PhysioEx 9 Intro Information

Each of the million nephrons in each kidney contains two major parts

a tubular component (renal tubule) and a vascular component (renal corpuscle)

The glomerulus is a…

tangled capillary knot that filters fluid from the blood into the lumen of the renal tubule

The function of the renal tubule is to…

process the filtered fluid, also called the filtrate

The beginning of the renal tuble is an…

enlarged end called Bowman’s capsule (or the glomerular capsule) which surrounds the glomerulus and serves to funnel the filtrate into the rest of the renal tubule

Collectively, the glomerulus and Bowman’s capsule are called the…

renal corpuscle

Two arterioles are associated with each glomerulus

an afferent arteriole feeds the glomerular capillary bed and an efferent arteriole drains it

These arterioles (afferent and efferent) are responsible for…

blood flow through the glomerulus

The diameter of the efferent arteriole is…

smaller than the diameter of the afferent arteriole, restricting blood flow out of the glomerulus

The pressure in the glomerular capillaries forces fluid through the…

endothelium of the capillaries into the lumen of the surrounding Bowman’s capsule

Everything in the blood except for the blood cells and plasma proteins is…

filtered through the glomerular wall

From the Bowman’s capsule, the filtrate moves into…

the rest of the renal tubule for processing

The job of the tubule is to…

reabsorb all the beneficial substances from its lumen and allow the wastes to travel down the tubule for elimination from the body

During glomerular filtration, blood enters the glomerulus from the…

afferent arteriole and protein-free plasma flows from the blood across the walls of the glomerular capillaries and into the Bowman’s capsule

The glomerular filtration rate is an…

index of kidney function

In humans, the filtration rate ranges from…

80 to 140 ml/min, so that in 24 hours, as much as 180 liters of filtrate is produced by the glomeruli

The filtrate formed is…

devoid of cellular debris, is essentially protein free and contains a concentration of salts and organic molecules similar to that in blood

The glomerular filtration rate can be altered by…

changing resistance or arteriole hydrostatic pressure

Cellular metabolism produces a complex mixture of…

waste products that must be eliminated from the body

This excretory function is performed by a combination of…

organs, most importantly, the paired kidneys

Each kidney consists of approximately…

one million nephrons

Nephrons carry out three crucial processes

glomerular filtration, tubular reabsorption and tubular secretion

Both the blood pressure in the glomerular capillaries and the filtrate pressure in the renal tubule can have a…

significant impact on the glomerular filtration rate

During glomerular filtration, blood enters the glomerulus from the…

afferent arteriole

Starling forces (hydrostatic and osmotic pressure gradients) drive…

protein-free fluid between the blood in the glomerular capillaries and the filtrate in Bowman’s capsule

Approximately 20% of the blood that enters the glomerular capillaries is…

normally filtered into Bowman’s capsule, where it is then referred to as filtrate

The unusually high hydrostatic blood pressure in the glomerular capillaries…

promotes this filtration

The glomerular filtration rate can be altered by…

changing the afferent arteriole resistance

In humans, approximately 180 liters of filtrate flows into the…

renal tubules every day

The blood pressure supplying the nephron can have a…

substantial impact on the glomerular capillary pressure and glomerular filtration

Under most circumstances, glomerular capillary pressure and glomerular filtration remain…

relatively constant despite changes in blood pressure because the nephron has the capacity to alter its afferent and efferent arteriole radii

Importantly for our body’s homeostasis, a relatively constant glomerular filtration rate of…

125 ml/min is maintained despite a wide range of blood pressures that occur throughout the day for an average human

As filtrate moves through the tubules of a nephron, solutes and water move from…

the tubule lumen into the interstitial spaces of the nephron

The movement of solutes and water relies on the…

total solute concentration gradient in the interstitial spaces surrounding the tubule lumen

The interstitial fluid is comprised mostly of…

NaCl and urea

When the nephron is permeable to solutes or water…

equilibrium will be reached between the interstitial fluid and the tubular fluid contents

Antidiuretic hormone increases the…

water permeability of the collecting duct, allowing water to flow to areas of higher solute concentration, from the tubule lumen into the surrounding interstitial spaces

Reabsorption describes the movement of…

filtered solutes and water from the lumen of the renal tubules back into the plasma

The reabsorbed solutes and water that move into the interstitial space need to be…

returned to the blood, or the kidneys will rapidly swell like balloons

The peritubular capillaries surrounding the renal tubule reclaim the…

reabsorbed substances and return them to general circulation

Peritubular capillaries arise from the…

efferent arteriole exiting the glomerulus and empty into the renal veins leaving the kidney

Without reabsorption, we would…

excrete the solutes and water that our bodies need to maintain homeostasis

Glucose is not very large and is therefore…

easily filtered out of the plasma into Bowman’s capsule as part of the filtrate

To ensure that glucose is reabsorbed into the body so that it can fuel cellular metabolism…

glucose carrier proteins are present in the proximal tubule cells of the nephron

There are a finite number of these glucose carriers in…

each renal tubule cell

If too much glucose is present in the filtrate, it will not…

all be reabsorbed and glucose will be inappropriately excreted into the urine

Glucose is first absorbed by…

secondary active transport at the apical membrane of proximal tubule cells and then it leaves the tubule cell via facilitated diffusion along the basolateral membrane

Both types of carrier proteins that transport these molecules across the tubule membranes are…

transmembrane proteins

Because carrier proteins are needed to move glucose from the lumen of the nephron into the interstitial spaces, there is a limit to…

the amount of glucose that can be reabsorbed

When all glucose carriers are bound with the glucose they are transporting…

excess glucose in the filtrate is eliminated in urine

The concentration and volume of urine excreted by our kidneys will change depending on…

what our body needs for homeostasis

If a person consumes a large quantity of water, the excess water will be…

eliminated as a large volume of dilute urine

When dehydration occurs, there is a clear benefit in being able to…

produce a small volume of concentrated urine to retain water

Aldosterone is a…

hormone produced by the adrenal cortex under the control of the body’s renin-angiotensin system

A decrease in blood pressure is detected by the cells in the…

afferent arteriole, triggering the release of renin

Renin acts as a…

proteolytic enzyme, causing angiotensinogen to be converted into angiotensin I

Endothelial cells throughout the body possess a…

converting enzyme that converts angiotensin I into angiotensin II

Angiotensin II signals the adrenal cortex to…

secrete aldosterone

Aldosterone acts on the…

distal convoluted tubule cells in the nephron to promote the reabsorption of sodium from filtrate into the body and the secretion of potassium from the body

This electrolyte shift, coupled with the addition of antidiuretic hormone, also causes more water to be…

reabsorbed into the blood, resulting in increased blood pressure

ADH is manufactured by the…

hypothalamus and stored in the posterior pituitary gland

ADH levels are influenced by the…

osmolarity of body fluids and the volume and pressure of the cardiovascular system

A 1% change in body osmolarity will cause this hormone to be…

secreted

The primary action of the ADH hormone is to increase the…

permeability of the collecting duct to water so that more water is reabsorbed into the body by inserting aquaporins, or water channels, in the apical membrane

Without water reabsorption, the body would..

quickly dehydrate

Our kidneys tightly regulate the…

amount of water and solutes excreted to maintain water balance in the body

If water intake is down, or if there has been a fluid loss from the body, the kidneys work to…

conserve water by making the urine very hyperosmotic to the blood

If there has been a large intake of fluid, the urine is…

more hypo-osmotic

In the normal individual, urine osmolarity varies from…

50 to 1200 milliosmoles/kg water