Anatomy of the Respiratory System

Major Structures:
- Nasal Cavity: Filters, warms, and humidifies air.
- Pharynx: Pathway for air to the larynx; connects nasal and oral cavities.
- Larynx: Voice box; contains vocal cords and protects airway.
- Trachea: Windpipe; conducts air to bronchi, supported by cartilage rings.
- Bronchi: Main passages that branch from the trachea into each lung.
- Bronchioles: Smaller air passages within the lungs leading to alveoli.
- Alveoli: Tiny air sacs where gas exchange occurs; surrounded by capillaries.
Lungs:
- Composed of lobes (3 in the right lung, 2 in the left lung).
- Pleura: Double-layered membrane surrounding lungs, facilitating movement during breathing.

Inhalation:
- Diaphragm contracts and moves downward.
- Intercostal muscles expand rib cage.
- Thoracic cavity volume increases, causing pressure drop; air flows in.
Exhalation:
- Diaphragm relaxes and moves upward.
- Intercostal muscles contract, decreasing rib cage size.
- Thoracic cavity volume decreases, causing pressure increase; air flows out.
Types of Breathing:
- Quiet Breathing: Passive exhalation; minimal muscle effort.
- Forced Breathing: Involves additional muscles (e.g., abdominal muscles) for exhalation.

Asthma: Chronic inflammation of airways; causes wheezing, shortness of breath.
Chronic Obstructive Pulmonary Disease (COPD): Includes emphysema and chronic bronchitis; leads to airflow limitation.
Pneumonia: Infection causing inflammation in air sacs; may fill with fluid.
Tuberculosis (TB): Bacterial infection primarily affecting lungs; causes cough and chest pain.
Lung Cancer: Uncontrolled growth of cells in lungs; risk factors include smoking and exposure to carcinogens.

Muscle: Primary muscle of respiration; dome-shaped, located at the base of the thoracic cavity.
Function:
- Contracts during inhalation, increasing thoracic volume.
- Relaxes during exhalation, assisting in expelling air from lungs.
Importance: Critical for efficient breathing; dysfunction can lead to respiratory insufficiency.

Location: Occurs in the alveoli of the lungs.
Mechanism:
- Diffusion: Oxygen moves from alveoli to blood; carbon dioxide moves from blood to alveoli.
- Driven by concentration gradients (high to low concentration).
Oxygen Transport:
- Bound to hemoglobin in red blood cells; a small amount dissolves in plasma.
Carbon Dioxide Transport:
- Transported as bicarbonate ions in plasma; some bound to hemoglobin; a small amount dissolved in plasma.
Importance: Essential for cellular respiration and maintaining acid-base balance in the body.

Nasal Cavity: Plays a crucial role in filtering, warming, and humidifying inhaled air.
Pharynx: Acts as a passageway for air to reach the larynx; connects both nasal and oral cavities.
Larynx: Known as the voice box, it houses the vocal cords and provides protection for the airway.
Trachea: Also known as the windpipe, it channels air to the bronchi and is reinforced by cartilage rings for structural support.
Bronchi: Main air passages diverging from the trachea into the lungs, ensuring efficient airflow.
Bronchioles: Smaller tubular air passages in the lungs that branch from bronchi and lead to alveoli.
Alveoli: Microscopic air sacs where oxygen and carbon dioxide exchange occurs, surrounded by a network of capillaries.
Lungs: Comprised of lobes, with 3 lobes in the right lung and 2 in the left, facilitating gas exchange.
Pleura: A double-layered membrane enveloping the lungs, enabling smooth movement during inhalation and exhalation.

Inhalation: Initiated by the diaphragm contracting and moving down, while intercostal muscles expand the rib cage; this increase in thoracic cavity volume lowers internal pressure, drawing air in.
Exhalation: Involves diaphragm relaxing and moving back upward; intercostal muscles contract, reducing rib cage size and thoracic cavity volume, which raises pressure and pushes air out.
Types of Breathing:
- Quiet Breathing: Characterized by passive exhalation requiring minimal muscular effort.
- Forced Breathing: Engages additional muscles, such as abdominal muscles, to enhance exhalation force.

Asthma: Characterized by chronic airway inflammation, resulting in wheezing and difficulty breathing.
Chronic Obstructive Pulmonary Disease (COPD): Encompasses conditions like emphysema and chronic bronchitis, leading to limited airflow and respiratory distress.
Pneumonia: Infectious condition causing inflammation in the alveoli, potentially resulting in fluid accumulation.
Tuberculosis (TB): A contagious bacterial infection primarily impacting lung health, leading to persistent cough and chest pain.
Lung Cancer: Involves unchecked cellular growth in the lungs; major risk factors include tobacco use and carcinogen exposure.

Muscle: The primary muscle responsible for respiration, dome-shaped, located at the base of the thoracic cavity.
Function: Contracts during inhalation to expand thoracic volume and relaxes during exhalation, aiding in expelling air from the lungs.
Importance: Essential for effective breathing; dysfunction can jeopardize respiratory efficiency and overall oxygen supply.

Location: Gas exchange transpires within the alveoli of the lungs.
Mechanism:
- Diffusion is the primary process, where oxygen shifts from alveoli to blood, while carbon dioxide moves from blood back to alveoli, influenced by concentration gradients.
Oxygen Transport: Predominantly binds to hemoglobin within red blood cells; a minor portion remains dissolved in plasma.
Carbon Dioxide Transport: Mostly carried as bicarbonate ions in blood plasma, some is combined with hemoglobin, and a small fraction dissolves in plasma.
Importance: Critical for supplying oxygen for cellular respiration and maintaining the body's acid-base equilibrium.