the integument

  1. The integumentary System includes
    skin and related structures such as hair, hooves, horns, claws, skin related glands
  2. layers of the integument
    • epidermis
    • dermis
    • hypodermis
  3. Epidermis
    • cell types:
    • keratinocytes - produce kerating, the tough fibrous, water proof protein that gives skin its resiliency and strength
    • Melanocytes - produce the pigment melanin
    • Merkel cells - phagocytize microinvaders; macrophage specific to epidermis
    • Langerhans cells - found in the stratum spinosum; may be involved in allergic and cell mediated immune response to skin
  4. Epidermal layers
    • stratum germinatium or basale
    • stratum spinosumer or spiny
    • stratum granulosum or granular
    • stratum lucidum or clear
    • stratum corneum or horny
  5. Stratum Germinatium or basale
    • basal layer
    • deepest layer
    • consists of a single row of keratinocytes attatched to the epithelial basement membrane
    • Merkel cells, melanocytes and keratinocytes are found in this layer
  6. Stratum Spinosum or spiny
    • contains several layers of cells held together by desmosomes
    • langerhans cells are found in this layer, where their slender projections form a weblike frame around the keratinocytes
  7. Stratum Granulosum or granular
    • composed of 2-4 layers of flattened diamond shaped keratinocytes that contain lamallated granules of glycolipids
    • these glycolipids play a role in helping to waterproof the skin and slowing water loss
  8. Stratum Lucidum or clear
    • 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
  9. Stratum Corneum or horny
    • composed of 20-30 rows of keratinocytes "remnants"
    • sometimes called horny or cornified cells
  10. Epidermis of hairy skin
    • hairy skin usually consists of 3 epidermal layers rather than 5
    • stratum basale
    • stratum spinosum
    • stratum corneum
    • the surface of hairy skin is covered in sale like folds
    • a knoblike elevation can be seen periodically; tactile elevation or epidermal papilla, usually associated with a tactile hair
  11. Dermis
    • composed of dense irregular conn tissue with collagen, elastic and reticular fibers
    • also includes hair follicles, nerve endings, glands, smooth muscle, blood vessels and lymphatic channels
    • fibroblasts, adipocytes and macrophages are also present
  12. Dermal layers
    • Papillary Layer
    • reticular layer
  13. Papillary layer
    • underneath the epithelial layer of the epidermis
    • composed of loose conn tissue with loosely woven fibers and ground substance
    • dermal papillae help cement the epidermis and dermis together (little bumps that pop up)
    • blood vessels, pain, temp, and touch receptors also present
  14. Reticular layer
    • consists of dense irregular conn tissue
    • bundles of collagen fibers from papillary layer blend into those of the reticular layer
    • separations between bundles represent tension lines in the skin
    • in areas where a great deal of bending occurs, dermal folds or flexure lines are present
  15. Hypodermis
    • composed of areolar tissue containing adipose tissue, blood and lymphatic vessels and nerves
    • contains special touch receptors called the pacinian corpuscle which is sensitive to heavier pressure than meissners corpuslce
    • fibers of the hypodermis are continuous with those of the dermis
    • hypodermal layer permits skin to move freely over underlying bone and muscle without putting tension on the skin
  16. Special features of the integument
    • pigmentation
    • paw pads
    • planum nasale
    • ergots and chestnuts
    • cutaneous pouches in sheep
  17. Pigmentation
    • result of the presence or absence of melanin granules in the extensions of melanocytes
    • no pigmentation if granules are concentrated around the nucleus of the melanocytes
    • as granules move into the cellular extensions and into the surrounding tissue, pigmentation becomes macroscopically apparent
    • the more granules present, the darker the pigmentation
    • melanocyte - stimulating hormone controls dispersion of granules
    • keratinocytes arrange melanin on the side of the cell with the greatest amount of sun exposure
    • acts to protect keratinocytes from exposure to damaging ultraviolet rays
  18. Paw pads
    • thick layers of fat and connective tissue with exocrine sweat glands and lamallar corpuscles
    • outer surface is the toughest and thickest skin in the body
    • often pigmented; composed of all 5 epidermal layers
    • conical papillae can be seen covering the entire pad
  19. Planum Nasale
    • top of the nose in cats, pigs, sheep and dogs
    • planum nasolbiale - the muzzle of cows and horses
    • usually pigmented
    • aglandular except in sheep pigs and cows
    • cpmposed of only 3 epidermal layers, germinativum, spinosum, corneum
  20. Ergots and Chestnuts
    • dark horny structures found on the legs of horses, ponies and other membranes of the equine family
    • thought to be vestiges of carpal and tarsal pads of the 2nd and 4th digits (splint bones)
  21. Cutaneous Pouches in sheep
    • infoldings in the skin
    • infraorbital, interdigital and inguinal pouches
    • contain fine hairs and numerous sebaceous and tail glands
    • secrete a fatty yellow substance which covers and sticks to the skin when dry
  22. Related structures of the integument
    • hair
    • glands of the skin
    • claws and dewclaws
    • hoof
    • horns
  23. Hair
    • hair strand and follicle
    • types of hair
    • functions of maintaining body temp; camouflage
    • hair shaft is visible above the skin
    • hair root is buried within the skin
    • hair follicle anchors the hair
    • deepest part of hair follicle expands to form a hair bulb
    • at the base of the hair bulb is a mound of dermal cells called the papilla
    • hair strands are formed as epithelial cells mature, fill with keratin and move away from papilla
  24. Hair Follice
    • root sheath layers include the connective tissue root sheath, external root sheath and internal root sheath
    • each hair strand is organized into three layers : cuticle, cortex and medulla
  25. Growth Cycles of hair
    • anagen phase: cells are added at the base of the root , hair lengthens
    • catagen phase: period of transiton between anagen and telogen phases
    • telogen phase: maximum length of hair is achieved, hair stops growing, hair follicle shortens and hair is held in a resting phase
  26. Hair color
    • melanocytes transfer melanin to the cortical and medullary cells that form the hair strand
    • different colors result from the quantity and type of melanin incorporated into the hair
    • *horses produce one type of melain*
    • *dogs produce 2 types of melanin*
    • as animals age, melanin production decreases and hair begins to turn grey
    • white hair is formed when the cortex loses its pigment entirely and the medulla becomes completely filled with air
  27. Types of hair: primary or guard hairs, secondary or wool type hairs, tactile or sinus hairs
    • Primary/guard hairs: straight or arched; thicker and longer than secondary hairs
    • Secondary/wool hair: softer and shorter than primary hairs; wavy or bristled in the dog; predominant hair type is species with wool type coats
    • Tactile/sinus hairs: contain numerous sensory ending, commonly known as whiskers; also mixed with intermittenly throughtout the hair coat, also called sinus hair cause of the large blood sinus located in the conn tissue portion of the follicel
  28. Arrector Pili Muscle
    • small, smooth muslce
    • attatched to each hair follicle
    • innervated by the sympathetic nervous system
    • contraction of the muscle pulls the hair into an erect position
  29. Glands of the skin:
    • Sebaceous glands
    • Sweat glands (sudoriferous glands)
    • Eccrine and Apocrine
    • Tail Glands
    • Anal Sacs
  30. Sebaceous glands
    • Located in the dermis; may be simple or complex alveolar structures
    • Most have a single duct that empties into the hair follicle; others have ducts that empty directly onto the suface of the skin
    • Epithelial cells lining sebaceous gland manufacture and store sebum
    • Because the epithelial cells is lost in the process of secretion, the sebaceous gland is classified as a Holocrine gland
    • Composed primarily of glyceroids and free fatty acids
    • Arrector pili muscles contrat and compresses sebaceous glands, forcing sebum through the duct into the hair follicle
    • Coats the base of the hair and surrounding skin; helps trap moisture, keep hair soft, pliant and somewhat waterproof; sebum also helps reduce the skins risk of infection
  31. Sweat Glands
    • also called sudoriferous glands
    • found over the entire body of most domestic species
    • sweat helps cool the body through evaporation
    • two types of sweat glands are Eccrine and Apocrine
    • Eccrine Glands: found in the pads of animals; excretory portion consists of a simple coiled tube located in the dermis or hypodermis; empty into the surface of the skin through a long duct
    • Apocrine Glands: coiled excretory portion buried in the dermis or hypodermis; single excretory duct; empty into the hair follicle
  32. Tail Glands
    • an oval region at the dorsal base of the tails of most dogs and cats
    • contains coarse, oily hairs
    • very large apocrine and sebaceous glands present
    • thought to assist with recognition and identification of individual animals
  33. Anal Sacs
    • cats and dogs have anal sacs similar to musk glands of skunks
    • located at the 5 and 7 O'clock positon relative to the anus
    • connected to the lateral margin of the anus by a small duct
    • lines with sebaceous and apocrine glands
    • when an animal defecates or becomes frightened, some or all of the material is expressed
  34. Claws and Dewclaws
    • Claws: hard outer covering of the distal digits; usually pigmented; function in maintaining traction and serve as tools for defense and catching prey; claws are nonretractable except in most cat species.
    • Dewclaws: evolutionary remnants of digits; in the dog, the dewclaw is the first digit; in the cow, pig and sheep, the medial and lateral dewclaws are the second and fifth digits, respectively
  35. Hoof
    • horny outer covering of digits of some animals
    • another name for hoof is ungula *hoofed animals are called ungulates*
    • hooves rest on tissue called corium
    • the corium is attatched to the periosteum of the distal phalanx
    • the outer hoof is a modified epithelial layer and the corium is modified dermis
    • the skeletal foot of the horse includes the distal part of the second phalanx, the distal sesamoid bone (navicular bone) and the entire third phalanx (coffin bone)
    • the coffin bone has a layer of corium,which in turn is covered by the cornified hoof
    • the hoof and the corium from intergigitaitons called laminae
    • the equine hoof is generally divided into three parts = wall, sole and frog
  36. equine hoof - the wall
    the external portion of the hoof visible from the anterior, lateral and medial views; divided into the toe, the quarters and the heels
  37. equine hoof - the sole
    plantar or palmar surface of the hoof; outer layers are avascular and lack innervation(nerves)
  38. equine hoof - the frog
    • triangular horny structure located between the heels on the underside of the hoof
    • divided by a central depression known as the central sulcus
    • digital cushion is a thick pasd of fat and fibrous tissue that lies beneath the sensitive from
    • lateral cartilage extends proximally form the distal phalanx
  39. Horns
    • epidermal in origin
    • structually similar to hair
    • composed of keratin
    • in adults, the horn is hollow and communicated directly with the frontal sinus
    • the corium lies at the root of the horn and is bound to the horn process by periosteum
    • the body of the horn is composed of tightly packed tubules
    • the wall of the horn is thinner at the base than the apex
Card Set
the integument
the integumentary system