Skin and Body Membranes Chapter 4

Classification of Body Membranes The two major categories of body membranes – epithelial connective

Epithelial Membranes Cutaneous – skin; mucus membrane; serous membrane Mucous - Lamina propria – lines body cavities opening to exterior. Serous – lines cavities closed to exterior – serous fluid allows organs to move without friction. *Heart

Serous membranes Peritoneum –lining of abdominal cavity Pleura – lining around lungs Pericardium – lining around heart

Integumentary System Defined Consists of skin, hair, nails, and sweat glands. Function – protect internal structures prevent infectious agent entry regulate temp, produce vitamin D prevent water loss detect stimuli such as touch, pain and temp.

Skin 2 major tissue layers A. Dermis – layer of dense connective tissue B. Epidermis – epithelial tissue layer, rests on dermis

Epidermis Stratified squamous epithelium. Cells from mitosis in the deep layers. Keratinization – Keratin filled cells Stratum corneum – outer layer of epidermis. Increasing layers produces thickened areas - callus. Over bony area - corn.

Dermis Dense connective tissue with fat cells. Collagen and elastic fibers, structural strength to skin

Integumentary System Day 2

Dermis Incisions across cleavage lines, produce scar tissue. (parallel incisions, less scars) overstretched skin leaves lines called striae or stretch marks in dermis

Striae

Structure of the Skin Hypodermis - under dermis, or subcutaneous tissue Attaches skin to muscle, bone or connective tissue ½ body’s stored fat Fat – padding and insulation;

Skin Color Determined by pigments in the skin, blood circulation in skin, and thick stratum corneum. Melanin – brown to black pigment in skin. Melanin produced by melanocytes transfer melanin to epithelial cells. Freckles, moles, nipples - large amounts of melanin

Skin Color Amount of melanin determines racial variations Genetic factors, hormones, and exposure to light determine color Albinism –mutation causes a deficiency or absence of melanin. fair skin, white hair, unpigmented irises in the eye. cyanosis – skin turning blue - lack of oxygen both in blood and skin. heart failure and breathing disorders.

Glands Sebaceous Glands – produce sebam – an oily, white substance rich in lipids. Lubricates hair and skin, prevents drying.

Sweat Glands More than 2.5 million per person Eccrine sweat glands – almost every part of skin. Numerous in palms of hands, soles of feet Sweat is released to cool off body. It is acidic – pH 4.6

Apocrine Sweat Gland Produce a thick milky or yellowish secretion Causes body odor from bacteria on the skin.

Integumentary System Day 3

Hair

characteristic to mammals, scattered all over the body. Shaft – protrudes above skin surface Root and hair bulb matrix– below skin Cortex – hard outer covering Medulla – soft, center of the hair Cuticle – covers cortex, holds hair in follicle.

Hair produced in hair bulb Eyelashes grow for ~30 days, rest for ~105 days. Scalp hairs grow for 3 years, rest for 1 to 2 years. Hair color determined by melanin, decreases with age causing gray hair. smooth muscle cells (hair follicle)called arrector pili. The contraction of the arrector pili causes the hair to stand on end. (goose bumps)

Nails Thin plate, consisting of keratin. Nail body – visible part Nail root – covered by skin Cuticle – grows out onto nail body Lunula –whitish, crescent shaped, base of nail. From which the nail grows. Nails grow continuously

Imbalances of Skin Athlete’s Foot – an itchy, red - resulting from fungus infection – tinea pedis Boils and carbuncles – inflammation of hair follicles and sebaceous glands, common the neck. Usually caused by bacteria. Cold sores – (fever blisters) – caused by herpes simplex infection. Usually occur around the lips or mouth.

Cont. Contact dermatitis – itching, redness, and swelling. exposure to chemicals in poison ivy. Impetigo – pink, water filled, raised lesions, develop yellow crust and rupture. Caused by contagious staphylococcus infection. Common in school aged children. Psoriasis – a red epidermal lesion covered with dry, silvery scales. Cause unknown. Attacks may be triggered by stress, trauma, infection or hormonal changes.

Burns tissue damage and cell death caused by intense heat, electricity, UV radiation (sun burn), or chemicals. Rule of nines – divides body into 11 areas, each for 9% of total body surface area. See page 104 for example

Burn

Skin Cancer Basal Cell Carcinoma – common type, open ulcer, surgical removed Squamous Cell Carcinoma – scaly, reddened papule, ulcer with raised boarder, easily treated with early detection. Malignant melanoma – skin cancer of melanocytes, usually in moles, can be fatal.

ABCD Rule A – Asymmetry - two sides of pigmented spot or mole do not match. B – Border irregularity –borders of lesion are not smooth C – Color – contains areas of different colors (black, brown, tans, blues & reds) D – Diameter –larger than 6 mm in diameter.