Lungs

Respiratory system (lungs, bronchi, trachea) on the left side, alveoli and their cellular components on the right side

The lungs supply oxygen to the rest of the body and remove carbon dioxide.

The lungs are made up of millions of tiny air sacs called alveoli.

Oxygen passes through the walls of these air sacs and is absorbed into the bloodstream. Carbon dioxide passes out of the alveoli to be released from the blood into the airways.

Each lung is divided into lobes and smaller subdivisions called segments.

The right lung consists of three lobes: upper, middle and lower, The left lung has only two: upper and lower.

Below you'll find tutorials and quizzes on the anatomy and physiology of the lungs, using interactive animations and diagrams. Learn more about the respiratory system with this quiz study guide.

The bronchiole wall featured image with zoom-in anatomy and cross section
Bronchioles of the lung: anatomy and function

A zoomed-in cross-section perspective demonstrating the anatomy of the bronchiole wall. Ciliated simple columnar cells, smooth muscle, folded epithelium, and alveoli are labeled.
An expanded view of the thorax magnifying the pleura
Pleural cavity and pleura

Each lung is enveloped in a double-membrane pleural sac (visceral and parietal layer). A thin layer of watery fluid is secreted into the pleural cavity that separates the layers.
The featured image for the lung surfaces tutorial
Lungs Anatomy | Shapes and Surfaces of the Lungs

The anatomical landmarks and surfaces of the right and left lungs are demonstrated, including the mediastinal space, with labeled illustrations.
A figure demonstrating the respiratory system including alveoli, lungs, trachea and sagittal view of the mouth.
Respiratory System Anatomy – Major Zones & Divisions

The respiratory is separated into the conducting zone and the respiratory zone.
The conducting zone include structures that facilitate air to move in and out of the lungs.
The respiratory zone allow inhaled oxygen to diffuse into the lung capillaries in exchange for carbon dioxide.
Mediastinal view of the lungs
Lung Lobes and Fissures

The lungs are anatomically and functionally divided into large subunits called lobes. Each lobe receives air from its own secondary bronchus and is separated from its neighbors by fissures.
The segments of the lung are highlighted in the right and left lung
Bronchopulmonary Segments of the Lungs | Lung Segments | Tertiary Bronchi

An interactive demonstration of the bronchopulmonary segments featuring the iconic GBS illustrations. The segments of the right and left lung are highlighted and labeled.
Zoom-in and highlighted in green of the seconcary pulmonary lobules
Secondary lung lobules

Walls of connective tissue (or septa) partitioned the bronchopulmonary segments into many polygonal-shaped secondary pulmonary lobules. A secondary pulmonary lobule typically contains 3-5 terminal bronchioles.
A zoom-in of the secondary lobule and alveolar duct
Lung alveoli: anatomy and structure

This tutorial reviews the alveolar ducts which contain many cup-shaped alveoli. At each end of alveolar duct are alveolar sacs. The alveoli share a common opening to the alveolar duct.
Zoomed-in lung alveolus which contains Type I/II cells, and the alveolus is found in alveolar sac which in turn located in pulmonary lobule
Lung Alveolus Structure – Lung Alveoli Anatomy

The alveolar sac contains two types of cells :Type 1 and type 2 cells. Type 1 cells secrete pulmonary surfactant, keeping the alveolar walls from sticking together as they deflate in exhalation.

Zoom-in image of respiratory membrane
Respiratory Membrane and Gas Exchange

An interactive demonstration of the structure of the respiratory membrane and the mechanism of gas exchange occurring in the lungs.