Cells, Organs & Tissues, SEA-TON

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.
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Cells, Organs & Tissues Encyclopedia Articles By Title

seashell
seashell, hard exoskeleton of marine mollusks such as snails, bivalves, and chitons that serves to protect and......
sebaceous gland
sebaceous gland, small oil-producing gland present in the skin of mammals. Sebaceous glands are usually attached......
second messenger
second messenger, molecule inside cells that acts to transmit signals from a receptor to a target. The term second......
secretion
secretion, in biology, production and release of a useful substance by a gland or cell; also, the substance produced.......
semen
semen, fluid that is emitted from the male reproductive tract and that contains sperm cells, which are capable......
semicircular canal
semicircular canal, any of three loop-shaped organs in the inner ear that help control balance and stability by......
semilunar valve
semilunar valve, either of two pocketlike half-moon-shaped structures located between the left ventricle and the......
seminal vesicle
seminal vesicle, either of two elongated saclike glands that secrete their fluid contents into the ejaculatory......
semispinalis muscle
semispinalis muscle, any of the deep muscles just to either side of the spine that arise from the transverse processes......
Senses
Senses, means by which animals detect and respond to stimuli in their internal and external environments. The senses......
sensory neuron
sensory neuron, nerve cell that carries information about changes in external and internal environments to the......
serum
serum, the portion of plasma remaining after coagulation of blood, during which process the plasma protein fibrinogen......
serum albumin
serum albumin, protein found in blood plasma that helps maintain the osmotic pressure between the blood vessels......
sex chromosome
sex chromosome, either of a pair of chromosomes that determine whether an individual is male or female. The sex......
Sex hormone
Sex hormone, a chemical substance produced by a sex gland or other organ that has an effect on the sexual features......
Sharpey-Schafer, Sir Edward Albert
Sir Edward Albert Sharpey-Schafer was an English physiologist and inventor of the prone-pressure method (Schafer......
Sherrington, Sir Charles Scott
Sir Charles Scott Sherrington was an English physiologist whose 50 years of experimentation laid the foundations......
shoulder
shoulder, in anatomy, the joint between the arm, or forelimb, and the trunk, together with the adjacent tissue,......
sieve element
sieve element, in vascular plants, elongated living cells of the phloem, the nuclei of which have fragmented and......
sigmoid colon
sigmoid colon, a terminal section of the large intestine that connects the descending colon to the rectum; its......
skeletal muscle
skeletal muscle, most common of the three major types of muscle tissue in vertebrates, along with cardiac muscle......
skeleton, human
human skeleton, the internal skeleton that serves as a framework for the body. This framework consists of many......
skull
skull, skeletal framework of the head of vertebrates, composed of bones or cartilage, which form a unit that protects......
small intestine
small intestine, a long, narrow, folded or coiled tube extending from the stomach to the large intestine; it is......
smell
smell, the detection and identification by sensory organs of airborne chemicals. The concept of smell, as it applies......
smooth endoplasmic reticulum
smooth endoplasmic reticulum (SER), meshwork of fine disklike tubular membrane vesicles, part of a continuous membrane......
smooth muscle
smooth muscle, muscle that shows no cross stripes under microscopic magnification. It consists of narrow spindle-shaped......
sodium-potassium pump
sodium-potassium pump, in cellular physiology, a protein that has been identified in many cells that maintains......
soft palate
soft palate, in mammals, structure consisting of muscle and connective tissue that forms the roof of the posterior......
soleus muscle
soleus muscle, a flat, broad muscle of the calf of the leg lying just beneath the gastrocnemius muscle. It arises......
soma
soma, in biology, all the living matter of an animal or a plant except the reproductive, or germ, cells. The distinction......
Spallanzani, Lazzaro
Lazzaro Spallanzani was an Italian physiologist who made important contributions to the experimental study of bodily......
sperm
sperm, male reproductive cell, produced by most animals. With the exception of nematode worms, decapods (e.g.,......
spermatic cord
spermatic cord, either of a pair of tubular structures in the male reproductive system that support the testes......
spermatogenesis
spermatogenesis, the origin and development of the sperm cells within the male reproductive organs, the testes.......
Sperry, Roger Wolcott
Roger Wolcott Sperry was an American neurobiologist. He was a corecipient with David Hunter Hubel and Torsten Nils......
sphincter muscle
sphincter muscle, any of the ringlike muscles surrounding and able to contract or close a bodily passage or opening.......
spinal cord
spinal cord, major nerve tract of vertebrates, extending from the base of the brain through the canal of the spinal......
spinal nerve
spinal nerve, in vertebrates, any one of many paired peripheral nerves that arise from the spinal cord. In humans......
spinalis muscle
spinalis muscle, any of the deep muscles of the back near the vertebral column that, as part of the erector spinae......
spiracle
spiracle, in arthropods, the small external opening of a trachea (respiratory tube) or a book lung (breathing organ......
Starling, Ernest Henry
Ernest Henry Starling was a British physiologist whose prolific contributions to a modern understanding of body......
Steinman, Ralph M.
Ralph M. Steinman was a Canadian immunologist and cell biologist who shared the 2011 Nobel Prize for Physiology......
stem
stem, in botany, the plant axis that bears buds and shoots with leaves and, at its basal end, roots. The stem conducts......
stem cell
stem cell, an undifferentiated cell that can divide to produce some offspring cells that continue as stem cells......
Steno, Nicolaus
Nicolaus Steno was a geologist and anatomist whose early observations greatly advanced the development of geology.......
Stern, Elizabeth
Elizabeth Stern was a Canadian-born American pathologist, noted for her work on the stages of a cell’s progression......
sternum
sternum, in the anatomy of tetrapods (four-limbed vertebrates), elongated bone in the centre of the chest that......
stolon
stolon, in biology, a special slender horizontal branch serving to propagate the organism. In botany a stolon—also......
stomach
stomach, saclike expansion of the digestive system, between the esophagus and the small intestine; it is located......
stomate
stomate, any of the microscopic openings or pores in the epidermis of leaves and young stems. Stomata are generally......
sucking
sucking, drawing of fluids into the mouth by creating a vacuum pressure in the oral cavity. Mammalian infants rely......
Sulston, John
John Sulston was a British biologist who, with Sydney Brenner and H. Robert Horvitz, won the Nobel Prize for Physiology......
summation
summation, in physiology, the additive effect of several electrical impulses on a neuromuscular junction, the junction......
sunburn
sunburn, acute cutaneous inflammation caused by overexposure to ultraviolet (UV) radiation of the so-called UVB......
Sutherland, Earl W., Jr.
Earl W. Sutherland, Jr. was an American pharmacologist and physiologist who was awarded the 1971 Nobel Prize for......
swallowing
swallowing, the act of passing food from the mouth, by way of the pharynx (or throat) and esophagus, to the stomach.......
sweat
sweat, the moisture excreted in visible quantities through the openings of the sweat glands. See...
sweat gland
sweat gland, either of two types of secretory skin glands occurring only in mammals. The eccrine sweat gland, which......
Swedenborg, Emanuel
Emanuel Swedenborg was a Swedish scientist, Christian mystic, philosopher, and theologian who wrote voluminously......
swim bladder
swim bladder, buoyancy organ possessed by most bony fish. The swim bladder is located in the body cavity and is......
Sylvius, Franciscus
Franciscus Sylvius was a physician, physiologist, anatomist, and chemist who is considered the founder of the 17th-century......
sympathetic nervous system
sympathetic nervous system, division of the nervous system that functions to produce localized adjustments (such......
synapse
synapse, the site of transmission of electric nerve impulses between two neurons or between a neuron and a gland......
synovial tissue
synovial tissue, thin, loose vascular connective tissue that makes up the membranes surrounding joints and the......
Syrinx
Syrinx, vocal organ of birds, located at the base of the windpipe (trachea), where the trachea divides into the......
systemic circulation
systemic circulation, in physiology, the portion of the circulatory system that carries oxygen- and nutrient-rich......
systole
systole, period of contraction of the ventricles of the heart that occurs between the first and second heart sounds......
T cell
T cell, type of white blood cell (leukocyte) that is an essential part of the immune system. T cells are one of......
taproot
taproot, main root of a primary root system, growing vertically downward. Most dicotyledonous plants (see cotyledon),......
Target theory
Target theory, in biology, the concept that the biological effects of radiations such as X rays result from ionization......
tarsal
tarsal, any of several short, angular bones that in humans make up the ankle and that—in animals that walk on their......
taste
taste, the detection and identification by the sensory system of dissolved chemicals placed in contact with some......
taste bud
taste bud, small organ located on the tongue in terrestrial vertebrates that functions in the perception of taste.......
tear duct and glands
tear duct and glands, structures that produce and distribute the watery component of the tear film. Tears consist......
telomere
telomere, segment of DNA occurring at the ends of chromosomes in eukaryotic cells (cells containing a clearly defined......
telophase
telophase, in mitosis and meiosis, the final stage of cell division in which the spindle disappears and the nucleus......
tendon
tendon, tissue that attaches a muscle to other body parts, usually bones. Tendons are the connective tissues that......
tendril
tendril, in botany, plant organ specialized to anchor and support vining stems. Tendrils may be modified leaves,......
test
test, in zoology, a protective, loose-fitting shell secreted by some protozoans (especially foraminiferans and......
testis
testis, in animals, the organ that produces sperm, the male reproductive cell, and androgens, the male hormones.......
Testosterone
Testosterone, hormone produced by the male testis that is responsible for development of the male sex organs and......
thalamus
thalamus, either of a pair of large ovoid organs that form most of the lateral walls of the third ventricle of......
The Human Brain Runs on Less Power than a Light Bulb
The human brain is one of the most complex structures known to science. It contains roughly 86 billion neurons,......
Thermoregulation
Thermoregulation, the maintenance of an optimum temperature range by an organism. Cold-blooded animals (poikilotherms)......
Thimann, Kenneth V.
Kenneth V. Thimann was an English-born American plant physiologist who isolated auxin, an important plant growth......
thoracic duct
thoracic duct, in mammalian anatomy, a principal channel for lymph. From about the level of the small of the back......
thrombocyte
thrombocyte, a small, nucleated, spindle-shaped cell of nonmammalian vertebrates that plays a role in the clotting......
thymus
thymus, pyramid-shaped lymphoid organ that, in humans, is immediately beneath the sternum (breastbone) at the level......
thyroid gland
thyroid gland, endocrine gland that is located in the anterior part of the lower neck, below the larynx (voice......
tibia
tibia, inner and larger of the two bones of the lower leg in vertebrates—the other is the fibula. In humans the......
Tissue
Tissue, in physiology, a level of organization in multicellular organisms; it consists of a group of structurally......
Today in History—August 30: The Mystery of the Golden Blob Begins
Find blob? Check. Poke blob? Uh-huh. ID blob? That one’s gonna take a while. On this day in 2023, a remotely operated......
Today in History—October 15: Putting the Power of Birth Control in a Pill
On October 15, 1951, Luis E. Miramontes, a chemist working in Mexico City at the pharmaceutical company Syntex,......
tongue
tongue, in most vertebrates, an organ, capable of various muscular movements, located on the floor of the mouth.......

Cells, Organs & Tissues Encyclopedia Articles By Title