The Integumentary System Skin Appendages. A skin appendage is defined as anything that assists the skin with its function –expelled cells from the epidermis.
Post on 12-Jan-2016
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The Integumentary System
Skin Appendages
Skin AppendagesSkin AppendagesA skin appendage is defined as anything that assists the skin with its function– expelled cells from the epidermis– modifications of the epidermis– appendages in the dermis and subcutaneous
layer develop from special cells that migrate there during embryological development
• glands• nerves• nails• hair
Skin AppendagesSkin AppendagesGlands
• ceruminous
• sebaceous
• sweat
Skin AppendagesSkin Appendagesceruminous glands
• in skin lining ear canal
• specific type of apocrine gland
apocrine – consisting of pinched-off cytoplasm, including some cell membrane
• produces a waxy secretion = cerumen (ear wax)
• openings surrounded by small hairs
Skin AppendagesSkin Appendagessebaceous glands• holocrine gland
holocrine – secretes whole dead cellsThe cells secreted by sebaceous glands
produce and store an abundance of fat along with their membrane organelles
1) cells secreted into gland ducts2) cells burst open3) fats released onto surface of skin as oily
secretion = sebum
Skin Appendages• sebaceous glands secrete sebum into hair
folicles (hair bulbs)
• sebum then moves to the surface of the skin along the hair
• when the gland becomes clogged, sebum backs up
Skin Appendagessweat glands – 2 types
1) apocrine sweat glands
2) eccrine sweat glands
apocrine sweat glands• secrete odorous material into hair folicles
of:– armpits– navel– groin region– areolae
• secretion contains pheromones– play a role in courtship and social behavior
apocrine sweat glandsapocrine sweat glands• secretions of apocrine sweat glands are
readily broken down by bacteria → body odors
• these glands are inactive until puberty
• there is decreased activity in these glands in the elderly
Skin Appendageseccrine sweat glands
• mostly on the skin of:– armpits– forehead– palms– soles
• sweat production varies from individual to individual – gland activity, concentration, and distribution are determined by genetics
eccrine sweat glandseccrine sweat glands
sweat is primarily water with various concentrations of salts, organic compounds, and wastes (like urea)
eccrine sweat glandseccrine sweat glands
• microbes feed of the nutrients in eccrine sweat → body odors
Skin Appendages
nerves
• sensory receptors allow the skin to communicate information from the environment to the body
• sensory receptors are found in all layers of skin – mostly the innermost regions and fascia
Nerves in the Skin
free nerve endings
• numerous
• in the inner part of the epidermis
• pain-sensing
• detect chemicals associated with tissue damage and bleeding → registers as pain
Nerves in the Skin
Merkel cells
• small numbers in the stratum germinativum
• sensitive to gentle physical sensations
• found mostly in areas having special sensitivity like fingertips
Nerves in the Skin
Meissner’s corpuscles (tactile corpuscles)
• upper regions of dermis, in the dermal papillae
• respond to touch
• surrounded by an elongated, club shaped pile of connective tissues
• pressure on the Meissner’s corpuscles compresses the connective tissue, causing the nerve to respond
Nerves in the Skin
Pacinian corpuscles (lamellated corpuscles)
• found in deeper areas of the subcutaneous layer (hypodermis)
• respond to hard pressure, including vibration
• shaped like onions
Nerves in the Skin
Ruffini receptors
• also in the dermal papillae
• detect pressure or constant touch
Nerves in the Skin
Krause end bulbs
• branched throughout the dermis
• sensitive touch receptors
• mostly in the mucous membranes of the mouth
Skin Appendages
Nails– just keratin secretions
• each nail grows forward from a nail root– in the skin-nail fold
• nails grow as long as nail root and skin-nail fold are not severely damaged
Nails
Nail Growth
• keratocytes at the base of the nail move up to the surface
• cells closests to the surface:1) die
2) flatten out
3) press tightly together
4) disentegrate into the nail body (matrix)
Nails
• as cells in the matrix accumululate, they continuosly push the nail forward
Nail Parts• lunula – white part at the base of the nail
body• nail plate – pink portion underneath the
nail body• cuticle – outgrowth of upper part of skin-
nail plateaverage growth is 1/8 inch per month
Skin AppendagesHair
• considered a modified stratum corneum, formed by an inward protrusion of the epidermis = hair follicle (hair bulb)
• base of the follicle, in the subcutaneous layer, is called a hair papilla– supplied by small blood vessels– connected to a nerve
Hair• The dead, hardened cells protruding from
the infold of the skin which formed the follicle become the main part of hair – the hair shaft
• most hairs have 2 layers
1) cortex– dead, densely packed cells full of keratin
2) medulla– inner layer– loosely arranged cells
Hair• larger hairs have a dried surface = cuticle
• the keratin in the cells gives the hair a yellowish color
hair color
• melanocytes at the base of the hair secrete red, brown, and black pigments
• differences in color due to amount and location of melanin in the cortex and medulla
• controlled by genetics
HairHair cycle = the mitosis cycles that the hair follicle undergoes to produce a length of hair
• newly formed hair cells move up the follicle
• newer cells formed beneath
• cells dry out, fill with keratin, harden, and die
HairIn addition to sebaceous glands, hair follicles also have an arrector pili muscle– band of smooth muscle– holds the hair erect
In fine body hair, vellus hair, the arrector pili muscle helps the hair to act like a sensitive touch receptor
Use of Hair Shaft Cells in Forensics• Hair cells capture many types of chemicals
that pass through the blood
• Any drug or poison that has been in a person’s body can be found in hair
• Drug-testing can be performed on the metabolic products found in the living cells at the base of the hair follicle– morphine found in hair of mummies– residues of drug breakdown found in older
cells
Use of Hair Shaft Cells in Forensics• DNA and mitochondria can be removed
from hair cells → genetic testing– genetic testing on hair from bodies buried for
hundreds of years
diagram of a sebaceous gland
cross section slide of skin showing sebaceous gland
A) normal sebaceous gland
B) dirt clogs pore
C) sebum gets trapped
D) bacteria begins to grow
E) acne develops
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