Anatomy Terms Starting With I
Anatomy Glossary: I
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Insulin
/ IN-suh-lin / · Latin insula, island (referring to the islets of Langerhans)
Insulin is a peptide hormone secreted by beta cells of the pancreatic islets of Langerhans that lowers blood glucose by promoting cellular uptake of glucose and inhibiting hepatic glucose production.
When blood glucose rises after a meal, beta cells release insulin, which binds receptors on muscle, adipose, and liver cells, triggering glucose transporter GLUT4 translocation to the cell surface and enabling glucose uptake. In the liver, insulin promotes glycogen synthesis and suppresses gluconeogenesis, driving blood glucose back toward the fasting set point of around 5 mmol/L. Type 1 diabetes results from autoimmune destruction of beta cells and complete insulin deficiency, while type 2 diabetes involves progressive insulin resistance and relative insulin insufficiency.
Insulin is made by beta cells in pancreatic islets. After a meal, it helps many body cells take up glucose and helps the liver store glucose as glycogen.
Endocrine System Fun Facts →Insulin simply removes sugar from the body. It moves glucose into storage and use pathways rather than making the glucose disappear.
In humans, insulin rises after carbohydrate-rich meals. Muscle and fat cells respond by increasing glucose uptake through insulin-sensitive transport systems.
Muscular System Facts →Interstitial Fluid
/ in-ter-STISH-ul FLOO-id / · Latin interstitium, space between; Latin fluidus
Interstitial fluid is the fluid that fills the spaces between cells in tissues, arising from capillary filtration and serving as the medium for nutrient and waste exchange between blood and cells.
Approximately 11 liters of interstitial fluid are present in the human body, representing about 15% of body weight and forming a critical component of the extracellular fluid compartment. Starling forces capillary hydrostatic pressure, capillary oncotic pressure, interstitial hydrostatic pressure, and interstitial oncotic pressure govern the balance of fluid movement between capillaries and the interstitium. Excess accumulation of interstitial fluid when these forces are disrupted causes edema, occurring in heart failure, liver disease, hypoproteinemia, and lymphatic obstruction.
Interstitial fluid surrounds most body cells and forms the immediate environment they exchange with. Blood plasma becomes interstitial fluid after fluid leaves capillaries.
Circulatory System Fun Facts →Every cell is directly bathed in blood. Most cells exchange materials with interstitial fluid, which sits between the blood capillary wall and the cell surface.
In human skeletal muscle, interstitial fluid fills spaces between muscle fibers and capillaries. Oxygen and glucose pass through this fluid before entering muscle cells.
Muscular System Facts →Intestinal Villi
/ in-TES-tih-nul VIL-ee / · Latin intestinum, gut; villus, shaggy hair
Intestinal villi are finger-like projections of the small intestinal mucosa that dramatically increase absorptive surface area, each containing a central lacteal for fat absorption and a capillary network for nutrient uptake.
Each villus is covered with absorptive cells called enterocytes. These cells have tiny projections called microvilli, also known as the brush border.
Villi and microvilli greatly increase the surface area of the small intestine. This larger surface makes nutrient absorption much more efficient.
Fun Facts About Digestive System →Villi digest food by themselves. Villi mainly absorb digested nutrients, while enzymes and bile help break food down first.
In humans, intestinal villi in the jejunum absorb sugars and amino acids into blood capillaries. Fats enter lymph vessels called lacteals inside many villi.
Circulatory System Fun Facts →