The Circulatory System:The Heart

Three Main Structures of the Circulatory System

the heart which is separated by a septum

the blood which carries oxygen and food over and above the removal of carbon dioxide (type A, B, AB, and O / + or – Rh factor)

the blood vessels (arteries / arterioles, veins / venules, and capillaries / capillary beds)

HEART: LOCATION, SIZE, & POSITION

the function of the circulatory system is to help transport materials throughout the body

differing amounts of nutrients and waste products enter and leave the fluid surrounding each body cell (ECF) on a nonstop basis

in addition, requirements for: ¹hormones, ²body salts, ³water, and other critical substances are constantly changing

through the process of homeostasis, the circulatory system supplies cell’s with their varying needs

so, we begin the study of the circulatory system with the heart….. the pump that keeps blood moving through a closed circuit of blood vessels (pulmonary to systemic)

the heart, the main organ of the circulatory system, is one of the strongest muscles in the body

it is approximately 6 inches long and 4 inches across (approximately the size of your fist) weighing up to 12 ounces

(on a scratch piece of paper draw these dimensions out)

the heart requires 10 pints of blood, in one circulation, between the systemic and pulmonary systems

it includes 100,000 miles of blood vessels, or roughly 200 miles per pound of adipose tissue

it beats between 60 – 90 times per minute

and, it is comprised of 2 pumps (the right and left divisions) as well as 4 chambers (two atriums and two ventricles)

the right atrium receives blood, from the body, by means of veins which are low in oxygen

the right ventricle subsequently sends the venous blood on to the lungs for oxygenation

the left atrium is then given blood, high in oxygen content, from the lungs

the left ventricle, having the thickest walls of all the chambers of the heart, pumps oxygenated blood to the entire body via through arteries

(page 721 in your text)

the atria are smaller than the ventricles and their walls are thinner and less muscular

atria are often called receiving chambers because blood enters the heart through veins that open up into these upper cavities

eventually, blood is pumped from the heart into arteries that exit from the ventricles

ventricles are, at times, referred to as the discharging chambers of the heart

a solid wall-like septum separates the atrium and ventricle on the right side from their counterparts on the left

as a result, blood from one side of the heart never mixes with blood from the other side (except in the fetus)

the septum between the atrial chambers is called the interatrial septum with the interventricular septum separating the ventricles

an atrioventricular valve (A-V valve), the tricuspid on the right and the mitral on the left, guarantee one-way blood flow between the atria and ventricles

all of this would not be possible though, if the right atrium did not receive blood from two large veins: the superior vena cava and the inferior vena cava

a smaller vein, the coronary sinus, also drains blood into the right atrium from the myocardium of the heart itself

(Is the coronary sinus on the anterior or posterior surface of the heart?)

anyways getting back to the large tricuspid valve, it has three tapered projections called cusps….. as its name implies

the tricuspid valve lies between the right atrium and the right ventricle

this valve permits blood to move from the right atrium into the right ventricle preventing backflow

strong, fibrous strings called chordae tendineae attach to the cusps of the tricuspid valve on the ventricular side

these strings originate from small mounds of cardiac muscle tissue, the papillary muscles, that project inward from the walls of the ventricle

HEART VALVES

the papillary muscles contract when the ventricle contracts

as the tricuspid valve closes, these muscles pull on the chordae tendineae and prevent the cusps from swinging back into the atrium

as for the right ventricle, it has a thinner muscular wall than the left ventricle

this right chamber pumps blood a short distance to the lungs against a relatively low resistance to blood flow

the left ventricle, on the other hand, must force blood to all the other parts of the body against a much greater resistance to flow

thus, the walls of the left ventricle are much thicker than those found on the right

when the muscular wall of the right ventricle contracts, the blood inside its chamber is put under increasing pressure

as a result, the tricuspid valve closes passively resulting in the only exit for the blood through the pulmonary trunk which divides to form the left and right pulmonary arteries that lead to the lungs

(create a flow chart that illustrates the opening & closing of the tricuspid valve)

at the base of the trunk is a pulmonary valve with three cusps (pulmonary semilunar valve)

this pulmonary semilunar valve allows blood to leave the right ventricle and prevent backflow into the ventricular chamber

the left atrium receives blood from the lungs through four pulmonary veins… two from the right lung and two from the left lung

blood passes from the left atrium into the left ventricle through the mitral valve, or bicuspid valve, which prevents blood from flowing back into the left atrium from the ventricle (miter / shaped like a type of hat)

as with the tricuspid valve, the papillary muscles and the chordae tendineae prevent the cusps of the mitral valve from swinging back into the left atrium during ventricular contraction

when the left ventricle contracts, the mitral valve closes passively, and the only exit is through a larger artery called the aorta

at the base of the aorta is the aortic valve which has three cusps

the aortic valve opens and allows blood to leave the left ventricle as it contracts

when the ventricular muscles relax, this valve closes preventing blood from backing up into the ventricle

miter hat“two”

(there are 3 cusps for each valve except the __________)

the mitral and tricuspid valves are called atrioventricular valves because they are between atria and ventricles

the pulmonary and aortic valves are called semilunar because of the half-moon shapes of their cusps

AV VALVE MECHANICS ventricles contract / “lub”

AV valves closespressure risessemilunar valves openblood flows into great vessels

ventricles relax / “dub”pressure dropssemilunar valves closesAV valves openblood flows from atria to ventricles

OPERATION OF ATRIOVENTRICULAR VALVES

OPERATION OF SEMILUNAR VALVES

HEART VALVES

as for general location, most people probably think the heart rests within the thoracic cavity on the left side of the body

in reality, the heart is located between the lungs in the lower portion of the mediastinum

if one drew an imaginary line through the middle of the trachea and continued the line down through the thoracic cavity, to divide it into right and left halves, about two thirds of the heart’s mass would be to the left of this line with approximately one third to the right

Heart Position

the heart is often described as a “triangular” organ with the apex, or blunt point of the lower edge, lying on the diaphragm pointing towards the left

it is important to know the location of the heart

for example: placing a stethoscope to hear the heart sounds, placing electrodes on the chest to record an electrocardiogram (ECG), or performing cardiopulmonary resuscitation (CPR) depend on accurate knowledge of the heart’s position

Position, Size, and Shape of the Heart

located in mediastinum between the lungs

base - broad superior portion of heart

apex - inferior end, tilts to the left, and tapers to a point

External Anatomy (Anterior)

External Anatomy (Posterior)

Functions of the Heart

1. generating blood pressure: contractions of the heart generate blood pressure, which is responsible for blood movement through the blood vessels

2. routing blood: the heart separates the pulmonary and systemic circulations ensuring the flow of oxygenated blood to tissues

3. ensuring one-way blood flow: the valves of the heart ensure a one-way flow of blood through the heart and blood vessels

4. regulating blood supply: changes in the rate and force of heart contraction match blood delivery to the changing metabolic needs of the tissues… such as during rest, exercise, and changes in body position

Coverings of the Heart

the pericardium encloses the heart and the proximal ends of the large blood vessels to which it attaches

the pericardium consists of an outer bag, the fibrous pericardium, that surrounds a more delicate double-layered sac

the innermost layer of this sac, the visceral pericardium, covers the heart

note: at the base of the heart, the visceral pericardium turns back on itself to become the parietal pericardium which forms the inner lining of the fibrous pericardium

the fibrous pericardium is dense connective tissue

it is attached to the central portion of the diaphragm, the posterior of the sternum, the vertebral column, and the large blood vessels emerging from the heart

between the parietal and visceral layers of the pericardium is a space, the pericardial cavity, that contains a small volume of serous fluid

this fluid reduces the friction between the pericardial membranes as the heart moves within them

Walls of the Heartthe wall of the heart is composed of three

distinct layers… an outer epicardium, a middle myocardium, and an inner endocardium

the outer epicardium corresponds to the visceral pericardium which protects the heart by means of friction reduction

it is a serous membrane that consists of connective tissue beneath the epithelium

its deeper portion often contains adipose tissue, particularly along the paths of the coronary arteries and cardiac veins that carry blood through the myocardium

the thick middle layer, or myocardium, consists mostly of cardiac muscle tissue that pumps blood out of the heart chambers

the muscle fibers are organized in planes separated by connective tissue richly supplied with ¹blood capillaries, ²lymph capillaries, and ³nerve fibers

the inner layer, or endocardium, consists of epithelium and connective tissue that contains many elastic and collagenous fibers

the endocardium also contains blood vessels and some specialized cardiac muscle fibers called Purkinje fibers

note: the endocardium is “continuous” with the inner linings of blood vessels that attach to the heart

Let’s Review! Where is the heart located? Illustrate your

description using the visualization of a growing flower against a garden fence.

Distinguish between the visceral pericardium and the parietal pericardium. Demonstrate your knowledge of these terms with an everyday example.

What is the myocardium? What is the endocardium? How do they function collectively to ensure efficient flow of blood?

List the four chambers of the heart starting with the right atrium.

5. _______ are the thicker chambers of the heart, which are sometimes called the discharging chambers.

6. The __________ are the thinner chambers of the heart, which are sometimes called the receiving chambers of the heart.

7. The ventricles of the heart are separated into right and left sides by the:

Internal Anatomy - Anterior

the heart acts as two separate pumps

the right atrium and the right ventricle perform a task quite different from the left atrium and left ventricle

when the heart “beats”, the atria contract simultaneously (atrial systole)

next, the ventricles fill with blood contracting together (ventricle systole)

Blood Flow Through The Heart(page 724 in your text)

blood enters the right atrium through two large veins called the superior and inferior vena cava

the right pump receives oxygen-poor blood from the veins ending systemic circulation and beginning pulmonary circulation

after coming into the right atrium, blood is pumped through the right AV, or tricuspid valve, before entering the right ventricle

when the ventricles contract, the blood in the right ventricle is pumped through the pulmonary semilunar valve into the pulmonary artery (remember… arteries away) and eventually to the lungs where oxygen is added and carbon dioxide lost

(turn to your neighbor & explain blood flow from the right atrium to the lungs)

blood rich in oxygen returns to the left atrium of the heart through the pulmonary veins

it then passes through the left AV, or bicuspid valve, into the left ventricle

when the left ventricle contracts, blood is forced through the aortic semilunar valve into the aorta before distribution to the body as a whole (ending pulmonary circulation and beginning systemic circulation)

(turn to your neighbor & explain blood flow from the lungs to your aorta)

Blood Flow Through Heart

using the worksheet of the heart provided by your instructor:

1. label the septums, chambers, pumps, and valves discussed earlier in this lecture

2. trace the flow of blood through the heart using a purple arrow for systemic circulation

and an orange arrow for pulmonary circulation

3. color your veins blue and your arteries red whilst accurately labeling them on the anterior

portion

the first two branches of the aorta, called the right and left coronary arteries, supply blood to the tissues of the heart

their openings lie just beyond the aortic valve

(open your textbook & highlight this structure on an illustration of the heart)

the heart must beat continually to supply blood to body tissues

to do this, myocardial cells require a constant supply of freshly oxygenated blood (O₂)

Blood Supply to the Heart

branches of the coronary arteries feed the many capillaries of the myocardium

the smaller branches, of these arteries, usually have connections (anastomoses / a-nas’ to-mos) between vessels that provide alternate pathways for blood called collateral circulation

these detours in circulation can supply oxygen and nutrients to the myocardium when a coronary artery is blocked

branches of the cardiac vein, whose paths roughly parallel those of the coronary arteries, drain blood that has passed through myocardial capillaries

these veins join an enlarged vein on the heart’s posterior surface called the coronary sinus

the coronary sinus then empties into the right atrium

(find these structures on an illustration in your textbook and highlight)

Let’s Review!

1. Review the path of blood through the heart. Can you verbally follow its course without referring back to your notes?

2. Which vessels supply blood to the myocardium?

3. How does blood return from the cardiac veins?

4. What role does genetic variability play in vessel distribution? In anatomical design? (i.e. the aorta)

5. Place these structures in the correct order from largest

to smallest: coronary sinus, coronary arteries, coronary veins, and capillaries.

Major Branches of the Aorta

Heart Action(page 731 in your text)

systolic is the active phase of the heart (contraction) beginning in the ventricles

it is the top number in relation to blood pressure

diastolic is the resting period of the heart (between contractions) beginning in the atriums

it is the bottom number in relation to blood pressure

both phases of the heart serves as a muscular pumping device for distributing blood to all parts of the body

Cardiac Cycle the beating of the heart is a regular and

rhythmic process

each complete heartbeat is called a cardiac cycle and includes the contraction (systole) and relaxation (diastole) of atria and ventricles

each cycle takes about 0.8 seconds to complete if the heart is beating at an average rate of about 72 beats per minute

the term stroke volume refers to the volume of blood ejected from the ventricles during each beat

cardiac output (CO), or the volume of blood pumped by one ventricle per minute, averages about 5 L in a normal resting adult

if the ventricles contract more forcefully, they expel more blood as a means of adjusting your cardiac output to increase in venous return (a homeostatic mechanism)

this principle is summarized by the Frank-Starling law of the heart (page 743 in your text)

sinus rhythm is set by the SA node at 60 – 100 BPM (beats per minute)

when an adult is at rest, vagal inhibition sets the sinus rhythm at 70 – 80 BPM

any premature ventricular contraction (PVC) can be caused by ¹hypoxia, ²electrolyte imbalance, ³stimulants, ⁴stress, and so on and so forth

(take a moment and define vagal)

Major Events of Cardiac Cycle

quiescent period¹

ventricular filling

isovolumetric contraction²

ventricular ejection

isovolumetric relaxation³

(Is “filling” systole or diastole?)

resistance opposes flow great vessels have

positive blood pressure ventricular pressure must

rise above this resistance for blood to flow into the great vessels

Principles of Pressure and Flow pressure causes a fluid to flow

◦pressure gradient is a pressure difference between two points (between high and low)

to sustain life, the heart must pump blood throughout the body on a regular and on-going basis

in order to do so, the heart muscle (or myocardium) requires a constant supply of blood containing nutrients and oxygen to function effectively

the delivery of this oxygen and nutrient-rich arterial blood to cardiac muscle tissue, besides the return of oxygen-poor blood from the venous system, is called coronary circulation

blood will also flow back into the heart muscle by way of two small vessels called the right and left coronary arteries which are the aorta’s first branches

Nerve Supply to Heart(page 728 in your text)

sympathetic nerves (activates) come from: ¹the upper thoracic spinal cord, ²through a sympathetic chain, ³to the cardiac nerves, and ³then directly to ventricular myocardiumthis process can raise heart rate to 230 bpm

parasympathetic nerves (deactivates / calms) come from: ¹the right vagal nerve, ²to the SA node, ³on to the left vagal nerve, and ⁴eventually ending up in the AV nodevagal tone normally slows heart rate to

70 – 80 bpm

Conduction System of the Heart(pages 728 – 729 in your text)

cardiac muscle fibers can contract rhythmically on their own: myogenic (originating within the heart) and autorhythmic (regular and spontaneously)

however, they must be coordinated by electrical signals (impulses) if the heart is to pump effectively

although the rate of the cardiac muscle’s rhythm is controlled by the autonomic nerve signals, the heart has its own built-in conduction system for coordinating contractions during the cardiac cycle

the most important thing to realize about this conduction system, however, is that all of the cardiac muscle fibers in each region of the heart are electrically linked together

actually, there are intercalated disks which act as these connectors… joining muscle fibers into a single unit to conduct impulses through the entire wall of the heart chamber without stopping

sub sequentially, both atrial walls will contract at about the same time because all of their fibers are electrically linked

likewise, both ventricular walls will contract at about the same time because of their fibers are electrically linked

Structure of Cardiac Muscleshort, branched cells, and one central nucleus

a sarcoplasmic reticulum and large T-tubules admit more Ca2+ from ECF

intercalated discs join myocytes end to endinterdigitating folds surface areamechanical junctions tightly join myocytes

desmosomeselectrical junctions (or gap junctions) allow

ions to flow more effectively

Structure of Cardiac Muscle Cell

four structures embedded in the wall of the heart are specialized to generate strong impulses which conduct them rapidly to certain regions of the heart wall

these structures ensure that the atria contracts first, before the ventricles contract, to increase overall efficiency of the heart

the names of these structures, that make up the conduction system of the heart, are the: ¹SA node, ²AV node, ³bundle of His, and the ⁴purkinje (pur-KIN-jee) fibers

(fibrous skeleton: insulates atria from ventricles)

the ¹sinoatrial node (SA node) is located in the upper wall of the right atrium initiating heartbeat

the SA node is commonly referred to as the “natural pacemaker” of the heart

the ²atrioventricular node (AV node) is located in the lower wall of the right atrium

the ³AV bundle or bundle of His found in the septum dividing the heart into right and left pumps

and finally, the ⁴Purkinje fibers located in the ventricular myocardium on the left side of the heart

(locate these structures in your text & highlight them)

specialized cardiac muscle cells, in the wall of the heart, rapidly conduct an electrical impulse throughout the myocardium

the signal is initiated by the SA node (natural pacemaker) and spreads to the rest of the atrial myocardium before moving on to the atrioventricular (AV) node

the AV node then initiates a signal that is conducted through the ventricular myocardium by way of the AV bundle of His and Purkinje fibers

(mark these structures on your heart diagram labeled earlier in class)

tachycardia results when the conduction system permits the heart to beat to fast

bradycardia results when the conduction system permits the heart to beat to slow

both are often associated with disturbances of both sinoatrial and atrioventricular conduction

(pages 741 – 742 in your text)

Cardiac Conduction System

Let’s Review!

1. Contraction of the heart is called:

2. Relaxation of the heart is called:

3. Describe the pressure changes in the atria

and ventricles during a cardiac cycle.

4. What causes heart sounds?

5. The term ______ refers to the volume of blood ejected from the ventricle during each beat.

6. The ________ is the pacemaker of the heart

and causes the contraction of the atria.

7. The _________ are extensions of the

atrioventricular fibers and cause the contraction of the ventricles.

8. Explain why a pressure difference must

exist between the aorta and the right atrium. Can you provide an everyday example to support your statement(s)?

Electrocardiogram(pages 733 – 736 in your text)

the specialized structures of the heart’s conduction system generate tiny electrical currents that spread through the surrounding tissues to the surface of the body

this fact is of great clinical significance because these electrical signals can be picked up from the body surface and transformed into visible tracings by an instrument called an electrocardiograph

the electrocardiogram (a.k.a. ECG / EKG) is the graphic record of the heart’s electrical activity

a normal ECG tracing has three very characteristic deflections or waves called the ¹P wave, the ²QRS complex, and the ³T wave

these deflections represent the electrical activity that regulates the contraction, or relaxation, of the atria and ventricles

the term depolarization describes the electrical activity that triggers contraction of the heart muscle

while the term repolarization begins just before the relaxation phase of cardiac muscle activity

(note: ST segment is ventricular systole)

Electrocardiogram (ECG) composite of all action potentials of nodal and myocardial

cells ¹detected, ²amplified, and ³recorded by electrodes on ¹arms, ²legs and ³chest

in a normal ECG, the small P wave occurs with depolarization of the ventricles, and the T wave results from electrical activity generated by repolarization of the ventricles

you may wonder why no visible record of atrial repolarization is noted in a normal ECG

the reason is simply that the deflection is very small and hidden by the large QRS complex that occurs at the same time

damage to cardiac muscle tissue, that is caused by a myocardial infarction or disease affecting the heart’s conduction system, results in distinctive changes in the ECG

therefore, ECG tracings are extremely valuable in the diagnosis and treatment of heart disease

in summary: when the heart wall is completely relaxed, with no change in activity, the ECG remains constant

P waves will occur when the AV node, and atrial walls, depolarize

when the atrial walls are completely depolarize, there will be no change recorded on the ECG

as for the QRS complex, it will occur as the atria repolarize and the ventricular walls depolarize

the atrial walls are now completely repolarized and the ventricular walls are now completely depolarized

consequently, no change is recorded on the ECG

when the T wave appears on the ECG, the ventricular walls have repolarized

once this is completed, the ventricles repolarize and you are once again at the baseline of the ECG

(create a flow chart of what one would see on a normal ECG recording)

Electrical Activity of Myocardium1) atrial

depolarization begins

2) atrial depolarization complete (atria contracted)

3) ventricles begin to depolarize at apex; atria repolarize (atria relaxed)

4) ventricular depolarization complete (ventricles contracted)

5) ventricles begin to repolarize at apex

6) ventricular repolarization complete (ventricles relaxed)

ECGs (normal and abnormal)

ECGs (abnormal)

extrasystole: note inverted QRS complex, misshapen QRS and T wave, plus absence of a P wave preceding this contraction.

ECGs (abnormal)

arrhythmia: conduction failure at AV node

no pumping action occurs

Read the handout, provided by your instructor, on performing an ECG.

Find your assigned partner. Between the two of you, decide who will be the “patient” and whowill be the “technician”.

If you are the “technician”, pleasetake a moment to explain the procedure to them. What can they expect, and why is the testbeing administered?

Hepatic Portal Circulation(page 797 in your textbook)

the term hepatic portal circulation refers to the route of blood flow through the liver

veins from the ¹spleen, ²stomach, ³pancreas, ⁴gallbladder, and ⁵intestines do not pour their blood directly into the inferior vena cava (as do the veins from other abdominal organs)

instead, they send their blood to the liver by means of the hepatic portal vein

the blood must pass through the liver before it re-enters the regular venous return to the heart

when blood eventually leaves the liver, by way of the hepatic veins, it drains into the inferior vena cava

normally, blood flows from arteries to arterioles to capillaries to venules to veins and back to the heart

such is not the case with the hepatic portal system

instead, venous blood is sent through a secondary capillary bed in the liver (one set in the digestive organs & the other in the liver)

afterwards, blood returns to its normal route

(can you illustrate this as a system of interstates & highways?)

the detour of venous blood through this secondary capillary bed serves some valuable purposes

for example when a meal is absorbed, the blood in the portal vein contains a higher-than-normal concentration of glucose (a form of sugar)

liver cells will remove this excess glucose and store it as glycogen

this ensures that blood leaving the liver has a normal blood glucose concentration

liver cells also remove and detoxify various poisonous substances (i.e. alcohol) that may be present in the blood

any detour in venous circulations allows an opportunity to “filter again” before going back into its usual route

this is why the hepatic portal system is an excellent example of how “structure follows function” in helping the body maintain homeostasis

Veins of Hepatic Portal System drains blood from viscera (stomach, spleen, and

intestines) to the liver so nutrients can be absorbed

Let’s Review

1. The ECG tracing that occurs when the ventricles depolarize is called the:

2. The ECG tracing that occurs when the atria depolarize is called the:

3. The ________ are the blood vessels that

carry blood back to the heart.

4. The _______ are the blood vessels that carry blood away from the heart.

5. The ___________ are the microscopic blood vessels where substances are exchanged between the blood and tissues.

6. Explain hepatic portal circulation, and what advantages are gained from this type of circulation.

6. The primary difference between pulmonary and systemic circulation.

7. Explain how the traces on an ECG relate to what is occurring in the heart.

8. Illustrate the path of the conduction system of the heart. Label the structures involved.

(hint: “ECG Format”)

blood pressure exists in the blood vessels

it is the highest in the arteries and lowest in the veins

this blood pressure “hill” is spoken of as the blood pressure gradient

more precisely, the blood pressure gradient is the difference between two blood pressures

Blood Pressure(pages 762 – 763 in your text)

the blood pressure gradient, for the entire systemic circulation, is the differences between the average (or mean) blood pressure in the aorta and the blood pressure at the termination of the vena cava where they join the right atrium of the heart

the blood pressure gradient is vital in keeping the blood flowing (a homeostatic mechanism)

when a blood pressure gradient is present, blood circulates

conversely when a blood pressure gradient is not present, blood does not circulate

in other words, there would no longer be a force to move blood into and out of the heart

this is why high or low blood pressure are not good for circulation

high blood pressure, for example, may cause rupturing of one or more blood vessels while low blood pressure can cause circulation and life to cease all together

factors that influence blood pressure are: ¹blood volume, the ²strength of heart contractions, ³heart rate, and ⁴blood viscosity (thickness)

BP Changes With Distance

Baroreflex (Negative Feedback Response)

importance of arterial elasticity◦¹expansion and ²recoil maintains steady flow of blood throughout cardiac cycle while “smoothing out” pressure fluctuations and stress on small arteries

with age, BP rises because arteries are generally less distensible / elastic

Blood Pressure

FLUCTUATIONS IN BLOOD PRESSURE(PAGES 766 – 769)

no one’s blood pressure stays the same all of the time

it fluctuates even in a perfectly healthy individual (i.e. goes up when one exercises or goes down when one is sleeping)

not only is this normal, but increased blood pressure brings more blood to muscles each minute

this supplies them with more oxygen ,and food for energy ,when needed

BLOOD FLOW IN RESPONSE TO NEEDS

arterioles shift blood flow with changing priorities

a normal average arterial blood pressure is about 120 / 80

however, that which is “normal” varies somewhat among individuals and with age

by and large, venous blood pressure is very low in the large veins and falls almost to 0 by the time blood leaves the vena cava in entering the right atrium

the venous blood pressure within the right atrium is called the central venous pressure

5 mechanisms help to keep venous blood moving back through the circulatory system and into the right atrium: continued beating of the heart, adequate blood pressure, semilunar valves, contraction of skeletal muscles, and changing pressure in the chest cavity during breathing

SKELETAL MUSCLE PUMP

Pulse(pages 741 – 743 in your text)

what you feel when you take a pulse is an artery expanding and then recoiling alternately

to feel a pulse, you must place your fingertips over an artery that lies near the surface of the body and over a bone or other firm base

the pulse is a valuable clinical sign that can provide information about the ¹rate, ²strength, and ³rhythmicity of the heartbeat

it can also be detected easily with little or no danger / discomfort to the patient

there are 9 major pulse points on your own body:

1. superficial temporal artery2. facial artery3. carotid artery (neck)4. axillary artery (inside of arm near pit)5. brachial artery (inside of arm above elbow)

6. radial artery7. femoral artery (inside of thigh near groin)8. popliteal (posterior to patella)9. dorsalis pedis (anterior tibial artery after crossing the ankle)

Let’s Review!

1. The strength of the heart contraction, and blood volume, are two factors that influence blood pressure. Two other factors that influence blood pressure are:

2. Identify 5 mechanisms that keep the venous blood moving toward the right atrium.

3. Name four locations, in the body, where the pulse can be felt. Demonstrate at least two of these pulse points on a neighbor. (please obtain permission first)

4. Place the following structures in their proper order as blood flows through the heart: left atrium, tricuspid valve, right ventricle, pulmonary vein, aortic semilunar valve, mitral valve, left ventricle, pulmonary artery, right atrium, and pulmonary semilunar valve.

Let’s Review Continued!

1. The Frank-Starling law of the heart explains why the ________ of the left ventricle is the same as that of the right ventricle.

2. The death of cardiac tissue from lack of blood flow is commonly known as a heart attack, but clinically called:

3. The _____ nerve(s) tend to innervate the heart and reduce overall rate.

4. Cardiac muscle does not exhibit tetanus because it has:

5. A heart rate of 45 BPM, and an absence of P waves, suggest:a) damage to the SA nodeb) ventricular fibrillationc) extrasystoled) heart block

6. To get from the right atrium to the right

ventricle, blood flows through this valve:

7. A person with a systolic blood pressure of

130 mm Hg and a diastolic pressure of 85 mm Hg would have a mean arterial pressure of about:

a) 85 mm Hg b) 100 mm Hg

c) 108 mm Hg d) 115 mm Hg

e) 130 mm Hg

8. Intestinal blood flows to the liver by way of:

9. Where the internal and external jugular veins are located within the body:

10. Where the subclavian artery is located within the body:

Please review the following lecture slides on your own.

Thank-you,

Mrs. Hiller Kellner

Systemic and Pulmonary Circulation(pages 716 – 717 in your text)

the term “circulation of blood” is self-explanatory, meaning the blood flows through vessels that are arranged to form a circuit or circular pattern

blood flow from the left ventricle of the heart, through blood vessels, to all parts of the body, and back to the right atrium of the heart is described as systemic circulation

in comparison, pulmonary circulation moves venous blood from the right atrium, to the right ventricle, to the pulmonary arteries, to lung arterioles, to lung capillaries where an exchange of gases occurs (turning the blood from deep crimson to scarlet)

this oxygenated blood then flows back through lung venules into the four pulmonary veins, and returning to the left atrium of the heart before moving on to the left ventricle to be pumped again through systemic circulation

Pulmonary Capillaries Near Alveoli

basketlike capillary beds surround alveoli

here, an exchange of internal gases with external air occurs at the alveoli

in both coronary thrombosis and coronary embolism, a blood clot occludes (or plugs up) some part of the coronary artery

blood can not pass through the occluded vessel and so cannot reach the heart muscle cells it normally supplies

deprived of oxygen, these cells soon die or are damaged

in medical terms, a myocardial infarction occurs (tissue death)

Diseases & Disorders of the Circulatory System

myocardial infarction (a.k.a. heart attack) is a common cause of death during middle and late adulthood often due to lifestyle factors

recovery from myocardial infarction is possible if the amount of heart tissue damaged was small enough so that the remaining heart muscle can pump blood effectively enough to supply the rest of the heart and body

the term angina pectoris is used to describe the severe chest pain that occurs when the myocardium is deprived of adequate oxygen

it is often a warning sign that the coronary arteries are no longer able to supply enough blood and oxygen

coronary bypass surgery (a.k.a. CABG) is a frequent treatment for those who suffer from severely restricted coronary artery blood flow

in this procedure, veins or arteries are “harvested” (removed) from other areas of the body and used to bypass partial blockages

another treatment to improve blood flow is angioplasty

angioplasty is a procedure in which a device is inserted into a blood vessel to open a channel for blood flow