The Circulatory System (01-02-2024) PDF

01-02-2024 ‫بسم هللا الرحمن الرحيم‬ The circulatory system also known as the cardiovascular system, is a vital organ system responsible for the transportation of blood, nutrients, gases, hormones, and waste products throughout the body. It consists of the heart, blood vessels,...

01-02-2024 ‫بسم هللا الرحمن الرحيم‬ The circulatory system also known as the cardiovascular system, is a vital organ system responsible for the transportation of blood, nutrients, gases, hormones, and waste products throughout the body. It consists of the heart, blood vessels, and blood. The main components of the circulatory system are: 1-.Heart: The heart is a muscular organ located in the chest cavity. It acts as a pump, continuously contracting and relaxing to pump blood throughout the body. The heart has four chambers: two atria (left and right) and two ventricles (left and right). The atria receive blood returning to the heart, while the ventricles pump blood out of the heart.  2-Blood Vessels: Blood vessels are an essential component of the circulatory system, responsible for transporting blood throughout the body. They come in three main types: arteries, veins, and capillaries. While each type of blood vessel has its own unique characteristics, there are some general features that apply to all of them..1Structure: Blood vessels Blood vessels have a layered structure consisting of three main layers: the tunica intima, tunica media, and tunica Adventita. The tunica intima is the innermost layer, composed of a single layer of endothelial cells that provide a smooth surface for blood flow. The tunica media is the middle layer, made up of smooth muscle cells and elastic fibers that allow the vessel to contract or relax to regulate blood flow and maintain blood pressure. The tunica externa is the outermost layer, composed of connective tissue that provides structural support and protection to the vessel.  2-Elasticity: Arteries have a higher proportion of elastic fibers in their walls, allowing them to stretch and recoil with each heartbeat, which helps to maintain a steady blood pressure. Veins, on the other hand, have thinner walls and less elastic tissue, making them more compliant and capable of expanding to accommodate larger volumes of blood..3--Diameter and lumen: Arteries have smaller lumens (the central opening of the blood vessel) compared to veins. This smaller diameter in arteries helps to maintain higher blood pressure to facilitate the efficient delivery of oxygenated blood to the body tissues. Veins have larger lumens that allow them to carry larger volumes of blood back to the heart..4-Valves: Veins contain one-way valves that prevent the backflow of blood. These valves are particularly important in the lower extremities, where they help to counteract the effects of gravity and assist in returning blood to the heart..5-- Capillaries: Capillaries are the smallest and thinnest blood vessels in the body. They consist of a single layer of endothelial cells, which allows for the exchange of nutrients, oxygen, carbon dioxide, and waste products between the blood and surrounding tissues. Capillaries have a large surface area, providing an optimal environment for the exchange of substances..6- Distribution: Arteries carry oxygenated blood away from the heart and supply it to various organs and tissues. Veins transport deoxygenated blood back to the heart. Capillaries connect arteries and veins, forming a network that enables the exchange of gases and nutrients with tissues. Overall, blood vessels play a vital role in maintaining proper circulation and ensuring the delivery of oxygen, nutrients, and other essential substances to all parts of the body. Their structure and function are intricately designed to support the complex demands of the circulatory system. Blood vessels are a network of tubes that transport blood to and from the heart and to various organs and tissues. There are three types of Blood vessels: a. Arteries: Arteries carry oxygenated blood away from the heart to the body's Tissues and organs. They have thick, elastic walls to withstand the high Pressure generated by the heart is pumping action. There are several types of arteries in the human body, each serving specific regions and organs. Here are some of the main types of arteries: 1. Elastic Arteries : These are large arteries, such as the aorta and its major branches. Elastic arteries have a high proportion of elastic fibers in their walls, allowing them to stretch and recoil as blood is pumped from the heart. This elasticity helps to maintain continuous blood flow and smooth out the pulsations caused by the heartbeat. The wall of an elastic artery is composed of three main layers:.1Tunica intima : This is the innermost layer of the artery and is in direct contact with the blood flowing through it. It consists of a single layer of endothelial cells, which provide a smooth surface for blood flow and help prevent clot  formation. The tunica intima also contains a thin layer of connective tissue called the subendothelium, which provides support. 2. -Tunica media: The tunica media is the middle layer of the artery and is primarily responsible for the elasticity and contractility of the artery. It contains smooth muscle cells, elastic fibers, and collagen fibers. The smooth muscle cells are arranged in a circular fashion around the artery and are responsible for regulating the diameter of the artery, thereby controlling blood flow. The elastic fibers, composed mainly of the protein elastin, allow the artery to stretch during systole (contraction phase of the heart) and recoil during diastole (relaxation phase of the heart). This elasticity helps to maintain continuous blood flow and pressure even when the heart is not actively pumping. 3. -Tunica adventitia (or tunica external): This is the outermost layer of the artery and is composed of connective tissue containing collagen fibers. It provides structural support and protection to the artery. The tunica adventitia also contains blood vessels called vasa vasorum, which supply oxygen and nutrients to the outer layers of the artery wall. Vasa vasorum: Is a network of small blood vessels that supply oxygen and nutrients tothe walls of larger blood vessels, such as arteries and veins The term "vasa vasorum" is Latin for "vessels of vessels." These blood vessels play a crucial role in maintaining the health and function of the larger blood vessels. The vasa vasorum are found in the tunica adventitia, which is the outermost layer of the blood vessel wall. In larger blood vessels, such as the aorta, vasa vasorum penetrate the tunica media, the middle layer of the vessel wall, to supply oxygen and nutrients to the cells in this region. The vasa vasorum help to nourish the cells of the blood vessel walls, especially in regions that are far from the lumen, or the inner space of the vessel. This is important because the cells in the outer layers of the blood vessel wall are further away from the oxygen and nutrients that are delivered through the lumen. The vasa vasorum provide an additional blood supply to these cells, ensuring their survival and proper function. In certain pathological conditions, such as atherosclerosis, the vasa vasorum can undergo changes. Inflammatory cells and growth of new blood vessels within the vessel wall can occur, contributing to the progression of the disease. Understanding the role of the vasa vasorum and their involvement in various vascular conditions is an active area of research in the field of cardiovascular medicine. 2-.Muscular Arteries : Also known as distributing arteries, muscular arteries are medium-sized arteries that distribute blood to specific organs and regions. They have a thick layer of smooth muscle in their walls, which allows them to constrict or dilate to regulate blood flow. Examples include the femoral artery in the thigh and the brachial artery in the arm. 3- Arterioles: Arterioles are small arteries that connect muscular arteries to capillaries. They have a significant role in regulating blood flow and blood pressure. By constricting or dilating, arterioles can control the amount of blood that reaches the capillaries and adjust blood flow to specific tissues and Organs.  4-Coronary Arteries : These arteries supply oxygenated blood to the heart muscle itself. The coronary arteries branch off from the aorta and encircle the heart, providing the necessary oxygen and nutrients for the heart's proper functioning. 5-.Cerebral Arteries : Cerebral arteries supply blood to the brain. The two main cerebral arteries are the internal carotid arteries and the vertebral arteries. They branch out to form an intricate network of blood vessels within the brain, ensuring a constant supply of oxygen and nutrients to brain cells..6- Renal Arteries : The renal arteries supply blood to the kidneys, Which are responsible for filtering waste products from the blood and regulating fluid balance. The renal arteries branch off from the abdominal aorta and deliver oxygenated blood to the kidneys.. b. Veins Veins carry deoxygenated blood from the body's tissues and organs back to the heart. They have thinner walls than arteries and contain valves to prevent blood from flowing backward. There are several types of veins in the human body, each serving a specific purpose in the circulatory system. Here are some of the main types of veins: 1-.Deep Veins Deep veins are located within the muscle tissue and are responsible for carrying the majority of the blood back to the heart. Examples of deep veins include the femoral vein in the thigh and the popliteal vein behind the knee.  2-.Superficial Veins: Superficial veins are closer to the surface of the body and are often visible beneath the skin. They play a lesser role in the overall blood transport but can serve as a backup in case of deep vein obstruction. Examples of superficial veins include the great saphenous vein in the leg and the basilic vein in the arm. 3-.Pulmonary Veins: Pulmonary veins are a unique type of vein that carry oxygenated blood from the lungs back to the heart. Unlike other veins, they carry oxygen- rich blood rather than deoxygenated blood. There are usually four pulmonary veins in the human body, two from each lung. 4- Portal Vein: The portal vein is responsible for carrying blood from the digestive organs, such as the stomach, intestines, and spleen, to the liver. It plays a crucial role in the liver's processing of nutrients, drugs, and other substances absorbed from the digestive system. 5- Sinusoids: Sinusoids are specialized veins found in certain organs, particularly the liver, bone marrow, and spleen. These veins have a unique structure that allows for the exchange of materials between the blood and surrounding tissue, facilitating various functions such as nutrient absorption and filtering c. Capillaries: Capillaries are tiny, thin-walled vessels that connect arteries and veins. They facilitate the exchange of oxygen, nutrients, and waste products between the blood and surrounding tissues. Capillaries are the smallest blood vessels in the human body, and they play a vital role in the exchange of oxygen, nutrients, and waste products between the blood and surrounding tissues. While there are no specific "types" of capillary blood, capillaries themselves can be classified into different types based on their structure and function. Here are the main types of capillaries: 1-.Continuous Capillaries: Continuous capillaries are the most common type of capillaries in the body. They have a continuous endothelial lining with small gaps called intercellular clefts between the cells. These capillaries allow for the exchange of small molecules such as oxygen, carbon dioxide, and nutrients. 2-Fenestrated Capillaries : Fenestrated capillaries have pores or openings (fenestrations) within their endothelial lining. These pores allow for increased permeability, facilitating the exchange of larger molecules and fluids. Fenestrated capillaries are found in organs that require rapid exchange of substances, such as the kidneys, endocrine glands, and intestines. 3-Sinusoidal Capillaries: Sinusoidal capillaries, also known as discontinuous capillaries, have a discontinuous endothelial lining with large gaps between the cells. These capillaries have a wider diameter and a more irregular shape compared to other types. Sinusoidal capillaries are found in organs such as the liver, spleen, and bone marrow, where they allow for the passage of larger cells and molecules, including blood cells and proteins. 3-.Blood: Blood is a fluid connective tissue that circulates throughout the body. It consists of plasma, red blood cells, white blood cells, and platelets. Plasma is a yellowish fluid that carries nutrients, hormones, wasteproducts, and other substances. Red blood cells transport oxygen to the body's tissues and remove carbon dioxide. White blood cells are involved in immune responses, defending the body against infections. Platelets help in blood clotting to prevent excessive bleeding. The circulatory system plays a crucial role in maintaining homeostasis in the body by delivering oxygen and nutrients to cells, removing waste products, regulating body temperature, and distributing hormones. It also helps in immune responses and blood clotting to prevent infections and excessive bleeding. Thanks  Blood Blood is a vital fluid that circulates through the bodies of many animals, including humans. It plays a crucial role in transporting oxygen, nutrients, hormones, and waste products throughout the body, allowing cells and organs to function properly. Composition of Blood: Blood is composed of several components, including red blood cells, white blood cells, platelets, and plasma. 1-.Red Blood Cells (RBCs): Also known aserythrocytes, red blood cells are the most abundant cells in the blood. Their primary function is to carry oxygen from the lungs to the body's tissues and remove carbon dioxide, a waste product of cellular metabolis,.Normal Count about 4.5 -5.5 X106 /ul 4. White Blood Cells (WBCs): White blood cells, or leukocytes, are an essential part of the immune system. Norma count about (4—10 ) X103 c/ul They help the body fight off infections and diseases by identifying and destroying pathogens, such as bacteria, viruses, and fungi. There are different types of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific functions. 3-.Platelets: Platelets, or thrombocytes, are small cell fragments involved in blood clotting. When a blood vessel is damaged, platelets accumulate at the site to form a plug and stop bleeding and normal count in human body about (150-350X103/ul ). They also release substances that help promote clotting and initiate the healing process. 4-.Plasma: Plasma is a yellowish fluid that makes up the majority of blood volume. It is composed of water, proteins, hormones, electrolytes, gases, and other substances. Plasma serves as a medium for transporting blood cells, nutrients, hormones, and waste products throughout the body.  Functions of Blood: Blood performs several vital functions in the body, including: 1-.Transportation: Blood carries oxygen from the lungs to the body's tissues and removes carbon dioxide and other waste products for elimination. It also transports nutrients, hormones, and other essential substances to various organs and tissues. 2-.Regulation: Blood helps regulate body temperature, pH balance, and electrolyte levels. It also plays a role in maintaining fluid balance within the body. 5. Protection: The immune system components present in blood, such as white blood cells and antibodies, help defend the body against infections and diseases. Blood clotting mechanisms protect against excessive bleeding and facilitate wound healing. 4-.-Homeostasis: Blood helps maintain overall stability and balance in the body, ensuring that various systems and organs function properly.  Hematopoiesis Hematopoiesis is the process of blood cell formation that occurs within the bone marrow. It involves the production of various types of blood cells, including red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). The process of hematopoiesis begins with pluripotent stem cells , which have the ability to differentiate into multiple cell types. These stem cells differentiate into two main lineages: the lymphoid lineage and the myeloid lineage. The lymphoid lineage gives rise to lymphocytes, which are a type of white blood cell involved in the immune response. Lymphocytes include B cells, T cells, and natural killer (NK) cells. They are primarily produced in the lymphoid organs, such as the bone marrow and thymus. The myeloid lineage gives rise to red blood cells, platelets, and most types of white blood cells. Myeloid stem cells differentiate into progenitor cells that are committed to specific cell lineages. Erythrocyte progenitor cells develop into red blood cells, while megakaryocyte progenitor cells give rise to platelets. Other progenitor cells in the myeloid lineage differentiate into various types of white blood cells, such as neutrophils, eosinophils, basophils, monocytes, and macrophages. The process of hematopoiesis is regulated by various growth factors and cytokines, which are signaling molecules that promote or inhibit the proliferation and differentiation of blood cells. For example, erythropoietin (EPO) stimulates the production of red blood cells, while granulocyte colony-stimulating factor (G-CSF) promotes the production of neutrophils.  1-.Bone Marrow: Hematopoiesis primarily occurs in the bone marrow, which is a soft, spongy tissue found inside the bones. Red bone marrow, also known as myeloid tissue, is the active site of hematopoiesis in adults. Yellow bone marrow, found in the central cavities of long bones, consists mainly of fat cells and has a reduced capacity for hematopoiesis..2-Hematopoietic Stem Cells (HSCs): HSCs are the multipotent cells responsible for generating all blood cell types. They can self-renew and differentiate into more specialized progenitor cells. HSCs reside in the bone marrow and undergo a process called asymmetric division, producing one daughter cell that remains a stem cell while the other differentiates into a progenitor cell. 3-Progenitor Cells: Progenitor cells are more committed and specialized than HSCs. They have a limited ability to self-renew and give rise to specific lineages of blood cells. Progenitor cells are often identified based on the presence of specific cell surface markers or by their functional characteristics. 4-Erythropoiesis: Erythropoiesis is the process of red blood cell (RBC) production. It is regulated by the hormone erythropoietin (EPO), which is primarily produced by the kidneys in response to low oxygen levels. EPO stimulates the differentiation and maturation of erythrocyte progenitor cells into mature red blood cells. The mature RBCs contain the oxygen- carrying molecule called hemoglobin and play a crucial role in oxygen transportation throughout the body. 5 -Leucopoiesis: Leukopoiesis is the process of white blood cell (WBC) production. Different types of white blood cells, including neutrophils, eosinophils, basophils, monocytes, and lymphocytes, are produced through leukopoiesis. The production of these cells is regulated by various growth factors and cytokines, such as granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM- CSF), and interleukins. 6-Thrombopoiesis : Thrombopoiesis is the process of platelet production. It involves the differentiation of megakaryocyte progenitor cells into megakaryocytes, which are large, polyploid cells present in the bone marrow. Megakaryocytes release platelets into the bloodstream by extending long cytoplasmic projections called proplatelets, which fragment into individual platelets. 7-.Regulation of Hematopoiesis: Hematopoiesis is tightly regulated by various factors. Growth factors and cytokines play a crucial role in stimulating or inhibiting the proliferation and differentiation of blood cells. Additionally, interactions with the bone marrow microenvironment, including stromal cells, extracellular matrix components, and signaling molecules, also influence hematopoiesis. 8-.Extra medullary Hematopoiesis : In certain circumstances, such as severe anemia or certain diseases, hematopoiesis can occur outside the bone marrow. This phenomenon is known as extramedullary hematopoiesis and typically occurs in organs such as the spleen, liver, or lymph nodes.