CBSE Class 10 Answered

Respiratory system in human beings:

The respiratory system in human beings consists of the nose, pharynx, larynx, trachea, bronchi and lungs.

• Air is taken in through the nostrils.
• Nostrils further continue into the nasal cavity.
• There is a bony plate called the palate, which separates the oral cavity from the nasal cavity.
• Nasal cavity opens into the pharynx.
• The pharynx is a muscular chamber acting as a common passage for the windpipe or trachea and the food pipe or oesophagus.
• It is connected to the larynx through a slit-like opening called the glottis.
• The larynx connects the pharynx to the trachea.
• The trachea shows the presence of cartilaginous rings.
• The cartilaginous rings provide flexibility thus, facilitating continuous air flow.
• The inner wall of the trachea is lined by a mucous membrane consisting of ciliated columnar epithelium.
• The trachea divides into two branches or tubes called bronchi, one of which enters the right lung and the other enters the left lung.
• The bronchi have cartilaginous rings for distention.
• Each bronchus divides into fine secondary bronchi. These bronchi further divide into finer tertiary bronchi. In the lungs, each bronchus finally divides into finer and smaller branches called bronchioles.
• The bronchioles further divide to form smaller terminal bronchioles.
• The bronchioles divide repeatedly to form a cluster of tiny air chambers called air sacs or alveoli.
• Alveoli have thin and moist walls which enable gaseous diffusion with blood capillaries.
• The lungs are a pair of spongy and elastic respiratory organs protected by a bony rib cage.
• The base of the lungs rests on the diaphragm.
• Each lung is covered by two membranes. The inner membrane is called the inner or visceral pleura and the outer membrane is called the outer or parietal pleura.
• The diaphragm is a curved, musculo-fibrous sheath which separates the thoracic cavity from the abdominal cavity.
• The diaphragm plays a major role during respiration.