Lecture 03 Integumentary System
description
Transcript of Lecture 03 Integumentary System
Lecture 03Integumentary System
• 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:
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
Thick and Thin Skin• Thick – palms, soles• Thin – everywhere else – lacks Stratum
lucidum– Hair folicles– Sebaceous glands– Sparser sensory receptors– Lacks epidermal ridges
–Langerhans cells – macrophages which originate in bone marrow - in Stratum Spinosum
Melanocytes – manufacture melanin- in Stratum Spinosum
Keratinocytes – most abundant, undergo keratinization
–Merkel – associated with sensory neurons
Cells of the Epidermis
Layers (Strata) of the Epidermis
• Stratum corneum• Stratum lucidum *• Stratum granulosum• Stratum spinosum• Stratum basale*not in thin skin
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
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
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
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
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
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 Meissner’s corpuscles (touch) & free
nerve endings (pain and temperature)
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
Tattoos• Ink is injected into the dermis – hence the
long lasting nature of tattoos
Accessory Structures of Skin
• Epidermal derivatives• Cells sink inward during
development to form:– hair– oil glands– sweat glands– nails
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
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
Cross section of follicle
• Bulb surrounds papilla
• Division of cells at matrix results in hair growth
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
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
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
Glands of the Skin• Specialized exocrine glands found in
dermis• Sebaceous (oil) glands• Sudiferous (sweat) glands• Ceruminous (wax) glands• Mammary (milk) glands
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
• 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)
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
Nail Growth• Nail matrix proximal to nail root produces growth• Cells transformed into tightly packed keratinized cells• 1 mm per week
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
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
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
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
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
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
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)
THINGS TO WORRY ABOUT
• Your Pores — Portals for Invasion? • Musty Dankness • Fleas & Ticks — Tiny Terrorists
What'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
• 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?