Anatomy and Physiology Chapter 15: The Respiratory System PDF

Anatomy and Physiology CHAPTER 15 THE RESPIRATORY SYSTEM Divisions Upper Respiratory Tract ◦ Parts outside the chest cavity ◦ Air passages of nose, nasal cavities, pharynx, larynx, and upper trachea Lower Respiratory Tract ◦ Consists of parts within the chest cavity ◦ Lower trachea and l...

Anatomy and Physiology CHAPTER 15 THE RESPIRATORY SYSTEM Divisions Upper Respiratory Tract ◦ Parts outside the chest cavity ◦ Air passages of nose, nasal cavities, pharynx, larynx, and upper trachea Lower Respiratory Tract ◦ Consists of parts within the chest cavity ◦ Lower trachea and lungs, which includes bronchial tubes and alveoli Nose and Nasal Cavities Air enters and leaves the respiratory system through the nose, which is made of bone and cartilage covered with skin. Two nasal cavities separated by the nasal septum. Lined with nasal mucosa, surface area increased by conchae. Air is warmed and humidified Olfactory receptors are in the upper nasal cavities. They detect vaporized chemicals that have been inhaled. Paranasal sinuses are air cavities in the maxillae, frontal, sphenoid, and ethmoid bones. They are lined with ciliated epithelium, and mucus drains into nasal cavities Function of sinuses is to lighten the skull and provide resonance for the voice. Pharnyx Muscular tube posterior to the nasal and oral cavities and anterior to the cervical vertebrae. Uppermost is nasopharynx, which is behind the nasal cavities. The soft palate is elevated during swallowing to block the nasopharynx and prevent food or saliva from going up rather than down. Uvula is part of the soft palate. Posterior wall of the nasopharynx is the adenoid or pharyngeal tonsil. Opening into the nasopharynx are 2 eustachian tubes, which extend to the middle ear cavities. The purpose is to permit air to enter or leave the middle ears, allowing the eardrums to vibrate properly. Nasopharynx is a passageway for air only Oropharynx is behind the mouth. Lateral walls contain palatine tonsils, also lymph nodules. Together with the adenoid and lingual tonsils on the base of the tongue, they form a ring of lymphatic tissue around the pharynx to destroy pathogens that penetrate the mucosa. Food and air passageway Laryngopharynx is a food and air passageway. Opens anteriorly to the larynx and posteriorly into the esophagus. Contraction of the muscular wall of the oropharynx and laryngopharynx is part of the swallowing reflex. Larynx Called the voice box. Thyroid cartilage is the largest. Functions are speaking and air passageway Epiglottis is the between the pharynx uppermost. and trachea. Made of 9 pieces of cartilage connected by ligaments. This prevents collapse to keep air passages open. Vocal cords are on either side of the glottis (the opening between them) Trachea and Bronchial Tree 4-5 inches long extends from the larynx to the primary bronchi. 16-20 C shaped pieces of cartilage, which keep the trachea open. The gaps are posterior, to permit the expansion of the esophagus when food is swallowed. Mucosa is ciliated epithelium with goblet cells. They sweep toward the pharynx. Right and Left primary bronchi are the branches of the trachea that enter the lungs. Within each lung, each primary bronchus branches into secondary bronchi leading to the lobes of each lung (3 right, 2 left) Further branching is called the bronchial tree. The smaller branches of this tree are the bronchioles. The smallest bronchioles terminate in clusters of alveoli, the air sacs of the lungs. Lungs and Pleural Membranes Lungs are located on either side of the heart and are encircled and protected by the rib cage. The base of each lung rests on the diaphragm below; the apex is at the level of the clavicle. Medially, there is an indentation called the hilus, where the primary bronchus and pulmonary artery and veins enter the lung. Serous membranes of the thoracic cavity. ◦ Parietal pleura lines the chest wall ◦ Visceral pleura is on the surface of the lungs. ◦ Between the plural membranes is serous fluid, which prevents friction and keep the two membranes together during breathing. Alveoli Functional units of the lungs are the air sacs alveoli. Simple squamous epithelium. In the spaces between clusters of alveoli is elastic connective tissue, which is important for exhalation. Macrophages Alveoli is surrounded by a capillary network, which permits efficient diffusion of gases. Each alveoli is lined with a thin layer of tissue fluid Pulmonary surfactant mixes with the tissue fluid within the alveoli Mechanism of Breathing Ventilation is the term for the movement of air to and from the alveoli. Inhalation and exhalation are brought about by the nervous system and respiratory muscles. The respiratory centers are located in the medulla and pons. The medulla generates impulses to the respiratory muscles. Respiratory Muscles Diaphragm External intercostal muscles Internal intercostal muscles Atmospheric pressure Intrapleural pressure Intrapulmonic pressure Inhalation Inspiration precise sequence of events that may be described as: Motor impulses from the medulla travel along the phrenic nerves to the diaphragm and along the intercostal nerves to the external intercostal muscles. The diaphragm contracts, moves downward, and expands the chest cavity from top to bottom. The external intercostal muscles pull the ribs up and out, which expands the chest cavity from side to side and front to back. As the chest cavity is expanded, the parietal pleura expands with it. Intrapleural pressure becomes even more negative as a sort of suction is created between the pleural membranes. The adhesion created by the serous fluid permits the visceral pleura to be expanded too, and this expands the visceral pleura to be expanded too, and this expands the lungs as well. As the lungs expand, intrapulmonic pressure falls below atmospheric pressure, and air enters the nose and travels through the respiratory passages to the alveoli. Entry of air continues until intrapulmonic pressure is equal to atmospheric pressure. Exhalation Begins when motor impulses from the medulla decrease, and the diaphragm and external intercostal muscles relax. As the chest cavity becomes smaller, the lungs are compressed, and their elastic connective tissue, which was stretched during inhalation, recoils and also compresses the alveoli. As intrapulmonic pressure rises above atmospheric pressure, air is forced out of the lungs until the two pressures are again equal. Pulmonary Volumes Tidal Volume Minute Respiratory Volume Inspiratory Reserve Expiratory Reserve Vital Capacity Residual Air Exchange of Gases External Respiration Internal Respiration Diffusion of Gases The air in the alveoli has a high PO2 and a low PCO2. The blood in the pulmonary capillaries has a high PCO2 and a low PO2. In external respiration oxygen diffuses from the air in the alveoli to the blood, and CO2 diffuses from the blood to the air in the alveoli. This blood is now circulated to the body. The arterial blood that reaches systemic capillaries has a high PO2 and a low PCO2. The body cells and tissue fluid have a low PO2 and a high PCO2 because cells use oxygen and produce CO2. In internal respiration, oxygen diffuses from the blood to the tissue fluid and CO2 diffuses from te tissue fluid to the blood. This is sent to the heart and lungs for gas exchange. Transport of Gases in the Blood Most oxygen is carried in the blood bonded to hemoglobin in RBCs. The mineral iron is part of hemoglobin and gives this protein its oxygen carrying ability. The bond of oxy-hemoglobin is unstable and when blood passes through tissues with low oxygen is breaks and releases the oxygen. Nervous Regulation Inspiration Center Expiration Center Apneustic Center Pneumotaxic Center Hypothallamus Cerebral Cortex Chemical Regulation Chemoreceptors are located in the carotid and aortic bodies and in the medulla. They detect changes in blood gases and pH. Respiration and Acid-Base Balance The more Hydrogen ions present in the body fluid, the lower the pH The fewer Hydrogen ions present in the body fluid, the high the pH. The respiratory system may be the cause of pH imbalance, or it may help correct a pH imbalance created by some other cause. Respiratory Acidosis Occurs when the rate or efficiency of respiration decreases, permitting carbon dioxide to accumulate in body fluids. This increases the Hydrogen ions in the body fluids. Diseases such as pneumonia and emphysema, or severe asthma. Respiratory Alkalosis Occurs when the rate of respiration increases, and CO2 is rapidly exhaled. Decrease is CO2 is decrease in Hydrogen ion production. Trauma, shock, or mental or emotional anxiety. Respiratory Compensation If the pH imbalance is caused by something other than a change in respiration, it is called metabolic acidosis or alkalosis. The change in pH stimulates a change in respiration that may help restore pH to normal. Metabolic acidosis May be caused by untreated DM, kidney disease, or severe diarrhea. Hydrogen is increased Respiration increases rate and depth of respiration to exhale CO2. This will raise the pH toward normal range. Metabolic Alkalosis Ingestion of excessive amounts of alkaline medications or vomiting excessively. Hydrogen ions are decreased Respiratory compensation involves a decrease in respiration to retain CO2. This will lower pH. At most respiratory compensation is ony about 75% effective. Aging in Respiratory System Smoking is major cause of problems Respiratory muscles weaken with age Lung tissue loses elasticity and alveoli and lost as walls deteriorate Remaining capacity is sufficient for ordinary activities Cilia of respiratory mucosa deteriorate with age, and alveolar macrophages are not as efficient, which makes them more prone to pneumonia Aveolar hypoxia from diseases such as emphysema or chronic bronchitis may lead to pulmonary hypertension, which overworks right ventricle Hypertension overworks left ventricle which leads to CHF and pulmonary edema.