INTEGUMENTARY SYSTEM

CH 8

ROOTS

• derm/a, derm/o, dermat/o = skin

• pil/o, ,trich/o = hair

• kerat/o = horny tissue

• hidr/o, sudor = sweat

• sebum = sebaceous gland secretion

• cerumen, cermin/o = earwax

SKIN INTRO

• ________ organ of the body 

• ACCESSORY ORGANS: hair, sweat glands, sebaceous glands, nails

• FUNCTIONS OF THE SKIN:

-Barrier against invasion of microorganisms

-Protects underlying structures from injury

-Prevents the body from drying out

-Maintains and regulates body temp

-Receptor for senses: touch, heat, cold, pressure, pain, -Disposes of waste products

LAYERS

• _____________: Outer, thinner layer, visible to the naked eye

• Made of 5 layers of __________ __________ epithelial tissue  

- from deepest to most superficial:

1) STRATUM GERMINATIVUM– basal layer; cells continuously multiply and are pushed to outer layer until they die and are sloughed off; continuous process

2) STRATUM SPINOSUM– spinous layer; cells in this layer are shrunken and spaced apart; thick in areas that are susceptible to wear and tear

3) STRATUM GRANULOSUM– granular layer; granules in the cytoplasm of cells are visible; cells are beginning to die; not present in all areas (esp in hairy skin); keratinization begins

4) STRATUM LUCIDUM– clear layer; cells are closely packed and clear; not always present (esp in hairy skin), but when it is, it is found in areas of wear and tear

5) STRATUM CORNEUM– horny layer; cells are flat, lifeless, and cornified (keratinized); cells are overlapping, dry; give horns, hooves, beaks, and hair their strength; dead cells are continuously sloughed

DERMIS

– inner, thicker layer of skin

-made of dense, fibrous connective tissue that contains blood vessels and nerves

-also contains hair, involuntary muscle, sebaceous glands, sweat glands, and sensory receptors

 

 

HYPODERMIS

-layer under the dermis

-also called subcutis/subcutaneous layer

-consists of fatty (adipose) tissue

-allows the skin to move without tearing

 

 

SKIN THICKNESS

-thickest in areas of _______ & ________ (footpads, forehead, dorsal neck, dorsal thorax, rump, base of tail)

-_______________: elephant, rhinoceros, hippopotamus

-thin skinned areas: pinna of the ear, axillary, inguinal, scrotal, periorbital, and perianal regions

SKIN COLOR

• DETERMINED VIA ______________ – skin pigment produced by melanocytes in the form of granules

-melanocytes are located in stratum germinativum, however the granules aren’t visible in the cell’s cytoplasm until stratum granulosum

- amount of melanin granules determines color of skin

-help to protect against damaging effects of the _________

• ______________ – congenital defect of melanin development

-normal pigmentation is not present in hair, skin, eyes

-lack protection against sunlight

• BLOOD SUPPLY can affect skin color.

-____________ occurs when oxygen supply is reduced in nonpigmented skin

HAIR- FUR - short, fine hair

3 TYPES OF HAIR:

-PRIMARY (#1)– “__________” hair, top coat-stiff, but with a smooth appearance-water runs off the coat of the animal without

chilling the animal

-SECONDARY (#2)– “___________” hair, undercoat-soft, shorter, thin, wavy

-_______________-thicker and longer than primary hair-found around the face-grow from hypodermis or superficial muscle layer-Each hair is innervated, allowing them to be touch receptors-EX: cat whiskers (vibrissa – any large tactile hair)

-Hair develops from the ____________, which is located inside the hair follicle. -Follicle sits at a 30-60 degree angle to the skin-Hair _____________ is what is visible

-_______________ __________– bundles of involuntary muscle that are attached to hair follicles-hair stiffens when the muscle contracts-plays a part in the fight or flight response

-_______________ – hair along the neck and back that is raised when an animal needs to increase its size during a fight

HAIR

HAIR

- 2 ARRANGEMENTS FOR HAIR GROWTH:

_____________ – primary hairs grow from separate follicles (cows, horses)

_____________________ – 2-5 primary hairs grow from each follicle (dogs, cats) and are surrounded by clusters of secondary hairs; all are growing from a common pore

-THERMAL REGULATION is affected by HAIR COLOR-light colored coats are cooler in hot, sunny climates

-________________– individual hairs have several bands of light and dark pigments with black tips

-________________ – process of losing hair-peaks every spring and fall-affected by photoperiod, temperature, nutrition, hormones, genetics, health

GLANDSSWEAT GLANDS (sudoriferous glands)

-cool the body

-dogs and cats sweat very little amounts that is usually masked by the hair coat; horses should be able to sweat in much larger amounts

- panting, slobbering, and smearing saliva on their coats helps to dissipate the heat

SWEAT GLANDS CONTINUED

-____________ GLANDS – found throughout the body-secrete strong-smelling substance into follicles- often line the external ear canal and over-secretion can lead to otitis externa

-______________ GLANDS – coiled structure whose duct emerges on the skin surface-produce watery sweat-found only on the footpads and between the nostrils in the dog

GLANDS

________________ GLANDS – secrete SEBUM (fatty lubricant) which lubricates the skin and hair, waterproofs the coat, gives the coat a glossy sheen, spreads sweat, slows bacterial growth, and acts as a territory marker

-absent on foot pads and nose

-_______________ = an excessive discharge from the sebaceous glands resulting in abnormally oily skin

-___________________GLANDS – on lips of cats, marks territory

-___________ GLANDS – produce a strong odor that makes female goats attracted to male goats during breeding season. Located caudomedially to the horns

-__________ __________– pouches at 4/5 and 7/8 o’clock. Foul smelling secretion that is expressed during defecation and serves as a territory marker

SEBACEOUSGLANDS

CERUMINOUS GLANDS- modified sweat glands located in the external ear

canal

-secrete earwax (aka _______________)

NAILS, CLAWS, HOOVES-modified epidermal structures of the distal phalanges

-used for protection, scratching, digging, or defense in battle

-dermis contains nerves and blood vessels

-all have a WALL, SOLE, and PAD, but with variations

-___________ = hoof or claw

-___________ = underside of hoof or claw-flaky in small animals-abundant surface area in horses

-__________= finger tip-small animals have individual digit pads, metacarpal and metatarsal pads, and a carpal pad

-horses have a _________ that pads the hoof and acts as a shock absorber with the bulbs

DEWCLAWS

-serve no practical purpose

(are often removed in dogs)

-usually found on front legs in small animals, but can also be found on hindleg

-dogs can be “double dewclawed” – required in Great Pyrenees

-look like miniature hooves in ruminants

CHESTNUTS, ERGOTSCHESTNUTS

-vestigial carpal and tarsal pads-flattened, oval masses of horn in the horse-found on the medial surface of the legs just proximal to the carpus and at the distal end of the tarsus

ERGOT-vestigial metacarpal/metatarsal pads -small mass of horn in a patch of hair on the palmar/plantar aspect of the horse’s fetlock

HORN

-permanent structure of keratinized epithelium that grows continuously after birth and originates from the frontal bone

-never branched and are never shed

-Hornless breeds of species that can have horns are called POLLED

-Shape of horn is determined by breed, sex, age

-male horns are usually larger

-cattle horns are located in temporal position, sheep and goats are in a parietal position

-goat horns grow caudally

-sheep horns are curled

ANTLERS

-found on male deer and reindeer, and caribou (both male and female)

-also grow from the skull, but are made of bone instead of keratin

-shed and regrown every year, becoming more complicated in structure

-Each year the horns are initially covered in VELVET which is soft hairy skin that produces the antler. The velvet is rubbed off as the skin dies and the bony process is exposed. Once the antler is exposed it begins to lose blood supply and is eventually shed.