Download The Heart

Biology 212
Anatomy & Physiology I
The Heart
Heart:
Mass: 250-300 g
Located in center of
thorax (mediastinum)
Anterior to vertebrae
Posterior to sternum &
2nd through 6th rib
Superior to diaphragm
Surrounded by lungs
All vessels, nerves, etc. enter or leave superior end ("base")
Layers of Heart:
(Outer Surface) Epicardium - Thin, connective tissue
Myocardium - Thick, cardiac muscle
(Inner Surface)
Endocardium - Thin, connective tissue
Simple squamous epithelium
lines inner surface, next to blood
Myocardium: Cardiac Muscle
Heart surrounded by double-layered pericardium
Visceral Layer
Parietal Layer
Serous Pericardium
Visceral Layer
Parietal Layer
Heart
Pericardial
Cavity
Heart surrounded by double-layered pericardium
Heart
Fibrous Pericardium
Serous Pericardium
Visceral Layer
Parietal Layer
Heart
Pericardial
Cavity
Anterior View
Left Atrium
Right Atrium
Left Ventricle
Right Ventricle
Anterior View
Aorta
Superior
Vena Cava
Inferior
Vena Cava
Pulmonary
Trunk
Anterior View
Left
Atrioventricular
Sulcus
Right
Atrioventricular
Sulcus
Anterior
Interventricular
Suclus
Posterior View
Left Atrium
Right Atrium
Right Ventricle
Left Ventricle
Posterior View
Left
Atrioventricular
Sulcus
Right
Atrioventricular
Sulcus
Posterior
Interventricular
Suclus
Posterior View
Aorta
Superior
Vena Cava
Pulmonary
Arteries
Inferior
Vena Cava
Pulmonary
Veins
Left
Coronary
Artery
Right
Coronary
Artery
Marginal
Coronary
Artery
Circumflex
Coronary
Artery
Anterior
Interventricular
Coronary
Artery
Circumflex
Coronary
Artery
Right
Coronary
Artery
Posterior
Interventricular
Coronary
Artery
Anterior
Cardiac
Veins
Small
Cardiac
Vein
Great
Cardiac
Vein
Great
Cardiac
Vein
Small
Cardiac
Vein
Middle
Cardiac
Vein
Coronary
Sinus
Valves of the Heart:
Right Atrioventricular Valve
(Tricuspid valve)
Right Atrium to Right Ventricle
Valves of the Heart:
Right Atrioventricular Valve
Pulmonary Valve
(Right semilunar valve)
Right Ventricle to
Pulmonary Trunk
Valves of the Heart:
Right Atrioventricular Valve
Pulmonary Valve
Left Atrioventricular Valve
(Bicuspid or Mitral valve)
Left Atrium to Left Ventricle
Valves of the Heart:
Right Atrioventricular Valve
Pulmonary Valve
Left Atrioventricular Valve
Aortic Valve
(Left semilunar valve)
Left Ventricle to
Ascending Trunk
Valves of the Heart:
Right Atrioventricular Valve
Pulmonary Valve
Left Atrioventricular Valve
Aortic Valve
Note: There are no valves controlling movement of blood
a) From superior or inferior vena cavae into right atrium
b) From pulmonary veins into left atrium
Sinoatrial Node
Atrioventricular
Node
Atrioventricular
Bundle (of His)
Bundle Branches
Purkinje fibers
Cardiac myocytes spontaneously depolarize:
Na+ constantly leaks into the cells, decreasing the
voltage until threshold voltage is reached
Thereafter: contraction similar to what we discussed for
skeletal muscle:
Cardiac myocytes spontaneously depolarize:
Na+ constantly leaks into the cells, decreasing the
voltage until threshold voltage is reached
Thereafter: contraction similar to what we discussed for
skeletal muscle:
Action potential moves
+
++
Na / Ca gates open
along sarcolemma and
+
++
Na and Ca flow into myocyte into the cell through
K+ flows out of myocyte
transverse tubules
Sarcoplasmic reticulum
releases Ca++ which binds onto thin myofilaments
Actin binding sites uncovered, form cross bridges with
myosin of thick myofilament
Contraction of the heart (or any one of its chambers) is
Systole
Relaxation of the heart (or any one of its chambers) is
Diastole
One systole followed by one diastole is one
Cardiac Cycle
Flow of blood through the heart is controlled entirely by
changes in pressure.
Blood always flows along its pressure gradient, from the
area of higher pressure to an area of lower pressure.
The open or closed position of a valve depends entirely
on the difference in pressure from one side to the other:
The higher pressure pushes the valve open or closed,
Assume the chambers of the heart and vessels have the
following pressures:
Left ventricle = 115 mm Hg
Right ventricle = 5 mm Hg
Pulmonary trunk = 22 mm Hg
Superior vena cava = 2 mm Hg
Inferior vena cava = 2 mm Hg
Left atrium = 20 mm Hg
Right atrium = 10 mm Hg
Aorta = 125 mm Hg
Which valves of the heart will be open?
Which valves of the heart will be closed?
Terms to know:
Heart rate: The number of cardiac cycles per minute
Stroke volume: Volume of blood ejected from a
ventricle during a single systole.
Cardiac Output: Volume of blood pumped by a ventricle
in one minute
= (Heart rate) x (Stroke volume)
Cardiac Index: Volume of blood pumped by a ventricle per
minute per square meter of body surface
Given the following information:
a) Dr. Thompson's total blood volume is 5.8 liters
b) His heart ejects 75 ml of blood per contraction
c) His kidneys produce 320 ml of urine per hour
d) All of his wisdom teeth have been removed
e) His heart contracts 70 times per minute
f) His systolic blood pressure is 130 mmHg
g) His diastolic blood pressure is 80 mmHg
h) The pressure in his left ventricle changes between
1 mmHg and 133 mmHg during each cardiac cycle
Calculate his Heart Rate
Stroke Volume
Cardiac Output
Therefore: You can regulate your cardiac output, and
therefore your cardiac index, by:
a) Increasing or decreasing your heart rate
b) Increasing or decreasing your stroke volume
In fact: Your ventricles modify both heart rate and stroke
volume on a beat-by-beat basis.
This depends on how much the cardiac muscle cells are
stretched during the preceding diastole, which itself
depends on the volume of blood in the chamber
= Frank-Starling Law of Cardiac Contraction