Integument II

What are the three cycles of hair growth?

Anagen, catagen, telogen

The arrector pili muscle is innervated (stimulated) by the:

Sympathetic nervous system

Which type of sweat gland empties directly into hair follicles?

Apocrine sweat gland

Functions of Hair

• maintenence of body temperature

• protection via camouflage

• sensory

What are the three concentric layers of hair?

• medulla

• cortex

• cuticle

Medulla

Innermost layer

2-3 layers of loosely arranged cells

contains flexible soft keratin

cortex

middle layer

thickest

contains stiff and rigid hard keratin

cuticle

hair surface

single layer of cells containing hard keratin

Compound follicle

• Multiple hair stands in a single pore (an opening through which hair emerges through the skin)

• Each hair has its own follicle and bulb

• each compound follicle has a long primary hair, surrounded by shorter secondary hairs

Influences of hair growth and shedding

• environment 

• genetics

• hormonal 

Anagen

• dead keratinized epithelial cells push up and away from the dermal papilla

• make up the shaft and the root

• As more cells are added, the hair lengthens

• grows to genetically predetermines length 

catagen

transition period between anagen and telogen

Telogen

Hair is held in resting phase

How is hair color formed?

Pigment in cortex and medulla of hair stand

melanin produced in bas of hair follicle 

pheomelanin

yellow and reddish colors

tyrosine melanine

brown and black colors

Primary hairs

Guard hairs

straight or arched; thicker and longer than secondary hairs

dominant hairs and complex hair follicles

Secondary hairs

wool-type hairs

softer and shorter than primary hairs 

promary hair type in species with wool coats

Tactile hairs

whiskers

used as probes and feelers

also mixed intermittently throughout the hair coat

Implantation angle

the degree that the hair naturally stands

Arrector pili muscle

small, smooth muscle

attached to each hair follicle

innervated by the sympathetic nervous system 

contraction pulls the hair erect

What part of the hair is visible above the skin?

Hair shaft

During what phase of the hair cycle does growth occur?

Anagen

What is the primary type of hair in sheep?

Secondary

What 2 factors stimulate hair to stand up?

cold and fear

Sebaceous glands

located in the dermis

• simple or complex alveolar structures

• produce sebum, lanolin

• Most ducts empty into the hair follicle

• Others empty directly onto skin

Sebum

oily, lipid substance

stored by sebaceous glands

sebum forced through the duct into the hair follicle

Lanolin

sebaceous gland of sheep produce substance that becomes lanolin]

aids in waterproofing the sheeps coat

Sweat glands

Sudoriferous glands

water transparent liquid

helps cool the body through evaporation 

2 types: eccrine and apocrine

Eccrine

empty onto surface of skin

apocrine

empty into hair follicles

Tail glands

oval region at dorsal base of tails of most dogs and cats

assists animals in identificaiton of one another

Anal sacs

reservoir for malodorous secretions, similar to those from musk glands

• lined with sebaceous and apocrine glands

• contents are expressed : defacation and when animal is frightened

Claws

hard outer coverings of the distal digits

hard plates of tightly packed keratinized cells 

5 types of corium in equines

• Laminar corium

• perioplic corium 

• coronary corium

• sole corium 

• frog corium 

Laminae

• hoof and corium form array of interdigitations

• forms the attachment between the hoof and the coffin bone

What part of the equine hoof is convex and the external portion is divided into toe, quarters, and heel?

Wall

Declawing a cat is better described as digit amputation of P3

True

What direction does the equine hoof grow?

From coronary band downward towards sole

Horns

• mass or horny keratin

• grow continuously, not sex relatedstructually similar to hair, epidermal in origin

• hollow, communicate directly with frontal sinus

Antlers

primarily on males

dermal in origin

shed annually

lack central core and internal blood supply

velvet skin