Chapter 10 Respiration

Transcription

1 1 Chapter 10 Respiration Introduction/Importance of the Respiratory System All eukaryotic organisms need oxygen to perform cellular respiration (production of ATP), either aerobically or anaerobically. Respiration Cellular respiration All organisms respire, or exchange gases with their environment Respiratory system in humans is closely linked with the circulatory system and the digestive system. Section 10.1 The Respiratory System Outcomes: I can explain the need for a respiratory surface in humans I am able to identify and state the function of the following respiratory structures: nasal cavity, epiglottis, trachea, bronchi, bronchioles, alveoli, diaphragm The basic function of the respiratory system is to distribute oxygen to each cell and allow carbon dioxide to leave each cell. This gas exchange helps to maintain homeostasis in the body. All respiratory systems share certain requirements for gas exchange (regardless of the type of organism): The surface through which gas exchange takes place must be: large to allow for efficient gas exchange thin walled so diffusion can occur rapidly moist - O 2 and CO 2 need to dissolve in contact with a source of O 2 in contact with a transport system that carries dissolved materials to and from the cells The Human Respiratory System

2 2 Lungs Gas exchange organs in air-breathing vertebrates and some other animals The lungs fill a large area of the human s chest cavity Each lung is divided into lobes; three on the right and two on the left (to make room for the heart) and enclosed by a two-layered membrane called the pleura. Visceral pleura inner pleura directly surrounding the lungs Parietal pleura outer pleura surrounding the lungs and which is in contact with the diaphragm and other organs of the chest cavity In between the pleural membranes is a lubricating fluid which allows the lungs to move freely during breathing. The lungs are separated from the abdominal cavity by the diaphragm - large muscle that forms the floor of the chest cavity and plays a role in breathing. The Pathway of Air The respiratory system is broken down into two parts: 1. The Upper Respiratory Tract 2. The Lower Respiratory Tract The Upper Respiratory Tract Air may be taken in through the mouth or the nose. Inhaling through the nose is more beneficial; Nasal cavity Air usually enters the respiratory system through the nostrils which lead to the hollow nasal passages. Hairs at the opening of the nostrils help keep foreign particles from entering. The air passageway (except mouth) has cilia and mucus secreting membranes which help trap unwanted particles from the air. Mucus also moistens the air As air passes through the nose, the air is warmed by the capillaries that lie below the mucus membrane. They also increase the humidity of the air. When you breathe through your mouth, you lose the advantages of filtering, warming and moistening the air before it enters the lungs Pharynx The section where the mouth and nasal cavity connect to the larynx and the esophagus. Also known as the throat Larynx Composed of cartilage Also known as the voice box The vocal cords are two pairs of membranes stretched across the inside of the larynx As air is breathed out the vocal cords vibrate allowing you to speak The larynx runs directly into the

3 3 Glottis Opening of the trachea. It is protected by the epiglottis a flap like structure that prevents food from entering the lungs by closing over the glottis when you swallow. Trachea Also known as the windpipe. It is kept open by cartilage. The trachea connects the air to the lungs The trachea is supported with horse shoe cartilage rings which prevent the trachea from collapsing. Foreign particles are removed by sweeping cilia. They sweep the mucus and trapped foreign particles to the nose and throat area where it can be removed by sneezing, swallowing, coughing, or spitting. The Lower Respiratory Tract Bronchi, Bronchial tubes, Bronchioles In the middle of the chest, the trachea divide into two bronchi (singular bronchus). One of these cartilage lined tubes enters each lung. Also lined with ciliated cells In the lungs the bronchi branch in a tree like fashion into bronchial tubes Bronchial tubes divide and divide into bronchioles Walls become thinner and thinner and are lined with ciliated mucus membranes. Alveoli At the end of each bronchiole tubule is a grape-like cluster of tiny sacs known as alveoli (singular alveolus). These structures are the respiratory surface where actual gas exchange occurs. The total surface area of the alveoli is about 40 times that of the surface area of the skin. These sacs are surrounded by a network of capillaries that deliver O 2 and remove CO 2 from the blood stream. Most gas exchange happens through simple diffusion but facilitated diffusion delivers a portion of O 2 to the bloodstream (allows more, faster) Section The Mechanics of Breathing Outcomes I can explain the mechanics of breathing (inhaling and exhaling), and gas exchange Gas exchange in humans is divided into four stages: 1. Breathing 2. External Respiration 3. Internal Respiration 4. Oxygen Transport

4 4 1. Breathing The movement of air in and out of the lungs. This is an involuntary process controlled by the respiratory center in the brain (medulla oblongata). Chemoreceptors in the blood sense elevated levels of CO 2 and stimulating an increase in breathing rate. Two phases of breathing: Inhalation (Inspiration) The active phase of breathing that draws air into the lungs. It is controlled through the action of the ribs, the intercostal muscles and the diaphragm. The lungs themselves are not muscular, but elastic and respond to the contractions and relaxations of the associated structures. Inhalation begins as the intercostal muscles and the diaphragm contract. This moves the rib cage out and up, diaphragm down, expanding the chest cavity. This causes a decrease in air pressure, creating a vacuum and air rushes into the lungs. Exhalation (Expiration) The passive phase of breathing that forces air out of the lungs. As the intercostal muscles relax and move inward, the diaphragm moves upward creating an increase in pressure which forces air out of the lungs. 2. External Respiration (between air and blood) The exchange of O 2 and CO 2 between the inhaled air and the alveoli of the lungs. Oxygen from the alveoli (region of higher concentration) diffuses to the blood (region of lower concentration) AND at the same time carbon dioxide diffuses out of the blood and into the alveoli (according to the concentration of CO 2

5 5 3. Internal Respiration (between blood and cells) The exchange of O 2 and CO 2 between the blood in the capillaries and the body cells. O 2 diffuses out of the blood and into the cells and CO 2 diffuses out of the body cells and into the bloodstream. 4. Oxygen Transport O 2 is carried by hemoglobin (Hb). This respiratory pigment is a red, iron-containing protein that holds O 2 loosely. O 2 combines with Hb to form HbO (oxyhemoglobin), which is bright red. o 1 hemoglobin molecule can transport 4 oxygen molecules HbO travels to cells, breaks down into Hb and O 2 allowing the O 2 to diffuse into the cells to be used during cellular respiration. CO 2 diffuses out of the cells, into the blood and is carried back to the lungs in three ways; - 70% is carried away in the plasma as an acid (in the form of bicarbonate ions) - 20% combines loosely with Hb to become HbCO 2 (carboxyhemoglobin) and - 10% is dissolved directly into the plasma Composition of Air Air In 21% O 2 16% O 2 79% N 2 79% N % CO % CO 2 Air Out Section 10.3 Respiratory Health Outcomes I can identify how respiratory diseases affect an organism I can predict the impact of environmental factors on an organism The Effects of Smoking Smoking stops the movement of cilia in the respiratory tract for up to 20 minutes (therefore unable to filter) Increases mucus production in response to the foreign particles. When smokers cough, they are trying to rid their body of excess mucus. Cigarette smoke contains carbon monoxide (CO) which prevents O 2 from bonding with Hb, therefore less O 2 reaches the body cells. This leaves smokers chronically short of breathe. When cigarette smoke is inhaled, about 1/3 of the particles remain on the alveoli Smoking can lead to emphysema

6 6 Lung Cancer A disease in which tumors form in the lungs as a result of an uncontrolled cell growth. The carcinoma takes over the healthy tissue and interferes with normal cell activity. Death is usually not caused by difficulty breathing but by the spread of cancer to other regions of the body. Most cases are caused by smoking where substances contained in cigarette smoke irritate the lining of the lungs and cancerous tumors form. Stopping smoking can reduce the risk of cancer as it allows normal cells to take over and replace cancerous cells. Other causes include exposure to radioactive chemicals like radon. Chronic Obstructive Pulmonary Disease (COPD) Irritation of the lungs that can lead to asthma, emphysema, and chronic bronchitis. And, in fact, many people develop two or three of these together. This group is known as COPD. It is caused most often by smoking, and rarely by cystic fibrosis. Asthma A severe allergic reaction that causes wheezing, coughing and breathing difficulty. During an asthma attack, the bronchioles go into spasms, which squeeze the air passages. Some children outgrow this condition Common triggers include: cold and chest infections, exercise and sports, and allergens (pollen, smoke, pollution, mould, pets) Treatments: removal of triggers, medication (anti-inflammatory agents, and bronchodilators) Bronchitis A condition in which the linings of the bronchial tubes become irritated and swollen due to an infection (acute) or an irritant (chronic). Passageways to the alveoli may swell and clog with mucus. Very common in smokers Emphysema A chronic condition in which the lungs lose their elasticity, and the walls of the alveoli become damaged (making the respiratory surface smaller). This results in a shortness of breath. Common in smokers The damage is irreversible Treatments only slow the progression of the disease, and include: eliminating smoking, exercise, drugs to aid with alveoli work, and supplemental oxygen. Pneumonia A condition in which the alveoli become filled with fluid and prevents the exchange of gases in the lungs. Caused by: bacterial infection, viruses, fungi, and some chemicals. Treatment: antibiotics