# Anatomy and Physiology of Animals/Glossary/O-P

A-B | C-D | E-F | G-H | I-J | K-L | M-N | O-P | Q,R,S | T,U,V,W,X,Y,Z
| Word | Meaning |
| O | |
| Excessive accumulation of fluid in the body tissues |
| Oesophagus | The hollow muscular tube connecting the pharynx with stomach |
| The female sex hormone produced by ovaries |
| Olfactory | To do with smell |
| Omasum | Part of the modified stomach of ruminants with a folded inner surface |
| Open rooted teeth | Teeth in which the root opening remains wide. They grow continuously e.g. the incisors of rabbits and rats |
| Optic Nerve | The nerve carrying impulses from the retina of the eye to the brain |
| Orbit | The bony cavity in the skull that holds the eyeball |
| Organ | A structure with a specific function |
| Organelle | A structure in the cell with a specific function |
| Organic | A compound that contains carbon and hydrogen e.g. carbohydrates, lipids and proteins |
| Organism | A living form. One individual |
| Origin | The attachment of a muscle to a bone that does not move |
| Osmosis | The movement of water molecules across a semi permeable membrane from an area of high water concentration to an area of low water concentration |
| Osmotic pressure | The pressure required to prevent water moving across a semi permeable membrane by osmosis |
| Ossicle | A small bone |
| Ossification | The formation of bone |
| Otolith | A particle of calcium carbonate embedded in the membrane of the otolith organ of the inner ear |
| Oval window | The small opening between the middle and inner ear |
| Ovarian cycle | The series of events in the ovary associated with the maturation of the ovum |
| Ovarian follicle | The developing ovum with the epithelial tissues surrounding it |
| Ovary | The female gonad that produces ova. |
| Ovulation | The release of the ovum from the mature follicle of the ovary |
| Ovum | The egg cell (plural: ova) |
| Oxyhaemoglobin | Haemoglobin combined with oxygen |
| Oxytocin | The hormone from the posterior pituitary gland. Stimulates milk “let down” |
| P | |
| Palate | The roof of the mouth |
| Palmar | The “walking” surface of the front paw |
| Pancreas | The organ lying along the caudal margin of the stomach. Has endocrine and exocrine functions |
| Pancreatic juice | The digestive secretion produced by the pancreas |
| Parasympathetic division | One of the two parts of the autonomic nervous system. Concerned with normal “at rest” activities |
| Parathyroid gland | One of four small endocrine glands on the dorsal surface of the thyroid gland |
| Parathyroid hormone | The hormone secreted from the parathyroid gland |
| Parotid gland | One of the paired salivary glands ventral to the ear |
| Parturition | The act of giving birth |
| Patella | The kneecap |
| Pathogen | A disease-producing organism |
| Pectoral | To do with the chest or breast |
| Pelvic cavity | The caudal portion of the abdominal cavity. Contains the bladder, colon and reproductive structures |
| Pelvic girdle | The bony structure formed by the hip bones, sacrum and coccygeal bones |
| Pelvis | The structure formed by the two hip bones, sacrum and coccyx |
| Penis | Male sexual organ |
| Pepsin | A protein digesting enzyme secreted by the stomach wall |
| Pericardial cavity | The small cavity between the two layers of the pericardial membranes |
| Pericardium | The membrane that encloses the heart |
| Periosteum | The tough connective tissue covering of a bone |
| Peripheral | Located on the outer part of the body |
| Peripheral nervous system | The part of the nervous system composed of the cranial and spinal nerves |
| Peristalsis | The successive muscular contractions along the wall of the gut |
| Peritoneum | The membrane that lines the abdominal cavity and covers the abdominal organ |
| Permanent teeth | The second set of teeth that persist through life |
| Peyer’s Patches | Large clusters of lymph nodules found in the wall of the small intestine |
| pH | A symbol that indicates the acidity or alkalinity of a solution |
| Phagocytosis | The process by which cells ingest particles and bacteria |
| Phalanges | The bones of the “fingers” and “toes” |
| Pharynx | The throat |
| Phospholipid bilayer | The arrangement of phospholipids molecules in two layers |
| Phospholipids | Molecules that make up the double layer of biological membranes |
| Photoreceptor | A receptor that detects light |
| Photosynthesis | The making of organic molecules by plants using energy from the sun |
| Physiology | The science that deals with the functions of an organism and its parts |
| Pineal gland | The gland situated in the brain that secretes melatoni |
| Pinna | The projecting part of the external ear |
| Pinocytosis | The process by which cells ingest liquid |
| Pituitary gland | The endocrine gland lying under the caudal surface of the brain attached to the hypothalamus by a stalk |
| Pivot joint | A synovial joint where a peg of bone articulates with a ring of bone as in the joint between the atlas and axis |
| Placenta | The special structure through which the exchange of materials between the foetus and mother occurs |
| Plantar | The “walking” surface of the hind paw |
| Plantigrade locomotion | Locomotion involving placing the whole surface of the foot on the ground as in humans and bears |
| Plasma | The fluid that surrounds the blood cells |
| Plasma membrane | The outer membrane surrounding the cell |
| Platelets | Cell fragments in the blood essential for clotting |
| Pleura | Membranes that cover the lungs and line the walls of the chest and diaphragm |
| Pleural cavity | The space between the two layers of the pleura |
| Plexus | A network of nerves |
| Poikilothermic | ‘Cold-blooded’ animals whose body temperature varies, to a large extent depending on the environment |
| Polysaccharides | A carbohydrate formed from up to a thousand monosaccharides |
| Preen | To clean, straighten and fluff feathers |
| Premolars | The more anterior cheek teeth |
| Progesterone | The hormone produced by the corpus luteum |
| Prolactin | A hormone produced by the anterior pituitary gland |
| Prostate gland | The gland caudal to bladder in males |
| Proteases | Enzymes that split proteins into amino acids |
| Protein | An organic compound consisting of carbon, hydrogen, oxygen and nitrogen. Made up of amino acids |
| Proximal | Nearer to the body or to the point of origin |
| Pulmonary | To do with the lungs |
| Pulp cavity | The cavity within the crown and neck of a toot |
| Pulse | The series of waves of high pressure blood passing along an artery |
| Pupil | The hole in the centre of the iris of the eye |
| Pus | Dead white blood cells |
| Pyloric sphincter | The ring of smooth muscle between the stomach and the small intestine |