19.5: Alveolar Gas Exchanges Carissa, Sidney, Maret, Grace Alveoli Alveoli: microscopic air sacs clustered at the distal ends of the alveolar ducts- the finest respiratory tubes Each alveolus (singular) is a tiny space within a thin wall that separates adjacent alveoli Alveolar pores: tiny openings in the walls of some alveoli that permit air to pass from one alveolus to another Alveolar macrophages: phagocytic cells in alveoli
and their pores Phagocytize airborne agents like bacteria, cleaning the alveoli Respiratory Membrane Alveolar Wall Mostly consists of a layer of simple squamous epithelium cells (type I cells) Small portion made up of type II cells that secrete pulmonary surfactant Pulmonary surfactant: mixture of lipids and proteins to lower surface tension at the air/liquid interface within alveoli Dense network of capillaries within walls of type I cells; separated from alveolar
walls by a thin basement membrane Space between alveolar wall and capillaries filled with elastic and collagen fibers to support alveolar walls Respiratory Membrane Respiratory membrane (alveolar capillary membrane) Consists of two thicknesses of epithelial cells and basement membrane cells Separates the air in an alveolus and the blood in a capillary AKA: respiratory membrane is the layers through which gas exchange occurs between the alveolar air and the blood
Exercise and Breathing Exercise increases the amount of oxygen skeletal muscles use Young man at rest uses about 250 mL of oxygen per minute but may require 3,600 mL per minute during exercise Carbon dioxide production increases as oxygen use increases during exercise Exercise stimulates respiratory centers, but does not increase blood oxygen and carbon dioxide levels, only breathing rate Breathing rate increases with exercise by the cerebral cortex and
the proprioceptors associated with muscles and joints Cerebral cortex sends stimulating impulses to the respiratory center whenever it signals the skeletal muscles to contract Muscle movements stimulate the proprioceptors, triggering a joint reflex where sensory impulses are conducted from the proprioceptors to the respiratory center, Exercise and Breathing Breathing rate and blood flow are increased by exercise Exercise taxes both the respiratory and cardiovascular systems Shortness of breath will occur if either of theses systems doesnt keep up
Shortness of breath due to the inability of the cardiovascular system to move enough blood between the lungs and cells, not the inability of the respiratory system to provide enough air Diffusion through the Respiratory Membrane Solutes diffuse from areas of high concentration to areas of low concentration Concentration gradient is needed to determine the direction of diffusion of a solute
Dissolved gas becomes proportional to its partial pressure in blood For example, the PCO2 of blood entering the pulmonary capillaries is 45 mm of Hg and the PCO2 in the alveolar air is 40 mm Hg Difference in alveolar pressure As long as breathing continues, the alveolar partial pressure of carbon dioxide stays fairly constant due to the large volume of air that is always in the lungs Diffusion through the Respiratory Membrane
Membrane is normally thin Gas exchange is rapid Factors that affect diffusion across the respiratory membrane include more surface area, shorter distance, greater solubility of gases, and a steeper partial pressure gradient A disease that harms the respiratory membrane: pneumonia A disease that reduces the surface area for diffusion: emphysema Both can impair gas exchange and may require increased PO2 for treatment Breath analysis
Effects of High Altitude Altitude sickness Can occur at varying degrees As elevation increases, the amount of oxygen in the air stays constant, but the PO2 decreases Ascension causes diffusion to occur more slowly In response, your body will try to get more oxygen through increased breathing and heart rate, as well as enhanced blood cell and hemoglobin production Effects of High Altitude
Severe altitude sickness is a condition called high altitude pulmonary edema (HAPE) Symptoms include severe headache, nausea and vomiting, rapid heart rate and breathing, blue cast to skin Low blood oxygen (hypoxia) can constrict pulmonary blood vessels In some cases, this can develop into high altitude cerebral edema (HACE) Treated with oxygen and coming down the mountain or prescription medicines that reduce pulmonary hypertension Diseases that Impair Gas Exchange
Pneumonia Alveolar linings swell with edema Swelling causes the surface area for gas exchange to diminish If left untreated, Pneumonia is fatal Treatments include take home antibiotics, cough medicine, and/or fever/pain reducers
Tuberculosis Caused by Mycobacterium tuberculosis Fibrous connective tissue forms tubercles Tubercles restrict gas exchange
Not very contagious Treatment includes antibiotics Diseases that Impair Gas Exchange Atelectasis Collapsed lung Complication after surgery Functional regions can usually carry on gas exchange Acute Respiratory Distress Syndrome (ARDS) Fluid buildup in alveoli
Occurs after an injury or infection You can get vaccinated and/or stop smoking Severe Acute Respiratory Syndrome (SARS) Serious and sometime fatal respiratory illness First case: China, 2002
No cases since 2004 No effective treatment Hair- Alveoli Mother Gothel- Oxygen Tower- Capillary Rapunzel- Tissue Cell Frying Pan- Alveolar Macrophages
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