Class 11 · Breathing and Exchange of Gases

Respiratory Tract Structure & Function — NEET Biology

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We have a pair of external nostrils opening out above the upper lips. It leads to a nasal chamber through the nasal passage. The nasal chamber opens into the pharynx, a portion of which is the common passage for food and air. The pharynx opens through the larynx region into the trachea. Larynx is a cartilaginous box which helps in sound production and hence called the sound box. During swallowing glottis can be covered by a thin elastic cartilaginous flap called epiglottis to prevent the entry of food into the larynx. Trachea is a straight tube extending up to the mid-thoracic cavity, which divides at the level of 5th thoracic vertebra into a right and left primary bronchi. Each bronchi undergoes repeated divisions to form the secondary and tertiary bronchi and bronchioles ending up in very thin terminal bronchioles. The tracheae, primary, secondary and tertiary bronchi, and initial bronchioles are supported by incomplete cartilaginous rings. Each terminal bronchiole gives rise to a number of very thin, irregular-walled and vascularised bag-like structures called alveoli. The branching network of bronchi, bronchioles and alveoli comprise the lungs. We have two lungs which are covered by a double layered pleura, with pleural fluid between them. It reduces friction on the lung-surface. The outer pleural membrane is in close contact with the thoracic

🖼️Related NCERT figure: Diagrammatic view of human respiratory system showing a cross-sectional view. The diagram shows the epiglottis, larynx, trachea, bronchus, lungs (left lung sectioned), heart, diaphragm, and detailed structures including pleural membranes, alveoli, pleural fluid, and bronchioles. The cut end of rib is also visible. (Figure 14.1 Diagrammatic view of human respiratory system (sectional view of the left lung is also shown))
NCERT Biology · Class 11 · Chapter 14 · Paragraph 5
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Which of the above statements are NOT correct? S1: The larynx is a cartilaginous box, often referred to as the sound box, due to its role in sound production. S2: The pharynx serves as a common passage for food and air, opening into the larynx region which then leads to the trachea. S3: The glottis, the opening into the larynx, is covered by a thin elastic cartilaginous flap called the epiglottis during breathing to prevent food entry. S4: The trachea, primary bronchi, and initial bronchioles are supported by complete cartilaginous rings to prevent their collapse. S5: The respiratory or exchange part of the human respiratory system is responsible for transporting atmospheric air to the alveoli, clearing it from foreign particles, humidifying it, and bringing it to body temperature.

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