Cells, Organs & Tissues, TOO-YT
Even if you feel you have nothing in common with a stinkbug or a ficus, you're guaranteed to share one crucial aspect of life with these beings: you are all made up of cells, the fundamental molecules of life, of which all living things are composed. As an individual unit, the cell is capable of metabolizing its own nutrients, synthesizing many types of molecules, providing its own energy, and replicating itself. In a multicellular organism, cooperative assemblies of similar cells form tissues, and a cooperation between tissues in turn forms organs, which carry out the functions necessary to sustain the life of an organism.
Cells, Organs & Tissues Encyclopedia Articles By Title
tooth
tooth, any of the hard, resistant structures occurring on the jaws and in or around the mouth and pharynx areas......
tooth germ
tooth germ, embryonic tooth, derived from the mesodermal (middle) and ectodermal (outer) layers of embryonic tissues.......
touch reception
touch reception, perception by an animal when in contact with a solid object. Two types of receptors are common:......
trachea
trachea, in vertebrates and invertebrates, a tube or system of tubes that carries air. In insects, a few land arachnids,......
tracheid
tracheid, in botany, primitive element of xylem (fluid-conducting tissues), consisting of a single elongated cell......
transfection
transfection, technique used to insert foreign nucleic acid (DNA or RNA) into a cell, typically with the intention......
transferrin
transferrin, protein (beta1 globulin) in blood plasma that transports iron from the tissues and bloodstream to......
transformation
transformation, in biology, one of several processes by which genetic material in the form of ânakedâ deoxyribonucleic......
transient receptor potential channel
transient receptor potential channel, superfamily of ion channels occurring in cell membranes that are involved......
transpiration
transpiration, in botany, a plantâs loss of water, mainly through the stomata of leaves. Stomatal openings are......
trapezius muscle
trapezius muscle, large, superficial muscle at the back of the neck and the upper part of the thorax, or chest.......
triceps muscle
triceps muscle, any muscle with three heads, or points of origin, particularly the large extensor along the back......
trichocyst
trichocyst, a structure in the cortex of certain ciliate and flagellate protozoans consisting of a cavity and long,......
tuber
tuber, specialized storage stem of certain seed plants. Tubers are usually short and thickened and typically grow......
turgor
turgor, Pressure exerted by fluid in a cell that presses the cell membrane against the cell wall. Turgor is what......
tympanic membrane
tympanic membrane, thin layer of tissue in the human ear that receives sound vibrations from the outer air and......
ulna
ulna, inner of two bones of the forearm when viewed with the palm facing forward. (The other, shorter bone of the......
ultimobranchial gland
ultimobranchial gland, in biology, any of the small bodies in the pharynx that develop behind the fifth pair of......
umami
umami, savory or meaty taste, one of the five fundamental taste sensations. The taste of umami is derived from......
ureter
ureter, duct that transmits urine from the kidney to the bladder. There normally is one ureter for each kidney.......
urethra
urethra, duct that transmits urine from the bladder to the exterior of the body during urination. The urethra is......
urethral gland
urethral gland, in male placental mammals, any of the glands that branch off the internal wall of the urethra,......
urinary bladder
urinary bladder, in most vertebrates, except birds, organ for the temporary storage of urine from the kidneys,......
urination
urination, the process of excreting urine from the urinary bladder. Nerve centres for the control of urination......
urine
urine, liquid or semisolid solution of metabolic wastes and certain other, often toxic, substances that the excretory......
Urogenital system
Urogenital system, in vertebrates, the organs concerned with reproduction and urinary excretion. Although their......
uterus
uterus, an inverted pear-shaped muscular organ of the female reproductive system, located between the bladder and......
vacuole
vacuole, in biology, membrane-bound compartment within a cell, enclosed by a specialized membrane and filled with......
vagina
vagina, canal in female mammals that receives the male reproductive cells, or sperm, and is part of the birth canal......
vagus nerve
vagus nerve, longest and most complex of the cranial nerves. The vagus nerve runs from the brain through the face......
vascular system
vascular system, in vascular plants, assemblage of conducting tissues and associated supportive fibres that transport......
ventricle
ventricle, muscular chamber that pumps blood out of the heart and into the circulatory system. Ventricles occur......
vertebral column
vertebral column, in vertebrate animals, the flexible column extending from neck to tail, made of a series of bones,......
Vesalius, Andreas
Andreas Vesalius was a Renaissance physician who revolutionized the study of biology and the practice of medicine......
vessel
vessel, in botany, the most specialized and efficient conducting structure of xylem (fluid-conducting tissues).......
vestibular system
vestibular system, apparatus of the inner ear involved in balance. The vestibular system consists of two structures......
vestibulocochlear nerve
vestibulocochlear nerve, nerve in the human ear, serving the organs of equilibrium and of hearing. It consists......
Vibrissae
Vibrissae, stiff hairs on the face or nostrils of an animal, such as the whiskers of a cat. Vibrissae often act......
villus
villus, in anatomy any of the small, slender, vascular projections that increase the surface area of a membrane.......
Virchow, Rudolf
Rudolf Virchow was a German pathologist and statesman, one of the most prominent physicians of the 19th century.......
vision
vision, physiological process of distinguishing, usually by means of an organ such as the eye, the shapes and colours......
Visual pigment
Visual pigment, any of a number of related substances that function in light reception by animals by transforming......
Viviparity
Viviparity, retention and growth of the fertilized egg within the maternal body until the young animal, as a larva......
vocal cord
vocal cord, either of two folds of mucous membrane that extend across the interior cavity of the larynx and are......
vocal sac
vocal sac, the sound-resonating throat pouch of male frogs and toads (amphibians of the order Anura). Vocal sacs......
Vocalization
Vocalization, any sound produced through the action of an animalâs respiratory system and used in communication.......
Voit, Carl von
Carl von Voit was a German physiologist whose definitive measurements of gross metabolism in mammals, including......
vulva
vulva, the external female genitalia that surround the opening to the vagina; collectively these consist of the......
Weber, Ernst Heinrich
Ernst Heinrich Weber was a German anatomist and physiologist whose fundamental studies of the sense of touch introduced......
Weiss, Paul Alfred
Paul Alfred Weiss was an Austrian-born American biologist who did pioneering research on the mechanics of nerve......
Wernicke area
Wernicke area, region of the brain that contains motor neurons involved in the comprehension of speech. This area......
whalebone
whalebone, series of stiff keratinous plates in the mouths of baleen whales, used to strain copepods and other......
What Are Gut Bacteria?
Gut bacteria are microorganisms that naturally inhabit the digestive tract. They serve critical roles in the human......
What are turtle shells made of?
Turtle shells are made of bone and cartilage, but it is the form and function of the shells that make them unique......
What causes a drought?
Droughts occur when evaporation and transpiration rates consistently exceed precipitation over an extended period......
What causes allergies?
Allergic reactions are caused by substances known as allergens. These substances can be found in a variety of sources......
What Causes Brain Freeze?
Brain freeze, also known as cold-stimulus headache or sphenopalatine ganglioneuralgia, is a phenomenon triggered......
What does a narwhal use its horn for?
A variety of theories have been proposed for the specific function of the narwhalâs long, straight tusk, but first......
What Happened to Einsteinâs Brain?
Albert Einstein, touted as one of the greatest thinkers of the 20th century, died April 18, 1955, as a result of......
What Happens When You Swallow Gum?
Your parents may have warned you not to swallow your chewing gum because it would remain in your stomach for seven......
What Is a Hamate Bone?
A hamate is a triangular bone located along the ulnar (pinky) side of the wrist among the carpal bones. It is distinguished......
white blood cell
white blood cell, a cellular component of the blood that lacks hemoglobin, has a nucleus, is capable of motility,......
Why Are Chromosomes in Pairs?
Chromosomes occur in pairs when organisms develop from two sets of genetic information. In sexually reproducing......
Why Are Elephantsâ Ears So Big?
An elephantâs large ears serve several purposes. Thermoregulationâan organismâs maintenance of its own body temperature......
Why are mosquitoes attracted to certain people?
Mosquitoes that feed on human blood are attracted to certain people more than others due to a combination of factors......
Why are plants green?
Plants are green because of a pigment found in the chloroplasts of plant cells called chlorophyll. It plays a crucial......
Why are reptiles cold-blooded?
Most reptiles are cold-blooded (ectothermic) because they rely on external sources to regulate their body temperature.......
Why are robin eggs blue?
Robin eggs are blue due to a fascinating evolutionary adaptation that may help protect them from sun exposure.......
Why are some eggs brown and some white?
The color of an eggshell is determined primarily by the breed of the hen that laid it. This trait is genetic: hens......
Why Are Stem Cells Important?
Stem cells are important because they are the bodyâs raw materials for growth, repair, and renewal. Unlike most......
Why are there different blood types?
Different blood groups are the result of genetic variations that determine the presence or absence of specific......
Why Canât You Tickle Yourself?
At some point in your life youâve probably been tickledârepeatedly touched in a way that induced smiling, laughter,......
Why do cats blink slowly?
Cats blink slowly as a form of nonverbal communication, often interpreted as a sign of trust and affection toward......
Why do cats have slit pupils?
Cats have slit pupils primarily to enhance their ability to see in varying light conditions. They are crepuscular......
Why do cats have whiskers?
Cats have whiskers primarily for tactile sensing, which is crucial for their survival and daily activities. Whiskers,......
Why do deer shed their antlers?
Deer shed their antlers as part of hormonal changes linked to their survival and mating season. In all but one......
Why do dogs have wet noses?
Dogs have wet noses mainly to enhance their sense of smell. The moisture on the nose traps scent particles in the......
Why Do Gray Hairs Have a Different Texture?
Gray hairs are indeed unusual, and not only because of their color. Gray hair is stiffer and more wiry than hair......
Why do humans have eyebrows?
Eyebrows are an often overlooked feature of the face. Without much fanfare they automatically do their job of protecting......
Why Do Leaves Change Color in the Fall?
Green leaves get their color from the photosynthetic pigment chlorophyll. When deciduous leaves are preparing to......
Why do leaves change colors in the fall?
In many places around the world, autumn is marked by the slow, beautiful change of green foliage to vibrant reds,......
Why Do Leaves Fall in Autumn?
In temperate regions of the world, autumn is marked by the brightly colored foliage that slowly drops from trees......
Why do salmon die after spawning?
Salmon are biologically programmed to die after spawning, a phenomenon known as semelparity. This is a reproductive......
Why do snakes flick their tongues?
When William Shakespeare warned of the venomous touch of a serpentâs forked tongue, he was quite off the mark.......
Why Do We Have Earwax?
Sticky, gooey, oftentimes orange, and homemade within the earsâearwax is considered a gross nuisance that people......
Why do zebras have stripes?
There are several theories about why zebras have stripes. Scientists believe that one of the main reasons is camouflage......
Why Does Blood Taste Like Metal?
Blood is often described as having a metallic taste because it contains a large amount of iron, mainly within hemoglobin,......
Why Does Cilantro Taste Like Soap to Some People?
Whether cilantro tastes fresh and citrusy or horribly soapy largely comes down to genetics. For most people, cilantro......
Why Does Hair Turn Gray?
Hair turns gray as melanocytesâthe cells that generate melanin, which gives hair (and skin) its colorationâdeteriorate......
Why Does Head Hair Grow Indefinitely but Not Body Hair?
The key difference between the growth of head hair and body hair lies in the duration of the active growth phase:......
Why Does Heat Relax Your Muscles?
Exercise is painful. As the clichĂ© goes, âNo pain, no gain.â When the body exerts itself, pumping action out of......
Wigglesworth, Sir Vincent (Brian)
Sir Vincent Wigglesworth was an English entomologist, noted for his contribution to the study of insect physiology.......
Wilson, Edmund Beecher
Edmund Beecher Wilson was an American biologist known for his researches in embryology and cytology. In 1891 Wilson......
Wolffian duct
Wolffian duct, one of a pair of tubes that carry urine from primitive or embryonic kidneys to the exterior or to......
wrist
wrist, complex joint between the five metacarpal bones of the hand and the radius and ulna bones of the forearm.......
Wundt, Wilhelm
Wilhelm Wundt was a German physiologist and psychologist who is generally acknowledged as the founder of experimental......
Xg blood group system
Xg blood group system, classification of human blood based on the presence of proteins called Xg antigens on the......
xylem
xylem, plant vascular tissue that conveys water and dissolved minerals from the roots to the rest of the plant......
Yolk
Yolk, the nutritive material of an egg, used as food by a developing, embryonic animal. Eggs with relatively little,......
Yt blood group system
Yt blood group system, classification of human blood based on the presence of molecules known as Yt antigens on......