BIO 112 Ch 44

ascending limb of the loop of henle

- in this, salt and not water, is able to diffuse from the tubule into the interstitial fluid -the filtrate becomes increasingly dilute

collecting duct

- the collecting duct carries filtrate through the medulla to the renal pelvis -one of the most important tasks is re-absorption of solutes and water -urine is hyperosmotic to body fluids

antidiuretic hormone ADH

-a vasopressin -osmoreceptor cells in the hypothalamus monitor blood osmolarity and regulate release of ADH from the posterior pituitary -when osmolarity rises above its set point, ADH release into the blood stream increases -binding of ADH to receptor molecules leads to a temporary increase in the number of aquaporin proteins in the membrane of collecting duct cells

angiotensin II

-raises blood pressure and decreases blood flow to the kidneys -stimulates the release of the hormone aldosterone, which increases blood volume and pressure

descending limb of the loop of henle

-re-absorption of water continues through channels formed by aquaporin proteins -movement in driven by the highly osmolarity of the interstitial fluid, which is hyperosmotic to the filtrate -the filtrate becomes increasingly concentrated

What substances are generally filtered from the blood by the kidneys?

-sodium -water -urea -glucose

distal tubule

-the distal tubule regulates the K+ and NaCl concentrations of the body fluid - the controlled movement of ions contributes to pH regulation

Under normal conditions, a pair of human kidneys processes what volume of blood each day?

1,600 L

Filtration

A process that separates materials based on the size of their particles; this occurs of the blood in the vertebrate kidneys

Which of the following animals is paired with the correct excretory system unit?

Bird; kidney

What is the correct path of filtrate through a nephron of the kidney as it is processes into urine?

Bowman's capsule, proximal tubule, descending limb of loop of Henle, thin segment of ascending limb, thick segment of ascending limb, distal tubule, collecting duct

To maintain homeostasis freshwater fish must ____.

C) excrete large quantities of water

In which of the following portions of a nephron of the mammalian kidney does the filtrate have the highest osmolarity?

Descending limb of the loop of Henle in the inner medulla

Which of the following would be most likely to increase for an amphibian moving from the aquatic habitat it occupies as a larva to the terrestrial habitat it occupies as an adult?

Energetic cost of excretion

Hagfish (Eptatretus cirrhauts) are a jawless marine vertebrate that are isotonic with their environment and are considered to be osmoconformers. How might this interesting adaptation limit the habitat that the hagfish can tolerate?

Hagfish habitat is limited by the salinity of the environment.

What is the correct path of blood flow through vessels supplying a nephron?

Renal artery, afferent arteriole, glomerulus, efferent arteriole, peritubular capillaries and vasa recta, renal vein

Which animal would most likely be an osmoconformer?

Starfish Most marine invertebrates are osmoconformers. Their osmolarity is the same as that of seawater.

Which is an accurate statement about the anatomy of the human excretory system?

The loop of Henle is located between the proximal tubule and the distal tubule.

glomerulus

a bed of capillaries within Bowman's capsule. Blood pressure forces fluid from the blood across the capillary wall into the capsule; this is the filtrate, which will undergo processing in the long tubule of the nephron.

juxtaglomerular apparatus

a drop in blood pressure near the glomerulus causes this hormone to release the enzyme renin

protonephridium

a network of dead-end tubules connected to external openings; smallest branches of the network are capped by a cellular unit called a flame bulb

uric acid

a relatively nontoxic excretory product that does not dissolve readily in water; can be secreted as a paste with little water loss; it is also more energetically expensive to produce than urea; insects, land snails, reptiles, and birds excrete this

euryhaline

animals can survive large fluctuations in external osmolarity

ammonia

animals that excrete nitrogenous wastes as this need access to lots of water and release this across the whole body surface; fish excrete this

Which of the following has an effect on blood pressure that counters the effect of the hormone aldosterone?

atrial natriuretic peptide

All of the following processes occur in the nephron of the kidney except ____.

blood cell formation -capsular filtration, tubular secretion, cellular respiration, and selective reabsorption all occur

osmoconformers

consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity

osmoregulation

controls solute concentrations and balances water gain and lose

Terrestrial organisms lose water through evaporation. In what ecosystem might an entomologist find a good study organism to examine the prevention of water loss?

desert

metanephridia

each segments of an earthworm has a pair of open-ended one of these; consist of tubules that collect coelomic fluid and produce dilute urine for excretion

As filtrate passes through the long loop of Henle, salt is removed and concentrated in the interstitial fluid of the kidney medulla. Because of this high salt concentration, the nephron is able to __________.

establish a hyperosmotic interstitial medullary concentration

A human who has no access to fresh water but is forced to drink seawater instead will _____.

excrete more water molecules than taken in, because of the high load of ion ingestion

Chloride cells in the gills of marine bony fishes play a role in which step of excretory system function?

excretion

osmoregulators

expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment

In a marine environment, animals that are iso-osmotic relative to their environment ____.

experience no net water loss by osmosis

A juxtamedullary nephron differs from a cortical nephron in that a juxtamedullary nephron ________.

extends far into the inner medulla of the kidney

filtration

filtering of body fluids

The bed of capillaries in a vertebrate kidney where water, urea, and salts are filtered out of the blood is the ____.

glomerulus

stenohaline

having only a narrow tolerance in the osmolarity of the external environment; this animal has the least chance of survival as it must move between fresh water and seawater

hypoosmotic

having total solute concentration less than that of normal extracellular fluid; lose salts by diffusion and maintain water by balance by drinking almost no water and excreting large amounts of dilute urine

Which of the following would have an excretory system that functions without a filtration step?

insects

urea

most terrestrial mammals and many marine species excrete urea, which is less toxic than ammonia; vertebrates produce this in the liver; conversion of ammonia to this is energetically expensive but excretion of this requires less water than ammonia

Most of our nitrogen-containing waste products are a result of ____.

protein metabolism

proximal tube

reabsorbs ions, water, and nutrients; molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries; passes through the proximal tubule

reabsorption

reclaiming valuable solutes

Which type of organism would have the least chance of long-term survival in the given environment?

stenohaline animals that move between fresh water and seawater

secretion

the addition of other substances, such as toxins and excess ions, to the filtrate

The force driving simple diffusion is ____, while the energy source for active transport is ____.

the concentration gradient; ATP

kidneys

the excretory organs of vertebrates, function in both excretion and osmoregulation; the numerous tubules of kidneys are highly organized; the vertebrate excretory system also includes ducts and other structures that carry urine from the tubules out of the kidney and out of the body

osmolarity

the solute concentration of a solution, determines the movement of water across a selectively permeable membrane

atrial natriuretic peptide ANP

this hormone is released in response to an increase in blood volume and pressure and inhibits the release of renin; opposes the RAAS

countercurrent multiplier system

this involves the loop of henle and maintains a high salt concentration in the kidney; allows the vasa racta to supply the kidney w the nutrients without interfering with the osmolarity gradient

iso-osmotic

two solutions having the same osmolarity

The most effective molecule for nitrogenous waste disposal in desert animals would be ____.

uric acid bc it does not require water for excretion

Which of the following is not moved out of or into the filtration of a nephron through active transport by epithelial cells?

water