L1 Physiology Functions of Respiratory system PDF

 Semester 3 Module (Respiratory)  INSTRUCTOR INFORMATION Prof. Ahmed Abdalfattah Physiology department  Respiration Respiration refers to the process involved in the supply of the tissue cells with oxygen and elimination of CO2 O2 consumption in young adult is 250 ml/...

 Semester 3 Module (Respiratory)  INSTRUCTOR INFORMATION Prof. Ahmed Abdalfattah Physiology department  Respiration Respiration refers to the process involved in the supply of the tissue cells with oxygen and elimination of CO2 O2 consumption in young adult is 250 ml/minute. CO2 production is about 200 ml/minute.  Respiration The term is generally used, includes 3 processes: External respiration, the absorption of O2 and removal of CO2 from the body as a whole. Transport of O2 and CO2 Internal respiration, the utilization of O2 and production of CO2 by cells and the gaseous exchanges between the cells and their fluid medium  External (pulmonary) respiration Uptake of O2 and excretion of CO2 and includes 2 processes: Pulmonary ventilation: – Respiratory rate 12-16 per minute – Infants and neonates 40 per minute – Respiratory cycle Inspiration, expiration and expiratory pause Pulmonary gas exchange: O2 diffusion from alveolar air to pulmonary capillaries and CO2 in the opposite direction  The Respiratory System It consists of: 1. The respiratory tract (airways or passages) 2. The thoracic cage and respiratory muscles 3. The nerve centers that control respiration  Respiratory unit Respiratory unit starts from the respiratory bronchioles. Each respiratory bronchiole divides into alveolar ducts. Each alveolar duct enters an enlarged structure called the alveolar sac. Space inside the alveolar sac is called antrum. Alveolar sac consists of a cluster of alveoli. Few alveoli are present in the wall of alveolar duct also. Thus, respiratory unit includes: 1. Respiratory bronchioles 2. Alveolar ducts 3. Alveolar sacs 4. Antrum 5. Alveoli. Each alveolus is like a pouch with the diameter of about 0.2 to 0.5 mm. It is lined by epithelial cells. Respiratory unit  Structure of respiratory system Structures or zones 1. Conducting zone 2. Transition zone 3. Respiratory zone After passing through the nasal passages and pharynx, the inspired air passes down the trachea and through the bronchioles, respiratory bronchioles, and alveolar ducts to the alveoli Between the trachea and the alveolar sacs, the airways divide (20 -25 ) average 23 times. The first 16 generations of passages form the conducting zone of the airways that transports gas from and to the exterior. They are made up of bronchi, bronchioles, and terminal bronchioles. The remaining seven generations form the transitional and respiratory zones where gas exchange occurs and are made up of respiratory bronchioles, alveolar ducts, and alveoli.  Respiratory zone or exchange airway Alveolie 300 million alveolie total surface area 70m2 The alveoli are lined by two types of epithelial cells Type I cells which are one layer of flat epithelium allow exchange of gases Type II cells or pneumocytes secret surfactant These division increase the total cross section of air way up to 2000 times.The velocity of air flow Deceased to very low values Respiratory Zone  Alveoli The alveoli are surrounded by pulmonary capillaries. In most areas, air and blood are separated only by the alveolar epithelium and the capillary endothelium, so they are about 0.5 m apart. Humans have 300 million alveoli, and the total area of the alveolar walls in contact with capillaries in both lungs is about 70-80 m2. The alveoli are lined by two types of epithelial cells : Type I cells are flat cells with large cytoplasmic extensions and are the primary lining cells. Type II cells (granular pneumocytes) are thicker and contain numerous lamellar inclusion bodies. These cells secrete surfactant. Other special types of epithelial cells may be present, and the lungs also contain pulmonary alveolar macrophages (PAMs), lymphocytes, plasma cells, APUD cells and mast cells. The mast cells contain heparin, various lipids, histamine, and various proteases that participate in allergic reactions.  Respiratoty functions A.Primary functions 1-Provide oxygen for metabolism of the tissues 2-Remove carbon dioxide, the waste product of metabolism.  NON-RESPIRATORY FUNCTIONS OF RESPIRATORY TRACT 1. OLFACTION Olfactory receptors present in the mucous membrane of nostril are responsible for olfactory sensation. 2. VOCALIZATION Larynx forms the speech apparatus. However, larynx alone plays major role in the process of vocalization. Therefore, it is called sound box.  3. PREVENTION OF DUST PARTICLES Dust particles, which enter the nostrils from air, are prevented from reaching the lungs by filtration action of the hairs in nasal mucous membrane. Small particles, by nasal mucous membrane. Those dust particles, which escape nasal hairs and nasal mucous membrane, are removed by the phagocytic action of macrophages in the alveoli. Particles, which escape the protective mechanisms in nose and alveoli are thrown out by cough reflex and sneezing reflex  4. DEFENSE MECHANISM By the presence of various types of cells in mucous membrane lining the alveoli of lungs. These cells are leukocytes, macrophages, mast cells, natural killer cells and dendritic cells. 5. MAINTENANCE OF WATER BALANCE Respiratory tract plays a role in water loss mechanism. During expiration, water evaporates through the expired air  6. REGULATION OF BODY TEMPERATURE During expiration, along with water, heat is also lost from the body. Thus, respiratory tract plays a role in heat loss mechanism.  7. REGULATION OF ACID-BASE BALANCE Lungs play a role in maintenance of acid-base balance of the body by regulating the carbon dioxide content in blood. Carbon dioxide is produced during various metabolic reactions in the tissues of the body. When it enters the blood, carbon dioxide combines with water to form carbonic acid. Since carbonic acid is unstable, it splits into hydrogen and bicarbonate ions  Entire reaction is reversed in lungs when carbon dioxide is removed from blood into the alveoli of lungs Increased metabolic activity…….more CO2 production ……acidosis……+++ of respiration  Other functions Breathing movements help venous retun and lymph flow The venous blood is filtered by the pulmonay capillaries so no emboli Metabolic &Endocrine function: Type II pneumocytes secrete surfactant Remove serotonin, ….. Secretion of heparin from the mast cells Secretion of ACE Enzyme B.Secondery functions 1- facilitate sense of smell. 2- Produce speech. 3- It has a role in acid base balance 4- It has a role in maintaining body water level. 5- It has a role in maintaining heat balance (body temperature regulation) 6- Protect the body from inhaled pathogens and irritating substances. Metabolic and Endocrine Functions Type II alveolar cells secrete surfactant The lungs remove certain substances from the blood as serotonin, bradykinin, acetyl choline, norepinephrine. Secretion off Heparin from mast cells Angiotensin I is converted into Ang II by ACE Fibrinolysis Secretion of VIP which causes relaxation of the bronchial tree Respiratory System