Anatomy & Physiology Lecture Notes - Integument System PDF

Anatomy & Physiology August 20, 2024 (Lecture) (Week 3) Integument System Layer of Epidermis Stratum b...

Anatomy & Physiology August 20, 2024 (Lecture) (Week 3) Integument System Layer of Epidermis Stratum basale-Bottom o Cells undergoing mitosis o Lies next to dermis Stratum spinosum Stratum granulosum Stratum lucidum o Occurs only in thick skin Stratum corneum-Top o Shingle-like dead cells Keyword: CuLuGo Sa Batok Skin (Integument) Consists of three major regions: 1. Epidermis – superficial region 2. Dermis – middle region 3. Hypodermis (superficial fascia) – deepest region Subcutaneous layer deep to skin (not technically part of skin) Mostly adipose tissue Dermis Strong, flexible connective tissue Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells Two layers: - Papillary - Reticular  Layers of the Dermis: Skin Color “Papillary Layer” Three pigments contribute to skin color: Papillary layer 1. Melanin - Areolar connective tissue Yellow to reddish-brown to with collagen and elastic black, responsible for dark fibers and blood vessels skin colors - Dermal papillae contain: Produced in melanocytes o Capillary loops Freckles and pigmented o Meissner’s corpuscles moles o Free nerve endings >>Local accumulations of -------------------------------------- melanin Notes: 2. Carotene Pacinian – high frequency vibration Yellow to orange, most Meissner’s – low frequency obvious in the palms and vibration soles Free nerve endings – detects pain 3. Hemoglobin and temperature changes Responsible for the pinkish -------------------------------------- hue of skin Layers of the Dermis: “Reticular Layer” Appendages of the Skin Reticular Layer Derivatives of the epidermis: ~80% of the thickness of - Sweat glands dermis - Oil glands Collagen fibers – strength - Hairs and hair follicles and resiliency - Nails Elastic fibers – provide stretch – recoil properties Sweat glands Two main types of sweat glands: Skin Markings: Friction Ridges 1. Eccrine (merocrine) sweat glands- abundant on palms, soles, and Epidermal ridges lie atop deeper forehead dermal papillary ridges to form Sweat: 99% water, NaCl, friction ridges of fingerprints vitamin C, antibodies, dermcidin, metabolic wastes Function in thermoregulation  2. Apocrine sweat glands – confined - Mate attraction to axillary and anogenital areas Distribution Sebum: sweat + fatty - Entire surface except palms, substances and proteins soles, lips, nipples, and portions of Ducts connect to hair external genitalia follicles Consists of dead keratinized cells Functional from puberty Contains hard keratin, more onward (as sexual scent durable than soft keratin of skin glands) Hair pigments: melanins (yellow, - Specialized apocrine glands rust brown, black) Ceruminous glands – in external ear - Gray/white hair: decreased canal; secrete cerumen melanin production, increased air Mammary glands bubbles in shaft Sebaceous (Oil) Glands Widely distributed Most develop from hair follicles Become active at puberty Sebum - Oily holocrine secretion - Bactericidal - Softens hair and skin Hair Follicle Extends from the epidermal surface into dermis Two-layered wall: outer connective tissue root sheath, inner epithelial root sheath Hair bulb: expanded deep end Hair follicle receptor (root hair plexus) - Sensory nerve endings around Hair each hair bulb o Stimulated by bending a hair Functions Arrector pili - Alerting the body to presence of - Smooth muscle attached to insects on the skin follicle - Guarding the scalp against - Responsible for “goose bumps” physical trauma, heat loss, and - Vestigial sunlight  Hair Thinning and Baldness Alopecia – hair thinning in both sexes after age 40 True (frank) baldness - Genetically determined and sex- influenced condition - Male pattern baldness is caused by follicular response to DHT Structure of a Nail Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes Functions of the Integumentary System 1. Protection-Three types of barriers - Chemical - Physical/mechanical barriers o Keratin and glycolipids block most water and water- soluble substances o Limited penetration of skin by lipid-soluble substance, plant oleoresin (e.g., poison  ivy), organic solvents, salts Three major types: of heavy metals, some drugs 1. Basal cell carcinoma - Biological barriers o Least malignant, most Dendritic cells, macrophages, and common DNA 2. Squamous cell carcinoma o Second most common 2. Body temperature regulation 3. Melanoma - ~500 ml/day of routine insensible o Most dangerous perspiration (at normal body temperature) Basal Cell Carcinoma - At elevated temperature, dilation of dermal vessels and increased Stratum basale cells proliferate sweat gland activity (sensible and slowly invade dermis and perspirations) cool the body hypodermis Cured by surgical excision in 99% of 3. Cutaneous sensations cases - Temperature, touch, and pain 4. Metabolic functions - Synthesis of Vitamin D precursor and collagenase - Chemical conversion of carcinogens and some hormones 5. Blood reservoir-up to 5% of body’s blood volume Squamous Cell Carcinoma 6. Excretion-nitrogenous wastes and salt in sweat Involves keratinocytes of stratum spinosum Skin Cancer Most common on scalp, ears, lower lip, and hands. Most skin tumors are benign (do Good prognosis if treated by not metastasize) radiation therapy or removed Risk factors surgically - Overexposure to UV radiation - Frequent irritation of the skin Some skin lotion contains enzymes in liposomes that can fix damaged DNA  Melanoma Partial-Thickness Burns Involves melanocytes First degree Highly metastatic and resistant to - Epidermal damage only chemotherapy o Localized redness, edema Treated by wide surgical excision (swelling), and pain accompanied by immunotherapy Second degree Characteristics (ABCD rule) - Epidermal and upper dermal A: Asymmetry; the two sides of damage the pigmented area do not much o Blisters appear B: Border exhibits indentations C: Color is black, brown, tan, and sometimes red or blue D: Diameter is larger than 6 mm (size of a pencil eraser) Full-Thickness Burns Burns Third degree - Entire thickness of skin damaged Heat, electricity, radiation, certain o Gray-white, cherry red, or chemicals black o No initial edema or pain (nerve endings destroyed) Burn o Skin grafting usually (tissue damage, denatured protein, cell necessary death) Immediate threat: - Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock  Severity of Burns Critical if: -> 25% of the body has second- degree burns ->10% of the body has third-degree burns ->Face, hands, or feet bear third- degree burns Skin Homeostatic Imbalances Infections o Athletes foot - Caused by fungal infection o Boils and carbuncles - Caused by bacterial infection o Cold sores - Caused by virus (HSV) Infections and allergies o Contact dermatitis - Exposures cause allergic reaction o Impetigo - Caused by bacterial infection (staph) o Psoriasis - Cause is unknown (genetic) - Triggered by trauma, infection, stress