Lecture 9(unit 2)-integumentary System Flashcards
Functions of the integumentary system
- Protection
- Body temperature regulation
- Excretion
- Vitamin D3 synthesis
- Sensory input
- Lipid storage
- Immune Function
Epidermis overview
- Multiple (5)layers of cells (stratified squamous Epithelium)
- Deeper layers of epidermis form epidermal ridges
Primary cell type in epidermis?
-Keratinocytes
•Body’s most abundant epithelial cell.
•Continuously produced by stem cell divisional deepest layers.
•Shed at exposed surfaces
Epidermis layers from top to bottom
- Stratum Corneum
- Stratum Lucidum (only in thick skin)
- Stratum Granulosum
- Stratum Spinosum
- Stratum Basale (Stratum germinativum)
Thin skin vs. Thick skin
-Thin skin • Covers most of body surface • Contains 4 strata (layers) • About as thick as a plastic sandwich bag -Thick skin • Found on palms of hands and soles of feet • Contains 5 strata (layers) • About as thick as paper towel
Stratum Basale
- Basal (bottom) layer of the epidermis
- Attached to basement membrane by hemidesmosomes
- Most cells here are basal cells, stem cells that divide to replace more superficial keratinocytes
- Merkel cells that respond to touch are also found here
Fingerprints
- Pattern of epidermal ridges on surface of fingertips
- Determined by genes and intrauterine environment during fetal development
- Unique pattern that does not change during lifetime
- Used to identify individuals
Stratum Spinosum (“spiny layer”)
- Composed If 8-10 layers of keratinocytes bound together by desmosomes
- Only looks spiny when on a prepared slide
-Contains dendritic (Langerhans) cells
• Part of immune response defending against microorganisms and superficial skin cancers
Stratum granulosum (“grainy layer”)
- Composed of 3-5 layers of keratinocytes
- Most cells have stopped dividing and started producing keratin and keratohyalin
- Cells grow thinner and flatter
- Cell membranes thicken and become less permeable
Stratum lucidum (“clear layer”)
- Found only in thick skin
- Separates stratum corneum from underlying layers
- Flattened, densely packed dead cells filled with keratin and keratohylin
Stratum corneum (cornum, horn)
- Outermost, protective region with 15-30 layers of keratinized cells (filled with keratin)
- Dead Cells still tightly connected by desmosomes
-Water resistant, not waterproof
• Lose water through INSENSIBLE PERSPIRATION ( unable to see or feel) and SENSIBLE PERSPIRATION(sweat)
Hypodermis
- Skin rests on it, but it’s not part of skin
- Aka “Subcutaneous Tissue”, “Superficial fascia”
- Consists of loose connective tissue
-Types of Cells:
•Fibroblasts
•Adipocytes
•Macrophages
Factors affecting skin color
-Hereditary factors:
•Amount of melanin
-Environmental factors:
•Sunlight UV
-Physilogical Factors:
•Vassodialation/Vasoconstriction of dermal blood vessels
•Excercise, blushing
•Accumalation of dietary carotene (orange/yellow color)
Sensory receptors in the integument
- 400cm of nerve fibers per cm2 of skin
Receptors in the epidermis
-Free nerve endings
• Sensitive to touch and pressure
• Between epidermal Cells
-Tactile discs
• Detect texture and steady pressure
• Found in deepest layer of epidermis
Receptors in the dermis
- Meissner’s corpuscles
• Detect light touch, pressure, and vibration
• Found in the papillary layer - Ruffini Corpuscles
• Sensitive to pressure and stretching of skin
• Found in the reticular layer - Lamellated (pacinian) corpuscles
• Detect deep pressure and vibration
•Found in both dermal layers and in hypodermis
What are dermis’s two major layers?
- Papillary layer
- Reticular layer
Papillary layer
- Immediately adjacent to stratum basale’s basal lamina
- Compromised of Areolar (loose) connective tissue, capillaries (thermoregulation), nerves, muscle (arrector pili)
Reticular layer
- Deep to the papillary layer
- Meshwork of Dense irregular CT . Containing both collagen and elastin. Collagen fibers extend into the hypodermis, anchoring the skin
- Surrounds blood vessels and accessory structures (such as hair follicles, sweat/sebaceous glands)
what can u find in Subcutaneous layer/ hypodermis ?
- Adipose
- Blood vessels
Found on nails of fingers and toes (for Protection)
- Nail (keratin)
- Lateral nail folds/grooves
- Eponychium (thickened epidermis bear root)
- Lanula (Pale region distal to eponychium)
- Nail bed (pink due to blood vessels underneath)
- Nail toot (extends deep into dermis, active cell division)
What happens as you grow older?
- Epidermis thins (germinative cell activity slows)
- Fewer Langerhans Cells (poorer immune system)
- Reduced Vitamin D production
- Reduced meloncyte activity (susceptible to UV damage)
- Loss of secondary sexual characteristics (changes in hair/ body fat distribution)
- Hair follicle activity slows or ceases
- Dermis becomes thin, less elastic wrinkles
- Reduction in skin blood supply and activity of sweat glands less able to lose body heat
What are the Four cell types in Epidermis
- Keratinocytes (abundant epithelial Cells in 4-5 layers)
- Melanocytes (produce brown pigment)
- Merkel Cells (sensation touch, surround cell dendrite)
- Langerhans/dendritic Cells (wandering phagocytes [eats bacteria])
Hair growth cycle
- Anagen (growth phase)
- Catagen (transition phase)
- Telogen (resting phase)
Functions of hair
- Thermoregulation
- Protect against UV light
- Guard nostrils/ears/ eyes from foreign particles/ insects
- Social Function (mate attraction, aggression, etc)
