The Integumentary System Flashcards
Integument
One of the largest and most extensive organs in the body. Composed of all four tissues, covers and protects.
Integumentary system
Includes the skin, horns, hooves, claws, glands, and hair
Keratin
A fibrous protein forming the main structural constituent of hair, feathers, hoofs, claws, horns, etc.
Keratinization
Cells expire and in doing so form the vital protective barrier that helps enable an animal’s survival
Vitamin D
A group of fat-soluble secosteroids that play a crucial role in increasing the absorption of calcium, magnesium, and phosphate
Epidermis
Composed of keratinized stratified squamous epithelium and forms an outer waterproof shield, avascular (first layer of skin)
Dermis
Majority of skin, tough leathery layer made of dense fibroelastic connective tissue, vascular (second layer of skin)
Dermal papillae
The downwards folds of the epidermis interdigitate with the upward projections of the dermis, help cement the epidermis and the dermis together
Hypodermis or subcutaneous layer
A third layer of skin found below the dermis and is composed primarily of adipose tissue
Skin covered with fur usually consists of only three epidermal layers
Stratum basale, stratum spinosum, and stratum corneum
The stratum granulosum and stratum lucidum
Found in mammals without fur and are generally missing in the skin of furred animals
The implantation angle
Clusters of hair emerge from beneath scales and are directed away from the opening at an angle, tends to be low in smooth-coated animals and typically higher in longer-haired animals
Tactile elevations
Interspersed throughout the surface of the epidermis are knoblike elevations
Tylotrich hairs
When slightly moved, or brushed lightly against objects, the tactile elevation perceives the discrete movement and alerts the animal to the presence of a close object
Vibrissae
whiskers
Principle cells found in the epidermis
Keratinocytes (majority), melanocytes, merkel cells, and langerhans cells
Keratinocytes
Produces a tough, fibrous, waterproof protein called keratin that gives skin its resiliency and strength
Melanocyte
Produces pigment found in skin, found in the deepest epidermal layers
Melanin
A dark pigment stored in membrane-bound granules called melanosomes
Melanosomes
Transported to the tips of the cellular projections, where they are released into the intracellular space and ultimately absorbed by keratinocytes
Langerhans cell
A macrophage specific to the epidermis, originates in bone marrow and subsequently migrates to the skin, where it phagocytizes microinvaders and plays an important role in helping stimulate other aspects of the immune system
Merkel cells
Can be found in small numbers at the epidermal-dermal junction, where their half-dome shape partners with a half-domed sensory nerve ending
Merkel disc
Thought to aid in the sensation of touch
Squamous cell carcinoma
Deadly form of skin cancer, spreads rapidly to local lymph nodes and is aggressively invasive locally
5 layers of the epidermis
Stratum germinativum (stratum basale), stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum
Stratum germinativum (stratum basale)
The deepest layer of the epidermis, consists of a single row of keratinocytes that are firmly attached to the epithelial basement membrane & are actively engaged in cell division
Stratum spinosum
Second deepest layer, also known as spiny because when the cells of this epidermal layer are fixed for histologic examination, they contract into spiculated masses that resemble sea urchins, consists of several layers of cells that are held together by desmosomes
Stratum granulosum
Or granular layer, is the middle layer of skin. Composed of 2-4 layers of flattened, diamond-shaped keratinocytes
Stratum lucidum
Or clear layer, is found in only very thick skin, so most skin lacks this layer. Microscopically appears as a translucent layer composed of a few rows of flattened, dead cells
Stratum corneum
Or horny layer, is the outermost layer and dominates the epidermis. Constitutes up to 3/4 of the total epidermal thickness and is composed of 20-30 rows of keratinocytes
Pruritus
itchiness
Notoedres
The mite most commonly linked to mage in cats, rats, and rabbits
The dermis is composed of two layers:
The thin, superficial papillary layer and the thick, deeper reticular layer
The papillary layer
Lies just beneath the epithelial layer of the epidermis and is composed of loose connective tissue with loosely woven fibers and ground substance
Meissner’s corpuscle
Nerve endings or pain receptors found within the papillary layer, sensitive to light touch
Reticular layer
Under the papillary dermis, consists of dense, irregular connective tissue, accounts for 80% of the dermis
Hypodermis
A thick layer that resides below the dermis, important bc it permits the skin to move freely over underlying bone and muscle w/o putting tension on the skin
Pacinian corpuscle
Type of touch receptor cell present in the hypodermis, sensitive to heavier pressure
Pigmentation
Caused by the presence or absence of melanin granules in the armlike extensions of the melanocytes
Melanocyte-stimulating hormone (MSH)
Controls the dispersion of the granules in pigmentation
Hypophysis
Controls melanocyte-stimulating hormone (MSH)
Planum nasale
The top of the nose in cats, pigs, sheep, and dogs
Planum nasolabiale
Frequently referred to the nose in cows and horses and also called muzzle
Ergots and chestnuts
Dark, horny structures found on the legs of horses, ponies, and other members of the equine family
Chestnuts
Typically dark brown and are found on the inside of each leg at the carpus of the forearm and at the tarsus or hock of the hind leg
Ergots
Similar to chestnuts but are much smaller and are often overlooked, bc they are usually buried in the long caudal hairs of the fetlock
Cutaneous pouches
Infoldings of the skin found in sheep (front of eyes, btwn the digits above the hooves, and the groin)
Infraorbital pouch
Infoldings of the skin found in sheep located in front of the eyes
Interdigital pouch
Infoldings of the skin found in sheep located btwn the digits above the hooves
Inguinal pouches
Infoldings of the skin found in sheep located in the groin
Hair shaft
The part of hair that is visible above the skin
Root hair
The part of the hair buried within the skin
Hair follicle
Anchors hair
Hair bulb
Formed when the deepest part of the hair follicle expands
Papilla
A mound of dermal cells located at the base of the hair bulb
Matrix
Rapidly dividing epithelial cells covering the papilla
Root hair plexus
A web of sensory nerve endings that envelops the hair root
Compound follicles
Multiple hair strands emerge from a single epidermal orifice, although each strand has its own follicle and bulb
Primary hair
Also known as guard hair or cover hair in compound follicles, is usually surrounded by shorter secondary hairs
Secondary hairs
Also called satellite hairs in compound follicles
Hair is formed in three concentric layers:
Medulla, cortex, and cuticle
Medulla
The innermost layer and central core in hair
Cortex
Surrounds the medulla in the formation of hair, stiff and rigid due to being composed of hard keratin
Cuticle
Forms when a single layer of cells arise from the edge of the papilla in the formation of hair
Telogen effluvium
When bitches lose a large % of their total hair volume at once after whelping
Anagen phase
As more cells are added at the base of the root, the hair lengthens
Telogen phase
When the maximum length of hair is achieved, the hair stops growing, the hair follicle shortens, and the hair is held in a resting phase
Catgen phase
The period of transition btwn the anagen and telogen phases
Pheomelanin
Create yellowish and reddish colors in dogs
Tyrosine melanin
Create brown-black colors in dogs
Hair has been categorized into 3 broad groups
Primary/guard hairs, secondary/wool-type hairs, and tactile/sinus hairs
Primary hairs
Generally straight or arched and are thicker and longer than secondary hairs. The dominant hair in a complex hair follicle
Tactile hairs
Used as probes and feelers. Supplied w sensory endings that make them particularly sensitive to the slightest bending or touch
Implantation angle
The degree of erection in hair
Arrector pili muslce
Small smooth muscle attached to each hair follicle and is innervated by the sympathetic nervous system, makes animals hair stand when frightened
Sebum
White semiliquid mixture produced by sebaceous glands when they get too full and rupture
Lanolin
A substance produced by sebaceous glands in sheep
Sweat glands
Also called sudoriferous glands and are found over the entire body of most domestic species
Two types of sweat glands:
Eccrine and apocrine glands
Eccrine gland
Consists of a simple coiled tube located in the dermis or hypodermis, it is connected to the surface of the skin by a long duct
Apocrine sweat glands
Have a coiled, excretory portion buried in the dermis or hypodermis w a single excretory duct. Empty into hair follicles rather than onto the surface of the skin
Tail gland
Most felids (cats and canids (dogs) possess an oval region at the dorsal base of their tails
Anal sacs
Lined with sebaceous and apocrine glands and acts as a reservoir for the secretions that are produced from these glands
Ungula
Hoof
Ungulates
Hoofed animals
Corium
Both claws and hooves rest on underlying sensitive tissue
There are 5 types of corium in the equine foot:
Laminar, perioplic, coronary, sole, and frog
Laminar corium
Consists of primary and secondary lamina and is located btwn the hoof wall and the third phalanx, provides nutrients to the stratum internum
Laminitis
Serious condition in horses in which the laminar corium becomes inflamed
Perioplic corium
Located in the perioplic sulcus and supplies nutrients to the overlaying periople
Coronary corium
Found in the coronary sulcus and supplies nutrients to the stratum externum and stratum medium
Sole corium
Located superior to the sole and provides nutrients to the sole
Frog corium
Located superior to the frog and provides nutrients to the frog
Coronary band
The hoof grows from this downwardly
The skeletal foot of the horse includes:
distal part of
the second phalanx; the distal sesamoid bone, which is called the navicular bone; and the entire third phalanx, which is commonly known as the coffin bone
Laminae
The hoof and the corium form an elaborate array of interdigitations
Hoof wall
The laminae consist of primary and secondary extensions, which increase the contact area between the corium and this
The wall of the hoof is divided into 3 regions:
The toe (front of foot), the quarters (lateral aspects), and the heels (tapers downward and wraps around back of foot)
Horn tubes
Miniature vertical lines evident running from the coronary band to the ground
Sole
The plantar or palmar surface of the hoof, it is concave and fills the space bordered by the wall and the bars
Angle
The part of the sole that immediately surrounds the bars
White line
A thin strip formed at the junction of the sole and the hoof wall
Frog
Insensitive, triangular, horny structure located btwn the heels on the underside of the hoof
Central sulcus
A central depression which divides the frog
Collateral sulcus
The frog is separated from the bars on the lateral and medial sides by a deep, concave region
Digital cushion
A thick pad of fat and fibrous tissue, which lies beneath the sensitive frog
Lateral cartilages
Two large bands of cartilage extended proximally from the distal phalanx and form an important structural support for the equine foot
Horns
Like hooves, are epidermal in origin and are structurally similar to hair, composed of horny keratin
Polled breeds
Domestic animals that have been bred to be horn free
