Class notes

Chapter 5 - Integumentary System

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Course
HLSC 120 - Anatomy (HLSC120)

Institution
University Of Alberta (UofA)

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Uploaded on December 11, 2019
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HLSC120 – Human Anatomy
Chapter 5: Integumentary System

Integumentary system – consists of the skin and its derivatives— nails, hair, sweat o Selectively permeable as it allows some materials to be absorbed
glands, and sebaceous glands while others are blocked
Integument – covering; skin that covers the body; body’s largest organ; skin; o Epidermis is designed to withstand stresses and regenerate itself
cutaneous membrane; vulnerable barrier to the outside world; subjected to trauma, continuously throughout a person’s lifetime
harmful chemicals, pollutants, microbes, and damaging sunlight; usually remains  Prevention of water loss – epidermis is resistant and prevents water loss;
strong and pliable, easily cleaned, self-renewing; serves as a visual indicator of our prevents water w/n body cells and interstitial fluid from leaking out (when
physiology and health skin is severely burned, the main danger is dehydration, because the
Dermatology – scientific study and treatment of the integumentary system individual has lost the protective skin barrier and water can escape from
Structure of the skin – consists of tissue types that collectively perform specific body tissues)
activities: o Transepidermal water loss – when some interstitial fluids slowly
 Covered by an epithelium that protects underlying body layers penetrate the epidermis to the surface, where they evaporate
 Connective tissues that underlie the epithelium contain blood vessels that into the surronding air
provide nutrients to the epithelial cells and provide strength and resilience o Insensible perspiration – release of water vapor from sweat
to the skin glands under normal circumstances when we are not sweating
 Smooth muscle controls both blood vessel diameter and hair position for  Temperature regulation – body temp is influenced by vast capillary
these integumentary structures networks and sweat glands in the dermis; the warmth from the blood
 Neural tissue supports and monitors sensory receptors in the skin, w/c dissipates through the skin and the body cools off by evaporation of the
provide information about touch, pressure, temperature and pain sweat
 1.5 and 2.0 square meters  Metabolic regulation – as little as 15mins of sunlight a day will provide your
 Accounts for 7-8% of body weight body with its daily vitamin D
 Thickness ranges b/w 1.5mm – 4mm depending on body location  Immune defense – epidermis contains Langerhans cells
 Consists of 2 layers o Langerhans cells – phagocytic cells;epidermal dendritic cells; small
Epidermis – a layer of stratified squamous epithelium population of immune cells in the epidermis; initiates an immune
Dermis – deeper layer of dense irregular connective tissue response against pathogens that have penetrated the epidermis
Hypodermis – subcutaneous layer; deep to the dermis; a layer of and also against epidermal cancer cells
areolar and adipose connective tissue; not part of the  Sensory reception – skin acts as an extensive sense organ w/ numerous
integumentary system sensory receptors associated w/ nerve endings that detect heat, cold,
Functions of the skin touch, pressure, texture, and vibration
 Projects internally and meets the mucous membranes w/n the nostrils, o Tactile (Merkel) cells – large, specialized epithelial cells that
lips, anus, urethral and vaginal opening, at these sites, transition is stimulate specific sensory nerve endings when they are distorted
seamless and the epithelial defenses remain intact and functional by fine touch or pressure
 Protection from physical injury, trauma, bumps, and scrapes; against  Excretion by means of secretion – skin exhibits excretory function when it
harmful chemicals, toxins, microbes, excessive heat or cold; protects secretes substances from the body
deeper tissues from solar radiation / UV rays (that’s why when you get a o Sweating – sensible perspiration; occurs when the body needs to
sunburn, your muscles and internal organs remain unaffected) cool itself off; also includes water, salts, urea when secreted

, o Urea – a nitrogenous waste product of body cells  Stratum lucidum – thin, translucent region about 2-3 cell layers thick; found
o Sebum – oily material secreted by the sebaceous glands; only on thick skin (i.e. palms of hands, soles of feet); cells occupying this layer
lubricates the skin surface and hair appear pale and featureless and have indistinct boundaries; keratinocytes w/n
EPIDERMIS this layer are flattened and filled w/ protein eleidin
keratinized, squamous epithelium, avascular, acquire its nutrients through diffusion o Eleidin – an intermediate product in the process of keratin maturation
from the underlying dermis  Stratum corneum – most superficial layer of the epidermis; stratum you see
Epidermal Strata when you look at your skin; consists of about 20-30 layers of corneocytes
 Stratum basale – basal layer; composed of living keratinocytes; deepest o Corneocytes – dead, scaly, interlocking keratinized cells; anucleate
epidermal layer; 3 types of cells that occupy this layer: (lacking a nucleus); tightly packed together
o Keratinocytes – most abundant cell type in the epidermis; found Thick epidermis – found on the palms of the hands, the soles of the feet, and
throughout all epidermal strata; provide the new epidermal cells that corresponding surfaces of the fingers and toes; all 5 strata occur in thick skin;
replace the more superficial dead keratinocytes lost or shed from the contains sweat glands, but no hair follicles or sebaceous glands
surface; synthesizes keratin Thin epidermis – covers most of the body; lacks the stratum lucidum so only has 4
o Melanocytes – scattered in the basal layer; transfer pigment granules layers; contains hair follicles, sebaceous glands, and sweat glands
(melanosomes) that accumulates around the nucleus and shields the Skin color
DNA w/n the nucleus from UV radiation; brown and darker tones of  Hemoglobin – oxygen binding protein present in red blood cells; exhibits a
the skin result from the melanin produced by the synthetic activities of bright red color; giving blood vessels in the dermis a reddish tint that is
melanocytes seen most easily in the lightly pigmented individuals
o Tactile (Merkel) cells – few in number; scattered w/n layer of cells that  Melanin – pigment produced and stored in melanocytes; synthesized from
composes the basal layer; sensitive to touch and when compressed, amino acid tyrosine and its production requires the enzyme tyrosinase;
release chemicals that stimulate nerve endings, providing info about transferred in membrane-bound vesicles from melanocytes to
objects touching the skin; work with other sensory nerve endings in keratinocytes in the stratum basale; affects the color of the entire
the skin epidermis; amount of melain in the skin is determined by both heredity
 Stratum spinosum – several layers of polygonal keratinocytes; cell begins to and light exposure; surrounds the keratinocyte nucleus where it absorbs
differentiate into a nondividing, highly specialized keratinocyte w/c attaches to UV radiation in sunlight preventing damage to nuclear DNA; exposure to
their neighbors by many intercellular junctions (desmosomes) and thus UV light both darkens melanin already present and stimulates melanocytes
resembling mini porcupines attached to their neighbors, this spiny appearance to make more melanin
explains the name of the layer; contains Langerhans cells  Carotene- yellow-orange pigment acquired in the body by eating yellow-
o Langerhans cells – epidermal dendritic cells; immune cells that help orange vegetables (carrots, corn, squash); accumulates inside keratinocytes
fight infection in the epidermis; their phagocytotic activity initiates an of the stratum corneum and w/n subcutaneous fat; converted into vitamin
immune response to protect the body against pathogens that have A w/c is significant in normal vision; reduces number of potentially
penetrated the superficial layers of the epidermis and against dangerous molecules formed during normal metabolic activity and in
epidermal cancer cells improving immune cell number and activity
 Stratum granulosum – in this layer begins the process of keratinisation wherein Skin markings
keratinocytes fill up w/ the protein keratin; cells become thinner and flatter;  Nevus – mole; harmless, localized overgrowth of melanin-forming cells
membranes thicken and become less permeable; nucleus and all organelles  Freckles – yellowish or brown spots that represent localized areas of excessive
disintegrate; cells start to die; a fully keratinized cell is dead bec it has neither a melanocyte activity; degree of pigmentation varies and depends on both sun
nucleus nor organelles, but it is strong bec it contains keratin exposure and heredity

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