Chapter 10 Respiratory System and Gas Exchange
Function of the Respiratory System To obtain oxygen (O 2 ) for all cells in the body. To rid the cells of waste gas (CO 2 ).
Oxygen (O 2 ) is vital chemical for most life on Earth. Oxygen is used in chemical reactions to release energy from food. Carbon dioxide (CO 2 ) is a common waste. Organisms that require oxygen to survive are known as aerobic.
The four processes of Respiration 1. Breathing- involves Inspiration taking in air Expiration releasing air 2. External Respiration O 2 /CO 2 exchange between air and blood (occurs in lungs) 3. Internal Respiration O 2 /CO 2 exchange between blood and cells (in body cells) 4. Cellular Respiration Complex chemical reactions that consume O 2 ; produce CO 2 and energy (occurs in mitochondria)
Respiratory Surfaces The area available for the exchange of gases (O 2 and CO 2 ). In humans, the respiratory surface is the Lung. Requirements of the respiratory surface: 1. It must be large to be efficient. 2. It must be moist to allow gases to dissolve and allow diffusion across the cell membranes.
LE 42-19 Respiratory medium (air or water) O 2 CO 2 Respiratory surface Organismal level Circulatory system Cellular level Energy-rich fuel molecules from food Cellular respiration ATP
Respiratory Surface of Fish- Gills
Respiratory Surface of Humans- Lungs Found within chest cavity of a human. Humans have 2 lungs: Left lung has 2 lobes, Right lung has 3 lobes. Left lung has 2 lobes making it slightly smaller than right lung to make room for the heart. Contains thousands of Alveoli (tiny air sacs) that inflate with air. Surface area of a typical human lung can cover a Tennis Court.
The lungs are divided into lobes. Right Lung: 3 Lobes Left Lung: 2 Lobes
The lungs are protected by a multi-layered pleura. A painful and dangerous condition known as pleurisy occurs when the pleura become inflamed.
Structures of the Human Respiratory System
LE 42-23 Branch from pulmonary vein (oxygen-rich blood) Branch from pulmonary artery (oxygen-poor blood) Terminal bronchiole Nasal cavity Pharynx Alveoli Larynx Esophagus Trachea Left lung Right lung Bronchus Bronchiole Diaphragm Heart SEM Colorized SEM
Parts of the Upper Respiratory Tract and their functions 1. Nasal cavity : Air first enters through the nostrils into the nasal cavity. The nasal cavity prepares the air for the sensitive lungs. In this cavity, small bones called turbinates are suspended. These contain a thin membrane that secretes mucous to filter the air. The area also has a high amount of capillaries which warm and moisten the air.
2. Pharynx (throat) : This prepared air goes to the pharynx. 3. Glottis : The glottis is the opening of the trachea (the passageway that conducts air to the lungs). 4. Epiglottis: The epiglottis can block flow to the lungs so that food is kept out. When inspiring, the epiglottis opens and air can travel into the larynx. 5. Larynx (Voice Box) : The larynx contains the vocal cords. From the larynx, air travels through the trachea. 6. Trachea (windpipe): Semicircular rings of cartilage support the trachea. NOTE: All structures listed so far are lined with ciliated cells that secrete mucus that trap particles and dust.
Lower Respiratory Tract 7. Bronchi: At about armpit-level, the trachea branches into two bronchi. 8. Bronchioles: Each bronchus enters a lung and produces a network of smaller tubes: bronchioles.
9. Alveoli (Alveolus): Bronchioles eventually end with a cluster of grape-like tiny sacs alveoli. Gas exchange occurs in the alveolus.
Alveoli- Specially Designed for Gas Exchange: 1. Their shape maximizes respiratory surface area. 2. Alveolar cell walls are one cell thick, allowing as many as possible. 3. Alveoli are connected to a network of capillaries. Much exchange is done by simple diffusion. However, up to 30% of oxygen transport may be done by protein pumps.
Structures that aid in Human Respiration 1. Cilia are hair-like structures that can trap bacteria, dust and other particles. It helps to remove mucus and trapped foreign material. 2. Mucus membranes secrete mucus which traps bacteria, dust and other particles. It also moistens the air. 3. Large surface area of alveoli helps to increase gas exchange.
Steps in Gas Exchange A. Oxygen is brought to the surface of an alveolus by inhaling air. B. Oxygen diffuses across the alveolar membrane via a concentration gradient and into a capillary. Water is needed at the surface between the alveolus and the capillary to facilitate the diffusion of gases (O 2 and CO 2 ).
C. At the same time, carbon dioxide (CO2) in the blood diffuses across the membrane and into an alveolus. This happens in the opposite direction to Oxygen. The CO2 is then sent back up the airway to be expelled to the outside.
Breathing The process that ventilates the lungs is breathing, the alternate inhalation and exhalation of air Ventilation relies on the principle that air will flow from a region of higher pressure to a region of lower pressure. When we breathe, we use two muscular structures to control the air pressure inside our lungs: the intercostal muscles and the diaphragm.
Terms: The diaphragm is a muscular layer that separates the region of the lungs (thoracic cavity) from the region of the stomach and liver (abdominal cavity). The intercostals muscles are those muscles associated with the ventral surface of the rib cage.
LE 42-24 Rib cage expands as rib muscles contract Air inhaled Rib cage gets smaller as rib muscles relax Air exhaled Lung Diaphragm INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up)
Process of Inhalation 1) The ribs move up and out 2) The diaphragm moves down. 3) The intercostal muscles contract When the above happens it increases the volume of the chest cavity. This creates a low pressure inside the chest. The pressure inside the chest is less than the pressure outside the body. Air rushes into the lungs from the outside. The lungs inflate
Process of Exhalation: 1) The ribs move down and in. 2) The diaphragm moves up 3) The intercostal muscles relax. When this happens, it decreases the volume of the chest cavity. This creates a high pressure inside the chest. The pressure inside the chest is greater than the pressure outside the body. Air is forced out of the lung. The lungs deflate.
Lung Capacity Tidal volume (TV) is the volume of air inhaled and exhaled in a normal breathing movement. (about 500 ml) Inspiratory reserve volume (IRT) is the additional volume of air that can be taken in beyond a regular (tidal) inhalation. (about 2000 ml) Expiratory reserve volume (ERT) is the additional volume of air that can be forced out of the lungs beyond the regular (tidal) exhalation. (about 1500 ml) Vital capacity (VC) is the total volume of gas that can be moved into or out of the lungs. VC = TV + IRT + ERT For average human VC = 500 ml + 2000 ml + 1500 ml = 4000 ml or 4 L Residual volume is the amount of gas that remains in the lungs and the passageways of the respiratory system even after a full exhalation. (about 1500 ml) (note: this amoutn of air never leaves the lungs, because if it did, the lungs would collapse)
Residual volume
Respiratory Impairment When diseases attack the respiratory system, they not only hurt the lungs but compromise the entire body s health by preventing the needed oxygen from getting to where it is needed.
Lung Cancer Uncontrolled growth of abnormal cancer cells in the lungs. These cells form tumours known as carcinomas. Leading cancer killer in North America. Death is often not due to breathing problems but by the cancer spreading to other parts of the body.
Lung Cancer Causes 87% of lung cancer cases are the result of cigarette smoking. Cigarettes contain cancer-causing compounds known as carcinogens. Another leading cause is exposure to radioactive radon.
Lung Cancer Symptoms Symptoms can include: Chronic cough Coughing up blood Weight loss Loss of appetite Shortness of breath Fever Symptoms do not always appear early on.
Lung Cancer Treatment Areas of the lungs with tumours can sometimes be removed through surgery. Chemotherapy and radiation therapy can also be used to kill cancer cells. These treatments often carry harsh side effects.
Pneumonia Inflamed alveoli filed with fluid. Oxygen uptake ability is reduced. Leading cause of death in the past still lethal today.
Pneumonia can affect an entire lobe (Lobar Pneumonia) or a series of bronchioles (Bronchial Pneumonia).
Pneumonia Causes The causes vary from bacteria, viruses, fungi, parasites. Other factors can cause Atypical Pneumonia. Before the cause of SARS was found, it was assumed to be an atypical pneumonia. Idiopathic Pneumonias are caused by either unknown agents or arise naturally.
Pneumonia Treatment The treatments for pneumonia vary depending on the cause. Bacterial pneumonia can be treated with antibiotics and is usually not fatal. Most people can recover with rest, ample fluids, and time. If the pneumonia is severe, breathing may need to be mechanically assisted.
Chronic Obstructive Pulmonary Disease COPD is a series of diseases that narrow airways, ultimately resulting in reduced gas exchange.
Emphysema Alveoli in persons with emphysema have become distended. Distended alveoli are less elastic and lack much of the needed surface area. Alveoli in persons with emphysema have become distended. Distended alveoli are less elastic and lack much of the needed surface area. The leading cause is cigarette smoking.
Emphysema is chronic and currently incurable. Treatment can only reduce symptoms and usually involves exercise, drugs to help alveolar function and supplemental oxygen.
Chronic Bronchitis The bronchi of the lungs are constantly inflamed and full of mucous. This reduces the amount of air that can flow to the alveoli for gas exchange. Often coughing will bring up the mucous and infections will occur. The leading cause is cigarette smoke. Heavy amounts of dust and inhaling fumes can also trigger the condition.
Chronic Bronchitis: treatment Treatment can involve: Antibiotics (for infections) Bronchodilators (expands bronchi)
Asthma Involves sensitivity to triggers that can cause the airways to become constricted. Both environmental and genetic factors contribute to the condition. Asthma will often come on acutely in attacks in response to a trigger. Triggers can include smoke, pollen, animal hair, dust, mould, pollution, cold air, exercise, stress, foods, medicines, and infections.
Asthma : treatment Treatments include: Trigger avoidance (preventative) Bronchodilators: These biochemically expand the airways. Can be formulated for acute attacks or for prevention. Many studies show Asthma on the rise in urban areas and industrialized nations. This may be due to decreased air quality. Increased amounts of ozone, nitrogen dioxide, sulphur dioxide and car emissions are likely causes.
Impact of Environmental Factors on Asthma : Besides the gases we need to survive, the air we breathe contains many different particles. For people with asthma, these particles can cause and allergic reaction that triggers an asthma attack.
Common particles found in air: i) spores from mildew or mould.; dust and pets; ii) many types of food can also trigger asthma attacks; iii) ozone, nitrogen dioxide, sulfur dioxide, and vehicle emissions; iv) odours from perfumes, room deodorizers, paints, petrochemical fumes, and baby talcum powders contain many airborne particles.