Introduction to General Anatomy - Lecture Notes PDF

INTRODUCTION TO GENERAL ANATOMY Prepared by: Jian Midj A. Oco, PTRP Presented by: Oriel M. Repil, PTRP, MD, OHP  INTRODUCTION TO GENERAL ANATOMY A. Fundamental planes B. Anatomic position C. Anatomical terms D....

INTRODUCTION TO GENERAL ANATOMY Prepared by: Jian Midj A. Oco, PTRP Presented by: Oriel M. Repil, PTRP, MD, OHP  INTRODUCTION TO GENERAL ANATOMY A. Fundamental planes B. Anatomic position C. Anatomical terms D. Systems of the body E. Regions of the body F. Cavities of the body  ANATOMY- science of body structures and the relationships among them. (ana = up, -tomy = process of cutting) PHYSIOLOGY- science of body functions – how the body parts work.  PLANES AND SECTION Plane – is a geometrical concept referring to an imagined flat surface A. SAGITTAL/LONGITUDINAL PLANE – divides body into right and left portions a. Median plane/midsagittal plane – plane passes through the midline of the body/organ and divide it into equal right and left side b. Parasagittal plane – if sagittal plane does not pass through midline but instead divides the body/organ into unequal right and left side * Midline – imaginary vertical line that divide the body into equal right and left sides. B. FRONTAL/CORONAL PLANE – divides body into anterior and posterior portions C. TRANVERSE/HORIZONTAL PLANE – divides body into superior and inferior portions  PLANES AND SECTION Section – refers to a part cut in a plane o Transverse section/cross section – cross-wise o Oblique section – a transverse section cut at a diagonal angle o Longitudinal section - lengthwise ** these terms are useful only on limited circumstances, since they don’t really identify whether the cuts are made top to bottom, front to back or side to side.  ANATOMICAL POSITION Anatomical position – standard position of reference where descriptions of any region or part of the human body is assumed to be placed in. ✓The subject stands erect facing forward with the head level and the eyes facing forward. ✓The lower limbs are parallel and the feet are flat on the floor and directed forward, ✓And the upper limbs are at the sides with the palms facing forward  BODY POSITIONS Prone – lying face down/lying on your tummy Supine – lying face up/lying on your back R/L Lateral(side) recumbent(lying down) Sidelying – lying on one side Quarter prone Fetal position Trendelenburg – leg up Reverse Trendelenburg – head up Fowler’s- bet 45 to 60deg Semi fowler’s – bet 15 to 45deg  REGIONAL NAMES Principal regions that can be identified externally: 1. Head – skull (encloses and protects the face) and face (front portion of the head – eyes, nose, mouth, cheeks, chin) 2. Neck – supports the head and attaches it to the trunk 3. Trunk – body itself, consists of chest, abdomen and pelvis 4. Upper limb – attaches to the lateral trunk - armpit, shoulder to hand 5. Lower limb – attaches to the lower trunk – buttock, thigh to foot  DIRECTIONAL TERMS - words that describe the position of one body part relative to another DIRECTIONAL TERM DEFINITION EXAMPLE OF USE SUPERIOR/CEPHALIC/CRANIAL Towards the head, upper part The heart is superior to the liver INFERIOR/CAUDAL Away from the head, lower part The stomach is inferior to the lungs ANTERIOR/VENTRAL Nearer to or at front of body Sternum is anterior to the heart POSTERIOR/DORSAL Nearer to or at back of body Esophagus is posterior to the trachea MEDIAL Nearer to midline Ulna is medial to radius LATERAL Far away from midline Lungs are lateral to the heart INTERMEDIATE Between structures Transverse colon is intermediate to ascend and descend colon IPSILATERAL Same side of the body Gall bladder and ascending colon is ipsilateral CONTRALATERAL Opposite side of the body Ascending and descending colon are contralateral PROXIMAL Near to the origin of structure The humerus is proximal to the radius DISTAL Far from the origin of structure Phalanges are distal to carpals SUPERFICIAL/EXTERNAL Towards or on surface of the body Ribs are superficial to lungs DEEP/ INTERNAL Away from surface of the body Ribs are deep to the skin of chest and back  ANATOMICAL TERMS FRONT ANTERIOR HEAD CEPHALIC SKULL CRANIAL/CRANIUM FACE FACIAL NECK/NAPE CERVICAL FOREHEAD FRONTAL TEMPLE TEMPORAL EYE ORBITAL/OCULAR EAR OTIC CHEEK BUCCAL NOSE NASAL MOUTH ORAL CHIN MENTAL  ANATOMICAL TERMS FRONT ANTERIOR ARMPIT AXILLARY ARM BRACHIAL FRONT OF ELBOW ANTECUBITAL FOREARM ANTEBRACHIAL WRIST CARPAL PALM PALMAR/VOLAR FINGERS PHALANGES/PHALANX/DIGITS/DIGITAL CHEST THORACIC ABDOMEN ABDOMINAL BREASTBONE STERNUM BREAST MAMMARY NAVEL UMBILICUS HAND/THUMB MANUAL/POLLEX  ANATOMICAL TERMS FRONT ANTERIOR PELVIS PELVIC PUBIS PUBIC GROIN INGUINAL HIP COXAL THIGH FEMORAL LEG CRURAL KNEECAP PATELLA ANKLE TARSAL TOES PHALANGES/PHALANX/DIGIT/DIGITAL FOOT PEDAL TOP OF FOOT DORSUM GREAT TOE HALLUX  ANATOMICAL TERMS BACK POSTERIOR Base of skull Occipital Shoulder blade Scapula Spinal column/spine Vertebral Back Dorsal Elbow Olecranon Loin/lowback Lumbar Between hips/tailbone Sacrum/coccyx Buttocks Gluteal Anus/external genitalia Perineal/perineum Hollow behind knee Popliteal Calf Sural Sole Plantar heel Calcaneal  INTEGUMENTARY SYSTEM Components: skin and associated structures, such as hair, fingernails/toenails, sweat and oil glands Functions: - protects body - helps regulate body temperature - Eliminates some wastes - Helps make vitamin D - Detects sensation: touch, pain, warmth, cold - Stores fat and provides insulation  SKELETAL SYSTEM Components: bones and joints and their associated cartilages Functions: - Supports and protects body - Provides surface area for muscle attachments - Aids body movements - Houses cells that produce blood cells - Stores minerals and lipids  MUSCULAR SYSTEM Components: skeletal muscle tissue – muscles that area usually attached to the bones (others are smooth and cardiac ms) Functions: - Participates in body movement (walk, run, etc.) - Maintains posture - Produces heat  NERVOUS SYSTEM Components: brain, spinal cord, nerves and special sense organs: eyes, ears Functions: - Generates action potentials (nerve impulses) to regulate body activities - Detects changes in body’s internal and external environments - Interprets changes - Responds by causing muscular contractions or glandular secretions  ENDOCRINE SYSTEM Components: hormone-producing glands (pineal gland, hypothalamus, pituitary gland, etc.) and hormone-producing cells in several other organs Functions: - Regulates body activities by releasing hormones (chemical messengers transported in blood from endocrine gland to tissue to target organ)  CARDIOVASCULAR SYSTEM Components: blood, heart, blood vessels (veins, arteries, capillaries) Functions: - Heart pumps blood through blood vessels - Blood carries oxygen and nutrients to cells and carbon dioxide and wastes away from cells and helps regulate acid-base balance, temperature and water content of body fluids - Blood components help defend against disease and repair damaged blood vessels  LYMPHATIC SYSTEM AND IMMUNITY Components: lymphatic fluid and vessels: spleen, thymus, lymph nodes, tonsils. Cells that carry out immune responses (T-cells, B-cells and others) Functions: - Returns proteins and fluid to blood - carries lipids from gastrointestinal tract to blood - Contains sites of maturation and proliferation of B-cells and T cells that protect against disease-causing microbes  RESPIRATORY SYSTEM Components: lungs and airway passages such as pharynx, larynx, trachea, bronchial tubes leading into and out of the lungs Functions: - Transfers oxygen from inhaled air to blood and carbon dioxide from blood to exhaled air - Helps regulate acid-base balance of the body fluids ** - Air flowing out of lungs through vocal cords produces sounds  DIGESTIVE SYSTEM Components: GI tract: mouth, pharynx, esophagus, stomach, small and large intestines, anus; also includes accessory organs that assist in digestion: salivary glands, liver, gall bladder and pancreas Functions: - Achieves physical and chemical breakdown of food - Absorbs nutrients - Eliminates solid wastes  URINARY SYSTEM Components: kidneys, ureters, urinary bladder, urethra Functions: - Produces, stores and eliminates urine - Eliminates wastes and regulates volume and chemical composition of blood - Helps maintain the acid-base balance of the body fluids ** - Maintains body’s mineral balance - Helps regulate production of red blood cells  REPRODUCTIVE SYSTEM Components: FEMALE: gonads (ovaries), uterine tubes/fallopian tubes, uterus, vagina, mammary glands. MALE: gonads(testes), epididymis, ductus/vas deferens, seminal vesicles, prostate, penis Functions: - Gonads produce gametes (sperm, oocytes) that unite to form new organism - Gonads also release hormones that regulate reproduction and other body processes - Associated organs transport and store gametes - Mammary glands produce milk  CAVITIES OF THE BODY Body cavities- spaces that enclose internal organs Cranial cavity Formed by cranial bones and brain Vertebral cavity Formed by vertebral column and contains spinal cord and the beginnings of spinal nerves Thoracic cavity Chest cavity; contains pleural and pericardial cavities and the mediastinum Pleural cavity A potential space between the layers of the pericardium that surrounds a lung Pericardial cavity A potential space between the layers of the pericardium that surrounds the heart Mediastinum Central portion of thoracic cavity between the lungs; extends from sternum to vertebral column, and from 1st rib to diaphragm; contains heart, thymus, esophagus, trachea, and several large vessels Abdominopelvic cavity Subdivided into abdominal and pelvic cavity Abdominal cavity Contains stomach, liver, spleen, liver, gallbladder, small and most of the large intestine; serous membrane of the abdominal cavity is peritoneum Pelvic cavity Contains urinary bladder, portions of large intestines, internal organs for reproduction REGIONS OF THE BODY Hypochondriac – below (rib) cartilage Epigastric – near the stomach Hypogastric – below the stomach Lumbar – lumbar vertebrae in lowback Iliac – ilium, bowl-like part of pelvic bone  REGIONS/QUADRANTS OF THE BODY 9 abdominopelvic region – 2 horizontal planes (1 below the ribs, the other just above the hip bones), 2 sagittal planes (each just medial to a nipple)  CLINICAL SIGNIFICANCE Medical Imaging - refers to techniques and procedures used to create images of the human body. - Allows visualization of internal structures to diagnose abnormal anatomy and deviations from normal physiology  - single barrage of x-rays passes -Inexpensive, quick, simple to through the body, producing an perform. image of interior structures on x- -dense structures: bones are white ray films. -hollow structures: lungs are black Radiography - 2-dimensional image -intermediate density: skin, fat, muscle are grey - Low dose x-ray for: examining soft tissues(mammography), determining bone density (bone densitometry)  5 basic radiography densities – Air density Bowel gas – Fat density Flank stripe – Soft tissue density liver – Bone density pelvis – Metal/contrast density barium  - Exposing to a high-energy - Safe but cannot be use on magnetic field. patients with metal implants - Results in a 2 or 3 dimensional - Shows fine details for soft tissues Magnetic Resonance Imaging blue print of cellular chemistry but not for bones (MRI) - Most useful for differentiating ~ an hour or longer, depending if normal and abnormal tissues you need contrast dye - Detects tumors, plaques, brain abnormalities, measure blood flow, and variety of system/organ disorders  - Computer assisted radiography - Visualizes soft tissues and organs - X-ray beam traces an arc at with much more detail. Computed Tomography (CT) multiple angles around section of - 3 dimensional views ~ 10 mins the body - Whole body CT targets torso, - Transverse section of the body, most beneficial in screening for CT scan lung cancers, coronary artery disease, and kidney cancers  - High frequency sound waves - safe, non-invasive, painless, uses - The image, which may be still or no dyes Ultrasound Scanning moving is called sonogram - Most commonly used to visualize fetus in pregnancy. - Doppler ultrasound used to observe the size, location and actions of organs and blood flow through blood vessels. INTEGUMENTARY SYSTEM  INTEGUMENTARY SYSTEM A. Overview B. Skin layers a. Epidermis b. Dermis c. Subcutaneous C. Skin appendages a. Hair b. Glands c. Nails D. Clinical significance  FUNCTIONS OF INTEGUMENTARY SYSTEM 1. Regulates body temperature/thermoregulation 2. Stores blood/blood reservoir 3. Protects body from external environment 4. Detects cutaneous sensations 5. Excretes and absorbs substances 6. Synthesis of vitamin D  THERMOREGULATION By liberating sweats at its surface and by adjusting the flow of blood in dermis During high environmental temp/heat produced by exercise, sweat production increases; the evaporation of sweat from skin surface lowers the body temp. In addition, blood vessels in the dermis dilate, causing more blood to flow to the dermis, which increases the amount of heat loss. In low environmental temp, sweat production is decreased, which conserves heat, blood vessels constrict, decreasing blood supply to the skin and reduces heat loss from the body. Skeletal muscle contraction generate body heat. The normal body temperature range is 36.5°C to 37.5°C  BLOOD RESERVOIR The dermis houses an extensive network of blood vessels that carry 8-10% of the total blood flow in a resting adult  PROTECTION Keratin – (protein inside cell) protects from microbes, abrasion, heat and chemicals. Lipids – inhibits evaporation of water from skin, guarding dehydration, also retard entry of water across skin surface (swimming, showers) Oily sebum – keeps the skin and hair from drying out and contains bactericidal chemicals Melanin – shield against the damaging effects of UV light 2 types of cells carry out protective functions: o Intraepidermal macrophages alert the immune system to the presence of potentially harmful microbial invaders by recognizing and processing them o Dermis macrophages phagocytise (ingest) bacteria and viruses that manage to bypass the intraepidermal macrophages of the epidermis  CUTANEOUS SENSATION are sensations that arise in the skin including tactile sensations: Merkel’s disk light touch Meissner’s corpuscles low-frequency vibrations and fine touch Pacinian corpuscles deep pressure and high-frequency vibrations Ruffini endings skin stretch, joint activity and warmth Krause end bulb coolness/cold  EXCRETION AND ABSORPTION Excretion small role in elimination of substance in the body Absorption the passage of materials from the external environment into body cells Waterproof nature of stratum corneum, about 400mL of water evaporates through it daily. (additional 200mL –sendentary, more if physically active)  SYNTHESIS OF VITAMIN D - requires activation of a precursor molecule in the skin by ultraviolet rays in sunlight. - Only a small amount of exposure to UV light (about 10-15 mins atleast 2x a week) is required for Vit D synthesis - Vit D is believed to enhance phagocytic activity, increase the production of antimicrobial substances in phagocytes, regulate immune functions and help reduce inflammation.  INTEGUMENTARY SYSTEM SKIN - aka cutaneous membrane - Covers the external surface of the body - Largest organ of the body in weight - In adult, skin covers an area of 2 sqm and weighs 4.5-5kg, about 7% of TBW - Thickness: - 0.5mm/0.02in on eyelids to 4.0mm/0.16in on heels - 2 main parts: Superficial thinner portion, composed of epithelial tissue, EPIDERMIS (avascular) Deeper, thicker connective tissue, DERMIS (vascular) - Deep to dermis, but not part of the skin, is the SUBCUTANEOUS LAYER/subQ aka HYPODERMIS, consists of adipose and areolar tissues - Storage depot for fat and contains large blood vessels that supply the skin - Contains nerve endings (sometimes with dermis) called lamellated corpuscles or Pacinian corpuscles that are sensitive to pressure.  INTEGUMENTARY SYSTEM - 2 main parts: Superficial thinner portion, composed of epithelial tissue, EPIDERMIS (avascular) Deeper, thicker connective tissue, DERMIS (vascular) - Deep to dermis, but not part of the skin, is the SUBCUTANEOUS LAYER/subQ aka HYPODERMIS, consists of adipose and areolar tissues - Storage depot for fat and contains large blood vessels that supply the skin - Contains nerve endings (sometimes with dermis) called lamellated corpuscles or Pacinian corpuscles that are sensitive to pressure.  EPIDERMIS Outer and most superficial layer Desquamation/exfoliation Keratinocytes – epidermal cells that produces keratin (tough fibrous protein that protects the skin) and lamellar granules which release a water repellent sealant that decreases water entry and loss and inhibit entry of foreign materials. Contains melanocytes – produces melanin for skin color and absorbing damaging UV lights Intraepidermal macrophages/ Langerhans cells – immune responses Tactile epithelial cells – function in sensation of touch  5 LAYERS OF EPIDERMIS STRATUM DESCRIPTION Deepest layer, composed of single row of cuboidal or columnar keratinocytes that contain scattered keratin intermediate filaments Basale Stem cells undergo cell division to produce new keratinocytes Melanocytes and tactile epithelial cells associated with tactile discs are scattered among keratinocytes Spinosum 8-10 rows of many-sided keratinocytes with bundles of keratin intermediate filaments Contains projections of melanocytes and intraepidermal macrophages (immune responses) Granulosum 3-5 rows of flattened keratinocytes, which organelles are beginning to degenerate Contains protein keratohyalin (converts keratin intermediate filaments into keratin) and lamellar granules (release lipid-rich, water repellent secretion) Lucidum 4-6 rows of clear, flat, dead keratinocytes with large amount of keratin Present only in skin of fingertips, palms and soles Corneum Few to fifty or more rows of dead, flat keratinocytes that mostly contains keratin  Second, deeper part of the skin DERMIS Has the ability to stretch and recoil easily Much thicker than epidermis Contains blood vessels, nerves, glands and hair follicles Dermis is essential in survival of epidermis due to its function and structure Divided into thin papillary region and thick deeper reticular region: REGION DESCRIPTION Papillary Superficial portion of dermis (1/5) Consists of areolar connective tissue with thin collagen and fine elastic fibers Contains epidermal ridges that house blood capillaries, corpuscle of touch, and free nerve endings (painful stimuli) – fingerprints/footprints Reticular Deeper portion of dermis (4/5) Consists of dense irregular connective tissue with bundles of thick collagen and some coarse elastic fibers Spaces between fibers contain some adipose cells, hair follicles, nerves, sebaceous glands (sebum/moisture), and sudoriferous glands (sweat gland)  ACCESSORY STRUCTURES OF SKIN 1. HAIR/PILI Present in most skin surface except palm, plantar aspect of feet, lips In adults, it is mostly distributer across scalp, eyebrows, axillae, and around external genitalia. ** nostrils, external ear canal Functions in sensing light touch due to touch receptors/hair root plexuses o Shaft – superficial portion of hair, projects above the skin o Root – deep to the shaft that penetrates into the dermis sometimes subcutaneous layer. o Hair follicle – surrounding root of the hair, made up of external and internal root sheath called epithelial root sheath ERS – downward continuation of epidermis IRS – forms a cellular tubular sheath of epithelium between the ERS and the hair o Dermal root sheath – dense dermis surrounding hair follicle  o Bulb – base of each hair follicle and its surrounding dermal root sheath is an onion- shaped structure o Papilla of the hair – structured houses a nipple-shaped indentation o Hair matrix – germinal layer of cells of the bulb Arrector pili – smooth muscle that causes ‘goose bump/gooseflesh’ when under physiological or emotional stress Hair root plexus – are dendrites of neuron that surrounds the hair follicle, which is sensitive to light touch ✓ Lanugo – fine, non pigmented downy hairs that covers the body of fetus that usually develops within 5th month ✓ Terminal hairs – long, coarse heavily pigmented hair that replaces the lanugo of the eyebrows, eyelash, and scalp prior to birth ✓ Vellus hair – the lanugo of the rest of the body  ACCESSORY STRUCTURES OF SKIN 2. SKIN GLANDS ❑Sebaceous glands/oil glands – simple, branched acinar(rounded) gland The secreting portion of a sebaceous gland lies in the dermis and usually opens into the neck of hair follicle, in some locations, such as lips, glans penis, labia minora and tarsal glands of the eyelids. Absent on palms and sole Small on most areas of trunk and limbs, large on skin of breast, face, neck and superior chest Secretes an oily substance called sebum, a mixture of triglycerides, cholesterol, proteins and inorganic salts. Sebum coats surface of hair and helps keep them from drying and becoming brittle, also prevents excessive evaporation of water from skin, keeping it soft and pliable(flexible), and inhibits growth of bacteria ❑Sudoriferous gland/sweat gland – 3-4 million in the body 2 main parts: Eccrine sweat glands (secretes outwardly) – simple, coiled tubular glands, more common Usually found in skin of forehead, palms and soles. Not present in margin of lips, nail beds of fingers and toes, glans penis, glans clitoris, labia minora, or eardrums. The secretory portion is located mostly on deep dermis, sometimes upper subcutaneous layer. Sweat (600mL/day) consists primarily of water with small amounts of ions (Na+ and Cl-), urea, uric acid, ammonia, amino acids, glucose and lactic acid. Main function: help regulate body temperature by evaporation Thermoregulation – homeostatic regulation of the body Thermoregulatory sweating – the role of eccrine gland in helping the body in thermoregulation Insensible perspiration – sweat that evaporates from the skin before it is perceived as moisture Sensible perspiration – sweat that is excreted in larger amounts and is seen as moisture on the skin Emotional sweating/cold sweat – sweat in response to an emotional stress such as fear or embarassment  Apocrine sweat glands – simple, coiled tubular glands but have larger ducts and lumen found mainly in skin of axilla, groin, areola of the breast, bearded regions of the face in adult male. The secretory portion is located in the lower dermis or upper subcutaneous layer and the excretory duct opens into hair follicles. Appears milky or yellowish in color but odorless. (sweat interacts with bacteria on surface of skin causes musky odor/body odor) Has same component as eccrine plus lipids and protein *** eccrine glands functions soon after birth, apocrine does not function until puberty. Apocrine and eccrine glands are both active in emotional sweating Apocrine glands secrete sweat during sexual activities (*pheromones) Eccrine glands are not active during thermoregulatory sweating.  Ceruminous glands – modified sweat glands on the external ear that produces a waxy lubricating secretion Secretory glands lie in the subcutaneous layer, deep to sebaceous gland Excretory ducts open either onto the surface of ear canal or into ducts tof sebaceous glands. Cerumen – a yellowish material, combined secretion of ceruminous and sebaceous glands.  ACCESSORY STRUCTURES OF SKIN 3. NAILS – plates of tightly packed, hard, dead, keratinized epidermal cells that form a clear, solid, covering over the dorsal surfaces of the distal portions of the digits. Nail body/plate – visible portion of nail Free edge – part of nail body that may extend past the distal end of digit Nail root – portion of nail that is buried in a fold of skin Lunula – white, crescent-shaped area of proximal end of the nail body Hyponychium – thickened region of stratum corneum beneath the free edge Nail bed – skin below the nail plate Eponychium/cuticle – proximal border of the nail and consists of stratum corneum of epidermis  CLINICAL SIGNIFICANCE Assessment and diagnosis Skin cancer : ABCDE (assymmetry, border, color, diameter, evolving) used for early warning signs of malignant melanoma Burn- - tissue damage caused by excessive heat, electricity, radioactive, friction or corrosive chemicals that breakdown proteins on skin. o 1st degree – epidermis, with mild pain and erythema but no blisters. May heal 3-6 days with peeling or flaking (ex. Mild sunburn) o 2nd degree – destroys epidermis and part of dermis, some skin function is lost. (+)redness, blister formation, edema, pain. If no infection, may heal 3-4 weeks but with scarring. ** 1st and 2nd degree burns are considered PARTIAL THICKNESS BURN o 3rd degree burn/FULL THICKNESS BURN – destroys epidermis, dermis and subcutaneous layer, may appear marble-white to mahogany colored to charred dry wound. (+) edema, numbed burned area d/t sensory damage. Skin grafting may be required to promote healing and minimize scarring.  RULE OF NINES Major burn – 3rd degree burn over 10% of body surface area 2nd degree burn over 25% of BSA 3rd degree burn on the face, hands, feet, or perineum When burn area exceeds 70%, more than half the victims die  CLINICAL SIGNIFICANCE Pressure ulcers/decubitus ulcers/bedsores – constant deficiency of blood flow to tissues Typically affects tissues that overlies a bony projection that has been subjected to prolonged pressure against an object such as bed, cast, or splint. Abrasion – skin has been scraped away Blister – collection of serous fluid within epidermis or between epidermis and dermis. (bullae – large blister) Callus – hardened, thickened skin on hand or soles d/t persistent pressure and friction Cold sore – lesion caused by HIV Contact dermatitis – inflammation of skin caused by exposure to chemicals Contusion – tissue deep to the skin is damaged but epidermis is not broken Cyst – a sac with a distinct connective tissue wall, containing a fluid or other material Eczema – inflammation of skin characterized by patches of red, blistering, dry and extremely itchy skin. The cause is unknown but is linked to genetics and allergies.  CLINICAL SIGNIFICANCE Frostbite – local destruction of skin and subcutaneous tissue on exposed surface as a result of extreme cold. Hives/urticaria – reddened elevated patches of skin that are often itchy. Caused by infection, emotional stress. Food allergies, etc. Keloid – elevated, irregular darkened area of excess scar tissue caused by collagen formation during healing Laceration – irregular tear of the skin Psoriasis – common and chronic skin disorder in which keratinocytes divide and move more quickly than normal from basale to corneum, resulting to incomplete cycle and immature shed surface cells. Warts – mass produced by uncontrolled growth of epithelial skin cells caused by papillomavirus, most are non cancerous. QUESTIONS? Thank you for listening!