Chapter 49
By: Kayla Nida

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This system is needed to allow for removal of impurities and waste from the body.
Helps maintain homeostasis in the body
◦ Regulating Body temperature
◦ Regulating Blood glucose
◦ Oxygen
◦ pH concentrations

Earthworms Insects
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Contain Nephridia, which are similar to the human kidney.
Obtain fluid from the body through the filtration system called
Nephrostomes
◦ Removes salt through active transport
◦ Forms urine
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Have Malpighian tubules
◦ Urine is not formed by filtration
◦ Waste molecules and potassium are secreted into the tubules trough active transport
◦ Most of the potassium and water is reabsorbed into the circulatory system through the hind gut

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Kidneys first developed among bony fish
◦ Body fluids are hypotonic to surrounding sea water so water leaves their body by osmosis through the gills and urine
◦ Drink large amounts of sea water to compensate
◦ Kidney is needed to get rid of the divalent ions, such as salt
Cartilaginous Fish
Kidney helps to reabsorb urea from the nephron tubule and maintain a blood urea concentration a 100 times higher than mammals
Urea makes the blood isotonic to the sea water, preventing water loss

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Kidney in Amphibians: first terrestrial vertebrate
◦ Identical to fresh water fish
◦ Makes sense because they stay in moist places
◦ Transport sodium across their skin from surrounding water
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Reptiles
Fresh water reptiles have similar kidneys to amphibians
Marine reptiles tend to lose water and obtain a lot of salt
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Process similar to bony fish; eliminate excess salt through salt glands

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Only ones able to produce urine with a higher osmotic concentration than their body fluid
Can excrete waste in small amounts so that more water can be retained in the body
Human kidneys can produce urine that is more than
4.2 times concentrated as blood plasma
Only ones to have loop of Henle that produces the hypertonic urine
Kangaroo rat kidneys are so efficient that it never has to drink water !

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Nitrogen containing by-products that must be removed from the body though urine
◦ Ammonia- toxic to cells and only safe in very dilute concentrations
◦ Urea- mammals excrete ammonia in this form
 water soluble and can be excreted in large amounts through urine
◦ Uric acid- Humans, Apes, and Dalmatians lack enzyme uricase, which converts uric acid into a more soluble derivative and must excrete the uric acid

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Fist sized organ located in the lower back
◦ Juxtamedullary nephrons- long loops that go deeply
Receives blood from a renal artery from which urine is produced
Ureter: where urine drains and carries it to the urinary bladder
Renal pelvis: mouth of the ureter when flared up
◦ Has cup-shaped extensions that receive urine from renal tissue
◦ Tissue is split into an outer renal cortex and inner renal medulla

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into the medulla
◦ Cortical nephrons – shorter loops

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Glomerulus- a group of capillaries in the renal cortex
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Capillaries filter the blood
Filtrate enters the first region of the nephron tubule= Bowman’s Capsule
Proximal convoluted
Tubule- sends filtrate to the loop of Henle
Fluid is then sent to the
Distal Tubule, which drains into the collecting duct
All the collecting ducts merge in the medulla to empty the urine

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Filtration
Reabsorption

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Driven by active transport and secondary active transport
Reabsorbs glucose, amino acids, and other molecules needed by the body
Moves out of tubules and into the blood
Reabsorption
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Moves from the blood and into the tubule to be excreted
Involves the transport of molecules across the capillaries and kidney tubules into the filtrate
Secretion

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Elimination of nitrogenous wastes, potassium, and other ions
Urin’s high hydrogen concentration helps maintain the acid base balance of the blood from 7.35-7.45
Maintains blood volume and pressure because of the excretion of water
◦ More water excreted means lower blood volume and visa-versa
Important for homeostasis

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Include volume of blood, blood pressure, and osmolality of blood plasma
Antidiuretic Hormone (ADH)
◦ Produced by hypothalamus and secreted by pituitary gland
◦ Secreted when a person is dehydrated or eats salty food, making you thirsty
◦ Causes walls of distal tubules and collecting ducts to become more permeable to water= conserving water

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Aldosterone- secreted by the adrenal cortex
◦ Stimulated by the drop in blood sodium concentration
◦ Stimulates the distal convoluted tubules and collecting ducts to reabsorb sodium, decreasing the excretion of sodium in the urine
◦ Promotes secretion of potassium to help regulate the potassium concentrations in the blood
Atrial Natriuretic Hormone (ANH)
◦ Secreted by the right atrium of the heart in response to an increase in blood volume
◦ Promotes excretion of salt and water into the blood to lower the blood volume

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The Kidneys maintain a constant internal environment
When affected by disease, a rise in the blood concentration of waste products, disturbances of electrolyte balance, and failure of blood pressure regulation occur
This causes other systems to develop problems because the homeostasis is thrown off

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Kidney disease- gradual and permanent loss of kidney over time.
◦ Five stages of severity
◦ Cured by replacing the kidney, watching your diet, some antibiotics
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Gout- build up of uric acid in the body because the kidneys cannot process it correctly
Causes joint pain and kidney stones
Diet change and antibiotics are used to help clear it
Nephritis- inflammation of the nephron
Can suffer permanent damage= chronic
Most can be cured but severe cases have lead to death