Learn how varicose veins can be caused. (A video from Beth Israel Deaconess Medical Center, Boston)

Bill Nye - Blood and Circulation Worksheet is a worksheet by Teach Science with Fergy for students to work through, along with the supplementary resources that you will find as part of this lesson

Bill Nye - Blood and Circulation Worksheet

Bill Nye - Blood and Circulation Worksheet with Answers is a worksheet by Teach Science with Fergy for students to work through, along with the supplementary resources that you will find as part of this lesson

Bill Nye - Blood and Circulation Worksheet with Answers

Circulatory System - Student Presentation 

Circulatory System - Teaching Presentation 

The circulatory system consisting of the heart, arteries, capillaries, and veins, is the pumping mechanism that transports blood throughout the body.

In the heart, the left ventricle contracts, pushing red blood cells into the aorta, the body's largest artery.  

From here, blood moves through a series of increasingly smaller arteries, until it reaches a capillary, the junction between arteries and veins.

Here oxygen molecules detach from the red blood cells and slip across the capillary wall into body tissue.  

Now de-oxygenated, blood begins its return to the heart.  

It passes through increasingly larger veins to eventually reach the right atrium.  

It enters the right ventricle, which pumps it through the pulmonary arteries into the lungs, to pick up more oxygen.  

Oxygenated, blood reenters the left atrium, moves into the left ventricle, and the blood's journey begins again.

CIRCULATION

(USMLE topics, cardiology) Pressure gradient, skeletal muscle pump, gravity, and respiratory pump . This video is available for instant download licensing here:  https://www.alilamedicalmedia.com/-/galleries/narrated-videos-by-topics/cardiac-physiology-no-ecg/-/medias/674e2423-a3f9-48ed-9ab4-879859d0d96a-mechanisms-of-venous-return-narrated-animation
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Voice by Ashley Fleming 

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All images/videos by Alila Medical Media are for information purposes ONLY and are NOT intended to replace professional medical advice, diagnosis or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition.
Venous return is the flow of blood from the periphery back to the heart’s right atrium. Venous return is important because the more blood returns to the heart, the more blood can be pumped out. In other words, venous return is the major determinant of cardiac output. 
Venous return is achieved by several mechanisms:
Pressure gradient: the difference between venous pressure and right atrial pressure is the major force driving peripheral blood back to the heart. In fact, venous return can be determined as the venous pressure gradient divided by venous resistance. Factors that increase venous pressure or decrease right atrial pressure, facilitate venous return. In principle, constriction of veins blocks blood flow, increases venous resistance and reduces venous return. However when blood vessels throughout the body are constricted, such as during sympathetic activation, the increased resistance causes blood pressure to rise, and this eventually overrides the increase in venous resistance. As a result, venous return increases.
Skeletal muscle pump: Veins in the arms and legs are surrounded by skeletal muscles. They also have one-way valves in their walls that only open for upward flow. During everyday activities, such as walking, the muscles contract and squeeze blood in the veins upward, toward the heart. The one-way valves prevent blood from flowing down again when the muscles relax. This is one of mechanisms by which physical exercise increases cardiac output to meet the body’s needs.
Gravity: In an upright position, venous blood from the head and neck flows downhill to the heart simply by gravity. Blood from the lower body and limbs, on the other hand, has to overcome gravity to return to the heart. People who stand or sit still for extended periods of time may suffer from venous blood pooling in the legs. This happens when venous pressure is not sufficient to override gravity and venous return is reduced. Because the heart cannot pump more blood than it receives, cardiac output may decrease, sometimes to a dangerous level, and the person may faint. One can prevent this from happening by activating the skeletal muscle pump, either by keeping the legs moving, or by tensing leg muscles periodically. 
Breathing, or respiratory pump: during inspiration, the diaphragm moves down, expanding the thoracic cavity, resulting in a decreased intra-thoracic pressure and a subsequent expansion of the lungs. Part of this change in pressure is transmitted across the walls of the heart, lowering right atrial pressure and thus facilitating venous return. At the same time, the descent of the diaphragm also causes an increase in abdominal pressure. As the inferior vena cava passes through both abdominal and thoracic cavities, an increase in abdominal pressure together with a decrease in thoracic pressure squeeze the blood upward, toward the heart. Increasing the rate and depth of breathing is another way the body raises cardiac output during physical exercise.

Mechanisms of Venous Return, Animation

Blood is a specialized fluid in your body that has four main components, each with a different function: plasma, red blood cells, white blood cells, and platelets. Watch this video to learn more about how these components work. For more information on blood and its disorders, visit ASH's patient resources webpage http://hematology.org/Patients/.

The Components of Blood and Their Importance

A Day in the Life of a Red Blood Cell .flv

Do you remember tripping over as a kid and cutting your knee? And then like magic the bleeding suddenly stops? Have you ever wondered why this happens?

Our body is very clever and produces substances to seal off the open wound. 

In this video we are going to look at how and why blood clots. 

Clotting prevents us from bleeding to death, and also protects us from nasty disease-causing organisms, called pathogens, entering our body. 

When we injure ourselves, we can damage the blood vessels just below our skin. This can cause blood to either leak into our tissue and form a bruise, or, if the skin is broken to openly bleed. 

To prevent these horrible things happening, blood clotting occurs.

So let’s have a look at how this happens.

Starting with platelets. These are tiny cell fragments that float around in our blood.

When a blood vessel is damaged, collagen is exposed. This collagen exposure attracts platelets to the injured area. The platelets then stick together to form a plug. 

They’ve quickly built a little barrier that stops us from losing too much blood. However, this platelet plug isn’t that strong. So it needs to be made stronger.
A protein called fibrin does exactly that. 

In our blood there are soluble fibrinogen proteins. At a wound, these soluble fibrinogen proteins are exposed to outside chemicals that aren’t normally found in blood vessels. Like with the collagen and platelets, this exposure causes the fibrinogen proteins to turn into sticky fibrin fibres. 

The fibrin fibres form a mesh, holding all the platelets together and making a much stronger clot.

More platelets, red blood cells and other components in our blood, all get stuck in the mesh making it even stronger. This clot stops more blood escaping the body. And also prevents nasty pathogens entering our body from the outside.


The clot develops into a scab, which protects the wound as it heals and new layers of skin form underneath. So really, all a scab is is just platelets trapped in the fibrin mesh! 

When the new skin is fully formed, the scab will fall off, revealing the lovely brand new skin underneath.

Remember that I said the exposure to collagen causes the platelets to stick together? And the exposure to outside chemicals causes the fibrinogen to turn into sticky fibrin? 

Both the platelets and the fibrin only become sticky AFTER the exposure. This means that in a normal, healthy blood vessel they won’t randomly cause clots.

So from this video, you should understand the magic of blood clotting. Platelets are first to the scene closely followed by fibrin fibres. Our blood clots so that we don’t lose a lot of blood and don’t let lots of nasty pathogens into our body if we cut ourselves.


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Platelets & Blood Clotting | Biology | FuseSchool

Human Anatomy and Physiology 2 Sheep Heart Anatomy Demonstration

Sheep Heart and Model Anatomy Demo

3D Animation of a Human Heart with the Lungs. 

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You can see the flow of blood through the pulmonary veins. The speed of the heart beat is slowed down for the sake of easy viewing.

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If you enjoyed this animation please consider watching the advertisements at the beginning of this all the way through as a thankyou.

In this animation discover how the heart works, how risk factors contribute to a heart attack and the importance of reducing your risk factors.

Visit https://www.heartfoundation.org.nz/your-heart/post-heart-attack/activity for information developed by the Heart Foundation NZ to support you, your family and your friends in the weeks and months after your heart attack. Find practical advice, where to find support and stories of people who have had an experience similar to yours.

What causes a heart attack?

http://www.smallcoghealth.com
Health information explaining what causes a heart attack. Also see the following parts: "What is a heart attack?", "How is a heart attack diagnosed?" and "How is a heart attack treated?".


What causes a heart attack?
http://www.youtube.com/watch?v=LA2DuxCcO4g


== More Videos in this Series ==

**Cardiovascular System **
Heart Structure - 
http://www.youtube.com/watch?v=62ns10WgI1A
Blood flow through the Heart -
http://www.youtube.com/watch?v=Z_nyv8bqNyE
Electrical activity in the Heart -
http://www.youtube.com/watch?v=zGZUJ9HOyrg
Coronary Arteries -
http://www.youtube.com/watch?v=WjpR3dQ4fIs

**Circulatory System **
The Blood -
http://www.youtube.com/watch?v=4kyQbQOOnYo
Blood Circulation -
http://www.youtube.com/watch?v=xR4RlXiFR18

**Coronary Heart Disease **
What is Angina -
http://www.youtube.com/watch?v=67S_W7S22Qs
What Causes Angina -
In development
How is Angina Diagnosed -
http://www.youtube.com/watch?v=toUZA_71j88
How is Angina Treated - 
http://www.youtube.com/watch?v=edLDxdYOob4
What is a Heart Attack - 
http://www.youtube.com/watch?v=P3sqNkZ6A9w
What causes a Heart Attack - 
http://www.youtube.com/watch?v=-yyfMA7Lu94
How is a Heart Attack Diagnosed - 
http://www.youtube.com/watch?v=YA17W4S5cKQ
How is a Heart Attack Treated - 
http://www.youtube.com/watch?v=iJvdPPjlMI4

**Heart Failure **
What is Heart Failure - 
http://www.youtube.com/watch?v=bDtkZo6yCKw
What Causes Heart Failure - 
http://www.youtube.com/watch?v=WsH_eoyIw9Y
How is Heart Failure Diagnosed - 
http://www.youtube.com/watch?v=I0jqf3JGwFg
How is Heart Failure Treated - 
http://www.youtube.com/watch?v=kXJ734Iq1-8

**Hypertension -- Blood Pressure **
What is Blood Pressure - 
http://www.youtube.com/watch?v=BhNvPb4l744
What Causes Blood Pressure - 
http://www.youtube.com/watch?v=EL_3I-Y--O0
How is Blood Pressure Diagnosed - 
http://www.youtube.com/watch?v=Z2yoQKbKdXg
How is Blood Pressure Treated - 
http://www.youtube.com/watch?v=ZQAkfEf0A1M

**Palpitations **
What are Palpitations -
http://www.youtube.com/watch?v=r1VCbb5OPkM
What Causes Atrial Fibrillation - 
http://www.youtube.com/watch?v=IhFSrLdPMuw
How is Atrial Fibrillation Diagnosed & Treated - 
http://www.youtube.com/watch?v=Lso2oBj1wGA
Ventricular Arrhythmias - 
http://www.youtube.com/watch?v=yTF1obIFqOI
What is Syncope - 
http://www.youtube.com/watch?v=n23BJTCibhs
What Causes Syncope - 
http://www.youtube.com/watch?v=vhUM8oNIgE8
How are the Causes of Syncope Diagnosed - 
http://www.youtube.com/watch?v=lGAR2x15Jcc
How is Syncope Treated - 
http://www.youtube.com/watch?v=ylZGp8vOSmA

**Valvular Heart Disease **
What is Valvular Heart Disease - 
http://www.youtube.com/watch?v=1hrhPww5jKY
What Causes Valvular Heart Disease - 
http://www.youtube.com/watch?v=Ponx7YKFfk8
How is Valvular Heart Disease Diagnosed - 
http://www.youtube.com/watch?v=fOwCadoTrw0
How is Valvular Heart Disease Treated - 
http://www.youtube.com/watch?v=v_W1sctcj2E

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Every two seconds, someone in the world has a stroke. One out of every six people will have a stroke at some point in their lives. Strokes deprive brain cells of oxygen and are one of the most common causes of death, and a leading cause of preventable disability. But what causes strokes in the first place? And what can doctors do to treat them? Vaibhav Goswami takes us into the body to find out.

Lesson by Vaibhav Goswami, animation by Artrake Studio.

Thank you so much to our patrons for your support! Without you this video would not be possible! John Saveland, Nicolle Fieldsend-Roxborough, Mridul Goswami, Venkat Venkatakrishnan, Sandy Nasser, CG Nobles, QIUJING L BU, Yoga Trapeze Wanderlust, Jaron Blackburn, Alejandro Cachoua, Thomas Mungavan, Elena Crescia, Edla Paniguel, Sarah Lundegaard, Charlsey, Anna-Pitschna Kunz, Tim Armstrong, Alessandro, Erika Blanquez, Ricki Daniel Marbun, zjweele13 , Judith Benavides, Znosheni Kedy, Caitlin de Falco, Scheherazade Kelii, Errys, James Bruening, Michael Braun-Boghos, Ricardo Diaz, Kack-Kyun Kim, Alexandrina Danifeld, Danny Romard, Yujing Jiang, Stina Boberg, Mariana Ortega, Anthony Wiggins, Hoai Nam Tran, Joe Sims, David Petrovič, Kat, Chris Adriaensen, Lowell Fleming, Lorenzo Margiotta, Amir Ghandeharioon, Anuj Tomar, Sunny Patel, Rachel Birenbaum, Vijayalakshmi , Devesh Kumar, Uday Kishore, Aidan Forero, Leen Mshasha, Allan Hayes, Thomas Bahrman, Alexander Baltadzhiev, Connor Yuzwenko-Martin, Vaibhav Mirjolkar, Tony, Michelle, Katie and Josh Pedretti, Erik Biemans, and Gaurav Mathur.

What happens during a stroke? - Vaibhav Goswami

Circulatory System - Student Lesson Outline 

The Circulatory System is a lesson by Teach Science with Fergy, containing engaging videos, presentations and activities to help develop students' science knowledge.

What Causes Varicose Veins?

Science Resource Description