Module 1: Vascular System 1.5-1.9 Flashcards
Arterioles branch into _____\_, which function in the exchange of _____ and____\_ between the_____ and the ________\_.
Arterioles branch into capillaries, which function in the exchange of solutes and fluids between the blood and the interstitial fluid.
Two important factors make capillaries the best location for diffusion:
- Capillaries have a _________\_. As a result, erythrocytes (red blood cells) must flow through the capillaries _______\_.
- The wall of a capillary is formed by a________ and, as such, provides the thinnest possible diffusion barrier for the movement of solutes and fluid across the capillary wall.
Two important factors make capillaries the best location for diffusion:
- Capillaries have a very small diameter of 5—10 μm. As a result, erythrocytes (red blood cells) must flow through the capillaries in single file.
- The wall of a capillary is formed by a single layer of epithelial cells and, as such, provides the thinnest possible diffusion barrier for the movement of solutes and fluid across the capillary wall.
There are two types of capillaries
- _______
- _______
There are two types of capillaries:
- Fenestrated
- Continuous
Continuous capillaries, the most common type, allow only ___________\_to move through the intercellular spaces between the _________\_
Continuous capillaries, the most common type, allow only small water-soluble molecules to move through the intercellular spaces between the capillary endothelial cells.
Where would you find fenestrated capillaries?
kidneys, liver, intestines and bone marrow
What is important about fenestrated capillaries and where they are located?
Fenestrated capillaries have fenestrations (intercellular spaces) that allow larger water-soluble molecules to move through.
Some fenestrated capillaries allow proteins and blood cells to pass through (kidneys/lymphatics)
Capillaries extend from ______ which are vessels connecting the arterioles to the venules
Capillaries extend from metaarterioles which are vessels connecting the arterioles to the venules
Blood flow through the capillaries is regulated by the contractile state of ______\_in the arteriolar walls, as well as by the ________\_, which are located at the capillary entrance around the metarterioles.
Blood flow through the capillaries is regulated by the contractile state of smooth muscle in the arteriolar walls, as well as by the precapillary sphincters, which are located at the capillary entrance around the metarterioles.
Solutes and fluids move across the capillary walls by
- _______,
- _______, or
- _______
Solutes and fluids move across the capillary walls by
- diffusion,
- transcytosis, or
- mediated transport
Diffusion of lipophilic molecules occurs __________\_the capillary endothelial cell, whereas diffusion of lipophobic molecules occurs _________\_ the capillary endothelial cells
Diffusion of lipophilic molecules occurs across the membrane of the capillary endothelial cell, whereas diffusion of lipophobic molecules occurs through the intercellular spaces in between the capillary endothelial cells
What is transcytosis? How is it used in the capillary beds?
Transcytosis is a form of vesicular transport.
In capillaries, larger lipophobic molecules can cross the capillary endothelial cells via transcytosis
Mediated transport requires ______\_ specific to the molecule to be transported
Mediated transport requires transport proteins specific to the molecule being transported
Mediated transport is primarily used in which organ?
Primarily used for transport across the capillaries of the brain.
The primary mechanism of exchange across the capillaries (excluding the capillaries of the brain) is by ______\_.
The primary mechanism of exchange across the capillaries (excluding the capillaries of the brain) is by diffusion.
The secondary mechanism of exchange occurs through _______\_ across the capillary wall
The secondary mechanism of exchange occurs through bulk flow of solutes and fluids across the capillary wall
Bulk flow occurs as the result of ________\_—determined by the ____\_ forces—and involves both ____\_and ____\_ processes
Bulk flow occurs as the result of pressure gradients—determined by the Starling forces—and involves both filtration and absorption processes
Although exchange can occur through bulk flow, the primary result of bulk flow is the _______\_and, thus, ___________\_.
Although exchange can occur through bulk flow, the primary result of bulk flow is the distribution of interstitial fluid and, thus, extracellular fluid (ECF).
The Starling forces for bulk flow include
- _____________,
- ____________,
- ____________, and
- ____________\_
The Starling forces for bulk flow include
- capillary hydrostatic pressure,
- interstitial fluid oncotic pressure,
- capillary oncotic pressure, and
- interstitial fluid hydrostatic pressure
Capillary hydrostatic pressure (PCAP) is the ________\_, and has an average value of 38 mmHg at the _______\_ and 16 mmHg at the ______\_
Capillary hydrostatic pressure (PCAP) is the blood pressure of the capillary, and has an average value of 38 mm Hg at the arteriole end and 16 mm Hg at the venule end
Interstitial fluid oncotic pressure (πIF) results from proteins in the interstitial fluid and, under normal conditions, is 0 mm Hg.
Why is it 0mmHg under normal conditions?
Interstitial fluid oncotic pressure (πIF) results from proteins in the interstitial fluid and, under normal conditions, is 0 mm Hg.
Is 0mmHg under normal conditions because under normal conditions there aren’t many proteins in the interstitial fluid.
Both capillary hydrostatic pressure and interstitial fluid oncotic pressure act on _____________\_
Both capillary hydrostatic pressure and interstitial fluid oncotic pressure act on filtration across the capillary beds.
Capillary oncotic pressure (πCAP) results from __________\_ and has an average value of 25 mm Hg
Capillary oncotic pressure (πCAP) results from protein in the plasma of the capillary and has an average value of 25 mm Hg
Interstitial fluid hydrostatic pressure (PIF) is _________________\_, has an average value ranging from 0 to 1 mm Hg.
Interstitial fluid hydrostatic pressure (PIF) is the pressure exerted by the fluid in the interstitial space, has an average value ranging from 0 to 1 mm Hg.
Both capillary oncotic pressure and interstitial fluid hydrostatic pressure act on ____________\_
Both capillary oncotic pressure and interstitial fluid hydrostatic pressure act on absorption across the capillary beds.
The image shows Starling forces across a capillary wall:
The four Starling forces are depicted across a capillary wall:
- ___________\_and _________\_ favour filtration,
whereas
- _________\_and _________\_ favour absorption.
The image shows Starling forces across a capillary wall:
The four Starling forces are depicted across a capillary wall:
- Capillary hydrostatic pressure (PCAP) and interstitial fluid oncotic pressure (pIF) favour filtration,
whereas
- interstitial fluid hydrostatic pressure (PIF) and capillary oncotic pressure (pCAP) favour absorption.
The net filtration pressure (NFP) is determined by: ___________\_
And has the equation:
NFP = (PCAP + πIF) – (πCAP + PIF)
The net filtration pressure (NFP) is determined by: totalling the forces favouring filtration and subtracting the forces favouring absorption
And has the equation:
NFP = (PCAP + πIF) – (πCAP + PIF)
Net filtration pressure is equal to (Capillary hydrostatic pressure + Interstitial fluid oncotic pressure) - (Capillary oncotic pressure + Interstitial fluid hydrostatic pressure)
Arteriole end NFP = (38 mm Hg + 0 mm Hg) – (25 mm Hg + 1 mm Hg) = 12 mm Hg
Venule end NFP = (16 mm Hg + 0 mm Hg) – (25 mm Hg + 1 mm Hg) = –10 mm Hg
What does this mean for the movement of solutes and fluids at the arteriole end of the capillary bed?
Vs the movement of solutes and fluids at the venule end?
At the arteriole end of the capillary bed, there is an NFP of 12 mm Hg, which causes movement of solutes and fluids out of the capillary and into the interstitial space (filtration).
At the venule end, there is an NFP of –10 mm Hg, which causes movement of solutes and fluids back into the capillary from the interstitial space (absorption).
The NFP favouring filtration at the arteriole end is ____\_than the NFP favouring absorption at the venule end; thus, net ___\_ occurs across a capillary bed. Under normal circumstances, approximately 3 L of fluid is filtered across the capillary beds of the body per day.
What happens to excess filtrate?
The NFP favouring filtration at the arteriole end is greater than the NFP favouring absorption at the venule end; thus, net filtration occurs across a capillary bed. Under normal circumstances, approximately 3 L of fluid is filtered across the capillary beds of the body per day.
Excess filtrate is returned to the circulatory system by the lymphatic system.
The lymphatic system includes _______,_______,and _____\_, such as the ____ and ______.
The lymphatic system includes lymph vessels, lymph nodes, and organs, such as the spleen and thymus.
What function does the lymphatic system serve in each of the following systems?
- The immune system: _________
- The Digestive system: ________
- The Vascular System: _________
- The immune system: An important role in immunity
- The Digestive system: transport of absorbed fat
- The Vascular System: return of filtered fluid and protein from capillary beds
Unlike the vascular system, the lymphatic system is an ___\_circuit in which lymph vessels originate as _______\_, which are next to capillaries, and merge into larger and larger lymph vessels, which eventually drain the lymph into ________\_entering the _______\_.
Unlike the vascular system, the lymphatic system is an open circuit in which lymph vessels originate as initial lymphatics, which are next to capillaries, and merge into larger and larger lymph vessels, which eventually drain the lymph into venous circulation entering the right atrium.
The metarterioles of the capillary beds branch into venules, which begin the process of returning blood to the heart.
The metarterioles of the capillary beds branch into venules, which begin the process of returning blood to the heart.
In general and in comparison to arterioles, the venules are ____\_and have less ________\_
In general and in comparison to arterioles, the venules are smaller in diameter and have less smooth muscle in their walls
Can the exchange of solutes and fluids btwn blood and interstitial fluid occur at the venules? If so, how does it compare to exchange at the capillaries?
Some exchange of solutes and fluids can occur at the venule but to a much lesser extent than occurs across the capillaries
The venules branch into ___\_ upon leaving the organ or tissue
The venules branch into veins upon leaving the organ or tissue
What is the function of veins?
Veins carry blood back to the heart
What is the purpose of valves within the veins?
Valves ensure that the flow of blood is unidirectional (prevent backflow)
Veins have a larger diameter. What does this mean about the resistance in veins?
The large diameter means there is less resistance to bloodflow.
Unlike arteries, veins are high-compliance vessels, allowing ________________\_. As such, veins function as _____\_ reservoirs.
Unlike arteries, veins are high-compliance vessels, allowing little change in pressure with large changes in volume. As such, veins function as blood reservoirs.
What is venous return?
The amount of blood that is returned to the atrium per minute by the veins
In the systemic circuit, the driving force for venous return is ______________\_
In the systemic circuit, the driving force for venous return is central venous pressure (CVP)
What is central venous pressure?
Pressure in the vena cava leading into the right atrium
A decrease in venous return results in
- a decrease in _______
- a decrease in _______
- decrease in ________
- decrease in _______
- finally, a decrease in ______ to the organs and tissues
A decrease in venous return results in
- a decrease in end diastolic volume(EDV)
- a decrease in Stroke volume
- decrease in Cardiac output (CO)
- decrease in Mean arterial pressure (MAP)
- finally, a decrease in Blood flow to the organs and tissues
What are the five primary factors that influence (central venous pressure) CVP and venous return?
- Sympathetic nervous system activity
- Skeletal muscle pump
- Respiratory pump
- Cardiac suction
- Blood volume
An increase in sympathetic nervous system activity results in _______\_and thus _____\_ venous return
An increase in sympathetic nervous system activity results in venous vasoconstriction and thus increases venous return
How does venous vasoconstriction affect resistance?
Unlike the arterioles, the veins are not muscular and have little tone under basal conditions; thus, venous vasoconstriction does not significantly increase resistance
What is venous capacity and how is it linked venous vasoconstriction and venous return?
Venous capacity is the volume of blood that the veins can accommodate.
An increase in venous vasoconstriction increases venous return by decreasing venous capacity.
How does skeletal muscle activity effect blood flow back to the heart? Why are the valves important?
Skeletal muscle activity increases pressure in the veins and thus increases blood flow back to the heart. The one-way valves in the veins prevent blood from moving backwards or away from the heart.
What is the respiratory pump and how does it effect venous return?
The respiratory pump results from pressure changes in the thoracic and abdominal cavities during inspiration. As atmospheric air is inhaled during inspiration, there is a decrease in pressure in the thoracic cavity and an increase in pressure in the abdominal cavity, which act together to create a pressure gradient that favours movement of blood toward the thoracic cavity. This increase in CVP results in an increase in venous return with inspiration.
What is Cardiac suction and how does it affect venous return?
Cardiac suction results from pressure changes in the chambers of the heart during the cardiac cycle.
- With ventricular contraction, the small increase in volume of the atrial chambers transiently decreases atrial pressure to less than 0 mm Hg and thus favours venous return.
- With ventricular relaxation, the increase in volume of the ventricular chambers transiently decreases ventricular pressure to less than 0 mm Hg and thus also favours venous return.
Changes in blood volume are directly related to changes in ____\_ and thus influence venous return.
For example, an increase in blood volume will ____\_CVP and thus _____\_ venous return. In contrast to the other four factors that affect venous return, blood volume is used to influence venous return and MAP over the long term.
Changes in blood volume are directly related to changes in CVP and thus influence venous return.
For example, an increase in blood volume will increase CVP and thus increase venous return. In contrast to the other four factors that effect venous return, blood volume is used to influence venous return and MAP over the long term.
Chart
chart
The body homeostatically regulates blood pressure by monitoring __________\_
The body homeostatically regulates blood pressure by monitoring mean arterial pressure (MAP)
MAP is determined by ______\_and ________\_
MAP is determined by cardiac output (CO) and total peripheral resistance (TPR)
MAP=CO x TPR
CO is determined by _____\_ and _______.
TPR is determined by ______\_and ______\_.
The relationship between these factors and their determinants, as well as their collective influence on MAP, is outlined in the following flow chart.
CO is determined by heart rate and stroke volume. TPR is determined by arteriolar radius and blood viscosity. The relationship between these factors and their determinants, as well as their collective influence on MAP, is outlined in the following flow chart.
Hypotension refers to a MAP that is ____\_than normal and may result in ____________\_
Hypotension refers to an MAP that is less than normal and may result in inadequate blood flow to the tissues and organs
Hypertension refers to a MAP that is ____\_than normal and may result in _________________\_
Hypertension refers to a MAP that is greater than normal and may result in damage to the heart and vasculature.
Mean arterial pressure MAP is extrinsically regulated through control of both __________ and ___________.
Mean arterial pressure MAP is extrinsically regulated through control of both Cardiac Output (CO) and Total Peripheral Resistance (TPR).
Mean Arterial pressure is regulated extrinsically through ______ and ______
Mean Arterial pressure is regulated extrinsically through cardiac output and Total peripheral resistance
Short-term regulation of Mean Arterial Pressure is mediated by what?
The Baroreceptor complex
What is the baroreceptor complex?
Arterial baroreceptors (mechanoreceptors ie respond to stretch) found in the carotid sinus and aortic arch that detect changes in Mean Arterial pressure.
Short-term control of map
Arterial baroreceptors provide _____\_information to the cardiovascular control centre in the _____\_ of the _______, which then sends _____\_ information through the autonomic nervous system (ANS) to the heart and vasculature
Arterial baroreceptors provide afferent information to the cardiovascular control centre in the medulla of the brain stem, which then sends efferent information through the autonomic nervous system (ANS) to the heart and vasculature
Both divisions of the ANS—the sympathetic and parasympathetic nervous systems—influence MAP, as outlined in the following flow chart.
The direct determinants of mean arterial blood pressure (MAP) are _______\_(1) and _______\_ (1)
The direct determinants of mean arterial blood pressure (MAP) are cardiac output (CO) (1) and total peripheral resistance (TPR) (1)
CO is determined by ________ (2) and ________ (2)
CO is determined by heart rate (2) and stroke volume (2)
Heart rate is influenced by both ___________ (3) which decreases Heart rate, and __________ and ________ (4) which increases heart rate
Heart rate is influenced by both parasympathetic activity (3) and sympathetic activity and epinephrine (4), which are responsible for decreasing and increasing heart rate, respectively
Stroke volume is influenced by ________ (5) and ________(6).
Stroke volume ________ in response to an increase in sympathetic activity as well as an increase in venous return.
Stroke volume is influenced by sympathetic activity (5) and venous return (6).
Stroke volume increases in response to an increase in sympathetic activity as well as an increase in venous return.
Venous return is influenced by _______________\_(7), the _______________\_ (8), the__________________(9), _______________\_(10) and _______________\_ (11)
Venous return is influenced by sympathetically induced venous vasoconstriction (7), the skeletal muscle pump (8), the respiratory pump (9), cardiac suction (10) and circulating blood volume (11)
Blood volume is determined by _________________________(12) in the short term and __________ (13) in the long term
Blood volume is determined by passive bulk-flow fluid shifts between vascular and interstitial fluid compartments (12) in the short term and salt and water balance (13) in the long term
Salt and water balance in the body are regulated by the ________________\_and ______\_ (14), respectively
Salt and water balance in the body are regulated by the rennin-angiotensin-aldosterone system and vasopressin (14), respectively
TPR is determined by __________ (15) and __________ (15)
TPR is determined by the radius of all arterioles (15) and blood viscosity (15)
Blood viscosity is primarily dependent upon the __________(16)
Blood viscosity is primarily dependent upon the number of red blood cells (16) in blood
Arteriolar radius is influenced by__________ (17) [which match blood flow with metabolic need by altering arteriolar radius] and by ____________ (20)
Arteriolar radius is influenced Local metabolic controls (17) [which match blood flow with metabolic need by altering arteriolar radius] and by Extrinsic control through vasoconstriction (20)
Local metabolic controls (17) match blood low with metabolic need by altering arteriolar radius. An example of this is ________\_(18)
Local metabolic controls (17) match blood low with metabolic need by altering arteriolar radius. An example of this is skeletal muscle activity (18)
Extrinsic vasoconstriction results from __________\_(19) and the hormones ___________\_ (21)
Extrinsic vasoconstriction results from sympathetic nervous system activity and epinephrine (19) and the hormones vasopressin and angiotensin II (21)
Long-term regulation of Mean Arterial Pressure (MAP) occurs over a period of minutes to days and is achieved through
Long-term regulation of Mean Arterial Pressure (MAP) occurs over a period of minutes to days and is achieved through regulation of blood volume.
Can the baroreceptor reflex correct Mean Arterial Pressure?
The baroreceptor reflex can compensate for changes in MAP, but cannot ultimately correct MAP.
