Integumentary system Flashcards
Integument
-Is the largest system of the body->16% of body weight
-Protects and interacts with all organ systems
-Changes in skin appearance are used to diagnose disorders in other system
Made up of 2 parts
-Cutaneous membrane (skin)-> epidermis and dermis
-Accessory structures within the dermis
Hypodermis (superficial fascia or subcutaneous layer
-Loose Connective tissue
-Below the dermis
-Location of hypodermic injection
Cutaneous membrane function
-Physical protection from environmental hazards
Storage of lipids
-Coordination of immune response to pathogens and cancers in sking
Accessory structures functin
-Sensory information
-Synthesis of vitamin d2
-Excretion
-Thermoregulation
Epidermis
-Protects the dermis, prevents water loss and the entry of pathogens, and synthesizes vitamin d, sensory receptors detect touch, pressure, pain, and temperature
Dermis
Papillary layer- Nourishes and supports epidermis
Reticular layer- Has sensory receptors that detect touch, pressure, pain, vibration, and temperature. Blood vessels assist in thermoregulation
Hair follicles
-Hair protect skull and provide delicate touch sensation on general body surface
Exocrine glands
-Assist in temperature regulation and waste excretion
Nails
-Protect and support tips of fingers and toes
Function of integumentary system
-Protection of underlying tissues and organs
-Excretion of salts, water, and organic wastes (glands)
-Maintenance of body temperature (insulation and evaportation)
-Production of melanin
Functions of integumentary system
-Production of keratin
-Synthesis of vitamin D3
-Storage of lipids
-Detection of touch, pressure, pain, and temperature
Epidermis
-Consists of Keratinized stratified squamous epithelium
-Avascular (as all epithelia lack blood vessels)
-Depend on the diffusion of nutrients and oxygen diffuse from capillaries of underlaying connective tissue (dermis)
Epidermis
-Separated from the dermis by a basement membrane
-The deepest layer of the epidermis and the underlying dermis interlock, strengthening the bond between the two
Keratinocytes
-Main epidermal cells
-Contain large amounts of keratin -> tough fibrous protein
Stem cells
-Undifferentiated cells that give rise to keratinocytes
-Found in the deepest layer of the dermis (stratum basale)
Melanocytes
-Synthesize pigment melanin that shields DNA from ultraviolet radiation
-Occur only in stratum basale but have branched processes that spread among keratinocytes and distribute melanin
Tactile Cells
-Touch receptor cells associated with the dermal nerve fibers
-In basal layer of epidermis
Dendritic cells
-Macrophages originating in bone marrow that guard against pathogens
-Found in stratum spinosum and granulosum
layers of epidermis
-Two types of skin referring to the thickness of epidermis
Thin skin
-Covers most of the body
-Has four layers
Thick skin
-Covers the palms of the hands and soles of the feet
-Has five layers->from the basement membrane to free surface: Statum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum
Stratum Basale
-Single layer of basal cells or germinative cells (stem cells) -> cells divide and give rise to keratinocytes that migrate towards skin surface to replace lost cells
-Is attached to basement membrane by hemidesmosomes
Stratum Basale
-Forms epidermal ridges that fit a complementary pattern of corrugation of the underlying dermis (dermal papillae)
-Forms a strong bond between epidermis and dermis
-Increase the area of basement membrane
-Strengthen attachment between wpidermis and dermis
Stratum Basale
-Specialized structures of stratum basale
Tactile discs
-Tactile (Merkel) cells with sensory nerve endings
- Found in hairless skin
- Respond to touch
-Melanocytes contain the pigment melanin
Stratum Spinosum “Spiny layer”
-Eight to ten layers of keratinocytes bound by desmosomes
-Named for appearance of cells (spiny); Cells shrink until cytoskeletons stick out
-Continue to divide, increasing thickness of epithelium
-Contain dendritic (Langerhans) cell, activate in immune response
Stratum granulosum (grainy layer)
-Three to five layers of keratinocytes that derive from stratum spinosum
-Stop dividing, starts producing protein fibers
-Keratin: tough, fibrous protein that makes up hair and nails
-Keratohyalin that form dense granules that promote dehydration of the cell and cross linking keratin fibers
-Dehydrate and die
Stratum lucidum (clear layer)
-Pale layer found only in thick skin
-Coverts stratum granulosum
-Keratinocytes packed with clear protein eleidin
Stratum Corneum “horn layer”
-Exposed surface of skin
-Resists abrasion, penetration, water loss
-Several layers (up to 30) of dead, scaly, keratinized cells
-Keratinization of corneation -> The formation of layer of dead, protective cells filled with keratin
Life cycle of a Keratinocyte
-Keratinocytes are produced by mitosis of stem cells in stratum basale
-Mitoses requires abundant oxygen and nutrients, so once cells migrate away from blood vessels of the dermis, mitosis cannot occur
-New keratinocytes push older ones toward the surface
-Over time, keratinocytes flatten, produce more keratin
-It takes up 7 to 10 days for cell to move from stratum basal to stratum corneum and it takes additional 2 weeks before they shed and wash away
Stratum corneum is water resisting but not waterproof
-Water is lost from skin in two ways
Insensible perspiration
-Water diffuses across stratum corneum and evaporates from skin
-500 mL per day
-Rate increases if stratum corneum is damaged
Sensible perspiration
-Water excreted by sweat glands
Epidermal growth factor (EGF)
-A peptide growth factor
-Produced by salivary glands and duodenum
-Used in laboratories to grwo skin grafts
Function of Epidermal growth factor (EGF)
-Promotes division of basal cells
-Accelerates keratin production
-Stimulates epidermal repair
-Stimulates glandular secretion
The dermis
-Located between epidermis and subcuraneous layer
-Anchors epidermal accessory structures (hair follicles, swear glands)
-Two components
-Outer papillary layer
-Deep reticular layer
Papillary layer
-Consists of areolar tissue
-Contains smaller capillaries, lymphatic, and sensory neurons
-Has dermal papillae projecting between epidermal ridges
-Becomes inflamed in dermatitis
-Caused by infection, radiation, mechanical irritation, or chemicals
-May produce itching or pain
The reticular layer
-Consists of dense irregular connective tissue
-Contain large blood vessels, lymphatic vessels, and nerve fiber
-The dermis contains all cell of connective tissue proper
Tension lines (cleavage line)
-Produced by parallel bundles of collagen and elastic fibers in the dermis
-Resist forces applied to skin
-A cut made parallel to a tension line remains shut, heals well
-A cut at a right angle pulls open and scars
The dermal blood supply
Cutaneous plexus.
subpapillary plexus
Cutaneous plexus
-Deep network of arteries along the reticular layer
Subpapillary plexus
-Network of small arteries in papillary layer
-Capillaries drain into small veins that lead to larger veins in subcutaneous layer
Contusion
-Damage to blood vessels resulting in “black-and-blue” bruising
Innervation of skin
-Nerve fibers in skin
-Sensory receptors
Nerve fibers in skin
-Control blood flow
-Adjust gland secretion rates
-Monitor sensory receptors
Sensory receptors respond to
-Light touch–tactile (Meissner) corpuscles, in dermal papillae
-Deep pressure and vibration–lamellar (pacinian) corpuscles, in reticular layer
The subcutaneous layer
-Lies below the integument (deep to the dermis)
-Connected to reticular layer of the dermis by connective tissue fibers
-primarily adipose tissue
-Large arteries and veins are in superficial region
-Pads body and binds skin to underlying tissues
The subcutaneous layer
-Common site of subcutaneous injection using hypodermic needles
-Energy reservoir
-Thermal insulation
-distribution of subcutaneous fat determine by hormones
Skin color
-Skin color is influenced by two factors:
-Epidermal pigmentation
-Blood circulation (red blood cells)
Epidermal pigmentation
-Melanin
-Carotene
-Blood flow and oxygenation influence skin coloe
Melanin
-Yellow-brown or black pigment
-Produced by melanocytes in stratum basale
-Stored in transport vesicles (melanosomes)
-Transferred to keratinocytes
-Dark-skinned people have large, numerous melanosomes
-Protect skin from ultraviolet (UV) radiation
-Small amounts of UV radiation are beneficial
-Too much can damage DNA and cause cancer
Carotene
-Orange-yellow pigment
-Found in orange vegetables
-Accumulates in epidermal cells and fatty tissues of the dermis
-Can be converted to vitamin A required for:
-Maintenance of epithelia
-Synthesis of photoreceptor pigments in eye
Blood flow and oxygenation influence skin color
-Hemoglobin is bright red when bound to oxygen
-When blood vessels dilate from heat, skin reddens
-When blood flow to skin decreases, skin pales
-Hemoglobin turns dark red when oxygen is released
-Can result in cyanosis (bluish skin)
-May be caused by extreme cold, heart failure, severe asthma, etc..
Vitamin D3 (cholecalciferol)
-produced by epidermal cells in presence of UV radiation
-Liver and kidneys together convert vitamin D3 into calcitriol
-Essential for absorption of calcium and phosphate ion by small intestine
Insufficient vitamin D3
-Can cause defective mineralization of bone
-Rickets (children)
- Osteomalacia (adult)
Human hair
-Hair is nonliving structure produced in hair follicle and composed of hard keratin (HK)
-Hair and hair follicles are found almost everywhere
-75% of the 2.5 million are on body surfaces, not head
Function of hair
-Protects the scalp from UV radiation and insulates the skull
-Guarding opening of nostril and external ear canals against particles and insects
-Is sensitive to very light touch
-Eye lashes keep the sweat out of the eyes
Structure of hair follicle
-Extend deep into dermis, produce nonliving hairs
-Wrapped in a dense connective tissue sheath
-Internal root sheath extends from skin surface to hair matrix
-External root sheath extends from skin surface to hair matrix
-Glassy membrane: clear layer wrapped in connective tissue sheath
Regions of the hair
-Hair shaft: upper part of the hair, not attached to the integument
-Hair root: lower part of the hair, attached integument
Hair structure
-Medulla: The central core
-Cortex: The middle layer
-Cuticle: The surface layer
Hair growth cycle
-Growing hair is firmly attached to matrix of follicle
-At the end of the growth cycle:
-Follicle become inactive -> club hair (growth stops)
-Over time club hair disconnect from hair matrix
-When new hair growth cycle begins
-follicle becomes active
-produces new hair
-club hair is shed
Types of Hairs
-Lanugo hair
-Vellus hairs
-terminal hairs
Lanugo hair
-It is the first hair to be produced by the feral hair follicles
-Usually appears around sixteen weeks of gestation and is abundant by week twenty
-Very thin, soft usually unpigmemnted, downy hair that is sometimes found on the body of a fetal or new-born human
Vellus hairs
softer, fine cover body surface
Terminal hair
-Heavy, pigmented
-Head, eyebrows, and eyelashes
-Other parts of body after puberty
Hair color
-Produced by melanocytes at the hair papilla
-Determined by genes
Arrector pili
-Involuntary smooth muscle, causes hairs to stand up (produces “goose bumps”)
Sebaceous glands
-lubricate the hair and control bacteria
Nail
-Made of dead cells packed with keratin to protect the tip of fingers
-Metabolic disorders can change nail structure
Structure of nail
-Nail body: Visible portion of the nail that covers the nail bed
-Side of nails lie in lateral nail grooves and surrounded by lateral nail folds
-The hypomuchium: skin beneath distal free edfe of the nail
Skin exocrine glands
-sebaceous glands (oil glands)
-Two types of sweat glands
1. apocrine glands
2. merocrine (eccrine) glands
Sebaceous glands
-Secrete sebum through holocrine secretion
Sebum
-contains lipids and other ingredients
-lubricates and protects the epidermis
-inhibits growth of bacteria
Sebaceous gland are classified as
-Simple branched alveolar glands associated with hair follicles
-sebaceous follicles
Sebaceous follicles
-Large sebaceous glands not associated with hair
-Discharge sebum directly onto skin surface
-Located on face, back, chest, nipples, external genitalia
Apocrine Sweat Glands
-Found in armpits, around nipples, and groin
-Secrete products into hair follicles via merocrine secretion
-Surrounded by myoepithelial cells
Myoepithelial cells
-Squeeze apocrine gland secretions onto skin surface
-In response to hormonal or nervous signal
Apocrine swear glands
-Produce sticky, cloudy secretions
-Apocrine secretion are a complex mixture of lipids and proteins;
-Are at first odorless but epidermal bacteria act on these molecules to produce odiferous molevules
Merocrine (Eccrine) Sweat Glands
-Widely distributed on body surface especially on palms and soles
-Coiled, tubular glands that discharge directly onto skin surface
-Produce clear secretion consisting water, salts, and organic compounds (ureau)
Functions of merocrine sweat gland activity
-Cooling surface of skin to reduce body temperature
-Excreting water and electrolytes
-Providing protection from environmental hazard
Autonomic nervous system (ANS)
-Controls sebaceous and apocrine sweat glands
-Works simultaneously over entire body
Merocrine swear glands
-Controlled independently
-Sweating occurs locally
Thermoregulation
-The main function of sensible perspiration
-Works with cardiovascular system
-Regulates body temperature
Repair of the integument
-Repairs of the integument following an injury
-Bleeding, swelling, and pain occur
-mast cells trigger inflammatory response
- a scab (dried blood clot) stabilized and protects the area
-Macrophages clean area
-fibroblasts and endothelial cells divide, producing granulation tissue
First degree burn (partial thickness burn)
Only surface of the epidermis is damaged. In this type of burn, which includes most sunburns, the skin redness, a sign called erythema, results from inflammation of sun damaged tisues
Second degree (partial thickness burn)
The entire epidermis and perhaps some of the dermis are damaged. Hair follicles and glands are usually not affected, but blistering, pain, and swelling occur. If the blisters rupture, infection can easily develop. Healing typically takes one to two weeks, abd some scar tissue may form
Three-degree burn (Full thickness burns)
Full thickness burns, destroy the epidermis and dermis, extending into the subcutaneous layer. Despite swelling, these burns are less painful than second degree burn, because sensory nerves are destroyed. These burn cannot repair themselves, because granulation tissue cannot form and epithelial cells cannot cover the injury site. Skin grafting is usually necessary
Rule of nines
A quick method of estimating the percentage of surface area affected by burns
skin function affected by burn
-Burns that cover more than 20% of the skin surface threaten life, because they affect the following function
-Fluid and electrolytes balance
-Thermoregulation
- Protection from infections
Effects of aging on skin
-Epidermis thins
-Number of dendritic cells decreases
-Vitamin D3 production decline
-Melanocyte and glandular activities decline
-Blood supply to dermis is reduced
Effects of aging on skin
-Function of hair follicles declines
-Dermis thins and elastic fiber network shrinks
-Sex-specific hair and body fat distribution fades
-Repair rate slows
