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CHAPTER 5 The Integumentary System


The Integumentary system is defined as the skin and all associated structures ... type: oval = wavy hair; flat ribbon-like = kinky/ curley; round = straight hair. ... – PowerPoint PPT presentation

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Title: CHAPTER 5 The Integumentary System

CHAPTER 5The Integumentary System
  • 1. Functions of the integumentary system
  • 2. Structure of the skin
  • 3. Accessory structures of the skin
  • 4. Skin pigmentation

  • The Integumentary system is defined as the skin
    and all associated structures (hair, nails, and
  • Consists of an epidermis and dermis.
  • The hypodermis is generally not considered as
    part of the skin proper.

Integumentary system

Functions of the integument
  • Body temperature regulation - via perspiration
    and vasodilation of skin blood vessels.
  • Protection - barrier against foreign material
    entering body and loss of fluids and electrolytes
    through skin.
  • Stimuli perception via nerve endings and
    receptors sensing temperature, pressure, pain,
  • Excretion of waste materials loss of urea,
    amino acids, uric acid, electrolytes, sugars,
  • Synthesis of Vitamin D3 precursor molecules in
    skin are stimulated by sunlight to begin
    production of calcitrol.

Epidermis (Epithelial layer)
  • Keratinized stratified squamous epithelium
  • Contains 4 distinct cell types
  • -Keratinocytes melanocytes Merckel cells and
    Langerhans cells
  • Is avascular and receives nutrients from dermis
  • Made up of 4 (5) distinct layers Stratum basale
    Stratum spinosum Stratum granulosum Stratum
    lucidum and the Stratum corneum. On palms and
    soles 5th layer (stratum lucidum) is present.


Cells of the skin
  • Keratinocytes- most predominant cell in skin
    produce keratin, a tough fibrous protein that
    gives skin its protective properties. Also
    produce antibodies and enzymes that detoxify
    harmful chemicals and agents that may enter the
  • Melanocytes- spider shaped cells that produce
    melanin a dark pigment in skin.
  • Merkel cells- hemisphere shaped cells that are
    sensory touch receptors.
  • Langerhans cells- star shaped macrophage
    phagocytic cells in skin eat foreign proteins.

Skin cells shapes

Epidermal layer 1
  • Stratum basale deepest layer of epidermis firmly
    attached to the dermis.
  • Also known as Stratum germinativum.
  • Consists of a single layer of stem cells
    representing young keratinocytes and exhibits a
    lot of mitotic activity.
  • Layer also contains Merckel cells and spider
    shaped melanocytes (10-25).


Epidermal layer 2
  • Stratum spinosum (spiny layer)
  • Several layers thick Thickest layer in thin
  • Derives name from many spiny keratinocyets
    scattered through this layer. Spiny appearance is
    due to fixation artifact and attached desmosomes.
  • Langerhans cells present act as part of immune
    system to scavenge foreign proteins that invade


Epidermal layer 3
  • Stratum granulosum
  • Consists of 1-5 layers of keratinocytes
  • Also contains keratinohyaline granules and
    lamellated granules. Former cells form keratin in
    more superficial layers of epidermis and latter
    cells form a glycolipid layer which acts as
  • Receives nutrient from capillaries in dermal
  • Layers above here are dead keratinized cells


Epidermal layer 4Found in thick skin only
  • Stratum lucidum (clear layer)
  • Occurs only in thick skin of palms and soles
  • Does not occur in thin skin
  • Consists of a few layers of flat dead
    keratinocytes that have a transparent appearance.


Epidermal layer 5
  • Stratum corneum (Horny layer)
  • Most superficial layer of epidermis
  • Many cell layers thick
  • Consists of dead keratinized cells that are
    filled with keratin and no longer have nuclei and
  • Is the layer that is shed as dandruff flakes from
  • Is beauty really only skin deep??
  • If so than what we are looking at is dead tissue
  • Average person sheds 40 lbs. in a lifetime


Dermis (fibrous connective tissue)
  • Second layer of skin
  • Is a strong flexible dense irregular connective
    tissue containing mast cells, macrophages,
    fibroblasts, and scattered leukocytes.
  • Also contains elastic, reticular and collagen
  • Dermis is what binds the body together.
  • Richly supplied by nerves and blood vessels.
  • Consists of 2 layers Papillary and Reticular

Dermis continued
  • -Papillary layer
  • Most superficial layer of dermis consists of
    areolar CT with collagen and elastic fibers.
  • Dermal papillae form dermal ridges that form our
    fingerprints, palm prints and footprints.
  • Reticular layer
  • -80 of dermis
  • -consist of dense irregular CT
  • -named for its network (reticulum) of collagen



Dermal sensory receptors
  • Free nerve endings sensitive to temperature, pain
    (nociceptors) and pressure
  • Meissners corpuscles sensitive to light
    pressure, discriminative touch, low vibrations.
  • Pacinian corpuscles sensitive to deep pressure,
    high frequency vibration. Adapt rapidly.

Hypodermis (fatty layer)
  • Not actually a layer of the skin
  • Also known as a subcutaneous layer or superficial
  • Deep to dermis consists of adipose and areolar
    connective tissue.
  • Anchors skin to deeper structures (mostly
    muscle) but loose enough to allow skin to be
    flexible and movable.
  • Acts as a good body insulator

Skin Color
  • Three pigments contribute to skin color
  • Melanin produced by melanocytes but accumulates
    in keratinocytes of stratum basale and stratum
  • Two forms of melanin eumelanin and pheomelanin
  • Carotene yellow pigment most conspicuous in heel
    calluses and corns in stratum corneum.
  • Hemoglobin red pigment in rbcs, imparts red
    color to skin through blood vessels

Skin accessories
  • Glands sebaceous and sweat (sudoriferous
    glands), and ceruminous glands
  • Hair (pilus/pili) derived from keratin
  • Nails are produced from keratin

Skin glands
  • Sebaceous glands produce an oily secretion
    called sebum. Usually open into a hair follicle.
  • Their secretion is holocrine
  • Sebum keeps skin moist and flexible and gives
    hair a sheen
  • Sudoriferous sweat glands are of 2 kinds
    apocrine and merocrine.
  • Merocrine most numerous produce watery
    perspiration for cooling body most abundant on
    palms, soles and forehead.
  • Apocrine present in groin, axilla, anal, areola,
    and beard regions ducts open into hair follicle
    sweat is thicker milkier due to fatty acids.
    Strong odor is due to bacterial decay.
  • Scent glands that respond to stress and sexual
  • Become fully functional at puberty.
  • Open into hair follicles


Skin glands
  • Ceruminous glands found only in the external
    auditory canal.
  • Secretion is called cerumen which is waxy and has
    a viscous texture and bitter taste. It repels
    insects and kills bacteria and waterproofs the
  • Are modified sweat glands apocrine.
  • Mammary glands specialized sweat glands that
    produce milk in pregnant females.


Hair (pilus) characteristics
  • Hair is made of dead keratinized cells and
    consists of a
  • bulb, root and shaft and grows within a follicle.
  • Arrector pili muscle (sm. m.)- under sympathetic
  • Three concentric layers
  • 1. medulla central core
  • 2. cortex several layers of flattened cells
  • 3. cuticle single layer of cells that overlap
    like shingle forming outermost portion gives
    hair strength and keeps it from matting


Three kinds of hair
  • Lanugo fine downy hair present in fetus and
    replace dat birth.
  • Vellus fine unpigmented hair. Approx 2/3 of
    hair in ? and 1/10 in ? and all hair in
    children, except eyebrows, eyelashes and scalp
  • Terminal - longer, coarser, and pigmented. Forms
    eyebrows, eyelashes, scalp and pubic, axillary,
    and facial hair after puberty.

Hair texture and color
  • Shaft shape on x-section determines hair type
    oval wavy hair flat ribbon-like kinky/
    curley round straight hair.
  • Hair color is due to amounts of melanin in
  • Brown and black have large amounts of eumelanin
  • Red has less eumelanin but more pheomelanin.
  • Blond has intermediate amount of pheomelanin but
    little eumelanin.
  • Gray or white is due to absence of melanin and
    air in the medulla.



Nail anatomy
  • Nails are a modification of stratum corneum
    composed of very thin dead scaly cells closely
    packed together and filled with parallel keratin
  • Claws and hooves in most mammals nails are a
    distinguishing characteristic of primates.
  • Serve to allow us to pick up very small objects
    and manipulate as well as being used for tearing,
    digging and scratching.

Nail anatomy
  • Nail matrix- growth zone at proximal border
    concealed under skin of nail plate.
  • Nail plate- visible portion of nail covering tip
    of finger or toe. Consists of root, body and free
    edge of nail.
  • Nail groove and fold- lateral edge of nail plate.
  • Free edge- distal most edge of nail plate over
    tip of finger or toe.
  • Eponichium- cuticle is dead epidermal tissue
    covering proximal end of nail.
  • Lunule- thick white crescent shaped area distal
    to eponichium. Obscures dermal vessels below.


Injury and Repair
  • The skin can regenerate after injury.
  • After injury there are four stages of healing
  • After injury bleeding usually occurs into the
  • Clot or scab forms at the surface of the
  • Granulation occurs and the clot dissolves.
  • Scar tissue forms and the extent of scarring
    depends on the degree of the injury.

  • Burns to the skin are graded in degrees
  • First degree involves superficial layers of the
    epidermis and will be inflamed and tender
  • Second degree penetrate deeper and may enter
    reticular layer of dermis leading to blisters and
  • Third degree kill all epidermal and dermal layers
    and may penetrate the hypodermis. Such injuries
    are very painful and can be life threatening if
    injury is very extensive.

Aging and the skin
  • As we get older, our skin takes on significant
  • It tends to get thinner and drier as glandular
    function decreases.
  • Skin injuries and infections increase and immune
    function decreases.
  • Muscles become weaker and the dermis sags and
    becomes more wrinkly.
  • Elastic fiber network decreases causing the skin
    to become less resilient.