INTEGUMENTARY SYSTEM Flashcards
Integumentary system
Consists of the skin and its associated structures. It is the largest organ in the body and makes up about 16% of body weight in adult human
3 main functions of integumentary system:
- Protection: Skin protects from basic elements of nature (wind, water, UV sunlight)
- Sensory function: Hair root plexus senses physical disturbance, epidermis/dermis/hypodermis contain sensory neurons that detect touch, temperature and pain
- Thermoregulation: Sweat glands and accessory structures help cool body when it becomes warm
Skin
Organ composed of tissues that work together as a single structure to perform unique and critical functions
Skin function
Functions in protection of body
Skin structure
Made up of multiple layers of cells and tissues held to underlying structures by connective tissue and has sensory and nerve fibers ensuring communication from brain
Epidermis
Avascular (no blood vessels), composed of layers of keratinized stratified squamous epithelium
Thick skin
Refers to the 5 layers (everything including stratum lucidum) of cells in skin and is found only on palms of hands and soles on feet
5 layers of skin:
- Stratum basale
- Stratum spinosum
- Stratum corneum
- Stratum lucidum (only present in thick skin)
- Stratum granulosum
Keratinocytes
Cell that manufactures and stores keratin protein
Keratin
Intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties
Stratum basale structure (3):
- Deepest layer attaching epidermis to basal lamina
- Cells bond to dermis through collagen fibers of basement membrane
- Single layer of cells primarily composed of basal cells which are cuboidal shaped stem cells and precursors of keratinocytes
Dermal papillae
Finger like projections or folds, strengthens connection between epidermis and dermis
2 types of cells that can be found in stratum basale:
- Merkel cells: Receptors for touch
- Melanocytes: Produce pigment melanin
Stratum Spinosum structure (2)
- SPINY in appearance due to protruding cell processes that connect via desmosomes
- 8-10 layers of keratinocytes formed from cell division in stratum basale
Langerhan cells
Immune cells scattered on stratum spinosum functioning in macrophages by engulfing bacteria, foregin particles and damaged cells
Keratinocytes function in stratum spinosum
Produce keratain and release water-repelling glycolipid that helps prevent water loss from body making skin waterproof
Stratum granulosum structure (3)
- GRAINY appearance due to changes by keratinocytes moving from stratum spinosum
- Cells become flatter and cell membrane thickens
- Production of fibrous keratin and accumulation of keratohyalin granules
What happens to nuclei and other organelles as cells die in stratum granulosum
Nuclei and other organelles disintegrate as cells die, leaving behind keratin, keratohyalin, and cell membrane
Reasoning for grainy appearance in stratum granulosum
Keratin and keratohyalin forms majority of keratinocyte mass, giving the layer its grainy appearance
Stratum lucidum structure (3):
- SMOOTH seemingly translucent layer above stratum granulosum and below stratum corneum
- Keratinocytes that compose stratum lucidum are dead and flattened
- Cells densely packed with eleiden, a clear protein derived from keratohyalin which gives cells transparent appearance and provides barrier to water
Where is stratum lucidum found
Found ONLY in thick skin of palms, soles, and digits
Eleiden
A clear protein derived from keratohyalin which gives cells transparent appearance and provides barrier to water; found densely packed in stratum lucidum
Stratum corneum structure
Most superficial layer of epidermis with 15-30 layers of cells exposed to outside environment
Stratum corneum function
It is a dead, dry later so it helps prevent penetration of microbes and dehydration of underlying tissues and provides mechanical protection against abrasion and sheds periodically and replaced by cells pushed from layer below
How does stratum corneum get its name
From the increased keratinization of cells in this layer of skin
Dermis
Considered the core of the integumentary system containing blood, lymph vessels, nerves, hair follicles, and sweat glands
Two layers of connective tissue that composes dermis:
- Papillary layer (superficial)
- Reticular later (deep)
- Compose an interconnected mesh of elastin and collagenous fibers produced by fibroblasts
Papillary layer (3):
- Made up of loose areolar connective tissue
- Contains fibroblasts, small amounts adipocytes, abundance of small blood vessels, lymphatic capillaries, nerve fibers, and touch receptors called tactile (meissner) corpuscles
- Contains phagocytes to fight bacteria and other infections
Reticular layer (2):
- Made up of dense, irregular connective tissue
- Well vascularized, has rich sensory and nerve supply
Elastin fibers in skin
Provides elasticity to skin, enable movement
Collagen fibers in skin
Provide structure and tensile strength
Hypodermis
Layer directly below dermis and functions to connect skin to underlying fibrous tissue of bones and muscle. It is well vascularized, loose, areolar connective tissue and adipose tissue that functions for fat storage and provides insulation and cushioning
Proteins involved in skin pigmentation
Melanin, carotene, hemoglobin
Melanin
Gives hair and skin its color, and helps protect living cells of epidermis from UV damage; dark skinned individuals have more melanin than those who are pale
Exposure to UV rays of sun or tanning salons effects on melanin
Cause melanin to be manufactured and build up keratinocytes which darken skin
Increased melanin concentrations significance
Protects DNA of epidermal cells from UV damage but can interfere with vitamin D production
What happens after 10 days of initial sun exposure
Melanin synthesis tend to peak around 10 days which explains why pale skinned individuals tend to suffer sunburns of epidermis initially
Can darker skinned people get sunburnt
Yes, but their sunburns are more protected
Too much sun exposure impacts
Lead to wrinkling due to destruction of cellular structure of skin, or cause sufficient DNA damage resulting in skin cancer
Moles
Larger masses of melanocytes and although most are benign, they should be monitored for changes that could indicate presence of cancer
Hair
Keratinous filament growing out of epidermis and composed of dead, keratinized cells. Strands of hair originate in epidermal penetration of dermis called hair follicle
Hair shaft
Exposed part of hair above skin surface and not anchored to follicle
Hair root
Lies below surface of skin and anchored in follicle
Hair bulb
Deep end of hair follicle containing hair papilla
Hair matrix
Layer of actively growing basal cells
Hair papilla
Surrounded by hair bulb made of connective tissue containing blood capillaries and nerve endings from dermis
Basal cells of hair bulb
Divide and push cells outward in hair root and shaft
External hair
Completely dead and composed entirely of keratin
Hair general functions
Protection, sensory input, thermoregulation, communication
Hair functions (2):
- Protect skin from sun rays, trap/exclude dust particles containing allergens or microbes, and prevent sweat and particles from dripping in eyes
- Hair is sensitive to air movement and disturbances in environment or on surface of skin due to hair plexus surrounding the base of each follicle
Arrector pili
Smooth muscle that each hair root is connected to making hair shaft become erect and adding an insulating layer of air for animals with heavy coat
Nail bed
Specialized structure of epidermis that is found at the tip of fingers and toes
Nail body
Forms at nail root and protects tips of fingers and toes because they are the farthest extremities that experience the maximum mechanical stress. They also form a back-support for picking up small items
Sudoriferous glands
Glands that produce sweat to cool the body when warm
Merocrine glands
Produce sweat that will assist in thermoregulation by evaporating and removing excess heat from the skin
2 main types of sweat glands:
- Eccrine sweat glands
- Apocrine sweat glands
Eccrine sweat gland (3)
- Primary component of thermoregulation in humans and thus help maintain homeostasis
- Produces hypotonic (relative to blood plasma) sweat for thermoregulation
- This type of sweat released by exocytosis composed mostly of water with some salt, antibodies, traces of metabolic waste, and dermicidin (antimicrobial peptide)
Eccrine gland location
Found all over skin surface and most abundant on palms of hand, soles of feet, and forehead
Eccrine gland structure
Coiled glands deep in dermis with the duct rising to a pore on skin surface where sweat is released
Apocrine sweat gland (2):
- Usually associated with hair follicles in densely hairy areas such as armpits, and anogenital regions
- This type of sweat includes water, salt, organic compounds that make sweat thicker and subject to bacterial decomposition and subsequent smell
Apocrine gland location and structure
Larger than eccrine and deeper in dermis, with duct normally emptying into hair follicle
Mammary gland
Found in breasts and produce/secrete milk, nourish growing offspring
Ceruminous gland
Found in external ear canal and produce/secrete mixture of lipids and proteins, combines with sebum and dead keratinocytes to form cerumen (earwax)
Sebaceous gland (2):
- Oil gland found all over the body and helps lubricate and waterproof skin and hair
- Associated with hair follicles and make sebum (mixture of lipids on skin surface)
Sebum
Mixture of lipids on skin surface that lubricates dry and dead layer of keratinized cells of stratum corneum, keeping it pliable
Fatty acids of sebum function
Has antimicrobial properties and prevent water loss from skin
