biology 211 anatomy & physiology i dr. thompson. the integumentary system skin = largest organ...
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Biology 211Anatomy & Physiology I
Dr. Thompson
The Integumentary System
Skin =
Largest organ in body
Skin + accessory organs (hair, nails, glands)
= scientific study and medical treatment of the integumentary system
Exposed to radiation, trauma, infections, chemicals, etc.
=
Functions of Integumentary System (skin & its products)
Barrier to keep water and solutes in
Barrier to keep bacterial, dirt, etc. out
Protection against abrasion
Contains sensory receptors for touch, temperature, pressure, pain, etc.
Temperature regulation via hair, sweat, & amount of blood flow
Blood reservoir
Synthesis of vitamin D
Excretion
Epidermis: .epithelium; outer layer is "keratinized" or "cornified"
Dermis:.
Hypodermis:
Three Layers of skin:
Epidermis:
Cells formed by mitosis in deepest, or basal, layer, then get pushed into more superficial layers or "stata"
= Single row of dividing cells
= Three or four layers of cells; Some cell division
= Three or four layers of cells; Actively synthesizing protein keratin
= One or two layers of dying cells
= Many layers of flat, dead, scale-like cells full of keratin
(Epidermis)
Primary cell type in epidermis = keratinocytes which produce large amounts of protein keratin
Other cell types:
produce pigment melanin & transfer it to keratinocytes
(really macrophages) clean up debris
detect touch and pressure; transfer this information to sensory receptors in the dermis
Most significant factor is melanin 2 forms (brownish black) (reddish yellow)
Additional pigment: = yellowHemoglobin in blood = red/pink
Different races: similar numbers of melanocytes, amount of melanin produced differs
Melanin accumulates in keratinocytes
Skin Color
= lack of melanin
= red; increased blood flow, inflammation
= blue; lack of oxyhemoglobin
= pale; decreased blood flow
= yellow; erythrocyte destruction, liver failure
Abnormal Skin Color
Keratinocytes move from stratum basale to stratum corneum, dying as they do so. Average = 6 - 8 wks
- Keratinocytes in stratum basale (& stratum spinosum) lie along basement membrane; divide by mitosis
- Older cells die but remain attached to each other
- Older ones pushed toward surface by newer cells
- Cells eventually shed from stratum corneum
- Keratinocytes synthesize large amounts of keratin and flatten out as they move toward surface
- Melanocytes transfer melanin to keratinocytes
(Epidermis)
Dermis:
Dense irregular connective tissue
Separated from epidermis (stratified squamous epithelium) by basement membrane
Highly vascular
Highly innervated
Two Layers:
just below epidermis
forms deep 80%
Dermis:
Contains many types of sensory receptors for touch, pressure, vibration, pain, temperature, etc.
Some = simple nerve endings
Others = complex structures with multiple cell types
Dermis = Dense irregular connective tissue. Thus:
Cells =
Fibers =
Appendages of the skin
Hair follicles and hairSweat glandsSebaceous (oil) glandsNails on fingers and toes
All begin as epidermis of embryo; grow down into dermis
Hair
Distributed over all skin except: palms of hands soles of feet nipples glans of penis & clitoris minor labia
Minimal trunk & limb hairThicker on scalp to retain heatEyebrows enhance facial features, shade eyesNostril hair filters dust & other particulatesPubic hair, axillary hair, anal hair retain pheromones
Hair
Formed in
Consists of layers of dead, highly keratinized keratinocytes
Loosely arranged keratinocytes
Densely packed keratinocytes
Keratinocytes loosely arranged like
scales
Black or brown color due to produced by melanocytes and transferred to keratinocytes in follicle. Red color produced by pigments called
Blonde color produced by intermediate levels of pheomelanin and low levels of eumelanin
Texture of hair due to shape of the hair shaft.
The rounder the hair shaft, the
The flatter the hair shaft, the
Black or brown color due to eumelanin produced by melanocytes and transferred to keratinocytes in follicle.
Red color produced by pigments called pheomelanin
Blonde color produced by intermediate levels of pheomelanin and low levels of eumelanin
Each hair is associated with:
Sweat Glands
- 2 to 3 million
Two types: : Distributed over all skin except nipples Simple coiled glands in dermis Duct leads to sweat pore on surface Secrete watery sweat for cooling
: Located only in axillary, pubic, anal regions Larger than eccrine glands Duct opens into opening of hair follicle Thicker sweat, high content of protein and fats Contains scent molecules: sexual, fear, etc.
Sweat is usually
Contains significant amounts of sodium, potassium, calcium, chloride, and trace amounts of other minerals
at rest, more at warmer temperatures
during moderate to intense exercise
in external ear canal. Secretion combines with sebum to form earwax
in breast
Modified Sweat Glands
Sebaceous (oil) glands:
- Branched tubular glands
- Duct opens into opening of hair follicle
- Secretes sebum, consisting of lipids, proteins, ions, carbohydrates,
Nails:
- Tips of fingers and toes - Thick layer of densely packed keratinocytes - Produced by at proximal end, hidden under or cuticle
Deeper layers of epidermis =
Average growth:0.5 mm per week
Major cause of accidental death
Classified by depth of tissue involvement Superficial: involves epidermis only Partial thickness: involves epidermis and some dermis Full thickness: epidermis, dermis, and deeper tissue destroyed
Burns:
Carcinomas (cancers) of the skin:
Basal Cell Carcinoma: Keratinocytes of stratum basale proliferate, invade dermis Relatively low malignancy
Squamous Cell Carcinoma: Keratinocytes of epidermis proliferate May or may not invade dermis Moderate malignancy
Malignant Melanoma: Melanocytes of epidermis proliferate and invade dermis Highly malignant