The Respiratory System – Key Vocabulary

Function of the Respiratory System

• Supplies the body with life-giving oxygen.
• Removes the waste gas carbon\, dioxide.
• Achieved through three inter-related processes (detailed below).

Main Processes

• Breathing (Ventilation)- Purely physical/mechanical.
• Consists of two opposite phases:
  • Inhalation: air rich in oxygen drawn from atmosphere into lungs.
  • Exhalation: air rich in carbon\, dioxide expelled from lungs to atmosphere.
• Gaseous Exchange- Occurs in the lungs by diffusion (movement of gas molecules from a region of high concentration to one of low concentration across a selectively permeable membrane).
• Oxygen diffuses through alveolar walls → blood.
• Carbon\, dioxide diffuses from blood → alveoli → exhaled.
• Cellular Respiration- Chemical breakdown of energy-rich glucose within cells using oxygen.
• Releases usable energy for cell functioning.
• By-products: carbon\, dioxide and water.

Main Anatomical Components

• Nose / External Nostrils
• Mouth
• Nasal Cavity
• Windpipe (Trachea)
• Bronchial Tubes (Bronchi)
• Smaller Bronchial Tubes (Bronchioles)
• Infundibulum with Alveoli (Air Sacs)
• Lungs
• Diaphragm

Nose & Nasal Cavities

• Two anterior nostrils normally admit inhaled air.
• Nasal cavities:
  • Warm incoming air.
  • Purify via cilia (fine hairs) that trap dust.
  • Moisten air with mucus.
• Abnormal breathing through mouth generally occurs when the nose is blocked (e.g. cold).

Windpipe (Trachea) & Air Passages

• Trachea = tube conducting air from nasal cavities into thorax.
• Held open by rings of cricoid cartilage.
• Bifurcates into two bronchi (singular = bronchus), each entering one lung.
• Inside lung, bronchi further branch → progressively narrower bronchioles.
• Terminal bronchiole ends in an infundibulum bearing many alveoli (bubble-like air sacs).

Lungs

External Structure

• Two spongy, highly elastic, conical, pink-grey organs in chest (thoracic) cavity.
• Protected by:
  • Spine (posteriorly).
  • Ribcage (laterally).
  • Breastbone / sternum (anteriorly).
• Colour due to extensive capillary network.
• Separated medially by space housing the heart.

Internal Structure

• Bronchi branch repeatedly → bronchioles → alveolar clusters; visualised as grape bunch.
• Each alveolus: thin-walled, enveloped by dense capillary network.
• Numerical fact: 200{-}300\,million alveoli per lung.

Diaphragm

• Dome-shaped muscular sheet beneath lungs; principal muscle of breathing.
• Contraction → diaphragm flattens & moves downward → thoracic volume ↑ → lungs fill with air (inhalation).
• Relaxation → diaphragm domes upward → thoracic volume ↓ → air forced out (exhalation).

Summary of Ventilatory Movements

• Inhalation: diaphragm contracts (down), ribs may rise, lungs expand.
• Exhalation: diaphragm relaxes (up), lungs recoil, air expelled.

Health Issues Involving the Respiratory System

• Asthma
  • Allergic inflammation & narrowing of airways.
  • Symptoms: wheezing, chest tightness, shortness of breath, coughing.
  • Influenced by genetic & environmental factors.
• Lung Cancer
  • Uncontrolled cell growth forming tumours in lung tissue.
  • Impairs lung ability to oxygenate blood.
  • Symptoms: chest pain, dyspnoea, chronic cough/wheezing, weight loss.
  • Predominantly linked to smoking & air pollution.
• Bronchitis
  • Swelling of bronchial tube lining (infection).
  • Airways congested with excess mucus.
  • Symptoms: coughing, wheezing, shortness of breath.
  • Frequently caused by smoking or inhaling polluted air.
• Tuberculosis (TB)
  • Contagious bacterial disease (inhaled pathogens).
  • Bacteria destroy lung tissue → reduced breathing efficiency.
  • Severe coughing may rupture capillaries → haemoptysis (blood in sputum).
  • Prevention/treatment: vaccination & specific antibiotics.
• Pneumonia
  • Lung infection causing alveoli to fill with fluid.
• Emphysema
  • Persistent mucus build-up blocks bronchi.
  • Enzymatic destruction of alveolar walls → reduced elasticity.
  • Inefficient gaseous exchange.
• Asbestosis
  • Inhalation of asbestos fibres.
  • Fibres lodge in lungs, damaging tissue.
  • Impedes absorption of oxygen; breathing becomes difficult.

Miscellaneous Details / Figures Referenced

• Illustrations (not reproduced here) depict diaphragm motion during breathing and show normal vs inflamed bronchial tubes & TB bacteria imagery.
• Textual aside: "You take my breath away" (humorous reference).

Connections & Significance

• Proper understanding of diffusion underpins gaseous exchange efficiency.
• Diseases often compromise either airway patency (asthma, bronchitis) or alveolar integrity (emphysema, pneumonia), directly lowering diffusion surface or air flow.
• Lifestyle factors (smoking, air pollution) recur as major etiological themes, highlighting public-health relevance.