Structure and Function of Lungs

Structure and Function

• The lungs are a pair of vital organs located within the thoracic cavity, enclosed by the rib cage.
• They are responsible for gas exchange, a process where oxygen from the air is absorbed into the bloodstream and carbon dioxide, a waste product, is expelled from the body.
• The lungs consist of elastic tissue, comprising millions of tiny air sacs called alveoli.
• This extensive network of alveoli provides a vast surface area for efficient gas exchange.
• The lungs are connected to the atmosphere via the trachea and bronchi.
• These structures progressively branch into smaller airways, ultimately leading to the alveoli.
• The bronchioles, the smallest subdivisions of the bronchi, lead directly to the alveoli.

Structure of the Alveoli

• Alveoli are thin-walled, balloon-like structures, crucial for gas exchange.
• Their thin walls, composed of a single layer of epithelial cells, facilitate the rapid diffusion of gases.
• The walls are surrounded by a dense network of capillaries, tiny blood vessels.
• This close proximity of air and blood allows for efficient gas exchange.
• The alveoli are coated with a surfactant, a lipoprotein substance vital for reducing surface tension within the air sacs and preventing collapse.

Mechanics of Breathing

• Breathing, also known as pulmonary ventilation, involves two phases: inspiration and expiration.
• Inspiration (inhalation) is the process of drawing air into the lungs.
• During inspiration, the diaphragm contracts and lowers, expanding the thoracic cavity.
• This expansion causes reduced pressure within the lungs, drawing air into the airways and alveoli.
• Expiration (exhalation) is the process of expelling air from the lungs.
• During expiration, the diaphragm relaxes, returning to its original dome-like shape.
• This causes the thoracic cavity to decrease in volume, increasing pressure in the lungs and forcing air out.

Gas Exchange

• Gas exchange occurs passively by diffusion, across the thin walls of the alveoli and capillaries.
• Oxygen, from the inhaled air, diffuses from the alveoli into the capillaries.
• Carbon dioxide, a waste product from the body, diffuses from the capillaries into the alveoli.
• The concentration gradient drives this diffusion, with higher oxygen concentration in the alveoli and higher carbon dioxide concentration in the capillaries.
• Hemoglobin, a protein in red blood cells, binds to oxygen, facilitating its transport throughout the body.

Control of Breathing

• Breathing is primarily controlled by the respiratory center in the medulla oblongata of the brain.
• This center monitors the levels of carbon dioxide in the blood.
• Elevated carbon dioxide levels stimulate the respiratory center, leading to increased breathing rate and depth to remove the excess carbon dioxide.
• Other factors like oxygen levels, pH levels and signals from the peripheral nervous system also influence breathing.

Common Lung Diseases

• Various diseases and disorders can affect the lungs, often resulting in impaired gas exchange.
• Examples are asthma, cystic fibrosis, chronic obstructive pulmonary disease (COPD), and lung cancer, each with distinct characteristics and implications for lung function.
• Asthma involves inflammation and narrowing of the airways, while COPD involves progressive damage to the lungs impairing airflow.

Factors Affecting Lung Function

• Age, lifestyle, environmental factors (like exposure to pollutants), and underlying health conditions significantly affect lung function.
• Smoking, for example, is a major risk factor for numerous lung diseases.
• Regular exercise and healthy lifestyle choices are important for maintaining optimal lung function.

This quiz covers the anatomy and physiological functions of the lungs and alveoli. Learn about the gas exchange process and the structure of alveoli that facilitates efficient breathing. Test your knowledge on the vital components of the respiratory system.