Integument - Exam 1

Exam 1

integument

7-10% of BW

skin (epidermis, dermis, hypodermis*)

glands (sweat and sebaceous)

cutaneous scent glands

hair

wound healing

claws (cat and dog)

hooves

feathers

horns and antlers

special skin structures (mammary glands, anal sacs)

skin function

protection - dehydration (wounds), infection (physical barrier)

sensory function

secretion/excretion

regulation of body temperature (sweat, blood flow to skin)

absorption of UV (Vit D production)

skin layers

epidermis - epithelium (keratinized, stratified squamous), avascular (5)

dermis - blood supply, relatively few cells, dense irregular CT (type 1 collagen) (1&2)

hypodermis - loose CT, superficial fascia

epidermis

thick skin (glabrous)

• no hair follicles

• up to 5 identifiable layers

• merocrine sweat glands

thin skin (nonglabrous)

• has hair follicles

• thin stratum corneum

• stratum lucidum (absent) and granulosum (hard to define)

• apocrine sweat glands

layers of epidermis

stratum basale

stratum spinosum

stratum granulosum

stratum lucidum (not evident on slide)

stratum corneum

straum basale

cell division (stem cells give rise to keratinocytes [cells in epidermis])

sits on basement membrane

melanocytes → produce pigment

merkel cells → nerve receptor

stratum spinosum

cells attached by desmosomes (cells shrink in staining and desmosomes make it look like they have spines) (all cells in epithelium attached this way)

membrane coating granules

keratinization begins

stratum granulosum

cells still have nuclei (last layer w/ nucleus)

keratohyalin granules

stratum lucidum

packets of keratin from here move up towards surface

only in thick skin

lack organelles and nuclei

keratin filaments

really only in human histo and only in palms/soles, and not all people

stratum corneum

further from surface - still have desmosomes

closer to surface - desmosomes breakdown, desquamated (sloughed off)

melanocytes

thick and thin skin

large cell, multiple processes coming off

derived from neural crest cells

located in the basal layer

source of melanin for keratinocytes (same # of melanocytes in black and white, differ in melanin production)

also found in the external root sheath and matrix of hair

merkel cells

thick and thin skin

light touch receptors

slow adapting

special stain required to visualize

located in s. basale

dendritic cells

thick and thin skin

langerhans cells

monocyte derived (patrol for foreign material) (macrophages)

special stain required to visualize

Antigen Presenting Cells (APC) - take pateria to lymph nodes (lymphocyte) to initiate immune response

dermis

reticular layer (thick and thin)

papillary layer (thick skin only)

reticular layer of dermis

dense irregular CT (type 1 collagen and elastin)

sweat glands

hair follicles, arrector pili muscles

mechanoreceptors

blood and lymph vessels

papillary layer of dermis

dermal ridges

loose CT

anchoring fibrils from basal lamina of epidermis

increase surface area for interaction between epidermis and dermis bc more abrasion in thick skin (foot pads, etc.)

hypodermis

loose CT

anchors dermis to underlying muscle/bone

adipose tissue

fat pads (structural fat) (pads of feet bottoms)

burn classification

sebaceous glands

simple branched acinar (alveolar) glands

release sebum via holocrine secretion

• antimicrobial (FAs acidify environment, Fe binding so bacteria can’t grow, antibodies - IgA, IgG)

• waterproofing - lipid content

secrete into hair follicle (most frequent)

sweat glands

simple coiled tubular glands

apocrine

• throughout all haired skin (thin)

• viscous secretion that contains scent (pheromone based)

• secretes into hair follicle

merocrine (eccrine)

• thick skin

• limited distribution in animals (very efficient in humans)

  • foot pads in dogs and cats, nasal planum

  • watery secretion onto skin surface

function of sweat glands in heat loss varies in importance between sp. (horse>cattle>sheep>dog>cat>pig)

hair follilce

produces hair, a flexible keratinized structure (hard keratin)

embedded in dermis

hair (medulla, cortex, cuticle)

external root sheath - continuous with epidermis, shoots down into dermis

internal root sheath - protect hair from immune system

bulb - at base of follicle

• hair matrix - hair matrix cells (analogous to s. basale) produce hard keratin

• dermal papilla - blood supply

hair follicle types

follicle includes - hair, sebaceous and apocrine glands, arrector pili muscle (smooth muscle)

Simple (A)

• single hair from one external orifice

Compound (B)

• one/few primary hair(s), several/many secondary hairs

• secondary hairs - thinner (undercoat), reduced/absent medullary

• primary hair - outer/ground coat

• all hairs emerge from same external orifice

• arrangement of compound follicles depends on species/breed/age (newborn animals have simple and become compound with age; Lanugo - organized as simple and no medulla)

sinus/tactile hair follicles

whiskers

blood filled cavity between inner and outer root sheath

innervated by sensory nerve bundles (in external root sheath

movement induced pressure waves through blood filled sinus

hair growth cycle

anagen - active growth phase (hair matrix and dermal papilla)

catagen - growth slows and stops (dermal papilla reduced), entire bulb (matrix) becomes keratinized and begins to move superficially towards the sebaceous glands

telogen - follicle is quiescent (resting), club hair (internal root sheath breaks down, becomes frayed at bulb)

renewed anagen - new hair pushes out old one

under control of hormones, day-length, temperature, and nutritional status

claw

derivative of skin (epidermis and dermis)

covers distal phalanges (cat and dog)

epidermis (dorsal ridge, wall, sole)

underlying dermis (corium) - rich in blood supply, ‘quick’

DR grows faster than wall (curved appearance)

sole produces along entire plane of blood supply

hollow horns

domestic ruminants (cattle, sheep, goats); male and female (male larger)

Basic bony core is the cornual process from the frontal bone

dermal core covering the cornual process (dermis)

covered with keratinized epithelium (epidermis)

permanent

antlers

cervids (generally only males, reindeer and caribou females have small)

bony outgrowth from frontal bone (pedicle) - endochondral ossification

covered with velvet (dermis and epidermis)

antlers shed seasonally

fastest bone production

• elk - 1in/d

• deer - 0.25-0.5 in/d

mammary gland

compound acinar gland (tubuloacinar in some sp.)

highly modified sweat glands

alveoli, ducts, and interstitial tissue

merocrine (protein and carbohydrates) and apocrine (lipids) secretion

active vs inactive

• involution: inactive → active

• first 3 lactations, add more mammary tissue

• after 3, add more CT and adipose during involution

anal sacs

carnivores (skunk, ferret)

paired diverticula opening into the anal canal at anocutaneous junction

glandular tissue is in wall, sac is innately hollow

dogs - apocrine glands in the wall, sebaceous glands newat the duct (holocrine, viscous potentially harder to express)

cat - sebaceous and apocrine glands in the wall (equal distribution)

do not fuse with perianal (circumanal) glands