Integumentary System PDF

Integumentary system  The Integumentary System Integument is skin Skin and its appendages make up the integumentary system A fatty layer (hypodermis) lies deep to it Skin is an organ because it consists of different tissues – largest organ in the body Dermatolog...

Integumentary system  The Integumentary System Integument is skin Skin and its appendages make up the integumentary system A fatty layer (hypodermis) lies deep to it Skin is an organ because it consists of different tissues – largest organ in the body Dermatology is the medical specialty concerning the diagnosing and treatment of skin disorders  Functions of skin Protection – Cushions and insulates and is waterproof – Protects from chemicals, heat, cold, bacteria – Screens UV rays Synthesizes vitamin D with UV rays Regulates body temperature – during high temperature or strenuous exercise sweat is evaporated from the skin surface to cool it down. – vasodilation (increases blood flow) and vasoconstriction (decrease in blood flow) regulates body temp  Functions of skin Prevents unnecessary water loss Sensory reception - nerve endings and receptor cells that detect stimuli to temperature, pain, pressure and touch Excretion - sweat removes water and small amounts of salt, uric acid and ammonia from the body surface Blood reservoir - dermis houses an extensive network of blood vessels carrying 8-10% of total blood flow in a resting adult  Types of skin Thick skin and thin skin Most of the body is made up of thin skin Thick skin is nonhairy, found on the palm region of the hand and sole of the foot Thick and thin skins are due to the thickness of the epidermis Layers of skin – Epidermis – Dermis  Epidermis Consists of stratified squamous keratinized epithelium Contains cells called keratinocytes Also contains special cells like – Melanocytes - make skin pigment melanin – Merkel cells – associated with sensory nerve endings – Langerhans cells – macrophage-like dendritic cells Layers of epidermis (from deep to superficial) – Stratum basale or germinativum – Stratum spinosum – Stratum granulosum – Stratum lucidum – Stratum corneum Epidermis and dermis of (a) thick skin and (b) thin skin Thick skin – skin (slide 45) Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale Dermis  Stratum basale (germinativum) Deepest layer Contains single layer of columnar or cuboidal shaped keratinocytes which lie on the basement membrane Cells divide and push already formed cells into higher layers As the cells move into the higher layers, they flatten and eventually die Melanocytes and Merkel cells are also located at stratum basale  Melanocytes are responsible for synthesis and release of brown pigment melanin – Melanin transported along dendrites of the melanocytes to keratinocytes – Melanin accumulates on the superficial aspect of the keratinocyte shielding its nucleus from harmful UV light – lack of melanin: albino/albinism (pale skin, light blonde, brown or reddish hair, irises that are pink, light blue, green or light brown, vision problems (nystagmus, strabismus, sensitivity to light) Merkel cells are specialized touch receptors - make contact with a sensory neuron ending  Stratum spinosum: Contains 8-10 layers of polyhedral cells (with many sides) Cells are often separated by narrow, translucent clefts The cells have numerous spine- like (prickle) cytoplasmatic extensions These spines of one cell are connected that of neighboring cells by desmosomes The cells produce a protein called cytokeratin Also has Langerhans cell, which functions as a macrophage by engulfing bacteria, foreign particles, and damaged cells that occur in this layer  The stratum granulosum The cells becomes flat (3 to 5 layers) and accumulate many large, basophilic keratohyaline grannules The nuclei and other cellular organs begin to disintegrate and cells begin to die  Stratum The stratum lucidum (clear Lucidum layer) Consists of several layers of clear flat dead cells Faint nuclear outlines are visible in only a few of the cells The keratinocytes of the stratum lucidum do not have distinct boundaries and are filled with protein eleidin, an intermediate form of keratin This layer is present only in the thick skin  Stratum corneum Stratum Corneum Cells are keratinized (filled with keratin) and form a layer that is about 30 cells thick Individual cells are difficult to observe because – nuclei can no longer be identified – the cells are very flat – the space between the cells has been filled with lipids, which cement the cells together into a continuous membrane Most superficial part of this layer has somewhat looser appearance Cells are constantly shed from this part of the stratum corneum - dandruff and flakes This layer makes up three fourths of the epidermal thickness Protection of the body by the epidermis is due to the functional features of the stratum corneum  Dermis Strong, flexible connective tissue layer Cells: fibroblasts, macrophages, mast cells, WBCs Fiber types: collagen, elastic, reticular Rich supply of nerves and vessels Critical role in temperature regulation (the vessels) Dermis of thick skin contains sweat glands Dermis of thin skin contains sweat glands, sebaceous glands, hair follicles and arrector pili muscles Two layers – Papillary – Reticular  Papillary layer: Forms 1/5 of dermis – loose areolar connective tissue Highly vascular Forms dermal papillae - fingerprints Reticular (net) layer: Dense irregular connective tissue Has – Sebaceous (oil) glands (in thin skin) – Arrector pili muscles (in thin skin) – Hair follicles (in thin skin) – Sudoriferous (sweat) glands – Meissner’s corpuscles (fine touch, discriminative touch, vibration) and Pacinian corpuscles (vibration and pressure)  Thin skin - scalp (slide 48) Epidermis Arrector pili muscle Sebaceous gland Dermis Hair follicle Sweat gland Thin skin-scalp (slide 48) Arrector pili muscle Sebaceous gland Hair follicle Sweat gland  Hypodermis “Hypodermis” (Gk) = below the skin “Subcutaneous” (Latin) = below the skin Also called “superficial fascia” Fatty tissue which stores fat and anchors skin (areolar tissue and adipose cells)  Skin appendages Derived from epidermis but extend into dermis Include – Hair and hair follicles – Sebaceous (oil) glands – Sweat (sudoiferous) glands – Nails  Nails Made of hard, flexible plates of keratin Proximal part is called root of the nail and covered by fold of skin Keratinized nail plate is bound to a bed of epidermis called the nail bed Nail plate grows from nail matrix Cells of nail matrix divide, move distally and become keratinized, form the nail root which matures as nail plate  Hair is absent in the region of palm, sole, lips, nipple, external genitalia (glans Hair (pili) penis, clitoris and labia minora) Composed of dead columns of keratinized cells – has 2 parts - shaft: is the superficial portion of hair - root: below the surface in the dermis Shaft and root are composed of three layers: medulla, cortex (with keratin and pigments) and outer cuticle  Hair The root of a hair is situated in an epidermal tube known as the hair follicle, extending into the dermis The hair follicle is dilated at its base to form the hair bulb The dermal papilla invigilates into the bulb which contains blood capillaries Arrector pili muscle extends from the deep part of the hair follicle to the papillary layer of the dermis Muscle is supplied by the sympathetic nerves and makes the hair erect on contraction.  Sebaceous (oil) glands Found in the dermis of thin skin Opens into the upper portion of hair follicle Produce sebum by holocrine secretion (entire secreting cell forms a part of secretion) Oils and lubricates  Sweat glands Found in the entire skin surface except nipples and part of external genitalia Prevent overheating Sweat is produced in response to stress as well as heat Has acinus lined by columnar cells  Types of sweat glands Eccrine or merocrine – Most numerous – True sweat: 99% water, some salts, traces of waste – Open through pores Apocrine – Axillary, anal and genital areas only – Ducts open into hair follices – Organic molecules in it decompose with time - odor Modified apocrine glands – Ceruminous – secrete earwax – Mammary gland – secrete milk  BURNS A burn is an injury to the skin or other organic tissue primarily caused by heat or due to radiation, radioactivity, electricity, friction or contact with chemicals. TYPES OF BURNS Thermal Burns Radiation Burns Chemical Burns Electrical Burns  CLASSIFICATION OF BURNS First Degree Burns (superficial) Only affects outer layer of skin, epidermis. Dry with blanchable redness. Second Degree Burns (partial thickness) Affects epidermis and dermis of skin. Painful blisters. Red, moist, shiny, fluid filled vesicles.  Third Degree Burns (full thickness) Destroys all layers of the skin. Damages nerve endings. Damages subcutaneous tissues. Dry waxy white, leathery, or charred black color, non-blanchable. Fourth Degree Burns (full thickness) Deepest and most severe. Destroys all layers of skin as well as bones, muscles and tendons. No pain.  RULE OF NINES The rule of nines gives an idea of how much of your total body’s surface area (TBSA) a burn takes up. It divides the body’s surface area up into percentages. It is used for the initial management of resuscitation in burn patients. The percentage of the TBSA burnt is used in the Parkland Formula to calculate the fluid requirements for burn patients in a 24-hour period. Usually used for 2nd, 3rd and 4th degree burns. QUESTION: Patient suffered a burn injury that left the Right anterior thigh, the entire left lower extremity and the anterior right upper arm with second degree burns. Estimate the percentage of the body burnt. ANSWER: Right anterior thigh = 4.5% Entire left lower extremity = 18% Anterior right upper arm = 2.3% % TBSA Burnt = 4.5% + 18% + 2.3% = 24.8% OR ~25%  Rule of nines for children: 9% each arm, 14% each leg, 18% for head, 18% for front torso, 18% for back torso Children’s have a larger TBSA relative to weight and may require larger fluid volumes. Parkland Formula Total crystalloid fluid (usually isotonic) over the first 24 hours = 4mls x %TBSA burnt x body weight (kg) First 8hrs = administer ½ fluid volume Next 16hrs = administer remaining ½ fluid volume