Chapter 5 Integumentary system Flashcards
Integumentray system consist of
Skin
Hair
Nails
Sweat glands
Sebaceous (oil) glands
Functions of skin
Skin is first and foremost a barrier.
Its main functions include:
Protection
Body temperature regulation
Cutaneous sensations
Metabolic functions
Blood reservoir
Excretion of wastes
Chemical barrier
skin secretes chemicals such as:
Sweat which contains antimicrobial proteins
Sebum and defensins which kill bacteria
Acid mantle- low pH which stops some bacteria
Melanin protects against UV radiation
Physical barrier
Flat, dead, keratinized cells surrounded by glycolipids, block: most water and water-soluble substances
Biological barrier
contains phagocytic cells which: engulf foreign antigens and present to white blood cells, activating the immune response
Insensible perspiration
Under normal, resting body temperature, sweat glands produce: about 500 ml/day of unnoticeable sweat
Sensible perspiration
If body temperature rises, dilation of dermal vessels can increase sweat gland activity to produce: 12 L (3 gallons) of noticeable sweat
Designed to cool body
Cold external environment
Dermal blood vessels constrict
Cutaneous Sensations
Cutaneous sensory receptors are part of the nervous system
Respond to stimuli such as: temperature, touch, and pain
Metabolic Functions
Skin can synthesize vitamin: D
Needed for: calcium absorption in the intestine
Requires: exposure to UV light
Lack of: Vitamin D can lead to a bone disorder called rickets
Blood Reservoir
Skin can hold up to 5 % of the body’s total blood volume
Skin vessels can be: constricted to shunt blood to other organs, such as an exercising muscle
Excretion
Skin can secrete limited amounts: of nitrogenous wastes such as ammonia, urea, and uric acid
Sweating can cause: salt and water loss
Epidermis
superficial region
Consists of: epithelial tissue and is avascular
Dermis
underlies epidermis
Mostly: fibrous connective tissue, vascular
Hypodermis (superficial fascia)
subcutaneous layer deep in the skin
Mostly adipose tissue that: absorbs shock and insulates
Anchors skin to underlying structures; mostly muscles
NOT part of skin but shares some function
Which of the layers are considered part of the skin?
Dermis, epidermis
Which of the layers are vascular? Avascular?
Dermis, epidermis
Keratinocytes
Major cells of epidermis
keratinocytes Produce fibrous
Keratin
keratinocytes are Tightly connected by
Desmosomes
Melanocytes
Spider-shaped cells located in the Deepest epidermis
Produce pigment
melanin
Dendritic (Langerhans) cells
Star-shaped, macrophages that petrol deep epidermis
Key activators of the Immune system
Tactile (Merkel) cells
Sensory receptors that sense touch
Stratum basale (Basal layer) (aka Stratum germinativum)
Deepest of all epidermal layers
Consists of a single row of stem cells that actively divide (mitotic), producing two daughter cells each time
10–25% of the layer is also composed of Melanocytes
Stratum spinosum (Prickly layer )
Several cell layers thick
Cells contain a weblike system of intermediate keratin filaments attached to desmosomes
Allows them to resist tension and pulling
Scattered among keratinocytes are abundant melanosomes and dendritic cells
Stratum granulosum (Granular layer)
Four to six cells thick, but cells are flattened, so layer is thin
Cell appearance changes
Cells flatten, nuclei and organelles disintegrate
Keratinization begins
Cells also accumulate lamellar granules, a water-resistant glycolipid that slows water loss
Cells above this layer die
Stratum lucidum (Clear layer)
Found only in thick skin (Palm of hand and sole of foot)
Consists of a thin, translucent band of two to three rows of clear, flat, dead keratinocytes
Stratum corneum (Horny layer)
20–30 rows of flat, anucleated, keratinized: dead cells
Accounts for: Three-quarters of epidermal thickness
Though dead, cells
dead, cells still function to
Protect deeper cells from the environment
Prevent water loss
Protect from: abrasion and penetration
Act as a barrier against biological, chemical, and physical assaults
Cells change by going through
Apoptosis
Dermis
Strong, flexible: connective tissue
Cells include fibroblasts, macrophages, and occasionally mast cells and white blood cells
Contains nerves, blood vessels, and lymphatic vessels
Contains epidermal hair follicles, oil glands, and sweat glands
Papillary Layer
Superficial layer of areolar connective tissue consisting of loose, interlacing collagen and elastic fibers and blood vessels
Loose fibers allow phagocytes to patrol for microorganisms
Dermal papillae
superficial region of the dermis that: sends fingerlike projections up into the epidermis.
Projections contain capillary loops, free nerve endings, and touch receptors (Meissner’s corpuscles)
In thick skin, dermal papillae lie on top of dermal ridges, which give rise to: Epidermal ridges
friction ridges
Enhance gripping ability
Contribute to a sense of touch
Sweat pores in ridges leave unique: fingerprint patterns
Reticular Layer
Makes up 80 % of dermal thickness
Consists of: dense irregular connective tissue
Many elastic fibers provide stretch-recoil properties
Collagen fibers provide strength and resiliency
Cutaneous plexus
a network of blood vessels: between the reticular layer and hypodermis
Cleavage (tension)
lines in the reticular layer are caused by many collagen fibers running parallel to the skin surface
Important to: surgeons because incisions parallel to cleavage lines heal more readily
Flexure lines of reticular layer 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
Melanin
Only pigment made in skin made by melanocytes
Packaged into melanosomes that are sent to
shield DNA of keratinocytes from damaging UV sunlight
UV light destroys
folic acid
-Necessary for DNA synthesis, so insufficient folic acid is especially dangerous for developing embryos
Why did different populations evolve different levels of melanin?
Different latitudes
Carotene
Yellow to orange Pigment
Most obvious in palms and soles
From diet
Hemoglobin
Pinkish hue of pale skin is due to lower levels of: melanin
Cyanosis
blue skin color low oxygenation of hemoglobin
Pallor
blanching or pale Anemiaa, low blood pressure, fear, anger
Erythema
redness Fever, hypertension, inflammation, allergy
Jaundice
yellow cast, liver disorders
Bruises
black and blue marks, clotted blood beneath the skin
Hair
Typically found all over the body except on: palms, soles, lips, nipples, and some portions of external genitalia
Hair Functions
Warn of: insects on skin
Hair on the head guards against physical trauma
Protect from: heat loss
Shield skin from sunlight
Structure of a Hair
Hairs (also called pili) flexible strands of dead, keratinized cells,Produced by hair follicles
