In an open circulatory system, how is blood moved?

In an open circulatory system, how is blood moved?

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In the mollusks section, the powerpoint mentioned that gastropods and bivalves have an open circulatory system. According to the note, this means that the blood does not travel in vessels. How, then, does blood move? Does that mean that these organisms are simple enough to be able to survive by just pumping blood straight out into the body?

How does this type of circulatory system work?



In a closed circulatory system, all of the blood stays within blood vessels or the heart itself.

Organisms that have open circulatory systems, such as arthropods, have hemolymph (a fluid that is essentially a mixture of blood and interstitial fluid). The hemolymph actually does travel in vessels for a very short amount of time, as it is leaving the heart. After this, it goes to the body cavities of the animal and directly bathes the tissues in the fluid in order to deliver oxygen, nutrients, etc.

Hemolymph moves throughout the body when the animal moves. Also, when the heart relaxes, hemolymph is drawn back toward the heart through ostia, or open-ended pores.

So to answer your question, yes, these animals can survive just by pumping hemolymph straight into the body. This is only effective because their body cavities are very small. In humans, an open circulatory system would never work because it would require an enormous amount of work to pump and circulate blood throughout our entire body cavity.

Open Circulatory System

Open circulatory systems are systems where blood, rather than being sealed tight in arteries and veins, suffuses the body and may be directly open to the environment at places such as the digestive tract.

Open circulatory systems use hemolymph instead of blood. This “hemolymph” performs the functions of blood, lymph, and intestinal fluid – which are three different, highly specialized fluids in animals with closed circulatory systems.

Instead of a complex and closed system of veins and arteries, organisms with open circulatory systems have a “hemocoel.” This is a central body cavity found inside most invertebrate animals where both digestive and circulatory functions are performed. This hemocoel may have “arteries” through which the blood can reach tissues – but these arteries are not closed and do not circulate blood as quickly as closed, muscle-assisted arteries.

Within the hemocoel, hemolymph directly absorbs nutrients from food and oxygen from the lungs or breathing pores. It also contains immune cells – but hemolymph does not have red blood cells like our own. Instead of using hemoglobin to carry oxygen, organisms with open circulatory systems use blue or yellow-green pigments to carry oxygen throughout the body.

Many animals that use open circulatory systems do have a heart – but the heart only pumps hemolymph to different cavities in the hemocoel. From these branches of the central body cavity, blood and the oxygen and nutrients it contains must penetrate the tissues and then return to the heart without the help of highly specialized pathways or muscle-assisted arteries like vertebrates possess.

In all animals, circulatory systems perform several vital functions. The circulatory system can be thought of as a river connecting the specialized cells of the body, which allows them to perform the trade and communication upon which their survival depends.

There are a few vital functions that all circulatory systems must serve. These include:

  • Transporting the oxygen that is necessary for cellular respiration
  • Transporting nutrients from food, which are necessary for cellular respiration and other functions
  • Transporting waste products of cellular respiration and other functions, which could otherwise build up to toxic levels within the body
  • Transporting any necessary messages between cells, such as hormones signaling hunger, thirst, oxygen deprivation, or other bodily needs.
  • Transporting immune cells which can fight infection to any area of the body where they might be needed.

Both blood and hemolymph accomplish these functions.

In closed circulatory systems, highly complex and specialized blood vessels and blood cells make these functions highly efficient. Within your own body, a system of closed arteries is lined with muscles to push blood through your entire body in only sixty seconds. Your body also has specialized blood cells that are very good at carrying oxygen from your lungs to other tissues.

Organisms with hemolymph systems do not have these advantages they have a central body cavity, called a hemocoel, instead of a closed system of blood vessels. Instead of blood cells, less efficient oxygen-carrying pigments float freely in the hemocoel.

To keep their cells alive, organisms with open circulatory systems must be small enough that hemolymph can reach all of their cells and deliver the materials necessary for life without the aid of a highly developed circulatory system.

This is why arthropods and mollusks – the two major living groups of organisms with open circulatory systems – are typically small. Giant ants or spiders would not be able to supply their tissues with sufficient oxygen to survive, unless they evolved a closed circulatory system.

1. Which of the following is NOT a difference between open and closed circulatory systems?
A. Closed circulatory systems have specialized arteries and veins open circulatory systems do not.
B. In open circulatory systems, hemolymph performs the functions that are performed by blood, lymph, and intestinal fluid in closed circulatory systems.
C. Open circulatory systems usually do not have a heart.
D. None of the above.

2. Which of the following is NOT an organism you would expect to have an open circulatory system?
A. Hermit crab
B. Ant
C. Clam
D. Squid

3. Which of the following characteristics are shared by open and closed circulatory systems?
A. Red blood cells
B. Immune cells
C. Arteries, veins, and capillaries
D. None of the above

What is an Open Circulatory System? (with pictures)

An open circulatory system is a type of circulatory system in which nutrients and waste are moved through the body with the assistance of a fluid which flows freely through the body cavity, rather than being contained in veins. Many invertebrates like insects and shellfish have an open circulatory system, with the exact composition of the circulating fluid varying, depending on the animal species involved. In contrast, vertebrates have a closed circulatory system which circulates blood through a series of vessels in the body, with the interstitial fluid known as lymph moving slowly between the cells and through a series of lymph nodes.

In the case of an animal with an open circulatory system, all of the organs and internal structures are constantly bathed in a mixture of the components of blood and lymph. This fluid brings nutrition and often oxygen to these structures, while carrying away waste for processing. Because the system is not closed, it is not possible to create blood pressure instead, the animal circulates this fluid with muscle contractions. In some animals, the fluid is not oxygenated instead, tissues receive oxygen directly through the tracheal system.

The fluid in an open circulatory system is sometimes referred to as hemolymph, referencing the fact that it is a cross between blood and lymph. It spends a brief amount of time in the heart, but instead of being pumped out of the heart and into a network of arteries and veins, it is dumped directly into the body cavity of the animal. If you have ever handled fresh shellfish, you have seen hemolymph it is the pale pinkish to green fluid which squirts out when you cut the shellfish open.

One advantage to an open circulatory system is that it renders the animal much less vulnerable to pressure. This can be an advantage for mollusks which live at great depths, because it prevents compression of their bodies. Because many insects use their tracheal systems to transport oxygen, they tend to have open circulatory systems because they place less demands on their bodies efficiency is not as urgent when oxygen and carbon dioxide are handled through a separate system.

The open circulatory system also gives animals greater control over their body temperature, which can be a distinct advantage at times. For example, it can help to quickly dissipate heat, allowing insects to survive in extremely hot environments. However, animals with a closed circulatory system have greater control over oxygen delivery to specific tissues, and they are also able to filter their blood and lymph more accurately because these systems are separated.

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a InfoBloom researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a InfoBloom researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

An "Open" Circulatory System: The Grasshopper

The circulatory system of insects differs from that of vertebrates and many other invertebrates in being "open". In insects, "blood" is confined to vessels during only a portion of its circuit through the body. The remainder of its journey takes place within the body cavity (called the hemocoel). For this reason, insect "blood" is called hemolymph.

The volume of hemolymph needed for such a system is kept to a minimum by a reduction in the size of the body cavity. The hemocoel is divided into chambers called sinuses.

In the grasshopper, the closed portion of the system consists of tubular hearts and an aorta running along the dorsal side of the insect. The hearts pump hemolymph into the sinuses of the hemocoel where exchanges of materials take place.

Coordinated movements of the body muscles gradually bring the hemolymph back to the dorsal sinus surrounding the hearts. Between contractions, tiny valves in the wall of the hearts open and allow hemolymph to enter.

This "open" system might appear to be inefficient compared to closed circulatory systems like ours [Link], but the two have very different demands being placed on them.

In vertebrates, the circulatory system is responsible for transporting oxygen to all the tissues and removing carbon dioxide from them. It is this requirement that establishes the level of performance demanded of the system. The efficiency of the vertebrate system is far greater than needed for transporting nutrients, hormones, etc.

In the grasshopper, exchange of oxygen and carbon dioxide occurs in the tracheal system. Hemolymph plays no part in the process. There is not even an oxygen-carrying pigment in insect hemolymph.

Problem: In an open circulatory system, blood is ________.a. always inside of vessels and is under higher pressure than in closed circulatory systemsb. not always confined to blood vessels and is under higher pressure than in closed circulatory systemsc. always inside of vessels and is under lower pressure than in closed circulatory systemsd. not always confined to blood vessels and is under lower pressure than in closed circulatory systems

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Structure of the human circulatory system

The human circulatory system consists of:

Blood vessels:

  • Arteries: blood vessels that carry blood away from the heart in pulses. It has a thick wall and small lumen.

The thick wall of arteries contains a tough outer layer of collagen that gives strength to the artery that supports the pressure the blood is under from the heart.
It also contains a layer of smooth (involuntary) muscle that contracts pushing blood along. The internal layer of the artery is composed of a layer of cells called the endothelium.

  • Veins: blood vessels that carry blood towards the heart in an even flow. They have thin walls, a large lumen and valves.

Blood pressure in veins is much lower than arteries, hence the thinner wall. They also have smooth muscle to push blood along in one direction and have valves to prevent back flow of blood.

  • Capillaries: blood vessels with walls one cell thick that carries blood from arterioles to venules through tissues, releasing nutrients and taking away wastes.

Systemic and pulmonary circuits

The human circulatory system consists of two blood circuits: the systemic circuit and the pulmonary circuit. This is why the human circulatory system is described as a double circulatory system.
The systemic circuit carries blood to all the major organs of the body, except the lungs.
The lungs have their own blood circuit, called the pulmonary circuit.
The diagram below shows all the arteries and veins emanating from, and returning to, the heart and internal organs.

Portal system

  • A portal system is a network of blood capillaries that connect two organs or tissues, e.g. hepatic portal system connects the small intestines to the liver via the hepatic portal vein.

Circulatory System Architecture

In (a) closed circulatory systems, the heart pumps blood through vessels that are separate from the interstitial fluid of the body. Most vertebrates and some invertebrates, like this annelid earthworm, have a closed circulatory system. In (b) open circulatory systems, a fluid called hemolymph is pumped through a blood vessel that empties into the body cavity. Hemolymph returns to the blood vessel through openings called ostia. Arthropods like this bee and most mollusks have open circulatory systems.

Circulatory System of Human Beings- Explained

Blood, as you know, is a liquid connective tissue that circulates in a closed system of blood vessels.

An adult man has about five to six liters of blood, while a woman, on an average, has about one liter less.

Our blood consists of (i) solid elements—which include red blood corpuscles (RBCs), white blood corpuscles (WBCs), and blood platelets, and (ii) liquid element—the plasma.

The corpuscles comprise about 45% and the plasma about 55% of the volume of blood.


Plasma is a straw-coloured liquid in which the RBCs, WBCs and platelets float. It contains mainly water, in which are dissolved various substances such as plasma proteins, food substances (amino acids, glucose, and fats), nitrogenous compounds and ions of sodium, potassium, calcium, magnesium and phosphorus.

Blood corpuscles:

Blood is red in colour due to the presence of RBCs. The RBCs contain the red-coloured respiratory pigment haemoglobin. This iron-protein compound transports oxygen from the lungs to the tissues. RBCs also transport carbon dioxide. WBCs protect the body from infection. Platelets help in the clotting of blood.

Visit a diagnostic centre. Give your blood sample. Get it checked for the level of haemoglobin.

The normal range of haemoglobin in humans is 120-180 g/L, or 12-18 g/L, of blood. Check your blood report to see if your haemoglobin level fails in this range. But haemoglobin levels also depend on age, sex and ethnic values of a place. For example, females have a lower normal value of haemoglobin level than males.

A below-normal level of haemoglobin may indicate anemia due to a number of possible causes. Low haemoglobin level could be from actual loss of blood from haemorrhage, vitamin deficiencies, lack of iron in the diet or a disease. This indicates that the person’s cells are not getting enough oxygen for energy production. Such anemic persons always feel tired and weak.

You can even obtain the normal range of hemoglobin level in animals such as cows, buffaloes, goats, etc., by visiting a veterinary clinic. This value is lower in these animals than in humans. The normal hemoglobin level in cows lies in the range of (5.9 ± 1.54) g/L of blood.

Blood dotting by platelets:

You must have noticed that after a cut the skin bleeds for a while, and then the blood thickens to form a clot. This process takes place as a result of a series of reactions in the blood. These reactions are started by the release of an enzyme by the circulating platelets.

The clot, which forms at the point of the wound, is a microscopic network of insoluble fibrous protein. It minimizes the loss of blood. If blood is lost, it leads to a loss of pressure by the pumping heart.

Functions of blood:

1. Transport of respiratory gases:

Blood carries oxygen from the lungs to the tissues. It also carries carbon dioxide from the tissues to the lungs.

2. Transport of nutrients:

Absorbed in the small intestine enter the blood capillaries. Blood carries these nutrients and distributes them to all parts of the body.

3. Transport of waste products:

Waste products of the body, such as urea, uric acid, etc., are carried by blood to the excretory organs.

4 . Regulation of water content of cells:

Blood regulates the water content of the cells when the water content in cells increases, blood takes up the excess amount of cellular water. Blood provides water to cells when they need it.

5. Regulation of body temperature:

Increased body temperature resulting from the excess respiration of a particular tissue is equalized by circulation of blood.

6. Defence against infection:

Blood protects the body against infection.

7. Prevention of bleeding:

Clotting blood prevents excess bleeding.

Blood Vessels:

Three types of blood vessels, namely, arteries, veins and capillaries, are involved in blood circulation. They are all connected to form one continuous closed system.


The arteries are wide, elastic and thick-walled vessels as they carry blood away from the heart to the limbs and organs of the body. They have thick, elastic walls to withstand the high pressure of the blood emerging from the heart.


Veins bring back blood from the tissues and organs to the heart. The blood in veins flows under less pressure than that in arteries. Therefore, veins do not have thick walls. But veins can accommodate more blood. Veins have valves that allow blood to flow in one direction only.


Arteries branch out into smaller and thinner blood vessels called arterioles. These divide into still smaller vessels to provide blood to all the cells. The thinnest blood vessels are called capillaries. Their walls have just one layer of squalors cells.

These walls are permeable, so that water and dissolved substances pass in and out, exchanging oxygen, carbon dioxide, dissolved nutrients and waste products with the tissues around the capillaries. The capillaries form a dense network, reaching out to each and every part of the body. The flow of blood is very slow in capillaries. They join to form venules and veins, which return blood from organs and tissues to the heart.

The human heart:


The heart is a muscular, conical and dark red organ that plays the role of a pump in the circulatory system. Its pumping action maintains the circulation of blood.

In man, the heart weighs about 0.43 per cent of the body weight. It is located in the middle of the thoracic cavity, but its apex is tilted towards the left side. The heart is enclosed in the pericardium, a tough, inflexible membrane. Between the heart and the pericardium is a fluid which reduces the friction produced during heartbeat.

The heart is made up of cardiac muscles. These muscles contract with considerable force, squeezing the blood out into the arteries. The heart beats nonstop throughout one’s life. It is due to the rhythmic contraction and relaxation of the heart muscles. There are four chambers in the heart—two atria, with thin walls, and two ventricles, with thick walls.

Working of the heart:

Blood from different parts of the body comes to the right atrium when it expands. This impure blood is brought from the upper part of the body through the superior vena cava and from the lower part of the body through the inferior vena cava.

As the right atrium contracts, the blood goes to the right ventricle, which dilates. The atrioventricular aperture is closed by a valve after the blood transfer. Valves prevent the backflow of blood when the atria or ventricles contract.

When the right ventricle contracts, the blood is forced out to the lungs for oxygenation through the pulmonary artery, guarded by another valve. In the lungs, there is an exchange of oxygen and carbon dioxide. After the blood has received oxygen from the lungs and given off carbon dioxide, the oxygenated blood returns to the left atrium.

Pulmonary veins bring this oxygenated blood from the lungs to the left atrium, as it relaxes. When the left atrium contracts, blood is transferred to the left ventricle, which expands. The aperture between the left atrium and left ventricle is guarded by a valve. The wall of the left ventricle is three or four times thicker than the wall of the right ventricle, as it pumps blood to the body.

When the left ventricle contracts, the oxygen-rich blood is pumped into the aorta for circulation to different parts of the body. The opening of the aorta is also guarded by a valve. Deoxygenated blood is collected from different parts of the body by small veins. These open into larger veins, which bring the blood back to the right atrium.

Cardiac cycle:

One sequence of the filling of the heart with blood and its pumping is called the cardiac cycle. The phase of contraction of the ventricle is called systole and its relaxation phase is called diastole.

Blood pressure:

As blood flows, it exerts a force on the walls of the blood vessels. This is much greater in the arteries than in the veins. The pressure of flow of blood in the aorta and its main branches is defined as blood pressure. The heart has to develop a high pressure so that blood can be pumped through the arteries, capillaries and veins.

During the ventricular contraction, or systolic phase, it is equal to that exerted by a column of 120 mm of mercury. During the ventricular relaxation, or diastolic phase, it is about 80 mmHg.

Thus, the normal blood pressure is said to be �/80’. However, the blood pressure varies from person to person and is affected by age, sex, heredity, physical and emotional states, and other factors.

An instrument called sphygmomanometer is used to measure blood pressure. Abnormally high blood pressure is called hypertension. It may be associated with a disease or may occur due to anxiety.

During hypertension, the arterioles get constricted and increase resistance to blood flow. High blood pressure can cause the rupture of blood vessels, internal bleeding or stroke. If a blood vessel is ruptured in the brain, that part does not get blood, oxygen and nutrients, and loses its function.

The Lymphatic System:

Lymph is another type of fluid that takes part in transportation:

Blood containing oxygen and food flows under tremendous pressure in the arteries, which divide into arterioles and eventually into capillaries.

When the blood from an arteriole enters a capillary, it is under so much pressure and the capillary walls are so thin that a clear liquid is forced out of the capillary walls into the spaces between the surrounding cells.

This liquid is called tissue fluid. Tissue fluid carries with it oxygen, food and other useful substances to the cells. It also takes away carbon dioxide and waste products from the cells.

If tissue fluid were to accumulate in the tissues and organs, it would cause swelling. So, it is returned to the bloodstream through another system of vessels, called the lymphatic system. The lymphatic system consists of lymph, lymph vessels and lymph nodes.

Most of the tissue fluid drains into lymph vessels and flows as lymph. Lymph is similar to blood except that it does not have RBCs and blood platelets, and has a lesser amount of proteins. Therefore, lymph is colourless or slightly yellowish and is similar to blood plasma.

The lymphatic system maintains the balance between tissue fluid and blood. Lymph carries digested fat from the intestine and drains excess fluid from the intercellular spaces back into the blood.

Before lymph enters the blood, it passes through a number of lymph nodes. These are small globular masses of lymphatic tissue. Lymph nodes produce WBCs that prevent infection.

Here’s How the Circulatory System of a Pig Works

The circulatory system of a pig includes a heart, blood, and the blood vessels. The blood is transported within the body through a network of blood vessels. The pig circulatory system is quite similar to humans. Know more about the circulatory system of pigs by going through this article.

The circulatory system of a pig includes a heart, blood, and the blood vessels. The blood is transported within the body through a network of blood vessels. The pig circulatory system is quite similar to humans. Know more about the circulatory system of pigs by going through this article.

The pig has a circulatory system that is quite similar to the human circulatory system. In pigs, the circulatory system is composed of the heart, blood, and the blood vessels. As the name suggests, this system is responsible for circulating blood and nutrients throughout the body.


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The heart of a pig is four-chambered. The top two chambers are known as atria (singular atrium), while the bottom two chambers are called ventricles. The inner surface of the heart is lined by a type of smooth tissue, known as endocardium.

The heart acts like a pumping organ. The number of times the heart beats in a minute is called heart rate or pulse rate. In an adult pig, the heart rate is usually 70 beats, while in young piglets, it can be about 200 beats per minute. In pigs, the heart rate can be felt at the base of the ear or under the tail.


Blood is the body fluid composed of plasma and blood cells. Blood cells are of two types – white and red blood cells. The white blood cells are an important part of the body’s defense or immune system, as they fight disease-causing agents like bacteria and viruses. The red blood cells or erythrocytes contain a protein known as hemoglobin, that transports oxygen to various parts of the body. Blood also contains platelets, which are responsible for blood clotting.

Blood Vessels

The blood vessels, known as arteries and veins circulate blood throughout the body. Arteries are responsible for carrying blood from the heart to the entire body, while veins return blood to the heart. The large arteries branch off into smaller arteries and arterioles, which further branch off into some tiny microscopic capillaries. The capillaries can interchange fluids through their walls, and thereby help the cells receive water, oxygen, and nutrients from blood, and get rid of waste products like carbon dioxide. The fine capillaries then combine and widen to become venules, and then veins, which carry blood to the heart.

Circulatory Mechanism

The entire circulatory mechanism in pigs can be classified into two parts – pulmonary and systemic circulation. Pulmonary circulation refers to the circulation of blood between the heart and the lungs, while systemic circulation is the circulation of blood between the heart and the rest of the body, excepting the lungs.

The deoxygenated or oxygen-deprived blood is collected from the body by the veins that terminate into two main large main veins – anterior and posterior vena cava. The deoxygenated blood first reaches the right atrium of the heart, from where it is transported to the right ventricle. It is then transported to the lungs through the pulmonary arteries for oxygenation.

The oxygen-rich blood from the lungs is carried to the heart by the pulmonary veins. The blood enters the left atrium first, from where it is pumped into the left ventricle. Finally, the oxygenated blood is pumped out of the heart into the aorta or the main artery. It is then carried by the numerous arteries to the different parts of the body.

Pig Fetal Circulation

The circulation of blood in pig fetus is somewhat different. The pig fetus receives oxygen-rich blood from the placenta through the umbilical vein. The umbilical vein reaches the liver, from where the blood enters the posterior vena cava through the ‘passage ductus venosus’. Posterior vena cava carries blood to the heart.

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In the fetal stage, the pulmonary circuit (which pumps blood from the heart to the lungs) is non-functional. So, almost half of the blood that enters the right atrium directly reaches the left atrium through a small opening called ‘foramen ovale’. Then it enters the left ventricle, from where it flows into the aorta to be circulated throughout the body. The remaining amount of blood in the right atrium enters the right ventricle, and then the pulmonary trunk. From here, the blood goes into the aorta through the shunt ‘ductus arteriosus’ and is then circulated throughout the body.

For proper circulation of blood within the body, the health of the heart and the blood vessels is very crucial. Any damage to these organs can impair circulation, and hamper the vital functions of the body. The lungs also play an important role in circulation, as they oxygenate blood. So, any disease of the lungs may result in the shortage of oxygen in the cells and tissues, which can disrupt their normal functioning.

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In an open circulatory system, how is blood moved? - Biology

Functions of Circulatory System:

Circulate blood around the body

Transport gasses, Transport nutrients to cells, Transport waste materials from cells, Transport hormones

Contains white blood cells that destroy foreign material

It helps maintain body temperature by transporting heat.

Structure and function of Blood Vessels:

Arteries: Arteries carry blood away from heart. All arteries contain oxygenated blood except Pulmonary Arteries. Arteries have a thick, elastic layer to allow stretching and absorb pressure.

Veins: Veins carry blood to the heart. All veins contain deoxygenated blood except Pulmonary Veins. The diameter of veins is greater than that of arteries. The blood pressure in the veins is low so valves in veins help prevent backflow. Veins act as blood reservoirs because they contain 50% to 60% of the blood volume.

Pathway of blood through the heart:

First deoxygenated blood enters the right atrium through the superior and inferior vena cava then it is pumped through the tricuspid valve into the right ventricle, then it is pumped through the pulmonary valve through the pulmonary arteries to the lungs. The left atrium receives oxygenated blood from the lungs and pumps it through the mitral (bicuspid) valve to the left ventricle where it is pumped through the aortic valve to the aorta.

Functions of the valves:

Tricuspid Vavle: This valve permits blood to move from right atrium into right ventricle and prevent the backflow of blood from right ventricle into right atrium.

Pulmonary Valve: Prevents blood from going back into right ventricle.

Mitral (bicuspid) Valve: Prevents blood from going back into left atrium.

Aortic valve: Prevents blood from moving from aorta into left ventricle.

Blood consists of White Blood Cells (leukocytes), Plasma, Red Blood Cells (erythrocytes), and Platelets.

White Blood Cells: Help fight infection there are 5 different WBCs: Neutrophil, Basophil, Eosinophil, Monocyte, and Lymphocyte.

Plasma: Makes up about 55% of the blood sample. Its straw-colored liqiud. Plasma is made up of water, amino acids, proteins, carbohydrates, lipids, vitamins, hormones, electrolytes, and cellular wastes.

Platelets: Cytoplasmic fragment formed in the bone marrow that helps blood clot.

Red blood Cells: Carry oxygen and carbondioxide help exchange gases between tissue or cells in out body. Makes up about 45% of the blood sample.

Erythrocytes Structure and Function (in-depth):

Erythrocytes ( Red Blood Cells) are tiny, biconcave discs, which means they are thin near the centers and thicker around their rims. This special shape is an adaptation for the red blood cell's function of transporting gasses: it increases the surface area through which gases can diffuse.

Open and Closed circulatory systems:

Examples of Open System: Arthropods and most mollusks (except cephalopods: nautilus, squid, octopus)

Open Circulatory System

Closed Circulatory System

-Blood is pumped from the heart through blood vessels but then it leaves the blood vessels and enters body cavities.

-Blood is not free in a cavity it is contained within blood vessels. Valves prevent the backflow of blood within the blood vessels.

-Blood flows slowly in an open circulatory system because there is no blood pressure after the blood leaves the blood vessels.

-Blood remains within blood vessels, pressure is high, and blood is therefore pumped faster.

Different Circulations:

Fish Circulation: Fish have a two-chambered heart with one atrium and one ventricle. The gills contain many capillaries for gas exchange, so the blood pressure is low after going through the gills. Low-pressure blood from the gills then goes directly to the body, which also has a large number of capillaries. The activity level of fish is limited due to the low rate of blood flow to the body.

Amphibian Circulation: Amphibians have a 3-chambered heart with two atria and one ventricle. Blood from the lungs goes to the left atyrium. Blood from the bod goes to the right atrium. Both atria empty into the ventricle where some mixing occurs. The advantage of this system is that there is high pressure in vessels that lead to both the lungs and body.

Reptile Circulation: In most reptiles, the ventricle is partially divided. This reduces mixing of oxygenated and unoxygenated blood in the ventricle.

Two Disorders of the Circulatory System:

a.) Anemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to body tissues. There are more than 1000 types of anemia. So if you are anemic you aren't getting enough oxygen throughout your body.

b.) Some main symptoms of Anemia:

  • Chest pain
  • Dizziness or light-headedness (especially when standing up or with activity)
  • Fatigue or lack of energy
  • Headaches
  • Problems concentrating
  • Shortness of breath (especially during exercise)

Some types of anemia may have other symptoms, such as:

Pale Skin, Rapid Heart Beat, Heart Murmur

c.) In the US the percent of anemic patients is low but in other countries its really high around 40 to 65% of people in countries like Africa get anemic.

d.) Treatment should be directed at the cause of the anemia, and may include:

  • Blood transfusions
  • Corticosteroids or other medicines that suppress the immune system
  • Erythropoietin, a medicine that helps your bone marrow make more blood cells
  • Supplements of iron, vitamin B12, folic acid, or other vitamins and minerals.

a.) Leukemia is cancer of the body's blood-forming tissues, including the bone marrow and the lymphatic system. Many types of leukemia exist. Some forms of leukemia are most common in children. Other forms of leukemia occur mostly in adults. Leukemia usually starts in the white blood cells. Your white blood cells are potent infection fighters. They normally grow and divide in an orderly way, as your body needs them. But in people with leukemia, the bone marrow produces a large number of abnormal white blood cells, which don't function properly.

b.) Leukemia symptoms vary, depending on the type of leukemia. Common leukemia signs and symptoms include:

  • Fever or chills
  • Persistent fatigue, weakness
  • Frequent infections
  • Losing weight without trying
  • Swollen lymph nodes, enlarged liver or spleen
  • Easy bleeding or bruising
  • Tiny red spots in your skin (petechiae)
  • Excessive sweating, especially at night
  • Bone pain or tenderness

c.) It is estimated that 44,600 men and women (25,320 men and 19,280 women) will be diagnosed with and 21,780 men and women will die of leukemia in 2011

d.) Common treatments used to fight leukemia include: Chemotherapy, Biological therapy, Radiation therapy, Targeted therapy, Stem cell transplant