Integumentary, My Dear Students, Integumentary

Beauty is Only Skin Deep

DERMATOLOGY The study of Skin

The Skin is the Largest Organ of the Body Depending on the species and age, the skin may represent 12%- 24% of an animal’s body weight The skin has many functions The skin consists of several structures

Functions of the Skin Serves as an enclosing barrier and providing environmental protection Skin offers a two-way barrier over the body. Skin keeps damaging agents out of the body and fluids and nutrients in the body. Regulates temperature Specialization of the skin (hair, fur, and sweat glands) helps animals to maintain a stable body temperature. Produces pigment and Vitamin D During sun exposure the skin is responsible for the synthesis of vitamin D, which is essential in calcium control. The pigment in skin helps to protect the body from damaging ultraviolet radiation. Sensory perception Skin detects pain, pressure, and temperature, thus adding further means of protection.

Structures/Parts of the Skin Epidermis Basement membrane zone Dermis Appendageal System Subcutaneous Muscles and Fat

EPIDERMIS and DERMIS The skin is composed of two principal layers: The epidermis, the outer, thinner layer visible to the naked eye; and the dermis, the inner thicker layer.

EPIDERMIS Multiple Layers of Cells Keratinocytes Melanocytes Langerhans cells Merkel cells Each Of These Cells Has Special Functions

Keratinocytes an epidermal cell that produces keratin Melanocytes a melanin-forming cell Langerhans cell present in all layers of the epidermis except the stratum corneum, which protects against infections, and are most prominent in the stratum spinosum. Merkel cells in basal part of epidermis; dense granules in cytoplasm, functions in tactile sensory perception

The Epidermis Layers of the epidermis, from the dermis outward, are as follows: Stratum germinativum (basal layer) Stratum spinosum (spinous layer) Stratum granulosum (granular layer) Stratum lucidum (clear layer) Stratum corneum (horny layer)

The Basal Layer (Stratum germinativum) The cells in this innermost layer

The Dermis The dermis is made up of dense, fibrous, connective tissue containing blood vessels and nerves.

Appendageal System These structures grow out of the epidermis Hair follicles, sebaceous and sweat glands, and specialized structures (claw, hoof, etc.) Simple hair follicles vs. Compound hair follicles Sebaceous glands secrete sebum into the hair follicles and onto the epidermal surface Sweat glands are part of the thermoregulatory system.

Hair Follicles Grow out of the epidermis Hair follicles of horses and cattle are simple. The follicles have one hair emerging from each pore. Hair follicles of dogs, cats, sheep, and goats are compound. The follicles have a central hair surrounded by 3-15 smaller hairs all exiting from a common pore. Animals with compound hair follicles are born with simple hair follicles that develop into compound hair follicles.

Sebaceous Glands Secrete sebum into the hair follicles and onto the epidermal surface Present in large numbers in the mucocutaneous junction, interdigital spaces, dorsal neck, rump, chin, and tail area. In some species, they are part of the scent-marking system. Cats sebaceous glands are present on the face, dorsum, and tail in high concentration; cats mark territories by rubbing their face on objects and depositing a layer of sebum laced with feline facial pheromones. Sebum is a complex lipid material containing cholesterol, triglycerides, waxes, and fatty acids. Important to keep the skin soft and pliable and maintain proper hydration Gives the hair coat sheen and has antimicrobial properties

Sweat Glands

HYPODERMIS