The Integumentary System

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The Integumentary System

• Human Anatomy and Physiology

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Types of Membranes
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Functions of the Integumentary System

• Houses sensory receptors
• Contains immune system cells
• Synthesizes vitamin D
• Excretes small quantities of waste
• Absorption of drugs and other agents

• Protective covering
• Prevents harmful substances and organisms from
  entering the body
• Reduces water loss from deeper tissues
• Regulation of body temperature

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Components of the Integumentary System

• Skin
• Hair
• Nails
• Sebaceous glands
• Sweat glands

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Layers of the Skin

• Epidermis
• Dermis
• Subcutaneous layer (hypodermis)

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Thick versus Thin Skin

• Thick Skin
• Palms of hands and soles of feet
• Hairless
• Subject to much abrasion
• Thicker epidermis (has an extra layer)

• Thin Skin
• Found everywhere else on the body
• Has hair
• Lacks one layer of the epidermis
• Thick and thin are not describing actual
  depth of tissue!!!
• Thickest skin upper back
• Thinnest skin eyelids

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Epidermis

• Stratified squamous epithelium
• Lacks blood vessels
• Grows from the bottom layer (stratum basale)
• Keratinization

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Layers of Epidermis

• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale
• Basement membrane

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Epidermal Layers

• Stratum corneum flattened cells, desicated,
  anucleate cells, keratinized
• Water barrier
• Varies in thickness
• Thickens with unusual amounts of friction ?
  calluses
• Stratum lucidum in thick skin only, cells in
  process of keratinization

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Epidermal Layers continued

• Stratum granulosum only a few cells thick,
  appears granular
• Cells contain numerous keratin granules
• Stratum spinosum several cells thick, numerous
  cytoplasmic processes called spines, nuclei
  elongated
• Stratum basale single layer of cells on bottom,
  contains skin stem cells
• Cells appear cuboidal or low columnar

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Dermis

• Epidermal ridges and dermal papillae
• Irregular dense connective tissue
• Thicker than epidermis
• Muscle and nerve fibers, blood vessels, hair
  follicles, sebaceous glands, and sweat glands
• 2 layers papillary and reticular

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Layers of Dermis

• Papillary layer
• Thinner, superficial layer
• Loose CT
• Contains blood vessels that serve the epidermis
• Contains nerve processes

• Reticular layer
• Varies in thickness, but generally thicker than
  papillary layer
• Contains thicker collagen and elastic fibers
• May contain smooth muscle cells

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Subcutaneous Layer/Hypodermis

• Loose connective tissue and adipose tissue
• Connective tissue fibers are continuous with
  dermis
• Panniculus adiposus layer of adipose tissue
  that insulates and stores energy
• Arrector pili muscles originate here

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Cells of the Epidermis

• Keratinocytes
• Main cell type
• Produce keratin
• Melanocytes
• In stratum basale
• Contain melanin granules
• Langerhans cells
• Involved in contact dermatitis reactions
• Merkel cells
• In stratum basale
• Most abundant in fingertips
• Sense light touch

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Skin Color

• There are 3 pigments involved in skin color
  melanin, carotene, and hemoglobin.
• Melanin is the only pigment made by the skin
  (from tyrosine) and ranges in color from yellow ?
  red-brown ? black.
• Skin color differences result from the kind and
  amount of melanin made and retained by the skin
  cells.
• All humans have relatively the same number of
  melanocytes.

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Skin Color continued

• Freckles and moles are local accumulations of
  melanin.
• A tan is darkening of the skin as a result of
  increased melanin production, usually in response
  to prolonged exposure to UV radiation.
• Carotene is a yellow?orange pigment found in
  certain plant products. It tends to accumulate
  in the stratum corneum and in the fat of the
  hypodermis, and it is more obvious when large
  amounts of carotene-rich foods are eaten.

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Skin Color continued

• Hemoglobin gives a pinkish hue to fair skin which
  is most noticeable in Caucasian skin. A more
  crimson pigment results when the hemoglobin is
  highly oxygenated. Hemoglobin is found in the
  RBCs of the dermal capillaries.
• Hair color is genetically determined and results
  from the amount and type of pigment secreted by
  melanocytes near hair follicles.
• Dark hair has more melanin than light hair. Red
  hair contains an iron pigment called
  trichosiderin, and gray hair is a mixture of
  pigmented and unpigmented hair.

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Nerve Supply to the Skin

• Free nerve endings found in the epidermis and
  papillary dermis sense temperature, vibration,
  pain, etc.
• Encapsulated nerve endings
• Pacinian corpuscles deep dermis and hypodermis
  sense deep pressure
• Meissners corpuscles in papillary region of
  dermis sense light touch

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Hair

• Present on all surfaces except for palms, soles,
  lips, nipples, and parts of external reproductive
  organs
• Made of keratinized cells
• Hair follicle
• Hair papilla
• Hair shaft
• Hair color
• Arrector pili

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Nails

• Protective coverings on the ends of fingers and
  toes
• Nail plate
• Nail bed
• Lunula

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Sebaceous Glands

• Sebaceous glands are associated with hair
  follicles
• Sebum
• Found everywhere except palms and soles
• Acne

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Sweat Glands

• In dermis or superficial subcutaneous layer
• Eccrine glands
• Most numerous
• Produce sweat on hot days and during exercise
• Apocrine glands
• Become active at puberty
• Secretions smell because of bacterial activity
• Active during emotional upset, fright, pain,
  sexual arousal
• Ceruminous glands and mammary glands

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Healing of Wounds

• Inflammation normal response to injury or
  stress
• Epidermal cuts
• Deep cuts
• Blood clots
• Scabs
• Scars

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Healing of Burns

• First degree burns
• Superficial partial-thickness burn
• Second degree burns
• Deep partial-thickness burn
• Third degree burns
• Full-thickness burn
• Rule of 9s

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Aging and Skin

• Epidermal cells reproduce slower ? larger and
  more irregular shape
• Age spots sites of oxidation of fats in
  secretory cells of apocrine and eccrine glands
• Dermis reduces ? wrinkling and sagging
• Drier skin because of less oil from sebaceous
  glands
• Gray or white hair from decreased melanin
  production

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Aging continued

• Slower hair growth and fewer hair follicles ?
  thinner hair and/or hair loss
• Less blood supply to nail beds ? impaired growth
• Diminished sensitivity to pain and pressure
  because of fewer receptors
• Fewer sweat glands, fewer dermal blood vessels,
  and declined ability to shiver ? decreased
  ability to control temperature
• Diminished ability to activate vitamin D ?
  reduced skeletal health