Home
proprep logo
Ask A Tutor
Why Proprep
About usPress roomBlogSee how it works
LoginFor Educators
HomeQuestions & Answers

Question

Which valves are anchored by chordae tendineae and which valves close when the cusps fill with blood...

StudyStudyStudyStudy

Solution

VerifiedVerified Solution by Proprep Tutor

 

Understanding Heart Valves and Their Functions

The human heart is a muscular organ that pumps blood throughout the body via the circulatory system. It consists of four chambers: two atria (upper chambers) and two ventricles (lower chambers).

The human heart is a muscular organ that pumps blood throughout the body via the circulatory system. It consists of four chambers: two atria (upper chambers) and two ventricles (lower chambers).

To ensure unidirectional blood flow, the heart has four valves that open and close in response to blood flow and pressure.

Let's delve into the specifics of these valves and their associated structures.

 

1. Valves Anchored by Chordae Tendineae:

Chordae tendineae are fibrous cords that anchor the cusps (or leaflets) of the heart valves to the papillary muscles, which are located within the ventricles of the heart. These structures prevent the valves from inverting or prolapsing into the atria when the ventricles contract.

 

  • Mitral Valve (or Bicuspid Valve): This valve is located between the left atrium and the left ventricle. It has two cusps and is anchored by chordae tendineae to the papillary muscles of the left ventricle.

 

 

Flap opened in posterolateral wall of left ventricle

 

  • Tricuspid Valve: This valve is situated between the right atrium and the right ventricle. It has three cusps and is also anchored by chordae tendineae to the papillary muscles of the right ventricle.

 

Opened right ventricle: anterior view

 

2. Valves That Close When Their Cusps Fill with Blood:

All heart valves operate based on pressure differences and blood flow. When the pressure is greater behind a valve, it opens, and when the pressure is greater in front of the valve, it closes. The closing of the valves is essential to prevent backflow of blood.

  • Aortic Valve: Located between the left ventricle and the aorta, this valve closes when the left ventricle relaxes, preventing blood from flowing back into the ventricle from the aorta. This occurs in the systemic circulation.

 

Section through left atrium and ventricle with mitral valve cut away

 

  • Pulmonary Valve: Situated between the right ventricle and the pulmonary artery, this valve closes when the right ventricle relaxes, preventing backflow of blood from the pulmonary artery into the ventricle. This takes place in the pulmonary circulation.

 

 

  • Mitral and Tricuspid Valves: As mentioned earlier, these valves are anchored by chordae tendineae. They close when the ventricles contract, preventing the backflow of blood into the atria. The closure of these valves is what produces the first heart sound, often denoted as "lub."

 

3. Coronary Circulation:

The coronary circulation specifically refers to the blood supply to the heart muscle itself. The heart receives its nourishment from the coronary arteries.

The valves' function in the coronary circulation is indirectly related, as they ensure efficient blood flow through the heart, which in turn ensures that the coronary arteries receive blood during the relaxation phase of the cardiac cycle.

 

Conclusion:

In summary, the mitral and tricuspid valves are anchored by chordae tendineae. All heart valves, including the aortic and pulmonary valves, close when the pressure in front of them is greater than the pressure behind them, ensuring unidirectional blood flow. Proper functioning of these valves is crucial for the efficient circulation of blood in pulmonary, systemic, and coronary circulations.

 

Closed Circulatory Systems

Solved: Unlock Proprep's Full Access

Gain Full Access to Proprep for In-Depth Answers and Video Explanations

Signup to watch the full video 07:58 minutes

In our previous discussions of the circulatory system in the previous video,
we were talking about
open circulatory systems in organisms
that are not vertebrates or invertebrates of various sorts.
Now what we're doing is we're going to be turning our attention
to closed circulatory systems that are
going to be delivering blood in a much more controlled way than happens in open systems.
Now, vertebrate systems have a lot less variety than all the variety that we saw in
the previous video than those of invertebrates because the blood is pumped by a heart,
and does not normally fill the body cavity in these closed systems.
In addition to that,
there are specialized molecules,
the hemoglobin molecules in the blood,
which transport the oxygen.
In many vertebrates,
actually in addition to this circulatory system that we call the cardiovascular system,
there's another system that's called the lymphatic system,
which does not go through the heart that moves things around as well,
primarily cells that have to do with the immune system.
But we're not going to be looking at that here.
We're talking about vertebrates.
Let's start looking at fish.
At fish, they have the simplest circulatory system, the vertebrates,
and they have 1 circuit where the blood flows through the heart.
Here's the heart. Then it goes to
the area which does the gas exchange to the outside through the gills.
Of course, there are capillaries.
Now the blood is oxygenated,
and it moves back around into what's called the systemic circulation,
that's going to be the capillaries that are near the organs,
and then go through the veins back to the heart.
These organisms, these fish, have 1 circuit.
We'll see later that in many cases there are more than 1 circuit where
the blood flows in 1 direction from a 2-chambered heart.
Notice we have an atrium and we have a ventricle,
and we'll have that in more complicated hearts as well,
pushing in 1 direction.
This is only a 2-chambered heart.
We have gill circulation through the capillaries,
and we have systemic circulation through the body of the fish.
This case we do have unidirectional flow of blood,
and there is a gradient of oxygenated blood,
of course, through the system.
What's in the heart is going to be least oxygenated,
and what's coming out of the gills is going to be the most oxygenated.
The result of this system is that there is a limit in the amount of oxygen that can
reach some tissues of the body because it's only a single system.
This reduces the overall metabolic capacity of the fish
compared to more complicated plans like we can see here.
In other vertebrates, in amphibians, reptiles,
and birds, and of course in mammals,
there are 2 circuits.
There's what's called the pulmonary circulation.
In some amphibians, there's a gas exchange in addition to that through the skin.
There's pulmonary circulation and there is systemic circulation.
They are separated,
these 2 systems,
unlike the fish where it's all 1 system.
Getting back to a diagram which is similar to what we saw in the fish,
here we have the heart circulating blood
from the heart to the lungs and then back to the heart and we have
the heart circulating blood from the heart through
the systemic capillaries and then back to the heart into separate systems.
In amphibians, notice,
we don't have a 2-chambered heart like we did in fish,
rather we have a 3-chambered heart.
We have 2 atria up here,
and we have 1 large ventricle. What does that mean?
That means that the blood which is returning from the lungs is
also mixing with blood which is returning from the system.
It's mixing over here.
We'll see that in a second.
The atria receive blood from both the pulmonary and the systemic circulations.
Therefore, there's mixing of the oxygenated and deoxygenated blood in this 1 ventricle,
and that is going to reduce the efficiency of oxygenation,
of course, because it's mixing with the oxygenated.
However, in order to help out with this,
there is a ridge within the ventricle.
There's a ridge which is over here,
which helps direct the blood in the right direction so that it can get better oxygenated.
There is this ridge that diverts oxygen-rich blood to the systemic capillaries,
and the deoxygenated blood into the pulmonary circuit.
The advantage of this system, of course,
is that there's high pressure in the vessels that pushes blood both into the lungs,
and into the systemic capillaries.
That's the advantage over fish that only have
this 2-chamber system and don't have the 2 different separate systems.
Because of this, these 2 systems,
amphibians are often described as having double circulation.
Now in reptiles, they have a similar situation.
Also there are 2 atria and 1 ventricle.
Here's the 3-chambered heart.
However, there is again this partial septum,
and there's an additional artery that you can see
here which comes out and joins the systemic capillary.
In principle, it's really the same as in amphibians.
Reptiles and amphibians, of course,
are very closely related.
But there is a little bit of a change such
that they can deal with particular systems more efficiently.
For instance, alligators and crocodiles have something called a foramen of Panizza.
They have these 2 aortas.
They have the right one arising from the left ventricle and
the left one coming from the right ventricle,
as you can see here,
and they're connected by this foramen of Panizza as we said.
That allows blood from the right ventricle to bypass
the pulmonary circulation when the animal is submerged.
When the animal is submerged and can't breathe,
the alligators and crocodiles,
then the pulmonary section is shut down by a particular kind of valve.
Therefore it continues moving blood around into its extremities,
but not through the lungs,
which are non-functional because the animal is submerged.
This video discusses the differences between open and closed circulatory systems, and the various types of closed circulatory systems found in vertebrates. It focuses on the circulatory systems of fish, amphibians, reptiles, and birds and mammals. Fish have the simplest circulatory system, with one circuit of blood flowing through the heart, gills, and systemic capillaries. Amphibians and reptiles have a three-chambered heart, with two atria and one ventricle, and a partial septum that helps direct oxygen-rich blood to the systemic capillaries. Alligators and crocodiles have a foramen of Panizza that allows blood to bypass the pulmonary circulation when the animal is submerged.

Ask a tutor

If you have any additional questions, you can ask one of our experts.

Recently Asked Questions