Integumentary System PDF

Unit 3 – The Integumentary System The Integumentary System  Integument is skin  Skin and its appendages make up the integumentary system  Skin, hairs, nails, vessels, nerves, and glands  A fatty layer (hypodermis) lies deep to it The Integumentary System  Two major components: 1. Cuta...

Unit 3 – The Integumentary System The Integumentary System  Integument is skin  Skin and its appendages make up the integumentary system  Skin, hairs, nails, vessels, nerves, and glands  A fatty layer (hypodermis) lies deep to it The Integumentary System  Two major components: 1. Cutaneous Membrane  Epidermis/Superficial Epithelium  Dermis/Underlying Connective Tissue 2. Accessory Structures  Located in dermis  Hair, nails, exocrine glands, blood vessels  Sensory receptors for touch, pressure, temperature and pain  Deep to the dermis, the loose connective tissue of the subcutaneous layer/superficial fascia/hypodermis separates the integument from the deep fascia around other organs Functions of the Skin  Protection  Covering to protect deeper tissues from dehydration, trauma, and germ invasion  Regulate Body Temperature  Controls heat loss  Evaporation of water from the skin, in the form of perspiration  Helps rid the body of excess heat  Helps manufacture Vitamin D  The sunshine vitamin  Ultraviolet light on the skin is necessary for the first stages of vitamin D Functions of the Skin  Storage  Fat, glucose, water, and salt  Absorption  Can absorb certain medications and chemicals  Screens out harmful ultraviolet radiation and eliminates wastes  Site of many receptors and nerve endings for sensory information  Touch, pressure, pain, and temperature Layers of Skin  Epidermis  Dermis  Subcutaneous Membrane  Hypodermis Epidermis  Outer layer of the skin  Renews itself ~ every 45 days Epidermis – Cell Types  Keratinocytes  Produce keratin  waterproofing protein  Originate in deeper layers & get pushed to surface  Connected to each other by desmosomes & tight junctions  Cell production & keratinization are accelerated in areas of friction  Think callus  thickened skin Epidermis – Cell Types  Melanocytes  Produce melanin  Prevents DNA mutation from UV radiation  UV increases melanin production  Same number in everyone but different amount of pigment produced  Accumulation of melanin results in freckles and moles 5 Layers of the Epidermis  In order from deep to superficial 1. Stratum germinative (basale) 2. Stratum spinosum 3. Stratum granulosum 4. Stratum lucidum 5. Stratum corneum  Takes 15-30 days for a cell to move through all five levels Stratum Germinative/Basale  Highly mitotic (goes through mitosis quickly)  Produces new skin layer  ~25% melanocytes Stratum Spinosum  Slightly mitotic – one of the daughter cells from the stratum germinativum is pushed into the stratum spinosum  Consists of 8-10 layers of cells  Contains Langerhans macrophages  Stimulate a defense against:  Microorganisms that manage to penetrate the superficial layers of the epidermis  Superficial skin cancers Stratum Granulosum  Not mitotic but begin making keratin and keratohyalin  Keratin = tough fibrous protein component of hair and nails  Keratohyalin = forms dense granules that dehydrate the cell and aggregate cross-linking of the keratin fibers  Also contains Langerhans cells  Nuclei and other organelles disintegrate = Cell Death Stratum Lucidum  ONLY found in thicker epidermis – palms, soles, callus  Completely keratinized (and dead!)  Contains closely packed, clear cells that contain gel-like substance eleiden Stratum Corneum  Outermost layer – Exposed Skin  Also completely keratinized  Dead cells  Remain in this layer for two weeks before they are shed  Tough, waterproofing protection Dermis  Middle layer of skin – your “hide” – like leather  Contains hair follicles, glands, nerves, vessels, and muscle Layers of the Dermis  Mainly strong, flexible connective tissue – 2 layers 1. Papillary Layer  Upper region  Uneven and has fingerlike projections called dermal papillae that create fingerprints and are important for grip  Contain capillaries, pain receptors (free nerve endings), and touch receptors called Meissner’s corpuscles 2. Reticular Layer  Deepest skin layer  Contains blood vessels, adipose (fat) sweat and oil glands, and deep pressure receptors Hypodermis  Not usually part of the skin  Also called subcutaneous layer  Site of subcutaneous injections – absorbed directly into the blood stream  Anchors skin to underlying organs, bones, and muscles  Shock absorption and insulation  Composed mostly of adipose tissue  Very vascular Skin Color  Skin color is determined by 3 factors: 1. 3 Types of pigments present 1. Melanin  Brown, black, or yellow 2. Carotene  Orange-yellow pigment from some vegetables  Vitamin A precursor – vitamin A forms retinal which is needed for sight  Accumulates in adipose and stratum corneum cells 3. Hemoglobin  Red, oxygen-carrying pigment in erythrocytes  More obviously detected in fair skin 2. Blood circulation 3. Stratum corneum thickness Skin Color  People who produce a lot of melanin have brown-toned skin  The crimson color of oxygen-rich hemoglobin gives the skin a rosy color  When hemoglobin is poorly oxygenated, the skin appears blue – a condition called cyanosis  Common during heart failure and severe breathing disorders Skin Color Signals Disease States  Rubor  Redness or erythema  Embarrassment (Blushing)  Fever  Hypertension  Inflammation  Allergy Skin Color Signals Disease States  Pallor or Blanching  Emotional stress (fear, anger, and others)  Pale skin may also signify anemia , low blood pressure, or impaired blood flow into the area  Jaundice  A yellow-case  Liver disorder in which excess bile pigments is in the blood  Bruises  Sites where blood has escaped and has clotted in the tissue spaces  Called hematomas  Unusual bruising may signify a deficiency of vitamin C or hemophilia Hair  Millions of hairs all over the body  Guards head  Shields eyes (eyelashes)  Keeps foreign particles out of the respiratory tract (nose hairs) Hair  A hair is produced by a hair follicle  Structure of Hair  Shaft – protects skin  Follicle – extends into dermis  Root – lies within the follicle  Bulb – growth zone at the inferior end of the follicle  Sebaceous Gland – lubricates hair  Arrector Pili Muscle – attached to follicle and contracts to move hair (growth or goosebumps) Hair Growth  Influenced by (in this order)  Nutrition – main influence  Hormones  Blood flow  Baldness (alopecia)  Male pattern baldness – sex-linked recessive genetic trait  Thinning – can be caused by medications, nutrition, stress Hair Pigment  Caused by proportions of 3 melanin types: 1. Dark Hair = true melanin 2. Blonde & Red Hair = melanin with iron and sulfur 3. Gray/White Hair = melanin replaced by air bubbles in shaft Nails  Scale-like modification of the epidermis  Heavily keratinized  Stratum basale extends beneath the nail bed to form the nail matrix  Responsible for growth (matrix region)  Lack of pigment makes them colorless  Lunula “little moon” – area of cell growth (white semicircle at base of nail)  Cuticle – area of skin that covers base of nail Glands of the Body  Cutaneous Glands  All are exocrine glands  Exocrine Glands  Release secretions to surface via ducts  2 Groups: 1. Sweat Glands 2. Sebaceous Glands  Both formed by stratum basale and push into dermis Sweat Glands  More than 2.5 million per person  2 Primary Types  Eccrine Glands  Widely distributed in skin; abundant on palms, soles, and forehead  Sweat composition: mostly water with a slightly acidic 4-6 pH  Function: thermoregulation Sweat Glands  Apocrine Glands  Ducts empty into hair follicles  Found mainly in anogenital and axillary region  Begin to function at puberty due to hormones/pheromones  Organic contents: fatty acids and proteins – can have a yellowish color that stains clothes  Odor is from associated bacteria  Cerminous Glands  Modified apocrine gland  Found in outer 1/3 of ear canal  Produce ear wax to trap “invaders” Sebaceous (Oil) Glands  All over except palms and soles of feet  Produce oil for waterproofing  Lubricant for skin and kills bacteria  Most with ducts that empty into hair follicles  Some open onto skin surface in lips, eyelids, genitalia  Sebum (seb = grease)  Mixture of oily substances and fragmented cells  Glands are activated at puberty  stimulated by hormones