Anatomy & Physiology, NRE-POL
Human beings have long been curious about the way that things work, and that curiosity includes wondering about how we ourselves work. The fields of anatomy and physiology involve studying the structures of bodies and the way that those structures and bodies function.
Anatomy & Physiology Encyclopedia Articles By Title
NREM sleep
NREM sleep, one of two phases in the sleep cycle, considered the restful or quiet sleep phase. The other phase......
Nucleic acid
Nucleic acid, naturally occurring chemical compound that serves as the main information-carrying molecule of the......
Nucleoprotein
Nucleoprotein, molecule consisting of a protein linked to a nucleic acid, either DNA (deoxyribonucleic acid) or......
Nucleoside
Nucleoside, a structural subunit of nucleic acids, the heredity-controlling components of all living cells, consisting......
Nucleotide
Nucleotide, any member of a class of organic compounds in which the molecular structure comprises a nitrogen-containing......
nystagmus
nystagmus, involuntary back and forth, up and down, or circular movements of the eyes that are often described......
obstetric fistula
obstetric fistula, abnormal duct or passageway that forms between the vagina and a nearby organ. This type of fistula......
Odour
Odour, the property of certain substances, in very small concentrations, to stimulate chemical sense receptors......
Oil gland
Oil gland, any of a variety of skin structures that secrete oily or greasy substances of various functions. In......
old age
old age, in human beings, the final stage of the normal life span. Definitions of old age are not consistent from......
olfactory bulb
olfactory bulb, structure located in the forebrain of vertebrates that receives neural input about odours detected......
olfactory receptor
olfactory receptor, protein capable of binding odour molecules that plays a central role in the sense of smell......
olfactory system
olfactory system, the bodily structures that serve the sense of smell. The system consists of the nose and the......
oligodendrocyte
oligodendrocyte, a type of neuroglia found in the central nervous system of invertebrates and vertebrates that......
Oligonucleotide
Oligonucleotide, a short chain of nucleotides (nitrogen-containing units linked to a sugar and a phosphate group)......
Oligosaccharide
Oligosaccharide, any carbohydrate of from three to six units of simple sugars (monosaccharides). A large number......
Olympics: The Genetics of Success
For decades, athletes have run, jumped, skated, and skied their way into Olympic history. The rest of us watch......
Ontogeny
Ontogeny, all the developmental events that occur during the existence of a living organism. Ontogeny begins with......
oogenesis
oogenesis, in the human female reproductive system, growth process in which the primary egg cell (or ovum) becomes......
ophthalmoplegia
ophthalmoplegia, paralysis of the extraocular muscles that control the movements of the eye. Ophthalmoplegia usually......
optic atrophy
optic atrophy, degeneration of the optic nerve (the second cranial nerve) due to direct or indirect damage to a......
optic nerve
optic nerve, second cranial nerve, which carries sensory nerve impulses from the more than one million ganglion......
optic neuritis
optic neuritis, inflammation of the optic nerve (the second cranial nerve). The inflammation causes a fairly rapid......
orchitis
orchitis, inflammation and swelling of the testes as a result of infection or physical injury. The testes are a......
Organ
Organ, in biology, a group of tissues in a living organism that have been adapted to perform a specific function.......
organogenesis
organogenesis, in embryology, the series of organized integrated processes that transforms an amorphous mass of......
Osmoregulation
Osmoregulation, in biology, maintenance by an organism of an internal balance between water and dissolved materials......
osteoblast
osteoblast, large cell responsible for the synthesis and mineralization of bone during both initial bone formation......
osteoclast
osteoclast, large multinucleated cell responsible for the dissolution and absorption of bone. Bone is a dynamic......
osteocyte
osteocyte, mature bone cell that maintains bone tissue and coordinates the continual remodeling of bone. Embedded......
osteon
osteon, the chief structural unit of compact (cortical) bone, consisting of concentric bone layers called lamellae,......
ovarian cancer
ovarian cancer, disease characterized by the abnormal growth of cells in the ovaries, the internal reproductive......
ovary
ovary, in zoology, female reproductive organ in which sex cells (eggs, or ova) are produced. The usually paired......
Oviparity
Oviparity, expulsion of undeveloped eggs rather than live young. The eggs may have been fertilized before release,......
ovulation
ovulation, release of a mature egg from the female ovary; the release enables the egg to be fertilized by the male......
ovum
ovum, in human physiology, single cell released from either of the female reproductive organs, the ovaries, which......
P blood group system
P blood group system, classification of human blood based on the presence of any of three substances known as the......
pacemaker
pacemaker, electronic cardiac-support device that produces rhythmic electrical impulses that take over the regulation......
pain
pain, complex experience consisting of a physiological and a psychological response to a noxious stimulus. Pain......
palate
palate, in vertebrate anatomy, the roof of the mouth, separating the oral and nasal cavities. It consists of an......
pancreas
pancreas, compound gland that discharges digestive enzymes into the gut and secretes the hormones insulin and glucagon,......
pancreatic cancer
pancreatic cancer, a disease characterized by abnormal growth of cells in the pancreas, a gland located behind......
pancreatitis
pancreatitis, inflammation of the pancreas, either acute or chronic. The disorder is most commonly caused by excessive......
Paneth’s cell
Paneth’s cell, specialized type of epithelial cell found in the mucous-membrane lining of the small intestine and......
Panting
Panting, a method of cooling, used by many mammals, most birds, and some reptiles, accomplished by means of the......
parasympathetic nervous system
parasympathetic nervous system, division of the nervous system that primarily modulates visceral organs such as......
parathyroid adenoma
parathyroid adenoma, disorder characterized by loss of mineral materials from the skeleton, the development of......
parathyroid gland
parathyroid gland, endocrine gland occurring in all vertebrate species from amphibia upward, usually located close......
Parathyroid hormone
Parathyroid hormone (PTH), substance produced and secreted by the parathyroid glands that regulates serum calcium......
parietal cell
parietal cell, in biology, one of the cells that are the source of the hydrochloric acid and most of the water......
pathology
pathology, medical specialty concerned with the determining causes of disease and the structural and functional......
Pectin
Pectin, any of a group of water-soluble carbohydrate substances that are found in the cell walls and intercellular......
pectoral girdle
pectoral girdle, in anatomy, the bony structure on either side of the body that connects the arm to the upper portion......
pectoralis muscle
pectoralis muscle, any of the muscles that connect the front walls of the chest with the bones of the upper arm......
pelage
pelage, hairy, woolly, or furry coat of a mammal, distinguished from the underlying bare skin. The pelage is significant......
pelvis
pelvis, in human anatomy, basin-shaped complex of bones that connects the trunk and the legs, supports and balances......
penis
penis, the copulatory organ of the male of higher vertebrates that in mammals usually also provides the channel......
periodontal membrane
periodontal membrane, fleshy tissue between tooth and tooth socket that holds the tooth in place, attaches it to......
periosteum
periosteum, dense fibrous membrane covering the surfaces of bones, consisting of an outer fibrous layer and an......
peripheral immune tolerance
peripheral immune tolerance, the set of mechanisms that prevent immune cells—especially T cells and B cells—from......
peristalsis
peristalsis, involuntary movements of the longitudinal and circular muscles, primarily in the digestive tract but......
peritoneum
peritoneum, large membrane in the abdominal cavity that connects and supports internal organs. It is composed of......
perspiration
perspiration, in most mammals, water given off by the intact skin, either as vapour by simple evaporation from......
pervasive developmental disorder
pervasive developmental disorder (PDD), term historically used in reference to any of a group of conditions characterized......
pervasive developmental disorder not otherwise specified
pervasive developmental disorder not otherwise specified (PDD-NOS), condition characterized by impairment in the......
Peyer patch
Peyer patch, any of the nodules of lymphatic cells that aggregate to form bundles or patches and occur usually......
phagocytosis
phagocytosis, process by which cells known as phagocytes ingest or engulf other cells or particles. The phagocyte......
phantom limb syndrome
phantom limb syndrome, the ability to feel sensations and even pain in a limb or limbs that no longer exist. Phantom......
pharynx
pharynx, cone-shaped passageway leading from the oral and nasal cavities in the head to the esophagus and larynx.......
phenylthiocarbamide tasting
phenylthiocarbamide tasting, a genetically controlled ability to taste phenylthiocarbamide (PTC) and a number of......
pheochromocytoma
pheochromocytoma, tumour, most often nonmalignant, that causes abnormally high blood pressure (hypertension) because......
pheromone
pheromone, any endogenous chemical secreted in minute amounts by an organism in order to elicit a particular reaction......
Phospholipid
Phospholipid, any member of a large class of fatlike, phosphorus-containing substances that play important structural......
photodynamism
photodynamism, conversion of certain substances in the skin of animals into other substances by the action of light.......
photophore
photophore, light-emitting organ present in fireflies and certain other bioluminescent animals. Photophores are......
Photoprotein
Photoprotein, in biochemistry, any of several proteins that give off light upon combination with oxygen, hydrogen......
Photoreception
Photoreception, any of the biological responses of animals to stimulation by light. In animals, photoreception......
photorecovery
photorecovery, restoration to the normal state, by the action of visible light, of the deoxyribonucleic acid composing......
photosynthesis
photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical......
Physiology
Physiology, study of the functioning of living organisms, animal or plant, and of the functioning of their constituent......
pineal gland
pineal gland, endocrine gland found in vertebrates that is the source of melatonin, a hormone derived from tryptophan......
pinguecula
pinguecula, very common yellow-white nodule in the conjunctiva at the front of the eye, usually on the side of......
pituitary gland
pituitary gland, ductless gland of the endocrine system that secretes hormones directly into the bloodstream. The......
pituitary tumour
pituitary tumour, most common cause of enlargement of the sella turcica, the bone cavity in the head in which the......
pivot joint
pivot joint, in vertebrate anatomy, a freely moveable joint (diarthrosis) that allows only rotary movement around......
placenta
placenta, in zoology, the vascular (supplied with blood vessels) organ in most mammals that unites the fetus to......
plane joint
plane joint, in anatomy, type of structure in the body formed between two bones in which the articular, or free,......
planula
planula, free-swimming or crawling larval type common in many species of the phylum Cnidaria (e.g., jellyfish,......
plasma
plasma, the liquid portion of blood. Plasma serves as a transport medium for delivering nutrients to the cells......
plasma cell
plasma cell, short-lived antibody-producing cell derived from a type of leukocyte (white blood cell) called a B......
platelet
platelet, colourless, nonnucleated blood component that is important in the formation of blood clots (coagulation).......
pleura
pleura, membrane lining the thoracic cavity (parietal pleura) and covering the lungs (visceral pleura). The parietal......
Plumage
Plumage, collective feathered covering of a bird. It provides protection, insulation, and adornment and also helps......
Plummer disease
Plummer disease, thyroid condition characterized by marked enlargement of the thyroid gland (goitre), firm thyroid......
pollination
pollination, transfer of pollen grains from the stamens (the flower parts that produce them) to the ovule-bearing......
polyembryony
polyembryony, a condition in which two or more embryos develop from a single fertilized egg, forming what in humans......
polyglandular autoimmune syndrome
polyglandular autoimmune syndrome, either of two familial syndromes in which affected patients have multiple endocrine......
polyp
polyp, in zoology, one of two principal body forms occurring in members of the animal phylum Cnidaria. The polyp......
Polysaccharide
Polysaccharide, the form in which most natural carbohydrates occur. Polysaccharides may have a molecular structure......
polyuria
polyuria, daily output of an excessive amount of urine. In humans, polyuria involves the output of more than three......