Human Respiratory System Lecture Notes

Introduction

• The respiratory system is essential for breathing and involves various components and processes.
• Air we breathe contains oxygen, water, other gases (e.g., krypton, radon), and particles.

Upper Respiratory Tract

• Protection Mechanisms:
  • Nasal Cavity: Nasal hair stops large particles.
  • Nasal Mucosa: Traps small particles.
  • Ciliated Cells: Move mucus towards the pharynx, known as mucociliary clearance.
• Air Conditioning:
  • Nasal and oral cavities warm and moisten air.
• Swallowing Mechanism:
  • Epiglottis: Prevents food/liquid from entering the lower respiratory tract by closing the larynx.

Lower Respiratory Tract

• Trachea:
  • Reinforced with hyaline cartilage rings.
  • Branches into two main bronchi at the heart.
• Lungs:
  • Right Lung: 3 lobes, 10 lung segments.
  • Left Lung: 2 lobes.
  • Lungs receive deoxygenated blood from the pulmonary arteries and return oxygenated blood to the heart via the pulmonary veins.
• Bronchial Tree:
  • Main bronchi form the trunk.
  • Bronchi branch into bronchioles, ending in alveoli.

Gas Exchange

• Alveoli:
  • Tiny air sacs (300-400 million) for gas exchange.
  • Composed of type 1 pneumocytes for thin diffusion layers.
• Blood Flow:
  • Red blood cells (erythrocytes) carry oxygen and release carbon dioxide.
  • Iron in erythrocytes binds with oxygen.
• Diffusion Process:
  • Oxygen enters alveoli; carbon dioxide is released into alveoli.

Breathing Mechanism

• Muscles Involved:
  • Neck Muscles: Raise sternum and upper ribs.
  • Rib Muscles: Raise and lower ribs.
  • Diaphragm: Primary muscle for breathing.

Types of Breathing

• Chest Breathing:
  • Outward rotation of ribs increases chest volume (bucket-handle motion).
  • Sternum movement (pump-handle motion).
• Diaphragmatic Breathing:
  • Natural at rest; involves diaphragm rising and lowering.

Pleura

• Function:
  • Acts as lubrication for lung movement against the chest wall.
• Structure:
  • Inner pleura covers lungs, outer pleura lines ribcage and diaphragm.
  • Pleural cavity allows sliding movement.