The Respiratory System Overview

Study Notes

The Respiratory System

The respiratory system in humans is responsible for taking up oxygen and expelling carbon dioxide, ensuring the continuous flow of oxygen to the body's tissues and the removal of waste gases. The system can be divided into upper and lower airway systems. The upper airway system comprises the nose, paranasal cavities (or sinuses), pharynx (or throat), and oral cavity, while the lower airway system includes the larynx, trachea, stem bronchi, and the intricate network of airways within the lungs, such as the intrapulmonary bronchi, bronchioles, and alveolar ducts.

Upper Airways

The human respiratory system begins with the nose, an external protuberance of an internal space known as the nasal cavity. The nasal cavity is subdivided into a left and right canal by a thin medial cartilaginous and bony wall, the nasal septum. Each canal opens to the face by a nostril and into the pharynx by the choana. The floor of the nasal cavity is formed by the palate, which also forms the roof of the oral cavity. The complex shape of the nasal cavity is due to projections of bony ridges, the superior, middle, and inferior turbinate bones (or conchae), from the lateral wall. These passageways thus formed below each ridge are called the superior, middle, and inferior nasal meatuses. The intranasal space communicates with a series of neighboring air-filled cavities within the skull (the paranasal sinuses) via the nasolacrimal duct, with the lacrimal apparatus in the corner of the eye.

Lower Airways

The lower airway system includes the larynx, trachea, stem bronchi, and intrapulmonary bronchi, bronchioles, and alveolar ducts. The larynx, located at the top of the trachea, serves as the upper end of the respiratory tract and the lower end of the digestive tract. It contains the vocal cords, which produce sound when vibrated. The trachea, reinforced by roughly 20 rings of cartilage, connects the larynx to the lungs.

The stem bronchi branch off from the trachea and enter the lungs, where they divide into smaller airways called bronchioles. At the ends of the bronchioles are tiny sacs called alveoli, which are essential for gas exchange between the air and the blood. Oxygen from inhaled air diffuses from the alveoli into pulmonary capillaries surrounding them, then binds to hemoglobin molecules in red blood cells and is pumped through the bloodstream. Carbon dioxide from deoxygenated blood diffuses from the capillaries into the alveoli and is expelled through exhalation.

Mechanics of Respiration

Respiration is facilitated by a series of coordinated movements involving the diaphragm, the main respiratory muscle, and the intercostal muscles of the chest wall. During inhalation, the diaphragm contracts and the intercostal muscles contract, expanding the internal space of the thorax. This creates a lower pressure in the lungs, drawing air in through the nose or mouth and down the windpipe. During exhalation, the diaphragm relaxes, and the intercostal muscles relax, decreasing the internal space of the thorax, and raising the pressure in the lungs, forcing air out of the body.

Role of the Circulatory System and Blood

The respiratory system is closely linked with the circulatory system, with both systems working together to deliver oxygen to all body cells and remove waste carbon dioxide. The blood, as a carrier for the gases, and the circulatory system (i.e., the heart and the blood vessels) are mandatory elements of a working respiratory system.

Description

Explore an overview of the human respiratory system, including the upper and lower airway systems, the mechanics of respiration, and the role of the circulatory system and blood in oxygen transport. Learn about the anatomy and functions of each component in the respiratory system.