Respiratory System pt 1

Respiration Facts

  • The average person takes in 21,600 breaths per day.

  • People yawn because the brain detects low levels of oxygen in the lungs.

  • Hiccups are caused by spasms or sudden movements in the diaphragm.

  • When a human coughs, droplets can travel a distance of up to 3 feet.

  • A cold virus can live outside the body for up to 3 days.

  • The diaphragm is the biggest muscle in the respiratory system.

Primary Functions of the Respiratory System

  • Provides a means of gas exchange between the environment and the body.

  • Ventilation: mechanical process of moving air into and out of lungs.

  • Diffusion: O2 moves out of lungs into the blood, CO2 moves from blood into lungs.

  • Regulates acid-base balance during exercise.

Major Organs of the Respiratory System

  • Nose & Nasal Cavity: filters and warms air.

  • Pharynx: throat that connects to the esophagus.

  • Larynx: voice box that contains vocal cords.

  • Trachea: windpipe that directs air to the lungs.

  • Bronchial Tree & Alveoli: sites where air is exchanged.

Anatomy of the Respiratory System

Thoracic Cavity

  • Located above the diaphragm, houses the lungs and heart.

  • Protected by ribs, spine, sternum:

    • Intercostals: muscles between ribs.

    • Diaphragm: main muscle for breathing.

    • Scalene & Sternocleidomastoid: assist in holding neck, allowing efficient air flow.

Lungs

  • Enclosed by two thin membranes called the pleura (visceral & parietal).

  • Functions of pleura:

    • Support: tethers lungs to diaphragm and thoracic cavity.

    • Protection: pleural surfaces slide past one another to reduce friction.

  • Collapsing lung can occur if pleura are compromised.

Conducting and Respiratory Zones

Conducting Zone

  • Air passages that transport air and condition it:

    • Nose, mouth, pharynx, larynx, trachea, bronchial tree, terminal bronchioles.

    • Conditions air: warms, humidifies, cleans (via mucus and macrophages).

Respiratory Zone

  • Begins gas exchange in the lungs:

    • Respiratory bronchioles, alveolar ducts, alveolar sacs.

    • Conditions affecting airways: Emphysema, exercise-induced asthma.

Alveoli and Gas Exchange

  • Alveolus: site of gas exchange; small air sac at lung's passage end.

  • ~300 million alveoli provide a large surface area (equivalent to a tennis court).

  • Alveoli covered by capillary network: 620 miles of capillaries facilitate diffusion.

  • Thinner tissue allows faster diffusion of O2 and CO2.

Ventilation Mechanics

  • Continuous gas exchange between external environment and body.

  • Inhalation: oxygen-rich air taken into lungs.

  • Exhalation: CO2-rich air expelled from lungs.

  • External respiration: gas exchange between atmosphere and blood.

  • Internal respiration: gas exchange between blood and cells.

Mechanics of Inspiration/Expiration

  • Inspiration: diaphragm contracts, chest expands, reducing pressure in lungs.

  • Expiration: diaphragm relaxes, chest compresses, increasing pressure to push air out.

Lung Volumes and Capacities

Lung Volumes

  1. Tidal volume: air exchanged with each breath.

  2. Inspiratory reserve volume (IRV): max air inhaled after quiet inspiration.

  3. Expiratory reserve volume (ERV): max air exhaled after quiet expiration.

  4. Residual volume (RV): air remaining post forced expiration.

Lung Capacities

  1. Vital capacity (VC): max air expired after max inspiration.

  2. Inspiratory capacity (IC): max air inspired after normal expiration.

  3. Functional residual capacity (FRC): air left post quiet normal expiration.

  4. Total lung capacity (TLC): total air lung can hold.

Pulmonary Ventilation and Alveolar Ventilation

  • Pulmonary Ventilation (V): amount of air moved in/out of lungs per minute (~7.5 L/min).

  • Alveolar Ventilation (VA): fresh air reaching respiratory zone (~350 mL); Dead space ventilation (VD): unused air (~150 mL).

Gas Exchange Principles

Gas Diffusion

  • Partial Pressure: Individual pressure exerted by gas; total pressure is the sum of all partial pressures (Dalton’s Law).

  • Fick’s Law: Gas transfer rate depends on area, thickness, diffusion coefficient, and pressure difference.

O2 and CO2 Transport

  • O2 is transported by hemoglobin (99% bound).

  • CO2 is transported as dissolved gas, bound to hemoglobin, or as bicarbonate ion.

  • Myoglobin also binds O2 in muscles, providing reserve during exercise.

Acid-Base Balance

  • Normal blood pH: ~7.4; values outside 7.0 to 7.8 are critical: Alkalosis (pH > 7.4) and Acidosis (pH < 7.4).

  • Exercise can lower pH due to lactic acid buildup, impacting enzyme activity and cell integrity.