Organs and organ systems INTEGUMENTARY SYSTEM ORGANS OF

Organs and organ systems INTEGUMENTARY SYSTEM

ORGANS OF THE INTEGUMENTARY SYSTEM Skin (cutaneous membrane) Subcutaneous tissue below the skin Accessory Structures Sweat glands Sebaceous or oil glands Hair Nails

INTEGUMENTARY SYSTEM Protects the body's internal living tissues and organs Lubricates and waterproofs the exterior Protects against invasion by infectious microorganisms

Protects the body from dehydration Helps to regulate body temperature Excretes and expels toxins and waste materials Sense receptors for touch, pressure, pain, heat and cold Stores water, fat, and vitamin D

SKIN Outer covering of the body Largest organ

LAYERS OF THE SKIN • epidermis- stratified squamous epithelium basement membrane • dermis- largely connective tissue; many nerves and blood vessels; smooth muscle • hypodermis- adipose tissue and more loose connective tissue

EPIDERMIS Composed of stratified squamous epithelium Avascular -no blood supply of its own Oxygen and nutrients diffuse from the underlying dermis The epidermis is a keratinized stratified squamous epithelium.

Five structurally different layers can be identified: 1. stratum basale 2. stratum spinosum 3. stratum granulosum 4. stratum lucidum 5. stratum corneum

STRATUM BASALE deepest layer(closest to the dermis) found close to the dermal blood supply. consists of a single layer of columnar or cuboidal cells which rest on the basement membrane. 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 Stratum spinosum the cells become irregularly polygonal the cells are often separated by narrow, translucent clefts. These clefts are spanned by spine-like cytoplasmatic extensions of the cells (hence the name of the layer and of its cells: spinous cells), which interconnect the cells of this layer. .

Stratum granulosum in thick skin consists of a few layers of flattened cells. Only one layer may be visible in thin skin

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.

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

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 Consists of dense fibrous connective tissue with numerous collagenous and elastic fibers. 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.

SKIN COLOR 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 the dermis and hypodermis (subcutaneous layer beneath dermis).

Different skin color

MELANIN The brown in skin color produced in the skin itself in cells called melanocytes. These cells are located in the epidermis In the melanocytes, the melanin is located in membrane- bound organelles called melanosomes Melanocytes can transfer melanin to keratinocytes - mainly to the basal cells.

Melanin protects the chromosomes of mitotically active basal cells against light-induced damage. Pigmentation is not just under the control of light. Hormones produced by the pituitary and the adrenal glands also affect pigmentation. Diseases of these two endocrine organs often result in changes of pigmentation of the skin.

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.

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 fair-skinned 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 DISEASES 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 carotene-rich 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. Hairless-palms of hands and soles of feet, the distal phalanges and sides of fingers and toes and parts of the external genitalia.

In those parts of the skin which we perceive as "hairy" we find terminal hairs. The free part of each hair is called the shaft. The root of each hair is anchored in a tubular invagination of the epidermis, the hair follicle, which extends down into the dermis and, usually, a short distance into the hypodermis. The hair that you groom daily is actually dead keratinized cells.

Each hair follicle has an associated bundle of smooth muscle, the arrector pili muscle. This muscle inserts with one end to the papillary layer of the dermis and with the other end to the dermal sheath of the hair follicle. This makes your hair stand up on its end.

Hair color is determined by the amount and type of melanin present. Melanocytes become less active with age. Gray hair is a mixture of pigmented and nonpigmented hairs. Red hair results from a a modified type of melanin that contains iron.

The shape of the hair shaft determines texture. Round shaft – straight hair Oval shaft – wavy hair Flat shafts – curly or kinky hair Perms use chemicals to flatten shafts and makes hair curly. Alopecia is the term for hair loss.

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

Two types of exocrine glands Sebaceous- sebum (oil, wax) associated with hair follicles helps maintain pliability of skin Sweat glands apocrine (armpits, groin) merocrine (eccrine)- widely distributed important for maintaining body temperature

AGING AND THE INTEGUMENTARY SYSTEM Declines in: Cell division in stratum basale Melanocyte production Glandular activity Hair follicle function Elastic fiber function in dermis Blood supply to skin Rate of repair

QUIZ 1 -2 Give 2 functions of the skin 3 -4 Give 2 accessory structures of the skin 5 -7 3 layers of the skin 8 -10 Give 3 layers of the epidermis