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What are the 8 major functions of the renal system?

1) Excretion of metabolic waste and foreign substances
2) Regulation of water and electrolyte balance
3) Regulation of extracellular fluid volume
4) Regulation of plasma osmolality
5) Regulation of red blood cell production
6) Regulation of vascular resistance
7) Regulation of acid-base balance
8) Regulation of vitamin D production


What is the importance of the kidney in excretion of metabolic waste and foreign substances?

The body’s continuous production of metabolic end products are of no use to the body and are harmful at high concentrations.

Therefore they must be excreted at the same rate as they are produced by the kidney working together with the liver.


What is the importance of the kidney in regulation of water and electrolyte balance?

It maintains a balance in the inputs and outputs of the body and control electrolytes individually as well as conserve fluid volume as needed.


What is the importance of the kidney in regulation of extracellular fluid volume?

Extracellular fluid volume is a consequence of water and electrolyte balance. Blood plasma is a significant component of this and it ensures vascular space is filled with sufficient volume so that blood can circulate normally.


What is the importance of the kidney in regulation of plasma osmolality?

Osmolality is the summed concentration of dissolved solutes and it is altered when inputs or outputs of water and dissolved solids are changed disproportionally. (drinking pure water or a salty meal)

Not only do the kidneys need to excrete water and solutes to match inputs, they have to at rates which maintain the ratio of water and solutes at a near constant value.


What is the importance of the kidney in regulation of red blood cell production?

The stimulus for secretion is a reduction in the partial pressure of O2 in the local environment of secreting cells in the cortical interstitium.

Local drops of oxygenation in the case of anemia caused
by blood loss, arterial hypoxia or inadequate renal blood flow can stimulate secretion of erythropoietin which will stimulate marrow to produce RBCs.


What is the importance of the kidney in regulation of vascular resistance?

The kidneys participate in the production of vasoactive substances via the renin-angiotensin-aldosterone system which exerts major control over vascular smooth muscle.

This influences peripheral vascular resistance and systemic arterial blood pressure.


What is the importance of the kidney in regulation of acid-base balance?

Kidneys maintain a balanced pH through the excretion of acids and bases.


What is the importance of the kidney in regulation of vitamin D production?

Kidneys are involved in the synthesis of vitamin D in the form of calcitriol.


What is the functional unit of the kidney?



What are the 3 layers of the kidney?



What is the medulla of the kidney divided into?

Renal Pyramids that terminate into papilla


Where do the papilla of the renal pyramids lie?

Minor Calyx


What do the minor calyces expand into?

Major Calyx


Where do the major calyces feed into?

Renal Pelvis


What are the major components of the nephron?

Renal corpuscle
Proximal tubule
Loop of Henle
Distal tubule
Collecting duct system


What is the renal corpuscle comprised of?

Glomerular Capillaries
Bowman's Capsule


What is the short segment of the thick ascending limb?

Macula Densa


What are the renin- and angiotensin II–producing cells and where are they located?

They are the granular cells and they are located on the afferent arterioles.


What is the juxtaglomerular apparatus comprised of?

The juxtaglomerular apparatus is composed of the macula densa (MD) of the thick ascending limb, extraglomerular mesangial cells (EGM), and renin- and angiotensin II–producing granular cells (G) of the afferent arterioles (AA).


What are the epithelial cells that cover the capillaries and form the visceral layer of Bowman’s capsule called?



How does plasma ultra filtrate move into Bowman's space?

Plasma ultrafiltrate moves via passive filtration from the glomerular capillaries (glomerulus) into the Bowman’s space.


What forms the filtration barrier?

The capillary endothelium, basement membrane, and foot processes of podocytes form the so-called filtration barrier.


What is special about the capillary endothelium and what solutes does this allow it to pass?

The endothelium is fenestrated and freely permeable to water, small solutes (Na+, urea, and glucose), and most proteins but is impermeable to red blood cells, white blood cells, and platelets.


What is the function of the basement membrane?

It is a porous matrix of negatively charged proteins is thought to function primarily as a charge-selective filter.


What are filtration slits and what is their function?

The processes of the podocytes interdigitate to cover the basement membrane and are separated by apparent gaps called filtration slits.

Filtration slits function primarily as a size-selective filter and keep the proteins and macromolecules that cross the basement membrane from entering Bowman’s space.


Describe the flow through the nephron.

Afferent Arterioles ->
Glomerulus ->
Proximal Tubule ->
Thin Descending Loop of Henle ->
Thin Ascending Loop of Henle ->
Thick Ascending Loop of Henle ->
Macula Densa ->
Distal Tubule ->
Collecting Duct


What is the site of ultrafiltration?



What is the site of high volume, low gradient reabsorption?

Proximal Tubule


What is the site of low volume, high gradient absorption?

Distal Tubule

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