A blood clot is the product of blood coagulation which is a mechanism whereby in case of an injury to a blood vessel, greater blood loss can be prevented. A network of fibrin, platelets and red blood cells fill the opening in the damaged vessel. Disorders of the blood clotting system can lead to an increased risk of bleeding on the one hand (reduced activity) or to the risk of a 'spontaneous' clot (thrombus) forming within an undamaged vessel (obstructive clotting or thrombosis).

Blood that is saturated with oxygen that is being carried from the lungs to tissue. As its name suggests, arterial blood is generally found in blood vessels known as arteries, between the lungs and the heart it is in the pulmonary vein. Due to its high oxygen content, it is bright red in colour.

Blood with a low oxygen content and high carbon dioxide content that is on its way back from tissue towards the heart and the lungs. Between peripheral tissue and the lungs, it is found in the veins, between the heart and the lungs in the pulmonary artery. The low oxygen content make it dark red in colour.

Venous blood is sampled for most medical blood tests. Typically, the easily accessible jugular vein is used for obtaining a blood sample.

The withdrawal of blood from the body as a form of therapy. Blood, sometimes in large quantities, is drawn through a phlenotomy incision (an opening in a vein, these days with a large gauge needle, historically with a special phlenotomy knife), with the aim of curing or preventing a disease. This was/is performed mainly in cases of acutelaminitis.

A protective vest made from shock absorbing polystyrene foam covered in material and attached to the body with zips or velcro straps. Body protectors typically cover the back, sides, and chest of the rider, some include attachments for the shoulder and upper arms. Body protectors can reduce injury to the rider in case of a fall by absorbing some of the force of impact. In many countries they are subjected to regular testing by safety standards organisations and are certified to various levels of protection. Wearing of body protectors is mandatory in certain equestrian sports such as racing and eventing.

The internal temperature of an organism. In the horse the normal body temperature is 37.5-38.0°C. The body temperature of a horse is measured rectally.

A distension of the tarsocrural (tibiotarsal) joint (the uppermost joint of the hock) which is characterised by three fluctuating swellings on the dorsomedial, medioplantar and lateroplantar aspects of the joint. This disease my be unassociated with lameness, heat or radiographic change. In such cases, the cause is simply an increased production of joint fluid due to low grade synovitis (inflammation of the membrane lining the joint pouch).

A single, large dose or portion. A bolus can refer to a single large dose of a drug, or a distinct mass moving through the gastrointestinal tract.

The angle between the dorsal surface and the solar margin of the distal phalanx (coffin bone). This is evaluated on a lateral radiograph.

Bone marrow is the tissue found in the interior of bones. It is responsible for the production of red and white blood cells. There are two types of bone marrow: red bone marrow (high proportion of blood building cells) and yellow bone marrow (high proportion of fatty tissue). At birth, all bone marrow is red; with increasing age, this is gradually converted to yellow marrow. In adults, red marrow is predominantly found in flat bones (pelvis, sternum, ribs etc.) whereas the medullary cavity is filled with yellow marrow.