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

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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