Lecture 03 Integumentary System

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Lecture 03Integumentary System
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• Integumentary System Skin accessory organs
• Cutaneous membrane
• Epidermis epithelial tissue
• Dermis connective tissue
• Accessory Structures
• Glands
• Hair (hair follicles)
• Nails
• Deep to skin not part of skin
• Hypodermis subcutaneous (subQ) superficial
  fascia

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Overview of Epidermis

• Keratinized, stratified squamous epithelium
• Contains no blood vessels
• 4 types of cells
• 4-5 distinct strata (layers) of cells
• Thick vs. thin skin

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• Thick and Thin Skin
• Thick palms, soles
• Thin everywhere else lacks Stratum lucidum
• Hair folicles
• Sebaceous glands
• Sparser sensory receptors
• Lacks epidermal ridges

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Cells of the Epidermis
Melanocytes manufacture melanin- in Stratum
Spinosum
Keratinocytes most abundant, undergo
keratinization

• Langerhans cells macrophages which originate in
  bone marrow - in Stratum Spinosum

• Merkel associated with sensory neurons

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Layers (Strata) of the Epidermis

• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale
• not in thin skin

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Layers of Epidermis

• Stratum germinativum
• Stratum spinosum
• Stratum granulosum
• Stratum lucidum
• Stratum corneum

• Cell division, pigmentation, cuboidal
• 8-10 rows deep, many sides kerationcytes
• Cells dying, waterpoofing
• Clear, flattened, dead, fingertips only
• 25-30 rows deep, flattened, dead

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Skin Color

• Determined primarily by melanin produced by
  melanocytes physiologic condition
• Two forms
• Phoemelanin which gives a yellow-red color to
  skin
• Eumelanin gives a black-brown color to skin
• Also by carotene which interacts with eumelanin
  in Asian populations
• Albinism/vitiligo lack of pigment all/patches

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• Diagnostic Clues Skin Color
• Jaundice
• yellowish color to skin and whites of eyes
• buildup of yellow bilirubin in blood from liver
  disease
• Cyanotic
• bluish color to nail beds and skin
• hemoglobin depleted of oxygen looks purple-blue
• Erythema
• redness of skin due to enlargement of capillaries
  in dermis
• during inflammation, infection, allergy or burns

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• Epidermal Ridges
• Dermal Papillae projections of dermal layer
• Form in fetus as epidermis conforms to dermal
  papillae
• fingerprints are left by sweat glands open on
  ridges
• increase grip of hand
• Increase contact between Stratum germinativum

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• Dermis
• Deep to epidermis connective tissue What
  kind(s)?
• Does not wear away
• Contains blood vessels, adipose, various
  accessory structures
• Composed of 2 layers
• Papillary
• Reticular

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Papillary Region

• Top 20 of dermis
• Composed of loose connective tissue elastic
  fibers
• Finger like projections called dermal papillae
• Functions
• anchors epidermis to dermis
• contains capillaries that feed epidermis
• contains Meissners corpuscles (touch) free
  nerve endings (pain and temperature)

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Reticular Region

• Dense irregular connective tissue
• collagen and elastic fibers
• aligned in cleavage lines
• Contains interlacing collagen and elastic fibers
• Packed with oil glands, sweat gland ducts, fat
  hair follicles
• Provides strength, extensibility elasticity to
  skin
• stretch marks are dermal tears from extreme
  stretching

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Tattoos

• Ink is injected into the dermis hence the long
  lasting nature of tattoos

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Accessory Structures of Skin

• Epidermal derivatives
• Cells sink inward during development to form
• hair
• oil glands
• sweat glands
• nails

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Hair

• Hair types consisting of keratinized cells
• Lanugo which develops during fetal development
  and disappears prior to birth
• Vellus fine hair which cover body
• Intermediate
• Terminal hair of the scalp, eyebrows, eyelids
• Hair develops from follicles which include
• Oil glands
• Arrector pili muscles which may pull on the
  follicle to cause the hair to stand on end in
  response to fear or cold
• Hair root plexus nerve endings surrounding the
  root which make the hair sensitive to touch
• Hair growth outwards from the matrix, a layer
  of cells in the root

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Structure of Follicle

• Shaft -- visible
• medulla, cortex cuticle
• CS round in straight hair
• CS oval in wavy hair
• Root -- below the surface
• Follicle surrounds root
• external root sheath
• internal root sheath
• base of follicle is bulb
• blood vessels
• germinal cell layer

Follicle
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Cross section of follicle
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• Bulb surrounds papilla
• Division of cells at matrix results in hair
  growth

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Hair Related Structures

• Arrector pili
• smooth muscle in dermis contracts with cold or
  fear.
• forms goosebumps as hair is pulled vertically
• Hair root plexus (network of nerves)
• detect hair movement
• Sebaceous Glands
• Produce oily secretion

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• Hair Growth
• Growth cycle growth stage resting stage
• Growth stage
• lasts for 2 to 6 years
• matrix cells at base of hair root producing
  length
• Resting stage
• lasts for 3 months
• matrix cells inactive follicle atrophies
• Old hair falls out as growth stage begins again
• normal hair loss is 70 to 100 hairs per day

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Hair Color

• Result of melanin produced in melanocytes in hair
  bulb
• Dark hair contains true melanin
• Blond and red hair contain melanin with iron and
  sulfur added
• Graying hair is result of decline in melanin
  production
• White hair has air bubbles in the medullary shaft

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Glands of the Skin

• Specialized exocrine glands found in dermis
• Sebaceous (oil) glands
• Sudiferous (sweat) glands
• Ceruminous (wax) glands
• Mammary (milk) glands

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Sebaceous (oil) glands

• Secretory portion in the dermis
• Most open onto hair shafts
• Sebum
• combination of cholesterol, proteins, fats
  salts
• keeps hair and skin from soft pliable
• inhibits growth of bacteria fungi(ringworm)
• Acne
• bacterial inflammation of glands
• secretions stimulated by hormones at puberty

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• Nails
• Involve free edge which you trim, the body and
  root
• Growth is from the nail bed specifically from
  the matrix an area proximal to the root
• Nail is tightly packed, keratinized cells (dead)

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Structure of Nails

• Tightly packed keratinized cells
• Nail body
• visible portion pink due to underlying
  capillaries
• free edge appears white
• Nail root
• buried under skin layers
• lunula is white due to thickened stratum basale
• Cuticle
• stratum corneum layer

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• Nail Growth
• Nail matrix proximal to nail root produces growth
• Cells transformed into tightly packed keratinized
  cells
• 1 mm per week

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Epidermal Wound Healing

• Abrasion or minor burn
• Basal cells migrate across the wound
• Contact inhibition with other cells stops
  migration
• Epidermal growth factor stimulates cell division
• Full thickness of epidermis results from further
  cell division

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Deep Wound Healing

• If an injury reaches dermis, healing occurs in 4
  phases
• inflammatory phase has clot unite wound edges and
  WBCs arrive from dilated and more permeable blood
  vessels
• migratory phase begins the regrowth of epithelial
  cells and the formation of scar tissue by the
  fibroblasts
• proliferative phase is a completion of tissue
  formation
• maturation phase sees the scab fall off
• Scar formation
• hypertrophic scar remains within the boundaries
  of the original wound
• keloid scar extends into previously normal tissue
• collagen fibers are very dense and fewer blood
  vessels are present so the tissue is lighter in
  color

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Age Related Structural Changes

• Collagen fibers decrease in number stiffen
• Elastic fibers become less elastic
• Fibroblasts decrease in number
• Langerhans cells and macrophages decrease in
  number and become less-efficient phagocytes
• Oil glands shrink and the skin becomes dry
• Walls of blood vessels in dermis thicken so
  decreased nutrient availability leads to thinner
  skin as subcutaneous fat is lost

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Burns

• Destruction of proteins of the skin
• chemicals, electricity, heat
• Problems that result
• shock due to water, plasma and plasma protein
  loss
• circulatory kidney problems from loss of plasma
• bacterial infection

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• Types of Burns
• First-degree
• only epidermis (sunburn)
• Second-degree burn
• destroys entire epidermis part of dermis
• fluid-filled blisters separate epidermis dermis
• epidermal derivatives are not damaged
• heals without grafting in 3 to 4 weeks may scar
• Third-degree or full-thickness
• destroy epidermis, dermis epidermal derivatives
• damaged area is numb due to loss of sensory nerves

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Skin Grafts

• New skin can not regenerate if stratum basale and
  its stem cells are destroyed
• Skin graft is covering of wound with piece of
  healthy skin
• autograft from self
• isograft from twin
• autologous skin
• transplantation of patients skin grown in culture

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Transdermal Drug Administration

• Method by which drugs in a patch enter the body
• Drug absorption most rapid in areas where skin is
  thin (scrotum, face and scalp)
• Examples
• nitroglycerin (prevention of chest pain from
  coronary artery disease)
• scopolamine ( motion sickness)
• estradiol (estrogen replacement therapy)
• nicotine (stop smoking alternative)

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• THINGS TO WORRY ABOUT
• Your Pores Portals for Invasion?
• Musty Dankness
• Fleas Ticks Tiny TerroristsWhat's Embedded
  in Your Bed?
• What Your Mother Never Told You About Those
  Hidden Corners and Cracks
• Pink Mold Slime or Scourge?Mildew Mold's
  Evil Twin
• AND

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• What is the difference between thick and thin
  skin?
• Where does each occur?
• What are the layers of the epidermis?
• of the dermis?
• What kind of tissue is found in each?
• How do nails form?
• Sketch a hair follicle how does a hair grow?
• What is a sebaceous gland what is the purpose
  of their secretions?