BIO 251 1st Edition Lecture 18 Outline of Last Lecture I Components of blood II Plasma a Compositions III Erythrocytes a Structure function IV Hematocrit V Leukocytes a Basics VI Platelets a Structure b Function VII Hemostasis a 3 steps i Vascular spasms ii Platelet aggregation iii Coagulation VIII Flow rate of blood IX Blood pressure These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Outline of Current Lecture I Overview of respiration II Structure of respiration III Respiratory cycle IV Airway resistance V Volume capacity ventilation VI Control of respiration Current Lecture Overview of Respiration 16 1 o External regulation Entire sequence of events involved in exchanges of O2 CO2 between the external environment and cells of the body Ventilation Air exchange between environment lung air sacs O2 CO2 exchanged between alveoli blood O2 CO2 are transported by blood between lungs tissue Exchange of O2 CO2 between blood tissues across capillaries o Internal respiration Intracellular metabolic processes which use O2 produce CO2 and derive energy from nutrient molecules Route for water loss heat elimination Exchanges venous return Helps maintain acid base balance Enables vocalization Defends against inhaled pathogens Removes modifies materials passing through pulmonary circulation Structure of respiratory system o Airways Tubes that carry air between environment alveoli 16 2 16 5 Nasal passages Pharynx throat Trachea windpipe Fairly rigid structure made of cartilage Larynx voice box at entrance to trachea Trachea splits into right left bronchi which enter right left lung bronchi are fairly rigid made of cartilage Bronchi branch into bronchioles smooth muscle instead of cartilage flexible o Alveoli Location of gas exchange with blood 16 5 Clusters of thin walled inflatable grapevine sacs at the terminal branches of the bronchioles Walls consist of single layer of Type I aveolar cells Type II alveolar cells secrete pulmonary surfactant which reduces surface tension in alveoli keeps lungs from collapsing Surrounded by pulmonary capillaries 16 5 NOTE thinness of walls of each alvelus and huge surface area of all alveoli greatly facilitates diffusion of gasses o Lungs and chest cavity 16 7 2 lungs each supplied by one of bronchi Lungs composed of bronchi bronchioles and alveoli plus lots of elastic CT Lungs are smaller than thoracic cavity but occupy most of it 2 factors keeps lungs close to thoracic wall 16 8 Intrapleural fluid is sticky water on glass together Allows movement of lungs along chest wall but keeps lungs stuck to chest wall Intrapleural pressure is 756 mm Hg and the intra alveolar pressure is 760 mm Hg when equlibriated with atmospheric pressure Transmural pressure gradient across lung wall is crucial in expanding the lung to fill chest cavity 16 8 9 Rib cage provides bony protection for lungs heart Diaphragm forms floor of chest cavity Respiratory Cycle 16 11 16 3 o Pressure considerations Air moves from region of high pressure to low pressure Flows down a pressure gradient Air flows in and out of the lungs by reversing pressure gradients between lungs environment Important pressures related to respiratory Atmospheric pressure Pressure exerted by weight of air in atmosphere on objects on earth s surfaces at sea level it is 760 mm Hg Intra alveolar pressure Pressure within the alveoli Whenever intra alveolar pressure does not equal atmospheric pressure Air will move down its pressure gradient until intraalveolar pressure equals atmospheric pressure Intrapleural pressure Pressure exerted outside the lungs within the thoracic cavity Usually just less than intra alveolar pressure atmospheric pressure avging about 756 mm Hg b c thoracic cavity is closed to the outside air can not move down pressure gradient into thoracic cavity o Respiration works by changing the volume of the chest cavity which changes the volume of the lungs which changes the pressure in the lungs then air moves along its pressure gradient o Before start of inspiration respiratory muscles are relaxed intra alveolar pressure atmospheric pressure and no air is flowing o Onset of inspiration inspiratory muscles contract which results in enlargement of thoracic cavity o As thoracic cavity enlarges lungs forced to expand to fill the larger cavity As lungs enlarge the intra alveolar pressure drops b c the same number of air molecules now occupy a larger lung volume o B c the intra alveolar pressure is less than atmospheric pressure air follows its pressure gradient flows into the lungs until no further gradient exists o Lung expansion is NOT CAUSED by the movement of air into the lungs instead air flows into the lungs BECAUSE of the fall in intra alveolar pressure brought about by lung expansion o Deeper inspirations are accomplished by contracting inspiratory muscles more forcefully by using inspiratory muscles to enlarge chest cavity o At end of inspiration muscles relax chest cavity returns to original size lungs return to original size Intra alveolar pressure increases as same number of air molecules occupy smaller volume Air in lungs then move down its pressure gradients expiration occurs until intra alveolar pressure equals atmospheric pressure o At rest expiration is passive process During exercise it is an active process excitatory muscles contract to decrease size of chest cavity during expiration Airway Resistance 16 14 o Role in determining airflow rates Increased in airway radius decreases resistance increases air flow rate Decreased airway radius increases resistance decreases air flow rate o Parasympathetic stimulation causes bronchoconstriction o Sympathetic stimulation causes bronchodilation Useful in fight or flight Useful in clinical treatments Administration of epic in a person w bronchial spasms can alleviate the problem Volume capacity ventilation o Important volumes healthy young males Max air lungs can hold 5700ml 4200ml F Air still in lungs after normal expiration at rest 2200 ml Air in lungs after normal inspiration 2700ml Tidal volume volume of air entering leaving in a breath 500ml Air still in lungs after maximal expiration 1200ml o Ventilation Pulmonary ventilation Tidal volume x respiratory rate Resting conditions 500ml breath x 12 breaths min 6000ml min Anatomical dead space Only air that reaches the alveoli is available for gas exchange The air that stays in conducting airways is