Human Biology Lec. 4 Blood and CVS 1 PDF

Human biology (Structure and Function of the Human Body) The Circulatory System Nashaat Nabil, MBBCH, MSc, MD Assoc. Prof. of Preventive medicine, Clinical Nutrition and Epidemiology Head of Medical Biotechnology department  ‫رؤية الكلية‬ ‫أن تكون لكية معمتدة أاكدميي ًا ورائدة...

Human biology (Structure and Function of the Human Body) The Circulatory System Nashaat Nabil, MBBCH, MSc, MD Assoc. Prof. of Preventive medicine, Clinical Nutrition and Epidemiology Head of Medical Biotechnology department  ‫رؤية الكلية‬ ‫أن تكون لكية معمتدة أاكدميي ًا ورائدة ىف جماالت التكنولوجيا احليوية‬ ‫عىل املس توى احملىل وا إالقلميى وادلوىل‬  ‫رساةل اللكية‬ ‫تلزتم لكية التكنولوجيا احليوية – جامعة مرص للعلوم والتكنولوجيا بتخرجي أخصايئ‬ ‫تكنولوجيا حيوية طبق ًا للمعايري الاكدميية املعمتدة يلىب احتياجات سوق العمل احملىل‬ ‫وا إالقلميى ىف القطاعات الطبية والصيدالنية والزراعية والبيئية وإاجراء حبوث علمية‬ ‫مبتكرة وتقدمي خدمات جممتعية واستشارات علمية ىف إاطار قمي إارتقائية‬  By the end of this lecture, you should be able to know (ILOs): – Blood composition and functions – Anatomy of the heart – Blood supply to the heart muscle – Conduction system of the heart – Blood vessels – CVS disorders Blood and Blood Components  The Juice of Life A mixture of cellular elements (erythrocytes, leukocytes, and platelets), fluid (plasma), ions, proteins, nutrients, wastes, gases, …. Circulates in a closed system of vessels (intravascular compartment) Blood volume in an average human is ~ 5 liters. Blood cells have short life-spans, and are replaced continuously through hematopoiesis  Why we need Blood Transports oxygen and nutrients to all cells of the body & CO2 and waste products to specific organs for elimination Carries ions, hormones, proteins and other signaling molecules, to their final destinations Helps regulate body temperature Maintains the acid/base & osmotic balance of the body fluids Provides optimum hydration for the extravascular compartments (interstitial and intracellular)  The Blood Trail Blood forms in the bone marrow, circulates in blood vessels RBCs carry oxygen Platelets stop bleeding WBCs protect the body The heart pumps the circulation Blood vessels control what stays in the circulation and what leaks out into different tissues Blood components are continuously recycled  Cellular Components of Blood RBCs = (4.8-5.4 million/µL of blood) WBCs = (4,000 - 11,000/µL of blood) Platelets = (150,000-400,000/ µL of blood)  Life span Red blood cells (RBCs), also referred to as red blood corpuscles, haematids, erythroid cells or erythrocytes =90-120 days. White blood cells (Leukocytes)=13-20 days (according to type). Platelets (Thrombocytes)=8-12 days  The Red Cell Biconcave disc (20-30% more surface area than a sphere) with no nucleus or organelles. Cytoplasm filled with hemoglobin (iron- containing protein; capable of carrying oxygen) Average 7 µm in diameter (the smallest capillary is 3-4 µm). 2-4 million new RBCs are produced by the bone marrow per second Recycled by the macrophages in the RES (liver, spleen, and lymph nodes) Which of the following statements about RBCs is wrong? A. They lack nuclei B. They form biconcave discs C. They are larger than the smallest capillaries D. They have abundant mitochondria to generate ATP for oxygen transport  White blood cells White blood cell, also called leukocyte, a colorless cell which circulates in the blood and is involved in counteracting foreign substances and disease. There are several types, including granulocytes, and agranulocytes  Leukocytes Granulocytes Basophils Neutrophils Eosinophils Agranulocytes Monocytes Lymphocytes  Platelets (Thrombocytes) A small colorless disc-shaped cell fragment (2-4 μm in diameter) without a nucleus, found in large numbers in blood and involved in clotting. Primary function is to rapidly release the content of their granules upon contact with collagen (or other materials outside of the endothelium) to begin the process of clot formation  Mechanism of Blood Clotting i. Vascular Spasm: The smooth muscle in blood vessel walls contracts immediately the blood vessel is broken. This response reduces blood loss for some time, while the other hemostatic mechanisms become active. ii. Platelet Plug Formation: When platelets encounter a damaged blood vessel, they form a “platelet plug” to help to close the gap in the broken blood vessel. (The key stages of this process are called platelet adhesion and platelet aggregation)  Mechanism of Blood Clotting iii. Coagulation: Blood normally remains in its liquid state while it is within the blood vessels but when it leaves them the blood may thicken and form a gel (coagulation). Blood clotting (“blood coagulation”) is the process by which (liquid) blood is transformed into a solid state This blood clotting is a complex process involving many clotting factors (calcium ions, enzymes, platelets, damaged tissues) activating each other  Hematopoiesis The earliest hematopoiesis in the fetus occurs in the yolk sac During the second trimester, it occurs mainly in the liver, and spleen By the end of the second trimester, it also involves the bone marrow in the medullary cavity of long bones In adults, it occurs mainly in bones of axial skeleton  The Heart A bag made of strong sheets of muscle enforced with fibrous tissue Receives blood coming from different regions of the body through the venous system and pushes (pumps) it into the arterial system Located in the mediastinum between the two lungs ”Powered” by its own internal pulse generator  Four chambers (cavities within the heart) → two for receiving blood from the venous system (atria) and two for sending it into the arterial system (ventricles) Each chamber fills with blood when the muscle in the wall RELAXES (diastole), then it pushes the blood when the muscle CONTRACTS (systole) Ventricles need more force (thicker muscles) Atria must push the blood to the ventricles FIRST, then ventricles send that blood to the rest of the body Blood MUST MOVE IN ONE DIRECTION Layers of the cardiac wall Pericardium Myocardium Endocardium  Blood Supply to the Heart The right and left coronary arteries. The coronary arteries are the aorta’s first branches. Blood flows into them during ventricular DIASTOLE  Occlusion (total obstruction) or stenosis (narrowing) of a coronary artery or one of their branches → Angina pectoris Myocardial infarction (death and scarring of part of the myocardium) is a common cause of death during middle and late adulthood. A cardiac catheter is a procedure where the coronary vessels are injected with a dye to visualize any obstruction. Can also be used to treat in some cases A plastic tube (stent) can be used to overcome a small obstruction. Sometimes, however, a bypass surgery is needed, in which a vein graft is used to “go around” the obstructed segment  Conduction (Electric) System of the Heart Cardiac muscle fibers can contract rhythmically on their own Contractions must be coordinated for the heart to pump effectively. This is why it has its own pacemaker and conduction system The rate and rhythm of cardiac muscle contraction is adjusted by autonomic nerve signals. Cardiac muscle fibers in each region of the heart are electrically linked together.  Conduction (Electric) System of the Heart 1.Sinoatrial node, sometimes called the SA node or the pacemaker 2.Atrioventricular node, or AV node 3.AV bundle, or bundle of His 4.Purkinje fibers  Heart Sounds Two distinct sounds can be heard. They are rhythmical and repetitive sounds that are often described as lub dup. The first, or lub, sound is caused by the vibration and abrupt closure of the AV valves as the ventricles contract. Closure of the AV valves prevents blood from rushing back up into the atria during contraction of the ventricles. This first sound is of longer duration and lower pitch than the second. The second heart sound, dup is caused by the closing of both the aortic and pulmonary valves when the ventricles undergo diastole (relax).  Blood Vessels BLOOD PRESSURE Is the pressure or “push” of blood as it flows through the cardiovascular system. It exists in all blood vessels, highest in the arteries and lowest in the veins. For example, if blood pressure in large arteries were to decrease to a point at which it became equal to the pressure their smallest branches (arterioles). The result would be that there would be no force available to move blood out of arteries into arterioles. Circulation would stop. That is why when arterial blood pressure falls rapidly (hypotension), for example during severe bleeding, emergency measures must be started quickly to try to reverse this fatal trend. High blood pressure, or hypertension (HTN), is also bad for several reasons. For example, it may cause the rupture of one or more blood vessels (for example, in the brain, as happens in a stroke). Factors Controlling Blood Pressure The volume of blood in the arteries The diameter of the arterioles Blood Viscosity  Exercises What would diuretics do to the mean blood pressure? What would vasoconstrictor (drugs that make arterioles narrower) drugs do to the mean blood pressure PULSE What you feel when you take a pulse is an artery expanding and then recoiling alternately. It can provide information about the rate, strength, and rhythm of the heartbeat. The nine major “pulse points” are named after the arteries over which they are felt. Locate each pulse point on your own body.  Circulatory system disorders Atherosclerosis Atherosclerosis is the buildup of plaque in the arteries. Over time, the plaque narrows arteries and makes it harder for blood to flow through. The plaque is also dangerous because it can rupture and trigger a blood clot. Atherosclerosis raises the risk of other diseases, including: - Carotid artery stenosis: Plaque buildup in the arteries in the neck that supply blood to brain. - Coronary artery disease (CAD): Plaque buildup in the arteries that supply blood to heart. CAD is the most common cause of a heart attack. - Peripheral artery disease. Plaque buildup in the arteries that run through the arms and legs.  Arrhythmias An arrhythmia is an irregular or abnormal heartbeat. Some begin in the upper chambers of heart (atria). These are called supraventricular arrhythmias. Atrial fibrillation is the most common type. Others begin in the lower chambers of heart (ventricles). These are called ventricular arrhythmias. One type, ventricular fibrillation, is a life-threatening medical emergency because it leads to sudden death. Arrhythmias prevent heart from contracting and relaxing normally. As a result, the heart can’t pump blood as well as it should.  Aneurysms Aneurysms are weak spots in the walls of arteries that can expand like a balloon. As they continue to get bigger, they’re at risk for rupture (breaking open) or causing blood clots. Aneurysms can occur in any artery. Most often, they occur in aorta, which is the largest artery in body. These are known as aortic aneurysms, and there are two main types: Thoracic aortic aneurysms, which develop in the part of aorta that’s in chest. Abdominal aortic aneurysms (AAA), which develop in the part of the aorta that’s in belly. These are more common than thoracic aortic aneurysms.  Blood pressure conditions Blood pressure is a number that shows how forcefully blood flows through the blood vessels Blood pressure conditions include: - Hypertension: High blood pressure throughout the arteries in the body. This is what people usually mean when they say, “high blood pressure.” Hypertension is known as a silent killer because it often has no symptoms, but it can, over time, lead to many health problems. - Hypotension: Low blood pressure throughout the body.  Cardiomyopathy Cardiomyopathy is a group of conditions that affect heart muscle, leading to weakened heart squeeze. These conditions harm heart’s ability to pump blood. Specific types of cardiomyopathy include: Dilated cardiomyopathy: The heart chambers get bigger. Hypertrophic cardiomyopathy: The heart muscle gets thicker (stiff). Peripartum cardiomyopathy: The heart weakens late in pregnancy or soon after delivery with no definite cause.  Congenital heart disease ❑ Congenital heart disease refers to heart problems babies are born with. Congenital heart disease is sometimes heritable. Other times, it occurs in people with no family history. ❑ Types of congenital heart disease include: Atrial septal defect and ventricular septal defect: A “hole in the heart,” located between the left and right sides of baby’s heart. Bicuspid aortic valve: An aortic valve with two flaps instead of three. Tricuspid atresia: Missing tricuspid valve. Pulmonary atresia: Missing or blocked pulmonary valve.  Congenital heart disease (cont.) Coarctation of the aorta: Narrowing in one part of baby’s aorta. Dextro-Transposition of the great arteries: Pulmonary artery and aorta are switched. Hypoplastic left heart syndrome: An underdeveloped left side of baby’s heart. Patent ductus arteriosus (PDA): An opening between baby’s aorta and the pulmonary artery that should’ve closed at birth. Tetralogy of Fallot: A combination of four defects that prevent baby from getting enough oxygen-rich blood. Truncus arteriosus: Only one artery carries blood out of baby’s heart, instead of two (aorta and pulmonary artery).  Heart failure Heart failure happens when the heart can’t pump blood as well as it should. So, organs can’t get enough oxygen. Heart failure has many causes and is associated with many other medical conditions. The later stages are called “congestive heart failure.” This involves fluid buildup (congestion) in different parts of your body.  Heart valve disease Heart valve disease can affect any of the four heart valves. These are the doors that separate different parts of heart and manage blood flow. A diseased valve strains the heart. Over time, this can lead to complications like heart failure or sudden cardiac death. The most common valve diseases among adults are: Mitral valve regurgitation: The mitral valve is leaky, causing some blood to flow backward. Aortic valve stenosis: The aortic valve is too narrow, limiting how much blood can flow through. Aortic valve regurgitation: The aortic valve is leaky.  High cholesterol Fats do important work in bodies. But too many fats in blood can be dangerous. This condition is known as high cholesterol (hyperlipidemia). High cholesterol can raise the risk of many other medical conditions. Familial hypercholesterolemia is high cholesterol that’s passed down within biological families. People with this condition have very high LDL (bad cholesterol) levels. This raises their risk of coronary artery disease and heart attacks.  Stroke A stroke is a life-threatening emergency that needs immediate medical attention. It happens when blood flow to the brain gets interrupted. There are several types of stroke: Ischemic stroke: A blood clot blocks an artery leading to the brain. Hemorrhagic stroke: There’s bleeding in the brain (sometimes, from a ruptured blood vessel or head injury). Transient ischemic attack (TIA): A blood clot temporarily blocks blood flow to brain, causing a “mini stroke.” A TIA is usually a warning sign before an ischemic stroke.  Vasculitis Vasculitis is an inflammation of the blood vessels caused by an overactive immune system. Vasculitis can affect veins, arteries or capillaries. This inflammation can narrow or block blood vessel. It can also weaken blood vessel and cause an aneurysm.  Venous disease Venous diseases are a group of conditions that affect the veins. Veins carry oxygen-poor blood back to heart. Diseases that affect veins can slow down the blood flow or make blood flow in the wrong direction. Severe venous disease can completely block blood flow. Common venous diseases include: Chronic venous insufficiency (CVI): leg veins struggle to pump blood back up to the heart. This causes blood to collect in the leg veins. Deep vein thrombosis (DVT): A blood clot forms in one of the deep veins (veins that aren’t near the surface of skin). If the clot breaks free, it can travel to the lungs and cause a life-threatening pulmonary embolism.  Angina pectoris Angina is chest pain or discomfort that happens when the heart isn’t receiving enough oxygen-rich blood. As a result, the heart may beat faster and harder to gain more blood, causing noticeable pain.