Integumentary system (skin) The Integumentary system

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Text of Integumentary system (skin) The Integumentary system

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  • Integumentary system (skin) The Integumentary system
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  • Skin: roles 1- Protects against infection, mechanical shock, chemical injury 2- Prevents fluid loss 3- Sensor for touch, pain, temperature 4- Excretion of sweat 5- Immunity 6- Synthesis of vitamin D 7- Thermoregulation
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  • Integumentary system (skin) Three layers: -Epidermis: the outer/superficial protective layer -Dermis: Deepest and thickest layer of the integumentary system, comprising 2 layers, the papillary and reticular layers - The hypodermis or subcutaneous tissue layer binds the dermis of the skin to the underlying muscle
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  • Epidermis Several layers: -The main layer is located at the base -formed by the active, dividing cells or keratinocytes --The keratinocytes multiply and push up, toward the surface of the skin -As they move away from the base and the blood supply, they die off, dry -Left are dried cells rich in keratin, a stringy protein -They form the upper layer, rich in keratin or corn This keratin (corn) layer (in addition to an oily secretion) has a number of roles: Keratin is somewhat water repellent (water proofs your skin)
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  • Integumentary system (skin)
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  • Skin color Derived from 3 skin pigments: Melanin Carotene Hemoglobin Melanin (brown/black) brown pigment secreted by the melanocytes. Stimulated by UV exposure to protect the basal layer from UV damages. Increased exposure lead to increased melanin synthesis African American and Caucasian have the same number of melanocyte. However, the amount of melanin secreted varies with the human origin and the exposure to UV
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  • Integumentary system (skin) Note: difference between the melanized cells of the stratum basale between the two skin tones. Also recall how the stratum corneum is transparent.
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  • Skin color Excess melanin: Freckles = patches of dense melanin liver spots = sun spots or age spots excess melanocyte activity seborrheic hyperkeratosis excess growth of keratinocytes
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  • Skin color Carotene: yellow pigment found in food (carrot) Hemoglobin red pigment found in the blood Lack of oxygen (Hb only) turns the skin blue (cyanosis)
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  • Sun damages
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  • Tatoos
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  • Integumentary system (skin) Below the epidermis = Dermis -Variations in the layers forms valleys and grooves, seen on the surface of the skin as fingerprint. -The collagen fibers are distributed along a certain orientation surgeons tries to cut along the fibers, not across them, to minimize scarring
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  • Integumentary system (skin)
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  • The dermis Contains: blood vessels nerve fibers Touch, pressure, temperature sensors Muscle, the arrector pili glands
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  • Hypodermis Below the dermis Subcutaneous tissue (not actually part of the skin). Can be thick, if rich in adipose tissue Tthickness varies with location and individuals
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  • Epidermal derivatives: Even though these structures are mostly located in the dermis they originate from the epidermis: Hair Nail Glands - sebaceous glands - sweat glands - apocrine glands - eccrine glands
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  • Epidermal derivatives: Hair Each hair made of a shaft, root and bulb Shaft is what you see (dead cells) Root is below the skin Bulb located at the base of the root within the follicle Follicle is the sheath of epidermal cells around the root Cells divide in the bulb, push their way up This is how hair grows in lengthcells growing Roughly 1mm every 3 days Speed of growth varies with individual and hair location
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  • Hair Note how the stratum basale of the epidermis lines the hair follicle.
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  • Hair Defined lifespan: 3-4 months for eyelash, 3-4 years for scalp Each hair is replaced by a new hair that pushes the old hair shaft out from the follicle You have the same number of folliclesnew hair just reboots the hair bulb to form a new unit. In-grown hair often results when the new hair shaft cannot leave the follicle (due to restriction/constriction of the root). Hirsutism: excessive body hair Hypertrichosis
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  • Hair color Hair color is define by the type and amount of pigment made in the stratum basale Melanin (more = dark) Red hair = presence of iron (trichosiderin) Grey-white hair = lack of pigment due to dying melanocytes (and presence of air bubbles in the shaft) Hair shape - round straight hair, oval curly hair Hair thickness - Depends on the size of the follicle and root
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  • Nails Composed of a compressed layer of stratum corneum cells Hardness derived from dense keratin deposits. Sometimes, the edge get stuck under the skin ingrown nail
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  • Sebaceous glands Derived from the epidermal cells Open in the hair shaft Secrete an oily substance, the sebum, making the skin water repellent Accumulation of sebaceous secretion in a gland lead to the formation of a black head If the gland becomes infected acne
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  • Sudoriferous glands: sweat glands Eccrine sudoriferous gland Distributed all over the body (sweaty palms, back, chest etc.) Non-smelly Open on the skin Apocrine sudoriferous gland Armpits (axillary) and pubic regions open into a hair shaft Smelly sweat Open into the hair shaft
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  • Sudoriferous glands Ceruminous glands: ear wax Only located in the outer auditory canal Cerumen = ear wax For protection of the auditory canal from pathogenic invasion, Also to lubricate the tympanic membrane.
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  • Dermal structures Arrector pili: small muscle attached to hair root and base of epidermis When pulled hair shaft stands up goose bumps Vascular supply nourish epidermis, hair root and dermis itself
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  • Dermal structures: Sensory endings Touch, pressure - sense touch and pressure Temperature receptors sense heat and cold Pain receptors Sense tissue damages
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  • Clinical considerations Wounds Burns Skin cancer Aging
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  • Wounds Open skin is an entry door for bacteria risk of infection. Gravity depends on depth and area involved. Phases of healing: Clot formation scab Inflammatory response Fibroblasts multiply granulations Macrophages phagocytize debris When dermis has filled up, epidermis can grow to cover the area If severe wound: scar tissue
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  • Wound examples
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  • Inflammation 4 cardinal symptoms Bacteria in the wound make contact with defense cells such as mast cells mast cells release histamine Histamine promotes increased permeability of blood vessels tissue swelling Tissue swelling Pain
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  • IInflammation Symptoms of inflammation: - Redness - heat - Swelling -- pain Bacteria also attract macrophages which release chemical promoting dilation of the capillaries (=vasodilation) more blood skin area becomes red (redness) and hot (heat)
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  • Burns Gravity of burns is determined by surface, depth and location Surface: law of 9
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  • Burns Gravity of burns is determined by 1) surface, 2) depth and 3) location Depth: First degree burn: involves epidermis only redness (erythema) sun burn - painful - Skin heals and peals within 10 days no scarring
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  • Burns Depth: Second degree burn: upper dermis involved blister - painful Epidermis heals within few days little/no scarring
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  • Burns Depth: Third degree burn: involves epidermis and entire dermis (and sometimes more) Not painful! Why?
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  • Skin tumors (benign and not) Warts: due to a virus., treated by cryosurgery Skin cancers Basal cell carcinoma: most common, due to UV exposure, arises from basal cells, easily treated Squamous cell carcinoma: from cells above basal cells, more invasive Malignant melanoma: Due to melanocytes changing moles very invasive
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  • Skin tumors (benign and not) Skin cancers Basal cell carcinoma: most common, due to UV exposure, arises from basal cell,,easily treated Squamous cell carcinoma: from cells above basal cells, more invasive Malignant melanoma: Due to melanocytes changing moles very invasive
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  • Melanomas Usually, starts from a mole Watch for changes in shape, height or color of the mole Melanomas are one of the deadliest cancers
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  • Aging Decrease in sebum secretion dry skin Decrease in sweat gland secretion difficulties to cope with heat Decrease in elastin fibers wrinkles Decrease in adipose tissue in the dermis difficulties to cope with cold
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