Transport of Oxygen and Carbon Dioxide in Blood and Tissue Fluids

Vocabulary-style flashcards covering the principles of oxygen and carbon dioxide transport, diffusion gradients, hemoglobin kinetics, and metabolic factors based on the lecture transcript.

Hemoglobin Oxygen Transport Proportion

$97 \%$ of the oxygen transported from the lungs to the tissues is carried in chemical combination with hemoglobin in the red blood cells, while the remaining $3 \%$ is transported in the dissolved state.

Alveolar PO2

The average partial pressure of oxygen in the gaseous oxygen of the alveolus, which is $104\,mm\,Hg$.

Venous PO2

The average oxygen partial pressure of the venous blood entering the pulmonary capillary at its arterial end, which is $40\,mm\,Hg$.

Diffusion Pressure Gradient (Lungs)

The initial pressure difference that causes $O_2$ to diffuse into the pulmonary capillary, calculated as $104\,mm\,Hg$ minus $40\,mm\,Hg$, or $64\,mm\,Hg$.

Shunt Flow

The $2\,\%$ of blood flow that passes from the aorta through the bronchial circulation to supply deep lung tissues without being exposed to lung air, resulting in a $PO_2$ of about $40\,mm\,Hg$.

Venous Admixture of Blood

The combination of oxygenated blood from alveolar capillaries with shunt blood, which causes the $PO_2$ of blood entering the left heart and pumped into the aorta to fall to about $95\,mm\,Hg$.

Interstitial Fluid PO2

The average partial pressure of oxygen in the fluid surrounding the tissue cells, which is $40\,mm\,Hg$.

Intracellular PO2

The partial pressure of oxygen inside peripheral tissue cells, which ranges from $5\,mm\,Hg$ to $40\,mm\,Hg$ and averages $23\,mm\,Hg$.

Critical Intracellular PO2

The minimum level of oxygen pressure ($1$ to $3\,mm\,Hg$) required for full support of the chemical processes that use oxygen in the cell.

CO2 Diffusion Rate

Carbon dioxide can diffuse about $20$ times as rapidly as oxygen, meaning far less pressure difference is required for its movement.

Intracellular PCO2

The partial pressure of carbon dioxide inside the cells, which is approximately $46\,mm\,Hg$.

Interstitial PCO2

The partial pressure of carbon dioxide in the interstitial fluid, which is approximately $45\,mm\,Hg$.

Alveolar PCO2

The partial pressure of carbon dioxide in the alveolar air, which is $40\,mm\,Hg$.

Oxygen-Hemoglobin Dissociation Curve

A graph demonstrating the progressive increase in the percentage of hemoglobin bound with $O_2$ (percent saturation) as blood $PO_2$ increases.

Hemoglobin Oxygen Capacity

The maximum amount of oxygen that can combine with hemoglobin; with $15\,g$ of hemoglobin per $100\,ml$ of blood and a binding constant of $1.34\,ml$ of $O_2$ per gram, the total capacity is approximately $20\,volumes\,\%$.

Utilization Coefficient

The percentage of the blood that gives up its $O_2$ as it passes through the tissue capillaries, normally about $25\,\%$, but increasing up to $75\%$ to $85\,\%$ during strenuous exercise.

Hemoglobin Tissue Oxygen Buffer System

The function of hemoglobin responsible for stabilizing the $PO_2$ in the tissues, normally maintaining it between $15$ and $40\,mm\,Hg$ even when atmospheric oxygen concentration changes markedly.

Bohr Effect

The shift of the oxygen-hemoglobin dissociation curve to the right and downward in response to increased blood $CO_2$ and hydrogen ions, which enhances the release of $O_2$ from the blood to the tissues.

2,3-biphosphoglycerate (BPG)

A metabolically important phosphate compound in the blood that shifts the oxygen-hemoglobin dissociation curve to the right, facilitating the release of oxygen during hypoxia.

ADP Control of Oxygen Usage

The principle that the rate of oxygen usage by the cells is controlled by the rate of energy expenditure, specifically the concentration of adenosine diphosphate ($ADP$) formed from $ATP$.平衡

Diffusion-Limited Oxygen Usage

A condition, typically pathological, where the rate of oxygen diffusion to the cells is so low that intracellular $PO_2$ falls below the critical level, making diffusion the rate-limiting factor for metabolism.

Blood Flow-Limited Oxygen Usage

A state where the rate of blood flow through a tissue is so low that the amount of available oxygen falls below what is required for intracellular metabolism.

Carbon Monoxide Tenacity

Carbon monoxide binds with hemoglobin at the same point as oxygen but with about $250$ times as much tenacity, allowing a $CO$ partial pressure of only $0.4\,mm\,Hg$ to compete equally with $O_2$.

Carbonic Anhydrase

An enzyme inside red blood cells that catalyzes the reaction between $CO_2$ and water, accelerating the reaction rate about $5000$-fold to facilitate bicarbonate formation.

Chloride Shift

The phenomenon where bicarbonate ions ($HCO_3^-$) diffuse out of red blood cells into the plasma while chloride ions ($Cl^-$) diffuse into the cells to maintain electrical neutrality, resulting in higher chloride content in venous red blood cells.

Carbaminohemoglobin

The compound formed when $CO_2$ reacts directly with amine radicals of the hemoglobin molecule, accounting for approximately $20\,\%$ to $30\,\%$ of total $CO_2$ transport.

Haldane Effect

The phenomenon where the binding of oxygen with hemoglobin in the lungs promotes the displacement of carbon dioxide from the blood into the alveoli.

Respiratory Exchange Ratio (R)

The ratio of $CO_2$ output to $O_2$ uptake; it averages $0.825$ for a normal diet, but is $1.0$ for exclusive carbohydrate metabolism and $0.7$ for exclusive fat metabolism.