Gas Exchange

Overview of the Respiratory System Lungs work with the circulatory system to ensure that the cells in the body receive oxygen and eliminate carbon dioxide It maintains the concentration gradients of oxygen and carbon dioxide between air in alveoli and blood flowing in adjacent capillaries. The process that requires oxygen and gives off carbon dioxide in the human body is cellular respiration. Ventilation – the filling the lungs with air and breathing that air out Spirometer is a device used to measure ventilation During this time oxygen diffuses into the blood stream and carbon dioxide diffuses into the ling tissue

Monitoring Ventilation in Humans Ventilation Rate – the number of inhalations or exhalations per minute Tidal Volume – the volume of air taken in or out with each inhalation or exhalation By monitoring ventilation rate and tidal volume at rest and then during mild and vigorous exercise the effect of ventilation can be investigated.

Monitoring Ventilation in Humans Monitoring Ventilation Rate Can be done using simple observation or using data-logging An inflatable chest belt is placed around the thorax and air is pumped in with a bladder A differential pressure sensor is then used to pressure variations inside the chest belt due to chest expansions The ventilation rate can be deduced and also the relative size of ventilations but not the absolute size.

Monitoring Ventilation in Humans Monitoring Tidal Volumes Tidal volumes are measured using a spirometer Tidal volume is deduced by how much the lung volume increases or decreases with each ventilation. Ventilation rate is deduced by counting the number of ventilations in a period on the graph on the graph and measuring the time period using the x-axis of the graph. Rate = number of ventilations/time

Overview of the Respiratory System Gas Exchange – the movement/diffusion of gases Gas exchange occurs in 2 places: The Lungs - oxygen from the air of the lungs moves into the blood stream and carbon dioxide moves out Capillary Bed – opposite gas exchange occurs, oxygen diffusion out of the blood stream and into a body cell and carbon dioxide diffuses out of the body into the capillary bed

Overview of the Respiratory System Single cell organisms do not have a ventilation system As long as the oxygen concentration is high on the outside going into the cell is not a problem Our bodies contain millions of cells underneath a layer of dead cell meant to protect the living cells Cells are too far from the outside air to directly make use of the process of diffusion (oxygen and carbon dioxide) The ventilation system and along with the circulatory system function together to pick up oxygen in the lungs and move the oxygen around the body

Overview of the Respiratory System Ventilation system ensures that the concentration of respiratory gases within the lungs encourages diffusion of gases needed for life. So, if you stopped breathing the oxygen in the lungs would not exceed the oxygen in the blood STOPPING THE DIFFUSION OF OXYGEN INTO THE BLOOD

Anatomy of the Ventilation System Gas Exchange occurs within the alveoli

Anatomy of the Ventilation System When you take in air through your mouth or nasal passages: The air first enters your trachea Then your right and left bronchi Then smaller and smaller branches of the bronchi Then very small branches called bronchioles Finally, the air enters the small air sacs in the lungs called alveoli

Anatomy of the Ventilation System Alveoli are found as clusters at the ends of the smallest bronchioles They look like grapes Approximately 300 million alveoli in each lung Each cluster has surrounding capillaries Blood enters the capillaries from the right ventricle via the pulmonary artery Blood is low in oxygen, high in carbon dioxide Oxygen diffuses through 2 cell membranes Must be able to draw

Anatomy of the Ventilation System Alveoli gas exchange Two membranes: First is a single cell membrane making up the wall of the alveolus Two types of cells: Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli to prevent the sides of the alveolus adhering to each other by reducing surface tension. Second is a single cell membrane making up the capillaries Carbon Dioxide diffuses in the opposite direction of oxygen in the same locations As long as you keep breathing and air is refreshed in the lungs the concentration of gases will allow diffusion of both gases

Adaptation of Alveoli Adaptation Advantage Spherical shape of alveoli Provides a large surface area for respiratory gases to diffuse through Flattened, single cell thickness of each alveolus Prevents respiratory gases from having to diffuse through more cell layers Moist inner lining of alveolus Allows for efficient diffusion Associated capillary bed nearby Respiratory gases do not have to diffuse far to reach single cell thick capillaries

Mechanism of Ventilation The lungs are not capable of creating motion on their own The lungs work based on an inverse relationship between pressure and volume. This is created by the muscles and structures that surround the lungs These include the Diaphragm, Intercostal Muscles around the ribs, and muscles in the abdomen An increase in volume will lead to a decrease in pressure. Whatever pressure does volume will do the opposite and vice versa

Mechanism of Inspiration The diaphragm contracts and at the same time the abdominal muscles and external intercostal muscles help raise the rib cage. Collectively, all of these actions act to increase the volume of the thoracic cavity Because the thoracic cavity has an increased its volume, the pressure inside the cavity decreases. This leads to less pressure pushing on the passive lung tissue The lung tissue increases its volume because there is less pressure exerted on it This leads to a decrease in pressure inside of the lungs, also known as a partial vacuum Air comes in through your open mouth or nasal passages to counter the partial vacuum within the lungs. (fills alveoli with air)

Antagonistic Muscles Inhaling Exhaling The external intercostal muscles contract, moving the ribcage up and out The diaphragm contracts becoming flatter and moving down These muscle movements increased the volume of the thorax The pressure inside the thorax therefore drops below atmospheric pressure Air flows into the lungs from outside the body until the pressure inside the lung rises to atmospheric levels The internal intercostal muscles contract, moving the ribcage down and in The abdominal muscles contract pushing the diaphragm up into a dome shape These muscle movements increased the volume of the thorax The pressure inside the thorax therefore rise above atmospheric pressure Air flows of the lungs to the outside the body until the pressure inside the lung falls to atmospheric levels

Different muscles are required for inspiration and expiration because muscles only do work when they contract.

Mechanism of Inspiration So the reverse holds true for expiration Diaphragm relaxes Internal intercostal muscles bring down the rib cage. When exercising all motions become more exaggerated

Causes and Consequences of Emphysema Emphysema – a disease whereby the alveoli in the lungs are progressively destroyed. Leading cause smoking AKA – COPD Chronic Obstructive Pulmonary Disease It’s a chronic disease (which means progresses slowly and last a long time) Turns healthy alveoli into large irregularly shaped structures with gapping holes Reduces surface area Less oxygen gets to the blood stream

Causes and Consequences of Emphysema Main symptom: Shortness of breath Shortness of breath begins as afflicted does exercise and progresses to an inability to get oxygen at all times Causes: Long term tobacco smoking (leading cause) Marijuana smoke (exposure) – yes this extremely safe drug causes emphysema, watch the statistics go up in states that legalized it. Fumes from manufacturing plants Coal dust Air pollution

Causes and Consequences of Emphysema No cure Progression can be slowed drastically with the cessation of smoking or exposure to other risk factors Prevent DON’T SMOKE and wear protective mask when working around dust or chemically fumes

Causes and Consequences of Lung Cancer Lung cancer is a cancerous growth that begins in the lungs. It is prone to spreading (metastasizing) Brain, bones, liver, and adrenal glands are likely target to the cancer cells from the lungs Cancerous growth in the lungs takes over areas of healthy tissue areas that once provided a combination of bronchioles and alveoli Larger the growth the more dysfunctional the lungs become Can lead to internal bleeding

Causes and Consequences of Lung Cancer One or more carcinogen (substances known to cause cancer) Cigarette smoke Other fumes and smoke Best treatment is early diagnosis Lung cancer has a high mortality rate

Lung Cancer Epidemiology – the study of the incidence and causes of disease Surveys are used to look for correlations between disease rates and factors that could be implicated. Correlation does not prove causation but careful analysis can show whether a factor actually causes a disease 5 main causes lung cancer: Smoking – tobacco smoke contains many mutagens that cause tumors to develop. Smoking causes 90% of lung cancer Passive Smoking – exhaled breath from smokers passes carcinogens on to others, both children and other adults Air pollution – the many sources include diesel exhaust fumes, nitrogen oxides from vehicles and smoke from wood and coal fires Radon gas – in some areas it leaks out of rocks especially granite Asbestos and silica – dust from these materials causes cancer if deposited in lungs

Lung Cancer Consequences of lung cancer: Difficulties with breathing Persistent coughing Coughing up blood General fatigue Chest pain Loss of appetite Weight loss Lung cancer is usually fatal as it is only discovered at a late stage when the primary tumor is large and secondary tumor have already developed elsewhere in the body