Introduction Skin and Body Membranes Body membranes Cover surfaces Line body cavities Form protective and lubricating sheets around organs Classified in 5 categories Epithelial membranes 3 types- cutaneous, mucous, and serous Consist of epithelial sheet and connective tissue Cutaneous Membranes Skin Stratified squamous epithelium on epidermis Underlying dermis is dense (fibrous) connective tissue Mucous Membranes Epithelium on lamina propria Lines body cavities Often secretes mucous Often adapted for absorption and secretion Serous Membranes Simple squamous epithelium on areolar connective tissues Line body cavities that are closed to exterior 1
Serous Membranes, con t. Occur in pairs Parietal layer-lines portion of wall of ventral body cavity Visceral layer- covers outside of organs Separated by serous fluids Serous membranes, con t. Peritoneum- found around abdominal cavity Pleura- found around lungs Pericardium- found around the heart Connective tissue membranes Synovial membranes- have no epithelial cells Line fibrous capsules surrounding joints Integumentary System- Skin Includes skin and its derivatives Basic skin functions Makes us waterproof (keratin) Insulates and protects us from damage Regulates heat loss Makes vitamin D Structure of the Skin Epidermis Outer layer Stratified squamous epithelium Can keratinize (waterproofing) Epidermis 5 strata or layers Innermost- stratum basale- divides rapidly, contains melanin (yellow, brown, black pigments) Stratum spinosum Stratum granulosum Stratum lucidum- only on hands and feet Outermost- stratum corneum- 20-30 layers of dead cells 2
Epidermis Avascular (no blood supply) Keratinocytes- cells that make it tough and waterproof Structure of the Skin Dermis Middle layer of skin Made of dense connective tissue 2 layers Papillary layer is upper layer Covered in dermal papillae with capillaries, used for pain receptors and fingerprints Dermis 2 layers Reticular layer is deepest skin layer Contains blood vessels, sweat and oil glands, and deep pressure receptors Made of collagen and elastic fibers Structure of the Skin Hypodermis Innermost layer of subcutaneous tissue Made of adipose tissue Shock absorber Cutaneous glands Exocrine glands Formed in stratum basale and live in dermis Sebaceous (oil) glands Found all over the body Produce sebum for moisture and to kill bacteria Cause acne 3
Sweat (sudoriferous) glands Eccrine glands produce sweat which is acidic Regulate heat loss Apocrine sweat glands are found in the axillary and genital areas Also create fatty acids and proteins Bacteria cause them to smell Hair and hair follicles Found all over but have a vestigial function Root- found in the follicle Shaft- the hair we see, made of protein Hair bulb matrix- growth area Cuticle- outermost layer, overlapping Hair and Hair Follicles Each hair is medulla surrounded by the cortex surrounded by the cuticle Hair follicle is the epidermal sheath that forms the hair The dermal sheath supplies the blood vessels The erector pilli muscles move the hair Nails Modification of epidermis Made of a free edge, a body, and a root Sits on vascular nail bed Nail matrix- area of growth Infections and Allergies Athlete s foot- fungus Boils and carbuncles- inflammation of hair follicles and sebaceous glands, bacterial Cold sores- caused by herpes virus Infections and allergies Contact dermatitis- caused by exposure to chemicals Impetigo- staph infection Psoriasis- unknown cause, triggered by trauma and stress 4
Burns Affects almost all other systems First problem is dehydration Leads to circulatory shock Degree of seriousness determined by rule of nines- body is divided into 11 areas, each counting as 9% Next problem is infection Burns First degree burns- only damage epidermis Second degree burns- injure epidermis and upper layer of derms Third degree burns- destroy all skin, also called full thickness burns, have to graft to heal them Burns are critical if: 25% of the body is covered in second degree burns, OR 10% of the body is covered in third degree burns, OR There are third degree burns on the face, hands, or feet Skin cancer Basal Cell carcinoma Least malignant and most common Cells of stratum basale can t form keratin Invade dermis and subcutaneous tissue Skin cancer Squamous Cell Carcinoma In the stratum spinosum Caused by sun exposure Skin cancer Malignant Melanoma Cancer of melanocytes (make melanin) 5% of cases Watch for ABCD- Asymmetry of moles, Border irregularity, Color changes, Diameter increasing 5
Developmental Aspects Fetus is covered in lanugo (hair) Vernix caseosa covers newborn skin to protect it More oil is produced in adolescence As we age, less subcutaneous tissue is made, less oil, less hair, and hair becomes gray Alopecia- baldness, triggered by age or genes Keep your skin healthy! Good nutrition, and fluids Practice good hygiene Stay out of the sun or use sunscreen Avoid alcohol, cigarettes, or drugs 6