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.