Cortical and juxtamedullary nephrons.

Differences and similarities

Keywords :glomerulus| Cortical nephron| Juxtamedullary nephron|Vasa Recta| Loop of Henle| Filtration

 Size and shape of Kidneys

 A kidney is a bean-shaped structure with convex and concave borders. There is a recess in the concave wall known as renal-hilum, through which the renal artery enters and the renal vein and ureter exit.  The weight of each kidney is about 150 grams.  Each kidney is 10 cm long, 5 cm wide, and 2.5 cm thick- roughly about the size of a fist.

Gross structure of kidney: in the vertical section of the kidney, there are two layers:

• Red outer cortex is more, and
• Pale inner medulla is smaller than the cortex.The renal medulla receives little portion of the renl blood flow,but oxygen consumption is very high.It is very sensitive to hypoxia,hypotension and reduction of blood flow.(medulla renis in Latin means marrow of the kidney)

 There are  10 to 15 pyramids in the medulla that terminate medially in the renal papilla and project in the minor calyces.  The minor calyces join to form two major calyces which open in the renal pelvis.  The renal pelvis continues as a ureter and ends in the urinary bladder.

Microscopic structure

  In each kidney, 1 to 1.5 million nephrons are present.  However, they are tiny, only 45 to 65 mm in length.

Types of nephrons:

There are two types of nephrons

• Cortical nephrons, and
• Juxta -medullary nephrons

 Different parts of the nephron

 1.  Bowman’s capsule

 2.  Glomerulus tuft of capillaries

 3.  Proximal convoluted tubule

  4.  Loop of Henle

         Descending  part

         A thin loop of Henle, and

    Thick ascending part of the loop of Henle

  5.  Distal convoluted tubule, and

  6.  Collecting tubule.

Differences

		Cortical nephron	Juxtamedullary nephron
1.	Presence of glomerulus	in upper cortical area	near the junction of cortex and medulla
2.	Size of glomerulus	small	Large
3.	% of nephron	80-85%	20-15%
4.	Loop of Henle	Small extends up to the outer layer of medulla	Large and extends deep in the medulla
5.	Efferent arterioles Diameter Forms	Diameter is large Peritubular capillaries	Diameter is small Vasa Recta
6.	Filtration rate	Slow	Fast
7.	Responsible for	Filtration of blood, excretion of waste and urine formation	Concentration or dilution of urine

Similarities

		Cortical nephron	Juxtamedullary nephron
1.	Structure Renal corpuscles Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct	same	same
2.	Renal corpuscles,PCT,DCT, and collecting ducts are in the cortex	Same	Same
3.	Function: Filtration ,excretion	Same	Same