Key terms
75 terms- Homeostasis§49.1
- Maintaining internal conditions within an optimal range
- Intracellular compartment§49.1
- Body water held inside cells
- Extracellular compartment§49.1
- Interstitial fluid plus blood plasma; the part that exchanges with the environment
- Osmosis§49.1
- Diffusion of water across a semipermeable membrane toward higher solute concentration
- Osmotic pressure§49.1
- Pressure required to balance the pressure created by water movement
- Osmolarity§49.1
- Osmotically active moles of solute per liter of solution
- Tonicity§49.1
- A solution's ability to change a cell's volume by osmosis
- Hypertonic§49.1
- Higher solute concentration; a cell placed in it shrinks
- Hypotonic§49.1
- Lower solute concentration; a cell placed in it swells
- Isotonic§49.1
- Equal solute concentration; no net water movement
- Osmoconformer§49.1
- Animal in osmotic equilibrium with its environment (most marine invertebrates, hagfish)
- Osmoregulator§49.1
- Animal holding blood osmolarity constant despite the environment
- Transport epithelium§49.1
- Specialized epithelial layer where water and ions are exchanged with the environment
- Deamination§49.2
- Removal of the amino (—NH₂) group, the first step in amino acid catabolism
- Ammonia (NH₃)§49.2
- Immediate nitrogen by-product; highly toxic, needs lots of water to excrete
- Urea§49.2
- Water-soluble, far less toxic nitrogen waste made in the liver
- Uric acid§49.2
- Only slightly soluble nitrogen waste; precipitates as a solid, saving water
- Guano§49.2
- The pasty white uric acid material in bird droppings
- Uricase§49.2
- Enzyme converting uric acid into the more soluble allantoin
- Allantoin§49.2
- Soluble derivative of uric acid made by most mammals
- Gout§49.2
- Painful condition from uric acid accumulating in human joints
- Contractile vacuole§49.3
- Osmoregulatory organelle of protists and sponges
- Protonephridia§49.3
- Branching flatworm tubules ending in flame cells; open only to the outside
- Flame cell§49.3
- Bulblike ciliated cell that draws fluid into a protonephridium
- Nephridia§49.3
- Earthworm tubules open to both the inside and the outside of the body
- Nephrostome§49.3
- Funnel-shaped opening of a nephridium that receives coelomic fluid
- Filtration§49.3
- Pressure-driven fluid formation through small openings that exclude large molecules
- Reabsorption§49.3
- Transport OUT of the tubule and back into body fluids or blood
- Secretion§49.3
- Transport of ions or molecules FROM body fluid INTO the tubule
- Antennal glands§49.3
- Excretory organs of crustaceans; filter then reabsorb
- Malpighian tubules§49.3
- Insect excretory organs branching off anterior to the hindgut; secrete, never filter
- Nephron§49.4
- Repeating functional unit of the kidney; about a million per human kidney
- Glomerulus§49.4
- Ball of capillaries in the cortex where blood is filtered under pressure
- Bowman's capsule§49.4
- Cup that surrounds the glomerulus and receives the filtrate
- Teleost§49.4
- Bony fish; freshwater and marine species face opposite osmotic problems
- Elasmobranch§49.4
- Cartilaginous fish (shark, ray) that retains urea to stay isotonic to seawater
- Salt gland§49.4
- Nasal or orbital gland of marine birds and reptiles that excretes excess salt
- Cloaca§49.4
- Shared digestive and urinary exit where extra water is reabsorbed from urine
- Loop of Henle§49.4
- Nephron loop found only in mammals and birds; builds the medullary gradient
- Metabolic water§49.4
- Water produced by aerobic cellular respiration; the kangaroo rat lives on it
- Renal artery§49.5
- Vessel delivering blood to the kidney
- Ureter§49.5
- Tube carrying urine from kidney to urinary bladder
- Urinary bladder§49.5
- Organ that stores urine before elimination
- Urethra§49.5
- Tube that carries urine out of the body
- Renal pelvis§49.5
- Funnel-like flared mouth of the ureter inside the kidney
- Renal cortex§49.5
- Outer kidney tissue containing glomeruli and convoluted tubules
- Renal medulla§49.5
- Inner kidney tissue holding the loops of Henle and the salt gradient
- Juxtamedullary nephron§49.5
- Nephron with a long loop dipping deep into the medulla
- Cortical nephron§49.5
- Nephron with a short loop, located mostly in the cortex
- Afferent arteriole§49.5
- Larger vessel feeding the glomerulus
- Efferent arteriole§49.5
- Smaller vessel draining the glomerulus; the size mismatch creates filtration pressure
- Peritubular capillaries§49.5
- Second capillary bed around the tubules; the site of reabsorption and secretion
- Vasa recta§49.5
- Capillary loops around the loop of Henle that preserve the medullary gradient
- Proximal convoluted tubule§49.5
- Cortical segment reabsorbing all nutrients and two-thirds of NaCl and water
- Descending limb§49.5
- Permeable to water, not to NaCl; water leaves here
- Ascending limb§49.5
- Impermeable to water; NaCl leaves here (thick portion pumps Na⁺ actively)
- Distal convoluted tubule§49.5
- Cortical segment after the loop; ADH, aldosterone, and K⁺/H⁺ handling act here
- Collecting duct§49.5
- Descends through the medulla; final adjustable site of water reabsorption
- Countercurrent multiplier system§49.5
- Loop of Henle mechanism that builds the hypertonic renal medulla
- Countercurrent exchange§49.5
- Vasa recta arrangement that supplies blood without washing out the gradient
- Milliosmolar (mOsm)§49.5
- Unit of the medullary gradient: 300 cortex, 600 outer medulla, 1200 inner medulla
- Transport maximum (saturation)§49.5
- Carrier limit; renal glucose carriers saturate near 180 mg/100 mL blood
- Diabetes mellitus§49.5
- Blood glucose exceeds the reabsorption limit, so glucose appears in the urine
- Aquaporins§49.5
- Water channels inserted into collecting duct membranes by ADH
- Antidiuretic hormone (ADH)§49.6
- Made in the hypothalamus, released by the posterior pituitary; conserves water
- Osmoreceptors§49.6
- Hypothalamic sensors that respond to rising plasma osmolarity
- Diabetes insipidus§49.6
- Lack of ADH; constant excretion of large volumes of dilute urine
- Aldosterone§49.6
- Adrenal cortex hormone: reabsorb Na⁺ and water, secrete K⁺
- Juxtaglomerular apparatus (JGA)§49.6
- Cells between the distal tubule and afferent arteriole that sense low blood flow
- Renin§49.6
- Enzyme from the JGA that converts angiotensinogen to angiotensin I
- Angiotensinogen§49.6
- Plasma precursor protein acted on by renin
- Angiotensin II§49.6
- Constricts blood vessels and triggers aldosterone release from the adrenal cortex
- Renin-angiotensin-aldosterone system (RAAS)§49.6
- Pathway linking low blood pressure or Na⁺ to salt and water retention
- Atrial natriuretic peptide (ANP)§49.6
- Hormone from the stretched right atrium; opposes aldosterone, dumps salt and water
- Diuretic§49.6
- Drug that increases urine output, often by blocking NaCl reabsorption