Veterinary Anatomy: Mammary Gland and Lactation

serving as shock absorbers, protecting the skeleton, and acting as sensory organs

They convey milk to the lactiferous sinus and then to the teat sinus

It consists of superficial and deep layers of external fascia of the trunk, comprising lateral and medial fascial sheets that extend between mammary complexes

The hoof capsule forms the hoof wall, sole, and frog, and is modified to serve as a weight-bearing structure

The segments vary in terms of carpal/tarsal pads, metacarpal/metatarsal pads, and digital pads

It forms claws, hooves, or nails, depending on the species

It determines the segmentation of digits, along with the presence or absence of papillary body and structure of stratum corneum

It consists of epithelial glandular tissue arranged in lobules, comprising alveoli that produce and secrete milk

Bitches have 8-12 mammary complexes with 5-20 mammary units each, while mares have 2 mammary complexes with 2 mammary units each

It is formed by the perioplic and coronary segments, and its structure and function vary across species

The three main components of a hair are the central medulla or core, the cortex, and the outer cuticle. The central medulla is the innermost layer, the cortex is the middle layer, and the outer cuticle is the outermost layer.

The function of arrector muscles of hair is to contract and cause the hair to stand upright, improving thermal isolation by trapping a layer of air close to the skin.

The type and number of melanin granules in keratinocytes determine the color of hair, with different types and amounts of melanin producing different shades and hues.

Sebaceous glands produce fatty secretions (sebum) that lubricate and waterproof the skin and coat, while sweat glands produce watery or albuminous secretions that help regulate body temperature and provide individual odor. Sebaceous glands often drain into hair follicles, where they mix with sweat gland secretions.

There are two main types of sweat glands: eccrine sweat glands, which produce watery sweat and are found in hairless regions, and apocrine sweat glands, which produce albuminous sweat and are often associated with hair follicles. Apocrine sweat glands are more common in horses and provide individual odor.

Specialized forms of skin glands include perianal glands, circumoral glands, and tail glands, among others. These glands have distinct functions and distributions in different species, such as the anal sac glands in carnivores and the dorsum tail glands in cats.

The mammary gland is a modified sweat gland of the exocrine, tubuloalveolar type, composed of one or several mammary units, each with a body and teat. The number of mammary complexes and their distribution vary among species, such as the thoracic to inguinal region in carnivores and pigs, and the restricted to groin region in horses and ruminants.

The three basic coat types based on length are normal (e.g. German Shepherd), short-hair (e.g. Boxer), and long-hair (e.g. Chow). Each type has distinct characteristics, such as the length, color, and diameter of the hairs, as well as the presence of guard hairs and undercoat.

The patterns of hair differ among species, with carnivores having multiple hairs sharing a single follicle opening, and domestic animals having varying hair stream patterns. Hair streams are important for sensing the environment and providing tactile information.

Tactile hairs are specialized hairs that provide sensory information about the environment, often found in specific locations such as the nose, ears, and lips. They differ from other types of hairs in their structure and function, with nerve endings in the deep root that respond to touch and vibrations.