Ch. 6 Integumentary System (skin & related structures)

Question 1

Integumentary System

Answer 1

• _{composed of all 4 tissue types}
• _{inlcudes hair, hooves, horns, & claws, as well as skin-related glands}
• _{outer layer composed of dead cells}
• _{<u>Keratinization</u> occurs as cells die}
• _{protective and regulatory functions}

Question 2

General FUNCTIONS of Integumentary

Answer 2

• _{covers and protects underlying structures}
• _{prevents desiccation}
• _{assists in maintenance of body normal temperature}
• _{excretes water, salt, and organic wastes}
• _{sensory organ - relay tactile and pressure info to CNS}
• _{vitamin D synthesis and nutrient storage}

Question 3

Integument = SKIN

Answer 3

• _{2 layers}
  
  • _{<strong>Epidermis - </strong>keratinized stratified squamous epithelium}
  • _{<strong>Dermis </strong>(corium) <strong>-</strong> dense fibroelstic connective tissue}
• _{<strong>Hypodermis = </strong>subcutaneous layer/subcutis}
  
  • _{primarily adipose tissue for thermo-insulation and mechanical shock absorption}
  • _{pressure receptors = <u><strong>pacinian corpuscle</strong></u>}
  • _{allows skin to move freely over underlying muscle and bone without putting tension on the skin that would result in tearing}

Question 4

Epidermis (cells)

Answer 4

• _{<strong>Keratinocytes - </strong>majority of epidermal cells}
• _{<strong>Melanocytes - </strong>produce melanin}
• _{<strong>Langerhan’s cells - </strong>macrophages only found in epidermis}
• _{<strong>Merkel cells - </strong>form Merkel disks}

Question 5

Keratinocytes

Answer 5

_{Majority of epidermis cells}

• _{produce <strong><u>kertain</u></strong> = tought, fibrous, waterproof protein -> <strong>gives skin it’s resilicency and strength</strong>}

Question 6

Melanocytes

Answer 6

_{Produce <strong>melanin</strong><strong> </strong>= dark brown-black pigment stored in membrane bound granules called <strong><u>melanosomes</u></strong>}

_{-> absorbed by keratinocytes -> melanin <u><strong>protects from UV exposure</strong></u>}

Question 7

Langerhan’s Cells

Answer 7

_{Macrophages only found in epidermis}

_{-> originate in bone marrow and migrate to skin}

_{-> <strong>phagocytize microbes and stimulate other cells of immune system</strong>}

Question 8

Merkel Cells

Answer 8

_{Form Merkel disks with sensory nerve ending of epidermal-dermal junction}

• _{<strong>though to aid in touch sensation</strong>}

Question 9

Epidermal Layers

Answer 9

Deepest to Most Superficial

• stratum germinativum (stratum basale)
• stratum spinosum (spiny layer)
• stratum granulosum (granular layer)
• stratum lucidum (clear layer)
• stratum corneum (horny layer)

Question 10

Stratum germinativum

Answer 10

_{(stratum basale)}

• _{attached to basement membrane}
• _{new cells produced here and move up}

Question 11

Stratum spinosum

Answer 11

_{(spiny layer)}

• _{Langerhan’s cells located here}

Question 12

Stratum granulosum

Answer 12

_{(granular layer)}

• _{keratinization occurs here}

Question 13

Stratum lucidum

Answer 13

_{(clear layer)}

• _{keratinized clear cells, only in very thick skin areas}

Question 14

Stratum corneum

Answer 14

_{(horny layer)}

• _{outermost, thickest layer}
• _{cornified remnants of keratinocytes (dandruff)}

Question 15

Keratinization

Answer 15

• _{produces <u><strong>keratin</strong></u>, a type of surface specialization providing protection and waterproofing for skin’s surface}
• _{as older cells travel up from basal layer, they fill w/ keratoyhyaline and glycolipid granules, lose thier nuclei, cytosol and organelles and become dead sheets of keratin -> dead cells and keratin slough off as dander / dandruff}

Question 16

Dermis

Answer 16

_{makes up the largest part of the skin}

• _{provides structural strength of skin}
• _{composed of 2 layers}
  
  • _papillary
  • _reticular
• _{few cells compared to the epidermis, including fibroblasts, adipocytes and macrophages}
• _{contains hair follicles, nerve endings, tough (Meissner’s corpuscles) and temperature receptors, glands, smooth muscle, blood vessels and lymphatics.}
• _{provides epidermis (avascular) w/ nutrients that diffuse up through basement membrane from dermal interstitial fluid}

Question 17

_{dermis layer}

papillary

Answer 17

_{loose conective tissue with fibers and ground substance; just beneath epidermis; forms <strong><u>dermal papillae</u></strong>}

Question 18

_{dermis layer}

reticular

Answer 18

_{irregular connective tissue containing collagen, elastic and reticular fibers; 80% of dermis; most fiber bundles run parallel to one another; orientation depends on direction of the stress placed on them}

Question 19

_{special feature}

Foot / Paw Pads

Answer 19

_{= thick layer of fat and connective tissue w/ tough, thick outer epidermal surface often pigmented and composed of all 5 epidermal layers.}

• _{bear the weight of animal}
• _{protection against abrasion}
• _{protection against thermal extremes}
• _{sweat glands are funtional and secrete onto the surface of pad}

Question 20

_{special feature}

^{<strong>Planum nasale</strong>}

Answer 20

_{<strong> = nasal planum</strong>}

• _{top of the nose in dogs, cats, pigs, sheep, and goats.}
• _{called planum nasolabiale in horses and cattle}

_{= only 3 epidermal layers in the dog; usually pigmented; no glands in epidermis or dermis in the dog; tubular glands in ruminants and pigs.}

Question 21

_{special feature}

^{<strong>Ergots and Chestnuts</strong>}

Answer 21

_{> dark brown, horny patches on legs of horses and other equid species}

_{= vestiges of carpal and tarsal pads of the 2nd and 4th digits.}

Question 22

_{special feature}

^{<strong>Cutaneous pouches of Sheep</strong>}

Answer 22

• _{<strong>Infraobital</strong>}
• _{<strong>Interdigital</strong>}
• _{<strong>Inguinal</strong>}

_{= infolding of skin forming pouches containing sebaceous (oil) glands -> <strong>secretions used in marking territory, courtship, etc.</strong>}

Question 23

_{<strong>Functions of Hair / Fur</strong>}

Answer 23

• Thermoregulation
• Camouflage
• Intra- and Interspecies communication
• Touch perception

Question 24

Thermoregulation

Answer 24

_{- insulate by trapping layers of air -> erection of hairs when cold}

Question 25

**Camouflage**

Answer 25

- coat color (melanin / pheomelanin)

Question 26

**Intra- and Interspecies communication**

Answer 26

_{- erection of hair when aroused or frightened} * _{degree of erection = implantation angle} * _{Arrector pili muscle - smooth muscle attached to hair follicle and innervated by sympathic nervous system}

Question 27

**Touch perception**

Answer 27

_{- tactile hairs = sinus = tylotrich hairs = whiskers (used as probes)} * _{also are mixed intermittenly throughout the coat} * _{well supplied w/ sensory nerve endings -> very sensitive to slightest bending or touch}

Question 28

**Hair Growth cycles**

Answer 28

_{Anagen phase - active growth when hair shaft lengthens Telogen phase - quiescent, resting phase occuing when maximum length achieved, hair stops growing and follicle shortens} * _{Telogen Effluvium - loss of large % of hair volume at one time due to metabolic stress or illness Catagen phase - transitional period between anagen and telogen phases.}

Question 29

**Sebaceous Glands**

Answer 29

* _{located in the dermis (not in foot pads or nasal planum)} * _{simple or compound acinar gland; holocrine} * _{duct empties into hair follicle -> arrector pili muscle squeezes secretion out or empties directly onto surface of skin} * _{Secretion = sebum (lanolin in sheep) - thick and oily - composed of glycerides and free fatty acids -> coats hair and traps moisture -> keeps skin moist and supple; some antibacterial and antifungal properties.} * _{can clog folllicle causing blackheads (comedones) that can become infected}

Question 30

**Sweat (sudoriferous) Glands**

Answer 30

_{- Present in most domestic species but only functional (produce sweat) in equids and to a lesser extent in ruminants 2 types (both merocrine secretion} * _{Eccrine - empty onto skin surface - simple, coiled tube in dermis connected to skin surface by lonf duct; in foot pads and deep fat layers in dogs} * _{Apocrine - empty into hair follicles - single coiled secretory/excretory duct; in external ear canal}

Question 31

**Tail glands**

Answer 31

* _{oily patch at dorsal base of tail in dogs and cats} * _{sebaceous and apocrine glands} * _{assists in communication of identification of individuals; sensitive to sex hormome levels}

Question 32

**Anal sacs**

Answer 32

* _{lined with sebaceous and apocrine glands} * _{stores secretion produced -> expressed during defecation or when frightened or excited} * _{used in marking territory and attracting mates}

Question 33

**Claws and Hooves**

Answer 33

* _{Hard outer layer composed of keratin; inner layer = corium = modified dermis} * _{for maintaining traction when running, walking and climbing} * _{catching prey} * _defense

Question 34

_{Horns (ruminant ungulates) / Antlers (cervids)}

Answer 34

* _{HORNS are epidermal origin; structurally similar to hair} * _{ANTLERS are dermal bones and arise from skull; found primarily in males and are shed annually} * _{function in defense and offense / courtship} * _{grow continually and are not shed (except in pronghorn)} * _{some domestics are bred to be horn free (polled)}