The Integumentary System Integument is skin Skin and its appendages make up the integumentary system Two distinct layers Epidermis Dermis

The Integumentary System Epidermis - outer layer Dermis – inner layer Sweat glands: excrete sweat through pores Sweat is made up of urea, salts, and water Largest organ of the body. It’s the body’s first line of defense

The “Birthday Suit” Combination of 4 main tissues: Epithelial – outer layer Connective – underlies dermis Smooth Muscle – goose bumps Nervous – sensory receptors

Functions of the Skin Protection Acts as cushion, insulator, waterproofing Protects from chemicals, heat, cold, bacteria Screens UV Temperature regulation and sensory receptor (nerve endings) Storage of chemical compounds Excretion and secretion Synthesis and storage of nutrients

The Skin FG04_02.JPG Title: Components of the Integumentary System Notes: Relationships among the major components of the integumentary system (with the exception of nails, shown in Figure 4-15). Keywords: integumentary system, cutaneous, epidermis, dermis, papillary layer, reticular layer, hair follicles, exocrine glands, nails

Epidermis Outer layer of dead skin cells called cuticle Layer you see everyday “Ashiness” is caused by this layer of dead skin cells being very rough DUST you see around is made up of dead skin cells! Under the cuticle is another layer of living epithelial cells that make up the rest of the epidermis.

Epidermis Four types of cells Layers (from deep to superficial) Keratinocytes – deepest, produce keratin (tough fibrous protein) Melanocytes - make dark skin pigment melanin Merkel cells – associated with sensory nerve endings Langerhans cells – macrophage-like dendritic cells Layers (from deep to superficial) Stratum basale or germinativum – single row of cells attached to dermis; youngest cells Stratum spinosum – spinyness is artifactual; tonofilaments (bundles of protein) resist tension Stratum granulosum – layers of flattened keratinocytes producing keratin (hair and nails made of it also) Stratum lucidum (only on palms and soles) Stratum corneum – horny layer (cells dead, many layers thick)

Epithelium: layers (on left) and cell types (on right)

Remember… Four basic types of tissue Epithelium – epidermis just discussed Connective tissue - dermis Muscle tissue Nervous tissue

Epidermis and Dermis Epidermis is avascular (no blood vessels) Dermis is highly vascular (has blood vessels) Epidermis receives nourishment from dermis Cells far away from nourishment die

Epidermis FG04_03.JPG Title: The Structure of the Epidermis Notes: A light micrograph through a portion of the epidermis, shows the major stratified layers of epidermal cells. Keywords: epidermis, structure, layers, stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum germinativum, dermis

Dermis Thick layer under the epidermis Strong, flexible connective tissue: your “hide” Rich supply of nerves and vessels Critical role in temperature regulation

Deeper Layer of the Dermis Contains Blood vessels Glands Deep pressure receptors Attached to underlying organs by the subcutaneous layer Packed with adipose cells Stabilizes position of skin

Dermal Components Communication with other organ systems Cardiovascular Lymphatic Nervous Sensation Control of blood flow and secretion

Epidermis and dermis of (a) thick skin and (b) thin skin (which one makes the difference?)

Fingerprints Human Anatomy, 3rd edition Prentice Hall, © 2001

Fingerprints, palmprints, footprints Dermal layer lie atop dermal ridges Elevate the overlying epidermis into epidermal ridges “Prints” are actually “sweat films” because of sweat pores Genetically determined Flexion creases Deep dermis, from continual folding Fibers Collagen: strength and resilience Elastic fibers: stretch-recoil Striae: stretch marks Tension lines (or lines of cleavage) The direction the bundles of fibers are directed The dermis is the receptive site for the pigment of tattoos

Skin Color Three skin pigments Melanin: the most important Carotene: from carrots and yellow vegies Hemoglobin: the pink of light skin Melanin in granules passes from melanocytes (same number in all races) to keratinocytes in stratum basale Digested by lysosomes Variations in color

Skin Appendages Derived from epidermis but extend into dermis Include Hair and hair follicles Sebaceous (oil) glands Sweat (sudoiferous) glands Nails

What Else Comes from the Epidermis? Nails Hair Glands

Nails Made of hard keratin Corresponds to hooves and claws Grows from nail matrix

Nail Structure Nail body Free edge Nail root Matrix Lunula (moon)

Nail Structure FG04_15.JPG Title: Structure of a Nail Notes: These drawings illustrate the prominent features of a typical fingernail as view from the surface and in section. Keywords: fingernail, hyponychium, nail bed, lateral nail groove, lunula, eponychium, phalanx, dermis, epidermis

Functions of Hair Protection Thermoregulation scalp Thermoregulation less in humans than other mammals Sensory sense light touch of the skin Minor role in humans

Hair growth: averages 2 mm/week Hair loss Hair color Types of hair Vellus: fine, short hairs Intermediate hairs Terminal: longer, courser hair Hair growth: averages 2 mm/week Active: growing Resting phase, then shed Hair loss Thinning – age related Male pattern baldness Hair color Amount of melanin for black or brown; distinct form of melanin for red White: decreased melanin and air bubbles in the medulla Genetically determined though influenced by hormones and environment

Hair Structure Shaft Superficial portion Root Below the surface Cuticle Outermost layer of hair Hair develops in follicles Downward continuation of epidermis

Hair Structure FG04_10A.JPG Title: Hair Follicles Notes: Hairs originate in complex organs termed follicles. (a) A longitudinal section and a cross section through a hair follicle. (b) and (c) A section along the longitudinal axis of a hair follicle. Keywords: hair follicle, longitudinal section, cross section, sebaceous gland, arrectory pili muscle, cortex, cuticle, internal root sheath, connective tissue layer, glassy membrane, external root shaft

Growth of Hair Contains melanocytes Hair papilla Bulb At the base of the follicle Contains blood vessels and nerves Nourishes hair Bulb Contains matrix – epithelial cells responsible for growth Contains melanocytes

Arrector Pili Smooth muscle attaches to follicle Raises hairs Response to fright or cold Function?

*“arrector pili” is smooth muscle * Hair and hair follicles: complex Derived from epidermis and dermis Everywhere but palms, soles, nipples, parts of genitalia *“arrector pili” is smooth muscle * Hair bulb: epithelial cells surrounding papilla Hair papilla is connective tissue________________

Glands Sebaceous glands Connected to hair follicles Secrete a waxy, oily substance (sebum) Blackheads Secretion increases at puberty

Sebaceous (oil) glands Entire body except palms and soles Oils and lubricates

Other Glands Sweat Glands Found just about everywhere Produce “perspiration” Water, salt, metabolic wastes Function – cooling of the body Scent Glands Specific type of sweat gland Found near hair follicles Axillary & genital regions Develop at puberty

Sweat Glands Prevent overheating 500 cc to 12 l/day! (is mostly water) Humans most efficient (only mammals have) Produced in response to stress as well as heat

Types of Sweat Glands Eccrine or merocrine Apocrine Most numerous True sweat: 99% water, some salts, traces of waste Open through pores Apocrine Axillary, anal and genital areas only Ducts open into hair follicles The organic molecules in it decompose with time - odor Modified apocrine glands Ceruminous – secrete earwax Mammary – secrete milk

The skin also helps control body temperature- Homeostasis When you sweat, heat leaves the body through your pores. When the sweat hits the outer surface of the skin, it is cooled by the air. This lowers your body temperature.

The Skin with Sweat Glands FG04_02.JPG Title: Components of the Integumentary System Notes: Relationships among the major components of the integumentary system (with the exception of nails, shown in Figure 4-15). Keywords: integumentary system, cutaneous, epidermis, dermis, papillary layer, reticular layer, hair follicles, exocrine glands, nails

Diseases and Disorders of the Integumentary System

Skin Injury and Repair Bleeding occurs at the site of injury immediately after the injury, and mast cells in the region trigger an inflammatory response. Epidermis Dermis After several hours, a scab has formed and cells of the stratum germinativum are migrating along the edges of the wound. Phagocytic cells are removing debris, and more of these cells are arriving with the enhanced circulation in the area. Clotting around the edges of the affected area partially isolates the region. Sweat gland Scab Macrophages and fibroblasts Migratory epithelial cells Granulation tissue

Skin Injury and Repair One week after the injury, the scab has been undermined by epidermal cells migrating over the meshwork produced by fibroblast activity. Phagocytic activity around the site has almost ended, and the fibrin clot is disintegrating. Fibroblasts After several weeks, the scab has been shed, and the epidermis is complete. A shallow depression marks the injury site, but fibroblasts in the dermis continue to create scar tissue that will gradually elevate the overlying epidermis. Scar tissue

Aging of the Skin Major Age-Related Changes Injury and infection increase Immune cells decrease Sun protection diminishes Skin becomes dry, scaly Hair thins, grays Sagging, wrinkles occur Heat loss decreases Repair slows

Effects of UV Radiation Beneficial effect - activates synthesis of vitamin D3 Harmful effects Sun burn Wrinkles, premature aging Malignant melanoma Basal cell carcinoma

Types and Growth of Hair Vellus hairs Body hairs of women and children Terminal hairs Hair of scalp Axillary and pubic area (at puberty) Hair thinning and baldness Due to aging Male pattern baldness

Burns Threat to life Catastrophic loss of body fluids Dehydration and fatal circulatory shock Infection

Burns Classified by severity Infections Skin cancer First-degree burn – only upper epidermis is damaged - redness (e.g. sunburn) Second-degree burn – upper part of dermis is also damaged Blisters appear Skin heals with little scarring Third-degree burn Consume thickness of skin Burned area appears white, red, or blackened Can lead to Infections Skin cancer

Skin Injury and Repair Table 5-1

First-degree Second-degree Third-degree (epidermis only; redness) (epidermis and dermis, with blistering) Third-degree (full thickness, destroying epidermis, dermis, often part of hypodermis)

Critical burns Over 10% of the body has third-degree burns 25 % of the body has second-degree burns Third-degree burns on face, hands, or feet

Skin Cancer Basal cell carcinoma Squamous cell carcinoma Melanoma Least malignant and most common Squamous cell carcinoma Arises from keratinocytes of stratum spinosum Melanoma A cancer of melanocytes The most dangerous type of skin cancer

Tumors of the skin Benign, e.g. warts Cancer – associated with UV exposure (also skin aging) Aktinic keratosis - premalignant Basal cell - cells of stratum basale Squamous cell - keratinocytes Melanoma – melanocytes: most dangerous; recognition: A - Asymmetry B - Border irregularity C - Colors D - Diameter larger than 6 mm

Skin Cancer Squamous cell carcinoma Basal cell carcinoma Melanoma Figure 5.12

Use the following vocabulary to label the diagram: hair shaft, oil (sebaceous)gland, fat cells, erector pili muscle, blood vessels, nerve endings, epidermis, dermis, cuticle, epithelial cells, hair follicle, sweat gland, connective tissue