Anat test 3

What is the difference between ventilation and diffusion in pulmonary gas exchange?

Ventilation moves gas into and out of the lungs, while diffusion is the passive movement of gas molecules across the alveolar-capillary membrane driven by concentration gradients.

What is barometric pressure at sea level?

Barometric pressure at sea level is 760 mmHg

What are the primary components of atmospheric pressure?

The primary components are nitrogen, oxygen, argon, and carbon dioxide.

How does the partial pressure of O2 in the alveoli compare to that in the atmosphere?

The partial pressure of O2 is significantly lower in the alveoli than in the atmosphere due to dilution by CO2 and water vapor.

What is the partial pressure of water vapor (PH2O) in the lungs?

The partial pressure of water vapor is 47 mmHg.

What is the alveolar gas equation?

The alveolar oxygen (PAO2) is calculated as:

PAO2=[PB−PH2O]×FIO2−PACO2×1.25PAO2=[PB−PH2O]×FIO2−PACO2×1.25

What occurs during gas diffusion until equilibrium is reached?

Gas diffusion continues until the partial pressures are equal on both sides of the A-C membrane, typically taking about 0.25 seconds.

What is Fick's Law?

Fick's Law states that the rate of gas transfer across a tissue is proportional to surface area, diffusion constant, and pressure difference, and inversely proportional to tissue thickness.

What does Henry's Law state?

Henry's Law states that the amount of a gas that dissolves in a liquid is proportional to the partial pressure of the gas.

What is Graham's Law?

Graham's Law states that the rate of diffusion of a gas is directly proportional to its solubility coefficient and inversely proportional to the square root of its molecular weight.

What are some clinical conditions that can impair gas diffusion?

Conditions include atelectasis, high altitudes, and pulmonary fibrosis.

What is the difference between perfusion limited and diffusion limited gas flow?

Perfusion limited means gas transfer is dependent on blood flow, while diffusion limited means it is dependent on the integrity of the A-C membrane.

How does oxygen diffusion typically occur under normal resting conditions?

Oxygen diffusion is typically perfusion limited, reaching equilibrium when blood is about one-third of the way through the capillary.

What happens to carbon monoxide (CO) during gas exchange?

Carbon monoxide rapidly bonds to hemoglobin, resulting in minimal partial pressure in the plasma.

What is the role of ventilation in the lungs?

Ventilation moves gas into and out of the lungs.

What is passive diffusion in the context of pulmonary gas exchange?

Passive diffusion is the movement of gas molecules across the alveolar-capillary membrane from areas of high concentration to low concentration.

What does the process of diffusion in the lungs involve?

Diffusion involves the passive movement of gas until equilibrium is reached, typically in about 0.25 seconds during a total blood transit time of 0.75 seconds.

What is the composition of the alveolar-capillary membrane?

It consists of the liquid lining of the intra-alveolar membrane, alveolar epithelial cells, basement membranes, connective tissue, capillary endothelium, and plasma.

What are the average oxygen and carbon dioxide tensions in venous blood entering the A-C system?

Average O2 tension is 40 mmHg, and average CO2 tension is 46 mmHg.

What is the significance of Fick's Law in gas diffusion?

Fick's Law indicates that gas transfer is proportional to surface area, diffusion constant, and pressure difference, and inversely proportional to tissue thickness.

What is the solubility coefficient for CO2 and O2?

The solubility of CO2 is 0.592, and O2 is 0.0244.

How does a decreased alveolar surface area affect O2 diffusion?

A decreased surface area (e.g., atelectasis) reduces O2 transfer into pulmonary capillary blood.

What is the difference between perfusion limited and diffusion limited gas flow?

Perfusion limited means gas transfer depends on blood flow; diffusion limited means it depends on the integrity of the A-C membrane.

What occurs to gas equilibrium during exercise?

During exercise, blood transit through the A-C system is faster, reducing the time for gas diffusion, which can affect O2 equilibrium.

How does pulmonary edema affect gas diffusion?

Pulmonary edema increases tissue thickness, impairing the movement of O2 across the A-C membrane.

How does carbon monoxide affect gas exchange?

CO rapidly binds to hemoglobin, limiting its partial pressure in the plasma and disrupting normal gas diffusion.

What are the implications of diffusion problems in clinical conditions?

Conditions like pulmonary fibrosis or edema can lead to decreased diffusion capacity and impaired gas exchange.

What is the primary function of the circulatory system?

To deliver oxygen to the cells of the body.

What happens when blood flow is inadequate?

Good alveolar ventilation becomes ineffective.

What components make up the circulatory system?

Blood, the heart, and the vascular system.

What are the main components of blood?

Erythrocytes (RBC), leukocytes (WBC), and thrombocytes (platelets).

What is hematocrit?

The percentage of RBCs in relation to total blood volume.

What is the normal hematocrit for adult males and females?

Males: 45%, Females: 42%.

What is the primary function of leukocytes?

To protect the body against bacteria and foreign agents.

What is the average leukocyte count in blood?

5000 to 9000 cells per cubic millimeter.

What indicates a bacterial infection in leukocytes?

A high neutrophil count.

What is the function of thrombocytes (platelets)?

To prevent blood loss and activate clotting factors.

What constitutes the majority of plasma?

Water (about 90%).

What proteins are found in plasma?

Albumins, globulins, and fibrinogen.

How does blood flow through the heart?

• Pathway: Right atrium → right ventricle → lungs → left atrium → left ventricle → aorta.

What are the major arteries supplying the heart?

The left coronary artery and the right coronary artery.

What is the function of the vasomotor center?

To regulate the number of sympathetic impulses sent to the vascular system, maintaining vascular tone.

What are baroreceptors?

Specialized stretch receptors that help regulate arterial blood pressure.

How is mean arterial pressure (MAP) estimated?

MAP = DBP + (1/3)(SBP - DBP).

What influences cardiac output (CO)?

Stroke volume (SV) and heart rate (HR); CO = SV x HR.

What factors affect ventricular preload?

Ventricular end-diastolic pressure (VEDP) and end-diastolic volume (VEDV).

What is ventricular afterload?

The pressure the ventricle must overcome to eject blood into circulation.

What is vascular resistance?

The resistance the circulatory system offers against blood flow, affected by mean arterial pressure (MAP) and cardiac output (CO).

What are active mechanisms affecting vascular resistance?

Abnormal ABGs, pharmacologic stimulation, and pathologic conditions.

What do passive mechanisms refer to in the context of vascular resistance?

Secondary changes in resistance due to mechanical changes, such as blood volume changes.

How does gravity affect blood flow in the lungs?

Blood flow decreases from the base to the apex of the lungs due to gravity.

What is the Frank-Starling law?

The greater the myocardial stretch before contraction, the greater the contraction, up to a point.

Specific Leukocytes

• Neutrophils: Response to bacterial infections.

• Eosinophils/Basophils: Allergic reactions.

• Monocytes: Chronic infections.

• Lymphocytes: Antibody production.

Thrombocytes (Platelets)

• Function: Prevent blood loss; normal count 250,000 to 500,000.

• Mechanism: Activate platelet factor for clotting.

Plasma

• Composition: 55% of blood volume; 90% water.

• Contents: Proteins, electrolytes, gases, waste products.

Heart structure

• Chambers: Right/left atria, right/left ventricles.

• Function: Acts as two separate pumps.

Coronary circulation

• Supplies: Heart via left and right coronary arteries.

• Resting Supply: ~5% of total cardiac output.

Vascular Systems

Types: Systemic (aorta to right atrium) and pulmonary (pulmonary trunk to left atrium)

Components: Arteries, arterioles, capillaries, venules, veins

Neural Control of Vascular System

Function : Sympathetic impulses maintain vasomotor tone

Baroreceptors : Regulate arterial blood pressure

The Baroreceptor Reflex

Location : Carotid arteries and aorta

Function : Adjusts blood pressure reflexively

Cardiac Output ( CO )

Formula : CO - Stroke Volume ( SV ) x Heart Rate ( HR ) .

Influence : SV and HR directly affect blood pressure

Ventricular Preload

Definition : Degree of myocardial stretch before contraction

Impact : Higher preload leads to greater contraction

Ventricular Afterload

Definition : Force the ventricle must overcome to eject blood

Factors : Blood volume , viscosity , vascular resistance

Vascular Resistance

Calculation : Resistance= Mean Arterial Pressure ( MAP ) / CO

Active Mechanisms of Vascular Resistance

Triggers : Abnormal blood gases , pharmacologic stimulation , pathologic conditions

Passive Mechanisms of Vascular Resistance

Definition : Changes in resistance due to mechanical changes ( e.g. , lung volume )

Impact : Varies with changes in pulmonary artery pressure

Distribution of Pulmonary Blood Flow

Gravity Impact : Blood flow decreases from lung base to apex

Determinants of Cardiac Output

Key Factors : Preload , afterload , contractility

Types of Cardiac Cells

Myocardial Cells : Mechanical cells responsible for contraction

Pacemaker Cells : Specialized cells generating spontaneous impulses

Action Potentials

Definition : Electrical changes across cardiac cell membranes

Resting State

Polarized State : Cardiac cells are polarized with a negative intracellular charge Involved

Electrolytes Involved: Potassium (K+), Calcium (Ca2+), Sodium (Nat).

Polarized State Mechanism

Ion Movement : For each Na + entering , about 75 K + exit , creating a negative charge inside the cell

Properties of Cardiac Tissue

Automaticity : Ability of the SA node to generate action potentials independently Excitability : Capacity to respond to stimuli ; decreased excitability needs stronger stimuli

Contractility : Ability of cardiac muscle to contract in response to a stimulus

Conductivity : Ability to conduct electrical impulses

The Conduction System

SA Node : Pacemaker ( 60-100 bpm ) .

AV Node : Secondary pacemaker ( 40-60 bpm ) .

Bundle Branches : Left and right pathways for impulse conduction .

Purkinje Fibers : Distribute impulses throughout the ventricles

Refractory Periods

Absolute Refractory Period : Cells cannot respond to a stimulus ( phases 0 , 1 , 2 , and half of 3 ) .

Relative Refractory Period : Cells are almost repolarized ; a strong stimulus can cause depolarization ( second half of phase 3 )

Nonrefractory Period : All cells are at rest ( phase 4 ) .

Neural Control of the Cardiac System

Sympathetic Nervous System : Increases heart rate and contractility

Parasympathetic Nervous System : Decreases heart rate and contractility

Components of an EKG

P Wave : Represents atrial contraction

QRS Complex : Represents ventricular contraction

T Wave : Represents ventricular repolarization

Types of Cardiac Cells

Myocardial Cells :

Function : Responsible for the mechanical contraction of the heart

Role : Contract in response to electrical impulses , facilitating blood pumping .

Pacemaker Cells :

Function : Specialized cells in the cardiac conduction system

Role : Generate spontaneous action potentials , initiating the heartbeat

Action Potentials

Definition : A rapid change in membrane potential that occurs when cardiac cells are stimulated

Phases : Involves depolarization and repolarization of cardiac cells

Resting State

Polarized State :

Definition : Condition of cardiac cells at rest , maintaining a negative charge inside

Importance : Essential for the generation of action potentials

Electrolytes :

Potassium ( K + ) : Predominantly intracellular ; crucial for maintaining resting potential

Calcium ( Ca2 + ) : Plays a role in contraction and action potential propagation

Sodium ( Na + ) : Primarily extracellular ; important for depolarization

Polarized State Mechanism

Ion Movement Na + Influx : For each sodium ion entering the cell , approximately 75 potassium ions exit , resulting in a net negative charge inside the cell

sympathetic stimulation

increases heart rate

sympathetic block

decreases heart rate

Parasympathetic stimulation

decreases heart rate

Parasympathetic block

increases heart rate

Which of the following gas laws states that in a mixture of gases the total pressure is equal to the sum of the partial pressure of each gas ?

Dalton's law

At sea level , the normal percentage of carbon dioxide ( CO2 ) in the atmosphere is

0.03 %

At sea level , the alveolar water vapor pressure is normally about

47 mm Hg

The normal transit time for blood through the alveolar - capillary system is about

0.75 second

Under normal resting conditions , the diffusion of oxygen and carbon dioxide is usually completed in about

0.25 second, one - third of the time available

Which of the following states that the rate of gas diffusion is inversely proportional to the weight of the gas ?

Graham's law

According to Fick's law , gas diffusion is

Directly proportional to the difference in partial pressure of the gas between the two sides

As a result of the severe left heart failure and increased pulmonary blood pressure in the case , fluid moved out of the pulmonary capillaries and into the extracapillary spaces . The pathologic process caused the thickness of the alveolar - capillary membrane to___________

Also increase

Because gas diffusion is indirectly related to the thickness , the diffusion of oxygen across the alveolar capillary membrane in this case

Decreased

While the physician was treating the patient's failing heart , the respiratory therapist worked to offset the patient's poor oxygenation by increasing the patient's__________ which is _________of Fick's law

PAO ; Pi

The therapist achieved the goal in question 3 by increasing the patient's overall ____________, and increasing the inspired____________

Pressure at the level of the alveoli ; Flo , to 0.4

Which factor in Fick's law confirmed why the patient's oxygenation status was chronically low in this case?

Thickness

Which factor in Fick's law was used therapeutically to improve the patient's oxygenation status ?

Pa ( P1 )

Which factor in Fick's law caused the patient's oxygenation status to acutely worsen in this case ?

T ( thickness )

Which factor in Fick's law confirmed why the patient's oxygenation status was chronically low in this case ?

Thickness