20. ANATOMY OF RESPIRATORY ORGANS AND FUNCTIONS

Anatomy of Respiratory Organs and Functions

Introduction:

The cells of the body require energy for all metabolic activities, which is primarily derived from chemical reactions that depend on oxygen (O2).

The main waste product of these reactions is carbon dioxide (CO2). The respiratory system allows oxygen to enter the body and provides a route for excretion of carbon dioxide.

Air entering the body is conditioned by temperature, humidity, and cleanliness. Blood transports O2 and CO2 between the lungs and cells. Gas exchange between blood and lungs is called external respiration, while exchange between blood and cells is internal respiration.

The main organs of the respiratory system include:

  1. Nose
  2. Pharynx
  3. Larynx
  4. Trachea
  5. Lungs
  6. Pleura
  7. The Respiratory Membrane

Nose:

  • Also called external nares, divided into two halves by the nasal septum.
  • Contains paranasal sinuses for warming air and cilia for filtering foreign particles.
  • Nostrils allow entry of air; the nasal cavity is divided by a septum.
  • Olfactory receptors in the superior nasal cavity detect smell.
  • Respiratory mucosa warms, moistens, and filters air; ciliated cells move mucus toward the throat.
  • Conchae increase surface area and turbulence for air conditioning.
  • Palate separates nasal and oral cavities; hard anteriorly, soft posteriorly.
  • Paranasal sinuses lighten the skull and act as a resonance chamber for speech.

Pharynx:

Also called the throat, it is a common pathway for air and food, lined with mucosa and skeletal muscles for swallowing.

Three Sections of the Pharynx:

  • Nasopharynx: Contains pharyngeal tonsils (adenoids) for immune defense.
  • Oropharynx: Contains palatine tonsils, aiding immunity.
  • Laryngopharynx: Bottom section where respiratory tract divides into esophagus and larynx.

Larynx:

  • Also called the voice box; prevents swallowed materials from entering the lower respiratory tract.
  • Conducts air to the lower respiratory tract and produces sound.
  • Supported by nine cartilages held by ligaments and muscles.

Trachea:

  • Flexible tube (windpipe) extending from larynx through the mediastinum, anterior to the esophagus.
  • Cartilage rings maintain rigidity to keep the trachea open.
  • Trachea bifurcates at the sternal angle into right and left primary bronchi, leading to each lung.

Lungs:

  • Conical organs resting on the diaphragm; apex projects superiorly, base rests on diaphragm.
  • Separated by the mediastinum; costal surface contacts thoracic wall.
  • Left lung: Two lobes, smaller, with cardiac notch.
  • Right lung: Three lobes, slightly higher due to liver position.

Pleura:

  • Serous membrane lining lungs and thoracic walls.
  • Visceral pleura covers lungs; parietal pleura lines thoracic walls, mediastinum, and diaphragm.
  • Pleural cavity is a potential space with serous fluid reducing friction during breathing.
  • Pleural effusion is excess fluid in the pleural space (pleuritis).

The Respiratory Membrane:

  • Alveolar walls are primarily a thin layer of squamous epithelial cells.
  • Alveolar pores connect neighboring air sacs, providing alternative routes for air.
  • The respiratory membrane (air-blood barrier) consists of alveolar and capillary walls, fused basement membranes, and occasional elastic fibers for gas exchange.
  • Alveolar macrophages (“dust cells”) remove bacteria, carbon particles, and debris.
  • Cuboidal cells produce surfactant, a lipid coating crucial for lung function.

Detailed Notes:
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PATH: PHARMD/ PHARMD NOTES/ PHARMD FIRST YEAR NOTES/ HUMAN ANATOMY AND PHYSIOLOGY/ ANATOMY OF RESPIRATORY ORGANS AND FUNCTIONS.

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