Unit – L Respiratory System

Respiratory Structures 1. Nasal Cavity --Air is warmed, filtered, and moistened 2. Pharynx -- Back of throat -- Common passage for air and food 3. Glottis -- Top of larynx -- Upper part of windpipe -- Covered by epiglottis when swallowing food

4. Larynx -- Voice box, which contains the vocal cords -- The Adam’s Apple 5. Vocal Cords -- Vibrate, as air is forced past, producing sound. 6. Trachea -- Windpipe -- Made of rings of cartilage to prevent collapsing -- Cilia: move debris

7. Bronchi -- Branches of the trachea -- One to each lung -- Bronchus; singular 8. Bronchioles -- Smaller branches of the bronchi -- No cartilage for support 9. Alveoli -- Rounded end of very small bronchioles -- Area where gas exchange occurs

10. Pleural Membranes -- Covers the surface of the lungs -- Double membrane -- Allows the surface of the lungs to slide over the body wall easily. -- Seal off thoracic cavity 11. Thoracic Cavity -- Chest cavity -- From diaphragm to throat

12. Diaphragm -- Horizontal muscle -- Separates the thoracic cavity with the abdominal cavity 13. Ribs -- Protects internal organs -- When ribs contact with the intercostal muscles, they rise and increase volume in the thoracic cavity.

Air Passageways: Filters, Warms, Moistens Several things happen to the air on its journey into the alveoli: 1. Cleansed of debris. This is a two-part process: a. The initial cleaning is by the nose hairs and mucous in the nasal Passageways.

b.The second is the process that occurs further along where the accumulation of debris can no longer get out of through the nose. This is the role of the mucous lining and the cilia along the trachea and the bronchi. Pretty well any material other than the gases of the inhaled air will get caught in the mucous. The cilia are in constant motion beating the debris- laden mucous upward towards the pharynx. When this material is detected at the back of the mouth, it is swallowed (or coughed up and spit out). Note: Cilia do not filter. vv

2. Adjusted to body temperature. The more contact it has with moist tissues that are 37  C the closer the temperature of the inhaled air get to 37  C. By the time air gets to the alveoli, there will be no difference in its temperature than that of the surrounding tissues.

3. Adjusted to 100% humidity. The air in the lungs is saturated with water. One of the things that happens to inhaled air is that it, too, becomes saturated with water. This is an obvious outcome of having passed over the mucous lined passageways.

Specializations of Alveoli

1. They are very numerous. Up to 300 million alveoli in the human lung. This provides a great surface area for diffusion. 2. They are very thin-walled. Alveolar walls are only one cell thick. This aids in diffusion.

3. The alveoli have a coating of lipoprotein on their inner surface. This helps to maintain surface tension thus preventing them from collapsing and sticking together during exhalation. 4. They are supplied with stretch receptors. These are nerve endings that are sensitive to stretch. During inhalation, these signal when the alveoli are full enough (stretched). This marks the onset of exhalation.

5. The alveoli surfaces have a very rich blood supply from the pulmonary capillaries to ensure maximum diffusion. They are highly vascularized. 6. Made up of Squamous (flat) Epithilial cells.

Three things that make the lungs very efficient at gas exchange 1. Huge surface area 2. Only 2 cell layers separate air in lungs from the blood 3. Moist

Processes of the Respiratory System The Respiratory System supplies the body with oxygen for its energy production. Without Oxygen, the body shuts down in minutes. The Respiratory System works closely with the Circulatory System.

Four Processes make up the Respiratory System. A. Breathing – Inspiration – Bringing Oxygen into the lungs – Expiration – Expelling Carbon Dioxide B. External Respiration -- Exchange of gases between blood and the lungs

C. Internal Respiration -- Exchange of gases between blood and the body tissues D. Cellular Respiration -- Production of ATP energy within the cells.

Pleural Membranes -- 2 sets of membranes a. one joined to the lung b. one joined to the ribs and diaphragm -- The two sets are close together separated by a slight amount of fluid. (vacuum is created) -- If the membranes are punctured, air enters the intrapleural space, destroying the vacuum. The lung collapses. -- They maintain an interpleural pressure that is less than atmospheric pressure; keeping the lungs open.

Mechanics of Breathing: Inhalation and Exhalation The chest cavity is dome-shaped. The top and sides are surrounded by the ribs. The bottom is made up by the diaphragm. It is a closed system.

Inhalation xx 1. CO 2 concentration and H + concentration are the PRIMARY STIMULI that cause us to breathe. When Carbon Dioxide and/or Hydrogen ion concentration gets too high, the Breathing center in the Medulla Oblongata is stimulated. 2. A nerve impulse is sent from the Medulla Oblongata to the diaphragm and rib cage.

3. The diaphragm contracts and lowers; the rib muscles contract (intercostal muscles) and raise the ribs. These actions increase the size of the chest cavity. Increase volume, decreases pressure. 4. A partial vacuum is created in the lungs (air pressure in the lungs is reduced).

5. Air Rushes into the lungs from outside in order to rebalance the pressure. This is the process of inspiration. ***NOTE: Air comes in because the lungs have already opened. The air does not force the lungs open. This is why it is said that we breathe by Negative Pressure. (Low pressure sucks the air into our lungs) ******NOTE: The lungs themselves have no muscles****

Exhalation: 1. When the lungs are full, stretch receptors in the alveoli are stimulated 2. The Medulla Oblongata is notified and stops sending messages. 3. The diaphragm and rib muscles relax. 4. The chest cavity gets smaller. Decreasing volume, which increases the pressure in the lungs. Air is forced out.

In addition to the Respiratory Center in the Medulla Oblongata, there are other receptors that can respond to stimuli: a. Carotid bodies – in the carotid artery b. Aortic bodies – in the aorta These respond to high concentration of Hydrogen Ions but can also respond to levels of carbon dioxide in the blood.

Gas Exchange When carbon dioxide diffuses from the cells into the blood, only a small amount of it (9%) reaching the blood is held in simple solution. (as dissolved carbon dioxide) Another 27 % attaches directly to the Hemoglobin to form carbonamino-hemoglobin. The remaining 64% combines with water to form bicarbonate ions and hydrogen ions.

Each time blood passes through the tissues it picks up large quantities of carbon dioxide. This then reacts with water to form Bicarbonate (HCO 3 - ) and Hydrogen Ions (H + ). There are many substances in the blood capable of binding the excess free hydrogen ions. Hemoglobin is one of the most important of these substances. When Hydrogen (H + ) combines with the hemoglobin (Hb), the Hb releases some of the oxygen attached to it.

Gas Exchange in Tissues Internal Respiration

1. CO 2 diffuses into the blood from the cell 2. CO 2 joins with water to make Bicarbonate and Hydrogen Ions. (Carbonic Anahydrase) – Enzyme that runs this reaction 3. Most of the released H + is picked up by the combined from of O 2 and hemoglobin. (Oxyhemoglobin [HbO 2 ]. The binding of H + by HbO 2 (produces HHb) aids in the release of oxygen. The H + concentration and the slight increase in temperature alter the hemoglobin (protein denatures slightly) and releases oxygen easily.

4.Oxygen then enters the tissue moving from an area of high concentration to areas of low concentration. The blood leaving the tissues now contains large quantities of hemoglobin which is free of oxygen, and is called Reduced Hemoglobin (HHb) The blood also contains large amounts of bicarbonate ions (HCO 3 - ). No further changes occur until the blood reaches the lungs.

Gas Exchange in the Lungs External Respiration

1.High concentration of Oxygen in lungs. Oxygen diffuses into blood. 2. Oxygen joins with reduced hemoglobin to form Oxyhemoglobin and Hydrogen ions. 3. H + picked up by Bicarbonate to produce CO 2 + H 2 O 4. The CO 2 diffuses into lung alveoli where it is expelled by normal breathing.

***NOTE: H + does not accumulate because as soon as it is released from HHB, it combines with HCO 3 - to release Carbon dioxide. Hemoglobin is essential in the blood because it serves as a carrier for oxygen, carbon dioxide, and hydrogen ions (acts like a buffer).*** Temperature is cooler which allows hemoglobin to grab oxygen easier.