The Integumentary System 5 The Integumentary System

Functions of the Integument 1. protects us from bacterial invasion 2. protects us from dessication 3. protects us from heat loss 4. protects us from UV radiation

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

Reticular layer of dermis Hair shaft Pore Dermal papillae (papillary layer of dermis) Epidermis Meissner's corpuscle Free nerve ending Reticular layer of dermis Sebaceous (oil) gland Dermis Arrector pili muscle Sensory nerve fiber Eccrine sweat gland Pacinian corpuscle Hypodermis (superficial fascia) Artery Vein Hair root Adipose tissue Hair follicle Eccrine sweat gland Hair follicle receptor (root hair plexus) Figure 5.1

Epidermis 4 major types of cells in the epidermis: Keratinocytes – produce keratin which protects the skin Melanocytes – protects the cell nuclei from UV radiation – gives us skin color Langerhans cells – ingest foreign substances Merkel cells – sensory receptor for touch Let Me Keep Money

Layers of the Epidermis Figure 5.2b

Layers of the Epidermis Stratum Basale – deepest layer next to dermis a. continual mitosis b. produces new keratinocytes and melanocytes

Layers of the Epidermis Stratum Spinosum Have filaments that function to resist tension and attach to the desmosomes Have Langerhans cells and melanin granules and spiky kerantinocytes

Layers of the Epidermis Stratum Granulosum Keratinocytes change to flattened shape Organelles disintegrate Granules which form keratin Granules which form a glycolipid waterproofing contained in extracellular space to slow water loss from epidermis No capillarity above this layer

Layers of the Epidermis Stratum Lucidum Clear flat dead keratinocytes Visible only in thick skin area of the body Not present in thin skin areas of the body

Layers of the Epidermis Stratum Corneum Outermost layer Protect against penetration and abrasion Consists of dead cells (dead skin and dandruff) Buy Some Good (lemon) Cookies

Dermis Contains fibroblasts (produces fibers); macrophages (destroy bacteria and worn cells); mast cells (detect foreign substances and initiate the inflammatory response); white blood cells (take part of the immune response) Supplied with nerve, blood, and lymphatic vessels Contain hair follicle, oil and sweat glands

Second major skin region containing strong, flexible connective tissue Dermis Second major skin region containing strong, flexible connective tissue Composed of two layers – papillary reticular

Layers of the Dermis: Papillary Layer Touch receptors Fingerprints Gripping of hands and feet Contain Meissner’s corpuscles (touch) Contain Pacinian corpuscles (pain)

Layers of the Dermis: Reticular Layer 80% of the thickness of the skin Collagen fibers in this layer add strength and resiliency to the skin Elastin fibers provide stretch-recoil properties Nourished by cutaneous plexus

Subcutaneous layer deep to the skin Hypodermis Subcutaneous layer deep to the skin Composed of adipose and areolar connective tissue

Three pigments contribute to skin color Melanin – yellow to reddish-brown to black pigment, responsible for dark skin colors Freckles and pigmented moles – result from local accumulations of melanin Carotene – yellow to orange pigment, most obvious in the palms and soles of the feet Hemoglobin – reddish pigment responsible for the pinkish hue of the skin

Sweat Glands (sudoriferous glands) prevent overheating of the body secrete cerumen and milk Eccrine – found in palms, soles of the feet, and forehead Apocrine – found in axillary and anogenital areas Ceruminous glands – modified apocrine glands in external ear canal that secrete cerumen Mammary glands – specialized sweat glands that secrete milk

Soften skin when stimulated by hormones Sebaceous Glands Soften skin when stimulated by hormones Secrete an oily secretion called sebum Whitehead, blackhead, seborrhea

dead keratinized cells produced by hair follicles Hair (Pili) dead keratinized cells produced by hair follicles Regions are shaft and root Contains hard keratin Consists of a core called the medulla, a cortex, and an outermost cuticle Pigmented by melanocytes at the base of the hair

Shaft of Hair (Go to Microscope) If shaft is flat and ribbon like (kinky) If shaft is oval (silky and wavy) If shaft is round (straight) Locate medulla, cortex, cuticle Look at the slides with beard hair (note the shape of the tip ends) Pull a hair out by the root (observe the root tip)

Hair Function and Distribution Functions of hair include: Helping to maintain warmth Alerting the body to presence of insects on the skin Guarding the scalp against physical trauma, heat loss, and sunlight

Hair Follicle Figure 5.5c

Vellus – pale, fine body hair found in children and the adult female Types of Hair Vellus – pale, fine body hair found in children and the adult female Terminal – coarse, long hair of eyebrows, scalp, axillary, and pubic regions

Structure of a Nail Scalelike modification of the epidermis on the distal, dorsal surface of fingers and toes Figure 5.6

Protection- Physical Barriers Prevents bacterial invasion Provides waterproofing with glycolipids Does allow penetration of: O, CO2, Vitamins A,D,E,K and steroids Oleoresins (poison oak/ivy) Organic solvents (paint thinner, acetone) Salts and heavy metals (Pb,Hg) Drug agents

Protection - Biological Langerhans cells – detect foreign substances Macrophages – viruses and bacteria DNA-conversion of radiation to heat

Body Temperature Regulation Constant secretion of sweat Dilation of blood vessels and increased sweat production during excessive heat Evaporation Constriction of blood vessels and heat loss is slowed

Makes chemicals to aid liver function Metabolic Functions Synthesis of vitamin D in dermal blood vessels – aids in Ca absorption from digestive system Makes chemicals to aid liver function Makes enzymes that deter wrinkles

Blood reservoir – 5% of blood volume Functions of Skin Blood reservoir – 5% of blood volume Excretion – sweat (amonia, urea, uric acid)

Skin Cancer Most skin tumors are benign and do not metastasize A crucial risk factor for nonmelanoma skin cancers is the disabling of the p53 gene Newly developed skin lotions can fix damaged DNA

3. Melanoma – cancer of melanocyts-most dangerous Skin Cancer – 3 types 1. Basal cell carcinoma – least malignant and most common-stratum basale 2.Squamous cell carcinoma -stratum spinosum-most head,hands,can metastasize 3. Melanoma – cancer of melanocyts-most dangerous

Skin Cancers Figure 5.7a–c

A: Asymmetry; the two sides of the pigmented area do not match Melanoma – ABCD rule A: Asymmetry; the two sides of the pigmented area do not match B: Border is irregular and exhibits indentations C: Color (pigmented area) is black, brown, tan, and sometimes red or blue D: Diameter is larger than 6 mm (size of a pencil eraser)

Burns considered critical if: Rule of Nines - Burns Burns considered critical if: Over 25% of the body has second-degree burns Over 10% of the body has third-degree burns There are third-degree burns on face, hands, or feet Volume of fluid lost extimated by percentage of body surface burned 11 body areas – each 9%

Rule of Nines Figure 5.8a

Developmental Aspects of the Integument: Fetal Epidermis develops from ectoderm Dermis and hypodermis develop from mesoderm Lanugo – downy coat of delicate hairs covering the fetus Vernix caseosa – substance produced by sebaceous glands that protects the skin of the fetus in the amnion