Module 1: Vascular System 1.5-1.9

Question 1

Arterioles branch into _____\_, which function in the exchange of _____ and____\_ between the_____ and the ________\_.

Answer 1

Arterioles branch into capillaries, which function in the exchange of solutes and fluids between the blood and the interstitial fluid.

Question 2

Two important factors make capillaries the best location for diffusion:

1. Capillaries have a _________\_. As a result, erythrocytes (red blood cells) must flow through the capillaries _______\_.
2. 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.

Answer 2

Two important factors make capillaries the best location for diffusion:

1. 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.
2. 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.

Question 3

There are two types of capillaries

1. _______
2. _______

Answer 3

There are two types of capillaries:

1. Fenestrated
2. Continuous

Question 4

Continuous capillaries, the most common type, allow only ___________\_to move through the intercellular spaces between the _________\_

Answer 4

Continuous capillaries, the most common type, allow only small water-soluble molecules to move through the intercellular spaces between the capillary endothelial cells.

Question 5

Where would you find fenestrated capillaries?

Answer 5

kidneys, liver, intestines and bone marrow

Question 6

What is important about fenestrated capillaries and where they are located?

Answer 6

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)

Question 7

Capillaries extend from ______ which are vessels connecting the arterioles to the venules

Answer 7

Capillaries extend from metaarterioles which are vessels connecting the arterioles to the venules

Question 8

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.

Answer 8

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.

Question 9

Solutes and fluids move across the capillary walls by

1. _______,
2. _______, or
3. _______

Answer 9

Solutes and fluids move across the capillary walls by

1. diffusion,
2. transcytosis, or
3. mediated transport

Question 10

Diffusion of lipophilic molecules occurs __________\_the capillary endothelial cell, whereas diffusion of lipophobic molecules occurs _________\_ the capillary endothelial cells

Answer 10

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

Question 11

What is transcytosis? How is it used in the capillary beds?

Answer 11

Transcytosis is a form of vesicular transport.

In capillaries, larger lipophobic molecules can cross the capillary endothelial cells via transcytosis

Question 12

Mediated transport requires ______\_ specific to the molecule to be transported

Answer 12

Mediated transport requires transport proteins specific to the molecule being transported

Question 13

Mediated transport is primarily used in which organ?

Answer 13

Primarily used for transport across the capillaries of the brain.

Question 14

The primary mechanism of exchange across the capillaries (excluding the capillaries of the brain) is by ______\_.

Answer 14

The primary mechanism of exchange across the capillaries (excluding the capillaries of the brain) is by diffusion.

Question 15

The secondary mechanism of exchange occurs through _______\_ across the capillary wall

Answer 15

The secondary mechanism of exchange occurs through bulk flow of solutes and fluids across the capillary wall

Question 16

Bulk flow occurs as the result of ________\_—determined by the ____\_ forces—and involves both ____\_and ____\_ processes

Answer 16

Bulk flow occurs as the result of pressure gradients—determined by the Starling forces—and involves both filtration and absorption processes

Question 17

Although exchange can occur through bulk flow, the primary result of bulk flow is the _______\_and, thus, ___________\_.

Answer 17

Although exchange can occur through bulk flow, the primary result of bulk flow is the distribution of interstitial fluid and, thus, extracellular fluid (ECF).

Question 18

The Starling forces for bulk flow include

1. _____________,
2. ____________,
3. ____________, and
4. ____________\_

Answer 18

The Starling forces for bulk flow include

1. capillary hydrostatic pressure,
2. interstitial fluid oncotic pressure,
3. capillary oncotic pressure, and
4. interstitial fluid hydrostatic pressure

Question 19

Capillary hydrostatic pressure (PCAP) is the ________\_, and has an average value of 38 mmHg at the _______\_ and 16 mmHg at the ______\_

Answer 19

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

Question 20

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?

Answer 20

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.

Question 21

Both capillary hydrostatic pressure and interstitial fluid oncotic pressure act on _____________\_

Answer 21

Both capillary hydrostatic pressure and interstitial fluid oncotic pressure act on filtration across the capillary beds.

Question 22

Capillary oncotic pressure (πCAP) results from __________\_ and has an average value of 25 mm Hg

Answer 22

Capillary oncotic pressure (πCAP) results from protein in the plasma of the capillary and has an average value of 25 mm Hg

Question 23

Interstitial fluid hydrostatic pressure (PIF) is _________________\_, has an average value ranging from 0 to 1 mm Hg.

Answer 23

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.

Question 24

Both capillary oncotic pressure and interstitial fluid hydrostatic pressure act on ____________\_

Answer 24

Both capillary oncotic pressure and interstitial fluid hydrostatic pressure act on absorption across the capillary beds.

Question 25

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.

Answer 25

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.

Question 26

The **net filtration pressure (NFP)** is determined by: _\_\_\_\_\_\_\_\_\_\_\_\__ And has the equation: NFP = (PCAP + πIF) – (πCAP + PIF)

Answer 26

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)

Question 27

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?

Answer 27

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**).

Question 28

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?

Answer 28

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.

Question 29

The lymphatic system includes _\_\_\_\_\_\_\_,\_\_\_\_\_\_\_,and \_\_\_\_\_\__, **_s_**uch as the ____ _and \_\_\_\_\_\_._

Answer 29

The lymphatic system includes lymph vessels, lymph nodes, and organs, such as the spleen and thymus.

Question 30

What function does the lymphatic system serve in each of the following systems? 1. The immune system: \_\_\_\_\_\_\_\_\_ 2. The Digestive system: \_\_\_\_\_\_\_\_ 3. The Vascular System: \_\_\_\_\_\_\_\_\_

Answer 30

1. The immune system: _An important role in immunity_ 2. The Digestive system: _transport of absorbed fat_ 3. The Vascular System: _return of filtered fluid and protein from capillary beds_

Question 31

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 _\_\_\_\_\_\_\_\__.

Answer 31

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_.

Question 32

The metarterioles of the capillary beds branch into _venules_, which begin the process of returning blood to the heart.

Answer 32

The metarterioles of the capillary beds branch into _venules_, which begin the process of returning blood to the heart.

Question 33

In general and in comparison to arterioles, the venules are _\_\_\_\_\__and have less _\_\_\_\_\_\_\_\_\__

Answer 33

In general and in comparison to arterioles, the venules are _smaller in diameter_ and have less _smooth muscle in their walls_

Question 34

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?

Answer 34

Some exchange of solutes and fluids can occur at the venule but to a much lesser extent than occurs across the capillaries

Question 35

The venules branch into _\_\_\_\__ upon leaving the organ or tissue

Answer 35

The venules branch into _veins_ upon leaving the organ or tissue

Question 36

What is the function of veins?

Answer 36

Veins carry blood back to the heart

Question 37

What is the purpose of valves within the veins?

Answer 37

Valves ensure that the flow of blood is unidirectional (prevent backflow)

Question 38

Veins have a larger diameter. What does this mean about the resistance in veins?

Answer 38

The large diameter means there is less resistance to bloodflow.

Question 39

Unlike arteries, veins are **high-compliance** vessels, allowing _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\__. As such, veins function as _\_\_\_\_\_\__ reservoirs.

Answer 39

Unlike arteries, veins are **high-compliance** vessels, allowing _little change in pressure with large changes in volume_. As such, veins function as _blood_ reservoirs.

Question 40

What is venous return?

Answer 40

The amount of blood that is returned to the atrium per minute by the veins

Question 41

In the systemic circuit, the driving force for venous return is _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\__

Answer 41

In the systemic circuit, the driving force for venous return is _central venous pressure (CVP)_

Question 42

What is central venous pressure?

Answer 42

Pressure in the vena cava leading into the right atrium

Question 43

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

Answer 43

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

Question 44

What are the five primary factors that influence (central venous pressure) CVP and venous return?

Answer 44

1. Sympathetic nervous system activity 2. Skeletal muscle pump 3. Respiratory pump 4. Cardiac suction 5. Blood volume

Question 45

An increase in sympathetic nervous system activity results in _\_\_\_\_\_\_\_\__and thus _\_\_\_\_\_\__ venous return

Answer 45

An increase in sympathetic nervous system activity results in _venous vasoconstriction_ and thus _increases_ venous return

Question 46

How does venous vasoconstriction affect resistance?

Answer 46

Unlike the arterioles, the veins are not muscular and have little tone under basal conditions; thus, venous vasoconstriction does not significantly increase resistance

Question 47

What is venous capacity and how is it linked venous vasoconstriction and venous return?

Answer 47

Venous capacity is the volume of blood that the veins can accommodate. An increase in venous vasoconstriction increases venous return by _decreasing venous capacity_.

Question 48

How does skeletal muscle activity effect blood flow back to the heart? Why are the valves important?

Answer 48

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.

Question 49

What is the respiratory pump and how does it effect venous return?

Answer 49

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.

Question 50

What is Cardiac suction and how does it affect venous return?

Answer 50

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.**

Question 51

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**.

Answer 51

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**.

Question 52

Chart

Answer 52

Question 53

chart

Answer 53

Question 54

The body homeostatically regulates blood pressure by monitoring _\_\_\_\_\_\_\_\_\_\_\__

Answer 54

The body homeostatically regulates blood pressure by monitoring _mean arterial pressure (MAP)_

Question 55

MAP is determined by _\_\_\_\_\_\_\__and _\_\_\_\_\_\_\_\_\__

Answer 55

MAP is determined by _cardiac output (CO)_ and _total peripheral resistance (TPR)_ _MAP=CO x TPR_

Question 56

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.

Answer 56

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.

Question 57

Hypotension refers to a MAP that is _\_\_\_\_\__than normal and may result in _\_\_\_\_\_\_\_\_\_\_\_\_\__

Answer 57

Hypotension refers to an MAP that is less than normal and may result in inadequate blood flow to the tissues and organs

Question 58

Hypertension refers to a MAP that is _\_\_\_\_\__than normal and may result in _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\__

Answer 58

Hypertension refers to a MAP that is _greater_ than normal and may result in _damage to the heart and vasculature._

Question 59

Mean arterial pressure MAP is extrinsically regulated through control of _both __________ and \_\_\_\_\_\_\_\_\_\_\_._

Answer 59

Mean arterial pressure MAP is extrinsically regulated through control of _both Cardiac Output (CO) and Total Peripheral Resistance (TPR)._

Question 60

Mean Arterial pressure is regulated **extrinsically** through ______ and \_\_\_\_\_\_

Answer 60

Mean Arterial pressure is regulated extrinsically through _cardiac output_ and _Total peripheral resistance_

Question 61

Short-term regulation of Mean Arterial Pressure is mediated by what?

Answer 61

The Baroreceptor complex

Question 62

What is the baroreceptor complex?

Answer 62

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

Question 63

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

Answer 63

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

Question 64

Both divisions of the ANS—the sympathetic and parasympathetic nervous systems—influence MAP, as outlined in the following flow chart.

Answer 64

Question 65

The direct determinants of mean arterial blood pressure (MAP) are _\_\_\_\_\_\_\_\__(1) and _\_\_\_\_\_\_\_\__ (1)

Answer 65

The direct determinants of mean arterial blood pressure (MAP) are _cardiac output (CO_) (1) and _total peripheral resistance (TPR)_ (1)

Question 66

CO is determined by ________ (2) and ________ (2)

Answer 66

CO is determined by _heart rate_ (2) and _stroke volume (2)_

Question 67

Heart rate is influenced by both ___________ (3) which decreases Heart rate, and __________ and ________ (4) which increases heart rate

Answer 67

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

Question 68

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.

Answer 68

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.

Question 69

Venous return is influenced by _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\__(7), the _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\__ (8), the_**\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_**_(9), _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\__(10) and _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\__ (11)

Answer 69

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)

Question 70

Blood volume is determined by \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_(12) in the short term and __________ (13) in the long term

Answer 70

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

Question 71

Salt and water balance in the body are regulated by the _\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\__and _\_\_\_\_\_\_\__ (14), respectively

Answer 71

Salt and water balance in the body are regulated by the _rennin-angiotensin-aldosterone system and vasopressin_ (14), respectively

Question 72

TPR is determined by __________ (15) and __________ (15)

Answer 72

TPR is determined by _the radius of all arterioles_ (15) and _blood viscosity_ (15)

Question 73

Blood viscosity is primarily dependent upon the \_\_\_\_\_\_\_\_\_\_(16)

Answer 73

Blood viscosity is primarily dependent upon the _number of red blood cells (16) in blood_

Question 74

Arteriolar radius is influenced by\_\_\_\_\_\_\_\_\_\_ (17) [which match blood flow with metabolic need by altering arteriolar radius] and by ____________ (20)

Answer 74

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)

Question 75

Local metabolic controls (17) match blood low with metabolic need by altering arteriolar radius. An example of this is _\_\_\_\_\_\_\_\_\__(18)

Answer 75

Local metabolic controls (17) match blood low with metabolic need by altering arteriolar radius. An example of this is _skeletal muscle activity_ (18)

Question 76

Extrinsic vasoconstriction results from _\_\_\_\_\_\_\_\_\_\_\__(19) and the hormones _\_\_\_\_\_\_\_\_\_\_\_\__ (21)

Answer 76

Extrinsic vasoconstriction results from _sympathetic nervous system activity and epinephrine_ (19) and the hormones _vasopressin and angiotensin II_ (21)

Question 77

Long-term regulation of Mean Arterial Pressure (MAP) occurs over a period of minutes to days and is achieved through

Answer 77

Long-term regulation of Mean Arterial Pressure (MAP) occurs over a period of minutes to days and is achieved through _regulation of blood volume._

Question 78

Can the baroreceptor reflex correct Mean Arterial Pressure?

Answer 78

The baroreceptor reflex can _compensate_ for changes in MAP, but cannot ultimately correct MAP.