HYPODERMIS
The hypodermis is a connective tissue layer which serves to anchor the dermis to underlying structures such as muscle & bone. It consists of loosely arranged collagen and elastin fibres for flexibility and movement. To varying degrees’ adipose tissue may also be present.
Blood Vessels, Lymphatics & Nerves
The vascular system plays an important part in the nutrition of the skin, thermoregulation, immunity and absorption of topically applied substances.
Cutaneous arteries give rise to 3 terminal plexi which supply the skin in 3 layers:
1. A deep or subcutaneous plexus 2. A middle or cutaneous plexus 3. A superficial or subpapillary plexus
The richness of the vascular supply to the skin of the horse is evident to anyone who has had to deal with a laceration of the limb of a horse. To support the vascular network there is an extensive network of lymphatic vessels which help to return excessive fluid in the tissues to the vascular space. As a sensory organ, the skin is exquisitely sensitive. Subcutaneous nerve trunks provide the dermis and supply the glands, muscles and hair and also send small branches into the epidermis. The nerve fibre may end as a free nerve ending for the perception of pain or as a Pacinian corpuscle for pressure perception. Thermal and chemical receptors are also present. This sensory information from the exterior is critical if the animal is to respond appropriately to its environment.
Accessory Structures of the Skin
Accessory structures of the skin include hair, glands and hooves.
A. Hair
Hair is present on the whole skin surface of the horse. The thickness and distribution of hair varies and has both genetic and hormonal components. It originates in the dermis and is set an angle to the skin.
Functions of Hair
1. Protective barrier 2. Thermal insulator 3. Participates in wound healing 4. Evaporation of apocrine gland secretions 5. Sensory
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