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Chapter 13. Blood, Heart and Circulation. 13-1. Chapter 13 Outline Overview Blood Pulmonary and Systemic Circulations Heart Valves Cardiac Cycle Electrical Activity of the Heart Structure of Blood Vessels Heart Disease Lymphatic System. 13-2. Overview. 13-3.

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Chapter 13

Chapter 13

Blood, Heart

and Circulation

13-1


Chapter 13

Chapter 13 Outline

  • Overview

  • Blood

  • Pulmonary and Systemic Circulations

  • Heart Valves

  • Cardiac Cycle

  • Electrical Activity of the Heart

  • Structure of Blood Vessels

  • Heart Disease

  • Lymphatic System

13-2


Overview

Overview

13-3


Functions of circulatory system

Functions of Circulatory System

  • Plays roles in transportation of respiratory gases, delivery of nutrients and hormones, and waste removal

    • And in temperature regulation, clotting, and immune function

13-4


Components of circulatory system

Components of Circulatory System

  • Include cardiovascular and lymphaticsystems

    • Heart pumps blood thru cardiovascular system

    • Blood vessels carry blood from heart to cells and back

      • Includes arteries, arterioles, capillaries, venules, veins

  • Lymphatic system picks up excess fluid filtered out in capillary beds and returns it to veins

    • Its lymph nodes are part of immune system

13-5


Blood

Blood

13-6


Composition of blood

Composition of Blood

  • Consists of formed elements (cells) suspended and carried in plasma (fluid part)

  • When centrifuged, blood separates into heavier formed elements on bottom and plasma on top

13-7


Composition of blood1

Composition of Blood

  • Total blood volume is about 5L

  • Plasma is straw-colored liquid consisting of H2O and dissolved solutes

    • Includes ions, metabolites, hormones, antibodies

  • Red blood cells (RBCs) comprise most of formed elements

    • % of RBCs in centrifuged blood sample = hematocrit

      • Hematocrit is 36-46% in women; 41-53% in men

13-8


Plasma proteins

Plasma Proteins

  • Constitute 7-9% of plasma

  • 3 types of plasma proteins: albumins, globulins, and fibrinogen

    • Albumin accounts for 60-80%

      • Creates colloid osmotic pressure that draws H2O from interstitial fluid into capillaries to maintain blood volume and pressure

  • Globulins carry lipids

    • Gamma globulins are antibodies

  • Fibrinogen serves as clotting factor

    • Converted to fibrin

    • Serum is fluid left when blood clots

13-9


Formed elements

Formed Elements

  • Are erythrocytes (RBCs) and leukocytes (WBCs)

  • RBCs are flattened biconcave discs

    • Shape provides increased surface area for diffusion

    • Lack nuclei and mitochondria

    • Each RBC contains 280 million hemoglobins

    • About 300 billion RBCs are produced each day

13-10


Leukocytes

Leukocytes

  • Have a nucleus, mitochondria, and amoeboid ability

  • Can squeeze through capillary walls (diapedesis)

    • Granular leukocytes help detoxify foreign substances and release heparin

      • Include eosinophils, basophils, and neutrophils

13-11


Leukocytes continued

Leukocytes continued

  • Agranular leukocytes are phagocytic and produce antibodies

    • Include lymphocytes and monocytes

13-12


Platelets thrombocytes

Platelets (thrombocytes)

  • Are smallest of formed elements, lack nucleus

  • Are amoeboid fragments of megakaryocytes from bone marrow

  • Constitute most of mass of blood clots

  • Release serotonin to vasoconstrict and reduce blood flow to clot area

  • Secrete growth factors to maintain integrity of blood vessel wall

  • Survive 5-9 days

13-13


Hematopoiesis

Hematopoiesis

  • Is formation of blood cells from stem cells in bone marrow (myeloid tissue) and lymphoid tissue

    • Marrow produces about 500 billion blood cells/day

    • In fetus occurs in liver

13-14


Hematopoiesis continued

Hematopoiesis continued

  • Erythropoiesis is formation of RBCs

    • Stimulated by erythropoietin (EPO) from kidney

  • Leukopoiesis is formation of WBCs

    • Stimulated by variety of cytokines

      • = autocrine regulators secreted by immune system

13-15


Erythropoiesis

Erythropoiesis

  • 2.5 million RBCs are produced/sec

  • Lifespan of 120 days

  • Old RBCs removed from blood by phagocytic cells in liver, spleen, and bone marrow

    • Iron recycled back into hemoglobin production

13-16


Rbc antigens and blood typing

RBC Antigens and Blood Typing

  • Antigens present on RBC surface specify blood type

  • Major antigen group is ABOsystem

    • Type A blood has only A antigens

    • Type B has only B antigens

    • Type AB has both A and B antigens

    • Type O has neither A or B antigens

13-17


Transfusion reactions

Transfusion Reactions

  • People with Type A blood make antibodies to Type B RBCs, but not to Type A

  • Type B blood has antibodies to Type A RBCs but not to Type B

  • Type AB blood doesn’t have antibodies to A or B

  • Type O has antibodies to both Type A and B

  • If different blood types are mixed, antibodies will cause mixture to agglutinate

13-18


Transfusion reactions continued

Transfusion Reactions continued

  • If blood types don't match, recipient’s antibodies agglutinate donor’s RBCs

  • Type O is “universal donor” because lacks A and B antigens

    • Recipient’s antibodies won’t agglutinate donor’s Type O RBCs

  • Type AB is “universal recipient” because doesn’t make anti-A or anti-B antibodies

    • Won’t agglutinate donor’s RBCs

13-19


Rh factor

Rh Factor

  • Is another type of antigen found on RBCs

  • Rh+ has Rho(D) antigens; Rh- does not

  • Can cause problems when Rh- mother has Rh+ babies

    • At birth, mother may be exposed to Rh+ blood of fetus

    • In later pregnancies mom may produce Rh antibodies

      • In Erythroblastosis fetalis, this happens and antibodies cross placenta causing hemolysis of fetal RBCs

13-20


Hemostasis

Hemostasis

  • Is cessation of bleeding

  • Promoted by reactions initiated by vessel injury:

    • Vasoconstriction restricts blood flow to area

    • Platelet plug forms

      • Plug and surroundings are infiltrated by web of fibrin, forming clot

13-21


Role of platelets

Role of Platelets

  • Platelets don't stick to intact endothelium because of presence of prostacyclin (PGI2--a prostaglandin) and NO

    • Keep clots from forming and are vasodilators

13-22


Role of platelets1

Role of Platelets

  • Damage to endothelium allows platelets to bind to exposed collagen

    • von Willebrand factor increases bond by binding to both collagen and platelets

    • Platelets stick to collagen and release ADP, serotonin, and thromboxane A2

      • = platelet release reaction

13-23


Role of platelets continued

Role of Platelets continued

  • Serotonin and thromboxane A2 stimulate vasoconstriction, reducing blood flow to wound

  • ADP and thromboxane A2 cause other platelets to become sticky and attach and undergo platelet release reaction

    • This continues until platelet plug is formed

13-24


Role of fibrin

Role of Fibrin

  • Platelet plug becomes infiltrated by meshwork of fibrin

  • Clot now contains platelets, fibrin and trapped RBCs

    • Platelet plug undergoes plug contraction to form more compact plug

13-25


Conversion of fibrinogen to fibrin

Conversion of Fibrinogen to Fibrin

  • Can occur via 2 pathways:

    • Intrinsic pathway clots damaged vessels and blood left in test tube

      • Initiated by exposure of blood to negatively charged surface of glass or blood vessel collagen

        • This activates factor XII (a protease) which initiates a series of clotting factors

        • Ca2+ and phospholipids convert prothrombin to thrombin

          • Thrombin converts fibrinogen to fibrin which polymerizes to form a mesh

    • Damage outside blood vessels releases tissuethromboplastin that triggers a clotting shortcut (= extrinsic pathway)

13-26


Chapter 13

13-27


Chapter 13

13-28


Dissolution of clots

Dissolution of Clots

  • When damage is repaired, activated factor XII causes activation of kallikrein

    • Kallikrein converts plasminogen to plasmin

      • Plasmin digests fibrin, dissolving clot

13-29


Anticoagulants

Anticoagulants

  • Clotting can be prevented by Ca+2 chelators (e.g. sodium citrate or EDTA)

    • or heparin which activates antithrombin III (blocks thrombin)

  • Coumarin blocks clotting by inhibiting activation of Vit K

    • Vit K works indirectly by reducing Ca+2 availability

13-30


Pulmonary and systemic circulations

Pulmonary and Systemic Circulations

13-31


Structure of heart

Structure of Heart

  • Heart has 4 chambers

    • 2 atria receive blood from venous system

    • 2 ventricles pump blood to arteries

    • 2 sides of heart are 2 pumps separated by muscular septum

13-32


Structure of heart continued

Structure of Heart continued

  • Between atria and ventricles is layer of dense connective tissue called fibrous skeleton

    • Which structurally and functionally separates the two

      • Myocardial cells of atria attach to top of fibrous skeleton and form 1 unit (or myocardium)

      • Cells from ventricles attach to bottom and form another unit

    • Fibrous skeleton also forms rings, the annuli fibrosi, to hold heart valves

13-33


Pulmonary and systemic circulations1

Pulmonary and Systemic Circulations

  • Blood coming from tissues enters superior and inferior vena cavae which empties into right atrium, then goes to right ventricle which pumps it through pulmonary arteries to lungs

13-34


Pulmonary and systemic circulations continued

Pulmonary and Systemic Circulations continued

  • Oxygenated blood from lungs passes thru pulmonary veins to left atrium, then to left ventricle which pumps it through aorta to body

13-35


Pulmonary and systemic circulations continued1

Pulmonary and Systemic Circulations continued

  • Pulmonary circulation is path of blood from right ventricle through lungs and back to heart

  • Systemic circulation is path of blood from left ventricle to body and back to heart

  • Rate of flow through systemic circulation = flow rate thru pulmonary circuit

13-36


Pulmonary and systemic circulations continued2

Pulmonary and Systemic Circulations continued

  • Resistance in systemic circuit > pulmonary

    • Work done by left ventricle pumping to systemic is 5-7X greater

      • Makes left ventricle more muscular (and 3-4X thicker)

13-37


Heart valves

Heart Valves

13-38


Atrioventricular valves

Atrioventricular Valves

  • Blood flows from atria into ventricles thru 1-way atrioventricular (AV) valves

    • Between right atrium and ventricle is tricuspid valve

    • Between left atrium and ventricle is bicuspid or mitral valve

13-39


Atrioventricular valves continued

Atrioventricular Valves continued

  • Opening and closing of valves results from pressure differences

    • High pressure of ventricular contraction is prevented from everting AV valves by contraction of papillary muscles which are connected to AVs by chorda tendinea

13-40


Semilunar valves

Semilunar Valves

  • During ventricular contraction blood is pumped through aortic and pulmonary semilunar valves

    • Close during relaxation

13-41


Cardiac cycle

Cardiac Cycle

13-42


Cardiac cycle1

Cardiac Cycle

  • Is repeating pattern of contraction and relaxation of heart

    • Systole refers to contraction phase

    • Diastole refers to relaxation phase

    • Both atria contract simultaneously; ventricles follow 0.1-0.2 sec later

13-43


Cardiac cycle2

Cardiac Cycle

  • End-diastolic volume is volume of blood in ventricles at end of diastole

  • Stroke volume is amount of blood ejected from ventricles during systole

  • End-systolic volume is amount of blood left in ventricles at end of systole

13-44


Cardiac cycle continued

Cardiac Cycle continued

  • As ventricles contract, pressure rises, closing AV valves

    • Called isovolumetric contraction because all valves are closed

  • When pressure in ventricles exceeds that in aorta, semilunar valves open and ejection begins

  • As pressure in ventricle falls below that in aorta, back pressure closes semilunars

  • All valves are closed and ventricles undergo isovolumetricrelaxation

  • When pressure in ventricles falls below atria, AVs open and ventricles fill

  • Atrial systole sends its blood into ventricles

13-45


Chapter 13

13-46


Heart sounds

Heart Sounds

  • Closing of AV and semilunar valves produces sounds that can be heard thru stethoscope

    • Lub (1st sound) produced by closing of AV valves

    • Dub (2nd sound) produced by closing of semilunars

13-47


Heart murmurs

Heart Murmurs

  • Are abnormal sounds produced by abnormal patterns of blood flow in heart

  • Many caused by defective heart valves

    • Can be of congenital origin

    • In rheumatic fever, damage can be from antibodies made in response to strep infection

13-48


Heart murmurs continued

Heart Murmurs continued

  • In mitral stenosis, mitral valve becomes thickened and calcified, impairing blood flow from left atrium to left ventricle

    • Accumulation of blood in left ventricle can cause pulmonary hypertension

  • Valves are incompetent when don't close properly

    • Can be from damage to papillary muscles

13-49


Heart murmurs continued1

Heart Murmurs continued

  • Murmurs caused by septal defects are usually congenital

    • Due to holes in septum between left and right sides of heart

    • Pressure causes blood to pass from left to right

13-50


Electrical activity of heart

Electrical Activity of Heart

13-51


Electrical activity of heart1

Electrical Activity of Heart

  • Myocardial cells are short, branched, and interconnected by gap junctions

  • Entire muscle that forms a chamber is called a myocardium or functional syncytium

    • Because APs originating in any cell are transmitted to all others

    • Chambers separated by nonconductive tissue

13-52


Sa node pacemaker

SA Node Pacemaker

  • In normal heart, SA node functions as pacemaker

    • Depolarizes spontaneously to threshold (= pacemaker potential)

13-53


Sa node pacemaker continued

SA Node Pacemaker continued

  • Membrane voltage begins at -60mV and gradually depolarizes to -40 threshold

  • Spontaneous depolarization is caused by Na+ flowing through channel that opens when hyperpolarized (HCN channel)

  • At threshold V-gated Ca2+ channels open, creating upstroke and contraction

  • Repolarization is via opening of V-gated K+ channels

13-54


Ectopic pacemakers

Ectopic Pacemakers

  • Other tissues in heart are spontaneously active

    • But are slower than SA node

    • Are stimulated to produce APs by SA node before spontaneously depolarize to threshold

    • If APs from SA node are prevented from reaching these, they will generate pacemaker potentials

13-55


Myocardial aps

Myocardial APs

  • Myocardial cells have RMP of –90 mV

  • Depolarized to threshold by APs originating in SA node

13-56


Myocardial aps continued

Myocardial APs continued

  • Upstroke occurs as V-gated Na+ channels open

  • MP rapidly declines to 15mV and stays there for 200-300 msec (plateau phase)

    • Plateau results from balance between slow Ca2+ influx and K+ efflux

  • Repolarization due to opening of extra K+ channels

13-57


Conducting tissues of heart

Conducting Tissues of Heart

  • APs from SA node spread through atrial myocardium via gap junctions

  • But need special pathway to ventricles because of non-conducting fibrous tissue

    • AV node at base of right atrium and bundle of His conduct APs to ventricles

Insert Fig 13.20

13-58


Conducting tissues of heart continued

Conducting Tissues of Heart continued

  • In septum of ventricles, His divides into right and left bundle branches

    • Which give rise to Purkinje fibers in walls of ventricles

      • These stimulate contraction of ventricles

13-59


Conduction of aps

Conduction of APs

  • APs from SA node spread at rate of 0.8 -1 m/sec

  • Time delay occurs as APs pass through AV node

    • Has slow conduction of 0.03– 0.05 m/sec

  • AP speed increases in Purkinje fibers to 5 m/sec

    • Ventricular contraction begins 0.1–0.2 sec after contraction of atria

13-60


Excitation contraction coupling

Excitation-Contraction Coupling

  • Depolarization of myocardial cells opens V-gated Ca2+ channels in sarcolemma

    • This depolarization opens V-gated and Ca2+ release channels in SR (calcium-induced-calcium-release)

    • Ca2+ binds to troponin and stimulates contraction (as in skeletal muscle)

    • During repolarization Ca2+ pumped out of cell and into SR

13-61


Refractory periods

Refractory Periods

  • Heart contracts as syncytium and thus cannot sustain force

  • Its AP lasts about 250 msec

  • Has a refractory period almost as long as AP

  • Cannot be stimulated to contract again until has relaxed

13-62


Electrocardiogram ecg ekg

Electrocardiogram (ECG/EKG)

  • Is a recording of electrical activity of heart conducted thru ions in body to surface

13-63


Types of ecg recordings

Types of ECG Recordings

  • Bipolar leads record voltage between electrodes placed on wrists and legs (right leg is ground)

  • Lead I records between right arm and left arm

  • Lead II: right arm and left leg

  • Lead III: left arm and left leg

13-64


Types of ecg recordings continued

Types of ECG Recordings continued

  • Unipolar leads record voltage between a single electrode placed on body and ground built into ECG machine

    • Limb leads go on right arm (AVR), left arm (AVL), and left leg (AVF)

    • The 6 chest leads, placed as shown, allow certain abnormalities to be detected

13-65


Chapter 13

ECG

  • 3 distinct waves are produced during cardiac cycle

  • P wave caused by atrial depolarization

13-66


Chapter 13

ECG

  • QRS complex is caused by ventricular depolarization

  • T wave results from ventricular repolarization

13-67


Correlation of ecg with heart sounds

Correlation of ECG with Heart Sounds

  • 1st heart sound (lub) comes immediately after QRS wave as AV valves close

  • 2nd heart sound (dub) comes as T wave begins and semilunar valves close

13-68


Structure of blood vessels

Structure of Blood Vessels

13-69


Structure of blood vessels1

Structure of Blood Vessels

  • Innermost layer of all vessels is the endothelium

  • Capillaries are made of only endothelial cells

  • Arteries and veins have 3 layers called tunicaexterna, media, and interna

    • Externa is connective tissue

    • Media is mostly smooth muscle

    • Interna is made of endothelium, basement membrane, and elastin

  • Although have same basic elements, arteries and veins are quite different

13-70


Chapter 13

13-71


Arteries

Arteries

  • Large arteries are muscular and elastic

    • Contain lots of elastin

    • Expand during systole and recoil during diastole

      • Helps maintain smooth blood flow during diastole

13-72


Arteries1

Arteries

  • Small arteries and arterioles are muscular

    • Provide most resistance in circulatory system

    • Arterioles cause greatest pressure drop

      • Mostly connect to capillary beds

      • Some connect directly to veins to form arteriovenous anastomoses

13-73


Capillaries

Capillaries

  • Provide extensive surface area for exchange

  • Blood flow through a capillary bed is determined by state of precapillary sphincters of arteriole supplying it

13-74


Types of capillaries

Types of Capillaries

  • In continuous capillaries, endothelial cells are tightly joined together

    • Have narrow intercellular channels that permit exchange of molecules smaller than proteins

    • Present in muscle, lungs, adipose tissue

  • Fenestrated capillaries have wide intercellular pores

    • Very permeable

    • Present in kidneys, endocrine glands, intestines.

  • Discontinuous capillaries have large gaps in endothelium

    • Are large and leaky

    • Present in liver, spleen, bone marrow

13-75


Veins

Veins

  • Contain majority of blood in circulatory system

  • Very compliant (expand readily)

  • Contain very low pressure (about 2mm Hg)

    • Insufficient to return blood to heart

13-76


Veins1

Veins

  • Blood is moved toward heart by contraction of surrounding skeletal muscles (skeletal muscle pump)

    • And pressure drops in chest during breathing

    • 1-way venous valves ensure blood moves only toward heart

13-77


Heart disease

Heart Disease

13-78


Atherosclerosis

Atherosclerosis

  • Is most common form of arteriosclerosis (hardening of arteries)

    • Accounts for 50% of deaths in US

  • Localized plaques (atheromas) reduce flow in an artery

    • And act as sites for thrombus (blood clots)

13-79


Atherosclerosis1

Atherosclerosis

  • Plaques begin at sites of damage to endothelium

    • E.g. from hypertension, smoking, high cholesterol, or diabetes

13-80


Atherosclerosis2

Atherosclerosis

  • Plaques begin at sites of damage to endothelium

    • E.g. from hypertension, smoking, high cholesterol, or diabetes

13-81


Cholesterol and plasma lipoproteins

Cholesterol and Plasma Lipoproteins

  • High blood cholesterol is associated with risk of atherosclerosis

  • Lipids, including cholesterol, are carried in blood attached to LDLs (low-density lipoproteins) and HDLs (high-density lipoproteins)

13-82


Cholesterol and plasma lipoproteins1

Cholesterol and Plasma Lipoproteins

  • LDLs and HDLs are produced in liver and taken into cells by receptor-mediated endocytosis

    • In cells LDL is oxidized

      • Oxidized LDL can injure endothelial cells facilitating plaque formation

    • Arteries have receptors for LDL but not HDL

      • Which is why HDL isn't atherosclerotic

13-83


Ischemic heart disease

Ischemic Heart Disease

  • Is most commonly due to atherosclerosis in coronary arteries

  • Ischemia occurs when blood supply to tissue is deficient

    • Causes increased lactic acid from anaerobic metabolism

  • Often accompanied by angina pectoris (chest pain)

13-84


Ischemic heart disease continued

Ischemic Heart Disease continued

  • Detectable by changes in S-T segment of ECG

13-85


Ischemic heart disease continued1

Ischemic Heart Disease continued

  • Myocardial infarction (MI) is a heart attack

    • Usually caused by occlusion of a coronary artery

      • Causing heart muscle to die

      • Diagnosed by high levels of creatine phosphokinase (CPK) and lactate dehydrogenase (LDH)

        • And presence of plasma troponin T and I from damaged muscle

      • Dead cells are replaced by noncontractile scar tissue

13-86


Arrhythmias detected on ecg

Arrhythmias Detected on ECG

  • Arrhythmias are abnormal heart rhythms

  • Heart rate <60/min is bradycardia; >100/min is tachycardia

13-87


Arrhythmias detected on ecg continued

Arrhythmias Detected on ECG continued

  • In flutter, contraction rates can be 200-300/min

  • In fibrillation, contraction of myocardial cells is uncoordinated and pumping ineffective

    • Ventricular fibrillation is life-threatening

      • Electrical defibrillation resynchronizes heart by depolarizing all cells at same time

13-88


Arrhythmias detected on ecg continued1

Arrhythmias Detected on ECG continued

  • AV node block occurs when node is damaged

  • First–degree AV node block is when conduction through AV node > 0.2 sec

    • Causes long P-R interval

  • Second-degree AV node block is when only 1 out of 2-4 atrial APs can pass to ventricles

    • Causes P waves with no QRS

  • In third-degree or complete AV node block no atrial activity passes to ventricles

    • Ventricles are driven slowly by bundle of His or Purkinjes

13-89


Arrhythmias detected on ecg continued2

Arrhythmias Detected on ECG continued

  • In third-degree or complete AV node block, no atrial activity passes to ventricles

    • Ventricles are driven slowly by bundle of His or Purkinjes

13-92


Lymphatic system

Lymphatic System

13-93


Lymphatic system1

Lymphatic System

  • Has 3 basic functions:

    • Transports interstitial fluid (lymph) back to blood

    • Transports absorbed fat from small intestine to blood

    • Helps provide immunological defenses against pathogens

13-94


Lymphatic system continued

Lymphatic System continued

  • Lymphatic capillaries are closed-end tubes that form vast networks in intercellular spaces

    • Very porous, absorb proteins, microorganisms, fat

13-95


Lymphatic system continued1

Lymphatic System continued

  • Lymph is carried from lymph capillaries to lymph ducts to lymph nodes

13-96


Lymphatic system continued2

Lymphatic System continued

  • Lymph nodes filter lymph before returning it to veins via thoracic duct or right lymphatic duct

  • Nodes make lymphocytes and contain phagocytic cells that remove pathogens

  • Lymphocytes also made in tonsils, spleen, thymus

13-97


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