Skin :Integumentary system of domestic animal Veterinary Medicine Dr. Alok Kumar Chaudhary Ph.D Scholar IVRI Bareilly Assistant Professor Veterinary Medicine, DUVASU, Mathura Phone

Out line of the lecture Integumentary System Integument (skin) and Accessory Organs Cutaneous Membrane (Skin) – largest organ - Epidermis - Dermis Accessory Organs – derive from epithelial cells of the epidermis but all extend into the dermis -Sweat glands and sebaceous (oil) glands -hair follicles -Nails Hypodermis – has similar functions as skin - Fatty layer deep to the skin - connects skin to underlying organs

Introduction Integumentary system of domestic animals

 The integumentary system consists of the skin and its accessory structures, including the hair, nails, sebaceous glands, sweat glands and subcutaneous muscles and fat.

1.Skin

Skin Anatomy The skin of animals consists of two layers 1. Epidermis 2. Dermis and subcutaneous tissue

1.Epidermis The epidermis is composed of multiple layers and cells The epidermis is thickest in large animals compared to small animals

Layers of epidermis

Stratum basale (Basal Layer) The deepest epidermal layer firmly attached to the underlying dermis Consists of a single row of cells mostly young keratinocytes Merkel cells are distributed lightly among the keratinocytes 10-25% of the cells are spider-shaped melanocytes

Cells of epidermal Four types of cells 1.Keratinocytes –produce keratin (tough fibrous protein) 2.Melanocytes - make dark skin pigment melanin 3.Merkel cells – associated with sensory nerve ending 4. Langerhans cells- receptor-mediated endocytosis

1.Keratinocytes - Produce keratin, a tough fibrous protein - Provides physical and mechanical protection - Produces antibiotics and enzymes that detoxify harmful chemicals

2.Melanocytes Produce the skin pigment melanin secretes signaling molecules in response to UV radiation that act to modulate the skin’s immune and inflammatory responses

3.Merkel cells Hemisphere- shaped cells sensitive to touch when compressed release chemicals that stimulate disc like sensory nerve endings (touch receptor)

4-Langerhans cells

Dermis The dermis is a mesenchymal structure that supports, nourishes, and to some degree, regulates the epidermis and appendages The dermis consists of ground substance, dermal collagen fibers, and cells. Cells mainly fibroblasts, melanocytes, mast cells, and occasionally eosinophils, neutrophils, lymphocytes, histiocytes, and plasma cells.Blood vessels responsible for thermoregulation, nerve plexuses associated with Cutaneous sensation Except in horses, apocrine glands do not appear to be innervated

Skin appendages Derived from epidermis but extend into dermis Include  Hair and hair follicles  Sebaceous (oil) glands  Sweat (sudoiferous) glands  claws/hoof

Hair and hair follicles: complex

Microscopic view of dog hair and hair follicle

Next lecture discussion topic Common dermatological disorders in domestic animals