Lecture: Chapter 05 Flashcards
INTEGUMENTARY SYSTEM
Skin. Composed of TWO distinct regions: the dermis and epidermis.
EPIDERMIS
epithelial cells; outer covering of body; it is AVASCULAR and gets nutrients by way of diffusion.
DERMIS
fibrous co. annective tissue, leathery, vascularized; provides nutrients to epidermis by diffusion.
HYPODERMIS
a.k.a. “Superficial Fascia;” subcutaneous tissue just deep to the skin; mostly ADIPOSE tissue; anchors skin to underlying layer (usually muscle). The adipose (fat) acts as an insulator and shock absorber.
THE EPIDERMIS
keratinized stratified squamous epithelium. Consists of 4 types of cells: 1) Keratinocytes, 2) Melanocytes, 3) Langerhans’ cells, & 4) Merkel cells. (see following cards)
KERATINOCYTES
produce keratin, the fibrous protein that is responsible for toughening of the skin and gives the epidermis its protective properties. New cells continually produced which pushes older cells upward (superficially). They are DEAD when they reach the free surface of the skin. These cells SLOUGH OFF for totally new layer every 25-45 days. Persistent friction causes a thickening of the epidermis called a CALLUS.
MELANOCYTES
synthesize pigment melanin; melanin accumulates on the superficial side of the keratinocyte’s nucleus, protecting it from harmful UV radiation. (Melanin acts as an umbrella preventing modification of DNA in nuclei that would lead to abnormal (cancer) cells). Everyone has SAME # of melanocytes.
LANGERHANS’ CELLS
a.k.a. “Dendritic Cells;” Macrophages; work with immune system; these are phagocytic cells that arise from bone marrow & migrate to epidermis.
MERKEL CELLS
touch receptors; located at dermal-epidermal junctions.
LAYERS OF THE EPIDERMIS
Cornum, Lucidum, Granulosum, Spinosum, Basale.
Can Lucy Give Some Blood
STRATUM CORNUM
outermost layer, 20-30 cells thick; protects skin from abrasion, penetration, and wter loss; provides a durable overcoat.
STRATUM LUCIDUM
clear layer only visible in thick skin (on palms and soles); thin, translucent band.
STRATUM GRANULOSUM
granular layer; 3-5 layers; as cells move up they flatten, nuclei & organelles disintegrate, and they build up KERATOHYALINE granules & LAMELLATED granules, which PREVENT excessive WATER LOSS through the skin. The keratohyaline granules form keratin in the upper layers; the lamellated granules contain a water-proofing glycolipid and decrease water loss.
STRATUM SPINOSUM
prickly layer; the keratinocytes appear irregular and spiny (in tissue samples, not living cells); This layer contains melanin granules and Langerhans’ cells.
STRATUM BASALE
basal layer; the deepest epidermal layer; attached to dermis; single row of cells undergoing rapid mitotic division. This layer also contains melanocytes and a few Merkel cells.
THE DERMIS
strong and flexible (vascular also) connective tissue, similar to animal hides used for leather; contains nerve fibers, blood vessels, and lymphatic vessels; also parts of hair follicles and oil and sweat glands (derived from epidermal tissue but “live” in the dermis); Contains 3 Kinds of Cells: 1)Mast_Cells, 2)Macrophages, 3)Fibroblasts
LAYERS OF THE DERMIS
Papillary Layer and Reticular Layer (also, flexure lines)
PAPILLARY LAYER
80% of dermis; areolar connective tissue with many blood vessels; superior surface has dermal papillae that project into the epidermis. Many papllae contain free nerve endings (pain receptors) or Meissner’s corpuscles (touch receptors). On the palms and soles, the papillae lie on dermal ridges, which force the overlying epidermis to form epidermal ridges that increase gripping ability. These ridges are unique to each of us and give rise to fingerprints.
3 FUNCTIONS OF
PAPILLARY LAYER
1) Feed & oxygenate the dermis
2) Provide touch & pain receptors
3) Form ridges on palms and soles
RETICULAR LAYER
dense, irregular connective tissue; major portion of the dermis. The thick collagen fibers run in different planes but mostly parallel to the skin. These are separated b less dense regions which form cleavage or tension lines in skin. The tension lines are not visible but are important for surgery. The run up and down the limbs but around the head and trunk.
*Pacinian Corpuscle = pressure receptor
FLEXURE LINES
dermal folds occurring near joints where the dermis is secured to deeper structures, e.g. lines on the palms, fingers, and wrists.
SKIN COLOR
Determined by 3 pigments:
1) Melanin, 2) Carotene, & 3) Hemoglobin
(see following cards)
Can indicate a medical condition, a disease, or an emotion.
MELANIN
yellow to reddish-brown to black color. Local accumulations of melanin are freckles of pigmented moles. Long sun exposure causes a build-up of melanin - a tan which helps protect skin DNA from UV light damage.
CAROTENE
yellow to orange pigment, common in carrots. It tends to accumulate in the stratum corneum and fatty tissues of the hypodermic. Most obvious in palms and soles where stratum corneum is the thickest.