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A&P Review (Integumentary System)
Terms in this set (52)
An organ system - largest organ in the body (makes up 7% of body weight)
Includes skin and its appendages:
- Skin glands (sweat glands and Sebaceous (oil) glands)
Consists of two distinct regions: epidermis and dermis.
Also contains hypodermis.
- Epithelial tissue
Keratinized stratified squamous epithelium
- Mostly fibrous connective tissue.
- Cells (Fibroblasts, macrophages, and occasionally mast cells and white blood cells)
- Fibers in matrix bind body together ("Hide" used to make leather)
- Contains nerve fibers; blood and lymphatic vessels
- Contains epidermal hair follicles; oil and sweat glands
- Two layers: Papillary, Reticular
-Rich vascular supply.
-Thinner on your ventral surface than your dorsal surface.
- Storage of water and electrolytes.
- Does not shed or regenerate.
Hypodermis (siperficial fascia)
- Subcutaneous layer deep to skin.
- Not part of skin but shared some functions.
- Mostly adipose tissue that absorbs shock and insulates.
- Anchors skint o underlying structures - mostly muscles.
- Produce fibrous protein keratin.
- Major cells of epidermis.
- Tightly connected by desmosomes
- 10-15% of cells in deepest epidermis.
- Produce pigment melanin - packaged into melanosomes. (Protect apical surface of keratinocyte nucleus from UV damage)
Dendritic (Langerhans) Cells
Macrophages - key activators of immune system
Tactile (Merkel) Cells
Sensory touch receptors
Contains five layers and is found in high-abrasion areas (hands, feet). Stratum lucidum is only in this type of skin.
Contains only four layers
Five Layers of Skin (deep to superficial)
1. Stratum basale (keratinocytes develop here)
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum
Stratum Basale (Basal Layer)
Deepest epidermal layer. Also called stratum germinativum. Firmly attached to dermis. Stem cells and melanocytes are here.
Single row of stem cells:
- Actively mitotic
- New cells continually produced
- As cells move toward surface, they die
Stratum Spinosum (Prickly Layer)
- Several layers thick.
- Cells contain web-like system of filaments attached to desmosomes
- Abundant melanosomes and dendritic cells
Startum Granulosum (Granular Layer)
Thin - four to six cell layers.
Cell appearance changes:
- Cells flatten
- Nuclei and organelles disintegrate
- Keratinization begins (keratin forms in upper layers. Water-resistant and slows water loss)
Cells above this layer die.
- Too far from dermal capillaries.
Stratum Lucidum (Clear Layer)
Only in thick skin. Thin, translucent band superficial to the stratum granulosum. A few rows of flat, dead, keratinocytes.
Stratum Corneum (Horny Layer)
- 20-30 rows of dead, flat, anucleate keratinized membranous sacs (no nucleus)
- Three-quarters of epidermal thickness.
- Though dead, its cells have functions
- Protect deeper cells from environment and water loss
- Protect from abrasion and penetration
- Barrier against biological, chemical, and physical assaults
Cell Differentiation in Epidermis
Cell change from stratum basale to stratum corneum.
Accomplished by specialized form of apoptosis.
- Controlled cellular suicide.
- Nucleus and organelles break down.
- Plasma membrane thickens.
- Allows cells to slough off as dandruff and dander.
Shed - 50,000 cells every minute.
- Joins epidermis & dermis
- Basement membrane with fibrous substance + polysaccharide gel - glues epidermis to dermis
- Serves as partial barrier to the passage of some cells and large molecules
Papillary Layer (Dermis)
- Areolar connective tissue with collagen and leastic fibers and blood vessels
- Loose tissue: phagocytes can patrol for microorganisms
- Dermal Papillae: superficial peglike projections
- In thick skin, dermal papillae lie on top of dermal ridges, which give rise to epidermal ridges. Collectively ridges are called friction ridges
Friction Ridges (Papillary Layer)
- Enhance gripping ability
- Contribute to sense of touch
- Sweat pores in ridges leave unique fingerprint pattern
- Some contain Meissner's corpuscles (touch receptors)
- Some contain free new endings (pain receptors)
- In thick skin, can form friction ridges
Reticular Layer (Dermis)
- Makes up ~80% of dermal thickness
- Consists of coarse, dense fibrous connective tissue (many elastic fibers provide stretch-recoil properties. Collagen fibers provide strength and resiliency, bind water, keeping skin hydrated)
- Cutaneous plexus
- Extracellular matrix contains pockets of adipose tissue
- Cleavage (tension) lines are caused bu many collagen fibers running parallel to skin surface (externally invisible, important to surgeons because incisions parallel to cleavage lines heal more readily
- Flexure lines are dermal folds at or near joints (dermis is tightly secured to deeper structures. Skin's inability to slide easily for joint movement causes deep creases. Visible on hands, wrists, fingers, soles, toes)
Cutaneous Plexus (Reticular Later)
Network of blood vessels between reticular layer and hypodermis.
Three pigments contribute:
- Melanin (only pigment made in skin)
Blue skin colour - low oxygenation of hemoglobin
Fever, hypertension inflammation, allergy
Anemia, low blood pressure, fear, anger
Yellow cast. Liver disorder
Inadequate steroid hormones in Addison's disease
Clotted blood beneath skin
Appendages of the Skin
Derivatives of the epidermis
- Hair and hair follicles
- Sweat glands
- Sebaceous (oil) glands
Dead keratinized cells of hard keratin (more durable than soft keratin of skin)
Not in palms, soles, lips, nipples, portions of external genitalia.
- Warn of insects on skin
- Physical trauma
- Heat loss
Hair has pigments
Extend from epidermis surface to dermis.
Two layered wall - part dermis, part epidermis
Hair Bulb (Hair Follicles)
- Expanded deep end.
- Hair follicle receptor (root hair plexus)
- Sensory nerve endings - touch receptors
- Hair matrix - actively dividing area
Arrector Pili (Hair Follicles)
Smooth muscle attached to follicle. Responsible for "goosebumps"
Hair Papilla (Hair Follicles)
Dermal tissue - blood supply
Pale, fine body hair of children and adult females
Coarse, long hair of eyebrows, scalp. At puberty, appears in axillary and pubic regions of both sexes, and the face and neck of males.
Nutrition and hormones affect hair growth. Lose 90 scalp hairs daily.
- Scalelike modifications of epidermis.
- Protective cover for distal, dorsal surface of fingers and toes.
- Contain hard keratin.
- Nail matrix.
Also called sudoriferous glands. All skin surfaces except nipples and part of external genitalia. ~3 million per person.
Two main types:
- Eccrine (merocrine)
Eccrine (Merocrine) Sweat Glands
- Most numerous
- Abundant on palms, soles, and forehead
- Ducts connect to pores
- Function in thermoregulation (regulated by sympathetic nervous system)
- Their secretion is sweat (99% water, salt, antibodies, metabolic wastes
- Confined to axillary and anogenital areas
- Secrete viscous milky and yellowish sweat that contains fatty substances and proteins (bacteria break down sweat, leading to body odor)
- Larger than eccrine sweat glands with ducts emptying into hair follicles.
- Begin functioning at puberty (function unknown but may act as sexual scent gland)
Modified Apocrine Glands
- Ceruminous Glands
- Mammary Glands
Lining of external ear canal; secrete cerumen (earwax)
Sebaceous (Oil) Glands
- not in thick skin of palms and soles
Most develop from hair follicles and secrete into hair follicles.
Relatively inactive until puberty
- Stimulated by hormones, especially androgens
- Oily holocrine secretion
- Softens hair and skin
Functions of the Integumentary System
- Body temperature regulation
- Cutaneous sensation
- Synthesis of Vitamin D (metabolic fx)
Three types of barriers:
Tissue damage caused by heat, electricity, radiation, certain chemicals
- Denatures proteins
- Kills cells
- Dehydration and electrolyte imbalance, leads to renal shutdown and circulatory shock.
To evaluate burns:
- Rule of nines
- Used to estimate volume of fluid loss
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