The rumen is the first chamber of the ruminant stomach. It is the largest chamber and has regular contractions to move food around for digestion, eliminate gases through eructation and send food particles back to the mouth for remastication. The rumen breaks down food particles through mechanical digestion and fermentation with the help of symbiotic microbes. Volatile fatty acids are the main product of ruminant digestion.

The ruminant stomach is composed of 4 separate compartments. Food passes first into the rumen, then reticulum, omasum and finally into the abomasum before entering the duodenum. The first three compartments are adapted to digest complex carbohydrates with the aid of microorganisms which produce volatile fatty acids - the major energy source of ruminants. The last compartments, the abomasum resembles the simple monogastric stomach in structure and function.

The information gained through the study of disease in populations which will be increased if more members of the population are sampled. However, the sampling of every individual in a population is rarely feasible from either a logistical or an economic perspective (except in the case of very small-scale studies). Censuses are a form of descriptive study which aims to systematically collect information about every member of the population of interest (the source population), and are carried out in many countries for both livestock as well as for humans (although information regarding disease may not be collected). Statistical surveys are another type of descriptive study, which aim to select a sample (known as the study sample) from the source population, with the intention of extrapolating the information about these individuals to the source population. Similarly, in most analytic studies, a sample of the population must be selected for the same reasons.

Sensory information from the periphery of the animal ascends through the spinal cord and enters the higher levels of the brain. There are numerous pathways which allow different types of information to be passed to the brain. Types of general somatic sensation include pain, touch, temperature and kinaesthesia (conscious proprioception). This sensory information is sent to one of two destinations; the cerebral cortex or the cerebellum.

The epidermis is a stratified squamous epithelium and is composed of 4 cell layers anchored to a basal lamina of connective tissue. Keratinocytes migrate through the epidermis from the basal layer. This migration begins in the stratum basale, then moves up through the stratum spinosum, stratum granulosum and the stratum corneum.

Hormones have a large effect on the skin, details of which can be found at endocrine and nutritional influences on the skin. As a result, endocrine associated skin pathology is relatively common.

The small intestine extends from the pylorus of the stomach to the caecum. The small intestine recieves chyme from the stomach. It is the main site of chemical degradation and absorption of chyme. Fats are exclusively broken down in this part of the alimentary tract. Carbohydrates and proteins that are not degraded in the small intestine are available for microbial fermentation in the large intestine. The small intestine produces enzymes for digestion of protein, carbohydrate and fat and absorbs the products of their digestion. Enzymes are produced by glands in the intestinal wall and the pancreas. The gall bladder produces bile which emulsifies fats for digestion. Absorption is facilitated by ridges in the small intestine and by the presence of villi and microvilli.

n the verterbrate embryo, as the primitive streak is regressing, the paraxial mesoderm divides into blocks of cells called somites. These divisions can be seen either side of the notochord. Somites are transient structures that will give rise to cells of the vertebrae and ribs, dermis of the dorsum, skeletal muscle of the body wall, back and limbs. Somites begin to develop at the anterior of the embryo first, and appear at regular intervals.

Fusion of the two plates of the thyroid cartilage is incomplete forming a rostral pointing notch which is a good site for surgical entry into the larynx. The thyroarytenoid muscle is divided into 2 parts; the rostral and caudal vocalis, which are situated within the vocal folds and vestibular folds. The cuneiform processes are attached to the epiglottis.

The spinal cord is constructed of the marginal layer which has axons and white matter, the mantle which contains cell bodies and grey matter and the spinal canal. This canal conducts sensory information from the peripheral nervous system (both somatic and autonomic) to the brain, conducts motor information from the brain to various effectors and acts as a minor reflex center.

Epidemiological studies can be described as belonging to one of two categories: descriptive or analytical. Descriptive studies involve detailed investigations of individuals in order to improve knowledge of disease. Descriptive studies often have no prior hypotheses and are opportunistic studies of disease whereas analytical studies are used to test hypotheses by selection and comparison of groups. However, data obtained from analytical studies can be used in a descriptive manner and vice versa.

This page explains superficial anatomy through a guide to the superficial anatomy of a dog, including the head, forelimb, and hindlimb. Detailed Illustrations open in new tab.

Monitoring of the epidemiological patterns (animal, place, time) of diseases and pathogens within populations provides a vital system for the identification of changes in disease status within this population (whether this relates to all animals worldwide, or those within a single country, region, village or farm). For this reason, most countries have systems in place for the intermittent collection and collation of data relating to disease. Monitoring of production levels also provides a method of informing farmers about the productivity of their animals. These processes can be described as monitoring systems.

T cells are so named as they differentiate in the thymus. They are long lived and are involved in cell mediated immunity. They represent 60-80% of the circulating lymphocytes and all express the markers CD2, CD3 and CD7 as well as having T cell receptors (TCR). Each T cell has 30,000 TCRs each of which is identical and recognises antigens and major histocompatability complex (MHC) II.

T cells are long lived and are involved in cell mediated immunity. Functionally they are divided by the expression of CD4+ or CD8+ markers. CD4+ T helper cells recognise antigens bound to MHC II complexes and are involved with the control of intracellular and extracellular pathogens; they can interact with CD8+, NK and dendritic cells or with B cells. Cytotoxic CD8+ T cells recognise the MHC I complex and destroy infected or neoplastic cells.

Thermoregulation is the ability of an endothermic organism to maintain a relatively constant body temperature, despite fluctuations in temperature of the external environment. This is a vital part of homeostasis.

Thrombocytes are small anuclear fragments of megakaryocytes. They are membrane bound portions of the megakaryocyte cytoplasm and have a finely granular cytoplasm; they are much smaller than other blood cells at 2-3ľm and have a lifespan of around 10 days in the circulation.

As with erythrocytes, thrombocytes are derived from multipotential myeloid stem cells (CFU-GEMM). In the bone marrow CFU-GEMM cells differentiate into the megakaryocyte precursor cell the megakaryocyte CFU (CFU-Meg), under the influence of cytokines CFU-CSF and IL-3. Unlike other blood cells which undergo mitosis in the first few developmental stages, once the CFU-GEMM has differentiated into the CFU-Meg there is no further mitosis. The CFU-Meg then develops into the megakaryoblast.

The thymus has a key role in the maturation of prothymocytes into mature T cells. In juvenile animals the thymus produces significant numbers of new T lymphocytes but as the animal matures this production decreases and T cell population is maintained by division of mature T cells.