The Kidney and Osmosregulation (11.3)
Osmosregulation vs Osmoconformation
The Kidney is all about osmoregulation!
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Osmolarity is the total solute concentration in a cell or organism (See Topic 1.4). Osmoregulation is a form of homeostasis that attempts to balance the osmolality of solutes within the body. Animals are either osmoregulators and osmoconformers.
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Removal of Nitrogen
Animals break down amino acids (proteins) which produce a nitrogen waste product that is toxic to organsisms. This must be excreted. Different organisms produced different kinds of nitrogen waste:
Arthropods (insects, spiders, crabs etc)
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Nitrogen waste and evolution The type of nitrogen waste an organism produces is correlated with evolutionary history and habitat.
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Malpighian TubulesMalpighian Tubules are a branch off intestinal tract of arthropods. Ions and uric acid are actively transported into lumen of the tract which draws water by osmosis from hemolymph (tissue) into the lumen. The tubules empty the contents of the lumen into the gut. In the hindgut, most water and salts are reabsorbed and nitrogenous waste is excreted as feces.
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Kidney Structure
Note that the kidney is found about midway up your abdomen, generally speaking closer to your spine. They are shaped like a bean. Parts are labeled on diagram. You must be able to draw and label the kidney!
Functions of the following parts:
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kidney blood composition
Blood enters the kidney through the renal artery and exits the kidney after filtration through the renal vein. Below is a comparison of what is in the blood before entering the kidney and after it exits the kidney.
- Note the removal of toxins, non-metabolized substances, and nitrogen products (such as urea/ ammonium).
- Compared to the maintenance of the proteins still in the blood (hormones, blood clotting factors, etc.), and the balancing of salt concentrations.
- The change in CO2, O2 , glucose concentrations deals with the use of the oxygen and sugar by the kidney cells to carry out the functions necessary for transport and energy (cellular respiration)
Kidneys filter about 1/5 of the volume of plasma from the blood. The filtrate contains: all substances in plasma except for large proteins that are not filtered. It then ACTIVELY REABSORBS specific substances that the body needs and what is unwanted is passed out of the body through urine.
Nephron Structure
Nephron is the functional unit of the kidney.
Note that the nephron itself is the tube with the filtrate within it. However, a system of capillaries follows the trajectory of the nephron and reabsorbs materials as needed. |
Nephron Overview
Three stages of nephron function:
- Glomerular Filtration (Bowman’s capsule) --> conducts Ultrafiltration
- Tubular reabsorption and secretion (tubules and loop of Henle) --> active and passive transport of minerals
- Water conservation (Collection duct)--> acted on by the Antidiuretic Hormone (ADH)
- Note that multiple nephrons empty into a single collecting duct which will empty into the urether
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Glomerulus & the Bowman’s Capsule
Glomerulus and Bowman’s Capsule facilitate ultrafiltration
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3 part filtration system:
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Proximal Convoluted Tubule
Proximal Convoluted Tubule (PCT) reabsorbs useful substances from the glomerular filtrate by active transport into the blood
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Some secretion also occurs in this from the blood stream into the nephron. Drugs, ammonia, and other large toxins unable to be filtered in the bowman's capsule can be actively transported into the nephron (secreted) for removal.
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The Loop of Henle
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Dehydration vs Overhydration
Dehydration (not enough water in the blood) vs Overhydration (overconsumption of water that dilutes solutes) is regulated by the collecting duct and the Antidiuretic Hormone (ADH), which regulateds the water in the blood stream through homeostasis.
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ANTIDIURETIC HORMONE (ADH) AND THE COLLECTING DUCT
Antidiuretic Hormone (ADH) controls the reabsorption of water from the nephron (Collecting duct) into the blood stream. This is a homeostatic response to water level carried out by the distal convoluted tubule and the collecting duct.
Regulation of Water Balance |
How it works...
When the pituitary gland releases ADH (vasopressin):
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Kidney Failure treatment
Reason for kidney failure are varied but diabetes or chronic high blood pressure (hypertension) resulting from diabetes are a primary cause.
Treatment can included the following:
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Urinalysis
Many diseases and drug abuse can be detected through urinary analysis as drugs are filtered through the Kidney.
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