Equine Anatomy

body is organized of

tissues, organs, and systems

tissues: group of similar cells

organs: tissues function together

organ system: group of organs with similar overall function

skin and coat of horse

-protect the internal systems from injury
-protect body from dehydration
-for vitamin D synthesis (can store)
-assist with temperature regulation
-also very important for sensation (touch)

sweating

very efficient at sweating and dissipate a great deal of heat through sweat

-some have a anhidrosis where they cannot sweat, and have difficulties performing athletic activities because of it

urinary system

remove wastes from blood and to expel them from the body via the urine
-also facilitates maintenance of blood pH

respiratory system

functions to facilitate the exchange or oxygen and carbon dioxide
-two main components of respiration: external respiration and internal respiration
-structures include upper airway, consisting of nostrils, nasal cavity, nasal septum, turbinate bones, sinuses, pharynx, soft palate, epiglottis, larynx, and trachea
-lower airway consists of trachea and lungs, with the bronchi, bronchioles, and alveoli, as well as the diaphragm

nasal cavity

can cool or warm air as it goes through

pharynx

exchange of air going in trachea v food in esophagus

sinuses

help skull be light
-vascular cartilage tissue, warms air and cools blood
-put out some hot air

hard palate and soft palate

-obligate nasal breather (only breath through nose)
-epiglotis and artyneoids

external respiration

breathing

internal respiration

oxygen use at the cell

breathing

controlled by respiratory center in the medulla oblongata of the brain that detects changes in oxygen, carbon dioxide, and pH
-breathing is also under some voluntary control, such as for phonation (vocalization) and during efforts such as parturition and defecation
-when they run at the gallop, respiration is coupled to locomotion, such that a horse will take a breath with each stride

roaring

condition called laryngeal hemiplegia
-a result of paralysis of left arytenoid cartilage
-results in cartilage flapping in the airway causing a roaring noise during exercise and potentially inhibiting airflow
-there is a surgical treatment called "tie back" that is very effective

Doral Displacement of Soft Palate

-soft palate displaces and sits on top of epiglottis -obstructs airway
-usually intermittent (massage neck)
-treatment
*nosebands
*surgery

exercise induced pulmonary hemorrhage (EIPH)

-condition seen in racehorses or other highly athletic animals
-intense exercise, pressure within pulmonary capillaries increases to a point that can rupture the vessel walls, causing blood to leak into the alveolar sac and exit via the nostrils (when blood is observed at the nostrils is is called epistaxis)

heaves

-chronic obstructive pulmonary disease (COPD) and is very similar to asthma in humans
-restricts bronchi, inflamed
-abdominal muscle show heave line
-caused by irritants to the respiratory tract such as molds and dust, often removal of such irritants by having the horse live outdoors is good management practice
-bronchodilators

circulatory system

-functions to supply the body with nutrients and remove wastes
-involves heart, arteries (carry blood away from the heart), veins (carry blood to the heart), and capillaries (that facilitate gas and nutrient exchange at the tissues and lungs)
-blood is pumped through the arteries and capillaries due to the pumping action of the heart
-blood is returned to the heart via one-way valves on the veins, muscular contractions facilitating movement of blood through the veins, and by the action of the digital cushion in the horse's hooves that help push blood back up to the heart

blood

accounts for ~9% of horse's body weight (good for donors and research)
-approximately 80% of blood in the systemic circulation and 20% in the pulmonary circulation
-most of blood is located within the veins
-components:
*RBC
*WBC
*platlets
*plasma

hematocrit (PCV)

is % of RBC in the blood
-with stress, the amount of RBC increase, thus increasing the hematocrit
-because of horse's spleen that functions to store and release RBC as needed

-30-45% is normal
-decrease if anemic
-increase in stress or dehydration

blood samples

easily taken from a horse from jugular vein
-specialized collection tubes may contain anticoagulants for the collection of plasma (stops the clotting) or no anticoagulant for the collection of serum

control systems

nervous and endocrine
-both function to maintain homeostasis within the body
-respond to stimuli and react accordingly

nervous system

includes brain, spinal cord, and nerves

endocrine system

includes glands (hypothalamus, pituitary, adrenal glands, thyroid, parathyroid, thymus, pancreas, ovaries/testes) and the hormones they produce

sight

-wide range of vision due to placement of eyes on the side of their heads
-mostly monocular vision (field seen with only one eye)
-small area of binocular vision (field seen with two eyes, which is required for depth perception)
-have a blind spot immediately in front of them (small, right between their eyes and close to their face) and immediately behind them
-horses have good night vision because of their tapetum lucidum, which helps to reflect light within the eye
-horse's eyeball is flattened in shape, which allows to focus both on near and far objects easily

-usually brown
-oval horizontal pupil
-corpora nigra (visor)
-sclera (white of eye)
-3rd eye lid (first one to retract)
-can't see above them