1. 19.5: Alveolar Gas Exchanges
Carissa, Sidney, Maret, Grace

2. 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

3. 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

4. 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

5. 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, increasing respiration rate

6. 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 doesn’t 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. Hair- Alveoli
Tower- Capillary
Mother Gothel- Oxygen

14. Rapunzel- Tissue Cell
Doorway- Respiratory Membrane
Frying Pan- Alveolar Macrophages

15. Flynn Rider- Airborne Agent
(Bacteria)
Frying Pan- Alveolar Macrophages

16. Tower- Capillary
Hair- Alveoli
Mother Gothel- CO2

17. https://play.kahoot.it/#/k/36bd0c6a-a321-4464-89f2-307b64711617