Human Anatomy and Physiology I The Integumentary System Chapter 5 BSC 2085

Chapter 5 Outline Overview of the skin Skin Cancers Burns Epidermis Hypodermis Appendages of the skin Sweat glands, Sebaceous glands, Hair, Nails Functions Skin Cancers Burns

Skin (Integument) Consists of three major regions Epidermis—superficial region Dermis—middle region Hypodermis—deepest region

Hair shaft Dermal papillae Epidermis Subpapillary vascular plexus Papillary layer Pore Appendages of skin Dermis Reticular layer • Eccrine sweat gland • Arrector pili muscle Hypodermis (superficial fascia) • Sebaceous (oil) gland • Hair follicle Nervous structures • Hair root • Sensory nerve fiber Cutaneous vascular plexus • Pacinian corpuscle • Hair follicle receptor (root hair plexus) Adipose tissue

Epidermis Keratinized stratified squamous epithelium Cells of Epidermis

Dermis - supplied with blood vessels, nerve fibers, lymphatic vessels Connective tissue - binds epidermis to tissue below - supplied with blood vessels, nerve fibers, lymphatic vessels Layers 1. Papillary layer 2. Reticular layer

Skin Color Three pigments contribute to skin color Melanin Carotene Yellow to reddish-brown to black, responsible for dark skin colors Carotene Yellow to orange, most obvious in the palms and soles Hemoglobin Responsible for the pinkish hue of skin

Appendages of the Skin Derivatives of the epidermis Sweat glands Oil glands Hairs and hair follicles Nails

Sweat Glands Eccrine: forehead, neck, back, palms, soles - respond to increased body temperature, or stress 2. Apocrine: axillary regions, groin, around nipples - respond to sexual arousal, fear, pain, emotional upset 3. Ceruminous: produce cerumen (earwax) - protection Secretory cells Dermal connective tissue Duct Sebaceous gland Sweat pore Eccrine

Sebaceous (Oil) Glands Function produce sebum - waterproofs and softens skin and hair Sebaceous gland duct Hair in hair follicle Secretory cells Dermal connective tissue gland Sweat pore Eccrine

Which of the following is not part of the dermis? Papillary layer Melanocytes Sebaceous glands Hair follicles

Hair Function Distribution Alerts the body to presence of insects on the skin Guards the scalp against physical trauma, heat loss, and sunlight Distribution Entire surface except palms, soles, lips, nipples, and portions of external genitalia

Hair Structure Hair develops from epidermal cells at base of follicle Older cells are pushed outward; become keratinized Hair pigments: melanins (yellow, rust brown, black) Gray/white hair: decreased melanin production, increased air bubbles in shaft

Follicle wall • Connective tissue root sheath Hair shaft • Glassy membrane • External epithelial root sheath • Internal epithelial root sheath Arrector pili Hair root • Cuticle Sebaceous gland • Cortex • Medulla Hair root Hair matrix Hair bulb Hair papilla Subcutaneous adipose tissue

Hair Thinning and Baldness Alopecia Hair thinning in both sexes after age 40 True baldness Genetically determined and sex-influenced condition Male pattern baldness is caused by follicular response to DHT

Nails Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes Keratinized epidermal cells Protective

Functions of the Integumentary System Protection Chemical barriers Skin secretions fight bacteria Melanin protects against UV rays Physical/mechanical barriers Keratin and glycolipids block most water and water- soluble substances Limited penetration of skin by lipid-soluble substances Biological barriers Dendritic cells and macrophages

Functions of the Integumentary System Body temperature regulation Sweat for evaporative cooling Constriction of dermal capillaries to prevent heat loss Cutaneous sensations Pain Pressure Temperature

Functions of the Integumentary System Metabolic functions Synthesis of vitamin D Blood reservoir — Up to 5% of body’s blood volume Excretion — Salt and nitrogenous wastes in sweat

Did You Know? Every minute 30,000 - 40,000 dead skin cells fall off or are sloughed off your body. In one month, your body will have a whole new layer of skin. You will shed about 40 pounds of skin during your lifetime. http://www.drstandley.com/bodysystems_integumentary.shtml

Skin Cancer Three major types Basal cell carcinoma Least malignant, most common Squamous cell carcinoma Second most common Melanoma Most dangerous

Basal Cell Carcinoma Stratum basale cells proliferate and slowly invade dermis and hypodermis Cured by surgical excision in 99% of cases

Squamous Cell Carcinoma Involves keratinocytes of stratum spinosum Most common on scalp, ears, lower lip, and hands Good prognosis if treated by radiation therapy or removed surgically

Melanoma Characteristics (ABCDE rule) A: Asymmetry; the two sides of the pigmented area do not match 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) E: Evolving is any change in elevation, itching, scabbing, or bleeding

Melanoma Involves melanocytes Highly metastatic and resistant to chemotherapy Treated by wide surgical excision accompanied by immunotherapy

Burns Causes Heat, electricity, radiation, certain chemicals Results Tissue damage, denatured protein, cell death Immediate threat Dehydration and electrolyte imbalance, leading to renal shutdown and circulatory shock

Burns First degree Second degree Epidermal damage only Localized redness, edema (swelling), and pain Second degree Epidermal and upper dermal damage Blisters appear 1st degree burn 2nd degree

Burns Third degree Entire thickness of skin damaged Gray-white, cherry red, or black No initial edema or pain (nerve endings destroyed) Skin grafting usually necessary 3rd degree burn

Homeostatic Imbalances Vitiligo Most prevalent skin pigmentation disorder Loss of melanocytes Uneven skin pigmentation Autoimmune disorder

Homeostatic Imbalances Eczema inflammation of the epidermis redness, edema, itching and dryness, crusting, flaking, blistering, cracking, oozing, or bleeding

Tissue Repair 1. Hemostasis and Inflammation hemostasis = blood clotting blood platelets adhere to the wound and recruit more platelets to form a clot. fibrin strengthens the clot Inflammation is triggered by mast cells Capillaries dilate to allow white blood cells through, causing pink appearance and increased temperature.

Tissue Repair 2. Proliferation macrophages consume debris and bacteria, and signal other cell types to come and start the next phase Granulation tissue replaces the blood clot Fibroblasts produce collagen to strengthen and hold the wound together Epidermis begins to regenerate

Tissue Repair 3. Remodeling/ Maturation Repairs are strengthened by more organized collagen Wound continues to contract Collagen-rich scar tissue has replaced wound Scab detaches