Question

The structural and functional unit of the kidney is called?
A) Nephron
B) Nephridia
C) Ureter
D) Urethra

Answer 1

Hint: Waste products from the blood are converted into urine and passed out of the body by various processes that take place inside the millions of tiny units that are present inside the kidney. These units make up the kidneys and help them to maintain the osmolarity, pH balance, ion balance and many more such functions.

Complete answer:
We have two bean shaped kidneys present in our abdomen which filter blood, and remove the waste from it and absorb the needed substances. All these functions are done by tiny units (tissues) that make up the kidneys and they are Nephrons. Nephrons are the structural and functional units of the kidney. They are involved in three very important functions which are – Glomerular Filtration, Tubular reabsorption, Tubular secretion.

The other options are
Nephridia – It is found in invertebrates but is similar to the kidney of vertebrates in function. It also functions in removing metabolic waste from the animal’s body. It can be categorised into – protonephridia and metanephridia.
Ureter – It is also a part of the excretory system and it carries urine from the kidney to the urinary bladder. Each kidney has its own ureter and half of the ureter is present in the abdomen (where the kidney is present) and half in the pelvic region (where the urinary bladder is present).
Urethra – It is also a part of an excretory system which is a tube like structure which connects the urinary bladder to the urinary meatus (opening to the outside) which carries urine outside the body.

Option A is the correct answer.

Additional Information: Nephrons regulate and balance the water and soluble substances present in the blood. It is divided into Glomerulus and Renal tubules.
Glomerulus – Tuft of capillaries formed by a fine branch coming from renal artery called the afferent arteriole.
Renal tubule – It begins with a double walled cup like structure which encloses the glomerulus and is known as Bowman’s capsule. Renal tubule extends further forming proximal convoluted tubule (PCT) which is highly coiled which extends into Henle’s loop having an ascending and descending part. The ascending part extends into distal convoluted tubule (DCT)
Malpighian body/ Renal Corpuscle – Formed by Renal tubule and Bowman’s capsule

Note: Kidneys are divided into outer cortex and inner medulla. Malpighian corpuscle, DCT and PCT are present in the cortex region while the Henle’s loop is in the medulla region. In some nephrons Henle’s loop is very short and extends only a little into the medulla, such nephrons are cortical nephrons. When Henle’s loop is very long that it extends deep into the medulla then such nephrons are known as Juxta medullary nephrons.