Sistema respiratorio: panoramica generale

General Overview

• The respiratory system is responsible for gas exchange: taking in oxygen (O2) and releasing carbon dioxide (CO2).
• It consists of a network of structures that facilitate this process, including the nose, pharynx, larynx, trachea, bronchi, and lungs.
• The lungs contain millions of alveoli specialized for gas exchange.
• The process of respiration involves both inhalation (breathing in) and exhalation (breathing out).

Upper Respiratory Tract

• The upper respiratory tract includes the nose, nasal cavity, pharynx, and larynx.
• The nose warms, humidifies, and filters inhaled air.
• The nasal cavity contains olfactory receptors for smell.
• The pharynx (throat) is a passageway for both air and food.
• The larynx (voice box) houses the vocal cords and plays a crucial role in sound production.

Lower Respiratory Tract

• The lower respiratory tract includes the trachea, bronchi, and lungs.
• The trachea (windpipe) is a tube that carries air to the bronchi.
• The bronchi are two branches that divide further into smaller bronchioles within the lungs.
• The lungs are the primary organs of gas exchange, composed of millions of alveoli.
• Alveoli are tiny air sacs surrounded by a network of capillaries where gas exchange takes place.

Mechanics of Breathing

• Breathing is a mechanical process driven by changes in pressure within the thoracic cavity (chest cavity).
• Inhalation occurs when the diaphragm contracts and the rib cage expands, creating a lower pressure inside the lungs, drawing air in.
• Exhalation occurs when the diaphragm relaxes and the rib cage recoils, increasing pressure in the lungs and forcing air out.
• Breathing is regulated by the respiratory center in the brain, which responds to changes in blood chemistry (e.g., CO2 levels).

Gas Exchange

• Gas exchange in the alveoli relies on diffusion.
• Oxygen from the inhaled air diffuses across the alveolar membrane and into the bloodstream.
• Carbon dioxide from the blood diffuses into the alveoli and is expelled during exhalation.
• The process is facilitated by the high surface area of the alveoli and the thin nature of the alveolar membrane.

Respiratory Volumes and Capacities

• Respiratory volumes and capacities describe the quantity of air exchanged during breathing.
• Tidal volume is the volume of air inhaled or exhaled in a normal breath.
• Inspiratory reserve volume is the additional volume of air that can be inhaled forcibly.
• Expiratory reserve volume is the additional volume of air that can be exhaled forcibly.
• Residual volume is the amount of air remaining in the lungs after forceful exhalation.
• Vital capacity is the maximum amount of air that can be moved in and out of the lungs in a single breath.

Control of Respiration

• Breathing is largely involuntary and controlled by the respiratory center in the medulla oblongata of the brain, and in the pons also.
• Chemoreceptors in the brain and blood vessels monitor blood levels of oxygen, carbon dioxide, and pH.
• These chemoreceptors trigger adjustments in breathing rate and depth to maintain homeostasis.
• External factors like exercise, emotions, and altitude also influence respiration.

Diseases Affecting the Respiratory System

• Various diseases can affect the respiratory system, including infections (e.g., pneumonia, bronchitis), allergies (e.g., asthma), and chronic conditions (e.g., emphysema, chronic bronchitis).
• These conditions can impair gas exchange, causing breathing difficulties and health issues.
• Lifestyle choices such as smoking significantly increase the risk of respiratory diseases.