Blood Vessels and Circulation PDF

From the capillaries, blood flows into veins CAPILLARIES -Blood flows from arterioles into capillaries -Capillaries branch to form networks -blood flow through capillary networks is regulated by smooth muscle cells called precapillary sphincters -These Precapillary sphincters are located at the orig...

From the capillaries, blood flows into veins CAPILLARIES -Blood flows from arterioles into capillaries -Capillaries branch to form networks -blood flow through capillary networks is regulated by smooth muscle cells called precapillary sphincters -These Precapillary sphincters are located at the original of the branches of the capillaries and by contracting and relaxing regulate the amount of blood flow through the various sections of the network -Capillary wall’s consist of endothelium, which is a layer of simple squamous epithelium surrounded by delicate loose connective tissue -The thin walls of capillary facilitate diffusion between the capillaries and surrounding cells -Each capillaries is 0.5 millimeter (mm) long. Capillaries branch without changing their diameter which is approximately the same as the diameter of a red blood cell -Red blood cell’s flow through most capillaries in a single file and are frequently folded as they pass through the smaller diameter capillaries. As blood flows through capillaries, blood gives up O2 and nutrients to the tissues spaces and takes up CO2 And other by products of metabolism -capillary networks are more numerous and more expensive in the lungs And highly metabolically shoes issues such as the liver kidneys skeletal muscle in cardiac muscle than in other issue types. Veins Carry blood toward the heart, usually, the blood is deoxygenated (oxygen-poor). Compared to arteries, the walls of veins are thinner and contain less elastic tissue and fewer smooth muscle cells. Starting at capillaries and proceeding toward the heart, small-diameter veins come together to form larger-diameter veins, which are fewer in number. Veins increase in diameter and decrease in number as they progress toward the heart, and their walls increase in thickness. Veins may be classified as venules, small veins, medium-sized veins, or large veins. Veins Blood flows from capillaries into venules and from venules into small veins. Venules have a diameter slightly larger than that of capillaries and are composed of endothelium resting on a delicate connective tissue layer. The structure of venules, except for their diameter, is very similar to that of capillaries. Small veins are slightly larger in diameter than venules. All three tunics are present in small veins.  The tunica media contains a continuous layer of smooth muscle cells, and the connective tissue of the tunica adventitia surrounds the tunica media. Blood Flow, Pressure, and Resistance The circulatory system is the continuous system of tubes that pumps blood to tissues and organs throughout the body Key Points The pulmonary croulatsry system crculates deoxygenated blood from the heart to the lungs via the pulmonary artery and returns it to the heart via the pulmonary vein. The systemic circulatory system circulates oxygenated blood from the heart around the body into the tissues before it is retumed to the heart. The arteries divide ints thin vessels called arterioles, which in tum divide into smaller capillaries that form a network between the cells of the body. The capillaries then join up again to make veins that return the blood to the heart. The flow of blood along arteries, arterioles and capillaries is not constant but can be controlled depending upon the body's requirements. Vascular resistance generated by the blood vessels must be overcome by blood pressure generated in the heart to allow blood to flow through the orculatory system Key Terms vasodilation: The opening of a blood vessel flow:. The movement of blood around the body closely controlled by alterations in resistance and pressure. vasoconstriction: The closing or tightening of a blood vessel. resistance:The resistance which must be overcome by pressure to maintain blood flow throughout the body. pressure: The force which overcomes resistance to maintain blood flow throughout the body ❖ The circulatory system is the continuous system of tubes through which the blood is pumped around the body. It supplies the tissues with their nutritional requirements and removes waste products ❖ The pulmonary circulatory system circulates deoxygenated blood from the heart to the lungs via the pulmonary artery and returns it to the heart via the pulmonary vein  ❖ The systemic circulatory system circulates oxygenated blood from the heart around the body into the tissues before returning deoxygenated blood to the heart. Resistance, Pressure and Flow Three key factors influence blood circulation Resistance Resistance to flow must be overcome to push blood through the circular system. If resistance increases , either pressure must increase to maintain flow or flow rate must reduce to maintain pressure Numerous factors can after resistance but the three most important are vessel length, vessel radius and blood viscosity. With increasing length, increasing viscosity and decreasing radius resistance is increased The anteserious and capillary networks are the main regons of the circulatory system that generate resistance due the small caliber of their lumen. The resistance offered by peripheral circulation is known as systematic vascular resistance (SVR) while the resistance offered by the vasculature of the lungs is known as pulmonary vascular resistance (PVR) Blood Pressure Blood pressure is the pressure that blood exerts on the wall of the blood vessels. The pressure originates in the contraction of the heart, which forces blood out of the heart and into the blood vessels. If flow is impaired through increased resistance then blood pressure must increase, so blood pressure is often used as a test for circulatory health. Blood pressure can be modulated through altering cardiac activity, vasoconstriction, or vasodilation. Blood Flow Flow is the movement of the blood around the circulatory system. A relatively constant flow is required by the body's tissues, so pressure and resistance are altered to maintain this consistency A too-high flow can damage blood vessels and tissue, while flow that's too low means tissues served by the blood vessel may not receive sufficient oxygen to function. Disease that can affect the circulatory system includes: 1. Atherosclerosis hardening of the arteries  it is typically caused by a diet in high fat, which leaves fatty deposits on the lining of the blood vessels. These fatty deposits stick together and make the arteries hard and less flexible. Atherosclerosis lead to high blood pressure, which can damage the heart and kidneys and even the 2. Heart Attack Myocardial infarction (MI) is a technical term for heart attack A heart attack can occur when the blood supply is cut off from the heart, often by blood clot Some heart attack are minor but other can be life-threatening 3. Mitra valve prolapse The mitral valve bulges out or prolapse because it does not close evenly Mitral valve pumps freshly oxygenated blood out of the heart to rest of the body 4. Mitral Valve Regurgitation Mitral valve regurgitation happens when the mitral valve does not close all the way and cause leak, allowing some oxygenated blood to flow backwards 5.Mitral stenosis Mitral valve is abnormally narrow which can prevent the blood from flowing smoothly or quickly through it 6. Angina pectoris Angina pectoris means "pain in the chest and occurs if the heart is not receiving enough blood. People often describe it as a crushing sensation or feeling like their chest is in a vice. People with angina pectoris may also feel breathless, tired 7. Arrhythmia and dysrhythmia Arrhythmia and dysrhythmia are often used interchangeably, and both refer to abnormal heart rates and rhythms. In general, arrhythmia means "no rhythm" and dysrhythmia means "abnormal rhythm." 8. Cardiac Ischemia The heart muscle is not getting enough oxygen to function properly.  A person with cardiac ischemia will usually experience angina-like pain and may feel as though they are having a heart attack. 9. High cholesterol Usually caused by a sedentary lifestyle and an unhealthful diet. Some people can also be genetically at risk of high cholesterol. People need cholesterol, but too much cholesterol can form a thick layer on the inside of the vessels, blocking blood flow. 10. Heart failure Heart failure means that the heart is not pumping blood around the body as efficiently as it should. It can lead to fatigue, shortness of breath, and coughing. Some people with heart failure find it difficult to do things such as walking, climbing stairs, or carrying groceries. 11. High blood pressure (hypertension) High blood pressure (hypertension) means the force or pressure of the blood flowing through the vessels is consistently too high. High blood pressure can lead to stroke, loss of vision, heart failure, heart attack, kidney disease, and reduced sexual function. 12. Stroke A stroke can happen when one of the vessels that lead to the brain either becomes blocked by a blood clot or bursts. This stops blood flow and prevents oxygen from getting to the brain. 13. Peripheral Artery Disease (PAD) Peripheral artery disease (PAD) refers to narrowing of the arteries that lead to the legs, stomach, arms, and head. This reduced blood flow can damage the cells and tissues in the limbs, organs, and brain. PAD tends to occur more often in older people. 14. Venous Thromboembolism (VTE) A blood clot that gets stuck in a vein, blocking the flow of blood. It is a serious condition that needs emergency medical attention. 15.Aortic Aneurysms Aortic aneurysms affect the main artery in the body. It means the artery wall has weakened, allowing it to widen or "balloon out." An enlarged artery could burst and become a medical emergency. Can circulatory diseases be prevented? While scientists do not know what causes all of these diseases, there are things that individuals can do to reduce the risk of developing them. ❖ Many circulatory system diseases are linked to each other. For example, high blood pressure damages the blood vessels, which can lead to other circulatory problems. ❖ The narrowing of blood vessels caused by high cholesterol increases the likelihood of a person getting a blood clot. ❖ Being overweight or obese also increases the possibility of developing circulatory diseases. However, a healthful diet and being active can reduce the risk. ❖ Regular exercise keeps the heart healthy by reducing the risk of high blood pressure, high cholesterol, and being overweight - all of which are risk factors for circulatory diseases. ❖ People who have family members with a circulatory disease are more likely to develop one themselves. This risk, however, can be reduced with a healthful lifestyle.