Respiratory System Structures & Pathway

Respiration Pathways and Structures

Overview of the Respiratory System

• Structure/function of the respiratory system: Understanding how the various components function together for respiration.

• Mechanism of breathing:

  • Inspiration (Inhalation): The process of taking air into the lungs.

  • Expiration (Exhalation): The process of expelling air from the lungs.

• Vital capacity: The maximum amount of air a person can expel from the lungs after a maximum inhalation.

• External vs Internal respiration:

  • External respiration: Gas exchange between the air in the lungs and the blood.

  • Internal respiration: Gas exchange between blood and tissue cells.

• Respiratory disorders: Discussion of various diseases that affect the respiratory system.

Respiration vs Breathing

• Definition: It’s essential to distinguish between breathing and respiration.

Breathing

• Inhalation

  • Oxygen (O₂) and glucose (C₆H₁₂O₆) are critical for the process.

• Exhalation: Byproducts like carbon dioxide (CO₂), and water (H₂O) are expelled.

• Chemical Equation:
  $\text{C}<em>6\text{H}</em>{12}\text{O}<em>6 + 6\text{O}</em>2 \rightarrow 6\text{CO}<em>2 + 6\text{H}</em>2\text{O} + \text{ATP}$

• Mechanism:

  • Diaphragm contracts → Chest expands → Air flows in (Inhalation).

  • Diaphragm relaxes → Chest contracts → Air flows out (Exhalation).

Respiration

• Function:

  • Transporting O₂ from the lungs to cells to create energy.

• Location:

  • Occurs at body cells utilizing external environment (lungs).

• Process: Respiration is continuous and encompasses various steps.

• Muscles involved: Breathing is a physical process involving muscular movement, while respiration at the cellular level is chemical and does not involve muscles directly.

• Energy:

  • Breathing: No energy is released.

  • Respiration: Energy is released in the form of ATP.

Components of Respiration

• Breathing: Essential to supply O₂ for 38 ATP generated by aerobic cellular respiration.

• Four Main Components:

  1. Breathing: Inhalation and exhalation.

  2. External respiration: Gas exchange of O₂ and CO₂ in the lungs.

  3. Internal respiration: Gas exchange between blood and tissue fluids.

  4. Cellular respiration: Conversion of chemical energy to ATP.
     $\text{C}<em>6\text{H}</em>{12}\text{O}<em>6 + \text{O}</em>2 \rightarrow \text{CO}<em>2 + \text{H}</em>2\text{O} + \text{ATP}$

Respiratory Pathway

• Flowchart of the Pathway: The pathway air follows during respiration:

  • Entry:

  • Nostrils/mouth → Nasal cavity/oral cavity → Pharynx → Epiglottis → Glottis → Larynx → Trachea → Bronchi → Bronchioles → Alveolus.

  • Gas Exchange: Occurs at alveoli and pulmonary capillaries for O₂ and CO₂.

Structures of the Respiratory System

• Nasal Cavity:

  • Function:

  • Air enters through nostrils leading to the nasal cavity which:

    • Filters air with hair and mucus.

    • Moistens air with mucus.

    • Warms air with blood.

  • Importance: Warmer, moister air enhances gas exchange efficiency.

  • Connection to other systems: Tear ducts, cranial sinuses, and ears empty into nasal cavities to protect the lungs.

• Pharynx (Throat): Common passageway for air and food.

• Epiglottis: A flap of tissue covering the trachea during swallowing to prevent food from entering the lungs.

• Larynx (Voice Box): Air passes through the larynx into the trachea; contains vocal cords made of two bands of elastic ligaments.

• Trachea (Windpipe):

  • Holds open by C-shaped cartilage rings.

  • Lined with cilia and mucous glands to trap and remove debris; conducts air into the bronchi.

• Bronchi:

  • The trachea divides into left and right bronchi leading to the corresponding lungs.

  • Both have cartilage rings and cilia.

  • Bronchi branch into smaller passageways called bronchioles.

• Bronchioles:

  • Smaller branches; ciliated but lacking cartilage.

  • Carry air to the alveoli, where gas exchange occurs.

• Alveoli:

  • Definition: Singular form is alveolus; sac-like structures at the end of bronchioles.

  • Function: Primary site for gas exchange; rich in capillary network due to numerous capillaries for efficient gas exchange.

  • Characteristics:

  • Numerous: Adult lungs contain millions, maximizing surface area for exchange.

  • Thin Walls: Only one cell thick to enhance diffusion.

  • Moist Surface: Promotes effective gas transfer by keeping surfaces wet.

  • Stretch Receptors: Send signals to the brain to initiate exhalation when alveoli are sufficiently stretched.

  • Lipoprotein Layer: Prevents alveoli from collapsing and sticking during exhalation.

Diaphragm and Muscles Involved in Breathing

• Diaphragm:

  • A dome-shaped muscle that separates the chest cavity from the abdominal cavity.

  • Function:

  • Moves downwards during inhalation and upwards during exhalation; regulates volume change in the thoracic cavity.

• Ribs and Intercostal Muscles:

  • Ribs: Connected to the vertebral column and sternum; provide structural support.

  • Intercostal Muscles: Located between the ribs; facilitate rib movement

  • Up and out during inhalation.

  • Down and in during exhalation.

The Lungs

• Location: Suspended in the thoracic cavity, an airtight space formed by the ribcage.

• Lobes:

  • The right lung has three lobes while the left lung has two lobes for heart accommodation.

Pleural Membrane

• Structure: Composed of double membranes enclosing the lungs.

• Function:

  • Outer Pleural Membrane: Adheres to the chest wall and diaphragm; creates a seal.

  • Inner Pleural Membrane: Attaches to thoracic cavity and lungs.

  • Intrapleural Fluid: Facilitates smooth movement during inhalation and exhalation, preventing abrasion.

  • Negative Air Pressure: Created during lung inflation, facilitating air influx during inhalation; keeps lungs attached to chest wall.