Circulatory System 19.1-19.2

transcript

THE HEART

H E AT H E R L D R A K EN E W Y O R K C H I R O P R A C T I C C O L L E G E , 2 0 1 3

S A L A D I N, “ U N I T Y O F F O R M A N D F U N C T I O N ”

The Circulatory System

OVERVIEW

Objectives

Define and distinguish between the pulmonary and systemic circuits

Describe the general location, size, and shape of the heart

Describe the pericardial sac that encloses the heart

PULMONARY and SYSTEMIC CIRCUITS

Cardiovascular System Consists of the heart and the blood vessels that carry

the blood to and from the body’s organs

2 major divisions Pulmonary circuit Systemic circuit

2 DIVISIONS

Pulmonary Circuit Carries blood to the lungs for gas exchange and returns it to the heart

The right side of the heart serves the pulmonary circuit Receives blood that has circulated throughout the body, unloaded its oxygen

and nutrients, and picked up a load of carbon dioxide/other wastes.

Pumps into the pulmonary trunk, which divides into right and left pulmonary arteries, transporting into alveoli, carbon dioxide unloaded/oxygen loaded.

Oxygen-rich blood then flows via pulmonary veins to the left side of the heart

Systemic Circuit Supplies blood every organ of the body, including other parts of the

lungs and wall of the heart itself

Pulmonary Circuit

Right side of the heart serves the pulmonary circuit

Superior/inferior vena cava

Right atrium Tricuspid valve Right ventricle Pulmonic semilunar

valves Pulmonary artery Lungs for gas

exchange Pulmonary vein Aortic semilunar

valves Left atrium Mitral valve Left ventricle Ascending aorta Aortic arch Body

2 DIVISIONS

Pulmonary Circuit Carries blood to the lungs for gas exchange and returns

it to the heartSystemic Circuit

Supplies blood every organ, including wall of the heart itself

Blood leaves the left side of the heart via the aorta, taking an inverted U-turn, the aortic arch, and passes downward, dorsal to the heart

Systemic Circuit

Supplies blood every organ of the body, including other parts of the lungs and wall of the heart itself

Blood leaves the left side of the heart via the aorta, taking an inverted U-turn, the aortic arch, and passes downward, dorsal to the heart

Fig. 19.1b

Aortic arch gives off arteries that supply the head, neck, and upper limbs.

The aorta then travels through the thoracic & abdominal cavities and gives off arteries to the organs

O2-poor,CO2-richblood

O2-rich,CO2-poorblood

Systemic circuit

Systemic Circuit

Supplies:

- Every organ

- Heart muscle

- Parts of the lungs

Systemic Circuit

After circulating through the body, the now-deoxygenated systemic blood returns to the right side of the heart mainly via:

Superior vena cava (draining the head, neck, upper limbs and thoracic organs)

Inferior vena cava (drains organs below the diaphragm)

Fig. 19.1

Putting it all together

Pulmonary AND Systemic Circuits

Pulmonary circuit

O2-poor,CO2-richblood

O2-rich,CO2-poorblood

Systemic circuit

POSITION of the HEART

Base – broad superior portion

of heart – point of attachment

for the great vessels

Apex – the inferior end tapers

to a blunt point

Superiorvena cava

Right lung

Parietalpleura (cut)

Pericardialsac (cut)

Pulmonarytrunk

Baseofheart

Apexof heart

Diaphragm(c)

Fig. 19.2b

Posterior

Pericardialcavity

Leftventricle

Interventricularseptum

Rightventricle

Thoracicvertebra

Position of Heart

Fig. 19.2a

Thoracic cavity in the mediastinum and deep to the sternum

Tilted towards the left – 2/3 of heart is in left of median

Sternum

3rd rib

Diaphragm

THE PERICARDIUM

Pericardium - heart is enclosed in a double-walled sac

Parietal pericardium – the outer wall has a tough, superficial fibrous layer

Serous layer – turns inward at the base of the heart and forms the visceral pericardium (epicardium) covering the heart surface

Fig. 19.3a

Pericardialcavity

Myocardium

Endocardium

Epicardium

Pericardial sac

Pericardialcavity

Pericardialsac:

Fibrouslayer

Serouslayer

Epicardium

PERICARDITIS

inflammation of the pericardium –

membrane becomes dry and produces a painful friction rub

Pericardial cavity – space between the parietal and visceral membranes, contains pericardial fluid – Allows the heart to beat

without friction

1. Distinguish between the pulmonary and systemic circuits and state which part of the heart serves each one

2. Make a two color sketch of the pericardium;

1. Use one color for the fibrous pericardium and another for the serous pericardium and another for the serous pericardium and show their relationship to the heart wall and pericardial activity

GROSS ANATOMY OF THE HEART

OBJECTIVES Describe the 3 layers of the heart wall

Identify the four chambers of the heart

Identify the surface features of the heart and correlate them with its internal four-chambered anatomy

Identify the four valves of the heart

Trace the flow of blood through the four chambers of the heart and adjacent blood vessels

Describe the arteries that nourish the myocardium & veins that drain it

HEART WALL

3 layers: Epicardium

Myocardium

Endocardium

HEART WALL

Epicardium Thin, serous layer that

covers external surface

Consists mainly of a simple squamous epithelium overlaying thin aereolar tissue

Some locations also include thick layer of adipose tissue

Some locations thin and transluscent to show myocardium

Myocardium of the Heart

Myocardium

Thick, muscular middle layer – composed of cardiac muscle

Thickest layer – performs the work of the

Thickness is proportional to the workload on the individual chambers

Muscle spirals around the heart, so when the ventricles contract, they exhibit a twisting/wringing motion

Endocardium of the Heart

Endocardium

Thin layer lining the inside of the chambers

Simple squamous endothelium overlaying thin aereolar tissue

Has no adipose tissue

Covers the valve surfaces and is continuous with the endothelium of the bl vessels

ANIMATION OF BLOOD FLOW THROUGH HEART

http://www.wellesley.edu/Biology/Courses/111/AdultHeart.gif

1Blood enters right atrium from superiorand inferior venae cavae.

Superiorvena cava

Rightpulmonaryveins

Rightatrium

Right AV(tricuspid) valve

Rightventricle

Inferiorvena cava

Left pulmonaryartery

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Left AV(bicuspid) valve

Aortic valve

Left atrium

Blood in right atrium flows through rightAV valve into right ventricle.

Superiorvena cava

Rightpulmonaryveins

Rightatrium

Rightventricle

Inferiorvena cava

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

Contraction of right ventricle forcespulmonary valve open.

Superiorvena cava

Rightatrium

Rightventricle

Inferiorvena cava

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

Rightpulmonaryveins

Blood flows through pulmonary valveinto pulmonary trunk.

Superiorvena cava

Rightatrium

Rightventricle

Inferiorvena cava

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

Rightpulmonaryveins

Blood is distributed by right and leftpulmonary arteries to the lungs, where itunloads CO2 and loads O2.

Superiorvena cava

Rightatrium

Rightventricle

Inferiorvena cava

Pulmonary trunk

Left pulmonaryveins

Aortic valve

Left atrium

Rightpulmonaryveins

Left ventricle

Blood returns from lungs via pulmonaryveins to left atrium.

Superiorvena cava

Rightpulmonaryveins

Rightatrium

Rightventricle

Inferiorvena cava

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

Blood in left atrium flows through left AVvalve into left ventricle.

Superiorvena cava

Rightpulmonaryveins

Rightatrium

Rightventricle

Inferiorvena cava

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

Superiorvena cava

Rightpulmonaryveins

Rightatrium

Rightventricle

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

Contraction of left ventricle (simultaneous withstep 3 ) forces aortic valve open.

Blood flows through aortic valve intoascending aorta.

Superiorvena cava

Rightpulmonaryveins

Rightatrium

Rightventricle

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

Blood in aorta is distributed to every organ inthe body, where it unloads O2 and loads CO2.

Superiorvena cava

Rightpulmonaryveins

Rightatrium

Rightventricle

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

Blood in aorta is distributed to every organ inthe body, where it unloads O2 and loads CO2.

Blood returns to heart via venae cavae.

Superiorvena cava

Rightpulmonaryveins

Rightatrium

Rightventricle

Inferiorvena cava 11

Pulmonary trunk

Left pulmonaryveins

Left ventricle

Aortic valve

Left atrium

HEART – FIBROUS SKELETON

Has a meshwork of collagenous and elastic fibers that make up a fibrous skeleton

Fibrous rings have multiple functions: Structural support for heart, esp around valves and

openings of great vessels

Anchors the myocytes and gives them something to pull against

Serves as electrical insulation b/w atria and ventricles, so the atria cannot stimulate the ventricles directly

Elastic recoil aids in refilling the heart

THE 4 CHAMBERS

Superior Chambers Right atria Left atria

Receiving chambersfor blood returningto the heart

Inferior chambers: Right ventricle Left ventricle

The pumps that ejectblood into the arterieskeep it flowingaround body

VALVES – Atrioventricular Valves

A). Atrioventricular (AV) Valves Located between the

atria and the ventricles Flaps consist of

connective tissue & endocardium.

They are attached to collagen cords called chordae tendinae. 1). Tricuspid 2). Bicuspid or Mitral

VALVES – Semilunar Valves

B). Semilunar (SL) Valves Lead into the large

arteries

Formed from 3 moon-shaped cusps

1). Aortic Semilunar Valve

2). Pulmonary Semilunar Valve

BLOOD FLOW – AV Valves - STEP 1

When the heart is relaxed, the AV flaps hang open

BLOOD FLOW – AV Valves – STEP 2

When the ventricles contract the AV valves are pressed closed from the ventricular side.

Blood is pushed against the AV valve which closes and it pushes against the SL valve which opens

BLOOD FLOW – Semilunar Valves - STEP 1

When the ventricle relaxes blood pressure is higher in the vessels, which closes the SL valve

BLOOD FLOW – Semilunar Valves – STEP 2

BLOOD FLOW THROUGH THE HEART

1. Blood enters right atrium from superior and inferior venae cavae

2. Blood in the right atrium flows through right AV valve into the right ventricle

3. Contraction of right ventricular forces pulmonary valve open

4. Blood flows through pulmonary valve into pulmonary trunk

5. Blood is distributed by right and left pulmonary arteries to the lungs, where it unloads CO2 and loads O2

6. Blood return from lungs via pulmonary arteries to left atrium

7. Blood in left atrium flows through left AV valve into left ventricle

8. Contraction of left ventricle (simultaneous with step 3) forces aortic valve open

9. Blood flows through the aortic valve into ascending aorta

10. Blood in aorta is distributed into every organ in the body, where it unloads O2 and loads CO2

11. Blood returns to heart via venae cavae

QUIZ TIME

Trace the pathway of a single erythrocyte from the inferior vena cava to the aortic arch, naming each vessel and structure it passes through, and noting when it is oxygenated, and when it is deoxygenated.

CORONARY ARTERY BLOOD FLOW

QUIZ QUESTION

Trace the path of a single erythrocyte from the aorta to the posterior apex of the heart, if the right coronary artery is blocked at just after its attachment to the aorta?

How would the left anterior portion of the heart receive blood supply with the same blockage?

This theory is called COLLATERAL CIRCULATION The flow of blood to an area via an alternative route via vessel

anastomoses

CLINICAL CORRELATION

What if multiple coronary arteries were clogged? So much that there was not enough blood to fuel the heart?

Angina pectoris chest pain/pressure due to temporary ischemia

deficiency of blood to cardiac muscle

O2 deprived myocardium shits to anaerobic fermentation, producing lactic acid, which stimulates pain receptors in the heart.

MYOCARDIAL INFARCTION (MI) – heart attack

VENOUS DRAINAGE

Refers to the route by which blood leaves an organ.

20% of coronary blood empties directly into multiple small thebesian veins into the right atrium/ventricle

VENOUS DRAINAGE

80% returns to the right atrium via this route:

Great cardiac vein – Collects blood from anterior heart,

travels w.anterior interventric artery

Carries blood from apex to coronary sulcus, arcs left, empties into coronary sinus

Posterior interventricular (middle cardiac) vein Collects bl from posterior aspect of

Left marginal vein Travels from apex up left margin,

empties into coronary sinus

Coronary sinus Large transverse vein in coronary

sulcus, empties blood into right atrium

3. Name the three layers of the heart and describe their structural differences

4. What are the functions of the fibrous skeleton?

5. Trace the flow of blood through the heart, naming each chamber and valve in order

6. What are the three principle branches of the left coronary artery? Where are they located on the heart surface? What are the branches of the right coronary artery, and where are they located?

7. What is the medical significance of the anastamoses in the coronary arterial system?

8. Why do the coronary arteries carry a greater blood flow during ventricular diastole than they do during ventricular systole?

9. What are the three major veins that empty into the coronary sinus?

CARDIAC CONDUCTION SYSTEM and CARDIAC MUSCLE

OBJECTIVES: Describe the nerve supply to the heart

Describe the internal electrical system of the heart

Describe the unique structural and metabolic characterisitic of cardiac muscle

Explain the nature and functional significance of the intercellular junctions between cardiac muscle cells

Heart contracts at regular intervals (obviously) Typically 75bpm

Invertebrates (clames, crabs, insects, etc) have heartbeat triggered by a pacemaker in the nervous system

Vertebrates (us) is myogenic Signal originates within the heart itself

NERVE SUPPLY TO THE HEART

Heart has its own pacemaker, but it does receives sympathetic and parasympathetic nerves, modifying the heart rate and contraction strength

Sympathetic stimulation may raise HR to 230 bpm.

Parasympathetic stimulation can slow the HR as low as 20 bpm, or even stop for a few seconds.

Sympathetic pathway originates w.neurons in the lower cervical/upper thoracic spinal cord

Efferent fibers from these neurons pass from the spinal cord to the sympathetic chain and travel up the chain to the 3 cervical ganglia

Cardiac nerves arise from these ganglia, and lead to the myocardium, increasing force of contraction

Some fibers innervate the atria

Sympathetic fibers to the coronary arteries dilate them and increase coronary blood flow to the coronary arteries during exercise

Parasympathetic pathway to the heart is through the vagus nerves

RIGHT VAGUS nerve innervates mainly an electrical center of the heart – SA node

LEFT VAGUS nerve innervates the AV node

Ventricles receive little or no vagal stimulation

Vagus nerve slows the heartbeat. W.o this influence, the average resting HR would be 100 bpm Steady firing of the vagus nerve, VAGAL TONE, holds resting HR down to 70-80 bpm

IN SHORT – Sympathetic nerves do NOT make the heart beat, they only MODIFY it.

CONDUCTION ANIMATION

http://en.wikipedia.org/wiki/File:ECG_Principle_fast.gif

SA node fires.

Purkinje fibers

Atrioventricularbundle

Atrioventricularnode

Sinoatrial node(pacemaker)

Right atrium

Bundlebranches

Leftatrium

Purkinjefibers

SA node fires.

Excitation spreads throughatrial myocardium.

Purkinje fibers

Right atrium

Bundlebranches

Leftatrium

Purkinjefibers

SA node fires.

AV node fires.

Purkinje fibers

Right atrium

Bundlebranches

Leftatrium

Purkinjefibers

SA node fires.

AV node fires.

Excitation spreads down AVbundle.

Purkinje fibers

Right atrium

Bundlebranches

Leftatrium

Purkinjefibers

SA node fires.

AV node fires.

Excitation spreads down AVbundle.

Purkinje fibers distributeexcitation throughventricular myocardium.

Purkinje fibers

Right atrium

Bundlebranches

Leftatrium

Purkinjefibers

0 .8.4

1.61.2

Time (seconds)

Pacemakerpotential

Actionpotential

Threshold

outflow

Slow Na+

inflow

Ca2+–Na+

inflow

Fig. 19.14-1

Voltage-gated Na+ channels open.1

Time (seconds)

Absoluterefractory

period

Fig. 19.14-2

Voltage-gated Na+ channels open.

Na+ inflow depolarizes the membraneand triggers the opening of still more Na+channels, creating a positive feedbackcycle and a rapidly rising membrane voltage.

Time (seconds)

Absoluterefractory

period

Myocardialcontraction

Fig. 19.14-3

Na+ channels close when the celldepolarizes, and the voltage peaks atnearly +30 mV.

Time (seconds)

Absoluterefractory

period

Actionpotential

Fig. 19.14-4

Ca2+ entering through slow Ca2+

channels prolongs depolarization ofmembrane, creating a plateau. Plateau fallsslightly because of some K+ leakage, but mostK+ channels remain closed until end ofplateau.

Plateau

Time (seconds)

Absoluterefractory

period

Actionpotential

Fig. 19.14

Ca2+ entering through slow Ca2+

channels prolongs depolarization ofmembrane, creating a plateau. Plateau fallsslightly because of some K+ leakage, but mostK+ channels remain closed until end ofplateau.

Ca2+ channels close and Ca2+ is transportedout of cell. K+ channels open, and rapid K+

outflow returns membrane to its restingpotential.

Plateau

Myocardialrelaxation

Time (seconds)

Absoluterefractory

period

Actionpotential

Fig. 19.15a

0.8 second

Atriacontract

Ventriclescontract

Atriacontract

Ventriclescontract

STsegment

PQsegment

QRS interval

T waveP wave

PRinterval

QTinterval

0.8 second

Atriacontract

Ventriclescontract

Atriacontract

Ventriclescontract

STsegment

PQsegment

QRS interval

T waveP wave

PRinterval

QTinterval

Absolute versus Relative Refractory

Wave ofdepolarization

Wave ofrepolarization

Atria begin depolarizing.

Wave ofdepolarizationWave ofrepolarization

Atrial depolarization complete.

Ventricular depolarization begins at apex andprogresses superiorly as atria repolarize.

Ventricular depolarization complete.

Ventricular repolarization begins at apex andprogresses superiorly.

Ventricular repolarization complete; heart isready for the next cycle.

Ventricular repolarization begins at apex andprogresses superiorly.

So why does this matter?

Table 19.1

SOURCES

http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/APIINotes5%20Anatomy%20of%20the%20Heart.htm

http://www.nhlbi.nih.gov/health/health-topics/images/pericarditis.jpg

http://o.quizlet.com/i/MYYoBudMtF4Nd4VX8VXZ5w_m.jpg

http://stevegallik.org/sites/histologyolm.stevegallik.org/images/heartwall.gif

Saladin, K. “Anatomy and Physiology: The Unity of Form and Function.”4th ed. Philadelphia. McGraw Hill Publishing.

http://www.unm.edu/~jimmy/refractory_periods.jpg

Circulatory System 19.1-19.2

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