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Sagittal plane: A vertical plane that divides the body or organs into
left and right portions. Such a plane may be midsagittal (mediam),
in which the divisions are equal, or parasagittal, in which the
divisions are unequal.
Salt:
A substance that, when dissolved in water, ionizes into cations and anions,
neither of which are hydrogen ions (H+) or hydroxide ions (OH-).
Sarcoma:
A connective tissue tumor, often highly malignant.
Sarcomere:
A contractile unit in a striated muscle fiber extending from one Z disc
to the next Z disk.
Sarcoplasm: The cytoplasm of a muscle fiber (cell).
Saw Palmetto:
Serenoa repens is the medical name for the herb saw palmetto.
Extracts of Saw Palmetto have been studied for their ability to inhibit the
enzymes 5-alpha reductase and 3-ketosteroid reductase. These enzymes are
responsible for the conversion of testosterone to dihydrotestosterone (DHT).
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Scavenge
(free radicals): To combine readily with free radicals, preventing them
from reacting with other molecules.
Scurvy:
A disorder caused by lack of vitamin C. Symptoms include anemia, bleeding
gums, tooth loss, joint pain, and fatigue. Scurvy is treated by supplying
foods high in vitamin C as well as with vitamin C supplements.
Seizure:
Uncontrolled electrical activity in the brain, which may produce a physical
convulsion, minor physical signs, thought disturbances, or a combination of
symptoms.
Serenoa
repens: see Saw Palmetto or
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details.
Serotonin:
A hormone also known as 5-hydroxytryptamine. Serotonin functions as both a
neurotransmitter and a vasoconstrictor (substance that causes blood vessels
to narrow).
Serum:
The liquid part of blood (as opposed to blood cells) that makes up about
half its volume. Serum differs from plasma in that the blood sample has
clotted. A centrifuge is used in the laboratory to separate serum from cells
after blood has clotted.
Short
bowel syndrome: A malabsorption syndrome resulting from the surgical
removal of an extensive portion of the small intestine.
Sickle
cell anemia: A hereditary disease in which a mutation in the gene for
one of the proteins that comprises hemoglobin results in the formation of
defective hemoglobin molecules known as hemoglobin S. Individuals who are
homozygous for this mutation (possess two genes for hemoglobin S) have red
blood cells that change from the normal discoid shape to a sickle shape when
the oxygen supply is low. These sickle-shaped cells are easily trapped in
capillaries and damaged, resulting in severe anemia. Individuals who are
heterozygous for the mutation (possess one gene for hemoglobin S and one
normal hemoglobin gene) have increased resistance to malaria.
Sideroblastic anemia: A group of anemias that are all characterized by
the accumulation of iron deposits in the mitochondria of immature red blood
cells. These abnormal red blood cells do not mature normally, and many are
destroyed in the bone marrow before reaching the circulation. Sideroblastic
anemias can be hereditary, idiopathic (unknown cause), or caused by such
diverse factors as certain drugs, alcohol, or copper deficiency.
Small
intestine: The part of the digestive tract that extends from the stomach
to the large intestine. The small intestine includes the duodenum (closest
to the stomach), the jejunum, and the ileum (closest to the large
intestine).
Sorbitol:
The polyol (sugar alcohol) corresponding to glucose.
Spina
bifida: A birth defect, also known as a neural tube defect, resulting
from failure of the lower end of the neural tube to close during embryonic
development. Spina bifida, the most common cause of infantile paralysis, is
characterized by a lack of protection of the spinal cord by its membranes
and vertebral bones.
Sprue:
Also known as celiac sprue and celiac disease, it is an inherited disease in
which the intestinal lining is inflamed in response to the ingestion of a
protein known as gluten. Treatment of celiac disease involves the avoidance
of gluten, which is present in many grains, including rye, oats, and barley.
Inflammation and atrophy of the lining of the small intestine leads to
impaired nutrient absorption.
Status:
The state of nutrition of an individual with respect to a specific nutrient.
Diminished or low status indicates inadequate supply or stores of a specific
nutrient for optimal physiological functioning.
Steroid:
A molecule related to cholesterol. Many important hormones such as estrogen
and testosterone are steroids. See hormone.
Steroid
hormone receptor: A protein within a cell which binds to a specific
steroid hormone. Binding of the steroid hormone changes the shape of the
receptor protein and activates it, allowing it to activate gene
transcription. In this way, a steroid hormone can activate the synthesis of
specific proteins.
Stress
fracture: A hairline or microscopic break in a bone, usually due to
repetitive stress rather than trauma. Stress fractures are usually painful,
and may be undetectable by X-ray. Though they may occur in almost any bone,
common sites of stress fractures are the tibia (lower leg) and metatarsals
(foot).
Stroke:
The sudden death of some brain cells due to lack of oxygen, when blood flow
to the brain is impaired by the blockage (usually due to a blood clot) or
rupture of a blood vessel in the brain. A stroke is also called a
cerebrovascular accident (CVA).
Subclinical: Without clinical signs or symptoms; sometimes used to
describe the early stage of a disease or condition, before symptoms are
detectable by clinical examination or laboratory tests.
Substrate:
A reactant in an enzyme catalyzed reaction.
Supplement: A nutrient or phytochemical supplied in addition to that
which is obtained in the diet.
Syndrome:
A combination of symptoms that occur together and is indicative of a
specific condition or disease.
Systolic
blood pressure:
The highest arterial pressure measured during the heart beat
cycle. It occurs when the heart muscle is contracting (pumping).
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