Skin and Body Membranes Chapter 4

Body Membranes-Functions Line or cover body surfaces Protect body surfaces Lubricate body surfaces

Epithelial Membranes Made of epithelium connected to underlying connective tissue Skin Cutaneous membrane Exposed to air = Dry membrane Made of keratinized stratified squamous epithelium

Epithelial Membranes, cont. Mucous membranes Type of epithelium depends on location of membrane Most are stratified squamous OR simple columnar Lines all body cavities open to exterior Respiratory tract Digestive tract Urinary & Reproductive tracts Wet membranes (bathed in secretions continuously) Underlying connective tissue is lamina propria

Epithelial Membranes, cont. Serous Membranes Simple squamous tissue on areolar tissue Line cavities that are closed to exterior Occur in pairs Parietal layer-lines wall of a cavity Visceral layer-covers the outside of the organs inside the cavity Layers separated by fluid secreted by both membranes Allows organs to slide easily across cavity walls and each other Reduces friction (good for heart pumping, stomach churning, etc) Peritoneum-lining of abdominal cavity/covers organs Pleura-surrounds lungs Pericardium-surrounds heart

Epithelial Membranes, cont.

Connective Tissue Membranes Synovial Membranes Made of areolar tissue-NO epithelial cells Line joint capsules Provide smooth surface Secrete fluid for lubrication (reduces friction) Also provide cushion for movements of tendons over bones Tendon sheath

Integumentary System AKA…SKIN! AKA…Cutaneous membrane AKA…Integument Means “covering” Keeps water and nutrients IN the body Keeps water and other things OUT We don’t get waterlogged when we shower or swim!

Skin Functions Protects body from: Mechanical damage (bumps) Physical barrier and pressure receptors Chemical damage Impermeable cells; pain receptors Bacterial damage Skin secretions acidic; inhibit bacteria UV radiation Contains melanin Thermal damage Heat/cold damage Has heat/cold/pain receptors Dessication Drying out

Skin Functions, cont. Aids in heat loss/retention Activates sweat glands and allows blood to flush into capillaries for heat loss Not allowing blood to flush into capillaries for heat retention Helps excrete urea and uric acid Sweat glands Makes vitamin D Sunlight converts cholesterol in skin to vitamin D

Skin Structure Epidermis Outer layer Keratinized stratified squamous cells No blood supply of its own (avascular) Dermis Dense connective tissue Can separate from epithelium due to burns/friction Causes blisters Hypodermis (Subcutaneous Tissue) Technically…not part of skin Adipose (fat) Anchors skin to underlying organs Shock absorber Insulates deeper tissues from extreme temp. changes

Epidermis Layers Stratum basale Stratum spinosum Stratum granulosum Deepest layer Next to dermis Cells are undergoing mitosis AKA Stratum germinativum Cells get nutrients via diffusion from dermis Cells get pushed up to move farther away from nutrient supply Stratum spinosum Stratum granulosum

Epidermis Layers, cont. Stratum lucidum Stratum corneum Clear, flattened cells full of keratin Only in areas where skin is hairless and extra thick Palms of hands Soles of feet Stratum corneum Outermost layer Shingle-like cells Dead cells Provides protective “coat” for body Rubs/flakes off slowly We have a totally new epidermis approximately every month!

Melanin Pigment produced by melanocytes In stratum basale Exposure to sunlight causes melanocytes to make melanin More melanin = more skin pigmentation = TAN Amount of melanin produced depends on: Amount of sun exposure Genetics Freckles/Moles Concentration of melanin in one spot

Dermis “Hide” Strong, stretchy, holds body together Two regions Papillary layer Contains fingerlike projections “dermal papillae” Has capillary loops for nutrient supply Pain/touch receptors Makes up our fingerprints (whorls, ridges) Reticular layer Deepest skin layer Contains blood vessels, sweat glands, oil glands Has pressure receptors

Skin Structure

Skin Color Determination Amount/kind of melanin in epidermis Can be yellow, reddish brown, or black Amount of carotene Yellowish-orange pigment (think carrots) If you eat LOTS of foods this color, your skin will look this color also! Hemoglobin Protein in red blood cells-carries oxygen Lots of melanin = brown toned skin Oxygen rich hemoglobin causes skin to look pink When Caucasians look “flushed”

Imbalances Abnormal yellow skin tone Can be due to liver disorder Cyanosis When oxygen content in blood is low Bluish-tinted skin (“cyan”) Erythema Redness/”flushing” Caused by blood rushing to capillaries near skin’s surface Pallor/blanching Pale skin Can be due to anemia, low BP, impaired blood flow Jaundice Abnormal yellow skin tone Can be due to liver disorder Bruises Sites where blood has escaped from circulation and clotted Tendency toward unusual bruising could mean vit. C deficiency or hemophilia

Skin Appendages Cutaneous Glands Exocrine glands Release secretions to surface of skin through ducts Two types: Sebaceous glands Sweat glands

Sebaceous (oil) Glands All over skin EXCEPT hands/feet Ducts empty into hair follicle Release sebum Oily substance and cell fragments Lubricant Keeps skin soft, keeps hair from being brittle Antibacterial properties Glands become more active during puberty Pimples! Whitehead Caused by blocked sebaceous gland Blackheads When material inside whitehead dries out Cradle cap (seborrhea) In infants Sebaceous glands are overactive Looks like lots of oily dandruff on scalp

Sweat Glands (Sudoriferous Glands) Eccrine Glands More numerous/all over body Open to pores on skin surface Produce sweat Important for heat regulation Apocrine Glands Only found in axillary and genital areas Larger than eccrine glands Ducts empty into hair follicles

Sweat Composition Mostly water Waste products Fatty acids and proteins (from apocrine glands only) Color Clear (eccrine) Milky white/yellowish (apocrine…due to FA’s and proteins) Function Heat regulation (gets rid of excess heat) Waste excretion Acidic-naturally inhibits bacteria Odor Sweat is ODORLESS!! The smell is from bacteria on skin When bacteria use sweat for nutrients, it is smelly!

Skin Appendages Hair Produced by hair bulb Made of keratinized epithelial cells (dead…mostly protein) Color comes from pigment in melanocytes Found everywhere EXCEPT palms, soles, nipples, lips

Hair Anatomy Medulla Central core Cortex Surrounds medulla Cuticle Outermost layer Single layer of overlapping cells (like shingles) Has the most keratin Provides strength Split Ends? Caused when cuticle is worn away at the tip of the hair shaft…keratin frizzes out…hair “splits”

Other Hair-Related Structures Hair Follicle Inner epidermal sheath= hair Outer dermal sheath= connective tissue Supplies blood to epidermis Arrector pili Smooth muscle Connects hair follicle to dermis When contracted, we see “goose bumps” and hairs are pulled upright Sebaceous glands

Skin Appendages Nails Modification of epidermis Scale-like Contain lots of keratin Mostly non-living material Stratum basale under nail bed resposible for growth Colorless No pigment Appear pink due to blood supply in underlying dermis

Burns Tissue damage/cell death caused by heat, electricity, UV radiation (sunburn/tanning bed), chemicals Can result in life-threatening problems Dehydration-lose fluid supply, electrolyte imbalance Leads to kidney shutdown and circulatory shock Lost fluids must be replaced immediately!

Burns Rule of Nines How to estimate fluid loss from a burn Divides body into different regions, each being 9% (except genital area is 1%)

Burn Classification First-degree Second-degree Third-degree Only epidermis is damaged Red, swollen Regeneration occurs Ex: sunburn Second-degree Damage to epidermis and upper dermis Red, painful, blisters Third-degree Full-thickness burn Grayish white or black (looks charred) Destroys nerve endings Not painful Regeneration NOT possible Must use skin grafting

Burn Classification

Critical Burns Over 25% of body has second-degree burns Over 10% of body has third-degree burns There are third-degree burns on face, hands, or feet Facial burns dangerous Possible burned airways Can swell, cause suffocation Joint injuries Scar tissue can limit joint mobility

Skin Cancer Most common type of cancer Two Types Benign Risk factors: Overexposure to UV radiation (sun/tanning bed) Frequent skin infections or chemical irritation Two Types Benign Do not spread Malignant Metastasizes (moves) to other parts of body

Skin Cancer Basal Cell Carcinoma Squamous Cell Carcinoma Least malignant Most common Occur most often on sun-exposed areas Slow-growing 99% have full cure if lesion is removed surgically Squamous Cell Carcinoma Scaly, red; eventually forms shallow ulcer with raised border Occurs most often on scalp, ears, hands, lip Fast-growing Good chance of cure if removed surgically or use radiation therapy

Skin Cancer Malignant Melanoma Cancer of melanocytes (cells that make melanin) 5% of skin cancers Often deadly Can begin anywhere there is pigment Develops spontaneously, some from moles 50% survival rate Examine skin for new moles or pigmented spots periodically Use ABCD Rule of Detection

ABCD Rule of Detection (A) Asymmetry Two sides of mole do not match (B) Border irregularity Borders of mole/lesion are not smooth (C) Color Spot has areas of different colors instead of being one color throughout (D) Diameter Spot larger than 6mm (larger than pencil eraser)