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CIRCULATORY SYSTEM
➢ Introduction:
- The circulatory system,also known as the cardiovascular system,is a vital network that transport blood, oxygen, nutrients and hormones throughout the body, while also removing waste products.
- It consists of heart, blood vessels (arteries,veins and capillaries) and blood.
➢ Functions:
1. Transport of oxygen and nutrients: - The circulatory system composed of heart, blood vessels (arteries, veins and capillaries), and blood, delivers oxygen and essential nutrients from the lungs and digestive system to all parts of the body. 2. Removal of waste products: - It efficiently removes waste products,such as carbon dioxide,produced by the body’s cell and transport them to the lungs for exhalation and to the kidneys for excretion. 3. Hormone Transport: - The circulatory system also plays a crucial role in transporting hormones, which are chemical messengers that regulate various bodily functions. 4. Defense against infection: - The circulatory system helps protect the body against infection by circulating immune cell and antibodies that flight off pathogens. 5. Temperature regulation: - The circulatory system helps regulate body temperature by distributing heat throughout the body and allowing for heart dissipation through the skin. 6. Tissue repair: - The substances present in the blood help repair damaged tissues. 7. Maintaining blood pressure: - The circulatory system helps to maintain blood pressure, which is the force of blood pushing against the walls of blood vessels.
➢ Components :
I. Heart II. Blood vessels III. Blood Heart o The heart is roughly cone shaped hollow muscular organs. o That is responsible for pumping blood through blood vessels by repeated rhythmic contraction. o The term cardiac means ‘related to the heart’ and comes from the Greek word, ‘Kardia’ which means ‘heart’. o The human heart is about the size of a first and has a mass of between 250 - 300 gram in female and 300-350 gram in male. o It is about 10 cm long. o Average human heart beats 72 b/min. ➢ LOCATION o It is located slightly left of middle in chest, anterior to the vertebral column and posterior to the sternum. o Situated in the thoracic cavity in the mediastinum space,just above the diaphragm. o Present at the level of thoracic vertebrae T5-T8. And present in the midline just tilted towards the left. ➢ ORGANS ASSOCIATED WITH THE HEART o Inferiorly: Central tendon of the diaphragm. o Superiorly: The great blood vessels; Aorta, Superior vena cava, Pulmonary artery and vein. o Posteriorly: Oesophagus,Trachea,Bronchus,Desending aorta. o Laterall y: The lungs o Anteriorly: The sternum , ribs and intercostal muscles.
o Upper chamber that receives deoxygenated blood from body through superior vena cava and Inferior vena cava. o Act as a reservoir for blood, allowing it to flow into the right ventricle during diastole. o Thin walled chamber compared to the ventricles. o Contains the sinoatrial node, regulate heart rhythm. o Has a smooth inner surface. o Right atrium contains pectinale muscles and SA node.. o Pectinale Muscle: These are muscular ridges within the RA’s walls. It increases the surface area for contraction. o SA node: SA node is a small group of specialized cells. And act as the heart’s natural pacemaker, regulating heart rhythm. ❖ Right Ventricle: o Lower chamber that pumps deoxygenated blood to the lungs. o Receives blood from the RA through Tricuspid Valve. o RV contract to pump blood to the lungs through the pulmonary artery through pulmonary valve. o Thicker walls than the atria, but thinner than the left ventricle. o Plays crucial role in pulmonary circulation, ensuring deoxygenated blood reaches the lung for oxygenation. o Right Ventricle contain Trabuculae Corneae and Papillary muscles. o Trabeculae Corneae: These are fibrous strings that plays a crucial role in heart’s functioning. o They connect the cups of the atrioventricular valves (Mitral and Tricuspid Valve) to the papillary muscles. o It prevents the valve from opening backward, ensuring proper blood flow. o It helps to maintain valve integrity and prevent regurgitation. o Chordae Trabeculae are made of collagen fibers o They are attached to the papillary muscles, which. Contract and relax to tighten or loosen the chordae. o Essential for proper heart function and efficient blood flow. o Damage to chordae Trabeculae can lead to valve problems such as mitral regurgitation. o Papillary Muscles: small muscles located in the ventricles of the heart. o Attached to the cups of tighten or loosen the chordae Trabeculae. o Help regulate valve opening backward, preventing regurgitation.
o Papillary muscles contract and relax in sync with the heartbeat. o They help maintain tension on the chordae Trabeculae, ensuring proper value function. ❖ Left Atrium: o Upper chamber that receives oxygenated blood from the lungs. o Blood flows into the LA through the pulmonary veins. o The LA contract to push blood into the left ventricle. o Acts as a reservoir for blood, allowing it to flow into the left ventricle during diastole. o Thin walled chamber composed to the ventricles. o Has a smooth inner surface plays a crucial role in the cardiac cycle, ensuring oxygenated blood flows properly from the lungs to the left ventricle and than to the rest of the body. o It contains pectinate muscles. ❖ Left Ventricle: o Lower chamber that pumps oxygenated blood to the body. o Receives blood from the LA through the mitral valve. o LV contracts to pump blood to the body through the Aorta through aortic valve. o Blood is then distributed to the entire body, supplying oxygen and nutrients. o Thicker walls than the RV and Atria, due to the higher pressure needed to pump blood through the body. o Plays a crucial role in systemic circulation, ensuring the oxygenated blood reaches the entire body. o It contains Trabuculae Corneae and Papillary Muscles ➢ Valves of heart: o The heart has four valves that play a crucial role in ensuring efficient blood and preventing backflow. ❖ Tricuspid Valve o Located between the right atrium and right ventricle. o Allows blood to flow from RA to RV while preventing backflow. o Has three leaflets that open and close with each heartbeat. o Supported by chordae tendineae and papillary muscles. o Opens during diastole and closes during systole o Prevents regurgitation and .maintains cardiac output. ❖ Pulmonary valve
o Contains gap junctions for rapid electrical conduction and coordinated contraction. ➢ Epicardium: The Outermost Layer o Composed of connective tissue and mesothelial cells o Covers the heart, providing protection and support o Produces pericardial fluid, which lubricates the heart and reduces friction between the heart and surrounding tissues o Continuous with the pericardium, a sac surrounding the heart ➢ Septum o The septum in the heart refers to a wall of tissue that separates different chambers. o The septum plays a crucial role in:
- Preventing mixing of oxygenated and deoxygenated blood.
- Maintaining efficient blood flow through the heart. o There are two main septa: Atrial Septum and Ventricular Septum. a) Atrial Septum: o Atrial septum is a well of tissue that separates the RA and LA. o Divides the two atria, preventing mixing of oxygenated and deoxygenated blood. o Thin wall of tissue. o Contains the fossa ovalis, a depression marking the former foramen ovale (present in fetal development) o Maintains separation of blood flow between the two atria. o Essential for efficient heart function. o Atrial Septal Defect (ASD) : A hole in the atrial septum, allowing blood to flow between the atria. b) Ventricular Septum: o The ventricular Septum is a wall of tissue that separates the RV and LV. o Divides the two ventricles, preventing mixing of oxygenated and deoxygenated blood. o Thicker than the atrial septum, due to higher ventricular pressure. o Composed of muscular and membranous parts. o Maintain separation of blood flow between the two ventricles. o Essential for efficient heart function and preventing complication.
o Ventricular Septal Defect : A hole in the ventricular septum, allowing blood to flow between the Ventricles. ➢ Blood flow through heart o Superior vena cava carries deoxygenated blood from upper part of body and Inferior vena cava carries deoxygenated blood from lower parts of body. o Right Atrium carries deoxygenated blood from superior vena cava and Inferior vena cava. o Right atrium pumps the blood towards the right ventricle through Tricuspid Valve.. o Pulmonary artery carries oxygenated blood from lungs and it goes in the left atrium. o Left ventricle carries oxygenated blood from left atrium through Mitral valve. o Through Aortic valve transport blood to the aorta. o Aorta divided into three parts and these are transports blood to all body parts.
o The three main types of blood vessels are:
- Arteries
- Veins
- Capillaries Arteries
- Arteries are blood vessels that carry oxygenated blood away from the heart to the rest of the body. They play a vital role in maintaining cardiovascular health and ensuring that tissues and organs receive adequate oxygen and nutrients.
- Arteries are characterized by:
- Thick walls that can withstand high blood pressure
- Muscular and elastic properties that help regulate blood flow and pressure
- Arteries are essential for delivering oxygen and nutrients to tissues and organs, and their dysfunction can lead to various cardiovascular diseases. ➢ Structure of Arteries: o Arteries have a unique structure that enables them to withstand high pressure and maintain blood flow. The three layers of an artery are: ❖ Tunica Intima: o Innermost layer o Lined with endothelial cells o Provides a smooth surface for blood flow ❖ Tunica Media: o Middle layer o Composed of smooth muscle cells and elastic fibers o Allows arteries to constrict and dilate ❖ Tunica Externa: o Outermost layer o Made of connective tissue o Provides structural support ➢ Functions of Arteries: o Arteries play a vital role in the circulatory system, and their functions include:
✓ Carrying Oxygenated Blood: Arteries transport oxygenated blood away from the heart to the body’s tissues and organs. ✓ Maintaining Blood Pressure: Arteries help regulate blood pressure through constriction and dilation. ✓ Regulating Blood Flow: Arteries control blood flow to specific areas of the body through vasoconstriction (narrowing) and vasodilation (widening). ✓ Delivering Nutrients and Oxygen: Arteries ensure that tissues and organs receive adequate oxygen and nutrients. ➢ Types of Arteries: o There are three main types of arteries: ❖ Elastic Arteries: o Large arteries (e.g., aorta and its major branches) o Stretch during systole and recoil during diastole o Help maintain blood pressure ❖ Muscular Arteries: o Medium-sized arteries o Distribute blood to specific organs and tissues o Regulate blood flow through vasoconstriction and vasodilation ❖ Arterioles: o Small arteries o Control blood flow to capillaries o Regulate blood pressure and flow through vasoconstriction and vasodilation ❖ Importance of Arteries: o Arteries play a vital role in maintaining cardiovascular health and overall well-being. Their importance includes: ✓ Delivering Oxygen and Nutrients: Arteries ensure that tissues and organs receive adequate oxygen and nutrients. ✓ Maintaining Blood Pressure: Arteries help regulate blood pressure, which is essential for maintaining cardiovascular health.
❖ Veins have a unique structure that enables them to carry deoxygenated blood back to the heart. The key features of vein structure include: ❖ Tunica Intima: Innermost layer, lined with endothelial cells. ❖ Tunica Media: Middle layer, composed of smooth muscle and elastic fibers (thinner than in arteries). ❖ Tunica Externa: Outermost layer, made of connective tissue. ❖ Valves: Veins contain one-way valves that prevent backflow and ensure blood flows towards the heart. o This structure allows veins to:
- Carry deoxygenated blood back to the heart.
- Regulate blood flow and pressure.
- Accommodate varying amounts of blood ➢ Functions of Veins: o Veins play a vital role in the circulatory system, and their functions include: ❖ Returning Blood to the Heart: Veins carry deoxygenated blood back to the heart, where it can be re-oxygenated. ❖ Regulating Blood Flow: Veins help regulate blood flow and pressure by dilating or constricting. ❖ Preventing Backflow: Veins contain one-way valves that prevent backflow and ensure blood flows towards the heart. ❖ Acting as Blood Reservoirs: Veins can store blood and release it as needed, helping to maintain blood pressure and flow. ➢ Importance of Veins: o Veins play a vital role in maintaining cardiovascular health and overall well-being. Their importance includes: ❖ Returning Blood to the Heart: Veins ensure that deoxygenated blood is returned to the heart for re-oxygenation. ❖ Maintaining Blood Pressure: Veins help regulate blood pressure by storing and releasing blood as needed.
❖ Supporting Circulation: Veins work with arteries and capillaries to maintain blood flow and circulation. ❖ Preventing Blood Pooling: Veins help prevent blood from pooling in extremities, which can lead to swelling and other complications. ➢ Types of Veins:* o There are several types of veins in the body, including: ❖ Superficial Veins: Located close to the skin’s surface, these veins are often visible and can be prone to varicose veins. ❖ Deep Veins: Located within muscle compartments, these veins are often accompanied by arteries and are more prone to deep vein thrombosis (DVT). ❖ Perforating Veins: These veins connect superficial veins to deep veins and help regulate blood flow. ❖ Pulmonary Veins: These veins carry oxygenated blood from the lungs to the heart. Capillaries: o Capillaries are tiny, thin-walled blood vessels that play a crucial role in the circulatory system. They allow for the exchange of:
- Oxygen and nutrients.
- Waste products.
- Carbon dioxide o Capillaries are found in tissues and organs throughout the body and are essential for maintaining proper cellular function and overall health. ➢ Importance of Capillaries:* o Capillaries play a vital role in maintaining overall health and proper cellular function. Their importance includes: ❖ Exchange of Oxygen and Nutrients: Capillaries allow oxygen and nutrients to diffuse into tissues and cells.
Blood
o Blood is a vital fluid that circulates through the body’s cardiovascular system, supplying oxygen and nutrients to tissues and organs and removing waste products. It’s composed of:
- Plasma: Liquid portion that carries cells and proteins
- Red Blood Cells (RBCs): Carry oxygen throughout the body
- White Blood Cells (WBCs): Play a crucial role in immune function
- Platelets: Essential for blood clotting ➢ Composition of Blood: Blood is composed of:
- Plasma (55%): Liquid portion that carries cells, proteins, and nutrients.
- Formed Elements (45%): ✓ Red Blood Cells (RBCs): Carry oxygen throughout the body. ✓ White Blood Cells (WBCs): Play a crucial role in immune function. ✓ Platelets: Essential for blood clotting. ❖ Plasma:
o Plasma is the liquid portion of blood, making up approximately 55% of its total composition. It’s a clear, straw-colored liquid that carries: ✓ Water: Maintains blood’s fluidity and transport functions. ✓ Proteins: Such as albumin, globulins, and fibrinogen, which help regulate blood clotting, immune response, and blood volume. ✓ Nutrients: Glucose, amino acids, and lipids are transported to tissues and organs. ✓ Hormones: Chemical messengers that regulate various bodily functions. ✓ Waste Products: Urea, creatinine, and other waste products are transported to organs like the kidneys for removal. ✓ Electrolytes: Ions such as sodium, potassium, and calcium that help regulate various bodily functions. Plasma plays a vital role in maintaining blood’s transport functions, regulating blood pressure, and supporting immune response. ❖ Formed Elements: The formed elements of blood are the cellular components that perform specific functions. They include: ✓ Red Blood Cells (RBCs): Red Blood Cells, also known as erythrocytes, are specialized cells that play a crucial role in delivering oxygen to tissues and organs throughout the body. They contain hemoglobin, which binds to oxygen, allowing RBCs to transport it from the lungs to the body’s cells. RBCs are essential for maintaining tissue oxygenation and overall health. ❖ Functions of Red Blood Cells (RBCs): RBCs perform several critical functions: ✓ Oxygen Transport: RBCs carry oxygen from lungs to tissues and organs. ✓ Carbon Dioxide Removal: RBCs transport carbon dioxide from tissues to lungs for exhalation. ✓ Maintaining Acid-Base Balance: RBCs help regulate pH levels by buffering excess hydrogen ions.
The cytoskeleton is composed of three main components:
1. Microtubules: Microtubules are dynamic structures composed of tubulin proteins. They: - Provide structural support: Help maintain cell shape and organization. - Form spindle fibers: Play a crucial role in cell division. - Facilitate intracellular transport: Help move vesicles, organelles, and other cellular components. - Form cilia and flagella: Enable cell movement and sensing. Microtubules are essential for various cellular processes, including cell division, transport, and movement. 2. Microfilaments: Microfilaments, also known as actin filaments, are composed of actin proteins. They: - Provide structural support: Help maintain cell shape and integrity. - Enable cell movement: Play a crucial role in muscle contraction, cell migration, and cytokinesis. - Regulate cell shape: Help control changes in cell shape and morphology. Microfilaments are essential for various cellular processes, including muscle contraction, cell migration, and cell division. 3. Intermediate filaments: Intermediate filaments are a type of cytoskeletal component that: - Provide mechanical support: Help maintain cell shape and resist physical stress. - Anchor organelles: Help anchor organelles and other cellular structures. - Maintain tissue integrity: Play a crucial role in maintaining tissue structure and function. Intermediate filaments are composed of various proteins, such as keratins, vimentin, and lamin, and are specific to different cell types. They provide essential support and stability to cells and tissues. ❖ White Blood Cells (WBCs):
White Blood Cells, also known as leukocytes, are a vital part of the immune system. They help protect the body against infections, diseases, and foreign invaders. WBCs are produced in the bone marrow and circulate in the blood and lymphatic system. o Their main functions include:
- Phagocytosis: Engulfing and destroying pathogens.
- Antibody production: Producing antibodies to fight infections.
- Cell-mediated immunity: Directly attacking infected cells. WBCs play a crucial role in maintaining the body’s defense against infections and diseases. ➢ Functions of WBC : ❖ Neutrophils: o Neutrophils are the most abundant type of white blood cell in the human body. They play a crucial role in the innate immune response, providing rapid defense against infections, particularly bacterial and fungal infections. Neutrophils are highly specialized cells that are capable of:
- Engulfing and destroying pathogens through phagocytosis
- Releasing granules that contain enzymes and antimicrobial proteins
- Responding quickly to sites of infection or inflammation o Neutrophils are a vital part of the body’s defense mechanism, helping to protect against infections and promote healing. ❖ Lymphocytes: o Lymphocytes are a type of white blood cell that plays a central role in the adaptive immune response. They help the body remember and recognize specific pathogens, allowing for a more targeted and effective response. o There are two main types of lymphocytes:
- B cells: Produce antibodies to fight infections.
- T cells: Directly attack infected cells or produce chemical signals to activate other immune cells. o Lymphocytes are essential for providing long-term immunity and protecting against infections and diseases. ❖ Monocytes: o Monocytes are a type of white blood cell that:
