Notes on Respiratory System Lecture

Introduction

• Respiratory system acquires oxygen and removes carbon dioxide.
• Oxygen is needed for ATP production; CO2 is a byproduct that must be removed.
• Excessive CO2 is harmful.

Main Structural Components

1. External Nose
   • Entry point for inhaled air.
2. Nasal Cavity
   • Cleans air with nose hairs.
   • Warms and humidifies air with mucous membranes.
3. Pharynx (Throat)
   • Common passageway for air and food.
4. Larynx (Voice Box)
   • Breathing and voice production.
5. Trachea (Windpipe)
   • Connects to bronchi.
6. Bronchi and Lungs
   • Bronchi branch into lungs; air travels through alveoli (air sacs).
   • Alveoli are main sites for gas exchange.

Respiratory Tracts

• Upper Tract: Nose to Larynx.
• Lower Tract: Trachea to Alveoli.

Conducting vs. Respiratory Zones

• Conducting Zone: Air passage; no gas exchange.
• Respiratory Zone: Site of gas exchange.

Respiratory Processes

1. Ventilation: Movement of air in and out of lungs.
2. External Respiration: Gas exchange between lungs and blood.
3. Internal Respiration: Gas exchange between blood and tissues.

Functions of the Respiratory System

• Regulate blood pH by removing CO2.
• Produce chemical mediators (e.g., ACE for blood pressure regulation).
• Voice production via the larynx.
• Olfaction (smell) through scent particles.
• Protection against microorganisms using nasal hairs and mucous.

Anatomy Details

1. Nasal Cavity
   • Remains open for breathing, even during eating.
   • Cleans, humidifies, and affects voice resonance.
2. Pharynx
   • Divided into nasopharynx, oropharynx, and laryngopharynx.
3. Larynx
   • Contains thyroid cartilage (Adam's apple) and epiglottis (prevents food entry).
4. Trachea and Bronchi
   • Trachea: C-shaped cartilage rings, lined with ciliated columnar epithelium.
   • Bronchi: Extensions of trachea; branch into bronchioles and alveoli.
5. Alveoli
   • Sites for gas exchange, surrounded by capillaries.
   • Respiratory membrane facilitates diffusion.

Lungs

• Structure: Cone-shaped; right lung has 3 lobes, left lung has 2 lobes.
• Blood Flow: Oxygenated blood leaves lungs, deoxygenated blood arrives for gas exchange.
• Lymphatic Supply: Superficial and deep lymphatic vessels.

Pleural Membranes and Cavities

• Pleural Cavity: Space around lungs.
• Pleura: Double-layered membrane (parietal pleura lines cavity, visceral pleura covers lungs).

Ventilation Process

• Muscles of Inhalation: Diaphragm, external intercostals, pectoralis minor, scalene muscles.
• Muscles of Exhalation: Internal intercostals, transverse thoracis, abdominal muscles.

Breathing Types

• Quiet Breathing: Passive exhalation.
• Labored Breathing: Intense inhalation and exhalation using additional muscle work.

Gas Exchange

• In Lungs: Oxygen enters blood from alveoli; CO2 exits into alveoli.
• In Tissues: Oxygen from blood to tissues; CO2 from tissues to blood.

Regulation of Breathing

• Medullary respiratory center regulates respiratory rate to maintain gas levels.
• Hering-Breuer Reflex: Prevents lung overinflation.

Microscopic Anatomy

• Nasal cavity, pharynx, larynx, trachea, and alveoli studied histologically.
• Histological features include pseudostratified ciliated columnar epithelium and hyaline cartilage in trachea and bronchi.

This comprehensive overview of the respiratory system covered its structural anatomy, processes involved in breathing, and the microscopic examination of key components.