Anatomy of the Respiratory System

Upper Respiratory Tract:
- Nose/Nasal Cavity: Filters, warms, and humidifies air.
- Pharynx: Passageway for air and food.
- Larynx: Contains vocal cords; protects the trachea against food aspiration.
Lower Respiratory Tract:
- Trachea: Windpipe; conducts air to the bronchi.
- Bronchi: Right and left branches that lead to the lungs.
- Bronchioles: Smaller air passages that lead to alveoli.
- Alveoli: Tiny air sacs where gas exchange occurs; surrounded by capillaries.
Lungs:
- Right Lung: Three lobes (superior, middle, inferior).
- Left Lung: Two lobes (superior, inferior); has cardiac notch for heart.
Pleura: Double-layered membrane surrounding each lung; pleural cavity contains pleural fluid which reduces friction.

Spirometry: Measures air flow in and out of lungs; key parameters include:
- FVC (Forced Vital Capacity)
- FEV1 (Forced Expiratory Volume in 1 second)
- FEV1/FVC ratio: Indicates obstructive or restrictive lung disease.
Lung Volumes:
- Tidal Volume (TV): Volume of air breathed in and out during normal respiration.
- Inspiratory Reserve Volume (IRV): Extra air inhaled past tidal volume.
- Expiratory Reserve Volume (ERV): Extra air exhaled past tidal volume.
- Residual Volume (RV): Air remaining in lungs after maximum exhalation.
Diffusion Capacity: Assesses the lungs' ability to transfer gas from alveoli to blood.

Obstructive Diseases:
- Asthma: Inflammation and narrowing of airways; characterized by wheezing, shortness of breath.
- Chronic Obstructive Pulmonary Disease (COPD): Includes emphysema and chronic bronchitis; limited airflow and breathing difficulty.
Restrictive Diseases:
- Pulmonary Fibrosis: Scarring of lung tissue leading to reduced capacity.
- Interstitial Lung Disease: Group of disorders affecting the tissue and space around the air sacs.
Infectious Diseases:
- Pneumonia: Infection that inflates air sacs in one or both lungs.
- Tuberculosis: Bacterial infection that primarily affects the lungs.
Other Conditions:
- Allergic reactions: Can lead to inflammation and bronchoconstriction.
- Lung cancer: Uncontrolled cell growth in lung tissue.

Location: Occurs in alveoli, surrounded by capillary networks.
Mechanism:
- O2 from alveoli diffuses into blood.
- CO2 from blood diffuses into alveoli.
Factors Affecting Gas Exchange:
- Partial pressure differences (Dalton's Law).
- Surface area available for diffusion (emphysema decreases surface area).
- Thickness of the alveolar-capillary membrane (increased in pulmonary fibrosis).

Inspiration:
- Diaphragm contracts, increasing thoracic cavity volume.
- External intercostal muscles contract, raising rib cage.
- Pressure inside lungs decreases, drawing air in.
Expiration:
- Diaphragm relaxes, decreasing thoracic cavity volume.
- Internal intercostal muscles contract, forcing air out.
- Can be passive (during rest) or active (during exercise).
Breathing Patterns:
- Eupnea: Normal breathing.
- Tachypnea: Rapid breathing; often due to anxiety or exertion.
- Bradypnea: Slow breathing; can indicate issues (e.g., brain injury).
- Apnea: Temporary cessation of breathing.

Trachea: Windpipe leading to the bronchi
Bronchi: Right and left branches that lead to the lungs.
Bronchioles: Smaller air passages that lead to alveoli.
Alveoli: Tiny air sacs where gas exchange occurs, surrounded by capillaries.

Right Lung: Has three lobes.
Left Lung: Has two lobes and a cardiac notch for the heart.
Pleura: Double-layered membrane surrounding each lung, containing pleural fluid to reduce friction.

Measures airflow in and out of the lungs.
Key Parameters:
- FVC (Forced Vital Capacity)
- FEV1 (Forced Expiratory Volume in 1 second)
- FEV1/FVC ratio: Identifies obstructive or restrictive lung problems.

Tidal Volume (TV): Volume of air breathed in and out during normal respiration.
Inspiratory Reserve Volume (IRV): Extra air inhaled past tidal volume.
Expiratory Reserve Volume (ERV): Extra air exhaled past tidal volume.
Residual Volume (RV): Air remaining in lungs after maximum exhalation.

Asthma: Inflamed and narrowed airways causing wheezing and shortness of breath.
Chronic Obstructive Pulmonary Disease (COPD): Emphysema and chronic bronchitis, limiting airflow and causing breathing difficulty.

Pulmonary Fibrosis: Scarring of lung tissue leading to reduced capacity.
Interstitial Lung Disease: Disorders affecting the tissue and space around the air sacs.

Location: Occurs in alveoli, surrounded by capillary networks.
Mechanism: Oxygen diffuses from alveoli into blood, and carbon dioxide diffuses from blood into alveoli.
Factors Affecting Gas Exchange:
- Partial pressure differences (Dalton's Law).
- Surface area available for diffusion (decreased in emphysema).
- Thickness of the alveolar-capillary membrane (increased in pulmonary fibrosis).

Inspiration:
- Diaphragm contracts, expanding the thoracic cavity.
- External intercostal muscles contract, raising the rib cage.
- Pressure inside the lungs decreases, drawing air in.
Expiration:
- Diaphragm relaxes, decreasing thoracic cavity volume.
- Internal intercostal muscles contract, forcing air out.
- Expiration can be passive (during rest) or active (during exercise).

Eupnea: Normal breathing.
Tachypnea: Rapid breathing, often due to anxiety or exertion.
Bradypnea: Slow breathing, potentially indicating problems like brain injury.
Apnea: Temporary cessation of breathing.