Respiratory System Notes

Respiratory System

  • Designed as an air distributor and gas exchanger.
  • Ensures oxygen supply and carbon dioxide removal.
  • Maintains constant environment for cell function.
  • Filters, warms, and humidifies air.

Structural Plan

  • Organs: nose, pharynx, larynx, trachea, bronchi, and lungs.
  • Structure: tube with branches ending in alveoli (tiny, thin-walled sacs).
  • Function: distribute air for gas exchange between air and blood.
  • Gas exchange occurs via diffusion.

Respiratory Tracts

  • Upper: outside thorax; includes nose, pharynx, and larynx.
  • Lower: within thorax; includes trachea, bronchial tree, and lungs.

Respiratory Mucosa

  • Lines air distribution tubes.
  • Produces >125 mL mucus daily, forming a "mucus blanket".
  • Mucus traps irritants.
  • Cilia move mucus upward to pharynx.

Nose Structure

  • Nasal septum divides nose into cavities.
  • Lined with mucous membrane.
  • Nasal polyp: noncancerous growths obstructing nasal passage.

Sinusitis

  • Sinuses: frontal, maxillary, sphenoidal, ethmoidal.
  • Paranasal sinuses produce mucus.
  • Sinusitis: sinus infection from colds, causing pressure, pain, headache, redness.
  • Treatment: decongestants, antibiotics, surgery.

Nose Functions

  • Warms and moistens inhaled air.
  • Sense organs for smell.

Pharynx (Throat) Structure

  • Length: ~12.5 cm (5 inches).
  • Divisions: nasopharynx, oropharynx, laryngopharynx.
  • Openings: nasal cavities, mouth, esophagus, larynx, auditory tubes.

Pharynx Function

  • Passage for food, liquids, and air.
  • Tonsils provide immune protection; tonsillitis is inflammation of tonsils.

Larynx Structure

  • Below pharynx (voice box).
  • Framework of cartilage (thyroid cartilage/Adam’s apple is largest).
  • Epiglottis covers opening.
  • Mucous lining.
  • Vocal cords stretch across larynx; glottis is space between cords.

Larynx Functions

  • Air distribution to lungs.
  • Voice production via vocal cords.

Disorders of the Upper Respiratory Tract

  • Upper respiratory infection (URI).
  • Rhinitis: nasal inflammation (cold, flu, allergy).
    • Infectious rhinitis: common cold
    • Allergic rhinitis: hay fever
  • Pharyngitis: sore throat.
  • Laryngitis: larynx inflammation.
  • Croup: laryngitis caused by parainfluenza virus (bark-like cough).
  • Deviated septum: abnormal septum position causing blockage.
  • Epistaxis: bloody nose from injury, hypertension.

Trachea Structure

  • Tube (~11 cm or 4½ inches) from larynx to thoracic cavity.
  • Mucous lining.
  • C-shaped cartilage rings.
  • Function: air passage to and from lungs.

Trachea

  • Obstruction: choking, causing death in minutes.
  • Abdominal thrust maneuver (Heimlich) clears obstructions.
  • Tracheostomy: surgical insertion of tube for blocked airway.

Bronchi, Bronchioles, and Alveoli Structure

  • Trachea branches into bronchi (right bronchus more vertical).
  • Aspirated objects lodge in right bronchus/lung.
  • Bronchi branch into smaller bronchioles.
  • Bronchioles end in alveolar sacs with alveoli.

Bronchi, Bronchioles, and Alveoli Functions

  • Bronchi/bronchioles: air distribution.
  • Alveoli: gas exchange between air and blood.
  • Alveolar ducts: tiny tubes that form from the subdivision of bronchioles, which end in clusters of alveoli called alveolar sacs

Bronchi, Bronchioles, and Alveoli

  • Pulmonary Surfactant: Reduces surface tension in alveoli
  • During expiration, when alveoli become smaller, surfactant becomes more concentrated, further reducing surface tension and preventing alveolar collapse.
  • Respiratory distress: inability to inflate alveoli.
    • Infant respiratory distress syndrome (IRDS): lack of surfactant in premature infants.
    • Adult respiratory distress syndrome (ARDS): surfactant impairment by foreign substances.

Lungs and Pleura Structure

  • Size: fill chest cavity (except space for heart).
  • Apex: upper part under collarbone.
  • Base: lower part on diaphragm.
  • Pleura: membrane lining chest cavity and lungs, reducing friction.
  • Right lung has three lobes; left lung has two lobes.

Lungs and Pleura Function

  • Breathing (pulmonary ventilation).
  • Pleurisy: inflammation of pleura.
  • Atelectasis: collapsed lung.
    • Pneumothorax: air in pleural space.
    • Hemothorax: blood in pleural space.

Respiration

  • Mechanics: inspiration (air in) and expiration (air out).
  • Thorax size changes affect air pressure.
  • Air moves from high to low pressure.

Respiration - Inspiration

  • Active process: muscles increase thorax volume, decreasing lung pressure.
  • Inspiratory muscles: diaphragm and external intercostals.
  • Diaphragm flattens (increases thorax length).
  • External intercostals elevate ribs (increase thorax size).

Respiration - Expiration

  • Thoracic Cavity decreases in size and increases in pressure.
  • Passive process normally (quiet expiration).
  • Thorax returns to resting size and elastic recoil.
  • Internal intercostals/abdominal muscles used in forceful expiration.
  • Internal intercostals depress rib cage.
  • Abdominal muscles elevate diaphragm.

Regulation of Respiration

  • Cerebral cortex: limited voluntary control.
  • Receptors:
    • Chemoreceptors: respond to carbon dioxide, oxygen, and blood acid levels in carotid and aortic bodies.
    • Pulmonary stretch receptors: prevent overinflation.

Types of Breathing

  • Eupnea: normal breathing.
  • Hyperventilation: rapid, deep respirations.
  • Hypoventilation: slow, shallow respirations.
  • Dyspnea: labored breathing.
  • Orthopnea: dyspnea relieved by sitting upright.
  • Apnea: stopped respiration.
  • Respiratory arrest: failure to resume breathing after apnea.

Disorders of the Lower Respiratory Tract

  • Lower respiratory infection.
  • Acute bronchitis/tracheobronchitis: inflammation of bronchi/trachea from URI.
  • Pneumonia: lung inflammation with exudates.
    • Lobar pneumonia: affects entire lobe.
    • Bronchopneumonia: scattered infection along bronchial tree.
  • Tuberculosis (TB): chronic, contagious lung infection.

Disorders of the Lower Respiratory Tract

  • Restrictive pulmonary disorders: reduce lung tissue stretch.
    • Factors inside the lungs: fibrosis or inflammation.
    • Factors outside the lungs: pain from injury or pleurisy.
  • Obstructive pulmonary disorders: obstruct breathing.
    • Chronic obstructive pulmonary disease (COPD) from preexisting conditions.
    • Chronic bronchitis: bronchial tree inflammation.
    • Emphysema: reduced lung surface area from alveolar damage.
    • Asthma: recurring airway spasms, edema, and mucus production.
  • Lung cancer: malignant tumor, treatable with surgery, chemotherapy, radiation, and photodynamic therapy.