Circulatory System Definition

The heart, blood arteries, and blood are all parts of the body's circulatory system, which allows a human or other vertebrate to have blood flow throughout the body. It contains the cardiovascular system, also known as the vascular system, which is made up of the heart and blood vessels (the words "blood vessels" and "heart" are derived from the Latin word "vascula," respectively). The circulatory system is divided into two sections: pulmonary circulation and systemic circulation.

The vast network of blood vessels that make up the heart's large vessels includes huge elastic arteries, large veins, and other arteries, smaller arterioles, capillaries that connect to venules (small veins), and other veins. In vertebrates, the circulatory system is closed, which implies that the blood never exits the system of blood vessels. Arthropods, for example, have an open circulatory system. Diploblasts without a circulatory system include sponges and comb jellies.

Plasma, red blood cells, white blood cells, and platelets make up the fluid called blood, which is transported throughout the body to provide oxygen and nutrition to the tissues and remove waste. Proteins and minerals are among the nutrients carried in the bloodstream, along with gases like oxygen and carbon dioxide, hormones, and haemoglobin. These nutrients not only sustain the body but also support the immune system's ability to fight off illness and maintain homeostasis by regulating temperature and pH.

The lymphatic system is the counterpart of the circulatory system in vertebrates. This system removes extra plasma that has been filtered from the capillaries as interstitial fluid between cells from the bodily tissues and returns it as lymph to the blood circulation. Lymph takes far longer to go through the body than blood does. Without the lymphatic system, a subsystem that is crucial to the blood circulatory system's operation, the blood would become dehydrated. The immune system and lymphatic system collaborate. The lymphatic system is an open system, in contrast to the closed circulatory system. It is referred to be a secondary circulatory system in certain publications.

Numerous cardiovascular illnesses may have an impact on the circulatory system. Cardiothoracic surgeons specialise in operating on the heart and its surrounding parts, whereas cardiologists are medical specialists in the heart. Vascular surgery focuses on problems with lymphatic and blood vessels.

Parts of the Circulatory System

A circuit loop known as the pulmonary circulation transports deoxygenated blood from the right heart to the lungs, where it is given oxygen and then returns to the left side of the heart. The left heart pumps oxygenated blood to the rest of the body via the systemic circulation, which is a circuit loop that sends deoxygenated blood back to the right heart through the venae cavae. A macrocirculation and a microcirculation are two other ways to describe the systemic circulation. An adult's blood volume ranges from five to six quarts, or around 4.7 to 5.7 litres, making up about 7% of their entire body weight. Red blood cells, white blood cells, platelets, and plasma comprise blood. The circulatory system and the digestive system collaborate to provide the body with the nutrition it needs to keep the heart beating.

Additional circulatory pathways are connected, such as the coronary circulation, which goes to the heart, the cerebral circulation, which goes to the brain; the renal circulation, which goes to the kidneys; and the bronchial circulation, which goes to the bronchi in the lungs.

The blood is confined inside the vascular network because the human circulatory system is closed. Microcirculation allows nutrients to reach organs through tiny blood arteries. An important component of the circulatory system, the lymphatic system is made up of a network of lymphatic veins, lymph nodes, organs, tissues, and circulating lymph. This system's subsystem is open. One of its main functions is carrying lymph, draining and transferring interstitial fluid into the lymphatic channels back to the heart for return to the circulatory system. Together with the immune system, the body's principal role is to offer pathogen defence.

Heart

Every cell in the body receives nutrition and oxygen from the blood, which heart pumps to all other regions of the body while also eliminating waste. In the systemic circulation, the left heart distributes oxygen-rich blood that has been returned from the lungs to the rest of the body. During pulmonary circulation, the right heart pushes blood that lacks oxygen into the lungs. For both a systemic and pulmonary circulation, the human heart has four chambers total-a left atrium, a left ventricle, a right atrium, and a right ventricle. There is one atrium and one ventricle for each circulation. The right side of the heart's upper chamber is known as the right atrium. Deoxygenated blood that has been returned to the right atrium is transported into the right ventricle, where it is pushed via the pulmonary artery to the lungs, where it is re-oxygenated, and carbon dioxide is removed. Blood is drawn into the left atrium from the pulmonary vein and the lungs, where it is freshly oxygenated before being pushed to the body's various organs through the aorta.

There are two pathways that blood follows for circulation in our heart:

1. Pulmonary Circulation
2. Systematic Circulation

1. Pulmonary Circulation

The pulmonary circulation is the part of the circulatory system where oxygen-depleted blood is pushed from the heart to the lungs through the pulmonary artery and then returns to the heart via the pulmonary vein after being oxygenated.

The right atrium of the heart receives oxygen-depleted blood from the superior and inferior vena cava, which then passes through the tricuspid valve (right atrioventricular valve) and into the right ventricle, where it is then pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs. The lungs engage in gaseous exchange, which involves the emission of CO₂ from the blood and the absorption of oxygen. The left atrium receives the blood that is now oxygenated via the pulmonary vein.

The larger lung airways' tissue is supplied with blood via the bronchial circulation, a distinct circuit from the systemic circulation.

2. Systematic Circulation

Through the aorta, oxygenated blood from the left heart is sent through a circuit loop known as the systemic circulation to the rest of the body. Deoxygenated blood is sent back to the right heart's right atrium, which is pushed into the pulmonary circulation for oxygenation through two major veins, called the inferior vena cava and superior vena cava, in the systemic circulation. A macrocirculation and a microcirculation are the two components of the systemic circulation.

Blood

In the circulatory systems of humans and other vertebrates, blood is a bodily fluid that carries metabolic waste products away from the cells while also delivering essential elements like nutrition and oxygen to the cells. Blood is made up of blood cells suspended in blood plasma. Plasma, which makes up 55% of blood fluid, is largely water (92% by volume), includes proteins, carbohydrates, mineral ions, hormones, carbon dioxide (plasma is the primary medium for excretory product movement), and blood cells.

Plasma's primary protein, albumin, controls the blood's colloidal osmotic pressure. In mammals, platelets (also known as thrombocytes) and red blood cells (commonly known as RBCs or erythrocytes) make up the majority of the blood. White blood cells (also known as WBCs or leukocytes) are also present. Red blood cells are the most numerous cells in vertebrate blood. These have haemoglobin, a protein containing iron that speeds up oxygen transport by reversibly binding to this respiratory gas and boosting its solubility in blood. As a bicarbonate ion, carbon dioxide is mostly carried extracellularly by plasma. Vertebrate blood becomes brilliant red when the haemoglobin is present (oxygenated) and dark red when it is not(deoxygenated).

Hemocyanin, rather than haemoglobin, is sometimes used to deliver oxygen by certain creatures, such as crabs and molluscs. Haemolymph, a fluid that is not enclosed in a closed circulatory system, is used instead of blood by several insects and molluscs. Most insects' "blood" lacks oxygen-carrying molecules like haemoglobin because their bodies are so tiny that their tracheal systems are more than enough to deliver oxygen.

The adaptive immune system of 5 vertebrates is mostly reliant on white blood cells. Infections and parasites are repelled by the white blood cells. The clotting of blood depends on platelets. Haemocytes are an essential component of the immune system of arthropods that use haemolymph.

The heart pumps blood via blood arteries to transport it throughout the body. In lung-equipped animals, arterial blood delivers oxygen from the air that is breathed into the body's tissues, while venous blood transfers carbon dioxide, a waste product of cell metabolism, from the tissues to the lungs for exhalation.

Blood Vessels

The arteries, veins, and capillaries make up the circulatory system's blood vessels. The term "great vessels" refers to the sizable arteries and veins that carry blood to and from the heart.

1. Arteries

Blood is transported from the heart through arteries. The tunica intima, tunica medium, and tunica externa are the three layers that make up the arterial walls. The thickest layer is often in the centre. It is composed of smooth muscle, which alters the artery's size to control blood flow. The three primary artery kinds are as follows:

a) Elastic arteries

The elastic arteries are the aorta and pulmonary arteries. In order to handle the surge and contraction caused by the blood pushing through with each pulse, they must be elastic as they get blood straight from the heart. The aorta is the most significant artery in the body. Deoxygenated blood is delivered to the lungs through pulmonary arteries from the right ventricle. They are the only arteries that transport blood that has lost oxygen.

b) Muscle arteries

Blood is transported across the body by the muscular arteries from the elastic arteries. They are constructed of smooth muscle that may swell and contract in response to blood flow. Examples of muscular arteries are the femoral and coronary arteries.

c) Arterioles

The arterioles, which carry blood from the muscle arteries to the capillaries, are the tiniest. The capillaries link the veins that bring blood to the heart with the arteries that carry blood away from the heart.

The volume of material exchange affects how many capillaries are present in a biological system. Because their bodily systems need a lot of oxygen and nutrients, skeletal muscle, the liver, and the kidney, all contain a lot of capillaries. One part of the eye without capillaries is the cornea.

2. Veins

Veins allow the blood to return to the heart. The venules, the tiniest veins, are where the blood exits the capillaries. The veins enlarge more and more as the blood flows towards the heart. The tunica intima, tunica medium, and tunica externa are layers that make up the walls of veins, much as the arteries.

The arteries and veins vary significantly in a number of significant ways.

• Veins contain less connective tissue and smooth muscle in their walls.
• Vein walls are more delicate than artery walls.
• Veins are able to retain more blood than arteries and are under less pressure.

Approximately 70% of the body's total blood flow is found in the veins at any moment.

3. Capillaries

These blood channels link venules, which are tiny veins, to arteries, which are also tiny. As a result of the capillaries' thin walls, nutrients, waste products, carbon dioxide, and oxygen may enter and leave cells.

Development of the Circulatory System

Vasculogenesis in the developing embryo is the first step in the formation of the circulatory system. The venous and arterial systems of the human body originate in various parts of the embryo. The six pairs of aortic arches that form on the top section of the embryo serve as the primary source of development for the arterial system. From weeks 4 to 8 of development, three bilateral veins give birth to the venous system. Within the eighth week of development, foetal circulation starts. The truncus arteriosus serves as a bypass for the lungs, which are not part of the foetal circulation. Through the placenta and the umbilical cord, the foetus receives oxygen (and nutrients) from the mother prior to delivery.

What is the Mechanism of the Circulatory System?

Blood vessels, which comprise arteries, veins, and capillaries, support the circulatory system in your body. Blood is regularly circulated throughout your body via these blood veins, your heart, and your lungs as follows:

• Oxygen-poor blood is sent to the lungs via the right ventricle, the bottom chamber of the heart that pumps blood. The pulmonary trunk, or major pulmonary artery, carries blood.
• In the lungs, blood cells absorb oxygen.
• The oxygenated blood from the lungs is transported by pulmonary veins to the left atrium, which is the upper chamber of the heart.
• The left ventricle (lower chamber) receives oxygenated blood from the left atrium. Blood is pumped out to the body via the arteries by this heart's muscular portion.
• Blood picks up and releases waste items, hormones, and nutrients as it circulates around your body and organs.
• Deoxygenated blood and carbon dioxide are returned to the heart via the veins, where they are then sent to the lungs.
• When you exhale, your lungs get rid of the carbon dioxide.

Conditions Affecting the Cardiovascular System

Cardiovascular disease refers to illnesses that impact the cardiovascular system.

Many of these illnesses are referred to as "lifestyle diseases" because they progress gradually and are connected to a person's eating patterns, exercise routines, smoking status, and other lifestyle decisions. Many of these disorders have atherosclerosis as their antecedent. In the walls of the medium and large arteries, here is where tiny atheromatous plaques accumulate. This might ultimately expand or break, occluding the arteries. Acute coronary syndromes, which are disorders marked by a sudden shortage of oxygenated blood to the heart tissue, are also at danger due to it. Additionally, atherosclerosis is linked to issues like artery splitting (or "dissection") and the development of aneurysms.

A clot known as a "thrombus" is produced as a result of another serious cardiovascular illness. These may come from arteries or veins. One reason for blood clots in the veins of the legs, especially after spending a lot of time sitting still, is deep venous thrombosis, which predominantly affects the legs. These clots might embolise, or move to another part of the body. Pulmonary embolism, transient ischemic attacks, or stroke might arise from this.

Congenital cardiovascular illnesses, such as prolonged foetal circulation or cardiac abnormalities, occur when the circulatory alterations that should occur after birth do not. Many congenital differences in the circulatory system are anatomical variances rather than illnesses.

The heart and circulatory system may be impacted by a number of disorders, including:

1. Coronary artery disease

Blood flow is reduced in the arteries of the legs as a result of peripheral arterial disease. Plaque accumulation in the arteries is often to blame for this.

2. Arteriosclerosis

Plaque accumulation in the blood arteries hardens and calcifies in arteriosclerosis. Less elasticity in the arteries increases blood pressure and the risk of stroke, heart disease, and kidney damage.

3. Heart attack

Heart muscle tissue dies when the blood supply to the heart muscle is obstructed during a heart attack. Another name for it is a myocardial infarction.

4. Angina

The heart muscle isn't receiving enough blood when you have angina. This results in excruciating chest discomfort, exhaustion, motion sickness, and shortness of breath.

5. Issues with the mitral valve

With mitral valve disorders such as mitral valve prolapse, stenosis, or regurgitation, oxygenated blood in the heart flows backwards, or blood flow is impeded or restricted.

6. Dysrhythmias or arrhythmias

Both of these phrases are used to denote an abnormal heart rate.

7. Ischemia

Muscles with ischemia get insufficient oxygen due to insufficient cardiac blood flow.

8. Aortic disease

This collection of ailments impacts the aorta. An aortic aneurysm is one instance in which the aorta is weak and protrudes outward.

Poor Circulation Signs and Symptoms

Poor circulation has a wide range of signs, including:

• Chest pain
• A sense of faintness or wooziness
• Breathing difficulty
• The limbs are painful, weak, or numbed
• Swelling in limbs
• Palpitations, or a fast or sluggish heartbeat,
• Fatigue

The signs and symptoms vary according to the kind of cardiovascular disorder. For instance, the next leg and foot issues may result from peripheral arterial disease:

• Walking or resting with cramped legs
• Frigid legs or feet
• The colour shift in the legs
• Change in the thickness or colour of the toe-nail
• The legs and feet are losing hair
• In the legs and feet, ulcers (sores) that do not heal

How to Avoid Circulatory System Issues?

Your circulatory system may be preserved by doing the following actions:

• Aim for 150 minutes or more of physical exercise every week.
• Consume a diet low in processed foods and high in fibre and veggies for heart health.
• Try to relax in a healthy manner.
• Hold onto a healthy weight.
• Organise treatment for ailments including diabetes, hypertension, and high cholesterol.
• Avoid smoking.