Question

Mention the respiratory unit of lungs and excretory unit of kidneys.

CBSE Class X Science VSA (1 Mark)

Answer 1

♦ The respiratory unit of lungs are alveoli.

The pulmonary alveoli are the terminal diverticula of the bronchial tree, in which the gas exchange takes place between the inspired air and the blood.
Each adult lung adds about 350 million alveoli, making a total of 700 million alveoli between the two lungs. If we stretch them, they would occupy about 75 square meters.

They are evaginations of the epithelium of the air ducts with a single opening for the gases to leave and enter, controlled by the action of a sphincter of smooth muscle. Its walls, called alveolar septa, provide a large increase in the exchange surface. The alveoli are located next to each other separated by interalveolar septa, which are very thin since they are formed by the simple flat epithelium of an alveolus, its basal lamina, connective tissue with an abundant network of blood capillaries, basal lamina, and the simple flat epithelium of the neighboring alveolus. In addition, the walls of the alveoli contain the sphincter of smooth muscle, elastic fibers and collagen III (reticulin). If the elastic fibers fail, the alveoli distend causing the disappearance of the alveolar sac divisions and the inability to make the exchange. In some alveoli there is a pore that communicates with the light of the adjacent alveolus. These pores are called Kohn pores.


♦ The excretory unit of kidneys are nephrons.

The nephron is the basic structural and functional unit of the kidney, responsible for the purification of the blood. Its main function is to filter the blood to regulate water and soluble substances, reabsorbing what is necessary and excreting the rest as urine. It is located mainly in the renal cortex.


The nephron is the functional unit of the renal parenchyma. In humans, each kidney contains around 1,000,000 to 1,300,000 nephrons.The structure of the nephron is complex, it is composed of a renal corpuscle in communication with a renal tubule. Malpighi's renal corpuscle is a spheroidal structure, constituted by Bowman's capsule and the ball of hair contained inside or glomerulus. The capsule, lined internally by a flattened epithelium, has two openings: the vascular pole, through which the afferent arteriole penetrates and the efferent arteriole emerges, and the urinary pole, which communicates with the renal tubule. The urinary space extends between the capsule and the glomerular ball, where the plasma ultrafiltrate is collected.

The nephron is an important part of the homeostatic mechanism, which regulates by filtration, absorption and excretion the amount of water, salts, glucose, as well as urea, and many other metabolites of the catabolism of fats, lipids and proteins.

Answer 2

Answer:

* The respiratory unit of lungs are alveoli.

* The excretory unit of kidneys are nephrons.

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