The Integumentary System Chapter 6 The Integumentary System

Introduction Skin Accessory structures Large waterproof covering UV light and chemical protection Accessory structures Hair, nails, glands

The Layers of the Skin

Introduction Epidermis: upper layer Dermis: lower layer Epithelial tissue divided into sublayers Dermis: lower layer Dense connective tissue Connects skin to fat and muscle Below dermis is subcutaneous layer called hypodermis

Introduction (cont’d.)

The Epidermis Stratified, squamous, keratinized, epithelium Keratinization Cells move to surface, lose water, and nuclei change Composed of five layers

The Epidermis (cont’d.) Stratum corneum Outermost layer Dead, keratinized cells Barrier to light, heat, chemicals, microorganisms

The Epidermis (cont’d.) Stratum lucidum One to two cell layers thick Flat and transparent Difficult to see

The Epidermis (cont’d.) Stratum granulosum Two or three layers Flattened cells Active keratinization Lose nuclei Compact and brittle

The Epidermis (cont’d.) Stratum spinosum Several layers of spiny-shaped cells Desmosomes prevalent Desmosomes: interlocking cellular bridges

The Epidermis (cont’d.) Stratum germinativum Rests on basement membrane Lowermost layer called stratum basale New cells produced here (mitosis) Melanocytes: produce melanin Skin color Albinism

The Dermis Also called corium Structures found in dermis Blood and lymph vessels Nerves Muscles Glands Hair follicles

The Dermis (cont’d.) Divisions Papillary Reticular Adjacent to the epidermis Reticular Between papillary and subcutaneous Subcutaneous (hypodermis) Layers of fat below the dermis

The Accessory Structures of the Skin

Hair Covers most of the surface of the body Three parts: cuticle, cortex, medulla Shaft: visible portion Root: hair follicle Arrector pili: smooth muscle

Hair

Hair (cont’d.) Growth Texture: straight, curly, or tightly curly Hair follicle Cycles of growth and rest Texture: straight, curly, or tightly curly Color: based on complex genetic factors

Nails Modified epidermal cells Lunula: white crescent Body: visible portion Root: covered by skin Growth occurs from the nailbed

Nails (cont’d.)

Sebaceous Glands Produce sebum (oil) Lubricates skin and hair Secretion controlled by endocrine system Increases at puberty Decreases in later life

Sweat Glands Most numerous in palms and soles Not found on margins of the lips or head of the penis Each gland has secretory portion and excretory duct Sweating helps cool the body

Functions of the Integumentary System

Sensation Temperature receptors Pressure receptors Hot and cold Pressure receptors Excessive pressure as pain Mild pressure as pleasurable Combinations produce burning, itching, tickling

Protection Prevents passage of harmful physical and chemical agents Melanin protects from UV rays Lipid content inhibits water loss Acid mantle: kills most bacteria Nails protect ends of our digits Hair acts as insulation and filter

Thermoregulation Normal body temperature: 98.6 degrees F When external temperatures increase Blood vessels dilate Sweat occurs When external temperatures decrease Blood vessels first dilate then constrict

Secretion Sebum Sweat Vitamin D Cosmetic gloss Moisturizer Antifungal/antibacterial properties Sweat Essential in cooling process Vitamin D

Summary Discussed the layers of the epidermis and the process of keratinization Described the structure of the dermis Discussed the accessory structures of the skin including the hair and nails Discussed the different functions of the integumentary system