Clinical Anatomy and Physiology for Veterinary technicians chapter 6

Anagen phase

the active phase of hair growth

Anal sac

Perianal sacs, containing apocrine and sebaceous glands, that are located at the 5 o'clock and 7 o'clock positions relative to the anus. The sacs reside between the internal and external sphincters of carnivores and produce a strong-smelling fluid when expressed; they are important for fecal territorial marking and are expressed during fearful episodes.

Angle

the angle of the hoof wall as viewed from a lateral aspect when the foot is flat on the ground

Apocrine sweat gland

Exocrine glands that secrete substances into the hair follicle, rather than directly to the skin surface.

Arrector pili muscle

smooth muscle that is attached to the base of the hair follicle. it is responsible for the involuntary "hair raising" response to cold, fear, or aggression

Catagen phase

the transitional phase between anagen and telogen phases of the hair growth

Central sulcus

the central depression of the frog in the equine hoof

Chestnut

believed to be the vestigial remnants of carpal and tarsal bones or extra toes possessed by ancestors of the modern horse; they are horny, keratinized growths located on the medial forearms and hocks of horses

Coffin bone

the distal phalanx bone of the horse

collateral sulcus

deep ridge on either side of the frog that separates it from the bars in the equine hoof

compound follicle

follicles through which more than one hair emerges

Corium

the dermis of the skin

coronary band

the part of the hoof that articulates with the skin

coronary corium

the part of the corium that has differentiated to provide nourishment to the hoof at the site of the coronary band

cortex

(1) the outer, superficial layer of an organ or structure (2) the outer portion of the kidney. it contains the renal corpuscles, proximal convoluted tubules, distal convoluted tubules, collecting ducts, and peritubular capillaries. (3) in hair, it is the layer surrounding the medulla, composed of hard keratin

cuticle

the single layer of cells that make up the outermost layer of the hair shaft

Defecation

the expelling of feces

Dermis

the deep, connective tissue portion of the skin that contains blood vessels, glands, and hair follicles

Dewclaw

a toe that does not reach the ground, such as the first digit of dogs and cats and the rudimentary medial and lateral toes of cattle

Distal phalanx bone

the phalanx that is located most distally from the body; the tip of the digit

Eccrine gland

exocrine glands that secrete substances directly onto the skin without the loss of cellular material. they contain simple, coiled, tube structures for excretory purposes

epidermal orifice

the opening of the hair follicle through which the hair emerges

epidermis

composed of keratinized stratified squamous epithelium, it is the outermost layer of the skin

ergot

believed to be the vestigial remnants of metacarpal and metatarsal pads, these are the horny, keratinized growths located behind the fetlocks of all equids

frog

the thick triangular pad located on the plantar and palmar surfaces of the horse's hooves. it is one of the important structures of the "circulatory pump" in the equine foot

hair bulb

the bulbous portion of the hair follicle, located within the dermis, that provides the material for hair productions

hair follicle

tubelike invaginations of the epidermis that traverse the dermis and pass into the connective tissue, where the hair is rooted. The arrector pili and sebaceous glands are located in close proximity to the hair follicle

heel

The most posterior region of the hoof.

hoof wall

the external, cornified portion of the hoof. it grows constantly downward from the coronary band to the sole. the deepest layer articulates with the corium by the way of the laminae

horn tube

Minute lines that traverse the hoof wall vertically from the germinating layer of the coronary band to the sole. the deepest layer articulates with the corium by way of the laminae

horn

a horny keratinized extension of the frontal bone in ruminate ungulates. at its root, it arises from the corium. epidermal in origin, horns vary in shape and size depending on age, sex, and species

hypophysis

pituitary gland

implantation angle

the degree of angulation of a shaft of hair

Infraorbital pouch

A pouch of cutaneous tissue found rostral to the medial canthus of the eye in sheep and other ungulates; also called the lacrimal pouch.

inguinal pouch

Also known as the mammary pouch; a pouch of cutaneous tissue found within the inguinal area of sheep.

integument

the outer covering of the body, consisting of the skin and all of its related components, such as nails, hair, hooves, and horns

integumentary system

the skin and all of its related components, such as nails, hair, hooves, and horns

interdigital pouch

A pouch of cutaneous tissue that exudes a waxy substance; found between the toes of sheep and other cloven-hoofed animals.

keratin

a tough waterproof protein that makes up scales, the outer sheaths of beaks and claws, and feathers; a major component of the epidermis, nails, hair, horns, and hooves

keratinization

the normal formation of keratin (a tough, waterproof protein) inside epithelial cells of the skin. as the epithelial cells mature, they fill with granules containing keratin

keratinocyte

cells that synthesize keratin. they have three distinct stages visible in the epidermis: the basal, prickle, and granular cell stages. as keratinocytes travel progressively away from the basement membrane toward the superficial epithelium, they lose their organelles to make way for more keratin. as a result of this process, the cells die by the time they reach the surface

laminae

the interdigitations between the corium and hoof that serve as the attachment sites between the hoof and coffin bone

laminitis

Manifests itself as extreme pain and heat in the equine hoof because of swelling and inflammation of the sensitive laminae. It most often affects equids in their front feet, but in severe cases, it may involve all four feet. There are many causes, such as ingesting large quantities of grains and carbohydrates, drug reactions, retained placenta, and trauma. In severe cases, the coffin bone may penetrate the sole of the hoof; also called founder.

Langerhans cell

the macrophages of the epidermis that phagocytize invading microorganisms and serve as antigen-presenting cells

Lanolin

fat-based secretion of the sheep's sebaceous glands; a by-product of the wool industry, it is used for lotion and ointments

Lateral cartilage

two large bands of cartilage contained within the quid hoof that, in conjunction with the frog and digital cushion, aid in venous return

apocrine gland

a gland whose secretions contain some of its cellular material. Part of the secretory cell is destroyed and must regenerate before the cell can secrete again. examples of these glands are mammary glands and some sweat glands