is deposited within the cell. Keratin hardens and flattens the cells as they move outward and it waterproofs the skin.

Optional Epidermal Layers
In the stratum spinosum, the cells become irregularly polygonal. The cells are often separated by narrow, translucent clefts. These clefts are spanned by spinelike cytoplasmatic extensions of the cells (hence the name of the layer and of its cells: spinous cells), which interconnect the cells of this layer.
The stratum granulosum consists, in thick skin, of a few layers of flattened cells. Only one layer may be visible in thin skin.
The stratum lucidum consists of several layers of flattened dead cells. Nuclei already begin to degenerate in the outer part of the stratum granulosum. In the stratum lucidum, faint nuclear outlines are visible in only a few of the cells. The stratum lucidum can usually not be identified in thin skin.

Final Epithelial Layer
In the stratum corneum, cells are keratinized and form a layer that is about 30 cells thick. Individual cells are difficult to observe because (1) nuclei can no longer be identified, (2) the cells are very flat and (3) the space between the cells has been filled with lipids, which cement the cells together into a continuous membrane. Closest to the surface of the epidermis, the stratum corneum has a somewhat looser appearance. Cells are constantly shed from this part of the stratum corneum. This layer makes up three fourths of the epidermal thickness. The protection of the body by the epidermis is due to the functional features of the stratum corneum.

Dermis or corium
The dermis, or corium, consists of dense fibrous connective tissue with numerous collagenous and elastic fibers. The dermis is much thicker than the epidermis. In thick skin, dermal papillae create a very irregular border between epidermis and dermis. Blood vessels, nervous tissue, some muscle tissue, certain glands, hair and nails are found in the dermis. Nerve endings allow us to sense pain, temperature, pressure, and touch.

Melanin Red and Yellow, Black and White
The red and yellow hues of the skin are due to hemoglobin in the red blood cells, which pass through the capillaries beneath the epidermis, and carotene (yellowish pigment), which accumulates in fat cells found in thedermis and hypodermis (subcutaneous layer beneath dermis).
Melanocytes
The brown in skin color is due to melanin, which is produced in the skin itself in cells called melanocytes. These cells are located in the epidermis. In the melanocytes, the melanin is located in membranebound organelles called melanosomes. Melanocytes can transfer melanin to keratinocytes mainly to the basal cells. Melanin protects the chromosomes of mitotically active basal cells against lightinduced damage.

Malfunctioning Melanocytes
Albinism melanocytes completely fail to secrete melanin. Hair, skin, and iris are white.
Vitiligo loss of pigment in certain areas of the skin producing white patches.
Freckles and moles are formed when melanin becomes concentrated in local areas.
Malignant melanoma a cancerous change in a mole that may metastasize (spread) rapidly and is most difficult to treat. Exposure to sunlight increases risk.

Other Pigments in Skin
Carotene a yellow pigment in skin usually hidden by the effects of melanin. Asians have little melanin which allows the yellow to show more than other nationalities.
Pinkish color seen in fairskinned persons because the vascular dermis is visible.
Cyanosis blue look to skin due to poorly oxygenated blood
Blushing caused by dilation of blood vessels
Pale by fright caused by restriction of vessels

Response to Disease
Jaundice caused when bilirubin is deposited in skin because a diseased liver is unable to excrete this pigment
Skin may appear bronzed due to the deposit of excess melanin when a person's adrenal gland is functioning poorly.
A bruise indicates that blood has escaped from the blood vessels and has clotted under the skin.
Over eating carotenerich vegetables such as carrots may cause skin to have a yellow tint.

Accessory Structures of the Skin
Hair
A characteristic feature of the human skin is the apparent lack of hair on most of the body surface. This is actually not quite true. Most of the skin is haired although the hair in most areas is short, fine and only lightly pigmented.
Truly hairless are only the palms of hands and soles of feet, the distal phalanges and sides of fingers and toes and parts of the external genitalia.

Accessory Structures of the Skin
Nails
Plates of stratified squamous epithelial cells with hard keratin
Protect distal ends of phalanges
Cells are keratinized in the nail root
Nail growth occurs in the lunula
Cuticle is a fold of stratum corneum on the proximal end of nail

Exocrine Glands
Sebaceous glands or oil glands are simple branched areolar glands. They secrete the sebum (seb = oil) an oily product. Sebum is usually secreted into a hair follicle. Sebum is a natural skin cream: it helps hair from becoming brittle, prevents excessive evaporation of water from the skin, keeps the skin soft and contains a bactericidal agent that inhibits the growth of certain bacteria.
Sebaceous glands are scattered all over the surface of the skin except in the palms, soles and the side of the feet.
Vernix caseosa white covering on fetus.
Blackhead
Pimple

: Exocrine Glands
Sweat glands or sudoriferous glands are simple coiled tubular glands. They are divided into two principal types: eccrine and apocrine.
Apocrine glands are found mainly in the skin of the armpits, of the anogenital areas and of the areola of the breasts. Their secretory portion can be located in the dermis or in the hypodermis. Their excretory ducts open into hair follicles. Their secretion is more viscous than that of the eccrine glands. They start secreting at puberty and may be analogous to the sexual scent glands of other animals.
Eccrine glands are the most common. Their secretory portion can be located in the dermis or in the hypodermis. They produce sweat, a watery mixture of salts, antibodies and metabolic wastes. Sweat prevents overheating of the body and thus helps regulate body temperature.
Ceruminous glands (or ear wax glands) and mammary glands are modified apocrine sweat glands.

:
Three types of skin cancer corresponding to three major types of skin cells: basal cells, squamous cells, and melanocytes.
Cancer of melanocytes malignant melanoma is the most lethal variety, but also the least common.
If caught early, most cases of nonmelanoma skin cancer are easily treated under local anaesthetic
Whites in Australia have the highest rates of skin cancer of all types in the world.
The damaging effects of sunlight can occur many years before tumors appear.
ultraviolet light causes mutations at points on a DNA strand.

Chapter 3 Presentation

by francine king on Sep 16, 2009

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