The Circulatory System The Nature of Blood Circulation

The Circulatory System

The Nature of Blood Circulation § General Information… § A circulatory system distributes materials throughout the vertebrate body (and some invertebrates) § Uses a transport medium called blood. § A heart is a muscular organ that pumps the transport medium (blood) through vessels. § Blood and interstitial fluid (fluid between cells) make up the body’s internal environment

There are 2 Kinds of Circulatory Systems Open Or Closed Well actually 3 if you consider that Poriferans, like sponges, exchange gases directly with the environment.

Direct Circulation: Diffussion.

Open Circulatory Systems Open circulatory system (of arthropods or mollusks) - Blood moves through hearts and large vessels, but also mixes with interstitial fluid aorta heart pump spaces or cavities in body tissues A In a grasshopper’s open system, a heart (not like yours) pumps blood through a vessel, a type of aorta. From there, blood moves into tissue spaces, mingles with interstitial fluid, then reenters the heart at openings in the heart wall. Fig. 37 -2 a, p. 638

Closed Circulatory Systems Closed circulatory system (of annelids (worms) and all vertebrates) - Blood remains inside heart and blood vessels - Molecules (CO 2 & O 2) diffuse between blood and interstitial fluid at capillaries dorsal blood vessel pump largediameter blood vessels capillary bed (many small vessels that serve as a diffusion zone) large-diameter blood vessels two of five hearts ventral blood gut cavity vessels B The closed system of an earthworm confines blood inside pairs of muscular hearts near the head end and inside many blood vessels. Fig. 37 -2 b, p. 638

Evolution of Circulation in Vertebrates § Fishes • Heart with two chambers • Single circuit of circulation § Amphibians • Heart with three chambers • Two partially separated circuits § Birds and mammals • Heart with four chambers • Two fully separate circuits

Single Circuit of Circulation capillary beds of gills heart A In fishes, the heart has two chambers: one atrium and one ventricle. Blood flows through one circuit. It picks up oxygen in the capillary beds of the gills, and delivers it to capillary beds in all body tissues. Oxygen-poor blood then returns to the heart. rest of body Fig. 37 -3 a, p. 639

Two Partially Separate Circuits of Circulation lungs right atrium left atrium ventricle rest of body B In amphibians, the heart has three chambers: two atria and one ventricle. Blood flows along two partially separated circuits. The force of one contraction pumps blood from the heart to the lungs and back. The force of a second contraction pumps blood from the heart to all body tissues and back to the heart. Fig. 37 -3 b, p. 639

Circulation in Birds and Mammals § The four-chambered heart has two separate halves, each with an atrium and a ventricle § Each half pumps blood in a separate circuit • Pulmonary circuit: Blood flows from right half of heart, to lungs (gains oxygen), to left half of heart • Systemic circuit: Blood flows from left half of heart, to body (loses oxygen), to right half of heart

Two Fully Separate Circuits of Circulation lungs right atrium right ventricle left atrium left ventricle C In birds and mammals, the heart has four chambers: two atria and two ventricles. The blood flows through two fully separated circuits. In one circuit, blood flows from the heart to the lungs and back. In the second circuit, blood flows from the heart to all body tissues and back. rest of body Fig. 37 -3 c, p. 639

Analogy of Slowing Blood in Capillaries lake river in river out 1 2 3 123 D Why flow slows in capillaries. Picture a volume of water in two fast rivers flowing into and out of a lake. The flow rate is constant, with an identical volume moving from points 1 to 3 in the same interval. However, flow velocity decreases in the lake. Why? The volume spreads out through a larger crosssectional area and flows forward a shorter distance during the specified interval. This extra time allows for diffusion of gases, like oxygen into cells and carbon dioxide out of cells, as well as nutrients like sugars, fats, and proteins. Fig. 37 -3 d, p. 639

Overview of Circulatory Systems § Fill in the blank. § Many animals have either an ____ or a ____ circulatory system that transports substances to and from all body tissues. § Some organisms have neither, achieving basic circulation by _____, which is the direct exchange of important biomolecules with the environment. § All vertebrates have a _______ circulatory system, in which blood is ________________.

Overview of Circulatory Systems § Many animals have either an open or a closed circulatory system that transports substances to and from all body tissues § Some organisms have neither, achieving basic circulation by diffusion, which is the direct exchange of important biomolecules with the environment. § All vertebrates have a closed circulatory system, in which blood is always contained within the heart or blood vessels

Characteristics of Blood § Blood, considering it is made of cells, can be called a large interconnect tissue.

Blood Cells § Blood consists mainly of plasma, a protein-rich fluid that carries wastes, gases and nutrients. • Blood cells and platelets form in bone marrow and are transported in plasma. § Platelets are fragments of megakaryocytes, active in clotting. § Red blood cells (erythrocytes) • Contain hemoglobin that carries oxygen from lungs to tissues • Quantified in cell count § White blood cells (leukocytes) • Defend the body from pathogens • Neutrophils, basophils, eosinophils, monocytes, and lymphocytes (B and T cells)

Components of Human Blood Components Amounts Main Functions Plasma Portion (50 -60% of total blood volume) 1. Water 91 -92% of total plasma volume 2. Plasma proteins (albumins, globulins, fibrinogen, etc. 7 -8% 3. Ions, sugars, lipids, amino acids, hormones, vitamins, 1 -2% dissolved gases, etc. Solvent Defense, clotting, lipid transport, extracellular fluid volume controls Nutrition, defense, respiration, extracellular fluid volume controls, cell communication, etc. Cellular Portion (40 -50% of total blood volume; numbers per microliter) 1. Red blood cells Oxygen, carbon 4, 600, 000 -5, 400, 000 dioxide transport to and from lungs 2. White blood cells: Neutophils Lymphoctyes Monocytes (macrophages) Eosinophils Basophils 3, 000 -6, 750 1, 000 -2, 700 150 -720 100 -380 25 -90 3. Platelets 250, 000 -300, 000 Fast-acting phagocytosis Immune responses Phagocytosis Killing parasitic worms Anti-inflammatory secretions Red Roles in blood clotting blood cell White blood cell platelet Stepped Art Fig. 37 -4, p. 640

Cellular Components of Human Blood stem cell in bone marrow myeloid stem cell red blood cell precursor granulocyte precursor lymphoid stem cell monocyte precursor megakaryocytes platelets red blood cells (erythrocytes) neutrophils basophils monocytes T lymphocytes eosinophils (immature (mature in phagocytes) thymus) B lymphocytes (mature in bone marrow) Fig. 37 -5, p. 641

Hemostasis § Hemostasis = Heme (blood) stasis (balance) • Keeping blood pressure/volume stable. § How do we stop bleeding? § Initiated by a hormone cascade when an injury is sustained and blood vessels are broken. § Hemostasis is a three-phase process that stops blood loss, constructs a framework for repairs • Damaged vessel constricts • Platelets accumulate • Cascading enzyme reactions involving plasma proteins cause clot formation

Three-Phase Process of Hemostasis Stimulus A blood vessel is damaged. Phase 1 response A vascular spasm constricts the vessel. Phase 2 response Platelets stick together plugging the site. Phase 3 response Clot formation starts: 1. Enzyme cascade results in activation of Factor X. 2. Factor X converts prothrombin in plasma to thrombin 3. Thrombin converts fibrinogen, a plasma protein, to fibrin threads. 4. Fibrin forms a net that entangles cells and platelets, forming a clot. Stepped Art Fig. 37 -6, p. 642

Blood Typing § Blood type • Genetically determined differences in molecules on the surface of red blood cells

Agglutination § Agglutination • Clumping of foreign cells by plasma proteins • When blood of incompatible types mixes, the immune system attacks the unfamiliar molecules Light micrographs showing (a) an absence of agglutination in a mixture of two different yet compatible blood types and (b) agglutination in a mixture of incompatible types.

ABO Blood Typing § Blood type O is a universal donor; blood type AB can receive blood from any donor

Mixing ABO Blood Types O Blood Type of Donor A B AB Blood Type of Recipient O A B AB Fig. 37 -8, p. 643

Rh Blood Typing § An Rh- mother may develop Rh+ antibodies if blood from an Rh+ child enters her bloodstream during childbirth § These antibodies may attack the red blood cells of the next Rh+ fetus

Rh Complications of Pregnancy How Rh differences can complicate pregnancy.

Blood Composition and Function § Fill in the blanks. § Vertebrate blood is a fluid connective ____. § It consists of _______, ________, and _____ (the transport medium) § _______ cells function in gas exchange; _______ cells defend tissues, and _____ function in clotting

Blood Composition and Function § Vertebrate blood is a fluid connective tissue § It consists of red blood cells, white blood cells, platelets, and plasma (the transport medium) § Red blood cells function in gas exchange; white blood cells defend tissues, and platelets function in clotting

Human Cardiovascular System § The term “cardiovascular” comes from the Greek kardia (for heart) and Latin vasculum (vessel) § In a cardiovascular circuit, blood flows from the heart through arteries, arterioles, capillaries, venules, veins, and back to the heart.

Two Circuits of the Human Cardiovascular System § Pulmonary circuit • Oxygen-poor blood flows from the heart, through a pair of lungs, then back to the heart • Blood takes up oxygen in the lungs § Systemic circuit • Oxygenated blood flows from the heart (through the aorta) into capillary beds where it gives up O 2 and takes up CO 2, then flows back to the heart

Pulmonary Circuit of the Human Cardiovascular System right pulmonary artery capillary bed of right lung Accessing the lungs to rid blood stream of excess CO 2 & to replenish O 2 pulmonary trunk left pulmonary artery capillary bed of left lung to systemic circuit from systemic circuit pulmonary veins heart Blood vessels carrying oxygenated blood are shown in red. Those that hold oxygenpoor blood are color-coded blue. Fig. 37 -10 a, p. 644

Systemic Circuit of the Human Cardiovascular System (pulmonary vessels to and from thoracic cavity) capillary beds of head, upper extremities to pulmonary aorta circuit from pulmonary circuit heart Accessing the rest of the body to deliver O 2 & to retrieve CO 2 (diaphragm, the muscular partition between thoracic and abdominal cavities) Pulmonary and systemic circuits of the human cardiovascular system. Blood vessels carrying oxygenated blood are shown in red. Those that hold oxygen-poor blood are color-coded blue. capillary beds of other organs in thoracic cavity capillary bed of liver capillary beds of intestines B Systemic Circuit for Blood capillary beds of other abdominal Flow organs and lower extremities

De bro oxyg rep ught enate len to db t ish he loo lun d O 2 gs to The Pulmonary Circuit Does? Ox y to h gena thr eart ted b oug to loo d hou istr d s t bo ibut e The Systemic d Circuit y e. O Does? Blue = deoxygenated Red = oxygenated 2

food, water intake oxygen intake Digestive System nutrients, water, salts The Circulatory System and Homeostasis Respiratory System oxygen elimination of carbon dioxide Circulatory System Urinary System water, solutes elimination of food residues Functional links between the circulatory rapid transport to system and other organ elimination of and from all living systems with major excess water, salts, cells roles in maintaining the wastes internal environment. Fig. 37 -12, p. 645

The Human Heart § A sac of connective tissue (pericardium) surrounds the heart muscle (myocardium) § Endothelium lines heart chambers and blood vessels § Heart valves keep blood moving in one direction • AV valves separate atria and ventricles • Semilunar valves separate ventricles and arteries

The Human Heart right lung left lung 1 B The heart is located between the lungs in the thoracic cavity. 2 ribs 1 – 8 3 4 5 6 7 pericardium 8 diaphragm Fig. 37 -13 b, p. 646

The Human Heart superior vena cava (flow from head, arms) arch of aorta trunk of pulmonary arteries (to lungs) right semilunar valve (shown closed) to pulmonary trunk left semilunar valve (closed) to aorta right pulmonary veins (from lungs) left pulmonary veins (from lungs) right atrium left atrium right AV valve (opened) = TRICUSPID VALVE left AV valve (opened) = MITRAL VAVLE right ventricle left ventricle (muscles that prevent valve from everting) endothelium and underlying connective tissue inferior vena cava (from trunk, legs) myocardium septum (partition between heart’s two halves) inner layer of pericardium heart’s apex Fig. 37 -13 a, p. 646

The Human Heart C Outer appearance. Pads of fat on the heart’s surface are normal. Fig. 37 -13 c, p. 646

The Cardiac Cycle § Cardiac cycle: Heart muscle alternates between diastole (relaxation) and systole (contraction) • • Blood collects in atria AV valves open, blood flows into ventricles Contraction of ventricles drives blood circulation Ventricles contract with a wringing motion from bottom to top

The Cardiac Cycle A Atria fill. Fluid pressure opens the AV valves, blood flows into the ventricles. B Next, atria contract. As fluid pressure rises in the ventricles, AV valves close. D Ventricles relax. Semilunar valves close as atria begin filling for the next cardiac cycle. C Ventricles contract. Semilunar valves open. Blood flows into aorta and pulmonary artery. Stepped Art Fig. 37 -14, p. 647

Cardiac Muscle § Cardiac muscle cells are striated (divided into sarcomeres) and have many mitochondria § Cells attach end to end at intercalated discs § Neighboring cells communicate through gap junctions that conduct waves of excitation

Cardiac Muscle Cells and Gap Junctions intercalated disk a branching cardiac muscle cell (part of one cardiac muscle fiber) b Part of a gap junction across the plasma membrane of a cardiac muscle cell. The junctions connect cytoplasm of adjoining cells and allow electrical signals that stimulate contraction to spread swiftly between them. Fig. 37 -15, p. 647

How the Heart Beats § Cardiac pacemaker (SA node) • A clump of noncontracting cells in the right atrium’s wall spontaneously fires action potentials about 70 times per minute § Cardiac conduction system • Signal spreads from SA node to AV node and junctional fibers in the septum, so heart contracts in a coordinated fashion

The Cardiac Conduction System SA node (cardiac pacemaker) AV node (the only point of electrical contact between atria and ventricles) junctional fibers branchings of junctional fibers (carry electrical signals through the ventricles) Fig. 37 -16, p. 647

The Human Heart and Two Flow Circuits § Fill in the blanks § The ______-chambered human heart pumps blood through _____ separate circuits of blood vessels § One circuit extends through _______, the other through _______ tissue only. § Both circuits loop back to the _____, which keeps blood flowing through the _______ circuits.

The Human Heart and Two Flow Circuits § The four-chambered human heart pumps blood through two separate circuits of blood vessels § One circuit extends through all body regions, the other through lung tissue only. § Both circuits loop back to the heart, which keeps blood flowing through the two circuits.

Part II § Pressure, Transport, and Flow Distribution

Major Blood Vessels of the Human Cardiovascular System Jugular Veins Superior Vena Cava Carotid Arteries Ascending Aorta Pulmonary Arteries Pulmonary Veins Coronary Arteries Hepatic Vein Brachial Artery Renal Vein Renal Artery Inferior Vena Cava Abdominal Aorta Iliac Veins Iliac Arteries Femoral Vein Femoral Artery Fig. 37 -11, p. 645

Pressure, Transport, and Flow Distribution § Contracting ventricles put pressure on the blood, forcing it through a series of vessels • • • Arteries carry blood from ventricles to arterioles Arterioles control blood distribution to capillaries Capillaries exchange substances Venules collect blood from capillaries Veins deliver blood back to heart

Human Blood Vessels outer coat smooth muscle basement membrane endothelium Artery elastic tissue Fig. 37 -17 a, p. 648

Human Blood Vessels outer coat smooth muscle rings basement over elastic tissue membrane endothelium Arteriole Fig. 37 -17 b, p. 648

Human Blood Vessels basement membrane endothelium Capillary (venules have a similar structure) Fig. 37 -17 c, p. 648

Human Blood Vessels outer coat smooth muscle, elastic fibers basement membrane endothelium Vein valve Fig. 37 -17 d, p. 648

Blood Pressure § Blood pressure • The pressure exerted by blood on the walls of blood vessels • Highest in arteries, then declines through circuit • Rate of blood flow depends on the difference in blood pressure between two points, and resistance to flow

arteries capillaries veins Blood Pressure in the Systolic Circuit: Plot of fluid pressure for a volume of blood as it flows through the systemic circuit. Systolic pressure occurs when ventricles contract, diastolic when ventricles are relaxed. arterioles venules Fig. 37 -18, p. 648

Blood Flow § Thick, elastic arteries smooth out variations in blood pressure during the cardiac cycle § Arterioles respond to signals from the autonomic and nervous systems, and to chemical signals, to direct blood flow to different parts of the body

100% Distribution of Cardiac Output in a Resting Person Figure It Out: What percentage of the brain’s blood supply arrives from the heart’s right half? Answer: None lungs heart’s right half liver digestive tract kidneys skeletal muscle brain skin bone cardiac muscle all other regions heart’s left half 6% 21% 20% 15% 13% 9% 5% 3% 8% Fig. 37 -19, p. 649

Controlling Blood Pressure § Blood pressure depends on total blood volume, how much blood the ventricles pump (cardiac output), and whether arterioles are constricted or dilated § Receptors in the aorta and carotid arteries monitor blood pressure and send signals to the medulla, which regulates cardiac output and arteriole diameter

Measuring Blood Pressure

Diffusion at Capillaries, Then Back to the Heart § Capillary • A cylinder of endothelial cells, one cell thick • Capillary beds are diffusion zones, where blood exchanges substances with interstitial fluid • Hydrostatic pressure moves materials out (ultrafiltration) • Osmotic pressure moves water in (capillary reabsorption)

Fluid Movement at a Capillary Bed blood to venule high pressure causes outward flow blood from arteriole Fluid movement at a capillary bed. Fluid crosses a capillary wall by way of ultrafiltration and reabsorption. (a) At the capillary’s arteriole end, a difference between blood pressure and interstitial fluid pressure forces out plasma, but few plasma proteins, through clefts between endothelial cells of the capillary wall. Ultrafiltration is the outward flow of fluid across the capillary wall as a result of hydrostatic pressure. (b) Reabsorption is the osmotic movement of some interstitial fluid into the capillary. It happens when the water concentration between interstitial fluid and the plasma differs. Plasma, with its dissolved proteins, has a greater solute concentration and therefore a lower water concentration. Reabsorption near the end of a capillary bed tends to balance ultrafiltration at the start of it. Normally, there is only a small net filtration of fluid, which vessels of the lymphatic system return to blood (Section 37. 10). cells of tissue inward-directed osmotic movement B A

Venous Pressure § Venules deliver blood from capillaries to veins § Veins deliver blood to the heart • Large-diameter, blood volume reservoirs • Valves help prevent backflow • Amount of blood in veins varies with activity level

Venous Valve Action Venous valve action. (a) Valves in medium-sized veins prevent the backflow of blood. Adjacent skeletal muscles helps raise fluid pressure inside a vein. (b) These muscles bulge into a vein as they contract. Pressure inside the vein rises and helps keeps blood flowing forward. (c) When muscles relax, the pressure that they exerted on the vein is lifted. Venous valves shut and cut off backflow. venous valve Fig. 37 -22 a, p. 651

blood flow to heart valve open valve closed

Key Concepts Blood Vessel Structure and Function § The heart pumps blood rhythmically, on its own § Adjustments at arterioles regulate how blood volume is distributed among tissues § Exchange of gases, wastes, and nutrients between the blood and tissues takes place at capillaries

Blood and Cardiovascular Disorders § Red blood cell disorders • Anemias, beta-thalassemias, polycythemia § White blood cell disorders • Infectious mononucleosis, leukemias, lymphomas § Clotting disorders • Hemophilia, thrombus, embolus

Blood and Cardiovascular Disorders § Atherosclerosis • Buildup of lipids in the arterial wall that narrows the lumen, may rupture and trigger heart attack

wall of artery, cross-section unobstructed lumen of a normal artery Fig. 37 -23 a, p. 652

atherosclerotic plaque blood clot sticking to plaque narrowed lumen Fig. 37 -23 b, p. 652

Clogged Coronary Arteries

coronary artery The photo shows coronary arteries and other blood vessels that service the heart. Resins were injected into them. Then the cardiac tissues were dissolved to make an accurate, three-dimensional corrosion cast. Fig. 37 -24 a, p. 653

The sketch shows two coronary bypasses (color-coded green), which extend from the aorta past two clogged parts of the coronary arteries. aorta coronary artery blockage location of a shunt made of a section taken from one of the patient’s other blood vessels Fig. 37 -24 b, p. 653

Blood and Cardiovascular Disorders § Hypertension – a silent killer • Chronic blood pressure above 140/90 § High blood pressure and atherosclerosis increase the risk of heart attack and stroke

one normal heartbeat Blood and Cardiovascular Disorders § Arrhythmias – abnormal heart rhythms • EKGs record electrical activity of cardiac cycle 0 0. 2 0. 4 0. 6 0. 8 a time (seconds) bradycardia (here, 46 beats per minute) b c tachycardia (here, 136 beats per minute) ventricular fibrillation d Fig. 37 -25, p. 653

Risk Factors § Cardiovascular disorders are the leading cause of death in the United States § Risk factors • Tobacco smoking, family history, hypertension, high cholesterol, diabetes mellitus, obesity, age, physical inactivity, gender

Key Concepts When the System Breaks Down § Cardiovascular problems include clogged blood vessels or abnormal heart rhythms § Some problems have a genetic basis; most are related to age or life-style