Introduction.
Structural and functional unit of kidney.
Each kidney contains around “ One Million” nephrons.
Present in the renal cortex as well as in renal medulla.
Two types:
Cortical Nephrons:
Superficial.
Originate in the cortex and extend for a short distance in medulla.
Constitute around 80-90% of the total nephrons.
Juxtamedullary Nephrons:
Lie deeper.
Originate at the junction of medulla and cortex, go deeper in medulla.
Constitute around 10-20% of the total nephrons.
Each nephron consists of two units:
Renal corpuscle. (Filtration Unit) It is made up of,
Glomerulus.
Bowman's Capsule
Renal Tubule. (Transportation Unit) it is made up of,
Proximal Convoluted Tubule (PCT).
Loop of Henle.
Distal Convoluted Tubule. (DCT)
Renal Corpuscle:
It is a filtering chamber where plasma is filtered.
It has two components,
Glomerulus.
Bowman’s Capsule.
Glomerulus is a bunch of capillaries, blood enters in glomerulus via afferent arteriole and exits through efferent arteriole.
Afferent arteriole has a large diameter and efferent arteriole has a smaller diameter, this difference between diameters causes increase in pressure inside glomerulus which facilitates filtration.
Bowman's capsule is a funnel shaped part of nephron surrounding glomerulus.
Bowman's capsule’s outer wall called the parietal layer is separated from the inner wall called the visceral wall by a space called “Capsular Space”.
Bowman's capsule and glomerulus together form a “malpighian body”.
Juxtaglomerular apparatus is a specialized structure of cells that plays an important role in blood pressure maintenance.
“Filtration Membrane” is the contact point between glomerular capillaries and Bowman’s Capsule.
Blood from afferent arteriole enters glomerulus and is filtered i.e. blood cells, protein molecules are retained in capillary while plasma with solutes with smaller size escape from small pores on capillaries to capsular space and then to the renal tubule.
Renal Tubule:
It starts from a bowman's capsule and ends at collecting tubules.
Anatomically it is divided into three parts,
Proximal Convoluted Tubule (PCT).
Loop of Henle.
Ascending Loop of Henle.
Descending Loop of Henle.
Distal Convoluted Tubule (DCT).
Proximal Convoluted Tubule (PCT):
It starts from Bowman’s capsule and continues down the descending loop of Henle.
It has an inner lining of cuboidal epithelium having a microvilli brush border (just like epithelial cells in the small intestine), which increases surface area for fluid absorption.
It absorbs ions like Na & Cl, water and glucose.
It absorbs actively hence contain very large number of mitochondrias to produce ATPs
Loop of Henle:
It is divided into two parts,
Descending Loop of Henle. (part going downwards)
Ascending Loop of Henle. (part going upwards)
It is present between PCT and DCT and has a sharp hairpin like structure.
It deals with maximum fluid absorption, it is more long in animals present in the desert.
Distal Convoluted Tubule (DCT):
The highly coiled part starts after the ascending Loop of Henle.
It contains simple cuboidal epithelium.
It is shorter as compared to PCT.
Collecting Duct:
DCT continues to form collecting ducts.
Collecting ducts are connected to many nephrons.
It contains columnar epithelium.
Commonly Asked Questions.
Draw a well labeled diagram of the Nephron.
With a well labelled diagram discuss the structure of Nephron.
With a well labelled diagram of Nephron discuss the process of Urine formation.