The Integumentary System Gimme some skin!!

Objectives…. Describe the structure and function of the skin. Give the basis for different skin colors

Skin facts: Also known as the cutaneous membrane Covers the external surface of the body The body’s largest organ Weighs10-11 lbs about 16% of total body weight. Covers a surface area of about 22 sq. ft.

1 inch of skin contains… 65 hairs 100 sebaceous (oil) glands 78 yards of nerves 650 sweat glands 19 yards of blood vessels 9,500,000 cells 1,300 nerve endings

Functions of the Skin Protect from injury and dehydration Body temperature control Excretion of some wastes Receptor of external stimuli Defense against microbes Vitamin D synthesis Absorption

Structure of the Skin The skin consist of the: Epidermis Dermis Hypodermis or subcutaneous (subQ) layer. (adipose tissue and blood vessels).

The Epidermis: Composition: keratinized stratified squamous epithelium and 4 cell types: Keratinocytes: produce protein keratin. Melanocytes: make melanin, the pigment that gives skin its color. Langerhans cells: Aid in immune response. Merkel cells: Aid in touch sensations.

5 Epidermal Layers Stratum corneum: Superficial layer, 25-30 layers of dead keratinocytes that are continuously shed and replaced. Thickening of this layer results in a callus. Stratum lucidum: Only found in the thick skin of the fingertips, palms and soles. Contains large amounts of keratin. Stratum granulosum: Constantly undergoing apoptosis (programmed cell death). Release a lipid-rich secretion that prevents loss of body fluids.

5 Epidermal Layers cont’d… Stratum spinosum: (spinos- = thornlike) 8 –10 layers of flattened keratinocytes. Stratum basale: The deepest layer of the epidermis. Some cells are stem cells that under go cell division to continuously produce new cells (keratinocytes).

The Dermis Composition: Mainly connective tissue containing collagen and elastic fibers. Contains small, fingerlike projections called dermal papillae. The dermal papillae contain blood capillaries and tactile receptors. The deeper part of the dermis contains fat cells, hair follicles, nerves, oil glands and sweat glands and is attached to the subQ layer.

Dermal Facts… The tactile receptors (corpusucles of touch & Meissner corpusucles) are associated with the sensations of warmth, coolness, pain, tickling and itching. The collagen and elastic fibers provide the skin with strength, extensibility (stretching) and elasticity (returning to original shape). Ex. Pregnancy and obesity. ** Extreme stretching can cause tears in the dermis causing striae, better known as ‘stretch marks.’

                             Skin Color                                                  

3 pigments found in skin: 1. Melanin – Causes skin color to range from pale yellow to tan to black. Melanocytes are most plentiful in the epidermis of the penis, nipples of breast, areolae, face and limbs. The amount of pigment in the melanocytes causes the variance in skin color. Accumulations of melanin in patches causes: freckles & age (liver) spots.

Carotene – a. Is a yellow-orange pigment that gives egg yolks and carrots their color. b. Precursor of vitamin A (makes pigments needed for vision). c. Found in the fatty areas of subQ. d. When little carotene or melanin is present the skin appears translucent.

Hemoglobin – a. In white people gives skin a pink to red color. b Hemoglobin – a. In white people gives skin a pink to red color. b. Oxygen carrying pigment in red blood cells.

Albinism (albin- = white) The inherited inability of an individual to produce melanin. Most albinos also lack melanin in their hair and eyes as well as the skin.

Psoriasis A skin disorder where keratinocytes divide and move more quickly than normal (As little as 7- 10 days). This shedding forms flaky, silvery scales at the skin’s surface, most often on the scalp (dandruff), knees and elbows.

Eczema Eczema is an inflammation of the skin and may be associated with an allergic reaction. Eczema affects more than 15 million Americans and ten percent of all children have eczema.

Other disorders include: Jaundice: Caused by a bilirubin (protein) build up in blood giving the skin and eyes a yellowish appearance. Usually indicates liver disease in adults. Cyanotic: A bluish-purplish tint to the skin caused by lack of oxygen in hemoglobin. Erythema: Redness of the skin, caused by engorgement of capillaries in the dermis. Caused by skin injury, exposure to heat, infection, allergic reaction and inflammation.

Jaundice, Cyanosis & Erythema

Fungal Infections of Skin… Ringworm Athlete's Foot White Spot Candidiasis