Skin & Body Membranes Chapter 4

FACTS ABOUT THE SKIN Called the Integument: means covering. Covers entire body. Wt. Approximately 9 pounds. 7% of total body wt. 4

Facts Cont. Every square centimeter of skin contains: -70cm of Blood Vessels -55cm of nerves (230 sensory receptors) -100 sweat glands -15 oil glands -1/2 million cells dying and are constantly being replaced.

I. Classification of Body Membranes

A. Epithelial Membranes Epithelial sheet Underlying layer of connective tissue

1. Cutaneous Membrane Skin Keratinizing stratified squamous epithelium Anchored by dense fibrous CT

2. Mucous Membranes Epithelium varies Underlying loose CT Lines all cavities open to exterior

3. Serous Membranes Layer of simple squamous Layer of areolar CT Lines body cavities closed to exterior Made of two layers Parietal: lines cavity Visceral: cover outside of organs in cavity Serous fluid in between layers Decrease friction

Figure 4.1 Classes of epithelial membranes

B. Connective Tissue Membranes Synovial Membranes: soft areolar CT No epithelial cells Line fibrous capsules surrounding joints Provide smooth surface & secrete lubricating fluid

II. Integumentary System

A. Basic Skin Functions Mechanical Damage: keratin toughens cells Pressure receptors alert nervous system to possible damage Chemical damage: keratinized cells relatively impermeable Pain receptors alert nervous system

Bacterial Damage: secretions are acidic & inhibit bacteria Phagocytes ingest foreign substances & pathogens Ultraviolet radiation: melanin produced by melanocytes offer protection Thermal Damage: heat, cold, & pain receptors Desiccation: keratin in cells reduce evaporation

Heat loss: activating sweat glands Allowing blood to flush into skin capillary beds Heat retention: reducing flow of blood into skin capillary beds Excretion of urea & uric acid in sweat Modified cholesterol molecules in skin converted to vitamin D by sunlight

B. Types of Nerve Endings Cutaneous sensory receptors - (exteroceptors) - respond to stimuli outside the body. Meissners Corpuscles in dermal papillae - sense gentle touch and feel in the skin

Pacinian receptors - deeper dermis - deeper pressure Root Hair Plexuses - wind in the hair Bare nerve endings - sense cold, heat etc.

C. Structure of the Skin Most superficial: Epidermis Second Layer: Dermis Hypodermis: not actual skin but is known as the fat layer of the skin. Underneath the dermis Mostly fat, insulate and absorb shock Anchors skin to underlying structures 5

Epidermis: 4 Cell types 6

1. Keratinocytes: main structural cell…new epidermis every 35-45 days Produce Keratin: fibrous protein used for protection. 2. Melanocytes: give skin color, accumulate on superficial side of keratinocytes. 3. Langerhans cells: macrophages of the immune system. 4. Merkel Cells: Combines with nerve receptors to form Merkel disc which is sensitive to touch. 7

5 layers of Epidermis (pg. 100 fig. 4.3) 1. Stratum Basale (Basal Layer) -Mostly young Keratinocytes, -One cell layer thick 8

2. Stratum Spinosum (Spiny Layer) - Mostly Langerhans cells that surround keratinocytes that are flat and prickly. -Keratinocytes in this layer contain tonofilaments: -Thick bundles of tension fibers 9

3. Stratum Granulosum (Granular Layer) -3-5 Layers of Keratinocytes -Tough Layer -Water resistant, to slow water loss from the body 10

4. Stratum Lucidum (Clear Layer) -Only present in thick skin -Mainly 2-3 rows of Keratinocytes 11

5. Stratum Corneum (Horny Layer) -Outermost layer, mostly dead keratinocytes or keratin filled cells -20-30 layers thick, thickest layer - prevent abrasion and penetration -Waterproofing from environment -Protects deeper cells 12

Dermis: 2nd Layer of Skin Hide of our skin Richly supplied with nerves, blood & lymph vessels. Cell types are mostly macrophages & fibroblasts. House major portion of hair follicles, oil and sweat glands. 13

The dermis has 2 major layers 1. Papillary Layer: connect epidermis to dermis - Contain the majority of blood vessels. - Form identifying finger and foot prints. 14

2. Reticular Layer - 80% of the Dermis - Dense irregular connective tissue - Form cleavage lines: skin heals better when an incision is made along these lines. 15

- If overstretched such as in pregnancy, dermal tears form striae or sretchmarks. - Blister: Separation of Epidermis from Dermis, fluid filled.

D. SKIN COLOR 3 PIGMENTS CONTRIBUTE TO SKIN COLOR 16

1. MELANIN -Color ranges: yellow - reddish brown - black -More melanin the darker the color. Freckles and moles are local accumulation of melanin. -Sun exacerbates melanin buildup 17

2. CAROTENE Color range: yellow - orange. Found in certain plants: carrots, rich sources of Vitamin A. Most found in the palms and soles. 18

3. HEMOGLOBIN Color range: - Pale: caused by lack of blood. Yellow: caused by build up of bile in the blood (Jaundice). Blue: cyanosis, lack of oxygen Pink: Normal hue 19

Bronze: Addisons disease, metallic appearance Blue: Lack of Oxygen (cyanosis). Redness: Erythema, blushing, inflammation, or hypertension. Bruises: blood has escaped & clotted in tissue spaces 20

E. APPENDAGES OF THE SKIN 21

1. HAIR AND HAIR FOLLICLES - Hair (Pili): made of keratin Shaft: projects from the skin Root: embedded in skin, depending on shape signifies, straight or curly hair. - Hair pigment depends on melanocytes located in follicle 22

- Hair Follicles (pg. 105 fig. 4.7) - contains hair root - Nerve endings - Knot of capillaries: papilla, to supply nutrients - Bundle of smooth muscle: arrector pili: raiser of hair. 23

2. Distribution of Hair growth Fine Vellus: fine body hair of children or females Terminal hair: course scalp hair and eyebrows - grow in response to sex hormones, the more testosterone the more terminal hair 24

Male patterned baldness: genetic and sex-influenced condition Alopecia: hair loss, as we get older new hairs do not replace old hairs as quickly. Male patterned baldness: genetic and sex-influenced condition 25

3. Nails Hard keratin 26

4. Sweat Glands sudoriferous glands -Cover entire skin surface except for nipples, and parts of external genitalia. 2.5 million per person 27

Types of Sweat Glands Eccrine: most numerous location: palms, soles of feet, forehead secretion: sweat 99% water, salts, nitrogenous wastes acidic pH 4-6 purpose: temperature regulation emotion induced sweating, we have no control 08/02/98 28

Apocrine: Location: axillary, genital areas Size: Larger than eccrine glands Secretions: same as eccrine plus fatty deposits and protein. - Has foul odor when fats and proteins are decomposed (body odor) -Begin to function at puberty 31

5. Sebaceous (oil) glands Location: all over the body except for palms and soles of feet. Secretion: Sebum, oily substance Function: smooth and soften hair and skin and slows water loss during dry weather. Acne: active inflammation of gland Bacteria 34

Blocked duct: Whitehead is formed if this oxidizes and dries it becomes a blackhead Seborrhea: (Cradle Cap) in infants is over secretion of sebaceous glands 35

III. Homeostatic Imbalances 39

A. Burns Partial thickness burns - 1st and 2nd degree Full thickness burns - 3rd degree 40

1. Problem with burns Fluid and electrolyte imbalance Shock Infection 41

2. Treatment Dependent on percentage of burn calculated by the Rule of nines. pg. 108 fig. 4.11 Fluid and electrolyte replacement Antibiotics Supportive care Debridment of eschar(burned skin) Grafting

B. Skin Cancer 1. Basal Cell Carcinoma most common, least malignant, slow growth Pearly edge 99% cure rate with early excision

2. Squamous Cell Carcinoma In keratinocytes of the stratum spinosum Scaly red papule (round elevated) rapid growth, meets to lymph Good cure rate if caught early and radiation is followed through.

3. Malignant Melanoma CA of Melanocytes Most dangerous Accounts for about 5% of Skin CAs Little chance of survival, better if caught early Tx is surgical excision with chemotherapy

4. American Cancer Society ABCD rule for examination of skin CA A - Asymmetry B - Border irregularity C - Colors different D - Diameter is larger than 6mm (pencil eraser)