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INTEGUMENTARY SYSTEM The external body covering. (GENERAL FUNCTIONS…
INTEGUMENTARY SYSTEM
The external body covering.
COMPONENTS
Cutaneous Membrane
Two distinct regions
Epidermis
First major region of the skin.
Composed of Keratinized Stratified Squamous Epithelium
Has 4-5 layers of Strata
Contains keratinocytes, melanocytes, tactile epithelial cells & dendritic cells
Protects the dermis from trauma & chemicals
Prevents entry of bacteria/pathogens
Avascular
Sensory Receptors detect pain, pressure, touch and temperature
Dermis
Second major region of the skin. Strong flexible Connective Tissue Mostly made up of Dense Connective Tissue
Consists of 2 Major Regions- Papillary Dermis & Reticular Dermis
Papillary Layer
Upper dermal region
Dermal papillae
-finger-like projections connect the Epidermis to Dermis
Nourishes & supports epidermis
Composed of Areolar Connective Tissue
Folded nature creates large surface area
Reticular Layer
Deepest skin layer
Attaches skin to deeper skin
Composed of Dense Irregular Connective Tissue
Collagen & Elastic fibers throughout = strength
Stores lipids
Contains blood vessels, sweat and oil glands
Subcutaneous Membrane
or can be refereed to as
Superficial Fascia
Hypodermis
Deep to the skin and its epidermis and Dermal layers
Composed of Loose Areolar Connective Tissue and Adipose Tissue
Anchors the skin to underlying structures, mainly muscles
Provide insulation and nutrient storage
Nervous Tissue/ Structures
Sensory Nerve Fibers w/ free Nerve Endings
Appendages of Skin
Derivatives of the Epidermis
Nails
Built in tools that help us pick up objects and scratch itchy skin.
Made of dead keratinized cells
Hard keratin makes them tough & durable
Rests on a bed of epidermis
Hair & Hair Follicles
Found on most body surfaces
Main function- sense light touches
Hair on head protects us from sun and cold
Hair
Flexible strand made of dead cells filled with hard keratin (protein)
Root
Embedded in the skin
Shaft
part of hair that projects above the skin surface
Follicle
Extends from the epidermal surface into the Dermis. Surrounds the root and the deep end of the follicle forms a bulb
Hair Follicle Receptor
Sensory nerve ending wrapped around each hair bulb
Dermal Papilla
The hair papilla protrudes into each hair bulb. It also contains capillaries to supply nutrients and growth of hair
Arector Pili
A smooth muscle cell that attaches the superficial dermis to the hair follicle.When muscle is contracted it causes goose bumps
Exocrine Glands
Composed of Epithelial Tissue
Sweat Glands
Prevents body from overheating, cools and evaporates. Two different types
Eccrine Sweat Glands
Most abundant, found palms, feet and forehead
Mecocrine Secretion
- Apical surface opens up and releases secretion
Function- evaporate and cool
Apocrine Sweat Glands
Located in Axillary, anal and genital areas
Apocrine secretion
- Apical part of cell is pinched off, lipids and proteins part of cell breaks away. Odorless when first secreted but decomposed bacteria on skin produces odor
Function- evaporation cooling, mate selection
Sebaceous Glands
Skin's oil glands. Located wherever we have hair, next to the hair follicle.
Produce sebum
Holocrine secretion
- the whole cell breaks up to form the product
Makes skin & hair oily
Collects dirt, moisturizes hair and skin
Stimulated by hormones
The Dermal Blood Vessels
Consists of two vascular plexuses that nourish and provide temperature regulation
Subpapillary Plexus
The more superficial plexus, located just below
Dermal Papillae
and the
epidermis
Dermal Plexus
The deep plexus is located between the
Dermis
and
hypodermis
.
GENERAL FUNCTIONS
Protection
Cushions and insulates deeper body organs
Protects body from outside elements that could cause bumps, scraps or cuts
Waterproof barrier prevent unnecessary water loss across body surface
Deeper tissues from damage (chemical, dirt, germs, UV radiation, thermal, desiccation)
Temperature Regulation
Thermal regulation through blood vessels & sweat glands
Excretion
Minor Role
Water & Electrolytes
Wastes
Production of Vitamin D
Produced in skin w/ help of UV Radiation
Vit D needed to help absorb calcium
Sensory Reception
Sense organs associated with nerve endings
Distinguish heat, cold, touch, pressure & pain
CELL TYPES IN EPIDERMIS
Keratinocytes
Most abundant cell found in Epidermis
Produce Keratin- tough fibrous protein
Provide physical and mechanical protection
tightly connected to one another by desmosomes
Melanocytes
Found in Stratum Basale
Spider shaped cells
Pigment producing - Melanin
Tactile Epithelial Cells
Or Merkel cells
Found in Stratum Basale sparsely throughout Keratinocytes
Cell associated with disc-like sensory nerve ending
Sensitive to touch
When stimulated send process to Neurons
Dendritic Cells
Star shaped cell
Found in Stratum Spinosum
Part of Immune system
Stretches to other ells
Found in Stratum Spinosum
Stem Cells
In Deepest layer of Stratum Basale
Young Keratinocytes
Divide rapidly
Regeneration of Keratinocytes & Stem Cells
LAYERS OF EPIDERMIS
Keratinized Stratified Squamous Epithelium
Stratum Basale
Deepest epidermal layer, attached firmly to underlying dermis
Single row of cells, mostly stem cells
Melanocytes and Tactile cells also can be found in this layer
Stratum Spinosum
Several layers of keratinocytes connected by desmosomes.
Spine-like extensions
Among keratinocytes are dendritic cells
Stratum Granulosum
Flattened keratinocytes with pre-keratin filaments
Granules that produces a water proofing glycolipid
Makes skin waterproof
Stratum Lucidum
Very flat layer, found only in thick skin.
Consists of a few rows of flat, dead keratinocytes
ie, palms of hands and soles of feet
Stratum Corneum
Most superficial layer
Many cells thick
Dead Keratinocytes
Sacs filled with Keratin
Packed closely together
Shed regularly and fall off
Replaced by cells from deeper layers
Integument ( Skin)
Considered an organ- has more than one tissue type working together to perform certain functions.
Is the largest of all organs