Friday, 11 September 2015

All About - A Horses Skin

In last week's blog about the Immune System I mentioned that the skin is the first line of defence against invaders.  This is only one of its many functions. The skin is the largest organ of the body, it is a very complex outer protective layer and is very tough.

The skin:
1.       Provides a tough protective layer for tissues underneath
2.       Helps to maintain body heat
3.       Eliminates waste products
4.       Provides camouflage
5.       Production of Vitamin D
6.       Has the nerve endings for touch, pressure, heat and pain.

Horse skin varies in thickness and toughness.  Chesney has much tougher skin than Basil and so has fewer little injuries.  It takes little for Basil's skin to be damaged and he usually has a few little knicks on his body!

Skin Structure

Skin is very elastic and moves freely over the horse's flesh.  It should feel loose when touched.
The skin has 2 layers; the epidermis which is the outer layer, and the dermis which is the inner layer.

Epidermis: the surface is made of up dead cells, many are shed on a daily basis because cells are constantly dying and being replaced.   The epidermis is also covered with hairs - forming the horse's coat. These hairs and the tubes of the oil and sweat cells pass through the epidermis to the surface - the openings are called pores.  The dead cells (scurf) need to be groomed regularly so that the skin's other functions are not affected.  In the wild the dead cells mix with grease and mud before falling off naturally.  We ask our horses to work hard and work up a sweat, by grooming we are increasing the performance ability of the skin!  At the extremities the epidermis is modified to form the hooves.  

Dermis: this layer is deep and sensitive, it contains blood vessels, nerve fibres, the glands  that produce sweat and oil and the hair roots. The dermis also contains collagen and elastic fibres which give the skin toughness and flexibility.  It contains fat cells (subcutaneous fat) which store energy and provide thermal insulation.  


As mentioned above almost the whole of the horse is covered by hairs.  These hairs grow from the hair bulbs which are deep in the dermis.  The hairs come out at an acute angle so that the coat can lie flat and smooth.  The skin has both permanent and temporary hair.  The permanent longer hair includes the mane, tail, hairs on the lips, nostrils and eyes.  The temporary hair is shed in spring and autumn.  

In addition to the shedding of this temporary hair all permanent hair is shed a little at a time throughout the year and is replaced by new growth.  Every hair has a small gland at the base which exudes oil to lubricate the hair, in addition a tiny muscle is positioned to pull the hair upright.


Skin colour and the coat provide protection from the sunlight.  The skin can be a different colour from the coat - grey horses often have dark skin!  The coat gives protection from brambles, thorns etcetera.  The oil which lubricates each hair also keeps a horses' skin waterproof.

Maintaining Body Heat

As the muscles of the body work they produce heat, excess heat is then lost through the skin.  The sweat glands and blood vessels both play an important part in regulating the temperature of the horse.  The sweat glands are little coiled tubes within the dermis, these continue to the surface as a thin duct - through which the sweat is discharged.  As the sweat evaporates from the skin surface the body cools. 

Hairs lie flat against the skin and so trap the minimum amount of air which then allows the sweat to evaporate more efficiently.  Humid days will reduce the speed of evaporation and if a horse is dripping with sweat then the horse is not losing heat effectively.  It is important to think about how hard you work your horse if it is hot and humid.  This can cause the horse to over-heat, become dehydrated and in extreme conditions can lead to death.

Blood can be diverted to the surface capillaries when the horse is hot to increase the amount of heat that can be radiated.  Conversely blood can be confined to the deeper layers to retain heat.  Blood vessels can be constricted and dilated to decrease and increase the amount of blood flowing which will also aid in controlling heat loss through radiation.  In addition when the blood vessels expand they can also stimulate the sweat glands to work harder!  This is seen when a horse 'lathers up'. 

The hair also keeps the body warm by standing on end in cold weather, this increases the air trapped.  The longer coat in the winter traps even more air!  In the summer, when the coat hair is short, less air is trapped.  Thoroughbreds, like Basil, were bred in warmer countries and so have shorter coats than our native horses such as the Shire!

If a horse is unwell the subcutaneous fat  is reduced and the horse will get cold.  The hairs of the coat will stand on end and this tends to make the coat look dull.

Eliminating Waste

When sweat evaporates it takes waste products with it.  This is important to remember if a horse sweats excessively as it is likely to lose more salts from the body than is necessary.  It is important in these situations to ensure salts are replaced through the horse's diet.  This elimination also means that it is important to keep the pores clear to maximise their effectiveness.  Regular grooming is essential.

Providing Camouflage

Coat colour helps to provide camouflage in the wild by helping the horse to blend into the background.  Zebra stripes help them to hide in the 'brush' and native ponies on the New Forest, Dartmoor and Exmoor are dark colours to help them blend into the foliage!

Production of Vitamin D

As mentioned in my Vitamins blog a few weeks ago sunlight is needed to act on the skin to produce Vitamin D.  Have a look at my blog to see why Vitamin D is important.

Nerve Endings

The nerve fibres are sensitive to touch, hair movement, pressure and pain.  These are connected via nerves to the brain.  I am planning a future blog about the nervous system.

Skin is amazing!

Did you see this week's video 'How to ...  Put on a Stable Bandage'  on my You Tube channel.   
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Until next time!

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