The Respiratory System (Unit Test)

The Function of the Respiratory System

The Pathway of the Air

• Air enters through the mouth and nose

• Air passes through the pharynx (throat)

• It travels down to the trachea (windpipe)

• The trachea separates into two branches called bronchi

• The air will eventually reach the alveoli at the end of these branches

Structural Features

• Air enters the mouth/nose → passes through the pharynx (throat) → travels down the trachea (windpipe) → bronchi → lungs

• The trachea and bronchi are lined with epithelial cells → some produce mucus; others are called cilia (hair-like projections)

  • Filter out foreign material

  • The trachea is the tube that takes air from the back of the throat down to the lungs

• The trachea is supported by rings of cartilage to keep it open and allow air to flow through it freely

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Gas Exchange

• The main purpose of the respiratory system is gas exchange

• Oxygen enters the lungs and carbon dioxide leaves by a process called DIFFUSION

• The bronchi branch again and again ending in tiny air sacs called alveoli

  • Each alveolus is surrounded by a network of capillaries

• Oxygen and carbon dioxide must diffuse through 2 thin walls: the walls of the capillaries and the walls of the alveoli

• Diffusion: Substances move from an area of high concentration to an area of low concentration

• The concentration of oxygen in the blood is less than the concentration of oxygen in the alveoli

• Therefore oxygen diffuses from the alveoli into the blood

• At the same time excess carbon dioxide diffuses from the cells into the blood

• CO2 is carried by the blood to the lungs, where it diffuses into the alveoli and expelled outside the body

Gas Exchange Between The Blood and Alveoli

• Each alveolus has a thin wall so that gas exchange between the lungs and the blood can take place quickly.

• In the lungs, oxygen travels to thousands of tiny air sacs called alveoli. These are covered with tiny blood vessels.

• The alveoli give the lungs a huge surface area which is equal in size to the area of a tennis court!

Mechanism of Breathing

• Breathing involves drawing air into the lungs (inhalation) and drawing air out of the lungs (exhalation)

• This process involves:

  • Intercostal muscles (muscles between the ribs that make the rib cage expand and contract): Diaphragm (a large sheet of muscle underneath the lungs)

  • Together the diaphragm and the intercostal muscles increase/decrease the volume of the lungs, also changing the pressure and the air flowing in and out of the alveoli

• Inhalation

  • Intercostal muscles contract

  • Rib cage expands

  • Diaphragm contracts/moves downward

• Exhalation

  • Intercostal muscles relax

  • Rib cage contracts

  • Diaphragm relaxes/moves upward

Control of Breathing

• Breathing is involuntary (we don’t think about it)

• Breathing is controlled by a part of the brain that detects the concentration of CO2 in the blood

• As the level of CO2 increases the brain sends signals to the diaphragm, the intercostal muscles and the heart

• The breathing rate increases and the heart beats faster to decrease the levels of CO2 and increase O2

Respiratory Disorders: Tuberculosis

• TB is an infectious disease (can be spread from person to person)

• Caused by bacteria that grow in the lungs and may also spread to other parts of the body

• Symptoms: fever, cough, weight loss, tiredness, chest pain

• Diagnosed through a chest X ray and to confirm the diagnosis through examinations of stomach or lung secretions

• The bacteria may remain dormant in the body for decades

• Once diagnosed TB can be successfully treated with medicine and a few weeks of hospitalization

Respiratory Disorders: Cancer

• First hand and second hand tobacco smoke is a threat to the respiratory system

• Carcinogens found in cigarettes contribute to cancers of the lungs, mouth, esophagus, larynx, pancreas and bladder

Respiratory Disorders: Severe Acute Respiratory Syndrome

• Severe Acute Respiratory Syndrome (SARS) spread from a region of China to 37 countries around the world

• Canada identified 438 cases; 44 of these patients died

• Symptoms: flu-like, high fever, shortness of breath, dry cough, sore throat, headache, muscle pain, and exhaustion

• Diagnosis is made based on chest X-ray, showing evidence of pneumonia, and positive lab results of cell samples

Respiratory Disorders: Chronic Obstructive Pulmonary Diseases

• ~90% of COPD caused by smoking

• a chronic, progressive disease that involves both:

  • Obstructive Bronchitis

    • Long term cough, inflammation and mucus (similar to asthma)

  • Emphysema

    • Causes permanent damage to the alveoli, they loose elasticity and shape = decrease surface area for gas exchange