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BIOA02 > Lecture 5: The Circulatory System > Flashcards

Lecture 5: The Circulatory System Flashcards

1
Q

the series of vessels are all connected and the circulatory fluid is blood

A

closed circulatory systems

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2
Q

Blood flows from the heart to arteries to capillaries to veins back to the heart again.

There can either be a SINGLE CIRCUIT such as the circulatory system in water-breathing fish (the middle diagram below) or MULTIPLE CIRCUITS in which blood flows first through one circuit and then the next (see the human circulatory system for a good example of multiple circuits).

A

Blood Flow

Heart -> arteries -> capillaries -> veins -> heart

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3
Q

Advantage of closed circulatory systems:

A

Being high pressure systems:
high blood pressure -> high levels of blood flow to tissues -> high levels of oxygen and nutrient delivery

Also allow for blood to be directed to specific organs; possibility to regulate
blood flow to individual organs; increasing or decreasing flow as required

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4
Q

the circulatory fluid is haemolymph in this system

A

open circulatory system

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5
Q

a mixture of blood and extracellular fluid

A

haemolymph

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6
Q

In open systems the blood vessels (i.e., arteries, capillaries and veins) DO NOT form a complete enclosed circuit starting and ending at the heart.

Rather, the haemolymph
is pumped from…

A

from the heart into arteries -> dumped into body cavity or sinuses in tissues -> picked up by veins and return back to heart

It is then “dumped” into the body cavity or sinuses in the tissues before being picked up by veins and returned to the heart.

Given that there is a lack of a complete enclosed circuit, open circulatory systems are low pressure systems meaning that blood flow to organs
is not as fast or efficient as seen in closed circulatory systems.

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7
Q

high pressure systems

A

closed

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8
Q

low pressure systems

A

open

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9
Q

The human/mammalian heart consists of two ventricles (left and right) and two atria (left and right).

The left side:

The right side:

A

The left side of the heart = high pressure pump that pumps oxygenated blood to the systemic tissues.

The right side of the heart = low pressure pump that pumps deoxygenated blood to the lungs.

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10
Q

Mammalian Heart:

Movement of oxygenated blood into the heart

A

returning to the heart from the LUNGS enters the LEFT ATRIA via PULMONARY VEINS

It then moves through an atrioventricular (AV) valve into the LEFT VENTRICLE. (Blood in)

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11
Q

Mammalian Heart:

Movement of deoxygenated blood into the heart

A

returning to the heart from the SYSTEMIC CIRCULATION (all organs not including the
lungs)

Enters the RIGHT ATRIA through the SUPERIOR AND INFERIOR VENA CAVA

It then moves through an 
atrioventricular valve (AV) into the RIGHT VENTRICLE. (Blood in)
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12
Q

Mammalian Heart:

Movement of oxygenated blood out of heart

A

leaves the LEFT VENTRICLE through a semilunar valve and enters the aorta (Blood out)

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13
Q

Mammalian Heart:

Deoxygenated blood out of heart

A

leaves the RIGHT VENTRICLE through a semilunar valve and enters the pulmonary
arteries (Blood out)

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14
Q

There are valves that separate the atria and the ventricles called

A

They are called atrioventricular valves (AV)

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15
Q

separate the left ventricle from the aorta and the right ventricule from pulmonary artery

A

semilunar valves

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16
Q

The Human/Mammalian Circulation

A

Deoxygenated blood → Superior and Inferior Vena Cava → Right Atria → Right
Ventricle → Pulmonary Arteries → Lung → Oxygenated Blood → Pulmonary Veins →
Left Atria → Left Ventricles → Aorta → Systemic Tissues → Deoxygenated Blood

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17
Q

Question: The pulmonary artery is the only artery in the body that carries deoxygenated blood and the
pulmonary vein is the only vein that carries oxygenated blood? What is the reason for this?

A

(hint: think

nomenclature rather than physiological processes).

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18
Q

Mammalian Fetal Circulation

The mammalian fetus receives blood from the

A

placenta

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19
Q

Mammalian Fetal Circulation

From the placenta, blood flows, via the
_______, into the _______ of the fetus.

A

umbilical vein to right atria of fetus

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20
Q

Mammalian Fetal Circulation
In utero, the fetal lungs are breathing ______
rather than air.

As such, the lungs are not involved in obtaining oxygen.

As a result of this, there is no
point sending blood to the lungs (there is no oxygen there to move into the blood).

A

amniotic fluid

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21
Q

Mammalian Fetal Circulation

Therefore, just like the diving crocodile (see below), blood is shunted away from the lungs. This is done by two processes.

A

First, blood flowing into the right atria (from the umbilical vein) is not sent to the right ventricle (at
least not all of it). Rather, it is shunted through a “hole-in-the-heart” called the foramen ovale into the left atria. Therefore, it avoids being sent to the lungs.

Second, any blood that didn’t get shunted from the right atria to left atria through the foramen ovale
(and instead moved from right atria to right ventricle to pulmonary artery) gets shunted through the ductus arteriosus into the aorta. The ductus arteriosus is a hole between the pulmonary artery and the aorta.

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22
Q

Mammalian Fetal Circulation

Both the foramen ovale and the ductus arteriosus serve to reduce or prevent blood flow to the lungs
because there is no oxygen (or air) in the lungs.

Both the foramen ovale and the ductus arteriosus close immediately at birth due to a complex series of changes in blood pressure and blood flow resistance that are triggered once the lungs start to breath air rather than amniotic fluid.

A

Foramen Ovale and Ductus Ateriosus

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23
Q

Cephalopod Circulatory Systems

In cephalopods (squid and octopi), deoxygenated blood is pumped via two branchial hearts across the gills where it is oxygenated.

A

Oxygenated blood then flows to the systemic heart which pumps it to the systemic circulation. This circulatory system is functionally similar to that of a mammal. The branchial hearts are the equivalent of the right side of the mammalian heart (pumping deoxygenated blood to the gas exchange organ – the gills for cephalopods; lungs for mammals). The systemic heart is similar to the left side of the mammalian heart, pumping oxygenated blood to the systemic tissues.

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24
Q

Cephalopod Circulatory Systems

Question: Why are both the oxygenated and deoxygenated blood blue (albeit different shades of blue)?

A

Concentration of oxygen

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25
Q

The Fish Heart

The (water-breathing) fish heart consists of ___ chambers in series (i.e., one following the other).

Venous (deoxygenated) blood enters the heart through the sinus venosus. Although considered to be part of the heart, the sinus venosus is technically part of the venous system. Blood then flows through the
sinoatrial valve into the atrium (a very thin-walled chamber).

Blood then passes through the
atrioventricular valve into a muscular ventricle. Finally blood moves through the bulbal valve into
the bulbus arteriosus.

A

4 chambers

26
Q

The Fish Heart

The atrium and the ventricle are both contractile but most of the contractile force arises from the
ventricle. The bulbous arteriosus can also be considered as part of the arterial system.

It functions as a _______. This means that it expands (fills with blood and bulges outward) when the heart is contracting and then collapses back into its initial “shape” when the heart is relaxing. This helps force blood through the arteries when the heart is relaxing

A

Windkessel vessel

27
Q

The Fish Heart

Question: What blood vessel in humans serves the same purpose as the bulbous arteriosus, i.e., acts as a Windkessel vessel?

A

Answer?

28
Q

Circulation in Gill (Water) Breathing Fish

Deoxygenated blood

A

Deoxygenated blood from the tissues (systemic circulation) returns to the heart through the venous
system. It is then pumped through the ventral aorta (VA) to the gills where it is oxygenated.

29
Q

Circulation in Gill (Water) Breathing Fish

Oxygenated blood

A

Oxygenated blood leaves the gills via the dorsal aorta (DA) and flows into the systemic circulation.
The circulation is therefore a single loop – heart to VA to gills to DA to systemic circulation (arteries
then veins) back to the heart.

30
Q

Circulation in Gill (Water) Breathing Fish

Blood must be pumped across two capillary beds______

Therefore, the heart must generate sufficient pressure to drive the blood through the entire circuit while simultaneously having a low enough pressure to prevent pressure-induced damage to the delicate gill tissue.

A

capillaries in the gills and capillaries in the systemic circulation.

31
Q

Circulation in the Lungfish

Although the lungfish is a fish, its circulatory system resembles that of a _____ much more than it
resembles the circulation of a “regular” fish.

A

resembles more of a mammal

32
Q

Circulation in the Lungfish

Deoxygenated blood

A

Deoxygenated blood returns to the heart from the tissues (i.e., the systemic circulation). It is then
pumped through the gills to a pulmonary artery (PA) and then into the lungs where it is oxygenated. It
then returns to the left side of the heart.

33
Q

Circulation in the Lungfish

Oxygenated blood

A

Oxygenated blood returns to the heart from the lungs. It is then pumped through the gills to the dorsal
aorta (DA) and then to the systemic circulation (tissues) where it supplies oxygen to the tissues and
becomes deoxygenated.

34
Q

Circulation in the Lungfish

Although the heart is not completely divided like a mammalian or avian heart, it functions as if it were
divided.

A

RIGHT SIDE
The right side of the heart receives deoxygenated blood from the systemic circulation

LEFT SIDE
left side of the heart receives oxygenated blood from the lungs.

Note that the gills play very little role in gas exchange (i.e., O2 uptake from the water or CO2 excretion into the water) since they are much reduced in size.

35
Q

Exercise: Compare the lungfish circulation to that of a human and convince yourself that, despite some anatomical differences, they are basically the same.

A

Try it!

36
Q

The Amphibian Heart and Circulation

Deoxygenated blood

A

from the tissues enters the sinus venous (part of the venous system) and then flows into the right atria. From there it enters the ventricle and then the conus arteriosus. This deoxygenated blood then flows through the pulmocutaneous arteries to the lungs and the skin.

Within the lungs and skin, blood picks up oxygen (becomes oxygenated) and also loses CO2.

37
Q

The Amphibian Heart and Circulation

Oxygenated blood

A

from the lungs returns to the left atria via the pulmonary vein. It then enters the
ventricle and the conus arteriosus before moving through the systemic arteries to the tissues
(systemic circulation) where it gives up oxygen to the tissues and picks up CO2 (a waste product of
metabolism).

38
Q

The Amphibian Heart and Circulation

Both oxygenated blood returning to the left atria and deoxygenated blood returning to the right atria
move into the single ventricle.

A

It would appear, at least at first glance, that this is inefficient because the
oxygenated and deoxygenated blood would mix within the ventricle. In reality, very little mixing
occurs. There are anatomical features of the ventricle and the conus arteriosus that prevent this. In addition, slight differences in the timing of contraction of the right and left atria also help prevent this (the details aren’t important).

As a result, oxygenated blood that enters the left atria at a concentration of 8.6 vol% ends up flowing to the tissues (via the systemic arteries) at a concentration of 8.0 vol%. **In other words, there was very little mixing with the deoxygenated blood that caused a large decrease in oxygen.

The same is true on the right side. Deoxygenated blood enters the right atria at a concentration if 4.2
vol% and leaves via the pulmocutaneous arteries (to the lungs and skin) at a concentration of 4.4 vol%.
**Again, there is very little mixing of this deoxygenated blood with the oxygenated blood.

39
Q

The Amphibian Heart and Circulation

The amphibian heart consists of ___ chambers.

A

Three Chambers

There is a left atrium and a right atrium; as well as a single ventricle.

Blood enters the single ventricle from the two atria. It then leaves the ventricle via the conus
arteriosus. The conus arteriosus divides into a main branch going to the left and a main branch going to right. Both of these branches then divide into a pulmocutaneous artery that goes to the skin and lungs as well as a series of systemic arteries (i.e., subclavian and carotid) that go to the systemic tissues.

40
Q

Reptilian Hearts

Reptilian hearts have _____ (how many atria/ventricles)

A

two atria and two ventricles.

However, in non-crocodilian reptiles such as lizards, snakes and turtles, the ventricles are not completely divided (i.e., there is a connection between the left and right ventricle such that blood can move between the two ventricles). In crocodilian reptiles the
two ventricles are completely separate.

Blood cannot move from one ventricle into the other ventricle.

41
Q

Reptilian Hearts

Reptilian hearts have ______ that arise directly from the ventricles. There is a pulmonary
artery that transports blood to the lungs and two aorta that transport blood to the systemic circulation.

A

three blood vessels

42
Q

Reptilian Hearts

Deoxygenated blood

A

from the tissues enters the right atrium. It will then move into the ventricles and ultimately be pumped to the lungs.

43
Q

Reptilian Hearts

Oxygenated blood

A

from the lungs enters the left atrium. It will then move into the ventricles and
ultimately be pumped through the aorta to the systemic circulation.

*There is one (not important) exception to the two statements above. In the turtle, the left aorta actually
receives deoxygenated blood rather than oxygenated blood.

44
Q

The Crocodilian Heart

The crocodilian heart has _____

A

two atria (left and right) and two ventricles (left and right).

The ventricles are completely divided into a left ventricle and a right ventricle.

45
Q

The Crocodilian Heart

There is a pulmonary artery that leaves the right ventricle. It carries _____ blood to the
lungs.

A

deoxygenated

46
Q

The Crocodilian Heart

There is also a left aorta (systemic arch) that leaves the right ventricle. There are times when the left
aorta is closed and no blood flows through it. However, when the left aorta is open, it carries
_____ blood to the systemic tissues.

A

deoxygenated

47
Q

The Crocodilian Heart

The right aorta (systemic arch) leaves the ____ ventricle.

A

left

48
Q

The Crocodilian Heart

There is a valve that separates the _____ from the _____.

There is also a valve that separates
the left ventricle from the right aorta.

A

right ventricle from the left aorta

49
Q

The Crocodilian Heart

A connection between the right aorta and the left aorta called the

A

Foramen of Panizza.

50
Q

Blood Flow from the Crocodilian Heart during Normal Breathing

When a crocodile is on the surface breathing (air) normally, there is very little resistance to blood flow in the pulmonary artery (PA) that flows to the lungs (1). Therefore, deoxygenated blood flows from the right ventricle (RV) to the lungs via the pulmonary artery (2). At this time, the pressure in the right ventricle (RV) is less than the pressure in the left aorta (LA; 3). This keeps the valve that separates the right ventricle (RV) from the left aorta (LA) closed (4). Oxygenated blood from the left ventricle (LV) flows into the right aorta (RA), and to some extent, through Foramen of Panizza, into the left aorta (5).

Under these circumstances, the crocodilian heart is functioning just a like a human heart would.

A

Review!

51
Q

Blood Flow from the Crocodilian Heart during Normal Breathing

Deoxygenated blood

A

has returned from the systemic circulation to the right atria. It flows into the right ventricle and is pumped to the lungs via the pulmonary artery (PA)

52
Q

Blood Flow from the Crocodilian Heart during Normal Breathing

Oxygenated blood

A

has returned from the lungs to the left atria. It flows into the left ventricle and is
pumped to the systemic circulation via the right aorta (RA) and to a lesser extent via the left aorta (LA).
The only difference between the human and crocodile at this stage is that blood is flowing to the
systemic circulation via two aorta (crocodile) instead of one aorta (human)

53
Q

Blood Flow from the Crocodilian Heart during Diving

When a crocodile dives underwater, it will not breathe (there is no point breathing if you are
underwater and can’t get air into the lungs). This causes blood vessels in the lungs as well as the
pulmonary artery to _____

A

constrict (i.e., narrow in diameter). This increases the resistance to blood flow
within the lungs and the pulmonary artery.

54
Q

Blood Flow from the Crocodilian Heart during Diving

As a result of the increase in resistance, flow to the lungs (via the pulmonary artery) is ______.

A

As a result of the increase in resistance, flow to the lungs (via the pulmonary artery) is REDUCED or STOPPED.

This causes a build-up of pressure in the right ventricle.

Pressure in the right ventricle
becomes greater than pressure in the left aorta.

This causes the valve between the right ventricle and left aorta to open.

Blood can then flow from the right ventricle to the left aorta.

55
Q

Blood Flow from the Crocodilian Heart during Diving

This means that blood is no longer flowing through the pulmonary artery to the lungs. Instead, blood
from the right ventricles that should have flown to the lungs now flows through the left aorta to the
systemic circulation.

This is called a

A

In other words, deoxygenated blood from the right ventricle is being recycled
back into the systemic circulation.

blood shunt.

56
Q

Blood Shunt

A

Blood on the right hand side of the heart (the right ventricle) is moved (or
shunted) to the left hand side (i.e., the left aorta). This is a right to left shunt.

57
Q

Cardiorespiratory Synchrony (Blood Shunts)

The recycling of blood mentioned above is an example of a blood shunt which in turn is an example of ______

A

cardiorespiratory (cardiovascular – respiratory) synchrony.

58
Q

Cardiorespiratory Synchrony (Blood Shunts)

In the example above (crocodile diving), blood flow to the lungs was reduced when the animal was underwater and therefore couldn’t breathe air. In this case there is no point sending any blood to the lungs because the lungs are not being filled with fresh air so there is no new oxygen to take from the lungs into the blood.

A

Blood was shunted away from the lungs.

59
Q

Cardiorespiratory Synchrony (Blood Shunts)

1) Ventilation (breathing). There are periods when the animal is breathing (the deflections in the trace)
and periods when the animal is not breathing (the flat lines; called apnea).

2) Pulmonary (lung) blood flow (i.e., blood flow through the pulmonary artery).
3) Systemic (systemic tissues) blood flow (i.e., blood flow through an aorta).
4) The ratio between pulmonary blood flow (Qpulm) and systemic blood flow (Qsys).

A

The major point here is that when the animal isn’t breathing (i.e., is underwater) both pulmonary blood
flow and systemic blood flow decrease.

However, the decrease in pulmonary blood flow is much more
pronounced than the decrease in systemic blood flow. As a result, the ratio of Qpulm to Qsys is reduced.
The reduction in this ratio indicates a significant reduction in blood flow to the lungs.

60
Q

Cardiorespiratory Synchrony (Blood Shunts)

This is an example of cardiorespiratory synchrony. When breathing stops, blood flow to the lungs is

A

reduced

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