Chapter 44 – Osmoregulation and Excretion
OSMOREGULATION: The regulation of solute and water concentrations in body fluids by organisms living in hyperosmotic, hypoosmotic, and terrestrial environments.
EXCRETION: The disposal of nitrogen-containing waste products of metabolism.
TRANSPORT EPITHELIUM: One or more layers of specialized epithelial cells that regulate solute movements.
NITROGENOUS WASTES: Simple nitrogen compounds produced by the metabolism of proteins, such as urea and uric acid.
AMMONIA: A small, very toxic molecule made up of three hydrogen atoms and one nitrogen atom; produced by nitrogen fixation and as a metabolic waste product of protein and nucleic acid metabolism.
UREA: A soluble nitrogenous waste excreted by mammals, most adult amphibians, and many marine fishes and turtles; produced in the liver by a metabolic cycle that combines ammonia with carbon dioxide.
URIC ACID: An insoluble precipitate of nitrogenous waste excreted by land snails, insects, birds, and some reptiles.
FILTRATION: In the vertebrate kidney, the extraction of water and small solutes, including metabolic wastes, from the blood by the nephrons.
FILTRATE: Fluid extracted by the excretory system from the blood or body cavity. The excretory system produces urine from the filtrate after extracting valuable solutes from it and concentrating it.
SELECTIVE REABSORPTION: The selective uptake of solutes from a filtrate of blood, coelomic fluid, or hemolymph in the excretory organs of animals.
SECRETION: (1) The discharge of molecules synthesized by a cell. (2) In the vertebrate kidney, the discharge of wastes from the blood into the filtrate from the nephron tubules.
EXCRETION: The disposal of nitrogen-containing waste products of metabolism.
Draw, label, and summarize the key functions of the excretory systems (Fig 44.9, p.929) : Most excretory systems produce a filtrate by pressure–filtering body fluids and then modify the filtrate′s contents. This diagram is modeled after the vertebrate excretory system.
Vertebrate / Mammalian (i.e. human) URINARY SYSTEM: the organs and passageways concerned with the production and excretion of urine, including the kidneys, ureters, urinary bladder and the urethra.
RENAL ARTERY: The blood vessel bringing blood to the kidney.
RENAL VEIN: The blood vessel draining the kidney.
URETER: A duct leading from the kidney to the urinary bladder.
URINARY BLADDER: The pouch where urine is stored prior to elimination.
URETHRA: A tube that releases urine from the body near the vagina in females and through the penis in males; also serves in males as the exit tube for the reproductive system.
RENAL CORTEX: The outer portion of the vertebrate kidney.
RENAL MEDULLA: The inner portion of the vertebrate kidney, beneath the renal cortex.
NEPHRON: The tubular excretory unit of the vertebrate kidney.
GLOMERULUS: A ball of capillaries surrounded by Bowman뭩 capsule in the nephron and serving as the site of filtration in the vertebrate kidney.
BOWMAN’S CAPSULE: A cup-shaped receptacle in the vertebrate kidney that is the initial, expanded segment of the nephron where filtrate enters from the blood.
PROXIMAL TUBULE: In the vertebrate kidney, the portion of a nephron immediately downstream from Bowman뭩 capsule that conveys and helps refine filtrate.
DESCENDING AND ASCENDING LIMB OF THE LOOP OF HENLE: The long hairpin turn, with a descending and ascending limb, of the renal tubule in the vertebrate kidney; functions in water and salt reabsorption.
DISTAL TUBULE: In the vertebrate kidney, the portion of a nephron that helps refine filtrate and empties it into a collecting duct.
COLLECTING DUCT: The location in the kidney where filtrate from renal tubules is collected; the filtrate is now called urine.
RENAL PELVIS: Funnel-shaped chamber that receives processed filtrate from the vertebrate kidney뭩 collecting ducts and is drained by the ureter.
CORTICAL NEPHRONS: Nephrons located almost entirely in the renal cortex. These nephrons have a reduced loop of Henle.
JUXTAMEDULLARY NEPHRONS: Nephrons with well-developed loops of Henle that extend deeply into the renal medulla.
AFFERENT ARTERIOLE: The blood vessel supplying a nephron.
EFFERENT ARTERIOLE: The blood vessel draining a nephron.
VASA RECTA: The capillary system that serves the loop of Henle.
Describe/explain the COUNTERCURRENT MULTIPLIER SYSTEM (a picture might help!): A countercurrent system in which energy is expended in active transport to facilitate exchange of materials and create concentration gradients. For example, the loop of Henle actively transports NaCl from the filtrate in the upper part of the ascending limb of the loop, making the urine-concentrating function of the kidney more effective.
ANTIDIURETIC HORMONE (ADH): A hormone produced in the hypothalamus and released from the posterior pituitary. It promotes water rentention by the kidneys as part of an elaborate feedback scheme that helps regulate the osmolarity of the blood.
ALDOSTERONE: An adrenal hormone that acts on the distal tubules of the kidney to stimulate the reabsorption of sodium (Na+) and the passive flow of water from the filtrate.
RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM (RAAS): A part of a complex feedback circuit that normally partners with antidiuretic hormone in osmoregulation.
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