FUNCTIONAL ORGANIZATION OF RESPIRATORY SYSTEM Prof Sultan Ayoub

FUNCTIONAL ORGANIZATION OF RESPIRATORY SYSTEM Prof. Sultan Ayoub Meo MBBS, M. Phil, Ph. D (Pak), M Med Ed (Scotland) FRCP (London), FRCP (Dublin), FRCOP (Glasgow), FRCP (Edinburgh) Professor, Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia

LECTURE OUTLI NES / OBJECTIVES STUDENTS ABLE TO UNDERSTAND: n Structures and functions of the conductive and respiratory zones n Difference between internal and external respiration n Functions of the respiratory system, including non -respiratory functions, like clearance mechanism by mucus and cilia, production of surfactant

RESPIRATORY SYSTEM Upper respiratory tract q Nose q Pharynx and associated structures Lower respiratory tract q Larynx q Trachea q Bronchi q Lungs

RESPIRATORY SYSTEM

FUNCTIONS OF UPPER RESPIRATORY TRACT n n n Passageway for respiration Receptors for smell Filters foreign material Moistens and warms incoming air Resonating chambers for voice

COMPONENTS OF LOWER RESPIRATORY TRACT

COMPONENTS OF LOWER RESPIRATORY TRACT: LARYNX n Functions n n n Maintain an open passageway for air movement Epiglottis and vestibular folds prevent swallowed material from moving into larynx Vocal folds are primary source of sound production

ZONES OF THE RESPIRATORY TRACT

DEAD SPACE Part s of the respiratory tract not participating in gas exchange n Anatomical dead-space: Tracheo-bronchial tree down to respiratory bronchioles. Normally 2 ml/kg or 150 ml in an adult, roughly a third of the tidal volume. n Alveolar Dead Space: Non perfused alveoli n Physiologic Dead Space: Anatomical + Alveolar

TYPES OF RESPIRATORY PROCESS n Breathing (ventilation): Air in to and out of lungs n External respiration: Gas exchange between air in the lungs and blood n Internal respiration: Gas exchange between blood and body cells /tissues n Cellular respiration: Oxygen use to produce ATP, carbon dioxide as waste. Cellular respiration of glucose is carried out in three stages. 1. Glycolysis, 2. Oxidation of pyruvate, 3. citric acid cycle

TYPES OF RESPIRATORY PROCESS The term cellular respiration refers to the biochemical pathway by which cells release energy from food molecules and provide that energy for essential processes of life. Living cells must carry out cellular respiration. Prokaryotic (Single-celled organisms like bacteria) carry out cellular respiration within the cytoplasm or on the inner surfaces of the cells. Eukaryotic cells (Multi cellular animals including humans) are made up of complex cells with multiple internal organelles. Mitochondria are the site of the reactions. Energy of cells is ATP.

GENERAL FUNCTIONS OF RESPIRATORY SYSTEM n Gas exchange: Oxygen enters into the blood and carbon dioxide leaves n Regulation of blood p. H: Altered by changing blood carbon dioxide levels n Voice production: Movement of air support the vocal folds to make sound and speech n Olfaction: Smell sensation when airborne molecules drawn into nasal cavity n Protection: Against microorganisms by preventing entry and removing them via cough and sneez reflex

GENERAL FUNCTIONS RESPIRATORY SYSTEM OF Dust particles with an aerodynamic diameter of 10 m= nose and pharynx. 2 -10 m=tracheo-bronchial tree 0. 1 -2 m within the alveoli. Particles smaller then 0. 1 m remain in the air stream and are exhaled. Sheppard et al. , 1999 Occup Med, 1991

GENERAL FUNCTIONS OF RESPIRATORY SYSTEM: COUGH REFLEX q The larynx and carina are very sensitive to dust particles q Terminal bronchioles and even the alveoli are also sensitive to chemical such as sulfur dioxide or chlorine gas. q Air expelled at velocities ranging from 75 to 100 miles / hour [Guyton] q 965 Km (600 miles / hour [Ganong]

GENERAL FUNCTIONS OF RESPIRATORY SYSTEM: CILIARY FUNCTION Bronchus in the lungs are lined with hair-like projections called cilia that move microbes and debris up and out of the airways. Scattered throughout the cilia are goblet cells that secrete mucus which helps protect the lining of the bronchus microorganisms and trap

GENERAL FUNCTIONS OF RESPIRATORY SYSTEM: CILIARY FUNCTION q Each liter of air may contain several million particles of dust. q Cilia beat at a frequency of 1000– 1500 cycles / min q Cilia move particles away from lungs at a rate of 16 mm/min q Particles less 0. 1 -2 m in diameter reach the alveoli, where they are ingested by the macrophages.

GENERAL FUNCTIONS OF RESPIRATORY SYSTEM: CILIARY FUNCTION Defective ciliary motility leads to q Chronic sinusitis q Recurrent lung infections q Bronchiectasis. q Ciliary immotility may produced by air pollutants, or congenital disorders such as Kartagener's syndrome q Patients with this condition also infertile because they lack motile sperm

SURFACTANT q Surfactant is secreted by type II alveolar epethelial cells. q These cells comprise 10% of surface area of the alveoli. Surfactant is a surface active agent, decreases surface tension. q Composition of surfactant: Surfactant is the complex mixture of several phospholipids, proteins, and ions. The important components of which are phospholipids, dipalmitoyl lecithin, surfactant apoproteins, and calcium ions. Type II alveolar epithelial cells start to from the surfactant during 6 th to 7 th month of intrauterine life. Component % Composition Phosphatidyl choline 62 Phosphatidyl glycine 05 Other phospholipids 10 Neutral lipids 13 Proteins 08 Carbohydrates 02

FUNCTIONS OF SURFACTANT q Surfactant decreases the surface tension q Important for survival of premature infants q When insufficient amount of surfactant is present, the air and water (blood) surface tension becomes high and alveoli will collapse during expiration. This is called Respiratory Distress Syndrome [RDS] common cause of death in the premature infants q This disease is therefore also known as hyaline membrane disease q It has been suggested that surfactant have a bactericidal effect q Factors increasing surfactant formation: q Thyroxine and Glucocorticoids.

THANK YOU College of Medicine, King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia