Ch 5 the integumentary system
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Ch. 5 The Integumentary System. Introduction. Integument consists of: Skin – largest organ Accessory structures (hair/sweat glands) Subcutaneous tissue Skin Barrier to many harmful substances. The Skin. 2 major layers (Fig. 5-1) Epidermis – outer layer Dermis – inner layer.

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Ch. 5 The Integumentary System

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Ch 5 the integumentary system

Ch. 5 The Integumentary System


Introduction

Introduction

  • Integument consists of:

    • Skin – largest organ

    • Accessory structures (hair/sweat glands)

    • Subcutaneous tissue

  • Skin

    • Barrier to many harmful substances


The skin

The Skin

  • 2 major layers (Fig. 5-1)

    • Epidermis – outer layer

    • Dermis – inner layer


Epidermis

Epidermis

  • Stratified squamous keratinizing epithelium

  • Thickest on palms, soles

  • Abundant keratinocytes

  • No capillaries

  • 2 sublayers

    • inner stratum germinativum

    • outer stratum corneum


Stratum germinativum

Stratum Germinativum

  • “stratum basale”

  • Base of the epidermis where mitosis occurs

    • older cells pushed toward skin surface

      • produce keratin and die

  • Merkel cells (Merkel discs)

    • touch receptors (Fig. 5-2)


Stratum germinativum1

Stratum Germinativum

  • Keratinocytes

    • living cells that synthesize antimicrobial “defensins”

      • rupture pathogen membranes as part of inflammatory process

  • Living portion produces vitamin D when exposed to sunlight


Stratum corneum

Stratum Corneum

  • Outermost epidermal layer

  • Keratin prevents evaporation and water entry

  • Barrier to pathogens & chemicals


Langerhans cells

Langerhans Cells

  • “dendritic cells” (Fig. 5-2)

  • Originate in red bone marrow

  • Phagocytize foreign material

    • migrate to lymph nodes; take pathogen to lymphocytes

      • triggers immune response


Melanocytes

Melanocytes

  • See Fig. 5-2

  • Produce melanin

    • those with darker skin produce large amounts

    • production increased in when exposed to UV rays

  • Melanin gives color to hair, iris, choroid layer of eye

  • See Table 5-1


Dermis

Dermis

  • Made of irregular fibrous connective tissue

    • fibroblasts produce collagen & elastic fibers

      • allow strength & elasticity

  • Papillary layer – junction of dermis with epidermis (Fig. 5-1)

    • abundant capillaries

  • Accessory structures

    • hair & nail follicles, sensory receptors, glands


Hair follicles

Hair Follicles

  • Made of epidermal tissue

  • Base of follicle (Fig. 5-3)

    • Hair root; mitosis occurs in matrix

      • Produce keratin

      • Get color from melanin

      • Die & become incorporated into hair shaft

      • Hair shaft pushed toward skin surface


Hair follicles1

Hair Follicles

  • Eyelashes & eyebrows keep dust & sweat out of eyes

  • Nostril hairs keep dust from entering nasal cavities

  • Hair on head provides insulation

    • body hair doesn’t serve this purpose

  • Pilomotor (arrectorpili muscle) attached to each follicle

    • pull hair follicles upright (fear, cold)


Nail follicles

Nail Follicles

  • On ends of fingers & toes

  • Produce nails; mitosis in nail root at the nail’s base (Fig. 5-4)

  • New cells produce keratin & die

  • Nail is dead keratin cells, but nail bed is alive


Nails

Nails

  • Protect fingers & toes from mechanical injury

  • Allow dexterity

  • Good for scratching


Receptors

Receptors

  • Cutaneous senses

    • touch, pressure, heat, cold, pain

  • Specific receptor for each sensation

  • Receptors & sensation provide CNS with information about external environment


Glands

Glands

  • Made of epithelial tissue (Fig. 5-1)

  • Sebaceous glands

    • Secrete sebum (oil)

      • inhibits bacterial growth on skin’s surface

      • prevents drying of skin, hair

  • Ceruminous glands

    • in the dermis of ear canals

    • secrete cerumen (ear wax)

      • keeps outer surface of eardrum pliable; prevents drying


Glands1

Glands

  • Sweat glands

    • 2 types

      • Apocrine – numerous in axillae (underarm), genital areas

      • Eccrine – numerous on forehead, upper lip, palms, soles


Blood vessels

Blood Vessels

  • Capillaries in dermis

  • Arterioles

    • Smooth muscle in walls permits constriction or dilation

      • maintains body temp.


Subcutaneous tissue

Subcutaneous Tissue

  • “superficial fascia”

  • Made of areolar and adipose tissue

  • Connects dermis to underlying muscles

  • Secondary line of defense


Aging the integumentary system

Aging & The Integumentary System

  • Skin layers become thinner, more fragile

  • Fibroblasts die & are not replaced

  • Repair of breaks or cuts slows

  • Skin wrinkles

  • Glands become less active

  • Skin becomes dry

  • Temp. regulation becomes harder

  • Hair thins, turns white


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