MCAT Biology Urinary System Flashcards
The small artery that carries blood toward the capillaries of the glomerulus
Afferent arteriole
The principle mineralcorticoid secreted by the adrenal cortex
Aldosterone
This steroid hormone target the kidney tubules and increases renal reabsorption of sodium
Aldosterone
The __ is the long muscular “tube” that includes the mouth, esophagus, stomach, small intestine, and large intestine
Alimentary canal
A normal blood protein produced by the liver that is converted to angiotensin 1 by renin (secreted by the kidney when blood pressure falls).
Angiotensinogen
When is renin secreted by the kidney?
When blood pressure falls
Angiotensin 1 is further converted to angiotensin 2 by ____
ACE (angiotensin converting enzyme
___ is a powerful system vasoconstrictor and stimulator of aldosterone release, both of which result in an increase in blood pressure
Angiotensin 2
A layer of collagen fibers that separates epithelial tissue from connective tissue is known as __
basement membrane
The region of the nephron that surrounds the glomerulus
Bowmans capsule
The __ collects the plasma that is filtered from the capillaries in the glomerulus
Bowman’s capsule
The portion of the nephron where water reabsorption is regulated via antidiuretic hormone (ADH)
Collecting ducts
This is the final region through which urine must pass on its way to the ureter
Collecting duct
The small artery that carries blood away from the capillaries of the glomerulus
Efferent arteriole
A hormone produced and released by the kidney that stimulates the production of red blood cells by the bone marrow
Erythropoietin
In the kidney __ refers to the movement of plasma across the capillary walls of the glomerulus, into the capsule and tubule of the nephron
Filtration
Filtration at the glomerulus is driven by blood pressure
Filtration
The ball of capillaries at the beginning of the nephron where blood filtration takes place
Glomerulus
The cells of the afferent arteriole at the juxtaglomerular apparatus
Juxtaglomerular cells
__are the baroreceptors that secrete renin upon sensing a decrease in blood pressure, located in the afferent arteriole
Juxtaglomerular cells
The loop of the nephron tubule that dips downward into the renal medulla
Loop of Henle
The __ sets up a concentration gradient in the kidney so that from the cortex to the renal pelvis osmolarity increases
Loop of Henle
The __ of the loop of Henle is permeable to water, but not to sodium
Descending limb of Loop of Henle
The __ of the loop of Henle is permeable to sodium, but not water (here active transport of sodium out of the filtrate occurs)
Ascending Loop of Henle
The cells of the distal tubule at the juxtaglomerula apparatus
Macula densa
These are receptors that monitor filtrate osmolarity as a means of regulating filtration rate.
Macula densa
If a drop in osmolarity is sensed, the macula densa will ___
Dilate the afferent arteriole (to increase blood pressure in the glomerulus and thus increase filtration)
AND
stimulates the juxtaglomerular cells to secrete renin (to raise systemic blood pressure)
The functional unit of the kidney is the__
nephron
This is where blood filtration and subsequent modification of the filtrate occurs
Nephron
The __ empties into the collecting ducts, which empty into the ureter
Nephron
The first portion of the nephron tubule after the glomerulus
Proximal convoluted tubule
The __ is the site of most reabsorption
Proximal convoluted tubule
All filtered nutrients are reabsorbed here as well as most of the filtered water
Proximal convoluted tubule
The movement of a substance from the filtrate (in the renal tubule) back into the bloodstream
Reabsorption
The portion of the nephron after the glomerulus and capsule
Renal tubule
The region of the nephron where the filtrate is modified along its path to becoming urine
Renal tubule
The movement of substances from the blood to the filtrate along the tubule. This increases the rate at which substances can be removed from the body
Secretion
A waste product of protein breakdown, produced by the liver and released into the bloodstream to be eliminated by the kidney
Urea
The capillaries that surround the tubules of the nephron. The ___ reclaims reabsorbed substances, such as water and sodium ions
Vasa Recta
The ___ is responsible for excreting waste by chemically modifying them and releasing them into the bile
Liver
The ___ delas with hydrophobic or large waste products, which cannot be filtered out by the kidney
Liver
The kidney can only eliminate small __ dissolved in plasma
Hydrophils
___ is a carrier of xs nitrogen because free ammonia is toxic
Urea
The __ reabsorbes water and ions (sodium, calcium, etc.) from feces
large intestine
What are the 3 excretory/Homeostatic roles of the kidney?
- Excretion of hydrophilic aste
- Maintenance of constant solute concentration and constant pH
- Maintenance of constant fluid volume (important for blood pressure and cardiac output)
The internal sphincter of the bladder is made of __
smooth muscle (involuntary)
The external sphincter of the bladder is made of ___
skeletal muscle (voluntary)
Why does the medullary pyramid have those pyramid-shaped striations
The collecting ducts
Urine empties fro mthe collecting ducts and leaves the medulla at the tip of the pyramid known as a__
papilla
Each papilla empties into a space called a CALYX, and these calyces converge to form the ___ which is a large space where urine collects, this is what empties into the ureter
Renal pelvis
What are the two components of the nephron?
- Rounded region surrounding the capillaries where filtration takes palce = CAPSULE
- a coiled tube known as the RENAL TUBULE.
- the tubule receives filtrate from the capillaries in the capillaries in the capsule at one end and empties into a collecting duct at the other end. The collecting duct dumps urine into the renal pelvis
Constriction of the efferent arteriole results in __
high pressure in the glomerulus, which causes fluid to leak out of the glomerular capillaries
Roughly 70% of the volume of filtrate is reabsorbed here
Proximal convoluted tubule
The term secretion refers to the movement of substances INTO the filtrate (usually via active transport) most secretion takes place at the __
Distal convoluted tubule and the collecting duct
Before discarding filtrate into the ureter as urine the urine volume and osmolarity are adjusted appropriately in the ____
distal nephron which includes:
Distal convoluted tubule and collecting duct
The distal nephron is controlled by __ and ___
ADH and Aldosterone
Under conditions of low blood volume and high blood osmolarity (high solute concentration in the blood) __ is released
Antidiuretic hormone (vasopressin) from the posterior pituitary gland
___ prevents diuresis (water loss in the urine) by increasing water reabsorption in the distal nephron
ADH
ADH makes ____ permeable to water, without ADH, this region is impermeable to water
distal nephron (Distal convoluted tubule) and the collecting duct
The reason alcohol causes people to have water loss in the urine (diuresis) is that ___
It inhibits ADH secretion by the posterior pituitary
When the blood pressure is LOW, __ is released by the adrenal cortex
Aldosterone
__ causes increased reabsorption of Na+ by the distal nephron
Aldosterone
What is the result of increased reabsorption of Na+ by the distal nephron when aldosterone is released?
it increases plasma osmolarity, which leads to icreased thirst and water retention, which raises the blood pressure
How do ADH and Aldosterone work together?
Aldosterone causes sodium reabsorption, which results in increased plasma osmolarity. This causes ADH to be secreted, which results in increased water reabsorption and thus increased plasma volume
Bowman’s capsule empties into the __
proximal convoluted tubule
___ and __ are located in the renal cortex (outer layer of the kidney)
Bowman’s capsule, and the proximal convoluted tubule
The PCT empties into the __
loop of Henle
The DCT dumps into a__
collecting duct
the __ forms a loop that helps maintain a high concentration of salt in the medulla
Vasa recta
The ___ return to the bloodstream any water that is reabsorbed from the filtrate
Vasa recta
Because the blood in the vasa recta moves in the opposite direction of the filtrate in the nephron, the ___ perform counter current exchange
Vasa recta
The ___ is a specialized contact point between the afferent arteriole and the distal tubule
Juxtaglomerular apparatus (JGA)
At the JGA, the cells in the afferent arteriole are called ___ and those in the distal tubule are known as __
juxtaglomerular cells and those in the distal tubule are known as macula densa
___are baroreceptors that monitor systemic blood pressure
Juxtaglomerular cells (JG)
Explain the renin angiotensin system
- Decrease in blood pressure, JG cells secrete enyme renin
- Renin catalyzes the conversion of angiotensinogen (plasma protein made by the liver) into angiotensin 1
- Angiotensin 1 converted to Angiotensin 2 by angiotensin-converting enzyme (ACE) in the lungs.
- Angiotensin 2 is a powerful vasoconstrictor that immediately raises the blood pressure. It stimulates release of aldosterone which raises blood pressure by increasing sodium (and indirectly) water rettention
The cells of the macula densa are __
chemoreceptors, monitor filtrate osmolarity in the DISTAL TUBULE
When filtrate osmolarity decreases (indicating reduced filtration ratE), the cells of the macula densin stimulate the JG cells to release __
renin
The macula densin also causes ___ increasing blood flow (along with blood pressure and filtration rate) in the glomerulus
direct dilation of the afferent arteriole
when plasma pH is too high,____
HCO3- is excreted in the urine
When the plasma pH is too low,___
H+ is excreted
The enzyme __ is found in epithelial cells throughout the nephron, except in the squamous cells of the thin ascending loop of Henle
Carbonic anhydrase
By exhaling excess CO2, the lungs remove ___
an acid (H2CO3) from the blood, raising the pH
Hyperventilation (deep rapid breathing) ___
raises plasma pH
__ secrete calcitonine when the serum (Ca2+) is too high
C cells in the thyroid gland
Calcitonin causes (Ca2+) to be removed from the blood by
- deposition in bone
- reduced absorption by the gut
- excretion in urine
The function of __ is the opposite that of calcitonin
PTH parathyroid hormone
___ is secrted when the serum (Ca2+) level is too LOW
PTH
When blood oxygen content falls __ is released
erythropoietin, it causes icnreased synthesis of red blood cells in the bone marrow
Circulating blood enters the glomerulus through the __ and exits through the ___
Enters through the afferent arteriole and exits through the efferent arteriole
Aldosterone is released in response to ____ or __
IN response to RAS activation or to an increased serum level of K+
Aldosterone acts on the ___ and ___ to promote reabsorption of Na+ and secretion of K+
Aldosterone acts on the distal convoluted tubule and collecting duct
__ promotes water reabsorption by increasing the permeability of the distal convoluted tubule and collecting duct to water, it also induces vasoconstriction of blood vessels to promote increased blood pressure
ADH
___ is the force extered by a liquid on the walls of its container
Hydrostatic pressure
When blood osmolarity is high the kidneys respond by ______
Increasing water reabsorption and decreasing solute reabsorption
When blood osmolarity is low the kidneys respond by __
decreasing water reabsorption and increasing solute reabsorption
__ increases as solute concentration increases
Osmotic pressure
INCREASED hydrostatic pressure of the renal artery promotes glomerular retention _____
increases urinary output
INCREASED osmotic pressure of filtrate draws fluid back into nephrons;___
increases urinary output
INCREASE of hydrostatic pressure of Bowman’s capsule pushes fluid into glomerular capillaries___
decreases urinary output
INCREASE osmotic pressure of peritubular capillaries draws fluid back into blood stream ___
decreases urinary output
Blood is filtered in the glomerulus by ____ which forces excess fluid and waste products across the porous endothelium and into Bowman’s space
High hydrostatic [blood] pressure
