Terrestrial animals are |
osmoregulators that must obtain water from the environment |
Birds, insects, and many reptiles excrete nitrogenous waste in the form of uric acid, which |
reduces water loss compared to other nitrogenous wastes, but requires more metabolic energy to produce |
Freshwater fish excrete nitrogenous wastes as |
ammonia |
E |
The urethra is identified by the letter |
Urine formed by a kidney collects in the ___before being drained from the kidney by the___and transported to the____ |
renal pelvis….ureter….urinary bladder |
B |
Filtrate is formed as fluid is forced through the walls of the glomerulus and, initially, collects in the structure indicated by the letter |
The____are the major blood vessels transporting blood to the kidneys |
renal arteries |
The outer part of the kidney is the |
cortex |
What is the functional unit of a kidney? |
nephron |
An appropriate group of animals to examine to observe a Malpighian tubule would be |
the insects |
As a result of the non-selectivity of the kidney’s filtration of small molecules |
useful substances must be selectively reabsorbed |
The movement of substances out of the glomerulus and into Bowman’s capsule is referred to as |
filtration |
The movement of substances from the blood into the proximal tubule is known as |
secretion |
What is reabsorbed from filtrate? |
sodium chloride, glucose, water and amino acids |
As filtrate moves down the loop of Henle, the surrounding interstitial fluid becomes____ concentrated than the filtrate, so____leaves the filtrate |
more…water |
The most abundant solute in urine is |
urea (and other nitrogenous wastes) |
Glucose is removed from filtrate by |
active transport |
Increases water reabsorption |
ADH secretion, dehydration due to inadequate water intake, sweating, eating salty food |
Increases both water and Na+ reabsorption |
aldosterone release, blood loss, severe diarrhea |
Does not increase water or Na+ reabsorption |
diabetes insipidus, alcohol consumption, caffeine consumption |
Under the influence of antidiuretic hormone (ADH), _____ is produced |
more concentrated urine |
Antidiuretic hormone (ADH) makes the____permeable to water |
collecting duct |
The kidneys are paired organs that |
regulate water and electrolyte balance in terrestrial vertebrates |
What is the correct sequence of flow through the nephron? |
renal corpuslce>proximal tubule>loop of Henle>distal tubule>collecting duct |
What is the driving force for the filtration of blood by the renal corpuscle? |
higher pressure in glomerular capillaries than in surrounding Bowman’s capsule |
Which regions of the nephron function independently of hormonal control for the most part? |
renal corpuscle, proximal tubule, and loop of Henle |
In which region of the nephron is a steep osmotic gradient created? |
loop of Henle |
Which of the following statements best describes the actions of the hormone ADH of the nephron? |
ADH causes the collecting duct to increase water reabsorption by the surrounding tissue under conditions of dehydration |
Osmoregulation regulates |
solute concentrations and balances the gain and loss of water |
Osmolarity determines the |
movement of water across a selectively permeable membrane |
Osmoconformeers are |
isoosmotic with their surroundings and do not regulate their osmolarity |
Osmoregulators expend |
energy to control water uptake and loss in a hyper osmotic or hypo osmotic environment |
Osmoregulation in marine fish |
gain of water and salt ions from food through mouth; excretion of salt ions from gills; osmotic water loss through gills and other parts of body surface; excretion of salt ions and small amounts of water in scanty urine from kidneys |
Osmoregulation in a freshwater fish |
gain of water and some ions in food; uptake of salt ions by gills, osmotic water gain through gills; excretion of salt ions and large amounts of water in dilute urine from kidneys |
Osmoregulatory mechanisms of freshwater fish include |
salt uptake in gills and water excretion in urine |
Osmoregulators must |
expend energy to maintain osmotic gradients |
The fluid with the highest osmolarity is |
seawater in a tidal pool |
Water balance is affected by |
type of wastes, quantity of waste products |
Animals that excrete nitrogenous wastes as |
ammonia need access to lots of water |
Mammals and most adult amphibians convert ammonia to |
the less toxic urea; produced in the liver and carried to the kidneys |
Pros and Cons of Urea |
pros: less toxic, requires less water cons: energetically expensive |
Insects, land snails, and many reptiles including birds mainly excrete |
uric acid |
Uric acid is |
relatively nontoxic and does not dissolve readily in water |
Uric acid is more |
energetically expensive produce than urea |
What nitrogenous waste has the greatest number of nitrogen atoms? |
uric acid |
Nitrogenous wastes excreted depend on |
an animal’s evolutionary history, habitat, environment of the animal egg |
The amount of nitrogenous waste is coupled to |
the animal’s energy budget |
Adaptations of desert animals do not likely include |
nitrogenous waste excreted as ammonia |
An aquatic animal with an internal solute concentration of 500 mOsm/L is placed in a fluid with solute concentration of about 700 mOsm/L. To osmoregulate and survive, the animal must |
pump out salts to keep tissue at 500 mOsm/L. |
Excretory systems regulate |
solute movement between internal fluids and the external environment |
Most excretory systems produce |
urine by refining a filtrate derived from body fluids |
Kidneys, the excretory organs of vertebrates |
function in both excretion and osmoregulation |
The filtrate produced in Bowman’s capsule contains |
salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules |
Molecules are transported actively and passively from the filtrate into the |
interstitial fluid and then capillaries |
Some toxic materials are actively |
secreted into the filtrate |
As the filtrate passes through the proximal tubule |
materials to be excreted become concentrated |
Reabsorption of water continues through |
channels formed by aquaporin proteins |
Movement is driven by the |
high osmolarity of the interstitial fluid, which is hyper osmotic to the filtrate |
What is able to diffuse from the tubule into the interstitial fluid |
salt but not water; filtrate becomes increasingly dilute |
The distal tubule regulates the |
K+ and NaCl concentrations of body fluids, the controlled movement of ions contributes to pH regulation |
The collecting duct carries |
filtrate through the medulla to the renal pelvis |
Urine is hypersomotic to |
body fluids |
The mammalian kidneys ability to |
conserve water is a key terrestrial adaptation |
Hyperosmotic urine can be |
produced only using energy to transport solutes against concentration gradients |
The two primary solutes affecting osmolarity are |
NaCl and urea |
In the proximal tubule, |
filtrate volume decreases but its osmolarity remains the same |
The countercurrent multiplier system involving |
the loop of Henle maintains a high salt concentration in the kidney |
Considerable energy is expended to maintain |
the osmotic gradient between the medulla and cortex |
The collecting duct conducts filtrate |
through the osmolarity gradient, and more water exits the filtrate by osmosis |
Urea diffuses out of the |
collecting duct as it traverses the inner medulla |
Urea and NaCl form the osmotic gradient that |
enables the kidney to produce urine that is hyper osmotic to the blood |
The juxtamedullary nephron is |
key to water conservation in terrestrial animals |
Mammals in dry environment have |
long loops of Henle |
Mammals in fresh water have |
relatively short loops |
Birds have shorter loops of Henle but |
conserve water by excreting uric acid instead of urea |
Other reptiles have |
only optical nephrons but also excrete nitrogenous waste as uric acid |
Freshwater fishes conserve |
salt in their distal tubules and excrete large volumes of dilute urine |
Kidney function in amphibians is similar |
to freshwater fishes |
Marine bony fishes are |
hypo osmotic compared with their environment; their kidneys have small glomeruli and some lack glomeruli entirely; filtration rates are low, and very little urine is excreted |
The counter current multiplier system in the nephrons of mammalian kidneys allows the development of a concentration gradient of salt and urea in the medullary fluid that is |
high enough to develop hyper osmotic urine |
The primary nitrogenous waste excreted by mammals is |
urea, which is less toxic than ammonia |
The osmolarity of the urine is regulated by |
nervous and hormonal control |
Antidiuretic hormone (ADH) increases the |
permeability of the collecting duct epithelium to water; water osmolarity increases, this triggers the release of ADH, which helps to conserve water |
The renin-angiotensin-aldosterone system (RAAS) is part of a |
complex feedback circuit that functions in homeostasis |
A drop in blood pressure near the glomerulus causes the |
juxtaglomerular apparatus (JGA) to release the enzyme renin |
Renin triggers the formation |
of the peptide angiotensin 2 |
Angiotensin 2 |
raises blood pressure and decreases blood flow to the kidneys; stimulates the release of the hormone aldosterone, which increases blood volume and pressure |
ADH and RAAS both increase |
water reabsorption, but only RAAS will respond to a decrease in blood volume |
Atrial natriuretic peptide (ANP) |
opposes the RAAS; ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin |
The two solute model explaining urine production in the nephron states that |
the transport epithelium in the ascending loop of Henle is relatively impermeable to water |
A decrease in the volume of urine excreted would be expected following |
an increase in aquaporin channels in collect duct |
Bio ch. 44
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