Cardiovascular System: Blood Vessels

Blood vessels are an essential component of the circulatory system that transport blood to and from the heart. They can be classified into three types based on their function and structure: arteries, capillaries, and veins. We will examine each of these types in detail and explore the unique features of the three subtypes within each category. The walls of the blood vessels are divided into three layers, or tunics, that form their structure and function. These tunics are the tunica intima, tunica media, and tunica externa. In this article, we will examine each of these tunics in more detail.

Tunics of Blood Vessels

Tunica Intima

The tunica intima is the innermost layer of the blood vessels and is composed of endothelial cells that line the lumen of the vessel. This layer is in direct contact with the blood and is responsible for regulating the exchange of materials between the blood and the surrounding tissues. The endothelial cells also produce substances that help to prevent blood clotting and promote blood flow. Beneath the endothelial layer, there is a thin layer of connective tissue called the subendothelial layer. This layer is composed of collagen fibers, elastic fibers, and smooth muscle cells that help to stabilize the vessel wall and regulate its elasticity. In larger vessels, such as arteries and veins, the tunica intima also contains a layer of elastic tissue called the internal elastic lamina. This layer helps to provide support and maintain the structure of the vessel wall.

Tunica Media

The tunica media is the middle layer of the blood vessels and is composed of smooth muscle cells, elastic fibers, and collagen fibers. This layer is responsible for regulating the diameter of the vessel and controlling blood pressure and blood flow. The smooth muscle cells in the tunica media can contract and relax to adjust the size of the vessel and regulate blood flow.

In larger arteries, the tunica media is well-developed and contains a thick layer of smooth muscle cells. The smooth muscle cells are arranged in circular layers, and the contraction of these cells helps to increase blood pressure and flow. The tunica media of veins is thinner than that of arteries and contains fewer smooth muscle cells.

Tunica Externa

The tunica externa, also known as the tunica adventitia, is the outermost layer of the blood vessels and is composed of connective tissue, including collagen and elastic fibers. This layer provides support and protection for the vessel and helps to anchor it in place. In larger vessels, the tunica externa also contains small blood vessels called vasa vasorum, which supply nutrients to the outer layers of the vessel wall.

Blood Vessels

Arteries

Arteries are blood vessels that carry blood away from the heart and towards the body's tissues. They have thick, muscular walls that can contract and relax to regulate blood flow. The three subtypes of arteries are elastic arteries, muscular arteries, and arterioles.

·         Elastic arteries are the largest arteries in the body and are found closest to the heart. They have the ability to stretch and recoil in response to changes in blood pressure, which helps to maintain consistent blood flow. Examples of elastic arteries include the aorta and the pulmonary artery.

·         Muscular arteries are smaller than elastic arteries but still have a significant amount of smooth muscle in their walls. They can adjust their diameter to control blood flow to specific areas of the body. Examples of muscular arteries include the brachial artery and the femoral artery.

·         Arterioles are the smallest arteries and are responsible for regulating blood flow to individual capillary beds. They have less muscle than muscular arteries but still play a crucial role in maintaining blood pressure and blood flow throughout the body.

Capillaries

Capillaries are the smallest blood vessels in the body and are responsible for exchanging nutrients, gases, and waste products between the blood and the body's tissues. They have thin walls that allow for the exchange of materials and are permeable to molecules such as oxygen, carbon dioxide, and glucose. The three subtypes of capillaries are continuous capillaries, fenestrated capillaries, and sinusoidal capillaries.

·         Continuous capillaries are the most common type of capillary and are found in most tissues of the body. They have tightly packed endothelial cells that allow for the diffusion of small molecules between the blood and the tissues.

·         Fenestrated capillaries are found in organs that require rapid exchange of materials, such as the kidneys and intestines. They have pores in their walls that allow for the exchange of larger molecules such as proteins and hormones.

·         Sinusoidal capillaries are the largest type of capillary and are found in organs such as the liver, spleen, and bone marrow. They have large gaps in their walls that allow for the exchange of blood cells in and out of the vasculature.

Veins

Veins are blood vessels that carry blood back to the heart. They have thinner walls than arteries and rely on the  contraction of nearby muscles to help move blood against gravity. The three subtypes of veins are venules, medium veins, and large veins.

·         Venules are the smallest veins and connect capillaries to larger veins. They have thin walls and are responsible for draining blood from individual capillary beds.

·         Medium veins are larger than venules and have valves in their walls that prevent the backflow of blood. They rely on nearby muscles to help move blood back to the heart.

·         Large veins are the largest veins in the body and include the superior and inferior vena cava. They have the thickest walls of any type of vein and rely on the contraction of smooth muscle in their walls to move blood back to the heart.

Blood vessels are a critical component of the circulatory system and play a crucial role in transporting blood throughout the body while maintaining appropriate blood pressure. By understanding the unique features of each type of blood vessel, we can gain a better understanding of how the circulatory system functions and how it can be affected by various diseases and disorders.

Unlike arteries, which have a muscular wall and experience higher pressure due to the pumping action of the heart, veins have thinner walls and rely on several mechanisms to facilitate the movement of blood against gravity. Two important mechanisms involved in venous return are the skeletal muscle pump and the thoracic muscle pump.

The skeletal muscle pump operates primarily in the limbs, where it assists in returning blood from the lower extremities back to the heart. It relies on the contraction and relaxation of skeletal muscles, which surround and compress the veins. When skeletal muscles contract during physical activity or movement, they exert pressure on the veins running through them. This compression narrows the veins, forcing the blood within them to move in the direction of the heart. The venule valves present within the veins prevent backward flow, ensuring that blood is pushed towards the heart rather than back down.

The sequential contraction and relaxation of skeletal muscles along the veins create a pumping effect. As one muscle contracts, it compresses the vein, propelling blood towards the next muscle. When the first muscle relaxes and the next muscle contracts, the blood is pushed further along the vein. This coordinated muscular action facilitates the continuous movement of blood towards the heart, even against gravity. The skeletal muscle pump is particularly effective during activities that involve repetitive contraction and relaxation of the leg muscles, such as walking or running. It helps to counteract the effects of gravity, preventing blood from pooling in the lower extremities and aiding in venous return.

The thoracic muscle pump, also known as the respiratory pump, assists in venous return from the upper body, including the thorax, neck, and head. It relies on changes in thoracic pressure that occur during the respiratory cycle. During inhalation, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity. Simultaneously, the external intercostal muscles between the ribs contract, causing the rib cage to expand. These actions result in a decrease in thoracic pressure. As a consequence, the pressure within the thoracic veins, such as the superior vena cava and jugular veins, decreases as well. The decreased thoracic pressure during inhalation promotes venous return by allowing blood to flow from the peripheral veins and venous sinuses of the head and neck towards the heart. During exhalation, the diaphragm relaxes, moving upward, and the external intercostal muscles relax, causing the rib cage to contract. This results in an increase in thoracic pressure, helping to squeeze blood within the thoracic veins and propel it towards the heart.

It is important to note that the skeletal muscle pump and the thoracic muscle pump work in conjunction with other factors that influence venous return, such as the presence of one-way valves within veins and the pressure gradient established by the pumping action of the heart. Additionally, factors like hydration, physical activity, and maintaining proper posture can also affect the efficiency of these mechanisms.

Major Vessels of the Body

The circulatory system is responsible for transporting oxygen, nutrients, hormones, and other essential substances throughout the body. It comprises a complex network of blood vessels, including arteries, veins, and capillaries. Arteries carry oxygenated blood away from the heart to various tissues, while veins return deoxygenated blood back to the heart.

Major Arteries

Pulmonary Circuit

·         The pulmonary trunk carries deoxygenated blood from the right ventricle of the heart to the left and right pulmonary arteries.

o    The pulmonary arteries carry blood to the lungs for oxygenation. There are two pulmonary arteries, one for each lung.

Systemic Circuit

·         The aorta is the largest artery in the body and emerges from the left ventricle of the heart. It carries oxygenated blood from the heart to the rest of the body.

o    The ascending aorta originates from the left ventricle and supplies blood to the coronary arteries, which nourish the heart muscle.

o    The aortic arch gives rise to three major branches:

§  The brachiocephalic trunk is the third branch of the aorta and divides right common carotid and right subclavian.

·         The right common carotid artery supplies the right side of the head and neck

·         The right subclavian artery supplies the right arm and other structures.

§  The left common carotid artery supplies the left side of the head and neck.

§  The left subclavian artery supplies the left arm and other structures.

§  The common carotid arteries are on each side of the neck. They divide into internal and external carotid arteries:

·         The internal carotid arteries supply blood to the brain, eyes, and other structures within the skull.

·         The external carotid arteries supply blood to the face, scalp, and neck muscles.

§  The subclavian arteries are one on each side of the body. They arise from the aortic arch and supply blood to the arms, shoulders, and other structures.

·         The vertebral arteries are two major arteries that arise from the subclavian arteries in the neck. They enter the vertebral column through the transverse foramina of the cervical vertebrae and unite to form the basilar artery. The vertebral arteries supply blood to the brainstem, cerebellum, and posterior part of the brain.

·         The axillary artery extends from the subclavian artery into the armpit region, supplying the shoulder and upper arm.

·         The brachial artery is a continuation of the axillary artery and supplies the arm.

o    The radial artery runs along the thumb side of the forearm and supplies the forearm and hand.

o    The ulnar artery runs along the little finger side of the forearm and supplies the forearm and hand.

o    The palmar arches are arterial networks located in the hand. There are two palmar arches: the superficial palmar arch and the deep palmar arch. They are formed by the radial and ulnar arteries and supply blood to the palm and fingers.

o    The thoracic aorta is the upper segment of the descending aorta and is located within the thoracic cavity. It gives rise to several important branches:

§  The bronchial arteries supply blood to the bronchial tubes of the lungs, nourishing the lung tissue.

§  The esophageal arteries supply blood to the esophagus, providing oxygen and nutrients to the esophageal walls.

§  The mediastinal arteries supply blood to the tissues within the mediastinum, including the thymus, lymph nodes, and other structures.

§  The pericardial arteries supply blood to the pericardium, the membrane surrounding the heart.

§  The intercostal arteries run between the ribs and supply blood to the muscles, bones, and other structures of the chest wall.

o    The abdominal aorta is the lower segment of the descending aorta and is situated within the abdominal cavity. It provides blood supply to various organs and structures within the abdomen and pelvis. The abdominal aorta gives rise to several important branches.

§  The celiac trunk (or celiac artery) is the first major branch of the abdominal aorta and supplies blood to the stomach, liver, spleen, and parts of the pancreas.

§  The superior mesenteric artery arises just below the celiac trunk and supplies blood to the small intestine, cecum, ascending colon, and part of the transverse colon.

§  The inferior mesenteric artery is located just above the bifurcation of the abdominal aorta and supplies blood to the descending colon, sigmoid colon, and rectum.

§  The renal arteries arise near the level of the superior mesenteric artery and supply blood to the kidneys, playing a vital role in the filtration and regulation of waste products.

§  The gonadal arteries are responsible for supplying blood to the reproductive organs. In males, they are called the testicular arteries, and in females, they are known as the ovarian arteries.

§  The lumbar arteries arise from the posterior aspect of the abdominal aorta and supply blood to the muscles and structures of the lower back.

§  The common iliac arteries divides into the left and right common iliac arteries, which supply blood to the pelvis and lower limbs. These arteries were discussed in a previous response. Each common iliac artery divides into the internal and external iliac arteries.

·         The external iliac artery supplies blood to the lower limbs, including the thighs.

·         The femoral artery is a continuation of the external iliac artery and supplies the thigh.

·         The popliteal artery is located behind the knee and is a continuation of the femoral artery. It supplies the knee joint and calf muscles.

·         The anterior tibial artery descends through the front of the leg and supplies the anterior compartment of the leg and the dorsum of the foot.

·         The dorsalis pedis artery is located on the top of the foot, between the first and second metatarsal bones. It is a continuation of the anterior tibial artery and supplies blood to the dorsum (upper surface) of the foot.

·         The posterior tibial artery runs down the back of the leg and supplies the posterior compartment of the leg and the sole of the foot.

o    The fibular artery (peroneal) is a branch of the posterior tibial artery and supplies the lateral compartment of the leg and the lateral side of the foot.

·         The plantar arch is a major arterial network located on the sole of the foot. It is formed by the continuation of the posterior tibial artery and the lateral plantar artery. The plantar arch supplies blood to the muscles, skin, and other structures of the foot.

Major Veins

Pulmonary Circuit

·         The right pulmonary veins originate from the right lung. They carry oxygenated blood from the capillaries within the lung tissue and merge to form a single right pulmonary vein before entering the posterior aspect of the left atrium of the heart.

·         The left pulmonary veins arise from the left lung. They carry oxygenated blood from the lung capillaries and merge to form a single left pulmonary vein before entering the posterior aspect of the left atrium of the heart.

Systemic Circuit

·         The superior vena cava is a large vein that collects deoxygenated blood from the upper body and delivers it to the right atrium of the heart. While the superior vena cava does not have many branches, it receives blood from several major veins, including:

o   The brachiocephalic vein (innominate vein) is formed by the union of the internal jugular vein and the subclavian vein on each side of the body. The left and right brachiocephalic veins join together to form the superior vena cava.

§  The external jugular vein is a major superficial vein located on the side of the neck. It receives blood from the scalp, face, and superficial structures of the neck. It descends in the neck region and drains into the subclavian vein.

§  The internal jugular vein is a major deep vein that runs parallel to the external jugular vein in the neck. It collects blood from the brain, face, and neck. The internal jugular vein, along with the subclavian vein, forms the brachiocephalic vein.

§  The subclavian veins receive blood from the arms, shoulders, and other structures and drain into the superior vena cava.

·         The brachial vein accompanies the brachial artery and runs parallel to it. It collects deoxygenated blood from the deep structures of the upper arm.

·         The basilic vein is a large superficial vein that runs along the medial side of the arm. It merges with the brachial vein to form the axillary vein.

o    The median antebrachial vein is a superficial vein located on the anterior surface of the forearm. It ascends along the midline of the forearm and drains into the basilic vein.

·         The cephalic vein is a prominent superficial vein that runs along the lateral side of the arm. It drains into the axillary vein.

·         The median cubital vein connects the basilic and cephalic veins in the anterior elbow region.

·         The radial veins accompany the radial artery and drain the lateral side of the forearm and hand.

·         The ulnar veins accompany the ulnar artery and drain the medial side of the forearm and hand.

·         The palmar venous arches (superficial and deep are networks of veins located on the palm of the hand. There are superficial and deep palmar venous arches. The superficial palmar venous arch is located closer to the surface of the skin, while the deep palmar venous arch is located deeper within the hand. They receive blood from the digital veins and help drain blood from the hand.

·         The digital veins are small veins located in the fingers and toes. They drain blood from the capillaries of the digits and contribute to the venous return from the extremities.

o   The azygos vein is a single vein on the right side of the body that ascends along the thoracic vertebral column. The azygos vein drains blood from the posterior wall of the thorax and the abdominal wall.

§  The hemiazygos vein and accessory hemiazygos vein are smaller branches of the azygos vein. They drain blood from the left posterior wall of the thorax.

§  The intercostal veins are a series of veins that run parallel to the ribs. They drain blood from the intercostal spaces (spaces between the ribs) and carry it back to the azygos vein on the right side or the hemiazygos vein on the left side. These veins play a role in draining blood from the chest wall.

·         The inferior vena cava is the largest vein in the body and carries deoxygenated blood from the lower body back to the right atrium of the heart. The inferior vena cava receives blood from various veins, including:

o   The lumbar veins drain blood from the muscles and tissues of the lower back.

o   The renal veins drain deoxygenated blood from the kidneys and transport it to the inferior vena cava.

o   The hepatic veins drain deoxygenated blood from the liver and transport it to the inferior vena cava.

o   The gonadal veins, known as the testicular vein in males and the ovarian vein in females, drain deoxygenated blood from the reproductive organs and empty into the inferior vena cava.

o   The common iliac veins are formed by the union of the external iliac vein (which drains the lower limbs) and the internal iliac vein (which drains the pelvic organs). The left and right common iliac veins join together to form the inferior vena cava.

§  The femoral vein accompanies the femoral artery in the thigh and is a continuation of the popliteal vein. It drains blood from the thigh and deep structures of the leg.

·         The deep femoral vein, also known as the profunda femoris vein, accompanies the deep femoral artery in the thigh. It drains blood from the deep structures of the thigh and merges with the femoral vein.

§  The popliteal vein is located behind the knee and is formed by the merging of the anterior and posterior tibial veins. It drains the blood from the calf muscles and knee joint.

·         The fibular vein, also known as the peroneal vein, accompanies the fibular artery in the leg. It drains blood from the lateral compartment of the leg and joins the posterior tibial vein to form the popliteal vein.

·         The posterior tibial vein accompanies the posterior tibial artery in the leg. It drains blood from the posterior compartment of the leg and the sole of the foot. The posterior tibial vein combines with the fibular vein to form the popliteal vein.

§  The anterior tibial vein accompanies the anterior tibial artery and drains the anterior compartment of the leg and the dorsum of the foot.

§  The great saphenous vein is the longest vein in the body and runs along the medial side of the leg. It starts from the foot and ascends to the groin, where it drains into the femoral vein.

§  The small saphenous vein is located on the posterior side of the leg and drains into the popliteal vein.

§  The plantar venous arch is a network of veins located on the sole of the foot. It collects blood from the digital veins and other foot veins and helps with the venous return from the foot.

§  The dorsal venous arch is a network of veins located on the top surface of the foot. It collects blood from the digital veins and other superficial foot veins and helps drain blood from the foot.

The function of arteries is to carry blood away from the heart, supplying tissues and organs with essential oxygen and nutrients. Veins, on the other hand, carry blood back to the heart, where in the pulmonary circuit it will be reoxygenated in the lungs and then pumped to the rest of the body. Veins also play a role in removing waste products from the tissues.

Blood Pressure

Blood pressure is the force that blood exerts on the walls of blood vessels as it flows through them. It is an important physiological parameter that helps to maintain blood circulation and deliver oxygen and nutrients to tissues throughout the body. Blood pressure is measured in millimeters of mercury (mmHg) and is typically recorded as two numbers: systolic pressure and diastolic pressure.

·         Systolic pressure is the pressure exerted by blood when the heart contracts and pumps blood into the arteries. This is the highest pressure recorded during a blood pressure measurement.

·         Diastolic pressure, on the other hand, is the pressure exerted by blood when the heart is at rest between contractions. This is the lowest pressure recorded during a blood pressure measurement.

Blood pressure is regulated by a complex interplay of various physiological mechanisms. The main factors that influence blood pressure include the volume of blood in the circulatory system, the strength and frequency of the heart's contractions, the diameter and elasticity of blood vessels, and the activity of the sympathetic and parasympathetic nervous systems.

One of the most important regulators of blood pressure is the renin-angiotensin-aldosterone system (RAAS). This system helps to regulate blood pressure by controlling the amount of sodium (Na+) and water that is reabsorbed by the kidneys. When blood pressure drops, the kidneys release an enzyme called renin, which converts angiotensinogen into angiotensin I. Angiotensin I is then converted into angiotensin II by an enzyme called angiotensin-converting enzyme (ACE). Angiotensin II causes vasoconstriction (narrowing of blood vessels), which increases blood pressure, and stimulates the release of aldosterone from the adrenal glands. Aldosterone promotes the reabsorption of Na+ and water in the kidneys, which also helps to increase blood pressure.

The sympathetic nervous system also plays an important role in regulating blood pressure. When blood pressure drops, the sympathetic nervous system is activated, which increases heart rate and cardiac output (the amount of blood pumped by the heart per minute), constricts blood vessels, and stimulates the release of renin from the kidneys. These responses help to increase blood pressure and restore blood flow to vital organs.

Conversely, the parasympathetic nervous system helps to lower blood pressure by decreasing heart rate and cardiac output and dilating blood vessels. This system is activated during periods of rest and relaxation, and helps to maintain blood pressure within a healthy range.

Blood pressure can be affected by a variety of factors, including age, sex, genetics, lifestyle habits (such as diet and exercise), medications, and underlying health conditions (such as diabetes and kidney disease).

·         High blood pressure (hypertension) is a common medical condition that can increase the risk of heart disease, stroke, and other serious health problems.

·         Low blood pressure (hypotension) can also be a cause for concern, particularly if it is accompanied by symptoms such as dizziness and fainting.

Taking Blood Pressure

Blood pressure is the pressure exerted by the blood against the walls of the blood vessels, and it is an important indicator of cardiovascular health. In this guide, we will outline the steps involved in taking blood pressure measurements, which are commonly used in medical settings to assess a person's health status.

Before taking a blood, pressure reading, it is important to note that there are two types of blood pressure measurements: systolic pressure and diastolic pressure. Systolic pressure is the pressure exerted by the blood against the walls of the arteries when the heart beats, while diastolic pressure is the pressure exerted by the blood against the walls of the arteries when the heart is at rest, between beats.

To take a blood pressure measurement, you will need a sphygmomanometer (blood pressure cuff) and a stethoscope. Here are the steps involved in taking blood pressure:

1.   Prepare the patient

o   Ensure that the patient is in a comfortable and relaxed state, sitting in a chair with their feet on the ground and their arm resting on a flat surface at heart level. It is important to make sure the patient has not consumed caffeine or engaged in physical activity for at least 30 minutes before the reading.

2.   Wrap the blood pressure cuff around the patient's upper arm

o   The cuff should be placed snugly around the upper arm, with the lower edge of the cuff about 2.5 cm above the elbow crease. The cuff should be tight enough to prevent any air from escaping, but not so tight that it causes discomfort or pain.

3.   Locate the brachial artery

o   Using the stethoscope, locate the brachial artery in the bend of the elbow on the inside of the arm.

4.   Inflate the cuff

o   Using the hand pump, inflate the cuff until the gauge reads 180 mmHg (potentially 200 mmHg in extreme hypertension).

5.   Release the pressure in the cuff

o   Slowly release the pressure in the cuff at a rate of 2-3 mmHg per second by turning the release valve on the hand pump.

6.   Listen for the sounds of Korotkoff

o   Place the stethoscope over the brachial artery and listen for the sounds of Korotkoff, which are the sounds of blood flowing through the artery as the pressure in the cuff is released. The first sound represents the systolic pressure, and the point at which the sounds disappear represents the diastolic pressure.

7.   Record the blood pressure reading

o   Once the sounds disappear, note the reading on the gauge. This is the patient's blood pressure reading, with the systolic pressure represented by the first number and the diastolic pressure represented by the second number. For example, a reading of 120/80 mmHg represents a systolic pressure of 120 mmHg and a diastolic pressure of 80 mmHg.

8.   Repeat the measurement

o   If the first measurement indicates a high or low blood pressure, repeat the measurement to ensure accuracy.

Taking blood pressure measurements is an important skill for healthcare professionals to have, as it provides valuable information about a patient's cardiovascular health. By following these steps, you can ensure accurate and reliable blood pressure readings.

Overview

The cardiovascular system consists of blood vessels that transport blood to and from the heart. There are three types of blood vessels: arteries, capillaries, and veins. Each type has unique features and functions. The walls of blood vessels are composed of three layers called tunics: the tunica intima, tunica media, and tunica externa.

The tunica intima is the innermost layer and consists of endothelial cells that regulate the exchange of materials between the blood and surrounding tissues. Beneath the endothelial layer is the subendothelial layer, which stabilizes the vessel wall. In larger vessels, the tunica intima also contains the internal elastic lamina for support.

The tunica media is the middle layer and consists of smooth muscle cells, elastic fibers, and collagen fibers. It regulates the diameter of the vessel and controls blood pressure and flow. Muscular arteries have a well-developed tunica media, while veins have a thinner tunica media.

The tunica externa is the outermost layer and is composed of connective tissue. It provides support, protection, and anchoring for the vessel. In larger vessels, the tunica externa contains vasa vasorum, small blood vessels that supply nutrients to the vessel wall.

Arteries carry blood away from the heart and have thick, muscular walls. There are three subtypes of arteries: elastic arteries, muscular arteries, and arterioles. Elastic arteries, like the aorta, can stretch and recoil to maintain consistent blood flow. Muscular arteries adjust their diameter to control blood flow to specific areas. Arterioles regulate blood flow to individual capillary beds.

Capillaries are the smallest blood vessels and facilitate the exchange of nutrients, gases, and waste products between the blood and tissues. There are three subtypes of capillaries: continuous, fenestrated, and sinusoidal. Continuous capillaries are the most common, fenestrated capillaries have pores for rapid exchange, and sinusoidal capillaries have large gaps for the exchange of cells and large molecules.

Veins carry blood back to the heart and have thinner walls than arteries. There are three subtypes of veins: venules, medium veins, and large veins. Venules connect capillaries to larger veins, medium veins have valves to prevent backflow, and large veins, like the superior and inferior vena cava, rely on smooth muscle contractions to move blood.

Blood pressure is the force exerted by blood against the walls of blood vessels. It is measured as systolic pressure (during heart contraction) and diastolic pressure (during heart relaxation). Blood pressure is regulated by factors such as blood volume, heart contractions, vessel diameter and elasticity, and the sympathetic and parasympathetic nervous systems. The renin-angiotensin-aldosterone system and the sympathetic nervous system play significant roles in regulating blood pressure.

Taking accurate blood pressure measurements is crucial for assessing cardiovascular health, and healthcare professionals follow specific steps to ensure reliable readings.