Cells, Organs & Tissues, HOR-LUN
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
hormone, organic substance secreted by plants and animals that functions in the regulation of physiological activities......
- Introduction
- Vertebrates, Endocrine, Neuroendocrine
- LH, ICSH, Endocrine
- Thyroid Gland, Metabolism, Hormone Production
- Parathyroid, Calcium, Parathormone
- Glucagon, Pancreas, Regulation
- Reproductive, Endocrine, Glands
- Endocrine Glands, Secretions, Hormone Functions
- Molting, Insects, Juveniles
- Plant Growth, Photosynthesis, Reproduction
- Growth Inhibitors
horn, in zoology, either of the pair of hard processes that grow from the upper portion of the head of many hoofed......
Sir Victor Horsley was a British physiologist and neurosurgeon who was first to remove a spinal tumour (1887).......
hot flash, symptom of declining estrogen levels associated with menopause that is characterized by a sensation......
Bernardo Alberto Houssay was an Argentine physiologist and corecipient, with Carl and Gerty Cori, of the 1947 Nobel......
Fish primarily breathe through gills, which are specialized organs that extract dissolved oxygen from water. The......
Fish reproduction is a fascinating process that varies significantly across different species. Most bony fishes......
Frogs have an adaptable respiratory system that allows them to breathe in multiple ways throughout their life cycle......
Have you ever seen a monkey getting a manicure? Though that line sounds like the beginning of a bad joke, it actually......
The pearl-making process begins when a foreign particle, like a grain of sand or a tiny parasite, finds its way......
Penguins have a unique feather arrangement and body structure that provides excellent insulation. Their feathers......
Snakes have a unique and fascinating way of swallowing prey that is much larger than their own heads and even bodies.......
Modern birds are living dinosaurs, having evolved from a line of theropod dinosaurs more than 150 million years......
People are mammals, and mammals are warm-blooded creatures, capable of maintaining a relatively constant internal......
Whales can hold their breath for varying durations depending on the species, with some capable of staying submerged......
Chicken eggs typically take about 21 days to hatch. This is the time it takes for a fertilized egg to develop into......
The process of food digestion typically takes between 24 and 72 hours. The precise length of time is determined......
Spiders typically have eight eyes, although some species may have fewer. The number and arrangement of eyes can......
A typical adult human has approximately 8 to 12 pints (about 4.5 to 6.8 liters) of blood circulating through their......
The number of teeth a shark has can vary significantly depending on the species, but some species may go through......
David Hunter Hubel was a Canadian American neurobiologist, corecipient with Torsten Nils Wiesel and Roger Wolcott......
human cardiovascular system, organ system that conveys blood through vessels to and from all parts of the body,......
- Introduction
- Origin, Development & Function
- Heart Wall, Blood Flow, Circulation
- Coronary Arteries, Heart Valves, Blood Flow
- Electrocardiogram, Heartbeat, Circulation
- Arteries, Veins, Capillaries
- Arteries, Circulation, Blood Flow
- Pulse, Circulation, Blood Vessels
- Superior Vena Cava, Tributaries, Circulation
- Inferior Vena Cava, Tributaries, Circulation
- Capillaries, Circulation, Oxygenation
humerus, long bone of the upper limb or forelimb of land vertebrates that forms the shoulder joint above, where......
John Hunter was a surgeon, founder of pathological anatomy in England, and early advocate of investigation and......
Sir Andrew Fielding Huxley was an English physiologist, cowinner (with Sir Alan Hodgkin and Sir John Carew Eccles)......
hyaline cartilage, type of connective tissue, glossy pearl-gray or blue-white in appearance and resilient, found......
hydrogenosome, membrane-bound organelle found in the cytoplasm of eukaryotic cells (cells with clearly defined......
hymen, in the female reproductive system, the membrane that encircles or covers part of the opening of the vagina.......
hyoid bone, U-shaped bone situated at the root of the tongue in the front of the neck and between the lower jaw......
hypothalamus, region of the brain lying below the thalamus and making up the floor of the third cerebral ventricle.......
Louis Ignarro is an American pharmacologist who, along with Robert F. Furchgott and Ferid Murad, was co-awarded......
Ii blood group system, classification of human blood based on the presence of antigens I and i on the surface of......
ileum, the final and longest segment of the small intestine. It is specifically responsible for the absorption......
iliocostalis muscle, any of the deep muscles of the back that, as part of the erector spinae (sacrospinalis) muscle......
immune system, the complex group of defense responses found in humans and other advanced vertebrates that helps......
- Introduction
- Interferons, Antibodies, Cells
- Macrophages, Antigens, Defense
- Lymphocytes, Antigens, Immunity
- Antigens, Cells, Receptors
- Lymphocytes, Diversity, Adaptive
- IgA, IgG, IgM
- T Cells, Antigens, Receptors
- T Cells, B Cells, Activation
- Antibodies, Mediated, Mechanisms
- Killer Cells, Antigens, Defense
- Cancer Immunity, T-cells, Antigens
- Evolution, Defense, Adaptation
immunization, process by which resistance to disease is acquired or induced in plants and animals. This discussion......
incubation, the maintenance of uniform conditions of temperature and humidity to ensure the development of eggs......
induced pluripotent stem cell (iPS cell), immature cell that is generated from an adult (mature) cell and that......
inner ear, part of the ear that contains organs of the senses of hearing and equilibrium. The bony labyrinth, a......
integument, in biology, network of features that forms the covering of an organism. The integument delimits the......
- Introduction
- Invertebrate Groups, Structure, Function
- Parasites, Adaptations, Protection
- Exoskeleton, Cuticle, Segmentation
- Hair, Glands, Nails
- Epidermal, Scales, Reptiles
- Skin, Hair, Glands
- Fish Scales, Skin, Protection
- Reptiles, Scales, Skin
- Skin, Hair, Sweat Glands
- Embryology, Evolution, Protection
intercostalis muscle, in human physiology, any of a series of short muscles that extend between the ribs and serve......
intestinal gas, material contained within the digestive tract that consists principally of swallowed air and partly......
intestinal juice, clear to pale yellow, watery secretion composed of hormones, digestive enzymes, mucus, and neutralizing......
intestine, tubular part of the alimentary canal that extends from the stomach to the anus. The intestine is the......
intracellular fluid, substance within living cells that is made up primarily of water and molecules such as dissolved......
ion channel, protein expressed by virtually all living cells that creates a pathway for charged ions from dissolved......
iris, in anatomy, the colored muscular part of the eye surrounding the pupil, the small black opening in the center.......
Common wisdom holds that it is unsafe to swim after eating unless one waits for some prescribed period of time—usually......
ivory, variety of dentin of which the tusk of the elephant is composed and which is prized for its beauty, durability,......
Jacobson’s organ, an organ of chemoreception that is part of the olfactory system of amphibians, reptiles, and......
jaw, either of a pair of bones that form the framework of the mouth of vertebrate animals, usually containing teeth......
Elvin M. Jellinek was an American physiologist who was a pioneer in the scientific study of alcoholism. Jellinek......
Sir William Jenner, 1st Baronet was a physician and anatomist best known for his clinico-pathologic distinction......
joint, in anatomy, a structure that separates two or more adjacent elements of the skeletal system. Depending on......
David Julius is an American physiologist known for his discovery of heat- and cold-sensing receptors in the nerve......
karyotype, visual representation of the complete set of chromosomes in a cell. In a karyotype, the chromosomes,......
Sir Bernard Katz was a German-born British physiologist who investigated the functioning of nerves and muscles.......
William Williams Keen was the doctor who was the United States’ first brain surgeon. After graduating (M.D., 1862)......
Kell blood group system, classification of human blood based on the presence on the surfaces of red blood cells......
keratin, fibrous structural protein of hair, nails, horn, hoofs, wool, feathers, and of the epithelial cells in......
Richard Darwin Keynes was a British physiologist who was among the first in Britain to trace the movements of sodium......
Kidd blood group system, classification of human blood based on the presence of glycoproteins known as Kidd (Jk)......
kidney, in vertebrates and some invertebrates, organ that maintains water balance and expels metabolic wastes.......
kinocilium, filamentous structure occurring on auditory hair cells in the inner ear that functions in the development......
knee, hinge joint that is formed by the meeting of the thigh bone (femur) and the larger bone (tibia) of the lower......
knuckle, the joint of a finger. The knuckle joint of an animal killed for eating is the tarsal or carpal joint......
Carl Koller was a Czech-born American ophthalmic surgeon whose introduction of cocaine as a surface anesthetic......
August Krogh was a Danish physiologist who received the Nobel Prize for Physiology or Medicine in 1920 for his......
Kupffer cell, any of the stellate (star-shaped) cells in the linings of the liver sinusoids. The sinusoids are......
Rudolf Albert von Kölliker was a Swiss embryologist and histologist, one of the first to interpret tissue structure......
labour, in human physiology, the physical activity experienced by the mother during parturition (q.v.), or...
labyrinthodont, a type of tooth made up of infolded enamel that provides a grooved and strongly reinforced structure.......
lactation, secretion and yielding of milk by females after giving birth. The milk is produced by the mammary glands,......
lacteal, one of the lymphatic vessels that serve the small intestine and, after a meal, become white from the minute......
islets of Langerhans, irregularly shaped patches of endocrine tissue located within the pancreas of most vertebrates.......
large intestine, posterior section of the intestine, consisting typically of four regions: the cecum, colon, rectum,......
larynx, a hollow, tubular structure connected to the top of the windpipe (trachea); air passes through the larynx......
lateral line system, a system of tactile sense organs, unique to aquatic vertebrates from cyclostome fishes (lampreys......
laterality, in biological psychology, the development of specialized functioning in each hemisphere of the brain......
latex, colloidal suspension, either the milky white liquid emulsion found in the cells of certain flowering plants......
latissimus dorsi, widest and most powerful muscle of the back. It is a large, flat, triangular muscle covering......
Pyotr Petrovich Lazarev was a Soviet physicist and biophysicist known for his physicochemical theory of the movement......
leaf, in botany, any usually flattened green outgrowth from the stem of a vascular plant. As the primary sites......
leaf fiber, hard, coarse fiber obtained from leaves of certain monocotyledonous plants (flowering plants that usually......
lecanemab, human monoclonal antibody used for the treatment of Alzheimer disease. Lecanemab clears away and blocks......
lens, in anatomy, a nearly transparent biconvex structure suspended behind the iris of the eye, the sole function......
leptin receptor, molecule that receives and transmits signals from leptin, a hormone released from fat cells that......
levator muscle, any of the muscles that raise a body part. In humans these include the levator anguli oris, which......
levonorgestrel, synthetic progestogen (any progestational steroid, such as progesterone) that is used as a form......
Lewis blood group system, classification of human blood based on the expression of glycoproteins called Lewis (Le)......
ligament, tough fibrous band of connective tissue that serves to support the internal organs and hold bones together......
lignin, complex oxygen-containing organic polymer that, with cellulose, forms the chief constituent of wood. It......
limbic system, group of structures in the brain that governs emotions, motivation, olfaction (sense of smell),......
lips, soft pliable anatomical structures that form the mouth margin of most vertebrates, composed of a surface......
liver, the largest gland in the body, a spongy mass of wedge-shaped lobes that has many metabolic and secretory......
Jacques Loeb was a German-born American biologist noted chiefly for his experimental work on artificial parthenogenesis......
loop of Henle, long U-shaped portion of the tubule that conducts urine within each nephron of the kidney of reptiles,......
lorica, a tubular, conical, or vaselike structure secreted by some protozoans (e.g., Stentor) and many rotifers.......
Carl F.W. Ludwig was a founder of the physicochemical school of physiology in Germany. A professor of physiology......
lung, in air-breathing vertebrates, either of the two large organs of respiration located in the chest cavity and......