Topic 21: The Respiratory System

 Way back (last term) we studied cellular respiration.  While it is dependent on respiration, it is NOT the same!
Respiration is the process of taking in oxygen and releasing carbon dioxide.  Cellular respiration includes the chemical reactions that use oxygen to convert the energy in glucose into ATP (the universal energy carrier) and the byproducts, water and carbon dioxide.  Respiration is needed to get oxygen to the cells for these reactions to occur and to get rid of the carbon dioxide that is produced.  The exchange of these gases occurs at the lungs (tüdő).

THE RESPIRATORY TRACT

Air enters the respiratory tract through the nose and the mouth.  It is always best to inhale through the nose, as the nose is lined with epithelial cells that contain lots of capillaries, which helps to warm and moisten the air before it moves down the tract.  This epithelia is also cilliated epithelia, which along with the hairs that grow near the entry to the nose, help to filter out dust and other pollutants from the air.

The pharynx (garat) is the common passageway for food and air that branches into the esophagus (for food) and the trachea (légcső) (for air) at its base.  The trachea begins at the epiglottis, which moves to block the passage of food into the trachea.  The larynx (voicebox/gége) is found right under the epiglottis, at the entrance to the trachea.

The larynx is a made of pieces of cartilage, with the vocal cords stretched across them.  When we breathe, the cords are relaxed and the air can pass between them easily, so no sound is made.  When we speak, the cords are contracted, narrowing the passage between them.  As the air moves past them, it causes the cords to vibrate, creating sound.  The pitch of the voice depends on the size of the larynx (larger means a deeper voice - in men the larynx is often so large that it protrudes from the front of their neck forming the Adam's apple (Ádám csutka).  It is also determined by the thickness of the vocal cords and how tightly they are contracted (thicker, less contracted = deeper pitch).  The shape and size of a person's sinuses also affects the resonance of a person's voice (hence the flatness of a person's voice when their sinuses are congested).

The trachea (windpipe) is formed by C-shaped cartilage rings to maintain its form, so it doesn't collapse.  It leads down to the bronchi (főhörgők), which branch into the left and right lungs.  The right lung is formed of  3 lobes, while the left is formed of 2.  The bronchi branch further inside the lungs into the bronchioles (hörgők, hörgőcskék), which open into the alveoli (légholyagok).  Each lung contains thousands of alveoli, making the breathable surface area of the lungs approximately 100 square meters!

The alveoli are "wrapped" in capillaries via which gas exchange takes place.  Oxygen crosses from the alveoli into the blood, while CO2 passes from the blood into the alveoli.  This movement of the gas molecules occurs simply as a result of the partial pressures of the gases in the blood and the lungs.

BREATHING

In order for gas exchange to take place in the alveoli, air needs to enter the lungs to bring in oxygen and it needs to leave the lungs to take away the carbon dioxide.  The movement of air is breathing.  

Inhalation is the result of the contraction of the rib muscles (intercostal muscles), which raises up the rib cage, and the contraction of the diaphragm (rekeszizom), which stretches across the base of the rib cage (in a lower position than when it is relaxed).  This increase the size of the cavity in which the lungs are found, resulting in a lower pressure in the chest cavity.  This difference in pressure results in air moving into the lungs in order to equalize the pressure.  Because the muscles contract, this is an active process and requires energy.

When the rib muscles and the diaphragm are relaxed, then the size of the chest cavity decreases, forcing the air out.    

The Donders model demonstrates how the change in the size of the chest cavity (due to muscle contraction) results in a change in pressure (as it enlarges pressure decreases and vice versa) and how this results in the movement of air into and out of the lungs.

Control over breathing is vegetative (automatic) and occurs in the medulla (part of the brain stem).  It gains information on the levels of CO2 and O2 in the blood and depending on the levels increases or decreases depth and speed of breathing.

Illnesses and Conditions associated with respiration

•       Everday illnesses:

–      Colds (natha) are caused by bacteria or viruses.  They include congestion, runny nose,  and sore throat.

–      Flu is caused by viruses.  It shares symptoms with colds, but also includes fever, weakness and exhaustion

–      Sinusitis (arc- és homloküreg gyulladás) is often associated with increased mucus production with a cold or flu.  Sinuses become plugged and cannot empty the mucus that is produced.  It is often a painful condition.

•       Tonsillitis is the inflamation of the tonsils (torokmandula).  It is caused by bacterial infections and is associated with pain and fever.  It can lead to heart and kidney problems if it is left untreated.

•       Laryngitis (hangszalaggyulladás) is the inflammation of the vocal cords, due to overuse or infections.  It can result in a sore throat, raspy voice, or the complete loss of vocal function for the duration of the inflammation.

•       Bronchitis (hörghurut) is the inflammation of the bronchi.  It is often associated with fever, difficulty breathing and coughing. Air pollution (eg. cigarette smoke) makes it worse.  Smokers often have chronic bronchitis.

•       Asthma:

–      associated with coughing fits and difficulty breathing

–      symptoms appear suddenly (typically)

–      appears to be hereditary

–      fits can be brought on by upper respiratory tract infections, allergies, physical exertion or stress

–      if not treated, can have serious consequences

•       Pneumonia (tüdőgyulladás):

–      when the infection moves from the respiratory tract into the lungs

–      symptoms can range from none to fever, pain, difficulty breathing, coughing

–      lungs fill with fluid, reducing area of gas exchange

–      can result it scar tissue, cysts, pleurisy

•       Pleurisy (mellhártyagyulladás)

–      Inflammation of the pleura (double-layered membrane surrounding the lungs)

–      Usually the result of other infections or conditions

–      Breathing  is painful

–      When fluid fills the spaces between the membranes it is called pleural effusion

•       Tuberculosis (TB) (tbc in Hungarian)

–      Caused by bacteria (usually Mycobacterium tuberculosis)

–      Spreads through coughing and sneezing

–      Destroys lung tissue, if left untreated patients cough up blood, may have fever, night sweats, weight loss

–      Infection can affect other parts of the body (nervous system, bones, intestines, reproductive organs)

–      can be prevented with the BCG vaccine and treated with antibiotics

•       Pneumothorax (légmell)

–      Lung(s) collapse because air or gas gets into the (plearal space) chest cavity

–      Symptoms: chest pain, shortness of breath

–      Usually the result of injury or surgery, air may be extracted with a chest tube or syringe

–      Can also be spontaneous (no known cause), these usually only require observation, disappear on their own

•       Lung cancer

–      Most common over 50 and in men

–      Symptoms: shortness of breath, wheezing, persistent cough, hoarseness, chest pain

–      Causes associated with air pollution, especially smoking

•       Hypoxia

                low levels of blood oxygen

                various causes: CO poisoning, low haemoglobin levels

                typical symptom cyanosis – blue at base of nails, lips, ear lobes and ends of fingers

•       Caisson’s disease (the bends, decompression sickness)

–      Occurs when the body becomes depressurized and the gases that were dissolved in the blood plasma under higher pressure, now form bubbles in the blood

–      Since bubbles can form in or migrate to any part of the body, it can produce many symptoms, and its effects may vary from joint pain and rashes to paralysis and death.