The thyroid gland lies in the neck, in front of the upper part of the trachea. Two types of hormones are produced, which are the iodine containing hormones; tri-iodothyronine(T3) and thyroxine (T4). Thyroid hormones regulate the basal metabolic rate and are important in the regulation of growth of tissues, particularly nervous tissue. Release stimulated by TSH from the pituitary. The second type of hormone produced from the thyroid gland is calcitonin, which regulates blood calcium levels along with parathyroid hormone and acts to reduce blood calcium by inhibiting its removal from bone.

Teeth develop differently in different regions of the mouth in most species, a process called heterodonty. In some animals, teeth develop identically in different regions of the mouth, a process called homodonty. Different species will have varying numbers of teeth and different shapes depending largely on their diet. Not all species possess teeth and there is huge variation in dental formulae between the species that have teeth. Teeth are mainly used for mastication - chewing and grinding food particles, but are also used for seizing prey and tearing. The occlusion surface is where opposing teeth touch. The contact surface is where adjacent teeth touch.

The trachea is the tube linking the cricoid cartilage of the larynx to the bronchi, forming part of the conducting system which transports air from the external environment to the lungs. The oesophagus lies dorsally to the trachea. The cervical part of the trachea lies generally in the median position, although this varies slightly depending on the position of the head. The thoracic part of the trachea crosses the aortic arch, thus its positioning is moved slightly to the right at this level. The trachea bifurcates to form the two bronchi at the level of the 4th-6th intercostal space.

Hydrophillic ions and molecules are unable to diffuse across the lipid bilayer. However if concentration gradients allow it they are sometimes able to diffuse across the membrane using water filled protein channels. These tend to be only large enough for small ions to pass through and so are perhaps more commonly known as ion channels.

The urinary system includes the kidneys, the ureters which join the kidneys to the bladder, the bladder itself and the urethras which permit urine collecting in the bladder to be excreted - a process termed micturition. Understanding the physiology of kidney function is key when looking at the diseases that occur in this organ, and the anatomy of all the structures within the urinary sytem is significant as a foundation to understanding the pathology which affects them.

The Uterus is the organ of pregnancy as this is where implantation and development of the feotus occurs. The Uterus is the reproductive organ with the most species variations. These variations occur in both the anatomical types of uterus as well as the uterine horn appearance and endometrial linings.

The vagina constitutes the part of the female reproductive tract between the cervix and the vulva. With the vestibule and vulva, it is the copulatory organ and the birth canal. The hymen is the poorly developed, vestigial, mucosal folds at the junction of the vagina and vestibule.

Blood vessel formation is a combination of the following three processes: Vasculogenesis: the formation of blood vessels from endothelial progenitor cells; Angiogenesis: the sprouting of new capillaries from pre-existing vessels; and Arteriogenesis: the remodelling of newly formed or pre-existing vascular channels into larger and more muscular arterioles.

The hindlimb deep veins are very closely related to their respective arteries. Essentially the lay out of the veins is similar in all domestic species.

Ventilation is the movement of air into and out of the lungs. Air moves from high pressure to low pressure with the rate of flow being proportional to the pressure difference. As environmental pressure is generally constant, the respiratory system must change its internal pressure to maintain air flow. The lungs are not fixed to the thoracic wall, but follow the changing volume of the thoracic cavity thanks to the pleura.

Welcome to the Anatomy and Physiology section of WikiVet. Anatomy is the study of form and structure of organisms, whilst physiology is the study of the function of an organism and the processes, physical, chemical and biological, occuring within it. Here we cover all the anatomical and physiological points that make up our domestic species and exotic species.

Veterinary epidemiology is principally concerned with the study of disease within populations (although it may also be used for investigation of issues such as animal welfare and productivity). Put simply, it involves the investigation of patterns of disease within a population, in relation to which animals are affected, the spatial distribution (i.e. location) of affected animals, and the temporal distribution of affected animals (i.e. patterns of disease through time).

The principles of veterinary epidemiology are identical to those of human epidemiology, with the exception that they are applied to animal populations rather than human populations. As such, veterinary and human epidemiology can be viewed as forms of the same overarching discipline of epidemiology. Epidemiology is principally concerned with the investigation of disease within populations (although the same principles are also applicable to investigation of other characteristics, such as animal welfare or productivity), and is based on the concept that disease often does not occur in a random fashion. That is, various characteristics of the animal, the pathogenic agent (or agents) and the environment interact in order to alter the probability of disease occurrence. Epidemiology aims to identify these factors and to describe disease in the population.

Volatile fatty acids are the main energy source for ruminants, providing approximately 70% of the total energy requirements. They are used primarily by the microorganisms for reproduction and growth, with the excess production being used by the ruminant itself.

The vomeronasal organ is also known as the olfactory organ, or the Jacobson's organ. It is an olfactory sense organ that is found in most animals. It is positioned at the base of the nasal cavity, within the roof of the mouth, and is separated into two parts by the nasal septum. It is situated close to the vomer and nasal bones, hence the name vomeronasal organ.

Vomiting has potentially lethal effects in the monogastric animal. The effects are listed below. It is clinically important to differentiate vomiting from regurgitation, as clients can often confuse these clinical signs and the two have very different aetiologies.