1 2 3 Anatomy and Physiology 2 Journal BSC2086 Alexandria Nicot June 17th 2014 This is my own unassisted work 1 2 3 4 The Circulatory System Blood Vessels and Circulation Chapter 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 Many types of vessels run through our body and each have a unique destination and function There are two main circuits in the body the pulmonary and systemic The right side of the heart sends oxygen poor blood to the lungs this is the pulmonary circulation The left side of the heart is characterized by delivering oxygen rich blood previously filtered out in the lungs to everywhere else in the body known as the systemic circulation It all begins with the heart Following the flow of circulation from the heart are the arteries then arterioles and metarterioles The metarterioles are the passageways that link both artery and vein together The capillaries are the network of vessels between the two where the gas exchanges occur Lastly the flow continues to the venules that feed into the larger veins ultimately leading back to the heart Together the blood vessels and the heart are what constitute the cardiovascular system The final goal of this system is to nourish all the tissues of the body with oxygen and eliminate waste products The cardiovascular system also works alongside the lymphatic system with communication to remove excess fluid and toxins Additionally to the lymphatic s blood vessels correlate with the endocrine system via hormones to regulate body water volume and influencing blood pressure by controlling vasoconstriction Our bodies could not adjust to external and internal contributing factors if it were not for blood vessels Tubes that carry blood away from the heart in a high pressure system are known as arteries As the blood pumps oxygenated blood to the largest artery in the body the aorta it receives cardiac output from the left ventricle It sends it out into three major branches the brachiocephalic left common carotid and left subclavian artery Due to the heart s strong systolic force it shoots blood into the arteries in a high pressure system Arteries have to maintain the spongy quick expansion whenever blood is shot out of the heart and recoil right after Although the thickness of arteries varies by location For instance arteries close to the heart are thicker to accommodate for the stronger input of blood than arteries farther away such as the dorsalis pedis artery The elasticity of the arteries would be the greatest by the heart and therefore called elastic arteries whereas arteries further along the vascular system is often referred to as muscular arteries A smaller subdivision of this group are the arterioles It could be portrayed as road transportation The arteries are major highways and arterioles are the main roads in a town Arterioles have the same anatomical structure as arteries in comparison of their layers but the middle and outer layers become smaller as they approach capillaries This thinning of the layer helps the diffusion of gasses between arterioles to venules by the connection of capillaries Capillaries are the tiniest and most abundant blood vessels in the body Their small structure allows for numerous connections over greater surface area between small arteries and small veins Capillaries contain very minute circular muscles known as precapillary sphincters that control the pressure and amount of blood exchange at a time The amount of fluid in the interstitial tissue is regulated by the opening and closing of these capillary sphincters Excess fluid carrying metabolic wastes are removed into the tissue to then be carried away to the nearest lymph node to be destroyed If capillary 5 2 1 2 3 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 5 The Circulatory System Blood Vessels and Circulation Chapter 20 filtration and reabsorption was not possible to be accepted into the interstitial fluid there would be a painful swelling of backed up fluid known as edema The thickness of the tunica media is what sets apart arteries from veins Both vessels have a tunica intima the inner layer wall which is comprised of endothelium This layer decreases the resistance of blood flow because it has a simple squamous layer that allows for a tight smooth wrapping The tunica externa of both arteries and veins is layered with fibrous connective tissue Its function is simple but important to support and protect However the tunica media is significantly thicker in arteries rather than veins because of more smooth muscle and elastin Arteries also have an internal and external elastic lamina that helps in the stretching The sympathetic nervous system plays an active role in controlling the diameter of the blood vessels This is important in vasoconstriction and vasodilation in fight or flight circumstances Veins of the body remove carbon dioxide waste from the tissues back to the heart and be filtered out and recycled to oxygen Veins that drain the head and upper appendages return to the superior vena cava and every extremity below the diaphragm gets drained by the inferior vena cava Veins carry more blood because their diameter is larger containing more than half of the amount of blood Valves are present in veins and not arteries because veins require valves to create pressure to pump blood back to the heart Arteries do not need valves because gravity replaces the pressure factor As blood flow is traced you can find that it divides into smaller and smaller subbranches of the arterial system In contrast the venous system is the complete opposite Small veins converge to form larger and larger veins that eventually will lead to the superior and inferior vena cava and so the process starts again Many factors influence an essential force in our bodies known as blood pressure Blood pressure is an important tool in diagnosing abnormal conditions originating from the heart or arteries These factors include cardiac output blood volume resistance to flow and hormones Two key numbers make up your blood pressure value systolic and diastolic measurements The systolic number on top is the reading when the heart beats and the arterial wall contracts The diastolic number is measured of the pressure in the arteries are refilling with blood and relaxing Neural control performed by the autonomic nervous system controls
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