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Terms in this set (55)
The movement of gases between the environment and the body's cells.
-The exchange of air between the atmosphere and lungs
-The exchange of O2 and CO2 between the lungs and the blood.
-The transport of O2 and CO2 by the blood.
-The exchange of gases between blood and the cells.
A series of interconnected sacs and their associated pulmonary capillaries. These structures form the exchange surface where oxygen moves from inhaled air to the blood, and CO2 moves from the blood to air that is about to be exhaled.
Upper Respiratory Tract
Consists of the mouth, nasal cavity, pharynx, and larynx.
Lower Respiratory Tract
Consists of the trachea, 2 primary bronchi, their branches, and the lungs. It is also called the thoracic portion of the respiratory system.
Semi-rigid conducting airways that connected the lungs to the trachea.
A double-walled sac that surrounds a lung. 2 pleural sacs; 1 for each lung.
-Each pleural membrane (pleura) contains several layers of elastic connective tissue and capillaries.
-Pleural fluid holds the opposing layers of the pleural membrane together.
the pleural membrane that covers the surface of the lungs.
: the pleural membrane that lines the thoracic cavity.
It creates a moist, slippery surface so that the opposing membranes can slide across one another as the lungs move within the thorax.
-Also holds the lungs tight against the thoracic wall and holds them stretched in a partially inflated state, even at rest.
A common passageway for food, liquids, and air. It is the throat essentially.
Windpipe. A semiflexible tube help open by 15-20 C-shaped cartilage rings. It extends down into the thorax.
Mouth and Nose -> Pharynx -> Larynx -> Trachea -> Trachea branches into a pair of primary bronchi (1 per lung) -> bronchi continue to branch repeatedly into bronchioles -> bronchioles continue branching until they form a transition between the airways and the exchange epithelium of the lungs.
-diameter or airways becomes smaller as we continue down pathway
-as airways get smaller, number of airways increases
-total cross-sectional area increases as we move down path
The airways condition the air before it reaches the alveoli
1) Warms the air to body temperature (37 C) so core body temp. doesn't change and alveoli aren't damaged..
2) Adds water vapor until the air reaches 100% humidity so moist exchange epithelium doesn't dry out.
3) Filters out foreign material so bad stuff doesn't reach alveoli.
Occurs in the trachea and bronchi. The airways are lined with ciliated epithelium whose cilia are covered in a watery saline layer (allows mucous to move)
-Sticky layer of mucus floats over airway surface to trap most large particles. Mucus contains immunoglobulins that can disable many pathogens.
The cilia in the trachea and bronchi beat with an upward motion that moves the mucus continuously toward the pharynx. It can then be spit out or swallowed. Saline layer is essential for this movement.
Cells in the epithelium of airways that secretes mucus.
Type I Alveolar Cell
1 type of epithelial cell in an alveolus that is used for gas exchange. It is the larger of the 2 types of cells.
-Very thin so that gases can diffuse rapidly through them.
Type II Alveolar Cell
The smaller but thicker of the 2 alveolar cell types. They synthesize and secrete surfactant. Also help minimize the amount of fluid present in the alveoli by transporting solutes, followed by water, out of the alveolar air space.
A mixture of lipoproteins dipalmitoylphosphatidylcholine (DPPC) that are secreted by Type II alveolar cells and mixes with the thin fluid lining of the alveoli to help lungs expand during breathing by breaking up alveolar surface tension.
-Surfactant is more concentrated in smaller alveoli, making their surface tension less than that in larger alveoli. Helps to equalize the pressure among alveoli of different sizes.
Begins with the pulmonary trunk, which receives low-oxygen blood from the right ventricle. Pulmonary trunk divides into 2 pulmonary arteries (1 per lung).
-Rate of blood flow through the lungs is much higher than the rate in other tissues because the lungs receive entire CO of the right ventricle.
-Pulmonary circulation resistance is very low because large total cross-sectional area and distensibility of pulmonary arterioles.
-Pulmonary BP is low as a result.
The total pressure exerted by a mixture of gasses is the sum of the pressures exerted by the individual gases.
The pressure of a single gas in a mixture. This is determined only by the gas' relative abundance in the mixture and is independent of molecular size or mass of the gas.
P1V1 = P2V2
If the volume of a fas is reduced, the pressure increases and vice versa.
: The volume of air that moves during a single inspiration or expiration. ~500 mL.
Inspiratory Reserve Volume (IRV)
: The additional volume you inspire above the tidal volume. ~3000 mL.
Expiratory Reserve Volume (ERV)
: The amount of air forcefully exhaled after the end of a normal expiration. ~1100 mL.
Residual Volume (RV)
: The volume of air in the respiratory system after maximal exhalation.
-Most of this RV is due to the lungs being stretched against the ribs by the pleural fluid.
Vital Capacity (VC)
: It represents the maximum amount of air that can be voluntarily moved into or out of the respiratory system with one breath. It declines with age.
-IRV + ERV + TV
Total Lung Capacity (TLC)
: VC + RV
Inspiratory Capacity (IC)
: TV + IRV
Functional Residual Capacity (FRC)
: ERV + RV
1) Diaphragm contracts and drops down toward the abdomen.
2) Scalene and external intercostal muscles contract and pull rib cage up and out.
3) Thoracic volume increases, thoracic pressure decreases, and air flows into the lungs.
Expiration during quiet breathing.
1) Muscles relax
2) Elastic recoil of the lungs and thoracic cage returns the diaphragm and rib cage to their original, relaxed positions.
3) Volume decreases, pressure increases, and air is expelled.
Occurs during exercise or faced heavy breathing, voluntary exhalations.
-Uses internal intercostal muscles and abdominal muscles (collectively called expiratory muscles).
Sub atmospheric Intrapleural Pressure
The 2 pleural membranes are held together by the pleural fluid bond, so lungs are forced to stretch to conform to volume of thoracic cavity.
-At the same time, elastic recoil of the lungs creates an inwardly directed force that tries to pull the lungs away from the chest wall
-As a result, a sub atmospheric intrapleural pressure is created. ~ 3 mm Hg.
Law of LaPlace
P = 2T/r
T = surface tension
P = pressure
r = radius
Pressure is greater in a smaller bubble than in a bigger bubble.
Red Blood Cells, the most abundant cell type in blood.
-Biconcave shape allows the cell to modify their shape in response to osmotic changes in the blood.
-Simply membranous bags filled with enzymes and hemoglobin.
-Glycolysis is their primary source of ATP because they have no mitochondria.
-Can't make new enzymes or renew their membrane components because they have no nucleus or ER.
-Very flexible, but flexibility decreases with age.
1) In bone marrow, committed progenitor cells differentiate through several stages into large, nucleated
2) Erythroblasts mature and nucleus condenses and the cell shrinks.
3) The nucleus is pinched off and phagocytize by bone marrow macrophages. Other membranous organelles break down and disappear. It is now a
4) The reticulocyte leaves the marrow and enters circulation where it matures into an erythrocyte within 24 hours.
The main component of RBCs. It is a tetrameric (4 stuck together) protein with 4 globular protein chains, each wrapped around an iron-containing heme group. Each hemoglobin molecule has the potential to bind reversibly 4 oxygen molecules.
A condition in which hemoglobin content is too low and blood cannot transport enough oxygen to tissues.
Factors Influencing Alveolar Gas Exchange
1) O2 reaching the alveoli
-composition of inspired air
==rate and depth of breathing
2) Gas diffusion between alveoli and blood
==amount of fluid
3) Adequate perfusion of alveoli
Fick Law of Diffusion
Diffusion occurs across a concentration gradient and from areas of high concentration to low concentration. -Diffusion rate is proportional to surface area. QO2 = CO X (arterial oxygen content - venous oxygen content).
-QO2 = oxygen consumption
Oxygen transport in blood has 2 components: the oxygen that is dissolved in the plasma (<2%) and the oxygen bound to hemoglobin (>98%).
Oxygen Binding to Hemoglobin
Obeys the law of mass action: as the concentration of free O2 increases, more oxygen binds to hemoglobin and more HbO2 is produced. Also, cooperative binding so when 1 oxygen binds, the other subunits have a higher affinity for oxygen
= O2 in alveolar air -> plasma -> RBC -> binds to hemoglobin
=occurs so rapidly that blood in pulmonary capillaries normally picks up as much oxygen as the PO2 and number of RBCs allow.
=process reverses at tissues
Factors Influencing the Amount of O2-Hb Binding
It depends on the PO2 in the plasma surrounding the RBC and the number of potential Hb binding sites available in the RBCs.
-plasma PO2 is the primary factor and it is established by the composition of inspired air, the alveolar ventilation rate, and the efficiency of gas exchange from alveoli to blood.
-total number of O2-biding sites depends on the number of hemoglobin molecules in the RBCs.
Percent Saturation of Hemoglobin
The amount of oxygen bound to hemoglobin at any given PO2 is given as this.
(Amount of O2 bound/maximum that could be bound) X 100 = percent saturation of hemoglobin
Although CO2 is more soluble than O2 in blood, the body produces much more CO2 than can dissolve. CO2 is transported in 3 ways:
1) 7% of CO2 dissolves in plasma
2) 23% binds to hemoglobin
3) 70% is converted to bicarbonate ion
CO2 -> Bicarbonate
The conversion of CO2 to bicarbonate provides an additional mode of CO2 transport as well as acting as a buffer for metabolic acids.
-Dissolved CO2 in the plasma diffused into RBCs where it reacts with water in the presence of carbonic anhydrase to form carbonic acid (H2CO3).
-Carbonic acid then dissociates into hydrogen and a bicarbonate ion.
Co2 + H20 <=> H2Co3 <=> H+ + HCO3-
-This reaction is reversible and obeys the laws of mass action.
The products of CO2 <=> HCO3 must be removed from the cell in order to allow the reaction to keep going. Low product concentrations = more CO2 out of plasma and into RBC = more CO2 out of tissues into plasma.
-chloride shift is the transport process that moves bicarbonate out of the RBC on an antiport protein.
-Cl- is exchanged for HCO3-
Removal of H+ From the RBC
Hemoglobin acts as a buffer and binds hydrogen ions
-H+ + Hb <=> HbH
-prevents large changes in the body's pH because it keeps H+ out of the plasma.
CO2 is the primary stimulus for changes in ventilation. O2 and plasma pH play lesser roles.
-if too little O2 is present in arterial blood destined for the brain and other tissues, the rate and depth of breathing increases.
-if rate of CO2 production > rate of CO2 removal, arterial PCO2 increases, and ventilation is intensified to match CO2 removal to production.
Peripheral chemoreceptors outside the CNS sense changes in the PO2, pH, and PCO2 of plasma.
in the carotid arteries are the primary peripheral chemoreceptors.
-when type 1 or gloms cells in the carotid bodies are activated by a decrease in PO2 or pH or by an increase in PCO2, they trigger a reflex to increase ventilation.
They primarily lie on the medulla. They set respiratory pace and respond to changes in pH. When arterial PCO2 increases, CO2 crosses the BBB into CSF. CO2 and CSF react to make carbonic acid, which dissociates into bicarbonate and H+. H+ initiates the chemoreceptor reflex and ventilation is increased.
-If PCO2 remains elevated for several days, ventilation falls back toward normal rates as the chemoreceptor response adapts.
The most common capillaries. They have endothelial cells joined to one another with leaky junctions.
-found in muscle, connective tissue, and neural tissue.
-the continuous capillaries of the brain have evolved to form the BBB
-blood cells ad most plasma proteins are unable to pass through the junctions between endothelial cells.
Capillaries with large pores that allow high volumes of fluid to pass rapidly between the plasma and interstitial fluid.
-found primarily in the kidney and the intestine.
Velocity of Blood Flow
The primary determinant of velocity is not the diameter of an individual capillary, but the total cross-sectional area of all the capillaries.
-Total cross-sectional area is largest in the capillaries so blood flow velocity is slowest in the capillaries. This makes sense because it gives us more time for diffusion.
The mass movement of fluid as a result of hydrostatic or osmotic pressure gradients.
-Absorption is in, filtration is out
-Most capillaries show a transition from net filtration at the arterial end to net absorption at the venous end.
-Hydrostatic pressure and osmotic pressure are the 2 forces that regulate bulk flow in capillaries
The lateral pressure component of blood flow that pushes fluid out through the capillary pores.
-Decreases along the length of the capillary as energy is lost to friction
Determined by the solute concentration of a compartment. Osmotic pressure created by the presence of proteins is called colloid osmotic pressure or
-Oncotic pressure is higher in the plasma than in the interstitial fluid so it favors water movement into plasma.
-Remains constant along the length of the capillary.
Asthma is caused by bronchiole constriction and excess mucous secretion.
-It can be triggered by environmental stimuli (dust, pollen)
-Treatments include β2-adrenergic receptor agonists
(albuterol)- causes relaxation of airway smooth muscle and dilation of lung air passages
A pneumothorax is an abnormal collection of air in the pleural space that causes an uncoupling of the lung from the chest wall.
Analogous to 1 subunit of hemoglobin. Myoglobin helps to coax oxygen to head toward and bind to proteins in muscle cells.
State that hemoglobin's oxygen binding affinity is inversely related both to acidity and to the concentration of carbon dioxide.
-As pH decreases, reaction shifts to the left: Hemoglobin "gives up" oxygen more easily
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