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Chapter 5Integumentary SystemDermisAndAccessory StructuresEpidermisMajority of cells are keratinocytesAshiness is caused by this layer of dead skin cells being very rough and raggedy.DUST you see around is made up of dead skin cells!

2Review: Epidermis

* Lucidum only found in often used areas. * Basale has cells that are continuously dividing3FG04_02.JPGTitle: Components of the Integumentary SystemNotes: 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 vs. DermisEpidermis is avascular (no blood vessels)Epithelial tissueDermis is highly vascular (has blood vessels)Connective tissueDermisThick layer under the epidermis

Strong, flexible connective tissue

Fiber typesCollagen ElasticReticular

DermisRich supply of nerves and vessels

Critical role in Temperature Regulation

DermisTwo layers Papillary areolar connective tissue; includes dermal papillae Reticular reticulum (network) of collagen and reticular fibers

Accessory StructuresDerived from epidermis but extend into dermisIncludeHair and hair folliclesSebaceous (oil) glandsSweat (sudoiferous) glandsNails

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NailsOf hard keratinCorresponds to hooves and clawsGrows from nail matrix

Nail StructureNail bodyFree edgeNail root MatrixLunula (moon)

Hair

Derived from epidermisMade of hard keratinEverywhere but palms, soles, nipples, parts of genitalia Hair develops in follicles

Hair StructurePartsRoot imbedded in skinShaft projecting above skin surfaceHair bulb where hair is produced Hair follicle wall is extension of epidermis

Figure 5.5 in book page 104

Dermal Papilla

CuticleCortexMedullaHair BulbSebaceous GlandArrector Pili Muscle

Hair ShaftHair RootHair Follicle Wall

Three layersMedullacoreCortexsurrounds medullaCuticlesingle layers, overlappingHair Structure

17FG04_10A.JPGTitle: Hair FolliclesNotes: 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

Figure 5.5 in bookpage 104

Dermal PapillaCuticleCortexMedullaHair BulbSebaceous GlandArrector Pili MuscleHair ShaftHair RootHair Follicle WallArrector PiliSmooth muscle attaches to follicleRaises hairsResponse to fright or coldFunction?

19Thermoregulation less in man than other mammalsSense light touch of the skinProtection scalpThree concentric layersMedulla (core)Cortex (surrounds medulla)Cuticle (single layers, overlapping)

Functions of hairHair growth: averages 2 mm/weekActive stage: hair is growingResting phase: no hair growth, then shed

At the base of the follicle, hair papillaContains blood vessels and nervesNourishes hair

BulbContains matrix epithelial cells responsible for growthContains melanocytesHair lossThinning age relatedMale pattern baldness

Hair colorAmount of melanin for black or brown; distinct form of melanin for redWhite: decreased melanin and air bubbles in the medullaGenetically determined though influenced by hormones and environmentSebaceous (oil) glandsEntire body except palms and solesConnect to hair follicle

Sebaceous (oil) glandsProduce sebum oily waxy substanceOils and lubricatesCan cause blackheads, lead to acne if follicle ruptures from buildup.

Sebaceous Glands

25FG04_13A.JPGTitle: Sebaceous Glands and FolliclesNotes: The structure of sebaceous glands and sebaceous follicles in the skin.Keywords: sebaceous glands, sebaceous follicles, structure, sebum, germinative cells

Sweat glandsAll over bodyFunction: Prevent overheating

500 cc to 12 l/day! (is mostly water)

Produced in response to stress as well as heat

2 Types of sweat glandsMerocrineMost numerousTrue sweat: 99% water, some salts, traces of wasteOpen through poresApocrineAxillary, anal and genital areas onlyDucts open into hair follicesThe organic molecules in it decompose with time - odorThe 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.

28The Skin with Sweat Glands

29FG04_02.JPGTitle: Components of the Integumentary SystemNotes: 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

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

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HypodermisThe dermis is attached to underlying organs by the hypodermis (subcutaneous layer)Loose connective tissuePacked with adipose cellsStabilizes position of skin

HypodermisHypodermis (Gk) = below the skinSubcutaneous (Latin) = below the skinAlso called superficial fasciafascia (Latin) =band; in anatomy: sheet of connective tissueFatty tissue which stores fat and anchors skin (areolar tissue and adipose cells)Different patterns of accumulation (male/female)