RGI 1

Pressures Around the Lungs

  • The pressures surrounding the lungs play a crucial role in the process of respiration.

  • These pressures are essential for the effective transfer of air in and out of the lungs.

Functions of Oxygen in Respiration

  • Oxygen acts as the terminal electron acceptor in cellular respiration.

  • After electrons travel down the electron transport chain, oxygen accepts them, enabling ATP production.

  • Without oxygen, the electron transport process halts, leading to reduced ATP generation.

Components of Respiration

External Respiration

  • Involves the transfer of oxygen from the atmosphere to body tissues.

  • Gas transport occurs primarily within the blood.

Internal Respiration

  • Refers to the exchange of gases across capillary membranes where oxygen enters and carbon dioxide is expelled from tissues.

Anatomy of the Upper Respiratory Tract

  • Nasal Cavity: Space behind the nose, connects to the pharynx.

  • Pharynx: Space at the back of the nose and mouth, consisting of the nasal and oral pharynx.

  • Larynx: Also known as the voice box, located below the pharynx.

Anatomy of the Lower Respiratory Tract

  • Trachea: The windpipe that splits into primary bronchi.

  • Primary Bronchi: Two main branches (left and right) leading to each lung.

  • Secondary Bronchi: Further divides into lobar bronchi serving individual lung lobes.

  • Tertiary Bronchi: Provide segments within the lobes.

  • Bronchioles: Smaller branches leading to alveoli.

Eustachian Tubes

  • Link the middle ear to the nasopharynx to help equalize pressure.

Respiratory Infections

  • Upper Respiratory Tract Infections (URIs): Common and usually mild (e.g., colds).

    • Common Viruses: Rhinovirus and coronavirus.

  • Lower Respiratory Tract Infections (LRIs): More serious, can lead to conditions like bronchitis or pneumonia.

    • Causes: Influenza virus, Respiratory syncytial virus (RSV).

Alveolar Structure

  • Composed of two types of pneumocytes:

    • Type I Pneumocytes (95%): Involved in gas exchange.

    • Type II Pneumocytes (5%): Produce surfactant to maintain alveolar stability.

Thoracic Cavity Structure

  • Composed of the right lung (3 lobes) and left lung (2 lobes, cardiac notch for heart).

  • Pleurae: Membranes covering the lungs; important for creating negative pressure in the thoracic cavity which aids in airflow into the lungs.

Breathing Mechanism

Inspiration (Inhalation)

  • An active process requiring muscle contraction.

  • Diaphragm Contraction: Flattens the diaphragm, increasing thoracic space and decreasing lung pressure.

  • Intercostal Muscles: External muscles contract to elevate ribs, expanding thoracic cavity.

  • Air enters lungs due to lower pressure compared to atmosphere.

Expiration (Exhalation)

  • Primarily a passive process as muscles relax.

  • Elastic recoil of lungs pushes air out.

  • Forced Exhalation: Involves contraction of internal intercostal and abdominal muscles, especially during vigorous activities.

Pleural Pressures

  • Pleural space maintains negative pressure relative to atmospheric pressure, essential for lung inflation.

  • Infection in this space (pleurisy) can lead to complications.

Respiratory Distress Syndrome

  • Common in premature infants due to insufficient surfactant production.

  • Difficulty inflating alveoli leads to atelectasis (collapse of lung tissue) and respiratory distress.

  • Adequate surfactant is critical for keeping alveoli open for efficient gas exchange.