The respiratory system is intricately designed to facilitate the exchange of gases—specifically, oxygen (O2) and carbon dioxide (CO2)—between the environment and the body.
Here are the realistic diagrams of the human respiratory system, detailed and scientifically accurate, illustrating the respiratory system's structure.
This system can be anatomically divided into two main parts: the upper respiratory tract and the lower respiratory tract.
Each part includes various structures that contribute to the process of breathing and gas exchange.
Upper Respiratory Tract
1. Nose and Nasal Cavity:
The nose is the primary entry point for air.
The nasal cavity, lined with hair and mucous membrane, warms, moistens, and filters the incoming air.
The mucous traps particles like dust and microbes, while the cilia (tiny hairs) move the mucous toward the throat to be swallowed.
2. Pharynx (Throat):
A muscular tube that serves both respiratory and digestive systems, the pharynx connects the nasal cavity and mouth to the larynx (for air passage) and the esophagus (for food passage).
It's divided into three regions: the nasopharynx, oropharynx, and laryngopharynx.
3. Larynx (Voice Box):
Located below the pharynx, the larynx is a cartilaginous structure that houses the vocal cords.
It functions as a passageway for air and prevents food from entering the trachea, thanks to the epiglottis—a flap of tissue that closes during swallowing.
Lower Respiratory Tract
1. Trachea (Windpipe):
A rigid tube that descends from the larynx to the chest, where it divides into the right and left bronchi.
The tracheal walls are supported by C-shaped rings of cartilage, which prevent the trachea from collapsing and maintain an open airway.
2. Bronchi and Bronchial Tree:
The trachea bifurcates into the right and left main bronchi, each entering a lung. Inside the lungs, these bronchi branch into smaller secondary (lobar) bronchi, then into tertiary (segmental) bronchi, and continue to divide into even smaller bronchioles.
This branching resembles a tree, hence the name "bronchial tree."
3. Bronchioles:
The smallest air passages in the lungs, bronchioles, lead to the alveolar ducts.
Unlike the larger bronchi, bronchioles do not have cartilage in their walls but contain smooth muscle that can constrict or dilate, regulating airflow.
4. Alveoli:
Tiny, balloon-like air sacs at the end of the alveolar ducts, where gas exchange occurs.
Each alveolus is surrounded by a network of capillaries.
The walls of the alveoli and capillaries are extremely thin, facilitating the diffusion of O2 into the blood and CO2 out of the blood.
Additional Structures
1. Pleurae:
Double-layered membranes surrounding each lung and lining the chest cavity, providing lubrication and facilitating lung movement during breathing.
2. Diaphragm:
A major muscle of respiration that separates the thoracic cavity from the abdominal cavity.
Contraction of the diaphragm increases the volume of the thoracic cavity, creating a vacuum that draws air into the lungs.
3. Intercostal Muscles:
Located between the ribs, these muscles assist in expanding and contracting the chest cavity during breathing.
Functioning of the Respiratory System
The process of breathing (ventilation) involves two main phases: inhalation and exhalation.
During inhalation, the diaphragm and intercostal muscles contract, expanding the chest cavity and decreasing internal air pressure, so air flows into the lungs.
During exhalation, these muscles relax, the chest cavity contracts, and air is expelled from the lungs.