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Integumentary System

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Integumentary System Chapter 5 Overview Composed of skin and it s derivatives (sweat & oil glands, hairs and nails) Primary function is protection The Skin I Two ... – PowerPoint PPT presentation

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Title: Integumentary System


1
Integumentary System
  • Chapter 5

2
Overview
  • Composed of skin and its derivatives (sweat
    oil glands, hairs and nails)
  • Primary function is protection

3
The Skin I
  • Two distinct regions
  • Epidermis
  • - outermost protective shield
  • - composed of epithelial cells
  • - avascularized, obtains nutrients by diffusing
    through tissue fluid from blood vessels in the
    dermis
  • Dermis
  • - makes up bulk of skin
  • - tough, leathery layer fibrous connective
    tissue
  • - vascularized

4
The Skin II
  • The dermis and epidermis rest on subcutaneous
    hypodermis, (superficial fascia)
  • Not technically part of skin, but shares many of
    its functions
  • Mostly adipose tissue w/ some areolar connective
  • Stores fat
  • Anchors skin to underlying structures (usually
    muscle), but allows free sliding
  • Shock absorber and insulator

5
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6
Epidermis
  • Avascular, keratinized stratified squamous
    epithelium
  • Cells
  • Keratinocytes (majority)
  • Melanocytes
  • Langerhans cells
  • (a.k.a. epidermal dendritic cells)
  • Merkel cells
  • Layers/strata (from deep to superficial)
  • Stratum basale (basal layer)
  • Stratum spinosum (prickly layer)
  • Stratum granulosum (granular layer)
  • Stratum lucidum (clear layer) not found in
    thin skin
  • Stratum corneum (horny layer)

7
Dermis - Overview
  • Dense, irregular connective tissue Well-supplied
    with blood vessels, lymphatic vessels nerves
  • Cells typical of connective tissue proper
    fibroblasts, macrophages, occasional mast cells
    WBCs
  • Semi-fluid matrix heavily embedded with collagen,
    elastin and reticular fibers
  • Contains cutaneous receptors, glands hair
    follicles

8
Layers of the Dermis
  • Papillary superficial relatively thin
  • Areolar connective tissue
  • Dermal papillae that protrude into epidermis
  • Epidermal ridges that produce fingerprints
  • Reticular deep, 80 of dermal thickness
  • Connective fibers more densely interwoven
  • Less dense regions between collagen bundles
    produce cleavage (tension) lines in skin
  • Points of tight dermal attachment to hypodermis
    produce dermal folds or flexure lines

9
Skin Color
  • Skin color reflects the amount of pigments
    (melanin carotene) oxygenation level of
    hemoglobin in the blood
  • Melanin production is stimulated by exposure to
    UV light
  • Melanin is produced by melanocytes transferred
    to keratinocytes where it protects keratinocyte
    nuclei from damaging effects of UV radiation
  • Skin color can be affected by emotional state
  • Alterations in skin color may indicate certain
    diseases

10
Appendages of the Skin Sweat Glands
  • a.k.a suduriferous glands
  • 2 sub-categories
  • Eccrine (merocrine) sweat glands
  • Distributed over entire body surface, primary
    function is thermoregulation
  • Simple, coiled tubular glands that secrete a salt
    solution with a few other solutes
  • Ducts usually empty to skin surface via pores
  • Apocrine sweat glands
  • May function as scent glands
  • Primarily in axillary and anogenital areas
  • Secretion similar to that of eccrine secretion,
    but also contains proteins fatty substances on
    which bacteria thrive

11
Appendages of the Skin Sebaceous (oil) Glands
  • All over body surface, except hands and soles
  • Simple, aveolar glands, ducts usually empty into
    hair follicles
  • Oily secretion, called sebum, lubricates the skin
    and hair, and acts as a bactericidal agent.
  • Activated (at puberty) and controlled by
    androgens

12
Hair
  • Hair consists of dead, heavily keratinized cells
  • Hair color reflects amount and kind of melanin
    present
  • 2 regions
  • Root (embedded in skin)
  • Shaft (projects from the skin)
  • Hair structure
  • Central medulla (core)
  • Cortex
  • Outer cuticle

13
Hair Follicles
  • Extend from epidermal surface into the dermis,
    deep end expands forming a bulb
  • Richly vascularized
  • Sensory nerve endings, root hair plexus, wraps
    around each hair bulb. Bending hair stimulates
    these endings, hair act as sensitive touch
    receptors
  • Arrector pili muscles pull follicles into an
    upright position, producing goose bumps
  • Components
  • inner epidermal root sheath, enclosing the matrix
    (region of hair bulb that produces hair)
  • Outer connective tissue sheath derived from
    dermis

14
Types Growth of Hair
  • Two classifications
  • Vellus body hair of children and adult females
  • Terminal coarser, longer hair of eyebrows
    scalp
  • Usually darker
  • Appear in axillary and pubic regions during
    puberty
  • Influences on hair growth and density
  • Poor nutrition poor hair growth
  • Conditions that increase blood (chronic physical
    irritation or inflammation) flow generally
    enhance local hair growth

15
Hair Thinning and Baldness
  • Hair grows fastest from teen years to 40s, then
    slows
  • Hair thinning or alopecia results from hairs are
    not replaced as fast as they are shed
  • True baldness (male-pattern baldness) is an
    x-linked genetic condition

16
Nails
  • Scale-like modification of the epidermis
  • Correspond to hooves or claws or other animals
  • Composed of keratin, like hair
  • Normally appear pink because of bed of
    capillaries under nail bed, region over thick
    nail matix appears as a white crescent, lunula

17
Functions of the Integumentary System
  • Protection chemical barrier (antibacterial
    sebum), physical barrier (hardened keratinized
    surface), and biological barrier (phagocytes)
  • Temperature regulation Skin vasculature sweat
    glands, regulated by nervous system
  • Cutaneous sensation sensory receptors respond to
    temperature, touch, pressure and pain
  • Metabolic functions Vitamin D synthesized from
    cholesterol in skin cells
  • Blood reservoir extensive vascular supply of
    dermis
  • Excretion sweat contains small amounts of
    nitrogen wastes

18
Homeostatic Imbalances Skin Cancer
  • Most common cause is UV exposure
  • Basal cell carcinoma and squamous cell carcinoma
    are cured if removed before metastasis
  • Melanoma (cancer of melanocytes), is less common
    but more deadly
  • Basal Cell Carcinoma Squamous Cell Carcinoma
    Melanoma

19
Homeostatic Imbalances Burns
  • Initial threat is loss of protein and electrolyte
    rich body fluids, which may lead to circulation
    collapse
  • Bacterial infection is also a significant threat
  • Rule of Nines to evaluate extent of burn
  • Classified, in increasing severity, as
    first-degree, second-degree and third-degree.
    Third degree requires grafting for recovery

20
Evaluating Burns
21
Developmental Aspects
  • Epidermis develops from embryonic ectoderm,
    dermis (and hypodermis) develop from mesoderm.
  • Fetus exhibits a downy lanugo coat. Fetal
    sebaceous glands produce vernice caseosa, which
    helps protects fetal skin from watery
    environment.
  • Newborns skin is thin. During childhood, skin
    thickens and more subcutaneous fat is deposited.
    During puberty, sebaceous glands are activated
    and terminal hairs appear in greater numbers.
  • In old age, rate of epidermal declines and skin
    and hair thin. Skin glands become less active.
    Loss of collagen, elastin fibers and subcutaneous
    fat lead to wrinkling. Delayed action genes
    cause graying and balding. Photodamage is a
    major cause of skin aging.
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