RESPIRATION Dr. Zainab H.H Dept. of Physiology Lec.1,2

“Roses are red, Violets are blue, Without your lungs Your blood would be, too.” David D. Ralph, MD New England Journal of Medicine

objectives Describe the mechanism of respiration List the non respiratory functions of the lung Describe the basic structures of the lung

Respiratory System Made up of: 1. Gas exchanging organ – Lungs 2. Pump that ventilates the lungs – consists of:  Chest wall  Respiratory Muscles – increase and decrease the size of the thoracic cavity  Areas in the Brain – control the muscles  Tracts and Nerves – connect the brain to the muscles

Basics Of Respiration  A process involving:  Taking up of Oxygen from the air.  Utilizing the Oxygen in the tissues.  Removal of the Carbon dioxide formed. O2O2 Tissues: Use of O 2 Removal Of CO 2

Respiration  The term respiration includes 3 separate functions: 1. Ventilation: I. Breathing. 2. Gas exchange: I. Between air and capillaries in the lungs. II. Between systemic capillaries and tissues of the body. 3. O 2 utilization: I. Cellular respiration.

External Respiration 1) Inspiration: The process of taking in of air (O 2 ) from the external environment. 2) Expiration: Giving out of air (CO 2 ) from the body to the external environment. 3) Exchange of gases between the body and the external environment.

Internal Respiration 1) Tissue or Cell level Respiration. 2) Oxygen is utilized by tissues for the metabolism of organic molecules. Oxygen Carbon Dioxide TISSUES

Ventilation Cellular Respiration Gas exchange

Non Respiratory Functions Of Lungs I. Defense & Protection: 1. Warms & humidifies the air. 2. Dust particles are trapped by the Bronchial secretions. 3. The Ciliary Escalator removes trapped matter by expectoration(Cough) 4. Secretory Ig.A provides Immunity against airborne microbes. 5. Pulmonary Alveolar Macrophages(PAMs) engulf foreign bodies by Phagocytosis.

Non Respiratory Functions Of Lungs II. Metabolism & Other functions: 1. Regulation of blood pH. 2. Synthesis of proteins, Fats & Carbohydrates. 3. Fibrinolysis & removal of blood clots. 4. Phonation or Speech.

Non Respiratory Functions Of Lungs 5. Removal of vasoactive local hormones.(Bradykinin, PGE, E 2 etc.) 6. ACE (from Pulmonary Capillary endothelium) converts Angiotensin I into Angiotensin II. 7. Destruction of Thrombocytes. 8. Maintaining Body Water balance 9. Thermoregulation.

Functional division of Respiratory System 1) Conducting zone - All the structures air passes through before reaching the respiratory zone. 2) Respiratory zone - Region of gas exchange between air and blood.  Includes terminal respiratory bronchioles and alveolar sacs.

Thoracic Cavity  Diaphragm:  Sheets of striated muscle divides anterior body cavity into 2 parts. 1) Above diaphragm: thoracic cavity:  Contains heart, large blood vessels, trachea, esophagus, thymus, and lungs. 2) Below diaphragm: abdominopelvic cavity:  Contains liver, pancreas, GI tract, spleen, and genitourinary tract.

Thoracic Cavity  Structures in the central region “mediastinum” enveloped by two layers of pleural membranes. 1. Parietal (superficial) – lines the inside of thoracic wall. 2. Visceral (deep) – covers lung surface  The visceral pushed against parietal pleura  Under normal condition – little or no air  There is potential space “intrapleural space = pleural cavity”

Pleural Cavity  Filled with fluid produced by the pleural membranes.  It does 2 things: A. Act as lubricants – parietal and visceral pleural past each other B. Helps hold parietal and visceral pleural membrane together

Muscles Of Respiration For Inspiration 1. Diaphragm – 75% 2. External intercostals 3. Sternocleidomastoid 4. Serratus (anterior) 5. Scaleni For Expiration 1. Internal intercostals 2. Abdominal recti

Physical aspects of Ventilation  Ventilation - mechanical process that moves air in and out of the lungs.  Pressure difference induced by change in lung volumes  Air move from high to low pressure between conducting zone & terminal bronchioles

Quiet Inspiration  Active process:  Contraction of diaphragm, increases thoracic volume vertically.  Contraction of parasternal and external intercostals, raising the ribs; increasing thoracic volume laterally.  Pressure changes:  Alveolar changes from 0 to –3 mm Hg.  Intrapleural changes from –4 to –6 mm Hg.  Transpulmonary pressure = +3 mm Hg.

Expiration  Passive process.  The diaphragm, thoracic muscles, thorax, and lungs recoil.  Pressure changes:  Intrapulmonary pressure changes from –3 to +3 mm Hg.  Intrapleural pressure changes from –6 to –3 mm Hg.  Transpulmonary pressure = +6 mm Hg.

The air we breathe!  Definitions  Atmospheric Air: Air at the normal sea level.  Alveolar Air: The inspired air which has reached the alveoli. (Before the exchange of gases)  Expired Air: The air which is exhaled after the exchange process.

Atmosphere  The air that envelopes the Planet earth.  The air that we normally live in.  Has a pressure of 1 Atmosphere or 760mm of Hg.

Boyle’s Law  Gas pressure in closed container is inversely proportional to volume of container  Changes in lung volume changes in intrapulmonary pressure.  Increase in lung volume decreases intrapulmonary pressure.  Air goes in.  Decrease in lung volume, raises intrapulmonary pressure above atmosphere.  Air goes out.

Atmospheric & Intrapulmonary Pressures  During inspiration – air enters the lungs (atmospheric pressure > intrapulmonary “intrapleural” pressure)  Quiete inspiration – intrapulmonary pressure 3 mmHg sub atmospheric.  During expiration – air goes out of the lung (intrapulmonary “intrapleural” pressure > atmospheric pressure)  Quiete expiration - intrapulmonary pressure 3 mmHg greater than atmospheric pressure.

Intrapleural Pressure  Pressure in the intrapleural space.  It is negative, due to lack of air in the intrapleural space.  More negative during inspiration – expansion of thoracic cavity  It is normally lower than intrapulmonary pressure during both inspiration and expiration

Intrapleural Pressure  During inspiration, the intrapleural pressure falls further for two reasons: 1. as the lung expands, the elastic recoil increases. This increases the pull on the lung away from the chest wall, dropping the intrapleural pressure further. 2. the fall in the alveolar pressure is transmitted to the intrapleural space, increasing the pressure drop  During expiration, the intrapleural pressure returns to its resting level

Transpulmonary “transmural” Pressure  The pressure across the lung wall.  It is the difference between intrapulmonary and intrapleural pressure.  It keeps the lung against chest wall  Change in lung volume parallel changes in thoracic volume during inspiration & expiration.

The Alveoli  Air sacs - Honeycomb-like clusters  ~ 300 million in the two lungs  mm in diameter  Large surface area (60–80 m 2 ) for diffusion.  Each alveolus: only 1 thin cell layer “air- blood barrier = 0.3µm = 1/100 th hair width”.  Total air barrier is 2 cells across (2  m) (alveolar cell and capillary endothelial cell).

The Alveolar Cells  alveoli are lined by two types of epithelial cells 1) Type I pneumocytes  structural cells.  Thin squamous epithelial cells  95-97% (gas exchange) 2) Type II granular pneumocytes  Round or cup-like secretary cells  Secrete pulmonary surfactant  Reabsorb Na + and H 2 O “prevent buildup of fluid within alveoli”

The Alveolar Cells  The alveoli contain pulmonary alveolar macrophages (PAMs)

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