L20 - Cardiovascular System PDF

L20- CARDIOVASCULAR SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, AUA LEARNING OUTCOMES Blood vessels and hemodynamics. Histology, Innervation and function. Differences between arteries and veins. Micro circulation and its...

L20- CARDIOVASCULAR SYSTEM Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, AUA LEARNING OUTCOMES Blood vessels and hemodynamics. Histology, Innervation and function. Differences between arteries and veins. Micro circulation and its functions.  CLASSIFICATION OF BLOOD VESSELS Blood vascular system: Heart Arteries Veins Capillaries Heart: A four-chambered muscular organ which pumps the blood to various parts of the body Each half of the heart has a - receiving chamber called atrium - pumping chamber called ventricle 23-Sep-24 3  Arteries: Are large blood vessels that take oxygenated blood away from the heart to be distributed throughout the body. Characteristic features of arteries: Thick walled Lumen is smaller Do not have valves An artery is usually accompanied by veins and nerves (neurovascular bundle) Arterioles: The minute branches of the arteries just visible to the naked eye 23-Sep-24 4  TYPES OF ARTERIES: Large sized arteries ( Elastic arteries) - Eg.,Pulmonary trunk, Aorta & its branches i.e brachiocephalic, subclavian and common carotid artery Medium sized arteries (Muscular arteries) - Eg. Radial artery, popliteal artery, temporal artery Smaller arteries (arterioles) 23-Sep-24 5  Veins: Blood vessels take deoxygenated blood from around the body back to the heart. Characteristic features: Thin walled Lumen is larger Have valves to maintain the unidirectional flow of blood against gravity However Valves are absent in the venae cavae, hepatic, renal, uterine, ovarian, cerebral, spinal, pulmonary & umbilical veins. Venules: Smaller veins 23-Sep-24 6  TYPES OF VEINS: Large sized veins - eg. vena cava and portal vein and their tributaries Medium sized veins Small sized veins(venules) 23-Sep-24 7   Capillaries: Networks of microscopic vessels which connect arterioles with venules Come in intimate contact with the tissues for exchange of nutrients  Sinusoids: Large, irregular, vascular spaces closely surrounded by the parenchyma of the organ They are different from capillaries in the following respects: - Lumen is wider and irregular - Walls are thinner and may be incomplete Found in liver, spleen, bone marrow 23-Sep-24 8 MICROSCOPIC STRUCTURE OF ARTERIES AND VEINS  Endothelial layer  Three coats (tunics) : Tunica intima (innermost) Tunica media (middle) Tunica adventitia (outermost) 23-Sep-24 9  ENDOTHELIUM:  Special type of epithelium lining the interior surface of blood vessels and lymphatic vessels  Forms an interface between circulating blood or lymph in the lumen and the rest of the vessel wall.  Simple squamous type of epithelium. 23-Sep-24 10  MICROSCOPIC STRUCTURE OF ARTERIES 1. TUNICA INTIMA (innermost layer):  Consists of following 4 components: a. Endothelium (simple squamous epithelium) b. Basal lamina c. Subendothelial connective tissue d. Internal elastic lamina (made of elastic material) 2. TUNICA MEDIA (intermediate layer):  Surrounds the tunica intima  Consists of elastic fibers & smooth muscles http://medcell.med.yale.edu/systems_cell_biol ogy/blood_vessels_lab.php 23-Sep-24 11  3. TUNICA ADVENTITIA/EXTERNA (outermost layer):  Composed mainly of connective tissue  Separated from the tunica media by external elastic lamina http://medcell.med.yale.edu/systems_cell_biol ogy/blood_vessels_lab.php 23-Sep-24 12 MICROSCOPIC STRUCTURE OF VEINS  The veins also have the same three layers as the arteries  But these three layers are not well defined http://bcrc.bio.umass.edu/bestofhistology/con tent/large-vein-2012 23-Sep-24 13 MICROSCOPIC STRUCTURE OF A LARGE (ELASTIC) ARTERY  Tunica intima: consists of all the 4 components  Tunica media: Thickest of all the three layers Contains high proportion of elastic fibers In between elastic lamellae are layers of smooth muscle cells  Tunica adventitia:  Made up of connective tissues  Relatively thinner and contains collagen fibers 23-Sep-24 14 MICROSCOPIC STRUCTURE OF A MEDIUM SIZED (MUSCULAR) ARTERY  Tunica intima: Contains all the 4components Internal elastic lamina is more clearly visible  Tunica media: Contains high proportion of smooth muscle cells http://www.courseweb.uottawa.ca/medicine- histology/english/cardiovascular/Fig13_Cardio  Tunica adventitia: vascular.htm Made of connective tissue Thicker than that of elastic artery 23-Sep-24 15  MICROSCOPIC STRUCTURE OF A LARGE VEIN  Tunica intima: Consists of endothelial cells, subendothelial connective tissues and few smooth muscle cells  Tunica media: Consists of smooth muscle cells, collagen fibers and fibroblasts This layer is thinner than that of in arteries Difficult to distinguish between the two http://www.courseweb.uo  Tunica adventitia: ttawa.ca/medicine- histology/english/cardiova Thicker & consists of smooth muscle cells, scular/Fig13_Cardiovascul collagen, elastic fibers & fibroblasts ar.htm 23-Sep-24 16 MICROSCOPIC STRUCTURE OF A MEDIUM SIZED VEIN  Tunica intima:  Consist of little or no sub endothelial connective tissue  Tunica media:  Consists of few layers of smooth muscle cells and collagen fibres and elastic fibers  Tunica adventitia:  Thicker than the media and consists of collagen and elastic fibers 23-Sep-24 17  Differences between artery and vein Artery Vein  Smaller overall diameter and  Large overall diameter and smaller lumen. larger lumen.  Thicker walls, do not collapse  Thinner walls, collapse after after death. death.  Flow of blood is more rapid.  Flow of blood slower.  High oxygen content of blood.  Low oxygen content.  Tunica intima is relatively  Tunica intima is relatively thicker. thinner.  Internal and external elastic  Internal and external elastic laminae are well developed. laminae are less developed.  Tunica media is muscular and  Tunica media is generally a considerably thicker. thin muscular layer.  Tunica adventitia is about half  Tunica adventitia is thickest the thickness of media and has coat of wall and is composed high elastin content. chiefly of collagen fibers.  No valves.  Valves are present.  TERMS RELATED TO THE ARTERIAL SUPPLY AND VENOUS DRAINAGE Arterial anastomosis: The communication between the arteries or branches of the arteries Collateral supply: Circulation through the anastomosis Supply of blood through a network of minor vessels and joined w ith adjacent vessels when a major vein or artery obstructed. End arteries: Arteries that do not anastomose with the neighbours Eg. Central artery of retina, central branches of cerebral arteries, arteries of spleen, kidney 23-Sep-24 19 23-Sep-24 20  Deep veins: A vein that is deep in the body and are almost beside an artery with the same name Eg, femoral vein with the femoral artery Superficial veins: Veins that are closer to the body surface Venous valves and functions: Veins have valves to maintain the unidirectional flow of blood against gravity Since the venous pressure is low (7mmHg), the valves are of utmost value in venous return Valves prevent backflow during venous return 23-Sep-24 21  Arterio-venous anastomosis (shunt): Is the communication between an artery and a vein When the organ is active these shunts are closed and the blood circulates through the capillaries However when the organ is at rest, the blood bypasses the capillary bed and is shunted back through the arterio- vnous anastomosis The shunt vessels may be straight or coiled, posses a thick muscular coat and is under the influence of sympathetic system Shunts of simple structures are found in the skin of nose, lips, erectile tissue of sexual organ and thyroid gland 23-Sep-24 22  http://www.doereport.com/generateexhibit.p hp?ID=10762&ExhibitKeywordsRaw=&TL=&A= 23-Sep-24 23  VASA VASORUM: The network of small blood vessels which supply the large blood vessels 23-Sep-24 24  LYMPHOID TISSUES  A drainage system which is accessory to venous system.  Larger particles(proteins and particulate matter) removed from the tissue fluid by the lymphatics  ‘Drainage system of coarse type’  The venous system as ‘drainage system of fine type’.  The tissue fluid flowing in the lymphatic is called LYMPH. 23-Sep-24 25  DIFFERENT LYMPHOID TISSUES IN THE BODY: 1. Central lymphoid tissue 2. Peripheral lymphoid organs 3. Circulating lymphocytes 4. Lymphatic follicle (nodule) 1. Central lymphoid tissue: a. Bone marrow b. Thymus Functions: The bone marrow helps differentiation of the B- lymphocytes which are capable of synthesizing antibodies after getting transformed into plasma cells 23-Sep-24 26  Thymus helps in the differentiation of immunologically competent T-lymphocytes 2. Peripheral lymphoid organs: a. Lymph nodes b. Spleen FUNCTIONS OF LYMPH NODES: Filters the lymph and remove the particulate matters such as carbon, bacteria , dust , cancer cells by phagocytic action. Produces lymphocytes. Plasma cells produces the antibodies FUNCTIONS OF SPLEEN: Filters blood by removing the worn out RBC,WBC, and platelets 23-Sep-24 27  THE MAJOR LYMPHATIC DUCTS IN THE BODY:  The filtered lymph passes through the larger lymphatics and collected into 2 large trunks, the thoracic duct and right lymphatic duct. 23-Sep-24 28 Hemodynamics: Factors affecting blood flow Blood flow – volume of blood that flows through any tissue in a given period of time (in mL/min) Total blood flow is cardiac output (CO) Volume of blood that circulates through systemic (or pulmonary) blood vessels each minute CO = heart rate (HR) x stroke volume (SV) Distribution of CO depends on Pressure differences that drive blood through tissue Flows from higher to lower pressure Resistance to blood flow in specific blood vessels Higher resistance means smaller blood flow Copyright 2009, John Wiley & Sons, Inc.  Blood Pressure Contraction of ventricles generates blood pressure Systolic BP – highest pressure attained in arteries during systole Diastolic BP – lowest arterial pressure during diastole Pressure falls progressively with distance from left ventricle Blood pressure also depends on total volume of blood Copyright 2009, John Wiley & Sons, Inc. Vascular resistance Opposition to blood flow due to friction between blood and walls of blood vessels Depends on 1. Size of lumen – vasoconstriction males lumen smaller meaning greater resistance 2. Blood viscosity – ratio of RBCs to plasma and protein concentration, higher viscosity means higher resistance 3. Total blood vessel length – resistance directly proportional to length of vessel 400 miles of additional blood vessels for each 2.2lb. of fat Copyright 2009, John Wiley & Sons, Inc. Venous return Volume of blood flowing back to heart through systemic veins Occurs due to pressure generated by constriction of left ventricle Small pressure difference from venule (16 mmHg) to right ventricle (0 mmHg) sufficient Copyright 2009, John Wiley & Sons, Inc.  Skeletal Muscle Pump 2 other mechanisms Skeletal muscle pump – milks blood in 1 direction due to valves Respiratory pump – due to pressure changes in thoracic and abdominal cavities Copyright 2009, John Wiley & Sons, Inc. Proximal valve Distal valve 1 2 3  REFERENCES Drake R.L., Gray’s Anatomy for Students, 2nd Edition, 2009, Churchill Livingstone Moore, Clinically Oriented Anatomy, 6th Edition, 2009, Lippincott Williams & Wilkins Standring, Gray’s Anatomy: The Anatomical Basis of Clinical Practice, 40thEdition, 2008 Johannes W Rohen, Color Atlas of Anatomy: A photographic study of the human body, 7th Edition, Lippincott Williams & Wilkins Kenneth S Saladin, Human Anatomy, 2nd Edition, 2008, McGraw-Hill Companies 23-Sep-24 35