# Anatomy and Physiology of Animals/Glossary/Q,R,S

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 | Print version
| Word | Meaning |
| R | |
| Radius | The shorter bone of the forelimb between the humerus and the “wrist” |
| Receptor | A specialized cell that responds to specific sensory stimuli such as touch,pressure, light etc. |
| Red marrow | Bone marrow found in the spaces of spongy bone.Makes red blood cells |
| Reflex | A fast automatic response to a stimulus |
| Reflex arc | Consists of receptor, sensory, relay and motor neurons and effector |
| Refraction | Bending of light as it passes from one medium to another |
| Relaxin | The hormone secreted by the placenta and ovaries that eases the joint between the right and left pelvis and dilates the cervix for birth |
| Renal | To do with the kidney |
| Renal pelvis | The cavity in the centre of the kidney |
| Renal pyramid | A cone shaped structure in kidney medulla |
| Renal system | The body system involving the kidneys |
| Reticulum | The part of the modified stomach of ruminants with honeycomb of raised folds on its inner surface |
| Retina | The inner coat of the eyeball. Nerve calls here (rods and cones) respond to light ray |
| Ribosome | The organelle in the cell that makes proteins |
| Rickets | A bone disorder caused by inadequate vitamin D |
| Rod | The photoreceptor in the retina, specialized for vision in dim light |
| Rostral | Towards the muzzle |
| Rumen | The first and largest compartment of the modified stomach of ruminants.It houses the microorganisms |
| Ruminant | An animal with a rumen e.g. sheep, cow, camel |
| Rumination | Chewing the “cud” |
| S | |
| Sacrum | The triangular bone formed from fused sacral vertebrae.Located between the two hipbones |
| Sagittal plane | Plane that divides the body into left and right portions |
| Sagittal section | Lengthwise slice of an animal or organ |
| Saliva | The secretion from the salivary glands |
| Salivary amylase | The starch digesting enzyme in saliva |
| Saturated fat | A fat containing saturated fatty acids |
| Scapula | The shoulder blade |
| Sciatic nerve | The large nerve that passes down the hind leg |
| Sclera | The fibrous outer coat of eyeball |
| Seasonal breeding | Breeding confined to certain seasons of the year |
| Sebaceous gland | An exocrine gland in the dermis of the skin associated with a hair follicle |
| Sebum | The waxy secretion from a sebaceous gland |
| Secondary sex characteristic | A characteristic that develops at sexual maturity. e.g. large body size of males, manes in lions |
| Secretion | The production or release of a fluid from a gland |
| Semen | The fluid discharged at ejaculation of male. Consists of sperm and fluid |
| Semicircular canals | The membranous fluid filled canals containing receptors for equilibrium |
| Semilunar valve | The valve guarding the entrance to the aorta or the pulmonary artery |
| Seminal vesicle | A gland that secretes a component of semen |
| Seminiferous tubule | The tightly coiled duct in the testis where sperm are produced |
| Semi-permeable membrane | A membrane that allows some substances to cross more easily than others |
| Sensory neuron | A neuron that carries a nerve impulse towards the central nervous system |
| Serum | Plasma minus its clotting proteins |
| Sesamoid bones | Small bones usually found in tendons |
| Shock | Reduced cardiac output resulting in failure to deliver adequate oxygen and nutrients to the body |
| Shoulder | The synovial joint where the humerus joins the scapula |
| Sinus | An air cavity in a bone especially in the bones of the face or skull |
| Skeletal muscle | Tissue specialized for contraction with striated fibres. Attached to the bones of the skeleton |
| Skull | The skeleton of the head |
| Small intestine | The long tube of the gut that begins at the stomach and ends at the large intestine |
| Smooth muscle | Tissue specialized for contraction with spindle shaped non striated fibres |
| Soft palate | The posterior portion of the roof of the mouth |
| Solution | One or more substances dissolved in a liquid |
| Specific gravity | A measure of the density of a liquid or solid, as compared with that of water. |
| Sperm duct | The tube that carries sperm from the epididymis to the urethra. Also called the vas deferens |
| Spermatic cord | The structure in the male reproductive system attached to the testis that carries the vas deferens, arteries, veins, etc. |
| Spermatozoon | A mature sperm cell |
| Sphincter | A ring-like muscle that controls movement along a body passage or orifice |
| Spinal cord | The mass of nerve tissue in the vertebral column |
| Spinal nerve | One of the nerves that originate in the spinal cord |
| Spleen | The large lymphatic organ near the stomach that stores blood and produces lymphocytes |
| Spongy bone | The inner layer of bone; found at the ends of long bones less dense than compact bone |
| Squamous | Scale like |
| Starch | The storage polysaccharide in plants consisting of many glucose molecules |
| Sterile | Free from any living micro organisms |
| Sternum | The breastbone |
| Stifle | The joint between the femur and the tibia on the hind leg |
| Stimulus | Any change in the environment capable of initiating a nerve impulse |
| Stomach | The large baglike part of the gut between the oesophagus and the small intestine |
| Striated muscle | Striped or skeletal muscle |
| Subcutaneous | Beneath the skin |
| Submandibular gland | The salivary gland beneath the tongue |
| Substrate | A substance on which an enzyme acts |
| Sulcus | A groove or depression between the convolutions of the brain |
| Superficial | Nearer to the surface of |
| Suture | An immoveable joint in the skull |
| Sympathetic division | One of the two subdivisions of the autonomic nervous system concerned with reacting to emergency situations |
| Synapse | The junction between two neurons |
| Synovial joint | A fully moveable joint |
| System | An association of organs that have a common function, e.g. digestive system, respiratory system |
| Systemic circulation | The blood circulation from the left ventricl through the aorta to all the organs of the body and back to the heart |
| Systole | The phase of the heartbeat involving contraction of the ventricles |
| Systolic blood pressure | The blood pressure during passage of the pulse |
| Synapse | The junction between two neurons |
| Synovial joint | A fully moveable joint |