Respiratory System-Respiratory-2023 PDF

Assoc. Prof. Özlem Tuğçe Çilingir-Kaya Marmara University School of Medicine Histology & Embryology Department 1. Respiratory bronchioles 2. Alveolar ducts 3. Alveolar sacs 4. Alveoli  The first region of the RS where exchange of gases can occur.  Each respiratory bronchiole terminates...

Assoc. Prof. Özlem Tuğçe Çilingir-Kaya Marmara University School of Medicine Histology & Embryology Department 1. Respiratory bronchioles 2. Alveolar ducts 3. Alveolar sacs 4. Alveoli  The first region of the RS where exchange of gases can occur.  Each respiratory bronchiole terminates in an alveolar duct  Their wall is interrupted by the presence of thin-walled, pouch-like structures = alveoli  Gaseous exchange (O2 for CO2) can occur.  As respiratory bronchioles branch, they become narrower in diameter and their population of alveoli increases.  Alveolar ducts arises from a respiratory bronchiole branches.  Do not have walls of their own; they are merely linear arrangements of alveoli.  Each of the resultant alveolar ducts usually ends as a blind outpouching, composed of two or more small clusters of alveoli,  Each cluster is known as an alveolar sac.  These alveolar sacs open into a common space = The atrium  Alveoli are small air sacs composed of  highly attenuated type I pneumocytes and  larger type II pneumocytes.  Their thin walls permit exchange of CO2 for O2 between the air in their lumina and blood in adjacent capillaries.  Form the primary structural and functional unit of the RS.  There are numeorus alveoli  Frequently pressed against each other  Eliminating the CT interstitium between them  In such areas of contact, the air spaces of the two alveoli may communicate with each other through an alveolar pore = pore of Kohn  The diameter varies from 8 to 60 μm.  Lined on both sides by alveolar epithelium.  The IS may be extremely narrow, housing only a continuous capillary and its basal lamina, or  It may be somewhat wider, including CT elements, such as  type III collagen  elastic fibers,  macrophages (m),  fibroblasts (and myofibroblasts),  mast cells  lymphoid elements  The IS reinforces the alveolar duct and stabilizes it.  Alveoli and capillaries are composed of epithelial cells.  They have a prominent basal lamina.  The openings of alveoli are associated with alveolar sacs.  Unlike those of respiratory bronchioles and alveolar ducts, they are devoid of smooth muscle cells.  Instead, their orifices are circumscribed by elastic and, especially, reticular fibers.  The walls of alveoli are composed of two types of cells: 1. Type I pneumocytes 2. Type II pneumocytes  question will be tyoe and 2 comparasin  ~95% of the alveolar surface is composed of simple squamous epithelium,  Known as type I pneumocytes = type I alveolar cells = squamous alveolar cells  It houses much of the cell’s organelle population.  Type I pneumocytes form occluding junctions with each other,  Preventing the seepage of extracellular fluid (tissue fluid) into the alveolar lumen.  The adluminal aspect is covered by a well-developed basal lamina  The luminal aspect is lined by surfactant  Although type II pneumocytes (= great alveolar cells = septal cells = type II alveolar cells) are more numerous than type I pneumocytes, they occupy only about 5% of the alveolar surface.  Their dome-shaped apical surface juts into the lumen of the alveolus.  The most distinguishing feature is the presence of membrane- bound lamellar bodies that contain pulmonary surfactant.  Synthesized on the RER and modified in the Golgi apparatus. Fatal Respiratory Distress Syndrome  Monocytes gain access to the pulmonary interstitium  Become alveolar macrophages  migrate between type I pneumocytes  enter the lumen of the alveolus.  They phagocytose particulate matter in the lumen of the alveolus as well as in the interalveolar spaces.  Also assist type II pneumocytes in the uptake of surfactant.  incsered lung complince  The patients with emphysema, elasticity of the lung tissue is reduced and large, fluid-filled sacs are present that decrease the gas- exchange capability of the respiratory portion of the RS.  The thinnest region of the interalveolar septum that is traversed by O2 and CO2 as these gases go from the lumen of the blood vessel to the lumen of the alveolus.  The narrowest barrier regions are composed of the following structures: 1. Surfactant and type I pneumocytes 2. Fused basal laminae of type I pneumocytes and endothelial cells of the capillary 3. Endothelial cells of the continuous capillary  In the lungs,  O2 is exchanged for CO2 carried by blood;  in the tissues of the body, CO2 is exchanged for O2 carried by blood.  The passage of O2 and CO2 across the blood-gas barrier is due to passive diffusion in response to the partial pressures of these gases within the blood and alveolar lumina.  The thoracic cage is separated into three regions: 1. The left thoracic cavity 2. The right thoracic cavities 3. The centrally located mediastinum. have differnt origind  Each thoracic cavity is lined by a serous membrane = the pleura  simple squamous epithelium  subserous CT 1. The visceral pleura, covers and adheres to the lung, 2. The parietal pleura, lines and adheres to the walls of the thoracic cavity.  The space between the visceral and parietal pleura  The pleural cavity  A slight amount of serous fluid permits a nearly frictionless movement of the lungs during ventilation 1.Movement of air in and out of the lungs (breathing or ventilation) 2.Exchange of O2 in the inspired air for CO2 in the blood (external respiration)  Occur within the confines of the respiratory system 3.Conveyance of O2 and CO2 to and from the cells (transport of gases)  Performed by the circulatory system 4.Exchange of CO2 for O2 in the vicinity of the cells (internal respiration)  Occurs in the tissues throughout the body  Inhalation is an energy-requiring process because it involves the contraction of the diaphragm, intercostal, and scalenus muscles, as well as accessory respiratory muscles.  For exhalation to occur, the respiratory (and accessory respiratory) muscles relax, decreasing the volume of the pleural cavities, with a consequent increase in the pressure within the pleural cavities.  In persons afflicted with poliomyelitis, the muscles of respiration may become so weakened that the accessory muscles hypertrophy because they become responsible for the elevation of the thoracic cage.  In myasthenia gravis and Guillain-Barré syndrome, the weakness of the respiratory and accessory respiratory muscles may lead to respiratory failure and consequent death even though the lungs function normally.  Each lung has a medial indentation  The hilum  The primary bronchi, bronchiolar arteries, and pulmonary arteries enter and  The bronchiolar veins, pulmonary veins, and lymph vessels leave the lung.  This group of vessels and the airway that enter the hilum make up the root of the lung.  Each lobe is subdivided into several bronchopulmonary segments supplied by a tertiary intrapulmonary (segmental) bronchus.  In turn, bronchopulmonary segments are subdivided into many lobules, each served by a bronchiole. Pulmonary arteries and veins Bronchial arteries and veins  Arise from the right ventricle  Arise from the systemic and drain into the left atrium circulation  Supply deoxygenated blood to  Carry oxygenated blood and the lungs from the right side of travel in the septa between the heart lobules of the lung  Involved gas exchange  High-pressure system  Low-pressure system  Parasympathetic, preganglionic fibers descend into the vagus and terminate in the ganglia. The ganglia contain excitatory neurons that are cholinergic and inhibitory neurons that are nonadrenergic. Other neurons with an integrative function are probably also present. Glial cells (G) are present in the ganglia. Postganglionic fibers to the smooth muscle are excitatory (e) or inhibitory (i).  Normally, the smooth muscle coats contract at the end of expiration and relax during inspiration.  In asthma, however, the smooth muscle coat undergoes prolonged contraction during expiration; thus, these individuals have difficulty expelling air from their lungs.  Steroids and β2-agonists relax bronchiolar smooth muscle and are frequently used to relieve asthmatic attacks.