Download Cardiovascular System

Cardiovascular System
THE HEART
The Heart
 Size: “fist size”
250 grams in females
 350 grams in males

 Location:
 Medial cavity of the thorax
 2/3 lies to the left of the sternum
The Heart
 Base: widest part posterior
 Superior surface- 9 cm wide, directed toward the right
shoulder
 Apex- directed inferiorly toward left hip
 Rests on diaphragm
 Point of Maximum Intensity: PMI
 Site where the apex is against the chest wall, between 5th and
6th rib.
Pericardium
Pericardium: double-walled fibersernous sac
membrane which:
1. encloses the heart
2. anchors the heart
Pericardium
Fibrous Pericardium
Serous Pericardium
 Tough dense
 Thin slippery
connective tissue.
 Protects and anchors
heart to sternum,
diaphragm, and major
vessels the enter and
exit
 Prevents over
distension of heart
membrane

Parietal layer:
Lines fibrous pericardium
 Pericardial Cavity: space
filled with pericardial fluid
(prevents friction)


Visceral Pericardium
Lines surface of heart,
connective tissue
Wall of Heart
Epicardium- composed of serous tissue and
mesothelium outer thin layer
2. Myocardium- composed of cardiac muscle tissue1.
1.
2.
Bulk of heart- layer that contracts (involuntary)
Cells are tethered together by a layer of fiberous tissue that
crosses
3. Endocardium- a glistening white sheet of
endothelium resting on a layer of connective tissue.
1.
2.
Lines heart chambers
Continuous over valves and throughout vascular system.
Heart Chambers
Atria
Ventricles
2 Atria (atrium) receive blood
from veins
2 ventricles – pumping
organs
Auricle: an appendage that
increases the atria’s volume
capacity.
– Pectinate muscles: muscle
bundles that run parallel to one
another and allow atrium to
expand and contract.
– Interatrial Septum:
divides right and left atrium
Foramen ovalis- opening between
atria before birth- closes at birth
and forms the fossa ovale (a dent)
–



Right Ventricle: pumps to
the lungs
Left Ventricle: pumps to the
systemic circulation
Interventricular Septum:
Divides the left and right
ventricles
Structure of the Heart
Grooves on the Surface
 Atrialventricular groove


Coronary Sulcus
Encircles juncitino of atria
and ventricles
 Anterior Interventricle
Sulcus:

Marks the anterior portion
of the interventricular
septum

Sulci: contains coronary
blood vessels and fat
Heart Valves
 Atrioventricular Valves
(AV)



Prevent back flow into the
atria during ventricular
contraction
Right Atrioventricular
Valve (tricuspid)
Left Atrioventricular Valve
(bicuspid, mitrovalve)
 Semilunar Valves



Prevent back flow into the
ventricles
Aortic Semilunar- left side
Pulmonary Semilunarright side
Heart Structure
Blood Flow
Path of Nerve Impulse Through Heart
1.
Sinoatrial node (SA Node) (Pacemaker)
Mass of nerve tissue in right atrial wall near opening of superior
vena cava- connected to medulla oblongata
2. Down the atria
3. Atrioventricular node collects
4. Passed to bundle of HIS in interventricular septum
5. Down Perkengie Network to Apex
6. Up across Ventricle – out of artery
The Heartbeat
The Conducting
System of the Heart
PLAY
The Heart:
Conduction System
Figure 12-9(a)
SA node activity and atrial
activation begin.
SA node
Time = 0
Stimulus spreads across the atrial
surfaces and reaches the AV node.
AV node
Elapsed time = 50 msec
There is a 100-msec delay at the
AV node. Atrial contraction begins. AV bundle
Bundle branches
Elapsed time = 150 msec
The impulse travels along the interventricular
septum within the AV bundle and the bundle
branches to the Purkinje fibers.
Elapsed time = 175 msec
The impulse is distributed by Purkinje fibers
and relayed throughout the ventricular
myocardium. Atrial contraction is completed,
and ventricular contraction begins.
Elapsed time = 225 msec
Purkinje fibers
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
Figure 12-9(b)
1 of 6
 An Electrocardiogram
Figure 12-10
Nervous Control of Heart Rate
1. Cardiac Acceleratory Centerincreased heart rate- connected to S.A. node by cervical
sympathetic ganglion
2. Cardiac Inhibitory CenterVagus Nerve- decreases
3. Bainbridge Reflexincreases HR due to an increased flow of blood back to heart
because of exercise
4. Aortic Arch Reflexdecreased HR due to increase of blood pressure in aorta
5. Carotid Sinuscan increase HR when Blood Pressure drops or decrease HR
when blood pressure rises
Chemical Controls
 Epinephrine: speeds up
 Noradrenaline: speeds up
 Thoroxyine: speeds up
 Sodium: speeds up, Potassium: slows down
 Calcium: speeds up
 Nicotine: speeds up initially, then slows down
Cardiac Cycle
2 atria contract (ventricles relax)
2. 2 ventricles contract (atria relax)
1.
Systole- contraction (chamber empties)
Diastole- chamber filling (relaxation)
Normal 120/80
Average cardiac cycle takes .8 seconds
(a) Atriole systole begins:
Atrial contraction forces
a small amount of additional
blood into relaxed ventricles.
START
(f) Ventricular diastole—late:
All chambers are relaxed.
Ventricles fill passively.
800
msec
0
msec
100
msec
Cardiac
cycle
(e) Ventricular diastole—early:
As ventricles relax, pressure
in ventricles drops; blood
flows back against cusps of
semilunar valves and forces
them closed. Blood flows
into the relaxed atria.
370
msec
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings
(b) Atriole systole ends
atrial diastole begins
(c) Ventricular systole—
first phase: Ventricular
contraction pushes AV
valves closed but does
not create enough pressure
to open semilunar valves.
(d) Ventricular systole—
second phase: As ventricular
pressure rises and exceeds
pressure in the arteries, the
semilunar valves open and
blood is ejected.
Figure 12-11
1 of 6
 Stroke Volume:
 Amount of blood ejected from one ventricle in one contraction
(80 ml)
 Cardiac Output:
 Amount of blood leaving heart in one minute
CO = (HR) (SV)