Flashcards in Ventilation and Gas Exchange Deck (39)
What is ventilation?
The process of bringing in fresh air into the alveoli and removing the stale air. Maintains concentration gradient of CO2 and O2 between O2 in the alveoli and CO2 in the blood capillaries.
What is gas exchange?
Process of diffusion between O2 in the alveoli and CO2 in the blood capillaries.
What is respiration?
Oxidation of organic compounds that occurs within cells, producing energy in the form of ATP.
Why do we need a ventilation system?
Ventilation is necessary as it maintains the concentration gradient of CO2 and O2 for gas exchange to occur, which itself is required for cellular respiration to occur, which itself is necessary for energy production. Thus the ventilation system is necessary for energy production.
What are Type I Pneumocytes
Extremely thin alveolar cells that are adapted to carry out gas exchange. Contained in the epithelial layers of alveoli in the lungs.
What are Type II Pneumocytes?
Rounded cells occupying part of the alveolar surface area. They secrete a fluid which coats the inner surface of the alveoli.
What is the basement membrane?
Thin, fibrous extracelular matrix of tissue separating the alveoli and blood capillary.
What is the surfactant layer?
-Moist film allowing oxygen in the alveolus to dissolve and then diffuse to the bloof capillaries.
-Provides an area from which CO2 can evaporate into the air and be exhaled.
-Monolayer of phospholipid-like molecules on the surface of the moisture layer of the alveoli with hydrophilic heads facing the water and and hydrophobic tails faicing the air in the alveoli. Reduces surface tension and prevents water from causing the sides of the alveoli to adhere when air is exhaled, preventing lung collapse.
What are four structural adaptations of the alveoli that suits them to their function of gas exchange?
Spherical shape of alveoli, and flattened, single-cell thickness of each alveolus (Type I pneumocytes), moist inner lining of alveolus from Type II pneumocytes, and associated capillary bed nearby.
Advantage of spherical shape of alveoli?
Increased surface area for diffusion
Advantage of flattened, single-cell thickness of each alveolus (Type I pneumocytes)?
Small distance to diffuse over
Advantage of moist inner lining of alveolus from Type II pneumocytes?
Prevents lung collapse. Maintains CO2 and O2 concentration gradients.
Advantage of associate capilary bed nearby?
Oxygen able to be quickly brought into the blood stream.
Describe the mechanism of inspiration.
-Muscle contractions cause the pressure inside the thorax to rise above atmospheric pressure, causing air to be drawn into the lungs until they reach atmospheric pressure.
-Diaphragm moves downwards and flattens. Ribcage moves upwards and outwards.
Describe the mechanism of expiration.
-Muscle contractions cause pressure inside the thorax to rise above atmospheric pressure, so air is forced our from the lungs to the atmosphere.
-Diaphragm moves upwards and becomes domed. Ribcage moves downwards and inwards.
What is the state of the diaphragm, abdominal muscles, external intercostal muscles, internal intercostal muscles, and air pressure with inhalation?
-abdominal muscles relax
-external intercostal muscles contract
-internal intercostal muscles relax
-air pressure decreases
What is the state of the diaphragm, abdominal muscles, external intercostal muscles, internal intercostal muscles, and air pressure with exhalation?
-abdominal muscles contract
-external intercostal muscles relax
-internal intercostal muscles contract
-air pressure increases
What is hemoglobin? What does it do?
-Protein molecule found within erythrocytes
-Carries most of the oxygen in the bloodstream
What is the structure of an erythrocyte?
Plasma membrane surrounding a denucleate cytoplasm filled with hemoglobin molecules. Few organelles or other components other than hemoglobin.
What is the structure of hemoglobin?
Composed of four polypeptides, each with a heme group near its center, and each heme group having an iron atom within it.
What is iron's role in hemoglobin?
When hemoglobin reversibly binds to an oxygen molecule, it is the iron atom within the heme group that is binding with the oxygen.
How many O2 molecules can be carried by one hemoglobin molecule? How many CO2 molecules?
4 O2 molecules. 1 CO2 molecule.
What is meant by hemoglobin's affinity for oxygen?
Hemoglobin's shape changes depending on how many oxygen are bound to hemoglobin's iron atoms. These different shapes affect hemoglobin's ability to bind with oxygen. This is known as hemoglobin's affinity for oxygen. The greater the tendency to bind with oxygen, the higher the affinity.
What is included in an oxygen dissociation curve?
Mapping of the partial pressure of oxygen (independent variable) with respect to percentage saturation of hemoglobin (dependent variable).
Define partial pressure.
The pressure exerted by a single type of gas within a mixture of gases.
What pressure units are used for the partial pressure of oxygen?
What is the relation of the partial pressure of oxygen and the saturation of hemoglobin?
As partial pressure increases, the percentage of saturation of hemoglobin increases sigmoidally.
What is myoglobin? What is its structure?
-Oxygen-binding protein found in muscles used to store oxygen within the muscle tissues until muscles begin to enter an anaerobic situation, dissociating oxygen to delay the onset of lactic acid fermentation
-Each molecule consists of a single polypeptide, a heme group, and an iron atom.
Describe the importance of fetal hemoglobin's affinity for oxygen?
Fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin. As a result, maternal hemoglobin releases oxygen in the placental capillaries while fetal hemoglobin is more likely to bind to that same oxygen such that oxygen is transferred from mother to child.
What occurs to blood at the tissues?
The partial pressure of oxygen decreases and the partial pressure of carbon dioxide increases, making the pH decrease and in turn making hemoglobin's affinity for oxygen decreases and thus releases its oxygen.
What occurs to the blood at the lungs?
Partial pressure of oxygen increases and the partial pressure of carbon dioxide decreases, making the pH increase and in turn making hemoglobin's affinity for oxygen increase and so hemoglobin takes up oxygen from the lungs.
What is the effect of CO2 on the pH of the blood?
Causes the pH of the blood to decrease.
What happens to hemoglobin when CO2 has a greater presence?
Hemoglobin is induced to dissociate oxygen
What are the three ways in which CO2 is brought out of the tissues?
-Dissolves in the blood plasma
-Enters erythrocytes and becomes reversibly bound to heme groups
-Enter erythrocytes and converted into hydrogen carbonate ions and then move into the blood plasma
How is CO2 converted to hydrogen carbonate?
-The cytoplasm of the erythrocytes contains the enzyme carbonic anhydrase which catalyzes a reaction in which carbon dioxide and water combine to form carbonic acid.
-Carbonic acid dissociates into a hydrogen carbonate ion and a hydrogen ion.
-Hydrogen carbonate ions exit the cytoplasm of the erythrocyte through specialized protein channels via facilitated diffusion, exchanging one hydrogen carbonate ions for one chloride ion. This is known as the chloride shift.
How is the ventilation rate controlled by negative feedback?
-Ventilation rate controlled by an area of the medulla oblongata of the brainstem known as the respiratory control center, where two mechanisms come into play when the rate of ventilation needs to increase.
-Receptor cells, chemosensors or chemoreceptors, in the inner wall of the aorta and carotid arteries detect when there is an increase in CO2 level and the associate degree in blood pH. When stimulated, these receptors send action potentials to the medulla's breath center.
-The medulla itself contains these types of chemosensors. As the blood passes through the capillary beds of the medulla, increased carbon dioxide and decreased pH are detected.
-To increase ventilation rate, the medulla's respiratory center sends action potentials to the diaphragm, intercostal muscles, and muscles in the abdomen, altering the frequency of breathing.
How does pO2 change with increasing altitude?
Decreases, meaning oxygen is more spread out.
How can the body acclimatize to life at high altitudes?
-Increasing the number of erythrocytes and hemoglobin
-Increasing capillaries in the lungs and muscles
-Increasing lung size and surface area for oxygen and carbon dioxide exchange
-Increase in myoglobin within muscle tissue