الجيوب الأنفية والتنفّس

Respiratory System

• The respiratory system is vital for metabolic processes and energy release within the body's cells.
• Oxygen is essential for these processes, and carbon dioxide must be expelled.
• Respiration is divided into two types:
  • External respiration: This occurs in the lungs and involves the exchange of gases between inhaled air and blood. Blood releases carbon dioxide into the alveoli and absorbs oxygen.
  • Internal respiration: This is the exchange of gases between cells and blood. Cells take up oxygen dissolved in the blood and release carbon dioxide.

Secondary Functions of the Respiratory System

• Voice Production: Sound production begins in the larynx (voice box). Vocal cords vibrate during speech as exhaled air passes through them. Other structures like the pharynx and nasal cavity help refine the sound.
• Body Temperature Regulation: The nasal mucosa, rich with blood vessels, helps regulate body temperature.
• pH Regulation: The respiratory system regulates blood pH by controlling the amount of carbon dioxide in the blood.
  • If the blood becomes too acidic (due to increased CO2), the respiratory system increases breathing rate to remove more CO2 and reduce acidity.
  • Conversely, if the blood becomes too alkaline, the respiratory system slows breathing, increasing CO2 levels and returning the blood to a neutral pH.
• Olfaction (Sense of Smell): Olfactory receptors in the upper nasal passages detect odors.

Structure of the Respiratory System

• Upper Respiratory Tract: Includes the nose, pharynx, larynx, and trachea.
  • Nose: The first part of the respiratory system, with nostrils.
  • Nasal Passages: Located between the nostrils and pharynx; divided into right and left sides by a nasal septum. These are convoluted tubes.
  • Paranasal Sinuses: Air spaces in the skull bones, lined with cilia that help move mucus. Examples are maxillary and frontal sinuses.
  • Pharynx: The passageway for both the digestive and respiratory systems; has a posterior (respiratory) and an anterior (digestive) part. Reflexes regulate the passage of air and food.
• Lower Respiratory Tract: From the trachea to the alveoli, including the bronchi, bronchioles, and alveoli.
  • Trachea (Windpipe): A tube extending from the larynx into the chest cavity where it branches into two bronchi. It contains incomplete rings of cartilage for support, smooth muscle, and a lining of cilia that trap and remove foreign particles.
  • Bronchi: The branching of the trachea into two branches into each lung.
  • Bronchioles: Smaller branches of the bronchi within the lungs.
  • Alveoli: Tiny, thin-walled air sacs in the lungs, richly supplied with blood capillaries, allowing for efficient gas exchange.
• Lungs: Located within the thoracic cavity; each lung has a base and an apex.
• Thorax: Bone structure that encloses and protects the lungs. The diaphragm separates the thoracic and abdominal cavities and plays a key role in breathing.

Breathing

• Inhalation: The process of bringing air into the lungs. This involves increasing the size of the thoracic cavity by contraction of the diaphragm and intercostal muscles.
• Exhalation: The process of expelling air from the lungs. The thoracic cavity decreases in size as the diaphragm and intercostal muscles relax.

Gas Exchange in Alveoli

• Air in the alveoli has a high concentration of oxygen (21%) and a low concentration of carbon dioxide (0.03%).
• Oxygen moves from the alveoli to the blood capillaries, and carbon dioxide moves from the blood capillaries to the alveoli. This is governed by diffusion.

Control of Breathing

• Breathing is regulated by the respiratory center in the medulla oblongata of the brainstem.
• Mechanical Control: Receptors in the lungs respond to lung inflation and deflation, sending signals to the respiratory center to adjust breathing.
• Chemical Control: Chemical sensors in the carotid and aortic arteries monitor blood pH, carbon dioxide (CO2) levels, and oxygen (O2) levels send signals to control breathing.

Respiratory Infections

• Upper Respiratory Infections (URIs): Mostly viral, common types include rhinoviruses, parainfluenza viruses, respiratory syncytial virus (RSV), and adenoviruses.
• Influenza: A viral infection affecting the upper or lower respiratory tract. Type A is most common and serious.
• Lower Respiratory Infections: Protecting the lower respiratory system often involves effective defense mechanisms against infectious agents. Smoking damages these processes.
• Pneumonia: Inflammation of the lung tissue (alveoli/interstitium). Can be bacterial, viral or fungal.

Other Respiratory Conditions

• COPD (Chronic Obstructive Pulmonary Disease): Chronic obstructive disease of the airways, often caused by smoking. Symptoms can include chronic cough, mucus production, shortness of breath and hypoxia.
• Asthma: A chronic inflammatory condition of the airways. Asthma attacks can be triggered by various irritants producing bronchial spasms and inflammation.
• Emphysema: A lung condition characterized by the destruction of alveoli, leading to reduced lung elasticity and gas exchange. Often caused by smoking. Symptoms include shortness of breath.
• Cystic Fibrosis: A genetic disorder affecting exocrine glands, including the mucus-producing glands in the lungs, causing thick, sticky mucus. This can lead to respiratory infections, and digestive issues.