Nephrons: Types, Major Parts, Flow of Fluid

What are nephrons?

the functional unit of the kidney

How many nephrons do we have? How long?

proximally 1 million, constant from birth, and cannot regenerate

What are the two major types of nephrons?

cortical and juxtamedullary nephrons

Cortical nephrons

• how many?

• where are they located

80-85%

renal corpuscles lie in the outer cortex and have short nephron loops that slightly penetrate the medulla 

Cortical nephrons

• what blood supply do their loops receive?

their short nephron loops receive blood supply from the peritubular capillaries

Juxtamedullary nephrons

• how many?

• where are they located

15-20%

renal corpuscles lie deep in the cortex and have long nephron loops that extend deep into the medulla 

Juxtamedullary nephrons

• what blood supply do their loops receive?

heir long nephron loops receive blood supply from the vasa recta

What do juxtamedullary nephrons create?

• what does it do?

vertical osmotic gradient 

keeps interstitial fluid around the nephron to better absorb water, allowing the change of the urines concentration 

Juxtamedullary nephron

• what is another anatomical difference?

has a thin and thick ascending tube of the loop of Henle 

What are the major parts of the nephron?

renal corpuscle and renal tubule

(MP) Renal corpuscle

• function 

• parts?

where blood plasma is filtered

glomerulus and Bowman’s/glomerular capsule

(RC) What is the glomerulus?

• where is it?

is a capillary bed, inside the capsule 

(RC) Bowman’s/Glomerular capsule

• what does it receive?

• what are its layers?

• what is the space in between?

receives filtrate from the glomerulus 

has a parietal and visceral layer 

capsular/Bowman’s space 

(RC) Bowman’s/Glomerular capsule

• visceral layer 

consists of podocytes, and their projections (pedicles) wrap around the glomerular capillaries and form the capsules inner wall

(RC) Bowman’s/Glomerular capsule

• parietal layer 

simple squamous epithelium, forms the outer wall 

(MP) Renal tubule 

• function 

• parts?

reabsorption from fluid into the blood and tubular secretion from blood into fluid

proximal convoluted tubule

loop of Henle

distal convoluted tubule 

(RT) Proximal convoluted tubule

attached to the glomerular capsule

(RT) What does the Loop of Henle consist of?

• where do they begin/end 

descending limb: begins in the cortex, extends downward into the medulla 

ascending limb: turns and returns to the renal cortex

(RT) Distal convoluted tubule

connects and empties to collecting ducts

What do nephrons connect to?

collecting ducts

Vocab: Macula densa

macula densa is a collection of densely staining epithelial cells found in the distal straight tubule of the nephron as it makes contact with the renal corpuscle

Vocab: Juxtaglomerular cells (JG cells)

modified smooth muscle fibers of the afferent arteriole

Vocab: Juxtaglomerular apparatus

JG cells and macula densa help regulate BP within the kidney

Flow of fluid in a CORTICAL nephron 

Glomerular (Bowman's) capsule

Proximal convoluted tubule

Descending limb of the nephron loop

Ascending limb of the nephron loop

Distal convoluted tubule

Collecting duct

Flow of fluid in a JUXTAMEDULLARY nephron 

Glomerular (Bowman's) capsule

Proximal convoluted tubule

Descending limb of the nephron loop

Thin ascending limb of the nephron loop

Thick ascending limb of the nephron loop

Distal convoluted tubule

Collecting duct