Exam 2 Flashcards
pulmonary circulation
right side of heart carries blood to lungs and returns blood to left side of heart
systemic circulation
left side of heart pumps blood to remaining tissues of body. CO2 and other waste products are carried back to right side of heart
Shape of heart
Similar to a blunt cone; Blunt, rounded point of heart is apex; Larger, flat part at superior end of heart is base
Size of heart
approximately the size of a closed fist; 250g in females and 300g in males
Location of heart
Mediastinum; Midline partition of thoracic cavity that also contains trachea, esophagus, thymus, and associated structures
Importance of knowing heart’s location
1) Positioning of stethoscope to hear heart sounds and positioning electrodes to record an electrocardiogram from chest
2) Effective CPR
CPR
Cardiopulmonary resuscitation; Depends on knowledge of position of heart; An emergency procedure that maintains blood flow in the body if a person’s heart stops; Consists of firm and rhythmic compression of chest combined with artificial ventilation of lungs
Structure of pericardium
Double-layered, closed sac that surrounds the heart. Consists of two layers:
1) Outer fibrous pericardium: tough, fibrous connective tissue layer that prevents overdistension of heart and anchors it within the mediastinum. Superiorly, the fibrous pericardium is continuous with the connective tissue coverings of the great vessels, such as the aorta, and inferiorly it is attached to the surface of the diaphragm
2) Inner serous pericardium: Layer of simple squamous epithelium
Structure of serous pericardium
Continuous with each other where great vessels enter or leave heart. There is a space between two layers called pericardial cavity
Divided further into two parts:
1) Parietal pericardium: Part that lines the fibrous pericardium
2) Visceral pericardium: Part that covers the heart surface; Also known as epicardium when describing region in context of heart wall
Space between serous pericardium layers
Pericardial cavity; Filled with thin layer of serous pericardial fluid; Fluid helps reduce friction as the heart moves within the pericardial sac; Can increase in volume to hold a significant volume of pericardial fluid
Outer layer of heart wall
Epicardium; Superficial layer of heart wall; A thin serous membrane that constitutes the smooth, outer surface of the heart; Acts as protective layer and helps in proper development of cardiac cells
Middle layer of heart wall
Myocardium; Thick, middle layer of heart; Composed of cardiac muscle tissue and is responsible for the heart’s ability to contract
Inner layer of heart wall
Endocardium; Deep to myocardium; Consists of simple squamous epithelium over a layer of connective tissue; Forms the smooth, inner surface of the heart chambers, which allows blood to move easily through the heart; Also covers the surfaces of the heart valves
Vena cava
Superior and inferior vena cava carry blood from the body to the right atrium; Veins
Pulmonary veins
Four pulmonary veins carry blood from the lungs to the left atrium; Veins
Pulmonary trunk
Carries blood from the right ventricle to the lungs; Great artery
Aorta
Carries blood from the left ventricle to the body; Great artery
Coronary sulcus
Runs obliquely around the heart, separating atria from ventricles
Anterior interventricular sulcus
Extend inferiorly from coronary sulcus, indicating the division between right and left ventricles; On anterior surface of heart, extending from coronary sulcus towards apex of heart
Posterior interventricular sulcus
Extend inferiorly from coronary sulcus, indicating the division between right and left ventricles; On posterior surface of heart, extending from coronary sulcus towards apex of heart
Coronary arteries
Left and right coronary arteries exit the aorta just above the point where the aorta leaves the heart; Lie within the coronary sulcus; Right coronary artery is usually smaller in diameter than the left one, and it does not carry as much blood as the left coronary artery
Left coronary artery
3 major branches:
1) Anterior interventricular artery: Supplies blood to most of the anterior part of heart
2) Left marginal artery: Supplies blood to lateral wall of left ventricle
3) Circumflex artery: Supplies blood to posterior wall of heart
Right coronary artery
Lies within coronary sulcus and extends from aorta around to the posterior part of the heart
2 major branches:
1) Right marginal artery: Supplies blood to lateral wall of right ventricle
2) Posterior interventricular artery: Supplies blood to posterior and inferior part of heart
Cardiac veins
2 major veins draining the blood from heart wall tissue:
1) Great cardiac vein: Drains blood from left side of heart
2) Small cardiac vein: Drains right margin of heart
Both veins empty into coronary sinus
Coronary sinus
Cardiac veins converge toward posterior part of coronary sulcus and empty into large venous cavity, or coronary sinus, which in turn empties into right atrium
Right atrium
3 main openings:
1) Opening from superior vena cava: Receives blood from body
2) Opening from inferior vena cava: Receives blood from body
3) Opening from coronary sinus: receives blood from heart
Left atrium
Four relatively uniform openings from the four pulmonary veins that receive blood from lungs
Interatrial septum
Wall of tissue that separates right and left atria from each other
Atrioventricular canals
Atria open into ventricles through atrioventricular canals
Right ventricle
Blood flows from right ventricle into pulmonary trunk
Left ventricle
Blood flows from left ventricle into aorta; Wall is thicker than wall of right ventricle, allowing for stronger contractions to pump blood through systemic circulation
Interventricular septum
Separates left and right ventricles from one another with a thick, muscular part toward apex and a thin, membranous part toward atria
Atrioventricular valve
Located in each atrioventricular canal and composed of cusps, or flaps; Ensures one-way flow of blood from atria into ventricles, preventing blood from flowing back into atria
Chordae tendinae and papillary muscles
Tricuspid valve
Atrioventricular valve between right atrium and right ventricle; Consists of three cusps
Bicuspid valve
Atrioventricular valve between left atrium and left ventricle; Consists of two cusps; Also known as mitral valve
Semilunar valve
Positioned between each ventricle and its associated great artery; Includes aortic semilunar valve and pulmonary semilunar valve; Each valve consists of three pocketlike semilunar cusps, the free inner borders of which meet in the center of the artery to block blood flow. Contraction of ventricles pushes blood against semilunar valves, forcing them to open, and blood can then enter the great arteries. However, when blood flows back from aorta and pulmonary trunk toward ventricles, it enters the pockets of the cusps, causing the cusps to meet in the center of the aorta or pulmonary trunk. This closes the semilunar valves and prevents blood from flowing back into ventricles
Heart skeleton
Consists of a plate of fibrous connective tissue between atria and ventricles. Connective tissue plate forms fibrous rings around the atrioventricular and semilunar valves and provides solid support for them, reinforcing the valve openings. Fibrous connective tissue plate also serves as electrical insulation between the atria and the ventricles and provides a rigid site for attachment of cardiac muscles
Cardiac muscle cell
Elongated, branching cells that have one, or occasionally two, centrally located nuclei. Contain actin and myosin myofilaments organized to form sarcomeres, which join end-to-end to form myofibrils. These myofilaments are responsible for cardiac muscle contraction, and their organization gives cardiac muscle a striated appearance. The striations are less regularly arranged and less numerous than in skeletal muscle
Cardiac muscle cell vs Skeletal muscle cell
Cardiac:
1) Less regularly arranged and less numerous striations
2) Onset of contraction is longer and prolonged in cardiac muscle
3) Cardiac muscle requires some calcium from extracellular fluid and from T tubules
4) Rich in mitochondria because cannot develop large oxygen deficit
5) Organized in spiral bundles or sheets
6) Bound to adjacent cells by specialized cell-to-cell contacts called intercalated disks
Skeletal:
1) Regularly arranged sarcoplasmic reticulum and has dilated cisternae
2) Calcium for contraction is stored in sarcoplasmic reticulum
Both:
1) Actin and myosin myofilaments are responsible for cardiac muscle contraction, and their organization gives cardiac muscle a striated appearance
2) Both muscles have T-tubules that are in close association with sarcoplasmic reticulum
Conducting system of heart
Relays action potentials through heart; System consists of modified cardiac muscle cells that form two nodes and a conducting bundle; 2 nodes are contained within walls of right atrium:
1) Sinoatrial node
2) Atrioventricular node
SA node -> AV node -> Bundle of His -> Bundle branches -> Purkinje fibers
Sinoatrial node
Medial to the opening of superior vena cava; Cells of SA node spontaneously generate action potentials at a grater frequency than other cardiac muscle cells, these cells are called the pacemaker of the heart; SA node is made up of specialized, small-diameter muscle cells that merge with the other cardiac muscle cells of the right atrium; Activity of SA node that causes heart to contract spontaneously and rhythmically
Atrioventricular node
Medial to the right atrioventricular valve; Gives rise to a conducting bundle of the heart, the atrioventricular bundle
Atrioventricular bundle
Bundle of His; Passes through a small opening in the fibrous skeleton to reach the interventricular septum, where it divides to form the right and left bundle branches
Bundle branches
Emerge from bundle of His; Extend beneath the endocardium on each side of the interventricular septum to the apex of both the right and left ventricles
Purkinje fibers
Inferior terminal branches of the bundles; Fibers are large-diameter cardiac muscle fibers; Have fewer myofibrils than most cardiac muscle cells and do not contract as forcefully; Intercalated disks are well developed between Purkinje fibers and contain numerous gap junctions; These structural modifications allow action potentials to travel along Purkinje fibers much more rapidly than through other cardiac muscle tissue
Autorhythmic
Heart is autorhythmic because it stimulates itself to contract at regular intervals; If removed from body and maintained under physiological conditions with proper nutrients and temperature, it will continue to beat autorhythmically for a long time
Pacemaker potential
A spontaneously developing local potential that reaches threshold that leads to action potentials to be generated in SA node/ Changes in ion movement into and out of pacemaker cells cause pacemaker potential
Authorhythmicity vs pacemaker potential
In SA node, pacemaker cells generate action potentials spontaneously and at regular intervals through autorhythmicity. When pacemaker potential reaches threshold, then action potentials are generated in SA node
Action potentials in cardiac muscle cells
Cardiac muscle exhibit depolarization followed by repolarization of resting membrane potential; Alterations in membrane channels are responsible for the changes in the permeability of plasma membrane that produce action potentials; Action potentials in cardiac muscle last longer than those in skeletal muscle, and membrane channels differ somewhat from those in skeletal muscle
Refactory period of cardiac muscle
Plateau phase of action potential in cardiac muscle delays repolarization to resting membrane potential, the refactory period is prolonged. Long refactory period ensures contraction and most of relaxation are completed before another action potential can be initiated. This prevents tetanic contractions and cardiac muscle and is responsible for rhythmic contractions
Refactory period is divided into two:
1) Absolute refactory period: A muscle cell is completely insensitive to further stimulation
2) Relative refactory period: Cell is sensitive to stimulation, but a greater stimulation than normal is required to cause action potential
Electrocardiogram (ECG)
Summated record of cardiac action potentials detected with electrodes placed on the body surface
P wave
Result of action potentials that cause depolarization of atrial myocardium. These action potentials result in atrial contraction
QRS complex
Composed of three individual waves - Q, R, and S waves - and results from ventricular depolarization, which stimulates ventricular contraction
Wave representing repolarization of atria cannot be seen because it occurs during QRS complex
T wave
Represents repolarization of ventricles and precedes ventricular relaxation
PQ interval
Q wave is very small, so more commonly called PR interval. Interval lasts approximately 0.16 second, during which time the atria contract and begin to relax. At end of PR interval, ventricles begin to depolarize
QT interval
Extends from beginning of QRS complex to end of T wave. Lasts about 0.36 second and represents the approximate length of time required for ventricles to completed contraction and start to relax
Cardiac cycle
The repetitive pumping process that begins with the onset of cardiac muscle contraction and ends with the beginning of the next contraction; Both atrial primer pumps complete the filling of ventricles with blood, and both ventricular power pumps produce major force that causes blood to flow through pulmonary and systemic arteries
1) Heart relaxed: Passive ventricular filling
2) Atrial systole: Active ventricular filling
3) Ventricular systole: Period of isovolumetric contraction
4) Ventricular systole: Period of ejection
5) Ventricular diastole: Period of isovolumetric relaxation
Cardiac cycle and contraction
Cardiac cycle involves predictable pattern of contraction and relaxation of heart chambers
1) Heart relaxed
2) Atrial systole: SA node stimulates atrial contraction
3) Ventricular systole: Action potential passes through heart, stimulating ventricle contraction
4) Ventricular systole: Ventricular contraction continues
5) Ventricular diastole: Ventricles relax
Cardiac cycle and valve movement
Beginning of cardiac cycle, atria and ventricles and relaxed, AV valves are open, and semilunar valves are closed.
1) Heart relaxed: AV valves are open and semilunar valves stay closed
2) Atrial systole:
3) Ventricular systole: AV valves close
4) Ventricular systole: Semilunar valves are pushed open
5) Ventricular diastole: Semilunar valves close
Cardiac cycle and pressure of chambers
Blood moves from area of higher pressure to an area of lower pressure. Pressure changes produced within the heart chambers as a result of cardiac muscle contraction and relaxation move blood along pulmonary and systemic circulations
1) Heart relaxed: Greater blood pressure in veins than in heart chambers. Atrial pressure slightly greater than ventricular pressure
2) Atrial systole
3) Ventricular systole: As ventricles contract, ventricular pressures increase
4) Ventricular systole: Ventricular pressure builds until it overcomes pressures in pulmonary trunk and aorta
5) Ventricular diastole: Ventricles relax, so ventricular pressures decrease below pressures in pulmonary trunk and aorta
Cardiac cycle and heart sounds
First heart sound is low-pitched “lub.” It occurs at beginning of ventricular systole and is caused by vibration of atrioventricular valves and surrounding fluid as valves close.
Second heart sound is high-pitched “dup.” Occurs at beginning of ventricular diastole and results from closure of aortic and pulmonary semilunar valves
Systole is time between first and second heart sounds. Diastole is time between second heart sound and next first heart sound
Cardiac cycle and ECG
1) Heart relaxed
2) Atrial systole: P wave
3) Ventricular systole: QRS complex
4) Ventricular systole
5) Ventricular diastole: T wave
Systole
To contract; Systole is time between first and second heart sounds
Diastole
To dilate; Diastole is time between second heart sound and next first heart sound
Cardiac cycle: Heart relaxed: Passive ventricular filling
All chambers are relaxed. Blood movement is passive, so greater blood pressure in veins than in heart chambers. Semilunar valves are closed. As blood moves into atria, much of it flows into ventricles for two reasons:
1) AV valves are open
2) Atrial pressure is slightly greater than ventricular pressure
Most ventricular filling occurs during this time
Cardiac cycle: Atrial systole: Active ventricular filling
SA node generates action potential that stimulates atrial contraction. Represented by P wave of ECG. Atrial contraction begins cardiac cycle. As atria contract, they carry out primer pump function by actively forcing more blood into ventricles. Atria contraction lessens the time needed for ventricles to fill with blood (from passive filling to active filling).
Cardiac cycle: Ventricular systole: Period of isovolumetric contraction
Action potentials passes to AV node, down AV bundle, bundle branches, and Purkinje fibers, stimulating ventricular systole. Represented by QRS complex in ECG. As ventricles contract, ventricular pressures increase, causing blood to flow toward atria and close AV valves. Semilunar valves remain closed. Ventricular contraction continues and ventricular pressures rise, however, because all valves are closed, no blood flows from ventricles. Called period of isovolumetric contraction because volume of blood in ventricles does not change, even though ventricles are contracting. End-diastolic volume
Cardiac cycle: Ventricular systole: Period of ejection
Ventricular contraction continues, and ventricular pressure builds until it overcomes the pressures in pulmonary trunk and aorta. As a result, the semilunar valves are pushed open, and blood flows from ventricles into those arteries. Valves open at nearly same time. Larger left ventricular pressure causes blood to flow through body and lower right ventricular pressure causes blood to flow through lungs. Although pressure generated varies, the amount of blood pumped by each is almost the same. Ventricular pressure decreases toward end of ejection due to reduced blood flow. End-systolic volume
Cardiac cycle: Ventricular diastole: Period of isovolumetric relaxation
Ventricular repolarization, represented by T wave of ECG, leads to ventricular diastole. As ventricular diastole begins, the ventricles relax, and ventricular pressures decrease below pressures in pulmonary trunk and aorta. Consequently, blood begins to flow back toward ventricles, causing semilunar valves to close. With closure of semilunar valves, all heart valves are closed, and no blood flows into relaxing ventricles. Ventricular pressure drops below atrial pressure
Mean arterial pressure (MAP)
Necessary to move blood through blood vessels; Slightly less than the average of the systolic and diastolic pressures in aorta. It is proportional to cardiac output times peripheral resistance. Changes to either cardiac output or peripheral resistance can alter mean arterial pressure
MAP = CO * PR
MAP = HR * SV * PR
Cardiac output (CO)
Minute volume; The amount of blood pumped by the heart per minute
Also influenced by heart rate and stroke volume
CO = HR * SV
Peripheral resistance (PR)
Total resistance against which blood must be pumped
Intrinsic regulation
Results from heart’s normal functional characteristics and does not depend on either neural or hormonal regulation. Functions whether the heart is in place in body or is removed and maintained outside body under proper conditions
Extrinsic regulation
Involves neural and hormonal control
1) Parasympathetic control
2) Sympathetic control
3) Hormonal control
Parasympathetic control
Type of extrinsic regulation; Vagus nerve (CN X);
Increase in heart rate: results in reduced parasympathetic stimulation;
Strong parasympathetic stimulation can decrease heart rate below resting levels, but it has little effect on stroke volume;
If venous return remains constant while heart is inhibited by parasympathetic stimulation, stroke volume can increase; Acetylcholine causes plasma membranes of cardiac cells to hyperpolarize, so heart rate decreases because takes longer to depolarize to the point of an action potential
Sympathetic control
Type of extrinsic regulation; cervical and upper thoracic sympathetic chain ganglia;
Sympathetic stimulation increases both heart rate and force of muscular contraction. Stronger contractions can also increase stroke volume; Norepinephrine increases rate and degree of cardiac muscle depolarization, so frequency of action potentials increase
Hormonal control
Type of extrinsic regulation; Epinephrine and norepinephrine both increase the rate and force of heart contractions. Both secretions controlled by sympathetic stimulation of adrenal medulla; Occurs in response to physical activity, emotional excitement, or other stressful conditions
Effect of blood pressure and heart function
Blood pressure in systemic vessels must be high enough to allow nutrient and waste product exchange across walls of capillaries and to meet metabolic demands.
1) Blood pressure rises: Arterial walls stretched farther, and action potential frequency at baroreceptors increase. Baroreceptor reflexes reduce sympathetic stimulation and increase parasympathetic stimulation of heart, causing heart rate to slow.
2) Blood pressure decreases: Arterial walls are stretched to lesser extent, and action potential frequency decreases. Causes decreases parasympathetic and increased sympathetic stimulation of heart, resulting in greater heart rate and force of contraction
Baroreceptor in heart
Baroreceptor reflexes detect changes in blood pressure and lead to changes in heart rate and force of contraction. Baroreceptors measure blood pressure by detecting degree of stretch of blood vessel walls
Effects of pH and CO2 and heart function
Chemoreceptors are sensitive to changes in pH and CO2.
pH: Drop in blood pH, which is often due to a rise in CO2, decrease parasympathetic and increase sympathetic stimulation of the heart, resulting in increased heart rate and force of contraction
CO2: Increased cardiac output causes greater blood flow through lungs, where CO2 is eliminated from body. This helps lower blood CO2 level to within its normal range, which increases blood pH
Effect of O2 and heart function
Chemoreceptors are sensitive to blood O2 levels.
Decrease in O2 levels: Activates carotid and aortic body chemoreceptor reflexes from other reflexes. Results in decreased heart rate and increased vasoconstriction. Vasoconstriction causes blood pressure to rise, which promotes blood delivery despite the decrease in heart rate. Slowing heart rate reduces need for O2. Prolonged decreases in blood O2 levels increase heart rate
Excess extracellular ion concentration of K+
Causes heart rate and stroke volume to decrease. Twofold increase results in heart block, which is loss of action potential conduction through heart. Causes changes in membrane potential that lead to decreased rate at which action potentials are conducted. Decreased conduction rates can lead to ectopic action potentials. Membrane potential changes result in less Ca2+ entering sarcoplasm, so strength of cardiac muscle contraction lessens
Excess extracellular ion concentration of Ca2+
Produces greater force of cardiac contraction. Elevated blood Ca2+ levels lower heart rate
Effect of body temperature and heart function
Small increases in cardiac muscle temperature cause heart rate to speed up. Exercise or fever results in increased heart rate and force of contraction
Decreases in temperature results in heart rate to slow. Hypothermia and heart surgery causes heart rate to drop
Blood vessel structure
Besides capillaries and venules, blood vessel walls consist of three distinct tissue layers:
1) Tunica intima
2) Tunica media
3) Tunica externa
Tunica intima
Most internal layer of blood vessel wall. Consists of four layers:
1) Endothelium
2) Basement membrane
3) Lamina propria: Thin layer of connective tissue
4) Internal elastic membrane: Separates tunica intima from tunica media
Tunica media
Consists of smooth muscle fibers arranged circularly around blood vessel. Amount of blood flowing through blood vessel is regulated by contraction or relaxation of smooth muscle in tunica media. Contains elastic and collagen fibers. External elastic membrane separates tunica media from tunica externa
Vasoconstriction: Smooth muscle contraction and causes decrease in blood vessel diameter, thereby decreasing blood flow
Vasodilation: Smooth muscle relaxation and causes increase in blood vessel diameter, thereby increasing blood flow
Tunica externa
Composed of connective tissue, which varries from dense connective tissue near tunica media and loose connective tissue that merges with connective tissue surround blood vessels
Types of arteries
1) Elastic arteries
2) Muscular arteries
3) Arterioles
Biggest -> smallest
Elastic arteries
Largest diameters and called conducting arteries. Vessels first to receive blood from heart, so blood pressure is high. When stretched, walls of elastic arteries recoil, preventing drastic decreases in blood pressure. Have greater amount of elastic tissue and smaller amount of smooth muscle compared to other arteries. Responsible for elastic characteristics of blood vessel wall, but collagenous connective tissue determines degree it can stretch. Tunica intima is thick, whereas tunica externa is thin
Muscular arteries
Medium-sized and small arteries. Muscular in the name refers to thick tunica media. Tunica intima has well-developed internal elastic membrane. Tunica externa is composed of thick layer of collagenous connective tissue that blends with surrounding tissue. Frequently called distributing arteries because smooth muscles allow them to partially regulate blood flow to different body regions by either constricting or dilating
Arterioles
Smallest arteries where three layers can be identified. Transport blood from small arteries to capillaries. Tunica media has no observable internal elastic membrane. Capable of vasodilation and vasoconstriction
Types of capillaries
1) Continuous capillaries
2) Fenestrated capillaries
3) Sinusoidal capillaries
Continuous capillaries
Walls exhibit no gaps between endothelial cells. Less permeable to large molecules. Located in muscle, nervous tissue and other locations
Fenestrated capillaries
Endothelial cells have numerous fenestrae, or areas where cytoplasm is absent and plasma membrane consists of porous diaphragm that is thinner than normal plasma membrane. Located in tissues where capillaries are highly permeable, such as intestinal villi, ciliary processes of the eyes, choroid plexuses of central nervous system, and glomeruli of kidneys
Sinusoidal capillaries
Larger in diameter than other capillaries, and their basement membrane is less prominent or completely absent. Their fenestrae are larger and gaps can exist between endothelial cells. Occur in places where large molecules or whole cells move across walls, such as liver or endocrine glands
Types of veins
1) Venules
2) Small veins
3) Medium or large veins
4) Portal veins
5) Valves
6) Vasa vasorum
Venules
Smallest veins. Similar to capillaries because are also composed of endothelium. Collect blood from capillaries and transport it to small veins. Nutrient exchange occurs across venule walls
Small veins
Smooth muscle fibers form a continuous layer. Contains tunica externa composed of collagenous connective tissue. Nutrient exchange occurs, but to a lesser to degree because of an increase in wall thickness
Medium and large veins
Large veins transport blood from medium veins to heart. For both, tunica intima is thin and consists of endothelial cells, a relatively thin layer of collagenous connective tissue, and a few scattered elastic fibers. Tunica media is also thin with some collagen fibers and sparse elastic fibers. Tunica externa, which is composed of collagenous connective tissue, is predominant layer
Portal veins
A capillary network is directly connected to another capillary network by portal veins. There is no pumping mechanism. Three portal veins are found in humans:
1) Hepatic portal veins
2) Hypothalamohypophysial portal veins
3) Renal nephron portal systems
Valves in veins
Veins that have diameters greater than 2mm contain valves. Valves consist of folds in tunica intima that form two flaps shaped like semilunar valves of heart, Two folds overlap in middle of vein so that, when blood attempts to flow in reverse direction, the valves occlude, or block, the vessel. Medium veins contain many valves, and the number of valves is greater in veins of lower limbs than upper limbs
Vasa vasorum
For arteries and veins greater than 1mm in diameter, nutrients cannot diffuse from lumen of vessel to all layers of wall. Therefore, nutrients are supplied to blood vessel walls by way of small blood vessels called vasa vasorum, which penetrate from the exterior of the vessel to form a capillary network in the tunica externa and tunica media
Innervation of blood vessel walls
Most are richly innervated by unmyelinated sympathetic nerve fibers. Some blood vessels, such as those in penis and clitoris, are innervated by parasympathetic fibers. Small arteries and arterioles are innervated to a greater extent.
Laminar blood flow
Fluid, typically blood, flowing through long, smooth-walled tubes in a streamlined fashion. Layer nearest wall of tube experiences the greatest resistance to flow because it moves against stationary wall. Flow in vessel consists of movement of concentric layers, with the outer layer moving most slowly.
Turbulent blood flow
Laminar flow is interrupted and becomes turbulent flow when the rate of flow exceeds a critical velocity or when the fluid passes a constriction, a sharp turn, or a rough surface. Caused by numerous small currents flowing at an angle to the long axis of the vessels resulting in flowing whorls in the blood vessel. Common as blood flows past the valves in the heart and is partially responsible for the heart sounds. Occurs primarily in heart and to a lesser extent where arteries branch
Blood pressure
A measure of force blood exerts against blood vessel walls
How is blood pressure measured
1) Mercury manometer measures blood pressure in millimeters of mercury
2) Can be measured directly by inserting a cannula (tube) into a blood vessel and connecting a manometer or an electronic pressure transducer to it
3) Placing a catheter into a blood vessel or into a chamber of the heart to monitor pressure changes in possible but not appropriate for routine clinical examinations
Poiseuille’s Law
Flow = (pi(P1-P2)D^4)/(128vl)
The laminar flow rate of fluids through a cylindrical tube, such as blood flow in blood vessels
Viscosity vs blood flow
Measure of a liquid’s resistance to flow. As viscosity of a liquid increases, the pressure required to force it to flow also increases
Laplace’s Law and Critical closing pressure
Critical closing pressure: The lowest pressure at which the vessel remains open or the minimum force necessary to hold open a vessel. Force is dependent on diameter of vessel and blood pressure
Laplace’s Law: Force = Vessel Diameter * Pressure or F = DP
Explains how vessel diameter affects the force applied to vessel wall. As diameter of vessel increases or pressure in vessel increases, the force applied to vessel wall increases.
Vessel diameter and Vascular compliance
Vascular compliance: The tendency for blood vessel volume to increase as blood pressure increases. Vessels with greater compliance stretch more easily and vessels with smaller compliance stretch less easily
Percent distribution of blood in each of the systemic vessel types
Systemic vessels: 84%
Veins: 64% total blood volume
(Large - 39%; Small - 25%)
Arteries: 15% total blood volume
(Large - 8%; Small - 5%; Arterioles - 2%)
Capillaries: 5%
Pulmonary vessels: 9%
Heart: 7%
Cross-sectional area of blood vessels vs. Rate of blood flow
The velocity of blood flow changes relative to the cross-sectional area of each blood vessel type. Velocity of blood flow in a particular blood vessel type is inversely proportional to its total cross-sectional area. As the veins become larger in diameter, their total cross-sectional area decreases and velocity of blood flow increases
How blood pressure and resistance changes as blood flows through blood vessels
Blood pressure: As blood flows through circulation, from arteries through the capillaries and the veins, the pressure falls progressively by the time it returns to the right atrium. The decrease in blood pressure in each part of the systemic circulation is directly proportional to the resistance to blood flow. If blood pressure increases, blood flow will also increase
Resistance: The greater the resistance in a blood vessel, the more rapidly the pressure decreases as blood flows through it. Resistance to flow is associated with diameter of vessels. Vessel diameter decreases, resistance to flow increases. Blood vessels with smaller diameters have higher levels of resistance. If resistance increases, blood flow will decrease
Pulse pressure
The difference between systolic and diastolic pressures. Stroke volume and vascular compliance both influence pulse pressure greatly. Stroke volume is directly proportional and vascular compliance is indirectly proportional
Systolic/Diastolic
Locations on body where pulse can be detected
10 major locations on each side of body where large arteries are close to surface:
1) Superficial temporal artery
2) Facial artery
3) Common carotid artery
4) Axillary artery
5) Brachial artery
6) Radial artery
7) Femoral artery
8) Popliteal artery
9) Dorsalis pedis artery
10) Posterior tibial artery
Exchange of materials across capillary wall
Diffusion:
1)Oxygen, hormones, and nutrients diffuse from a higher concentration in capillaries to a lower concentration in the interstitial fluid
2) Waste products diffuse from higher concertation in interstitial fluid to a lower concentration in capillaries
3) Lipid-soluble molecules (O2, CO2, fatty acids, steroid hormones) diffuse through plasma membranes of the endothelial cells of capillaries
4) Water-soluble substances (glucose and amino acids) diffuse through intercellular spaces or through fenestrations of capillaries
Preload vs Cardiac output
Preload: Determined by the volume of blood that enters the heart from the veins
If volume of blood is increased because of a rapid transfusion, the amount of blood flow to the heart through the veins increases. This increases the preload, which causes the cardiac output to increase
Venous tone vs Cardiac output
Venous tone: A continual state of partial contraction of the veins as a result of sympathetic stimulation
Increased sympathetic stimulation increases venous tone by causing veins to constrict more, which forces the large venous volume to flow toward the heart. Venous return increases causing an increase in cardiac output
Gravity vs Cardiac output
When changing from lying down to standing, the blood pressure in veins of lower limbs increases. The increased blood pressure causes veins to expand. As veins expand and fill with blood, venous return decreases because less blood is returning to heart. As venous return decreases, cardiac output and blood pressure decrease
In a standing position, hydrostatic pressure
caused by gravity increases blood pressure
below the heart and decreases pressure
above the heart.
Muscular movement improves venous return.
Local control vs Blood flow
Local control of blood flow is achieved by periodic relaxation and contraction of precapillary sphincters regulating blood flow through capillary networks of the tissues. Blood flow is proportional to metabolic needs of the tissue, therefore, as metabolic needs increase, blood flow increases to supply the greater need for O2 and other nutrients
Nervous mechanisms vs Blood flow
Nervous regulation provides a means to regulate blood flow by altering the volume of blood flowing to different regions of the body. Nervous regulation by autonomic nervous system (sympathetic) can function rapidly. Sympathetic vasomotor fibers are neurons that regulate the level of smooth muscle contraction in vessel walls. These fibers innervate all blood vessels besides capillaries. Innervation of small arteries and arterioles allows sympathetic nervous system to increase or decrease resistance to blood flow
Hormonal mechanisms vs Blood flow
Sympathetic action potentials also cause release of epinephrine and norepinephrine into blood from adrenal medulla. These neurohormones are transported in blood. In most vessels they cause vasoconstriction, but in some vessels, epinephrine binds to B-adrenergic receptors and can cause blood vessels in skeletal muscle to dilate
Factors that determine mean arterial pressure
1) Heart rate
2) Stroke volume
3) Peripheral resistance
Increase in any one of these elevates blood pressure
Short-term regulation of blood pressure
1) Baroreceptor reflexes: Increase in blood pressure increases parasympathetic stimulation of the heart and decreases sympathetic stimulation of the heart, resulting in a decrease in blood pressure; Carotid sinus and aortic arch; Maintains blood pressure
2) Adrenal medullary mechanism: Results from stimulation of adrenal medulla by sympathetic nerve fibers. Releases epinephrine and norepinephrine into bloodstream; Increases heart rate and stroke volume; Plays a role in during exercise and emergencies; Increases blood pressure
3) Chemoreceptor reflexes: Maintain homeostasis by responding to changes in blood composition. Stimulated by decreasing blood O2 levels or increasing blood CO2 levels, which causes blood pH to decrease which causes mean arterial pressure to rise; Maintains blood pressure
4) Central Nervous System Ischemic response: Increase in blood pressure in response to a lack of blood flow to medulla oblongata. Functions primarily in response to emergency situations when brain receives little O2
Long-term regulation of blood pressure
1) Renin-angiotensin-aldosterone mechanism: Regulate blood pressure by altering blood volume through production of urine. Kidneys increase urine output as blood volume and arterial pressure increase, which reduces blood volume and blood pressure
2) Antidiuretic Hormone Mechanism: Baroreceptors are sensitive to changes in blood pressure. Decrease in blood pressure result in release of ADH. ADH cause blood vessels to constrict to increase blood pressure
3) Atrial natriuretic Mechanism: ANH acts on kidneys to increase rate of urine production and dilate arteries and veins. Loss of water and Na+ in urine causes blood volume to decrease, which causes a decrease in blood pressure
4) Fluid shift mechanism: Occurs in response to small changes in pressures across capillary walls. As blood pressure increases, some fluid is forced from capillaries into interstitial spaces to help prevent the development of high blood pressure. As blood pressure falls, interstitial fluid moves into capillaries to resist further decline in blood pressure; Maintains blood pressure
5) Stress-Relaxation Response: Characteristic of smooth muscle fibers. When blood volume suddenly declines, blood pressure also decreases, reducing the force applied to smooth muscle fibers in blood vessel walls. As a result, smooth muscle fibers contract, reducing the volume of blood vessels, and thus resisting a further decline in blood pressure; Maintains blood pressure
Functions of lymphatic system
1) Fluid balance
2) Lipid absorption
3) Defense
Parts of lymphatic system
Lymph, lymphatic vessels, lymphatic tissues, lymphatic nodules, lymph nodes, tonsils, spleen, and thymus
Lymphatic vessel structure
Originate as small, dead-end tubes called lymphatic capillaries, which are located in most tissues of the body. Lymphatic capillaries form lymphatic vessels, which resemble small veins. There are three layers:
1) Inner layer: Consists of endothelium surrounded by an elastic membrane
2) Middle layer: Consists of smooth muscle cells and elastic fibers
3) Outer layer: A thin layer of fibrous connective tissue
Small lymphatic vessels have one-way valves along their lengths
Lymph formed
Lymph is formed when fluid from the spaces between tissues, known as interstitial fluid, is collected through tiny lymph capillaries located throughout the body
How is lymph transported through lymphatic vessels
There are 3 mechanisms:
1) Contraction of lymphatic vessels: Pump lymph along the vessel by way of smooth muscle contractions. Lymph moves from chamber of chamber (made with valves that divide lymphatic vessels)
2) Contraction of skeletal muscles: When surrounding skeletal muscle cells contract, lymphatic vessels are compressed, causing lymph to move
3) Thoracic pressure changes: During inspiration, pressure in thoracic cavity decreases, lymphatic vessels expand, and lymph flows into them. During expiration, pressure in thoracic cavity increases, and lymphatic vessels are compressed, causing lymph to move
Structure and function of lymph nodes
Structure: Round,, oval, or bean-shaped bodies distributed along various lymphatic vessels. Lymph nodes are connected in a series, so that lymph leaving one lymph node is carried to another lymph node, and so on
Function: Filter lymph, which enters and exits the lymph nodes through lymphatic vessels, and remove bacteria and other materials.
Function of tonsils
Large groups of lymphatic nodules and diffuse lymphatic tissue located deep to the mucous membranes within the pharynx. The tonsils protect against bacteria and other potentially harmful material entering the pharynx from the nasal or oral cavity. In adults, tonsils decrease in size and eventually may disappear
Function of spleen
Roughly size of clenched fist and is located on left, superior part of abdominal cavity
Functions include destroying defective red blood cells, detecting and responding to foreign substances in the blood, and acting as a blood reservoir.
Function of thymus
Bilobed gland located in superior mediastinum (within thoracic cavity)
Thymus is the site for the maturation of T cells. Secretes thymosin, a hormone that is important in T-cell maturation process. Lymphocytes are produced in thymus, although most degenerate
Innate immunity
The body recognizes and destroys certain foreign substances, but the response to them is the same each time the body is exposed
Adaptive immunity
The body recognizes and destroys foreign substances, but the response to them is faster and stronger than the first time the foreign substance was encountered
Specificity and memory when applied to immunity
Both are characteristics of adaptive immunity, but not innate immunity
Specificity: The ability of adaptive immunity to recognize a particular substance. For example, innate immunity can act against bacteria in general, whereas adaptive immunity can distinguish among various kinds of bacteria.
Memory: The ability of adaptive immunity to “remember” previous encounters with a particular substance. As a result, the response is faster, stronger, and longer lasting.
3 components of innate immunity
1) Physical barriers: Prevent entry of disease-causing agents into body and remove microorganisms and other substances from body surface
2) Chemical mediators: Some are on surface
3) Cells and production of chemicals: Types of leukocytes and more
Chemical mediators
Surface chemicals: Lysozymes lyse cells; acid secretions prevent microbial growth; mucus on mucous membranes trap microorganisms
Histamine: Attracts eosinophils; Allergy reaction
Kinins: Attract neutrophils
Interferons: Interfere with virus production and infection
Complement: Lyse cells, promote phagocytosis, and attract neutrophils, monocytes, macrophages, and eosinophils
Prostaglandins: Stimulate pain receptors
Leukotrienes: Attract neutrophils and eosinophils
Pyrogens: Stimulate fever production
Cells of innate immunity
Neutrophil: Phagocytosis and inflammation, usually the first cell to leave the blood and enter infected tissues
Monocyte: Leaves the blood and enters tissues to become a macrophage
Macrophage: Most effective phagocyte; important in later stages of infection and in tissue repair; located throughout the body to “intercept” foreign substances, processes antigens; involved in the activation of B cells and T
cells
Basophil: Motile cell that leaves the blood, enters tissues, and releases chemicals
that promote inflammation
Mast cell: Nonmotile cell in connective tissues that promotes inflammation through the release of chemicals; Phagocytize bacteria readily
Eosinophil: Enters tissues from the blood and defends against parasitic infections; participates in inflammation associated with asthma and allergies
Natural killer cells: Lyses tumor and virus-infected cells
Antigen
Substances that stimulate adaptive immunity, or the ability of lymphocytes to recognize, respond to, and “remember” a particular substance
Events of inflammatory response
1) As a result of injury, such as a splinter piercing the skin, bacteria enter the tissue, causing additional damage.
2) This damage stimulates the release or activation of chemical mediators, such as histamine, complement, kinins, and eicosanoids (e.g., prostaglandins and leukotrienes).
3) The chemical mediators cause vasodilation, which increases blood flow, bringing phagocytes and other white blood cells to the area, as well as increased vascular permeability that allows fibrinogen and complement to enter the tissue from the blood. The increase in blood flow and vascular permeability results in redness and swelling, two of the cardinal signs of inflammation.
4) White blood cells increase in number at the injury site as they move from the blood into the tissue by diapedesis.
5) Chemical mediators, such as fibrin and complement, increase at the injury site as well. Fibrinogen is converted to fibrin, which walls off the infected area, preventing the spread of infection.
Complement further enhances the inflammatory response and attracts additional phagocytes.
6) The process of releasing chemical mediators and attracting phagocytes and other white blood cells continues until the bacteria are destroyed.
7) Phagocytes, such as neutrophils and macrophages, remove microorganisms and dead tissue, and the damaged tissues are repaired.
Haptens vs complete antigen
Haptens: Incomplete antigens; They can bind to antigens but do no induce an immune response on their own
Complete antigen: A substance that, when introduced into the body, not only triggers an immune response but also reacts with the products of that response, like antibodies
Haptens in allergic reactions
Haptens can lead to allergic reactions. Haptens, like penicillin, can break down and bind to other molecules in the blood. The combined molecule can then stimulate an allergic reaction that ranges from a rash and fever to severe symptoms that can lead to death
Major histocompatibility complex (MHC) molecules in immunity
Glycoproteins found on plasma membranes of most body’s cells. Each MHC molecule has a variable region that can bind antigens found inside the cell. MHC molecules display antigens produced in or processed by the cell on the cell’s plasma membrane. As MCH molecules are formed in the cell, they combine with fragments of other molecules in the cytoplasm. The MHC molecules are then moved to the plasma membrane, where these fragments are displayed to immune cells
MHC Class I molecules
Display endogenous antigens (antigens produced in the cell); Found on nucleated cells; Virus proteins produced within cell and broken down in cytoplasm. Protein fragments enter rough endoplasmic reticulum and combine with MHC Class I molecules to form complexes. It moves through golgi apparatus to be transported to plasma membrane. Binds to T-cell receptors on the surface of T cells; Activated T cells can destroy infected cells
MHC Class II molecules
Display exogenous antigens ( antigens processed by cell with substances obtained from external environment); Found on phagocytic cells called antigen-presenting cells; Antigen-presenting cells engulf substances encountered in extracellular environment and process then within cytoplasm. The antigen is broken down to form processed antigens. Vesicles from Golgi apparatus combine MHC class II molecules and processed antigens. Its transported to plasma membrane, where they are displayed to other immune cells and it can stimulate immune cells
Antibody-mediated immunity
Involves proteins called antibodies, which are found in extracellular fluids;
Involves production of antibodies in response to extracellular antigens. Exposure of body to an antigen can lead to activation of B cells (from helper T cells) and to the production of antibodies, which are responsible for destroying the antigen; Effective against extracellular antigens, such as bacteria, viruses, and parasites, that are outside of cell; Can also cause immediate hypersensitivity reactions; Not effective against cytoplasmic microorganisms
Cell-mediated immunity
Involves actions of T cells; Most effective against cytoplasmic microorganisms through the action of cytotoxic cells responding to endogenous antigens because it destroys cells in which the microorganisms are located; Through interactions with MHC molecules, cytotoxic T cells can identify abnormal or infected cells of the body; Involves delayed hypersensitivity reactions and control of tumors
Helper cells, Cytotoxic cells, Suppressor cells
Structure of an antibody
Proteins produced in response to an antigen
Consist of two heavy and two light polypeptide chains. Variable region of antibody binds to antigen. Constant region of antibody can activate the classical pathway of the complement cascade. The constant region can also attach the antibody to the plasma membrane of cells
Direct effects of antibodies
Direct effects:
1) The antibody can bind to the antigenic determinant and interfere with the antigen’s ability to function
2) The antibody can combine with an antigenic determinant on two different antigens, rendering the antigens ineffective
Indirect effects of antibodies
Most effectiveness results from indirect mechanisms:
1) When antibody (IgG or IgM) combines with antigen through variable region, the constant region can activate the complement cascade through the classical pathway. Activated complement stimulates inflammation; attracts neutrophils, monocytes, macrophages, and eosinophils to sites of infection; and kills bacteria by lysis
2) Antibodies (IgE) can initiate an inflammatory response. Antibodies attach to mast cells or basophils through their constant region. When antigens combine with variable region of the antibodies, the mast cells or basophils release chemicals through exocytosis, and inflammation results
3) Opsonins are substances that make antigen more susceptible to phagocytosis. An antibody (IgG) acts as an opsonin by connecting to an antigen through the variable region of the antibody and to a macrophage through constant region of antibody. Macrophage then phagocytizes antigen and antibody
Primary responses to antigen
First exposure of B cell to an antigen causes primary response. Includes a series of cell divisions, cell differentiation, and antibody production. Antibodies are eventually produced by B cell. Primary response takes 3-14 days to produce enough antibodies to be effective against antigen
Secondary responses to antigen
Memory response
Occurs when immune system is exposed to an antigen against which it has already produced a primary response. When exposed to the antigen, memory B cells rapidly divide to produce plasma cells, which produce large amounts of antibody. Provides better protection for two reasons:
1) Time required to start producing antibodies is less
2) Amount of antibody produced is much larger
Antigen is quickly destroyed, no disease symptoms develop, and the person is immune
Includes formation of new memory B cells, which are the basis for adaptive immunity
Four ways adaptive immunity can be acquired
1) Active natural
2) Active artificial
3) Passive natural
4) Passive artificial
Active natural
Active natural: Natural exposure to an antigen can cause immune system to mount an adaptive immune response against antigen; Usually develops symptoms of disease
Active artifical
Active artificial: Antigen is deliberately introduced into a person’s body to stimulate immune system; Called immunization, and introduced antigen is vaccine; Part of a microorganism, a dead microorganism, or a live, altered microorganism. Antigen was changed so it stimulates an immune response but will not cause disease symptoms. Preferred method of acquiring adaptive immunity
Passive natural
Passive natural: Results when antibodies are transferred from a mother to her child across the placenta before birth or through the mother’s milk after the child is born. Following birth, antibodies protect baby for first few months. Eventually, antibodies break down, and the baby must rely on own immune system
Passive artifical
Passive artificial: Usually begins with vaccinating an animal. After animal’s immune system responds to antigen, antibodies are removed from animal and injected into human requiring immunity. Provides immediate protection for individual and is preferred when time might not be available for individual to develop own immunity. Only provides temporary immunity because antibodies are used or eliminated by recipient
Helper T cells
First lymphocytes to increase in number when exposed to antigen. Increased number of helper T cells responding to antigen can find and stimulate B cells or cytotoxic T cells. Subsequently, the number of those cells increase; Promote or inhibit the activities of both antibody-mediated and cell-mediated immunity
Cytotoxic T cell
Responsible for destroying cells by lysis or by producing cytokines; Become activated when exposed to specific antigen; Responsible for producing the effects of cell-mediated immunity
Regulatory T cell
Inhibits B cells, helper cells, and cytotoxic cells; Promote or inhibit the activities of both antibody-mediated and cell-mediated immunity; Suppress immune responses
Memory T cell
Quick and effective response to an antigen against which the immune system has previously reacted; Responsible for adaptive immunity
B cell
After activation, differentiates to become plasma cell or memory B cell; Give rise to cells that produce antibodies
Plasma cell
Produces antibodies directly or indirectly responsible for destroying antigen
Memory B cell
Quick and effective response to an antigen against which the immune system has previously reacted; Responsible for adaptive immunity
Dendritic cell
Processes antigen and is involved in the activation of B cells and T cells
Pericarditis
Inflammation of the pericardium, the sac-like membrane that surrounds the heart
Blood flow through heart
Inferior vena cava/Superior vena cava
Right atrium
Tricuspid valve
Right ventricle
Pulmonary semilunar valve
Pulmonary trunk/arteries
LUNGS
Pulmonary veins
Left atrium
Mitral valve
Left ventricle
Aortic semilunar valve
Aorta
BODY
Repeat
Left coronary artery branches
1) Left anterior descending artery
2) Circumflex artery
Right coronary artery branches
1) SA nodal branch
2) Right marginal branch
3) Posterior descending artery
4) AV nodal branch
3 veins that drain heart
1) Great cardiac vein
2) Middle cardiac vein
3) Small cardiac vein
Arrhythmia
Abnormal rhythm of heart
Characteristics: Irregular heartbeat, palpitations, dizziness, shortness of breath, fatigue
Common causes: Hypertension, electrolyte imbalance, heart attack, heart failure, alcohol
Ectopic focus
Abnormal site of electrical impulse generation that is outside the normal pacemaker cells, usually the SA node
Characteristics: Abnormal impulse generation, premature beats, irregular rhythm
Bradycardia
Slower-than-normal heart rate, typically less than 60 beats per minute
Characteristics: Slow heart rate, fatigue, shortness of breath, chest pain, heart murmur
Common causes: Athletic training, sleep, sick sinus syndrome, heart block, heart attack
Tachycardia
Abnormally fast heart rate, typically greater than 100 beats per minute
Characteristics: Fast heart rate, palpitations, shortness of breath, dizziness, chest pain
Common causes: Exercise, stress, arrhythmias, heart disease, anemia, shock
Angiogenesis
New blood vessels form from pre-existing ones
Critical for growth, development, and healing
Circulatory shock
Blood volume low; Cannot circulate normally
Results in inadequate blood flow to meet tissue needs
Hypovolemic: large scale blood loss, vomit, diarrhea
Vascular: Extreme vasodilation
Cardiogenic: Poor heart function
Obstructive: Obstruction of blood flow
Anaphylactic: Massive histamine release (allergic reaction)
Atherosclerosis
Chronic inflammatory disease characterized by buildup of plaque (mixture of fat, cholesterol, calcium, and other substances) within walls of arteries, leading to the thickening and stiffening of arterial walls
Can restrict blood flow, increase risk of clot formation, and contribute to events like heart attack, strokes, and peripheral artery disease
IgM
First antibody released
IgA
In mucus and other secretions
IgD
On surface of B cells (Functions as a B cell receptor)
IgG
75-85% of antibodies in plasma; From secondary and late primary responses; Confers passive immunity to fetus
IgE
Active in some allergies and parasitic infections
