Circulatory System Student Copy PDF

CI RC UL ATORY SYSTEM P R E P A P R E D B Y : J I A N M I D J A. O C O , P T R P P R E S E N T E D B Y : O R I E L M. R E P I L , P T R P, M D , O H P 1  CARD...

CI RC UL ATORY SYSTEM P R E P A P R E D B Y : J I A N M I D J A. O C O , P T R P P R E S E N T E D B Y : O R I E L M. R E P I L , P T R P, M D , O H P 1  CARDIOVASCULAR BLOOD Cardio = heart BLOOD HEART VESSELS Vascular = blood vessels OVERVIEW BLOOD – contributes to homeostasis by transporting oxygen, carbon dioxide, nutrients, and hormones to and from your body’s cells. – It also helps regulate body pH and temperature and provides protection against disease through phagocytosis and the production of antibodies. – is a liquid connective tissue that consists of cells surrounded by a liquid extracellular matrix (blood plasma). INTERSTITIAL FLUID - is the fluid that bathes body cells and is constantly renewed by the blood FUN CT IONS OF BLOOD Transportation. Blood transports inhaled oxygen from the lungs to the cells of the body and carbon dioxide from the body cells to the lungs for exhalation. Regulation. Blood helps regulate pH using buffers (chemicals that convert strong acids or bases into weak ones). It also helps adjust body temperature through the heat- absorbing and coolant properties of the water in blood plasma and its variable rate of flow through the skin, where excess heat can be lost from the blood to the environment. Protection. Blood can clot (become gel-like), which protects against its excessive loss from the cardiovascular system after an injury. In addition, its white blood cells protect against disease by carrying on phagocytosis. PHYSICAL CHARACTERISTIC OF BLOOD BLOOD is denser and more viscous (thicker) than water and feels slightly sticky. Blood temperature: is 38°C (100.4°F), about 1°C higher than oral or rectal body temperature Slightly alkaline pH ranging from 7.35 to 7.45 (average =7.4). The color of blood varies with its oxygen content. BRIGHT RED – if saturated with oxygen DARK RED – if unsaturated with oxygen FORMED ELEMENTS OF BLOOD Red blood cells (RBCs) or erythrocytes – transport oxygen from the lungs to body cells and deliver carbon dioxide from body cells to the lungs. (lives until 120 days only, produced in the bone marrow) White blood cells (WBCs) or leukocytes – protect the body from invading pathogens and other foreign substances. There are several types of WBCs: neutrophils, basophils, eosinophils, monocytes, and lymphocytes. – Lymphocytes are further subdivided into B lymphocytes (B cells), T lymphocytes (T cells), and natural killer (NK) cells. Platelets – the final type of formed element, are fragments of cells that do not have a nucleus. release chemicals that promote vascular spasm and blood clotting  CARDIOVASCULAR BLOOD OVERVIEW Cardio = heart Vascular = blood vessels BLOOD HEART VESSELS HEART contributes to homeostasis by pumping blood through blood vessels to the tissues of the body to deliver oxygen and nutrients and remove wastes. The heart beats about 100,000 times every day, which adds up to about 35 million beats in a year, and approximately 2.5 billion times in an average lifetime. Even while you are sleeping, your heart pumps 30 times its own weight each minute (about 5 liters) to the lungs and the same volume to the rest of the body. At this rate, your heart pumps more than about 14,000 liters (3600 gal) of blood in a day, or 5 million liters (1.3 million gal) in a year. Heart pumps more vigorously when you are active. Actual blood volume your heart pumps in a single day is much larger A N ATO M Y OF T H E H E A R T Location of the Heart HEART - relatively small, roughly the same size (but not the same shape) as your closed fist, rests on the diaphragm, near the midline of the thoracic cavity. – Long axis: about 12 cm (5 in.) – Width: 9 cm (3.5 in.) at its broadest point – Depth: 6 cm (2.5 in.), anterior to posterior – Average mass: 250 g (8 oz) in adult females and 300 g (10 oz) in adult males  A N ATO M Y OF T H E H E A R T heart lies in the MEDIASTINUM, about two-thirds of the mass of the heart lies to the left of the body’s midline. APEX - pointed part, formed by the tip of the left ventricle (a lower chamber of the heart) It is directed anteriorly, inferiorly, and to the left. BASE - is opposite the apex and is its posterior aspect. It is formed by the atria (upper chambers) of the heart, mostly the left atrium 8 /1 7 / 2 0 2 4 11 PERICARDIUM PERICARDIUM - membrane that surrounds and protects the heart and confines its position in the mediastinum, while allowing sufficient freedom of movement for vigorous and rapid contraction. The pericardium consists of two main parts: 1. FIBROUS PERICARDIUM - superficial, and is composed of tough, inelastic, dense irregular connective tissue. - prevents overstretching of the heart, provides protection, and anchors the heart in the mediastinum. 2. SEROUS PERICARDIUM - deeper, thinner, more delicate mesothelial membrane that forms a double layer around the heart SEROUS PERICARDIUM PARIETAL LAYER OF SEROUS PERICARDIUM – Outermost layer that lines the inside of the fibrous pericardium. VISCERAL LAYER OF SEROUS PERICARDIUM/Epicardium - innermost layer of the heart wall and adheres tightly to the surface of the heart. PERICARDIAL FLUID - a thin film of a few milliliters of lubricating serous fluid. - a slippery secretion of pericardial cells that reduces friction between the layers of the serous pericardium as the heart moves. PERICARDIAL CAVITY - space that contains the few milliliters of pericardial fluid L AY E R S O F H E A R T W A L L 1. EPICARDIUM (external layer) - imparts a smooth, slippery texture to the outermost surface of the heart that contains blood vessels, lymphatics, and nerves that supply the myocardium. A. VISCERAL LAYER OF THE SEROUS PERICARDIUM - thin, transparent outer layer of the heart wall that is composed of mesothelium. Beneath the mesothelium is a variable layer of delicate fibroelastic tissue and adipose tissue. B. ADIPOSE TISSUE - predominates and becomes thickest over the ventricular surfaces, where it houses the major coronary and cardiac vessels of the heart. L AY E R S O F H E A R T W A L L 2. MYOCARDIUM (middle layer) - responsible for the pumping action of the heart and is composed of cardiac muscle tissue. It makes up approximately 95% of the heart wall. - cardiac muscle fibers are organized in bundles that swirl diagonally around the heart and generate the strong pumping actions of the heart 3. ENDOCARDIUM (innermost layer) - is a thin layer of endothelium overlying a thin layer of connective tissue. - it provides a smooth lining for the chambers of the heart and covers the valves of the heart. the smooth endothelial lining minimizes the surface friction as blood passes through the heart.  CHAMBERS OF THE HEART ATRIA/ATRIUM – 2 superior receiving chambers – The paired atria receive blood from blood vessels returning blood to the heart, called veins, while the ventricles eject the blood from the heart into blood vessels called arteries. VENTRICLE – 2 inferior pumping chambers AURICLE - wrinkled pouchlike structure on the anterior surface of atrium. It increases the capacity of an atrium so that it can hold a greater volume of blood. SULCI – series of groove on the surface of the heart, that contain coronary blood vessels and a variable amount of fat. – Deep CORONARY SULCUS (coron- = resembling a crown) encircles most of the heart and marks the external boundary between the superior atria and inferior ventricles. CHAMBERS OF THE HEART – ANTERIOR INTERVENTRICULAR SULCUS - is a shallow groove on the anterior surface of the heart that marks the external boundary between the right and left ventricles on the anterior aspect of the heart. – POSTERIOR INTERVENTRICULAR SULCUS - marks the external boundary between the ventricles on the posterior aspect of the heart  VEINS always carry blood towards the heart R I G H T AT R I U M forms the right surface of the heart and receives blood from three veins: – the superior vena cava, inferior vena cava, and coronary sinus about 2–3 mm (0.08–0.12 in.) in average thickness. The anterior and posterior walls of the right atrium are very different. – inside of the posterior wall is smooth; – inside of the anterior wall is rough due to the presence of muscular ridges called PECTINATE MUSCLES which also extend into the auricle INTERATRIAL SEPTUM – thin partition in between the right atrium and left atrium R I G H T AT R I U M FOSSA OVALIS - an oval depression on the septum, the remnant of the foramen ovale, an opening in the interatrial septum of the fetal heart that normally closes soon after birth RIGHT ATRIOVENTRICULAR VALVE/tricuspid valve – where blood passes from the right atrium into the right ventricle (consists of 3 cusps/leaflets) The valves of the heart are composed of dense connective tissue covered by endocardium.  ARTERIES always take blood away from the heart (Artery = Away) RIGHT VENTRICLE is about 4–5 mm (0.16–0.2 in.) in average thickness and forms most of the anterior surface of the heart. TRABECULAE CARNEAE – series of ridges formed by raised bundles of cardiac muscle fibers inside the right ventricle. CORDAE TENDINAE – tendon-like cords where cusps of right AV valve is connected. PAPILLARY MUSCLES - cone-shaped trabeculae carneae where cordae tendinae is connected. INTERVENTRICULAR SEPTUM – internal partition that separates the right ventricle from the left ventricle (BLOOD) RIGHT VENTRICLE > PULMONARY VALVE > PULMONARY TRUNK > R/L PULMONARY ARTERIES > LUNGS  MITRAL VALVE/BICUSPID VALVE TRICUSPID VALVE LE FT ATRIUM is about the same thickness as the right atrium and forms most of the base of the heart It receives blood from the lungs through four pulmonary veins. anterior and posterior internal wall of left atrium is smooth. Blood passes from the left atrium into the left ventricle through the LEFT ATRIOVENTRICULAR VALVE (bicuspid or mitral) - has two cusps. (BLOOD) LEFT ATRIUM > LEFT ATRIOVENTRICULAR VALVE/mitral > LEFT VENTRICLE > LEFT VENTRICLE is the thickest chamber of the heart, averaging 10–15 mm (0.4–0.6 in.), and forms the apex of the heart Like the right ventricle, the left ventricle contains trabeculae carneae and has chordae tendineae that anchor the cusps of the bicuspid valve to papillary muscles. Some of the blood in the aorta flows into the CORONARY ARTERIES, which branch from the ascending aorta and carry blood to the heart wall. The remainder of the blood passes into the AORTIC ARCH (thoracic aorta) and DESCENDING AORTA (abdominal aorta). Branches of the aortic arch and descending aorta carry blood throughout the body. (BLOOD) LEFT VENTRICLE > AORTIC VALVE > ASCENDING AORTA LEFT VENTRICLE During fetal life, a temporary blood vessel, called the DUCTUS ARTERIOSUS, shunts blood from the pulmonary trunk into the aorta. Hence, only a small amount of blood enters the nonfunctioning fetal lungs The ductus arteriosus normally closes shortly after birth, leaving a remnant known as the LIGAMENTUM ARTERIOSUM which connects the aortic arch and pulmonary trunk FIBROUS SKELETON OF THE HEART Consists of 4 dense connective tissue rings that surround the valves of the heart, fuse with one another, and merge with the interventricular septum. Forms the structural foundation for the heart valves, that prevents overstretching of the valves as blood passes through them. It also serves as a point of insertion for bundles of cardiac muscle fibers and acts as an electrical insulator between the atria and ventricles. H E A R T V A LV E S ATRIOVENTRICULAR VALVE (AV Valve) - valves located between an atrium and a ventricle o MITRAL/BICUSPID VALVE – between left atrium and left ventricle o TRICUSPID VALVE – between right atrium and right ventricle SEMILUNAR VALVE (SL Valve) - aortic and pulmonary valves, because they are made up of three crescent moon–shaped cusps  C O R O N A R Y C I R C U L AT I O N Nutrients are not able to diffuse quickly enough from blood in the chambers of the heart to supply all layers of cells that make up the heart wall. For this reason, the myocardium has its own network of blood vessels, the CORONARY CIRCULATION or cardiac circulation (coron- = crown). The CORONARY ARTERIES branch from the ascending aorta and encircle the heart as a crown encircles the head While the heart is contracting, little blood flows in the coronary arteries because they are squeezed shut. When the heart relaxes, however, the high pressure of blood in the aorta propels blood through the coronary arteries, into capillaries, and then into CORONARY VEINS  LEFT and RIGHT CORONARY ARTERIES - branch from the ascending aorta and supply oxygenated blood to the myocardium CORONARY ARTERIES RIGHT CORONARY ARTERY - supplies small branches (atrial branches) to the right atrium. It continues inferior to the right auricle and ultimately divides into: o INFERIOR (posterior) INTERVENTRICULAR ARTERY - follows the posterior interventricular sulcus and supplies the walls of the two ventricles with oxygenated blood. o MARGINAL BRANCH - beyond the coronary sulcus runs along the right margin of the heart and transports oxygenated blood to the wall of the right ventricle.  LEFT and RIGHT CORONARY ARTERIES - branch from the ascending aorta and supply oxygenated blood to the myocardium CORONARY ARTERIES LEFT CORONARY ARTERY - passes inferior to the left auricle and divides into: o CIRCUMFLEX ARTERY - lies in the coronary sulcus and distributes oxygenated blood to the walls of the left ventricle and left atrium. o ANTERIOR INTERVENTRICULAR ARTERY or left anterior descending (LAD) artery - is in the anterior interventricular sulcus and supplies oxygenated blood to the walls of both ventricles. CORONARY VEINS After blood passes through the arteries of the coronary circulation, it flows into capillaries, where it delivers oxygen and nutrients to the heart muscle and collects carbon dioxide and waste, and then moves into CORONARY VEINS. Most of the deoxygenated blood from the myocardium drains into a large vascular sinus in the coronary sulcus on the posterior surface of the heart, called the CORONARY SINUS. The deoxygenated blood in the coronary sinus empties into the right atrium. CORONARY VEINS The principal tributaries carrying blood into the coronary sinus are the following: GREAT CARDIAC VEIN in the anterior interventricular sulcus, which drains the areas of the heart supplied by the left coronary artery (left and right ventricles and left atrium) MIDDLE CARDIAC VEIN in the posterior interventricular sulcus, which drains the areas supplied by the inferior interventricular artery of the right coronary artery (left and right ventricles) SMALL CARDIAC VEIN in the coronary sulcus, which drains the right atrium and right ventricle ANTERIOR CARDIAC VEIN, which drain the right ventricle and open directly into the right atrium OVERVIEW CARDIOVASCULAR BLOOD Cardio = heart BLOOD HEART VESSELS Vascular = blood vessels BLOOD VESSELS contribute to homeostasis by providing the structures for the flow of blood to and from the heart and the exchange of nutrients and wastes in tissues. They also play an important role in adjusting the velocity and volume of blood flow. The five main types of blood vessels are 1. Arteries 2. Arterioles 3. Capillaries 4. Venules 5. Veins FIVE MAIN TYPES OF BLOOD VESSELS 1. ARTERY – carries oxygenated blood away from the heart to other organs 2. ARTERIOLES – smaller artery that branched off from medium sized arteries 3. CAPILLARIES/BLOOD CAPILLARIES – smallest BV, numerous tiny vessels where arterioles branched off as it enters a tissue. The thin walls of capillaries allow the exchange of substances between the blood and body tissues. 4. VENULES – small veins formed by a group of capillaries reunited within a tissue 5. VEINS – merged venules, larger blood vessels that convey deoxygenated blood from the tissues back to the heart. ARTERY The wall of an artery has the three layers of a typical blood vessel but has a thick muscular-to-elastic tunica media. Due to their plentiful elastic fibers, arteries normally have high compliance, which means that their walls stretch easily or expand without tearing in response to a small increase in pressure. 1. ELASTIC ARTERY/conducting arteries - largest arteries in the body, perform an important function – PRESSURE RESERVOIR (help propel blood onward while the ventricles are relaxing) o Aorta and Pulmonary trunk  ARTERY 2. MUSCULAR ARTERY/medium sized-arteries so called because their tunica media contains more smooth muscle and fewer elastic fibers than elastic arteries. Due to thick walls, they are capable of greater vasoconstriction and vasodilation to adjust the rate of blood flow. Because of the reduced amount of elastic tissue in the walls of muscular arteries, these vessels do not have the ability to recoil and help propel the blood like the elastic arteries. o Femoral artery and Axillary artery DISTRIBUTING ARTERIES – Muscular artery continues to branch and ultimately distribute blood to each of the various organs o Brachial artery , Radial artery  A change in arteriole diameter can also affect blood pressure: ARTERIOLES Vasoconstriction of arterioles increases blood pressure Vasodilation of arterioles decreases blood pressure meaning small arteries, an abundant microscopic vessels that regulate the flow of blood into the capillary networks of the body’s tissues METARTERIOLE - terminal end of the arteriole, tapers toward the capillary junction. At the metarteriole–capillary junction, the distal-most muscle cell forms the PRECAPILLARY SPHINCTER which monitors the blood flow into the capillary; the other muscle cells in the arteriole regulate the resistance (opposition) to blood flow Aka RESISTANCE VESSEL – because it plays a key role in regulating blood flow from arteries into capillaries by regulating resistance, the opposition to blood flow due to friction between blood and the walls of blood vessels. Smaller BV = greater FRICTION = increase RESISTANCE  referred to as EXCHANGE VESSELS, due to its thin-walled vessels. CAPILLARIES smallest of blood vessels, have diameters of 5–10 μm and form the U-turns that connect the arterial outflow to the venous return primary function: MICTURATON (exchange of substances between the blood and interstitial fluid) (blood) – metarteriole > capillaries > postcapillary venule 3 types of capillaries: 1. CONTINUOUS CAPILLARIES – CNS, lungs, muscle tissue, and the skin. 2. FENESTRATED CAPILLARIES – kidneys, intestinal villi, choroid plexuses of the ventricles in the brain, ciliary processes of the eyes, and most endocrine glands. 3. SINUSOIDS (wider) – red bone marrow, liver, spleen, anterior pituitary, parathyroid and suprarenal glands  VENULES smallest venules, measuring 10 μm to 50 μm in diameter have thin walls that do not readily maintain their shape, drains the capillary blood and begin the return flow of blood back toward the heart Function: significant sites of exchange of nutrients and wastes and white blood cell emigration, and for this reason form part of the microcirculatory exchange unit along with the capillaries. POSTCAPILLARY VENULES - initially receive blood from capillaries MUSCULAR VENULES - (50 μm to 200 μm) have thicker walls across which exchanges with the interstitial fluid can no longer occur. VEINS very thin walls relative to their total diameter (range in size from 0.5 mm in diameter for small veins to 3 cm in the large superior and interior venae cava entering the heart) Many veins, especially those in the limbs, also contain valves (thin folds of tunica intima that form flaplike cusps) The VALVE CUSPS project into the lumen, pointing toward the heart that aids in venous return by preventing the backflow of blood. SUMMARY OF FUNCTION BLOOD VESSEL FUNCTION ELASTIC ARTERIES Conduct blood from heart to muscular arteries. MUSCULAR ARTERIES Distribute blood to arterioles. ARTERIOLES Deliver blood to capillaries and help regulate blood flow from arteries to capillaries. CAPILLARIES Permit exchange of nutrients and wastes between blood and interstitial fluid; distribute blood to postcapillary venules. POSTCAPILLARY VENULES Pass blood into muscular venules; permit exchange of nutrients and wastes between blood and interstitial fluid and function in white blood cell emigration. MUSCULAR VENULES Pass blood into vein; act as reservoirs for accumulating large volumes of blood (along with postcapillary venules). VEINS Return blood to heart, facilitated by valves in limb veins.  CIRCULATORY ROUTE SY STEM IC CIR CU LAT ION (P OS TNATAL R OUT E) P UL MONARY CIRCU LAT IO N (P OST NATAL ROU TE) FETA L CIRCULATION HEPATIC P ORTA L CIRCU LAT IO N 8 /1 7 / 2 0 2 4 54 CIRCULATORY ROUTE S In postnatal (after birth) circulation, the heart pumps blood into two closed circuits with each beat— 1. SYSTEMIC CIRCULATION 2. PULMONARY CIRCULATION The left side of the heart is the pump for SYSTEMIC CIRCULATION; it receives bright red oxygenated (oxygen-rich) blood from the lungs. The left ventricle ejects blood into the aorta. From the aorta, the blood divides into separate streams, entering progressively smaller systemic arteries that carry it to all organs throughout the body— except for the pulmonary alveoli (air sacs) of the lungs, which are supplied by the pulmonary circulation. SY ST E M I C C I R C U L AT I O N In systemic tissues, arteries give rise to smaller-diameter arterioles, which finally lead into extensive beds of systemic capillaries. Exchange of nutrients and gases occurs across the thin capillary walls. Blood unloads O2 (oxygen) and picks up CO2 (carbon dioxide). In most cases, blood flows through only one capillary and then enters a systemic venule. Venules carry deoxygenated (oxygen-poor) blood away from tissues and merge to form larger systemic veins. Ultimately the blood flows back to the right atrium. SY ST E M I C C I R C U L AT I O N Subdivisions: 1. CORONARY CIRCULATION – supplies the myocardium of the heart 2. CEREBRAL CIRCULATION – supplies the brain (Circle of Willis) 3. HEPATIC PORTAL CIRCULATION – extends from digestive canal to liver PULMONARY CIRCULATION The right side of the heart is the pump for PULMONARY CIRCULATION; it receives all of the dark-red deoxygenated blood returning from the systemic circulation. Blood ejected from the right ventricle flows into the pulmonary trunk, which branches into pulmonary arteries that carry blood to the right and left lungs. In pulmonary capillaries, around pulmonary alveoli, blood unloads CO2, which is exhaled, and picks up O2 from inhaled air. The freshly oxygenated blood then flows into pulmonary veins and returns to the left atrium. After birth, PULMONARY ARTERIES are the only arteries that carry deoxygenated blood PULMONARY VEINS are the only veins that carry oxygenated blood PULMONARY CIRCULATION carries deoxygenated blood from the right ventricle to the pulmonary alveoli within the lungs and returns oxygenated blood from the pulmonary alveoli (air sacs) to the left atrium PULMONARY TRUNK emerges from the right ventricle and passes superiorly, posteriorly, and to the left. It then divides into two branches: – the right pulmonary artery to the right lung – the left pulmonary artery to the left lung F E TA L C I R C U L AT I ON exists only in the fetus and contains special structures that allow the developing fetus to exchange materials with its mother via PLACENTA It differs from the postnatal (after birth) circulation because the lungs, kidneys, and digestive canal organs do not begin to function until birth. The fetus obtains O2 and nutrients from the maternal blood and eliminates CO2 and other wastes into it. As soon as a full-term fetus is delivered, there is increased uptake of oxygen by the lungs during the infant’s first and subsequent inhalations. Once breathing begins, placental blood flow ceases. As a direct result of aeration of the lungs, the ductus arteriosus and ductus venosus undergo vasoconstriction and the foramen ovale closes. H E PAT I C P O R TA L C I R C U L AT I O N HEPATIC PORTAL VEIN - receives blood from capillaries of digestive canal organs and the spleen and delivers it to the sinusoids of the liver PORTAL VEIN - vein that carries blood from one capillary network to another After a meal, hepatic portal blood is rich in nutrients absorbed from the digestive canal. The liver stores some of them and modifies others before they pass into the general circulation. LIVER is receiving nutrient-rich but deoxygenated blood via the hepatic portal vein, it is also receiving oxygenated blood via the hepatic artery, a branch of the celiac trunk. The oxygenated blood mixes with the deoxygenated blood in sinusoids (microvascular beds). Eventually, blood leaves the sinusoids of the liver through the HEPATIC VEINS, which drain into the inferior vena cava. Q U E S T I O N S ?