Integumentary Diseases, Disorders, and Conditions Part II of II
Chapter 5 Unit II: Organization Integumentary System Part I.
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Transcript of Chapter 5 Unit II: Organization Integumentary System Part I.
Chapter 5
Unit II: OrganizationIntegumentary System
Part I
• Body’s largest organ (15% of body wt, 2m2 surface area)• Made of two layers:
• Epidermis• Dermis
• Accessory Organs• Hair• Nails• Cutaneous Glands
• Hypodermis• Below the dermis• Not part of the skin
Integumentary System
Epidermis
Epidermal ridge
Dermis
Dermal papilla
Thick skin
LM x 225
LM x 225
Thin skin
Integumentary System• Thick skin – covers the palms, soles, fingers and toes
- ~0.5mm- stratum corneum is very thick (5 layers)- no sebaceous glands or hair follicles
• Thin skin – covers the rest of the body- ~0.1mm- thin stratum corneum (4 layers)- hair follicles and glands
• Protection of underlying tissues - bears most physical injuries.
• Barrier against pathogens - Few microbes can penetrate intact skin.
• Acid Mantle - slight acidity of pH 4-6 on the surface
• Water proofing
• Barrier to ultraviolet light (UV radiation)
• Vitamin D synthesis Calcitriol – needed for bone health
• Cutaneous absorption & excretion – O2, CO2, fat soluble vitamins
• Sensory - touch, texture, pressure, vibration, and tissue injury
• Thermoregulation - thermoreceptors
• Communication
Functions of your Skin
Composed of five types of cells:• Stem cells – undifferentiated cells
• Keratinocytes – majority of epidermis cells, durability and flexibility
• Melanocytes – synthesize pigment (melanin) shields from UV
• Tactile (Merkel) – receptors for touch
• Dendritic (Langerhans) – stand guard against foreign invaders, phagocytic
Structure of the SkinEpidermis
Layers of the Epidermis
• Simple cuboidal epithelial cells
• 4 types of cells: keratinocytes, Melanocytes, Merkel cells, stem cells
• Stem cells constantly undergoing mitotic cell division
Layers of the EpidermisStratum basale
• 8-10 layers of Keratinocytes
• Deepest cells undergo mitosis.
• Keratin filaments cause the cells to flatten near the surface.
• Desmosomes – attach the cells, give spiny appearance
• Langerhans cells – arise in bone marrow
Layers of the EpidermisStratum spinosum
• 3-5 layers of keratinocytes
• Lamellated granules secrete glycolipids
– waterproof barrier
– forms a barrier between surface cellsand deeper layers of the epidermis
– cuts off surface strata from nutrient supply
• Keratohyalin granules – cross links keratin filaments
Layers of the EpidermisStratum granulosum
• Translucent zone found only in thick skin
• Keratinocytes filled with keratohyalin and eleidin
• Cells have no nuclei or other organelles
• Undergoing dehydration
Layers of the EpidermisStratum lucidum
• Consists of up to 30 layers of dead, dead, keratinized cells
• outermost layer where surface cells flake off.
Layers of the EpidermisStratum corneum
1. Produced by stem cells in stratum basale
2. New cells push others toward surface - keratin filaments
3. Cells grow flat and fill with keratohyalin
4. Organelles disintegrate as they pass the water barrier
5. Cells die and fill with keratin fibers
6. Exfoliate
Life History of Keratinocytes
Layers of the Dermis
Layers of the Dermis
• 0.2mm – 4mm thick
• Fibrous Connective tissue composed of:
– fibroblasts
– collagen, elastic fibers: strength and flexibilty
– Accessory structures embedded here
• Layers
– papillary layer – surface layer, thin zone of areolar
Dermal papillae - extensions of the dermis into the epidermis
increase surface area for attachment, create finger prints
– reticular layer – thick layer of dense irregular
• Other names: Subcutaneous tissue/ superficial fascia
• Mostly adipose• Functions:
1.
2. • Hypodermic injections (subQ)
– highly vascular – Limits tissue damage
Hypodermis
• Composed of hard keratin
• Hair found almost everywhere
– 2.5 million/75% on general body not head
– Not found on thick skin, nipples, lips
– differences between sexes or individuals
• Texture and color
• 3 different body hair types:
– lanugo -- fine, unpigmented fetal hair
– vellus -- fine, unpigmented hair of children and women
– terminal hair -- coarse, long, pigmented hair
Skin OrgansHair
Cuticle
Cortex
Medulla
Hair matrix
Hair papilla
• Hair – keratinized cells• Follicle – oblique tube• Three zones:
– bulb = hair originates– vascular tissue (papilla) in bulb
provides nutrients– root = within follicle– shaft = above skin
• Three layers in cross section:– Medulla (core): soft keratin– Cortex: thick, hard keratin– cuticle (surface):
thin, hard keratin
Structure of Hair and Follicle
Arrector pili muscle
• Straight hair = round
• Wavy = oval
• Tight curls = flat
• Hair color = ratio of
two types of
melanin found in
the cortex
Texture and Color of Hair
Hair Growth Cycle
Epidermis
Dermis
Hair matrix
Sebaceousgland
Old club hair
PiloerectorNew hair
Bulge
Club hair(detachedfrom matrix)Club
Dermal papilla
Degenerationof lower follicle
Hair bulb
2 3Anagen (early) (Growing phase, 6–8 years)Stem cells multiply and follicle grows deeper into dermis; hair matrix cells multiply and keratinize, causing hair to grow upward; old club hair may persist temporarily alongside newly growing hair.
Anagen (mature) Catagen(Degenerative phase, 2–3 weeks)Hair growth ceases; hair bulbkeratinizes and forms club hair;lower follicle degenerates.
Telogen(Resting phase, 1–3 months)Dermal papilla has ascendedto level of bulge; club hair fallsout, usually in telogen ornext anagen.
1
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90% of scalp follicles Detached from Hair falls outGrows down from epidermis nutrients
• Alopecia - General term for all hair loss
• Pattern baldness
– sex-influenced trait
– males: XdefectY (can’t cover up)
– females: XdefectX (no baldness)
– expressed only with high testosterone levels
– follicles are sensitive to androgens causes them to shrink when exposed shorten their lifespan and prevents them from producing hair normally
• Hirsutism - excessive hair growth
– hormone imbalance (ovary or adrenal cortex tumor)
Hair Loss and Growth
• Body hair - (too thin to provide warmth) - alert us to parasites crawling on skin
• Scalp hair - heat retention and sunburn cover
• Beard, pubic and axillary hair - sexual maturity and help distribute sexual scents similar to pheromones
• Guard hairs - prevent foreign objects from getting in– nostrils, ear canals or eyes
• Expression of emotions with eyebrows
Functions of Hair
Skin OrgansFingernail Structure
• Derivative of stratum corneum that grows downward
– densely packed cells filled with hard keratin
• New cells added by mitosis in the nail matrix
• Flat nails allow for fleshy, sensitive fingertips
• protect fingertip and surrounding soft tissue from injury
• enhances precise delicate movements;
• enhances sensitivity (counterforce)
• tool
• Medical diagnosis
• Ex.) iron deficiency = concave nails
• Length and growth rate related to the length of the terminal phalanges
Nails