Skin Anatomy and Physiology for the Vet Tech – Flashcards
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Keratinocytes
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produce keratin, the tough, fibrous, waterproof protein that gives skin its resiliency and strength
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Melanocytes
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produce melanin pigment
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Merkel cells
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phagocytize microinvaders; macrophage specific to epidermis
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Langerhans cells
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found in stratum spinosum; may be involved in allergic and cell-mediated immune response in skin
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Stratum germinativum
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Deepest layer of epidermis: Consists of a single row of keratocytes attached to epithelial basement membrane Merkel cells, melanocytes, keratocytes, found in this layer
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Stratum spinosum
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(spiny layer of epidermis): Contains several layers of cells held together by desmosomes. Langerhans cells found in this layer
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Stratum granulosum
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(granular middle layer): Composed of two to four layers of flattened, diamond-shaped keratocytes that contain lamellated granules of glycolipids These glycolipids play a role in helping waterproof the skin and slowing water loss across the epidermis
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Stratum lucidum
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(clear layer): Found in very thick skin Composed of a few rows of flattened dead cells Contents of the keratogranules combine with intracellular tonofilaments to form keratin fibrils
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Stratum corneum
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(horny outermost layer of epidermis): Composed of 20 to 30 rows of keratocyte "remnants" Sometimes called horny or cornified cells
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Hairy skin usually consists of three epidermal layers rather than five ... What are they?
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stratum basale, stratum spinosum, and stratum corneum
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epidermal papilla
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A knoblike elevation that can be seen periodically in hairy skin. It is a tactile elevation that is usually associated with a tactile hair.
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Tylotrich hair
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A tactile hair associated with a tactile elevation called an epidermal papilla, found in hairy skin.
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Epidermis contains what 4 cell types?
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keratinocytes, melanocytes, Merkel cells, Langerhans cells
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The Epidermis can contain what 5 layers?
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Stratum germinativatum, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum,
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Skin consists of what three layers?
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Epidermis, Dermis, Hypodermis
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What is contained within the dermis?
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Dense irregular connective tissue: Collagen, elastic, and reticular fibers, hair follicles, nerve endings, glands, smooth muscle, blood vessels, lymphatics, fibroblasts, adipocytes, and macrophages.
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How many layers are in the Dermis, and what are they?
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TWO: Papillary and Reticular
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The first layer of the dermis is composed of what type of tissue?
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loose connective tissue with loosely woven fibers and ground substance
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Dermal papillae contain what? What is it's function?
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Contain: Blood vessels, pain, temperature, and touch receptors Function: helps cement the epidermis and the dermis together
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The second layer of the dermis is composed of what tissue?
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dense irregular connective tissue
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The hypodermis is composed of what tissue?
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areolar tissue
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What does the tissue of the hypodermis contain?
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adipose tissue (fat,_) blood and lymphatic vessels, and nerves
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What is the purpose of the hypodermal layer?
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It permits skin to move freely over underlying bone and muscle without putting tension on skin
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What is the special touch receptor in the hypodermis?
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the pacinian corpuscle - it is sensitive to heavier pressure than Meissner's corpuscle in the epidermis
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Pigmentation of the skin results from:
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presence or absence of melanin granules in the extensions of melanocytes
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What hormone controls the dispersion of melanin granules?
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Melanocyte-stimulating hormone
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What cells are responsible for arranging melanin on the side of the cell with the greatest sun exposure, and why?
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Keratocytes; to protect the cells from damaging UV rays
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What is the toughest and thickest skin in the body? How many epidermal layers does it have?
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Paw pads, All five epidermal layers
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What do paw pads consist of?
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Thick layers of fat and connective tissue with exocrine sweat glands and lamellar corpuscles
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What structures cover the entire surface of the paw pad?
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Conical papillae
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Planum Nasale
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top of the nose of cats, pigs, sheep and dogs
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Planum nasolabiale
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muzzle of cows and horses
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Which species have glandular planums?
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cows, pigs, sheep
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How many and which epidermal layers are present in the planums?
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Three: Germinativum, Spinosum, Corneum
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What is an ergot?
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A dark, horny structure found on the posterior ankles of any equine
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What is a chestnut?
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A dark, horny structure found on the medial knees or hocks of any equine
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Where are cutaneous pouches of sheep found?
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Infraorbitally, interdigitally, and inguinally
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What do cutaneous pouches in sheep do?
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They secrete a fatty yellow substance which covers and sticks to the skin when dry... from sebaceous and oil glands.
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What does hair do for an animal?
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Maintains body temperature, and provides camouflage
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Hair Bulb
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deepest part of the hair follicle
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Papilla (within a hair follicle)
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a mound of dermal cells from which the hair is derived
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What 3 different parts make up a hair?
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Shaft, Root, Follicle
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What 3 layers make up the root sheath?
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Connective tissue root sheath, External root sheath, Internal root sheath
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What 3 layers make up a hair strand?
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cuticle, cortex, medulla
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Root hair plexus
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web of sensory nerve endings (touch receptor)
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What are the 3 phases of hair growth?
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Anagen, Catagen, Telogen
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Anagen phase
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cells are added at the base of the root, hair lengthens
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Catagen phase
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period of transition between anagen and telogen phases
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Telogen phase
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maximum length of hair is achieved, hair stops growing, hair follicle shortens, and hair is held in a resting phase
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How many types of melanin do horses produce?
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one type
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What is the difference between gray hair and white hair?
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Gray hair has decreased amount of melanin, white hair has air in the medulla and NO pigment
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How many TYPES of hair are there? What are they?
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Three: Primary (guard); Secondary (wool); Tactile (sinus/Whiskers)
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Arrector Pili Muscle
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a small smooth muscle attached to each hair follicle that pulls the hair to an erect position when stimulated by the SYMPATHETIC nervous system
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How many glands are present in most animals' skin? What are they?
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Four: Sebaceous; Sweat (sudoriferous: eccrine and apocrine;) Tail; Anal
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Where are sebaceous glands located?
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In the dermis, with a single duct that empties either into a hair follicle (most,) or directly onto the surface of the skin.
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Sebum is made of
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glycerides and free fatty acids
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The purpose of sebum is to
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Coat the base of the hair and surrounding skin which helps to trap moisture, keeps hair soft, pliant, and somewhat waterproof; also reduces skin infections by creating a barrier.
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Eccrine Sweat glands:
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Excretory portion is located in the dermis or hypodermis; Empty onto surface of skin
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Apocrine Sweat Glands:
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Excretory portion buried in the dermis or hypodermis; Empty into hair follicles
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Tail glands consist of:
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Coarse, oily hairs and very large apocrine and sebaceous glands
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Tail gland purpose
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assists with recognition and identification of individual animals
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Anal Sacs are lined with which glands?
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sebaceous and apocrine glands
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Which digits are the dewclaws of cows, pigs, and sheep/goats?
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2nd and 5th digits
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Ungula
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another name for hoof
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Corium
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Tissue which is attached to the periosteum of the distal phalanx, on which rests the hoof
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The outer hoof is a modified version of what tissue?
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epidermis
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The corium is a modified version of what tissue?
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dermis
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Navicular bone
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the large distal sesamoid bone located proximally and posterior to the third phalanx
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Coffin bone
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The third phalanx
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What 3 parts is the equine hoof divided into?
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wall, sole, frog
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Digital Cushion
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a thick pad of fat and fibrous tissue lies beneath the sensitive frog
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The frog:
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Triangular horny structure located between the heels on the underside of the hoof
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Horns are derived from which layer of skin?
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Epidermis
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Horns are composed of:
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keratin
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The horn of an adult communicates directly with:
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the frontal sinus
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What are the 3 layers of the horn?
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corium, body, wall
