The exchange of gases inside the lungs actually occurs inside tiny sacs called :

RRB Staff Nurse Ahmedabad-2015

Applied Physiology

Easy

Appeared in: RRB Staff Nurse Ahmedabad-2015

Explanation

Alveoli are the microscopic, thin-walled air sacs located at the end of the bronchial tree in the lungs.
They are the primary functional units of the respiratory system for gas exchange.
The walls of the alveoli are just one cell thick and are surrounded by a dense network of capillaries, which allows for rapid and efficient diffusion of oxygen into the blood and carbon dioxide out of the blood.

Option A: Bronchi are the larger airways that lead from the trachea to the bronchioles. Their walls contain cartilage and are too thick to allow for efficient gas exchange. Their primary role is air conduction.
Option B: Cilia are microscopic, hair-like projections that line the respiratory tract. Their function is to move mucus and trapped particles upwards, away from the lungs, a process called mucociliary clearance. They do not participate in gas exchange.
Option C: Capillaries are the smallest blood vessels in the body. While gas exchange occurs between the alveoli and the pulmonary capillaries, the capillaries themselves are the vessels containing blood, not the 'tiny sacs' containing air.

Visual 1: Diagram - An illustration of the lower respiratory tract, showing the branching from bronchi to bronchioles and ending in clusters of alveolar sacs. This helps visualize the location of the alveoli.
Visual 2: Microscopic View - A cross-section of an alveolus adjacent to a pulmonary capillary, clearly showing the thin respiratory membrane where gas exchange (O₂ moving into the blood, CO₂ moving out) takes place.

Clinical Relevance

Nursing practice connection: Knowing Anatomy and Physiology of the Respiratory System: Site of Gas Exchange helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding the function of alveoli is fundamental for nurses managing patients with respiratory conditions like pneumonia (inflammation of alveoli), COPD/emphysema (destruction of alveolar walls), and ARDS (damage to the alveolar-capillary membrane), all of which impair gas exchange.
Nursing interventions such as deep breathing exercises, incentive spirometry, and proper positioning are aimed at maximizing alveolar inflation and preventing atelectasis (alveolar collapse).
What if? - If a patient develops pulmonary edema, fluid fills the alveoli. This increases the thickness of the respiratory membrane, severely impairing the diffusion of oxygen and carbon dioxide, leading to acute respiratory failure.

How to Approach the Question

First, break down the question to its core components: the function ('exchange of gases') and the structure ('tiny sacs' in the 'lungs').
This is a factual recall question testing knowledge of respiratory anatomy.
Systematically evaluate each option based on its known physiological role.
Eliminate options whose primary function does not match 'gas exchange'. Bronchi are for conduction and cilia are for cleaning.
Differentiate between the remaining options. Capillaries are blood vessels where exchange happens, but alveoli are the 'sacs' where the air is held for exchange.
Select the option that perfectly matches both the description ('tiny sacs') and the function ('gas exchange').

Concept Tested & Keywords

Concept Tested: Anatomy and Physiology of the Respiratory System: Site of Gas Exchange
Stem keywords: exchange of gases, lungs, tiny sacs
Lead-in keywords: occurs inside
Negative lead-in flag: false

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