Anatomy and Physiology

Pulmonary Anatomy and Physiology

Entranc Vena Azy Branch Monary

  • Pulmonary structure includes left ventricle, left atrium, and great vessels.

Thoracic Cage Anatomy

  • Components of the thoracic cage include:

    • Manubrium

    • True Ribs (1-7): Attached directly to the sternum.

    • Body Sternum

    • Costal Cartilage: Allows flexibility.

    • Vertebrochondral Ribs (8-10): False ribs that connect to the seventh rib.

    • Floating Ribs (11-12): Not attached to the sternum.

Lung Anatomy

Lung Pleurae

  • Pleurae: Two thin layers that cover the lungs.

    • Parietal Pleura: Lines the thoracic cavity.

    • Visceral Pleura: Covers the lungs’ external surface.

    • Pleural Cavity: Potential space between the pleurae filled with pleural fluid to reduce friction.

Lung Lobes

  • Right Lung:

    • Superior (RSL)

    • Middle (RML)

    • Inferior (RIL)

  • Left Lung:

    • Superior (LSL)

    • Inferior (LIL)

Hilum and Structures

  • Hilum: Connects lungs to supporting structures; entry/exit for:

    • Main Bronchus

    • Pulmonary Arteries

    • Pulmonary Veins

    • Pulmonary Ligament: Attaches lung to mediastinum.

Lung Segments

  • Right Lung Segments:

    • Upper Lobe: Apical, Posterior, Anterior

    • Middle Lobe: Lateral, Medial

    • Lower Lobe: Superior, Medial Basal, Anterior Basal, Lateral Basal, Posterior Basal

  • Left Lung Segments:

    • Similar structure to the right but includes Lingula.

Ventilation and Gas Exchange

Lung Functions

  • Ventilation: Mechanical process of moving air in and out.

  • Respiration: Gas exchange at alveolar level.

  • Parenchyma: The functional part of the lungs.

Control of Breathing

  • Respiratory Center: Group of neurons controls rate and depth of breathing; includes:

    • Medullary Rhythmicity Center

    • Dorsal Respiratory Group (DRG): Basic rhythm of breathing.

    • Ventral Respiratory Group (VRG): More forceful breathing.

    • Pneumotaxic Area: Regulates breathing rate.

Factors Influencing Breathing

  • Chemicals: Influence rate based on O2 and CO2 levels.

  • Reflexes: Prevent over-inflation and respond to irritants.

  • Voluntary Respiration: Controlled by the cerebral cortex.

Alveolar Gas Exchange

Structure of Alveoli

  • Form the primary site for gas exchange; around 300 million in each lung.

  • Respiratory Membrane: Comprised of alveolar and capillary epithelial cells.

Gas Transport Mechanisms

  • Oxygen: Primarily carried by hemoglobin; becomes oxyhemoglobin.

  • Carbon Dioxide: Carried as bicarbonate ions (most of CO2); also binds to hemoglobin.

Ventilation-Perfusion (V/Q) Matching

  • V/Q Ratio: Ideal is 1; ranges from 0.6 to 3 depending on lung regions.

  • Dead Space: V > Q; wasted ventilation.

  • Shunt: V < Q; inadequate ventilation.

  • Conditions affecting V/Q ratio:

    • Decreased V/Q in pneumonia or lung disease.

    • Increased V/Q in pulmonary embolism.

Lung Volumes and Capacities

  • Volumes: Tidal Volume, Inspiratory Reserve Volume, Expiratory Reserve Volume, Residual Volume.

  • Capacities: Total Lung Capacity, Vital Capacity, Inspiratory Capacity, Functional Residual Capacity.

Pulmonary Anatomy and Physiology

Pulmonary Structure

  • Components: The pulmonary structure comprises the left ventricle, left atrium, and the network of great vessels such as the aorta and pulmonary arteries that transport blood to and from the lungs for oxygenation.

Thoracic Cage Anatomy

  • Components of the Thoracic Cage: The thoracic cage serves as a protective structure for the heart and lungs and includes:

    • Manubrium: The uppermost segment of the sternum, connects to the first rib and provides attachment for certain muscles.

    • True Ribs (1-7): Ribs that are directly attached to the sternum through costal cartilage, providing stability and flexibility in breathing.

    • Body of the Sternum: The elongated central part of the sternum, which connects with the true ribs.

    • Costal Cartilage: Connective tissue that provides flexibility and allows for the movement necessary during respiration.

    • Vertebrochondral Ribs (8-10): Also known as false ribs; these ribs are attached indirectly to the sternum through the costal cartilage of the seventh rib.

    • Floating Ribs (11-12): Ribs that do not attach to the sternum and serve mainly to protect the kidneys.

Lung Anatomy

  • Lung Pleurae: The lungs are encapsulated in two pleural membranes:

    • Parietal Pleura: This outer layer lines the chest wall and diaphragm, providing lubrication and reducing friction during respiratory movements.

    • Visceral Pleura: This inner layer closely adheres to the lung surface, facilitating smooth expansion and contraction of the lungs during breathing.

    • Pleural Cavity: The potential space between the pleurae contains pleural fluid, which further reduces friction and assists in lung expansion.

  • Lung Lobes:

    • Right Lung: Comprised of three lobes:

      • Superior Lobe (RSL)

      • Middle Lobe (RML)

      • Inferior Lobe (RIL)

    • Left Lung: Comprised of two lobes:

      • Superior Lobe (LSL)

      • Inferior Lobe (LIL) which includes an anatomical feature called the lingula.

  • Hilum and Structures: The hilum is the key area where the lungs connect to the mediastinum, serving as the entry/exit point for:

    • Main Bronchus: Divides into the left and right bronchi to supply air to each lung.

    • Pulmonary Arteries: Carry deoxygenated blood from the right ventricle to be oxygenated in the lungs.

    • Pulmonary Veins: Return oxygenated blood from the lungs to the left atrium of the heart.

    • Pulmonary Ligament: A connective structure that anchors the lungs to the mediastinum.

  • Lung Segments:

    • Right Lung Segments:

      • Upper Lobe: Apical, Posterior, Anterior segments.

      • Middle Lobe: Lateral, Medial segments.

      • Lower Lobe: Superior, Medial Basal, Anterior Basal, Lateral Basal, Posterior Basal segments.

    • Left Lung Segments: Similar to the right but includes the Lingula, a tongue-like projection associated with the superior lobe.

Ventilation and Gas Exchange

  • Lung Functions:

    • Ventilation: The mechanical process of moving air into and out of the lungs, which involves inhalation and exhalation.

    • Respiration: The biochemical exchange of gases at the alveolar level, where oxygen is absorbed into the blood, and carbon dioxide is expelled.

    • Parenchyma: The functional tissue of the lungs that comprises alveoli and respiratory bronchioles, crucial for effective gas exchange.

  • Control of Breathing:

    • Respiratory Center: A group of interconnected neurons in the brainstem that regulate the rate and depth of breathing. It includes:

      • Medullary Rhythmicity Center: Contains neurons that set the rhythm of breathing.

      • Dorsal Respiratory Group (DRG): Responsible for the basic rhythm of breathing.

      • Ventral Respiratory Group (VRG): Activates during forceful breathing (exercise, exertion).

      • Pneumotaxic Area: Involved in fine-tuning the rhythm and rate of breathing.

  • Factors Influencing Breathing:

    • Chemicals: Levels of oxygen (O2) and carbon dioxide (CO2) significantly influence the breathing rate via chemoreceptors.

    • Reflexes: Protective reflexes exist to prevent over-inflation of the lungs and to respond to airway irritants like smoke or allergens.

    • Voluntary Respiration: Controlled by the cerebral cortex for deliberate actions like speech or singing.

  • Alveolar Gas Exchange:

    • Structure of Alveoli: These tiny air sacs provide the primary site for gas exchange; there are approximately 300 million alveoli in each lung, maximizing surface area.

    • Respiratory Membrane: Made up of the alveolar and capillary epithelial cells, where diffusion of gases occurs.

  • Gas Transport Mechanisms:

    • Oxygen: Carried mainly by hemoglobin, forming Oxyhemoglobin as it binds to red blood cells in the pulmonary capillaries.

    • Carbon Dioxide: Transported as bicarbonate ions (HCO3-) in plasma; also binds to hemoglobin forming carbaminohemoglobin.

  • Ventilation-Perfusion (V/Q) Matching:

    • V/Q Ratio: Ideal ratio is 1; variations affect gas exchange efficiency:

      • Dead Space (V > Q): Implies wasted ventilation due to non-perfused alveoli.

      • Shunt (V < Q): Indicates areas with inadequate ventilation.

    • Conditions affecting V/Q ratio:

      • Decreased V/Q often occurs in lung diseases like pneumonia.

      • Increased V/Q may occur in cases like pulmonary embolism.

Lung Volumes and Capacities

  • Volumes:

    • Tidal Volume: The volume of air inhaled or exhaled during normal breathing.

    • Inspiratory Reserve Volume: Additional air that can be inhaled with a deep breath; the amount over tidal volume.

    • Expiratory Reserve Volume: The additional air that can be forcibly exhaled after a normal exhalation.

    • Residual Volume: The volume of air that remains in the lungs after forcible expiration, preventing lung collapse.

  • Capacities:

    • Total Lung Capacity: The total volume of air in the lungs after maximum inhalation.

    • Vital Capacity: The maximum volume of air that can be expelled after full inhalation.

    • Inspiratory Capacity: Maximum volume of air that can be inhaled after normal exhalation.

    • Functional Residual Capacity: The volume of air remaining in the lungs after normal exhalation; includes both expiratory reserve volume and residual volume.