Bio res sys

Human Biology - Respiratory System

Introduction

• Instructor: Masoud Akhtar

• Email: m.akhtar.5@bham.ac.uk

• University: University of Birmingham

Learning Objectives

• Describe the structure and function of key respiratory system components

• Define concepts of inspiration and expiration and explain the changes in lung volume and pressure during these phases

• Explain the process of gas exchange in the alveoli

• Define emphysema and describe structural changes in the lungs associated with this condition

Structure of the Respiratory System

• Components:

  • Nasal cavity

  • Nostril

  • Pharynx

  • Oral cavity

  • Trachea

  • Larynx

  • Bronchi (Right and Left main bronchus)

  • Lungs (Right lung, Left lung)

  • Base of lungs

  • Diaphragm

Pharynx

• Definition: Membrane-lined cavity behind the nose and mouth, connecting them to the esophagus (digestion) or trachea (respiration).

Larynx

• Definition: Hollow muscular tube forming an air passage to the lungs, containing the vocal cords.

• Epiglottis: A lid that prevents food from entering the windpipe and lower airways.

Airway Components

• Trachea:

  • Tube reinforced by cartilage rings, extending from the larynx to the bronchial tubes.

  • Conducts air to and from the lungs.

• Bronchi:

  • Conducts air into the lungs and branches into bronchioles.

  • Lined with smooth muscle for dilation and constriction.

Functions of the Lungs

• Organs of ventilation containing alveoli for rapid gas exchange.

• Enclosed in the thorax and lined with pleural membranes to reduce friction.

Respiration and Gas Exchange

• Respiration: Metabolic process using O2 and producing CO2 for ATP energy; occurs in cytoplasm and mitochondria.

• Gas Exchange:

  • O2 and CO2 exchange between alveoli and blood capillaries through diffusion.

  • Large diffusion gradients maintained by ventilation and circulation.

Alveoli Structure and Function

• Composed of a single layer of flattened cells to minimize diffusion distance.

• Covered by a dense network of capillaries to maintain concentration gradients.

• High numbers of alveoli maximize surface area for effective gas exchange.

• Surfactant: Secreted fluid to maintain moist conditions and prevent alveolar collapse.

Gas Exchange Process

• Gas exchange (O2 in, CO2 out) occurs across the alveolar-capillary membrane through:

  • Squamous epithelium promoting short diffusion pathways and large surface area.

  • Proper ventilation and circulation to maintain gradients.

Types of Pneumocytes

• Type I Pneumocytes:

  • Flattened, thin cells lining alveoli, responsible for gas exchange.

• Type II Pneumocytes:

  • Rounded cells producing surfactant to prevent alveolar sticking.

Boyle's Law

• Law Definition: As volume increases, pressure decreases (inversely proportional).

• Formula: pV = k, P₁V₁ = P₂V₂

Ventilation (Breathing)

Inhalation

• Diaphragm contracts, expanding thoracic cavity.

• Volume increases, Pressure decreases in the lungs, drawing air in.

Exhalation

• Diaphragm relaxes, decreasing thoracic cavity volume.

• Volume decreases, Pressure increases in the lungs, expelling air.

Emphysema

Definition

• Condition where alveoli weaken and rupture, reducing surface area for gas exchange.

Causes

• Long-term exposure to airborne irritants:

  • Tobacco smoke

  • Air pollution

  • Chemical fumes and dust

Effects

• Symptoms include shortness of breath, coughing, wheezing, and chest tightness.

Treatment

• Focus on maximizing remaining lung function:

  • Bronchodilator medications

  • Oxygen therapy

  • Lung transplant

Key Summary

• The respiratory system involves various structures enabling breathing, consisting of the nose, trachea, and lungs.

• Gas exchange occurs in the alveoli via diffusion of oxygen into the bloodstream and carbon dioxide out.

• Emphysema results in reduced lung elasticity and surface area for gas exchange.