Respiration Overview

Respiration

• Respiration is the process of taking in oxygen and releasing carbon dioxide.
• Normal respiratory rates differ by age group:
  • Newborn: 30-60 breaths per minute
  • Early childhood: 20-40 breaths per minute
  • Late childhood: 15-25 breaths per minute
  • Adult: 12-16 breaths per minute
• Tachypnea: More than 16 breaths per minute
• Bradypnea: Less than 12 breaths per minute

Types of Respiration

• Respiration is categorized into two types:
  • External respiration: Exchange of gases between lungs and blood.
  • Internal respiration: Exchange of gases between blood and tissues.

Phases of Respiration

• Occurs in two phases:
  • Inspiration: Air enters the lungs from the atmosphere.
  • Expiration: Air leaves the lungs.

Anatomy of the Respiratory System

• Includes the upper and lower respiratory tract.
• Upper respiratory tract: Nasal cavity, pharynx, and larynx.
• Lower respiratory tract: Trachea, bronchi, bronchioles, and lungs.
• Key points about the nose: It's the first organ of the respiratory tract.
  • Larynx is also known as the voice box.
• Epiglottis: Flexible cartilage preventing food and drink from entering the windpipe
• Trachea consists of 16-20 C-shaped rings of hyaline cartilage.
• Carina: The point where the trachea divides into two bronchi.
  • Right bronchus/ is wider, shorter, and more vertical than Left bronchus leading to an increased chance of blockage.
• Alveoli: Smallest units of the respiratory tract, located in the lungs.
• Lungs contain roughly 300 million alveoli, providing a large gas exchange surface area (approximately 70 square meters)
  • Type 1 Alveolar Cells (95% of cells): Primarily involved in gas exchange.
  • Type 2 Alveolar Cells (5% of cells): Produce surfactant, reducing surface tension and preventing alveolar collapse during exhalation.
• Surfactant: Phospholipid that prevents alveolar collapse during expiration.

Lung Volumes and Capacities

• Static lung volumes: Volumes of air breathed by an individual.

  • Tidal volume (TV): Volume of air inhaled and exhaled in a normal breath (approximately 500 mL).
  • Inspiratory reserve volume (IRV): Maximum volume of air that can be inhaled after a normal breath (approximately 3,300 mL).
  • Expiratory reserve volume (ERV): Maximum volume of air that can be exhaled after a normal breath ( approximately 1,000 mL).
  • Residual volume (RV): Volume of air remaining in the lungs after a maximal exhalation (approximately 1,200 mL).

• Lung capacities: Combinations of two or more lung volumes.

  • Inspiratory capacity (IC)
  • Vital capacity (VC)
  • Functional residual capacity (FRC)
  • Total lung capacity (TLC)

• Surfactant production begins around weeks 24-28 of fetal life and is usually sufficient by week 35.

• Antrum: Space within the alveoli sac.

Pleura

• Outer surface of the lungs, made of serous membrane.

Diaphragm

• Main muscle of respiration.
• Supplied by the phrenic nerve.

Composition of Inspired and Expired Air

• Percentage of oxygen and carbon dioxide in inspired and expired air:
  • Inspired Air: Oxygen 21%, Carbon Dioxide 0.04%, Nitrogen 78%
  • Expired Air: Oxygen 16%, Carbon Dioxide 4%, Nitrogen 78%