Question

Assign the specific functions to the following organs with respect to excretion.

(a) Kidneys

(b) Glomerulus and Bowman's capsule.

(c) Tubular part of the nephron

(d) Urethra

(e) Urinary bladder

Answer 1

Excretion:

1. Excretion can be defined as the process of removal or expulsion of waste from the cells of the body of living organisms.
2. The different organs or parts of the body performing excretion form the excretory system.

(a) Kidneys:

1. Kidneys are the bean-shaped vital organs located on either side of the excretory system.

Function:

1. It is the site for urine formation.
2. Blood is purified in the millions of nephrons present inside the kidneys.
3. Urine is a liquid that is generated from the body of animals after the filtration of blood.

(b) Glomerulus and Bowman’s Capsule:

1. Bowman’s Capsule is the funnel-shaped structure from which the tubular part of the nephron emerges.
2. Function: It encloses the glomerulus.
3. Glomerulus is the tuft of blood capillaries enclosed within the Bowman's capsule.
4. Function: It is the site for ultrafiltration, as the capillaries provide a space for the exchange of waste materials through their thin membranous walls.

(c) Tubular part of the nephron:

1. It consists of a Distal convoluted tubule, Proximal convoluted tubule, and Henle's loop.
   1. Henle's loop: It is a U-shaped or hair-pin like structure that consists of a descending limb and an ascending limb. Useful substances, ions, and water are reabsorbed here.
   2. Distal convoluted tubule: It is a part of the nephron present between the loop of Henle and the collecting tubule. The walls of these tubules consist of mitochondria which provide the energy for active transport. Its primary function is calcium reabsorption.
   3. Proximal convoluted tubule: It is the part of the nephron which is present between the Bowman's capsule and Henle's loop. It helps in the reabsorption of glucose and other organic substances.

(d) Urethra:

1. It is a canal-like structure or a passage that extends from the neck of the urinary bladder and connects to the exterior.
2. In females, it opens by a urethral orifice in front of the vaginal aperture and helps in the excretion of urine only.
3. In males, it functions as the common passage for both urine and semen (a whitish fluid that contains the male gamete, sperm).

(e) Urinary bladder:

1. The urinary bladder is a muscular sac or pouch-like structure which stores urine.
2. When the urinary bladder becomes full, its muscles contract and signal the brain and the person feels like urinating.
3. The act of urinating is termed micturition
4. It functions to store the urine temporarily.