Chapter 12 - Cardiovascular System: Blood Vessel and Circulation PDF

Chapter 12 – Cardiovascular System: Blood Vessel and Circulation Learning Outcomes: At the end of the lecture, the student should be able to: Describe the structure of arteries and veins, and relate their structure to function. Describe the structure of capillaries, and explain t...

Chapter 12 – Cardiovascular System: Blood Vessel and Circulation Learning Outcomes: At the end of the lecture, the student should be able to: Describe the structure of arteries and veins, and relate their structure to function. Describe the structure of capillaries, and explain the exchange processes that take place in capillaries. Describe the pathway and purpose of pulmonary circulation. Name the branches of the aorta and their distributions. Name the major systemic veins and the parts of the body they drain of blood.  Circulatory System Pulmonary vessels Systemic vessels  Pulmonary vessels Transport blood from the right ventricle, through the lungs, and back to the left atrium  Systemic vessels Transport blood through all parts of the body from the left ventricle and back to the right atrium Functions of Circulatory System Carries blood Exchanges nutrients Transports substances Helps regulate blood pressure Directs blood flow to tissues 3 Main Types of Blood Vessels: Arteries → Carry blood away from the heart Capillaries → Most of the exchange occurs Veins → Carry blood toward the heart Capillaries Capillaries Range from 7 μm to 9 μm in diameter Consists: Endothelial cells Pericapillary cells  Types of Capillaries Continuous Fenestrated Sinusoidal Depending on their diameter and permeability characteristics Continuous capillaries Approximately 7–9 μm in diameter Walls exhibit no gaps between the endothelial cells Less permeable to large molecules Location: Muscle Nervous tissue Others Fenestrated Capillaries Endothelial cells have numerous fenestrae→70–100 nm in diameter ; pores Located where capillaries are highly permeable: Intestinal villi Ciliary processes of the eyes Choroid plexuses of the CNS Glomeruli of the kidneys Sinusoidal capillaries Larger in diameter Less prominent or completely absent of basement membrane Fenestrae are larger than fenestrated capillaries Located mostly in endocrine glands Capillary Network Arteriovenous Anastomoses Allows blood to flow from arterioles to small veins without passing through capillaries. Structure of Arteries and Veins  3 Distinct Layers: Tunica intima Tunica media Tunica adventitia / tunica externa Arteries Types of Arteries Elastic Arteries Muscular Arteries Arterioles Elastic arteries Largest diameters Conducting arteries → Blood pressure is relatively high Greater amount of elastic tissue Tunica intima →relatively thick Tunica media→ consists of a meshwork of elastic fibers, smooth muscle cells and collagen fibers Tunica adventitia → relatively thin Muscular arteries Medium-sized and small arteries Distributing arteries → smooth muscle cells allow them to regulate blood supply by either constricting or dilating. Tunica intima → well-developed internal elastic membrane Tunica adventitia → composed of a relatively thick layer Arterioles Transport blood from small arteries to capillaries Smallest arteries Capable of vasodilation and vasoconstriction Tunica intima→ no observable internal elastic membrane Tunica media → consists of 1or 2 layers of circular smooth muscle cells Systemic Circulation: Arteries Aorta Coronary arteries Arteries of the Head and neck Arteries of the upper Limb Abdominal Aorta and its Branches Arteries of the Pelvis Arteries of the Lower Limb Veins Types of Veins : Venules Small Veins Medium and Large Veins Portal Veins Valves Vasa Vasorum Venules and Small Veins Venules → very small veins Collects blood from the capillaries and transport it to small veins Small veins → receives blood from venules Medium and Large Veins Medium veins → collect blood from small veins and deliver it to large veins Large veins → Transport blood from the medium veins to the heart  Portal Veins 2 systems of portal veins in humans Hepatic portal veins → carry blood from GIT and spleen to dilated capillaries in liver Hypothalamohypophysial portal veins → carry blood from the hypothalamus of the brain to the anterior pituitary gland Valves Diameters greater than 2 mm Contains valves Mostly in lower limbs Varicose Enlarged, swollen, and twisting veins Appears blue or dark purple Valve malfunction → allow blood to flow in the wrong direction or to pool Systemic Circulation: Veins Three major veins return blood from the body to the right atrium: Coronary sinus Superior vena cava Inferior vena cava Veins of the Head and neck Veins of the upper Limb Veins of the Thorax Circulatory shock Inadequate blood flow throughout the body Due to failure of the mechanisms that maintain normal blood pressure. Stroke Decreased blood supply to a part of the brain It can occur as a result of a thrombosis, an embolism, or a hemorrhage Reference: Seeley's Anatomy & Physiology, 10th edition