The abomasum is the fourth chamber in the ruminant. It functions similarly to the carnivore stomach as it is glandular and digests food chemically, rather than mechanically or by fermentation like the other 3 chambers of the ruminant stomach.

Active transport is reliant on carrier proteins and thus follows the same rules as facilitated diffusion in that they are specific have a maximum rate and are subject to competition. Crucially they transport substances against their concentration gradient and so require energy to work.

The adrenal glands are paired bodies lying cranial to the kidneys within the retroperitoneal space. The glands consist of two layers; the cortex and medulla.

Aldosterone is a steroid hormone which is secreted from the zona glomerulosa of the adrenal gland. It has a mineralocorticoid activity and is the most important regulator of plasma potassium. When plasma potassium increases, increased stimulation of aldosterone occurs directly and also as a result of the Renin-Angiotensin-Aldosterone System (RAAS). Aldosterone is also the most important regulator of sodium excretion.

The horse is a monogastric hindgut fermenter. The horse evolved for grazing and it does so for up to 17 hours a day. A high proportion of the horse's dietary carbohydrate is in the form of starch. A mature horse eats 2-2.5% of it's body weight in dry matter every day, 1.5-1.75% of this should be fibre (hay/haylage). This is to prevent a rapid drop in pH in the large intestine and also to stimulate peristalsis in the gut and prevent build up of gas.

Gives an overview of the anatomy and physiology of mammalian and avian animals' alimentary systems.

Because small mammals are prey species, they do not take to intensive conditions of surgery and hospitalisation very readily. Those that are handled very frequently by their owners are more bonded with humans and better surgical subjects as a result. Rodents and rabbits are particularly susceptible to the surgical complications of dehydration (blood and fluid loss), core temperature depression, hypovolaemic shock, ileus and renal and respiratory depression.

Analytic epidemiological studies aim to investigate and identify factors associated with the presence of disease within populations, through the investigation of factors which may vary between individual members of these populations. Details on study designs appropriate for these investigations are given elsewhere. Conceptually, this involves investigating the disease experience amongst different 'groups' of animals within an overall population, distinguished according to the factor(s) of interest. These factors can be classified as one of the components of the 'epidemiological triad' of Host, Agent and Environment, many of which are closely interrelated with each other.

The anus is the terminal portion of the alimentary tract which communicates with the external environment. Two sphincters control it's aperture. It allows faeces and gas to leave the body. Defeacation is the process where faeces are expelled from the rectum through the anus.

After emerging from the heart, the aortic artery divides into the right and left dorsal branches. Each branch feeds into a set of arches which are unique to the embryo. Most higher vertebrates have have 6 pairs of aortic arches. In the mammal the 5th pair do not form. These arches evolve to form some of the structures of the mammalian circulation. The fate of each arch varies.

Although the information on this page is based around the anatomy of the canine hindlimb, it is essentially the anatomy of the arteries in domestic species. Any major differences will be discussed on their respective pages

The peripheral nervous system found in most domestic species can be segregated into three sub-systems; the sensory system, the somatic motor system and the autonomic system. The autonomic nervous system (ANS) regulates the internal environment of the body including factors such as body temperature, blood pressure and concentrations of many substances. The ANS is also responsible for mobilising the body's resources during stressful situations. The ANS controls gland cells, cardiac muscle cells and smooth muscle cells. Control of this nervous system is involuntary and regulation is via autonomic reflexes. The autonomic reflex arc system is very similar to that of the somatic motor system, i.e. there are sensory (afferent) nerve fibres, an information integration centre, motor (efferent) fibres and effector cells. Any levels of increased activity within the autonomic nervous system can result in both stimulation or inhibition of effector cells, although it is only the efferent part of the reflex arc that is actually considered autonomic.

The intestines occupy the caudal part of the body. They contact the reproductive organs and the gizzard. The small intestine is long and relatively uniform in shape and size. There is no demarcation between the jejunum and the ileum.

So named as they were initially found in the Bursa of Fabricius, B cells produce antibodies and are associated with humoral immunity (T cells are part of the cell-mediated immune response), and are an integral part of the adaptive immune system. They represent 20-30% of circulating lymphocytes.

Basophils are derived from the same stem cell line as mast cells and while they are similar to mast cells, they are not identical (they are thought by some to be immature mast cells). They are the least common of all the leukocytes, are a similar size to neutrophils and eosinophils and are characterised by the large number of basophilic staining granules in their cytoplasm. They are present in the circulation but rarely found in tissue.

Mature B cells that undergo stimulation by an antigen undergo class switching, and differentiate into either plasma or memory cells. In the paracortex region of the lymph node binding to MHC II in the presence of IL-4 produced by the CD4+ T cells (TH2 type) causes the B cells to differentiate; most will become plasma cells, however a small number will become memory cells. Follicular dendritic cells present in the germinal centers of peripheral lymphoid organs can absorb intact antigen onto their surface to present to B cells to stimulate differentiation.

Systematic error, or 'bias' is of particular importance in any epidemiological investigation, and should be avoided wherever possible. Biases will reduce the validity of any results obtained, whether it be by overestimating or underestimating the frequency of disease in a population or the association between an exposure and disease. The forms of bias covered here can only be minimised through careful study design and execution - they cannot be accounted for in the analysis. Although confounding is considered by many authors as a form of bias, it can be accounted for during analysis, and so is covered separately.

Bile formation is an osmotic secretory process that is driven by the active concentration of bile salts in the bile canaliculi. Bile acids are produced from cholesterol and prior to being excreted from hepatocytes are bound to specific amino acids allowing them to exist as bile salts. One side of the bile salt molecule is negatively charged (hydrophilic) whilst the other is hydrophobic allowing bile salts to form micelles once a certain bile salt concentration has been reached.

Once sperm has entered the the oocyte, an ootid is formed. During early stages the ootid will contain male and female pronuclei along with the first and second polar bodies. Fusion of the male and female pronuclei will result in a single diploid nucleus or syngamy. Once syngamy has occurred, the zona pellucida then develops into an imprenetrable layer that prevents polyspermy and so polyploidy. Once the zona pellucida has developed, the ootid is now referred to as a zygote (diploid) and will begin undergoing mitotic divisions via a cleavage process that will begin to give rise to daughter cells called blastomeres. These cleavage divisions will begin to produce a 4-celled embryo and then an 8-celled embryo.