The Blood Vessels > Discover your body
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The circulatory system
Did you know that the circulatory system in your body stretches for more than 60,000 miles?
In this video, you will learn that this is the most important system in our bodies. It is responsible for bringing blood, nutrients, and oxygen to all parts of the body, as well as for healing wounds. You can see why this is such an important process! There are two parts that make up the circulatory system: the heart and blood vessels. Blood vessels include arteries, veins, and capillaries. The heart has four chambers total—two ventricles and two atria. The left and right ventricles of the heart are located at the bottom. These chambers pump blood out of the heart. The left and right atria at the top of the heart receive blood into the heart. Every time your heart beats, these four chambers are doing their job!
The other part is the collection of blood vessels. Arteries carry blood away from the heart, veins carry blood to the heart, and capillaries connect arteries and veins. Because blood contains the nutrients and oxygen we need, our blood vessels are responsible for getting those important things to all parts of the body. As you now know, blood contains several important things. Besides nutrients and oxygen, blood also carries plasma, which is a yellowish liquid. This liquid is responsible for carrying proteins, nutrients, and hormones to the rest of the body. It is made of mostly water that comes from the food and water we consume. Plasma also carries away waste from the cells.
Types of
Blood Vessels:
Arteries: Arteries are thick-walled vessels that carry oxygen-rich blood away from the heart.
Veins: Veins are thin-walled vessels that carry oxygen-poor blood back to the heart.
Capillaries: Capillaries are tiny vessels that connect arteries and veins. They allow oxygen and nutrients to pass from the blood into the body's tissues and waste products to pass from the body's tissues into the blood.
Arteries
Arteries
Arteries are thick-walled, muscular, and valveless blood vessels, that carry oxygen-rich blood away from the heart. They have a smooth inner lining that helps to keep blood flowing smoothly. Arteries also have strong walls that can withstand the high pressure of the blood. The largest artery in the body is the Aorta, which carries blood from the left ventricle of the heart to the rest of the body. Other major arteries include the Coronary arteries, which supply blood to the heart muscle, and the Pulmonary arteries, which carry oxygen-poor blood from the right ventricle of the heart to the lungs.
Types of Arteries
Based on the structure, arteries are mainly classified into 2 main types:
Elastic Arteries
These are the arteries that have a considerable amount of elastic fibers as their structural component in their tunica media layer. These arteries can expand and contract more significantly than other arteries due to the presence of elastic fibers. The Aorta, major branches of the aorta, and other major arteries (larger arteries) are elastic arteries.
Muscular Arteries
These arteries have a low amount of elastic fibers in the tunica media but contain a very high proportion of muscle cells. These arteries are branches of major arteries and function to supply blood to organs and tissues.
Types of Arteries
Based on the types of blood they carry and the location of delivery, arteries can be classified into two types:
Systemic Arteries
These arteries supply oxygenated blood from the left ventricle to every tissue of the body for cellular respiration and nutrient circulation.
Pulmonary Arteries
These arteries carry deoxygenated blood collected by veins from the right ventricle to the lungs for re-oxygenation i.e. exchange of metabolic CO2 with the atmospheric O2 at the alveoli of the lungs.
How big are arteries?
The Aorta, your largest artery, is about 10 millimeters (mm) to 25 mm in diameter
Other arteries can be 3 mm to 5 mm in diameter
while the smallest arteries, arterioles, can be .30 mm to .01 mm in diameter.
Structure of the Arterial Wall
The three layers of the artery wall work together to help the artery function properly.
The tunica externa provides support and protection
The tunica media regulates blood pressure
The tunica intima prevents blood clots from forming.
1. Tunica externa (outer layer)
The tunica externa is the outermost layer of the artery wall and it is made of connective tissue. It is responsible for providing support and protection for the artery. The tunica externa contains nerves and blood vessels that supply the artery with oxygen and nutrients.
2. Tunica media (middle layer)
The tunica media is the middle layer of the artery wall and it is made of smooth muscle. The smooth muscle cells in the tunica media are responsible for constricting and dilating the artery, which helps to regulate blood pressure. The tunica media also contains elastic fibers, which help to keep the artery walls from bursting under pressure.
3. Tunica intima (inner layer)
The tunica intima is the innermost layer of the artery wall and it is made of endothelial cells. The endothelial cells are responsible for lining the inside of the artery and preventing blood clots from forming. The tunica intima also contains a thin layer of connective tissue, which helps to keep the endothelial cells in place.
Veins
Veins
All veins carry the deoxygenated blood except the pulmonary veins and the umbilical veins. The pulmonary veins carry the oxygenated blood from the lungs to the left atrium for circulation. The umbilical veins carry the oxygenated blood from the placenta to the growing fetus. The umbilical veins are present only in the growing fetus. The other veins that carry the deoxygenated blood are called the systemic veins.
Systemic veins collect the deoxygenated blood from capillaries and ascend the blood back to the heart at lower pressure of about 8 to 10 mm of Hg; hence it needs valves, an elastic muscular structure to check the backflow of blood.
Veins are the blood vessels that collect the deoxygenated blood from the various tissues and organs of the body and transport it back to the heart. The blood vessels that carry blood toward the heart are veins.
Connected to the capillaries, the veins start as small finer tubules of about 8 to 100 μm in diameter, called the venules. The veins that are connected directly to the capillaries are called the post–capillary venules. Several venules merge forming a smaller vein. Different small veins unite forming larger veins that finally connect to form two major veins called the vena
Veins
Veins are thin-walled vessels that carry oxygen-poor blood back to the heart. They have a weaker muscular wall than arteries and are more flexible. This allows them to expand and contract as the blood volume changes. The largest vein in the body is the vena cava, which carries blood from the lower body to the heart. Other major veins include the pulmonary veins, which carry oxygen-rich blood from the lungs to the left atrium of the heart, and the jugular veins, which carry blood from the head and neck to the right atrium of the heart.
Structure of the Veins Wall
Veins are thin-walled valves containing blood vessels. Anatomically, veins have the same three layered walls as arteries that are the tunica externa, the tunica media, and the tunica intima; however, they have considerably lesser amounts of smooth muscles making them thinner than the walls of the arteries. This thinner wall makes the veins more flexible and allows the veins to hold nearly 70% of total blood at any time. The veins carry the blood at very low pressure so they are equipped with venous valves that keep the blood flowing towards the heart by checking the backflow.
1. Tunica Externa
It is the outermost layer primarily made of connective tissues mainly with collagen fibers providing physical strength and elasticity to the veins.
2. Tunica Media
It is the middle layer composed of connective tissue with elastic fibers and transverse layers of muscle fibers. The smooth muscle cells present in this layer help to regulate the diameter of veins.
3. Tunica Intima
It is the innermost smooth layer made from endothelial cells providing a smooth surface for easy flow of the blood inside the veins.
Types of Veins
Based on the location, they are classified into two types:
Superficial Veins
The veins that lie closer to the body surface underneath the skin are called the superficial veins. These veins are often visible as bluish-to-purple-colored veins. Besides blood transportation, they play an important role in regulating the body temperature. These veins carry a lesser amount of blood in our bodies. Some common and visible superficial veins are externa jugular veins, cephalic veins, cubital veins, basilica veins, etc.
Deep Veins
The veins that are located deeper within the body are called the deep veins. These veins are not visible from the outside and are often paired with arteries of the same name. These veins carry a major portion of venous blood. Some common deep veins are internal jugular veins, brachial veins, subclavian veins, femoral veins, etc.
Types of Veins
Based on the types of blood they carry and the location of delivery, veins can be classified into two types:
Systemic Veins
These veins collect and carry the deoxygenated blood from all over the body to the right atrium.
Pulmonary Veins
These veins carry the oxygenated blood from the lungs to the left atrium. There are four major pulmonary veins – two emerging from each lung.
Veins Primary Functions
Systemic veins collect the deoxygenated blood from every tissue and organ of our body and transport it back to the heart for reoxygenation and re-circulation.
Pulmonary veins carry the re-oxygenated blood from the lungs to the heart for re-circulation.
Superficial veins also help in decreasing body temperature when it gets hot.
Veins diverse functions
Returning deoxygenated blood to the heart:
Veins carry deoxygenated blood back to the heart. This blood has released its oxygen to the tissues and now needs to be re-oxygenated in the lungs. Veins have valves that prevent blood from flowing backwards.
Regulating blood pressure
The blood moving through the circulatory system puts pressure on the walls of the blood vessels. Blood pressure results from the blood flow force generated by the pumping heart and the resistance of the blood vessel walls. When the heart contracts, it pumps blood out through the arteries. The blood pushes against the vessel walls and flows faster under this high pressure. When the ventricles relax, the vessel walls push back against the decreased force. Blood flow slows down under this low pressure.
Veins help to regulate blood pressure by acting as a reservoir for blood. When blood pressure is high, veins can constrict to hold more blood. When blood pressure is low, veins can relax to release more blood into the circulation.
Helping to maintain body temperature
Veins help to maintain body temperature by carrying blood away from the body's core and towards the skin. When the body is hot, veins can dilate to release more heat. When the body is cold, veins can constrict to conserve heat.
Storing nutrients and horm
Veins can store nutrients and hormones, such as glucose and insulin. These nutrients and hormones can be released into the bloodstream when needed.
Transporting waste products
Veins transport waste products, such as carbon dioxide and urea, from the tissues back to the heart and lungs. These waste products are then removed from the body through breathing and urination.
Conclusion:
Veins are essential for the proper functioning of the circulatory system. They play a vital role in returning deoxygenated blood to the heart, regulating blood pressure, maintaining body temperature, storing nutrients and hormones, and transporting waste products.
Capillaries
CAPILLARIES
Capillaries
Capillaries are tiny vessels that connect arteries and veins. They are so small that red blood cells can only pass through them single file. Capillaries are located in all parts of the body, including the skin, muscles, and organs. They allow oxygen and nutrients to pass from the blood into the body's tissues and waste products to pass from the body's tissues into the blood. Capillaries are essential for exchange between the blood and the tissues.
Capillaries are tiny vessels that branch out from arterioles to form networks around body cells. In the lungs, capillaries absorb oxygen from inhaled air into the bloodstream and release carbon dioxide for exhalation. Elsewhere in the body, oxygen and other nutrients diffuse from blood in the capillaries to the tissues they supply. The capillaries absorb carbon dioxide and other waste products from the tissues and then flow the deoxygenated blood into the veins.
Exchange of Gases, Nutrients, and Waste Between Blood and Tissue Occurs in the Capillaries
Capillary Beds
What is a capillary bed?
The capillary bed definition is that of a network of small blood vessels, called capillaries, that perform a crucial role in the cardiovascular system.
The Capillary bed function allows for the exchange of water, carbob dioxide, oxygen, and nutrients, as well as to eliminate waste. It is a network of micro circulation to transport cellular and fluid materials to the surrounding organ system.
Lung Capillary
What are the functions of capillaries?
Capillaries have a number of important functions, including:
Carrying oxygen and nutrients to the tissues: Capillaries deliver oxygen and nutrients to the tissues from the blood. This is essential for the cells in the tissues to function properly.
Removing waste products from the tissues: Capillaries remove waste products, such as carbon dioxide and urea, from the tissues and carry them back to the blood. This is essential for the body to get rid of waste products.
Helping to regulate blood pressure: Capillaries can help to regulate blood pressure by constricting or dilating. When capillaries constrict, they become narrower and reduce blood flow. When capillaries dilate, they become wider and increase blood flow.
Helping to maintain body temperature: Capillaries help to maintain body temperature by carrying blood away from the body's core and towards the skin. When the body is hot, capillaries can dilate to release more heat. When the body is cold, capillaries can constrict to conserve heat.
What are capillaries made of?
Capillaries are made of three layers of tissue:
Tunica intima: The tunica intima is the innermost layer of the capillary wall. It is made of endothelial cells, which are specialized cells that line the inside of blood vessels.
Tunica media: The tunica media is the middle layer of the capillary wall. It is made of smooth muscle cells, which can constrict or dilate the capillary.
Tunica externa: The tunica externa is the outermost layer of the capillary wall. It is made of connective tissue, which provides support and protection for the capillary.
What are some common capillary disorders?
There are a number of common capillary disorders, including:
Telangiectasia: Telangiectasia are small, red, dilated blood vessels that are often found on the face.
Spider veins: Spider veins are larger, red, dilated blood vessels that are often found on the legs.
Purpura: Purpura are small, purple bruises that are caused by bleeding under the skin.
Petechiae: Petechiae are tiny, red spots that are caused by bleeding under the skin.
How to prevent capillary disorders
There are a number of things you can do to help prevent capillary disorders, including:
Avoiding smoking: Smoking can damage the walls of blood vessels and make them more likely to bleed.
Maintaining a healthy weight: Being overweight or obese can put extra strain on blood vessels and make them more likely to leak.
Eating a healthy diet: Eating a healthy diet can help to keep your blood vessels healthy.
Exercising regularly: Exercise can help to improve blood circulation and reduce the risk of blood vessel damage.
Protecting your skin from the sun: Exposure to ultraviolet (UV) light can damage the walls of blood vessels and make them more likely to leak.
Conclusion
Capillaries are essential for the proper functioning of the body. They play a vital role in the exchange of nutrients and waste between the blood and the tissues. By understanding the functions of capillaries and the factors that can affect them, you can help to keep your blood vessels healthy and prevent capillary disorders.
Capillaries are the smallest blood vessels that are found in all parts throughout the body, including the skin, muscles, and organs. They are so small that red blood cells can only pass through them in single file. Capillaries are like the "thin blood vessels" that carry blood to the body's tissues and organs.
Capillaries are important because they allow oxygen and nutrients to move from the blood into the tissues. They also allow waste products from the tissues to move back into the blood. Capillaries are like little bridges that connect the blood to the body's tissues.
There are many capillaries in the body. In fact, there are about 500-600 capillaries in every square millimeter of skin! Capillaries are so small that you can't see them with your naked eye, but you can see them under a microscope.
Capillaries are made of a single layer of cells called endothelial cells. These cells are very thin and flexible, which allows them to bend and stretch. This is important because capillaries need to be able to change shape in order to allow blood to flow through them.
Capillaries are an important part of the circulatory system. They help to keep the body's cells healthy and functioning properly.
Points To Remember
Points to Remember
How does the circulatory system work?
The heart pumps oxygenated blood from the left ventricle through the arteries to the body's tissues. The oxygen is then used by the cells to produce energy. The deoxygenated blood from the body's tissues then returns to the heart through the veins. The deoxygenated blood then enters the right atrium and then moves to the right ventricle. The right ventricle pumps the deoxygenated blood to the lungs through the pulmonary arteries. The blood then picks up oxygen from the lungs and returns to the heart through the pulmonary veins. The oxygenated blood then enters the left atrium and then moves to the left ventricle. The cycle then repeats.
Functions of the circulatory system
The circulatory system has many important functions, including:
Delivering oxygen and nutrients to the body's tissues
Removing waste products from the body's tissues
Regulating body temperature
Fighting infection
Transporting hormones throughout the body
Regulating blood pressure