Integumentary System

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Integumentary System

• The skin and related structures

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Functions of Your Skin

• Barrier against microorganisms
• Prevents water loss
• Thermoregulation - helps control body temperature
  (click for link)
• Cutaneous sensation (for sensing your
  environment)
• Excretion of wastes (sweating)
• Aids in vitamin D production (helps body absorb
  calcium and protects against some cancers)
• Stores 5 of bodys blood

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Layers of the skin

• Epidermis (outer most layer)
• Dermis (below epidermis)
• Hypodermis (consists of adipose tissue (fat) -
  separates skin from muscles (technically not part
  of skin))

See Figure 5.1 on pg 153
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Epidermis (see figure 5.2 on pg 154)

• Top portion of the skin
• Avascular (has no blood vessels - nutrients
  diffuse from the blood vessels in dermis)
• Contains four types of cells
• Melanocytes (produce melanin (pigment) - blocks
  UV radiation)
• Keratinocytes (produce keratin - helps prevent
  water loss and acts as tough covering)
• Langerhans (dendritic) cells (part of immune
  system - prevents infection in the skin)
• Merkel cells (sensory receptors for touch)

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Epidermal layers (see figure 5.2 on pg 154)

• Outer (superficial) to inner (deep)
• Stratum corneum (dead cells filled with keratin -
  makes resistant to penetration and abrasions)
• Stratum lucidium (only in thick skin)
• Stratum granulosum
• Stratum spinosum
• Stratum basale (bottom layer) - new cells arise
  from this layer through mitosis (cell division).
  Melanocytes found here

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Epidermal Layers
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Dermis

• Contains blood vessels supplying cells of
  epidermis
• Contains nerve endings, sweat glands, hair
  follicles, sebaceous (oil) glands
• Composed of the proteins collagen (strength) and
  elastin (stretch recoil)

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Dermal Layers

• Papillary layer
• top portion
• forms ridges called dermal papillae (forms
  fingerprints)
• Rich in blood vessels
• Reticular layer
• mostly collagen and elastin fibers
• Hair rooted here
• Contains coiled portion of sweat glands

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Appendages of the skin

• Sudoriferous (sweat glands)
• Sebaceous (oil) glands
• Hair
• Nails

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Sudoriferous Glands (main types)
Apocrine glands Found in axillary (armpit) and
anogenital region Empty secretions onto hair
follicles Secretions also have fatty acids and
proteins (broken down by bacteria - causes body
odor)

• Eccrine (merocrine) glands
• Most abundant type
• Most numerous on forehead, palms and soles of
  feet
• Empty secretion on skin surface
• Secretion is 99 water, some salts, and small
  amounts of urea, ammonia, lactic acid

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Other Sudoriferous Glands

• Ceruminous glands
• Make cerumen (earwax)
• Mammary glands
• Produce milk in females

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Sebaceous (oil) glands

• Attached to hair follicle release sebum (oil)
  onto hair
• Found throughout skin, but most numerous on face,
  neck, upper chest
• Help to moisturize and waterproof hair and skin
• A pimple results when a sebaceous gland is
  infected

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Hair

• Shaft - part of hair extending out of the skin
• hair follicle (pinching in of the epidermis -
  surrounds hair)
• Hair matrix (area of dividing new cells)
• Papilla - dermal tissue at the hair root which
  supplies nutrients to the matrix
• Hair follicle receptor - nerve ending surrounding
  base of follicle

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Hair Growth

• Growth phase
• last from weeks to years (scalp)
• Gets shorter (especially for men) after 40s
• Regulated by hormones and nutrition
• Regressive phase
• follicle shrinks, matrix cells die, hair falls
  out
• Hair loss occurs when growth phase becomes too
  short for new hair to emerge from scalp

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Homeostatic Imbalances of the Skin

• Skin cancers (3 main types)
• Burns (1st, 2nd, and 3rd)

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Genes that Control Cell Division

• Proto-Oncogenes
• Initiate mitosis (accelerator)

• Tumor suppressor
• genes
• Inhibit mitosis (brake)

mutations must occur to both types of genes for
cancer to develop
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Skin Cancers

• Basal Cell carcinoma
• most common (30 of fair skinned people will get
  it
• 99 cure rate (surgically removed)
• involves stratum basale cells
• slow to metastasize

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Skin Cancers

• Squamous Cell carcinoma
• common on head and hands (but can happen on any
  exposed area)
• Can appear as red scaly elevated bump
• Can spread rapidly if not detected early
• arises from cells in stratum spinosum
  (keratinocytes)

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Skin Cancers

• Melanoma
• metastasizes (spreads) quickly/ highest mortality
  rate
• Appears as spreading brown/black patch
• one-third of cases arise from pre-existing moles

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Self-examination for melanomaABCD(E) rule

• Asymmetry (sides are not the same)
• Border (has indentations/bumpy texture)
• Color (variation in the same patch)
• Diameter (larger than a pencil eraser)
• Evolution (the patch changes)

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Second Degree Burns

• Epidermis and papillary layer of dermis (or
  deeper into dermis)
• Blistering occurs due to damaged blood vessels
• Skin heals in 3-4 weeks on average

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Third Degree Burns

• Involves full thickness of skin (dermis,
  epidermis, hypodermis)
• Dehydration most immediate threat
• Low blood pressure due to fluid loss
• Threat of infection
• Skin grafts often necessary