The study of animal anatomy and physiology involves many terms which are not commonly used in daily communication.

A – C

Abdominal cavity: in vertebrates that part of the body cavity containing the digestive organs, and in mammals separated from the thoracic cavity by the diaphragm.

Absorption: the passage of material into a cell; the passage of nutrients from the intestines into the blood vessels associated with them.

Acclimation: the habituation of an organism or animal to another climate i.e. becoming acclimatised e.g. as in behaviour.

Achondroplasia: shortening of long bones of the limbs caused by a disturbance in the ossification process (bone formation) during growth of the bone.

Acid-base balance: the maintenance of the correct ratio of acids to bases in the blood to maintain the correct pH.

Acquired behaviour: behaviour brought about by conditioning and learning.

ACTH: Adrenocorticotropic hormone.

Aerobic: in oxygen – usually refers to organic chemical reactions or to microorganisms that operate in the presence of oxygen.

Amoeba: a protozoan the shape of which is subject to constant change due to its ability to form and retract limb like projections which aid its mobility.

Amoeboid: resembling an amoeba in shape, in properties or in locomotion.

Anabolism (anabolic): the constructive chemical processes in living organisms that involves the formation of complex molecules from simpler ones, and the taking up and storage of energy.

Anaerobic: without oxygen; usually refers to organic chemical reactions or microorganisms that operate in the absence of oxygen.

Anagen: the growth phase of feathers.

Anastomosis: joining together of adjacent tubes e.g. bronchi.

Anatomy: the science of the structure of plants and animals as observed by dissection i.e. how they are constructed.

Anterior: nearer the head end; facing outwards from the axis.

Articulate: to form a mobile joint usually with two surfaces in contact or close association.

Blastodisc: the group of cells on the yolk of the egg from which the embryo develops.

Blastoderm: see blastodisc.

Binocular: with two eyes. Being able to see the same object or field with both eyes at the same time. This facilitates the perception of range or distance.

Bolus (boli): the ball of food at swallowing.

Catabolism (catabolic): the breaking down of complex organic molecules by living organisms with the release of energy (as in cells).

Caudal: towards the tail end or posterior.

Choanal opening: the opening from the nasal cavity into the roof of the mouth. Choanal means ‘funnel-like’.

Coelom: the cavity that develops very early in the embryo that later becomes the pericardial, pleural and peritoneal cavities.

Columnar (epithelium): cells that are very long i.e. longer than they are broad; like a column.

Conical: cone-like.

Corium: deep-seated layer of the skin or lining.

Cranial: towards the head end.

D – F

Dimorphism: having two different forms because of sex e.g. the males and females are different in appearance.

Distal: the part of any structure furthest from the middle line of an organism or from the point of attachment.

Dorsal: towards the back or dorsal surface.

Ectoderm: the outer layer of embryo cells.

Electrolyte: the name given collectively to many common salts in the body e.g. sodium chloride, potassium chloride.

Endocardium: membrane lining the interior of the heart.

Endoderm (entoderm): Inner or bottom layer of cells of an embryo from which systems such as the digestive system and its glands and the respiratory system develop.

Entoderm: see endoderm.

Epithelium: any cellular tissue covering a free surface or lining a tube or cavity; the skin.

G – I

Gamete: haploid cells that fuse to form the zygote; cells with half the chromosomes that join at fertilisation to form the complete embryo.

Germ disc: see blastodisc.

Gonads: sex organs; ovaries in the female and testes in the male.

Gonadotropins: hormones (follicle stimulating hormone and luteinising hormone) secreted by the pituitary gland that affect the function of the sex organs or gonads.

Heterophilic: either acidic or basic in reaction.

Homeothermic: animals that regulate their temperature to maintain a generally constant temperature of their deep organs.

Hyperthermia: body temperature above the normal.

Hypothermia: body temperature below the normal.

Ingest: to convey food into the alimentary canal; to eat.

Infection: invasion of the body by infectious agents such as bacteria or viruses which usually cause a disease condition.

Infestation: invasion of the body either internally or externally by parasites e.g. lice and worms.

J – L

Lateral: towards the side or situated at the side.

Longitudinal: lengthwise; along the length of the body.

Lunar: the moon; semi-lunar (half moon) e.g. types of valves found in the heart.

M – O

Median: along the middle of the long axis.

Meiosis: the process of reduction division of cells that produces sex cells with one of each pair of the bird’s chromosomes in the sperm and ovum. Chromosomes occur in pairs and one of each pair is supplied by each the male and female to form the normal complete cell(s) on fertilisation.

Metabolism: the chemical changes, both constructive and destructive, occurring in living organisms.

Mitosis: the process of cell division or replication whereby daughter cells are produced that have the same chromosome make-up as the original cell(s).

Mesoderm: the layer of embryo cells developing between the endoderm and the ectoderm.

Myocardium: the muscle tissue of the heart.

Neo: new; as in the respiration cycle.

Ovum: the female gamete; that part of the egg yolk fertilised by the sperm.

P – R

Paleo: old; as in the respiration cycle.

Papilla (papillae): a nipple or pimple like structure often associated with ducted glands.

Peri: around.

Pericardial: to do with the heart i.e. around the heart.

Peritoneal: to do with the intestines and/or abdomen.

pH: a term based on a mathematical formula that describes the acidity/alkalinity of a solution. Neutral is 7, acid below 7 and alkaline above 7. Pure water is neutral.

Phagocyte: a white blood cell with the ability to engulf and consume foreign bodies e.g. bacteria.

Physiology: dealing with the function and activities of organisms i.e. how they work.

Plantar: the sole of the foot.

Pleural: to do with the lungs.

Poikilothermic: animals that do not maintain a relatively constant deep body temperature and as a result, their body temperature varies with their environmental temperature.

Polymorphonuclear: poly = many; morpho = shape; nuclear = nucleus i.e. cells with a many shaped nucleus.

Posterior: located behind; facing back; behind the axis.

Proximal: the part of any structure nearest to the middle line of the organism or point of attachment.

Pulmonary: to do with the lungs e.g. pulmonary veins drain the lungs.

Purkinje fibres: special muscle fibres found in hearts that have a higher rate of conduction of the contractile impulse. They transmit the impulse at a faster rate.

S – U

Sagittal: section or division in the median longitudinal plane. Cut along the length of a system, organ or tissue.

Sebaceous: containing or secreting fatty matter.

Serous (membrane): very thin membrane of connecting tissue.

Squamous: special type of flattened cell.

Stratified epithelium: epithelium cells arranged one layer on top of the other.

Syncytium: a mass of protoplasm with multiple nuclei but without differentiation into separate cells.

Telogen: the resting phase of feather growth.

Thoracic (cavity): that part of the body cavity carrying the heart and lungs. In mammals it is separated from the abdominal cavity by the diaphragm.

Transverse: lying across or between.

V – Z

Ventral: towards the lower or abdominal surface.

Virulent: ability to cause disease.


Further information

  • Holmes, Sandra. (1985) Henderson’s Dictionary of Biological Terms, 9th Ed. Longman, London.