Systemic circulation
The two largest veins of
the body superior and inferior vena cava, empty their content into the right
atrium. The blood passes through the right atrioventricular valve into the
right ventricule and from there it is pumped into the pulmonary artery through
the semilunar valve (pulmonary valve). The pulmonary artery is the only artery
which carries de-oxygenated blood.
the body superior and inferior vena cava, empty their content into the right
atrium. The blood passes through the right atrioventricular valve into the
right ventricule and from there it is pumped into the pulmonary artery through
the semilunar valve (pulmonary valve). The pulmonary artery is the only artery
which carries de-oxygenated blood.
After leaving the heart,
the pulmonary artery divides into 2-left and right pulmonary artery which
carries venous de-oxygenated blood to the lung, where exchange of gases takes
place, carbon dioxide (CO2) is given out and oxygen (O2)
is absorbed. Two pulmonary vein from each lung carries the oxygenated blood
back to the left atrium, blood then passes from here through the left
atrioventricular valve into the left ventricle and from it, blood is pumped
into the aorta through the left semi lunar (aortic valve) to the general
circulation or tissue where oxygen is used up.
the pulmonary artery divides into 2-left and right pulmonary artery which
carries venous de-oxygenated blood to the lung, where exchange of gases takes
place, carbon dioxide (CO2) is given out and oxygen (O2)
is absorbed. Two pulmonary vein from each lung carries the oxygenated blood
back to the left atrium, blood then passes from here through the left
atrioventricular valve into the left ventricle and from it, blood is pumped
into the aorta through the left semi lunar (aortic valve) to the general
circulation or tissue where oxygen is used up.
Pulmonary Circulation
This consist of the
circulation of blood from the right ventricle to the lungs and back to the left
atrium. In the lungs (CO2) is extracted and O2 is
absorbed. The pulmonary artery carry de-oxygenated blood from the right
ventricle of the heart passes upwards and divided into left and right pulmonary
arteries at the level of the 5th thoracic vertebrates. The left
pulmonary artery passes to the root of the right lungs and then divides into
two (2) branches one passing into each lobe. The right pulmonary artery passes
through the root of the right lungs and also divides into two larger branches
carrying blood to the middle and lower lobe while smaller branches carry blood
into the upper lobe. In the lungs these arteries divides and sub-divided into
smaller arteries-arterioles-capillaries so that exchange of gases take place
between capillary blood and air in the alveolar of the lungs, the capillary
containing the oxygenated blood to the left atrium of the heart
circulation of blood from the right ventricle to the lungs and back to the left
atrium. In the lungs (CO2) is extracted and O2 is
absorbed. The pulmonary artery carry de-oxygenated blood from the right
ventricle of the heart passes upwards and divided into left and right pulmonary
arteries at the level of the 5th thoracic vertebrates. The left
pulmonary artery passes to the root of the right lungs and then divides into
two (2) branches one passing into each lobe. The right pulmonary artery passes
through the root of the right lungs and also divides into two larger branches
carrying blood to the middle and lower lobe while smaller branches carry blood
into the upper lobe. In the lungs these arteries divides and sub-divided into
smaller arteries-arterioles-capillaries so that exchange of gases take place
between capillary blood and air in the alveolar of the lungs, the capillary
containing the oxygenated blood to the left atrium of the heart
Cardiac Cycle
Cardiac cycle is a cyclic activity of the heart that
is initiated by the stimulation of the conducting system which is increase or
reduced by the autonomic nervous system. It is made up of three phases;
is initiated by the stimulation of the conducting system which is increase or
reduced by the autonomic nervous system. It is made up of three phases;
1. Atrial Systole
2. Ventricular Systole
3. Complete diastole or the
rest phase
rest phase
Atrial systole: This is the contraction of
the atrial muscle in responses to the stimulation from both conducting and
autonomic nervous system. When blood flows into the right atrium through the
svc the specialized neuromuscular cell (S A node) are stimulated to initiate
impulses around the wall of the right Atrium. These impulses are spread evenly
around the atrial myocardium. This result to contraction of both atrial. The
peak of the contraction is called Systole. This last for about 0.1 seconds. At
the peak of contraction, there is increase in pressure within the atrial
chambers and atrioventricular valve are forced to open and blood flows into the
ventricle
the atrial muscle in responses to the stimulation from both conducting and
autonomic nervous system. When blood flows into the right atrium through the
svc the specialized neuromuscular cell (S A node) are stimulated to initiate
impulses around the wall of the right Atrium. These impulses are spread evenly
around the atrial myocardium. This result to contraction of both atrial. The
peak of the contraction is called Systole. This last for about 0.1 seconds. At
the peak of contraction, there is increase in pressure within the atrial
chambers and atrioventricular valve are forced to open and blood flows into the
ventricle
Ventricular Systole: Impulses are received by
the A.V node located within the boundary of the A.V myocardium at the mid
point. The impulses are passed on through the A.V bundle and spread out through
the ventricular myocardium by the purkinje fibres. At the peak of the
contraction (ventricular Systole) blood is forced into the pulmonary artery and
the aorta from the Right and Left Ventricules respectively. This last for about
0.35 sec. And at the end of the ventricular systole, there is a state of
complete rest of contraction known as complete Diastole which last for about
0.4 sec. The total of all the three phases make up the cardiac cycle or the
heartbeat.
the A.V node located within the boundary of the A.V myocardium at the mid
point. The impulses are passed on through the A.V bundle and spread out through
the ventricular myocardium by the purkinje fibres. At the peak of the
contraction (ventricular Systole) blood is forced into the pulmonary artery and
the aorta from the Right and Left Ventricules respectively. This last for about
0.35 sec. And at the end of the ventricular systole, there is a state of
complete rest of contraction known as complete Diastole which last for about
0.4 sec. The total of all the three phases make up the cardiac cycle or the
heartbeat.
Heart Sound
The closure of the
atrioventricular valves is associated with a sound that can be heard by placing
one’s ear to the chest or more conventionally by using a stethoscope. This is
termed 1st heart sound, with the stethoscope it is like the word Lup spoken very softly. This sound
marks the onset of ventricular systole. The closure of the semi lunar valves
causes the 2nd heart sound. Which is like the word Dup spoken softly this marks the end to
ventricular systole and start of the ventricular diastole. Since the interval
between the closure of the atrioventricular valves (1st heart sound)
and the closure of semi lunar valves (2nd heart sound) is shorter
than the interval between the closure of the semi lunar valves and the next
closure of the atrioventricular valves, the beating of the heart has a
characteristic rhythm Lub-Dub-pause-lub-dub-pause.
atrioventricular valves is associated with a sound that can be heard by placing
one’s ear to the chest or more conventionally by using a stethoscope. This is
termed 1st heart sound, with the stethoscope it is like the word Lup spoken very softly. This sound
marks the onset of ventricular systole. The closure of the semi lunar valves
causes the 2nd heart sound. Which is like the word Dup spoken softly this marks the end to
ventricular systole and start of the ventricular diastole. Since the interval
between the closure of the atrioventricular valves (1st heart sound)
and the closure of semi lunar valves (2nd heart sound) is shorter
than the interval between the closure of the semi lunar valves and the next
closure of the atrioventricular valves, the beating of the heart has a
characteristic rhythm Lub-Dub-pause-lub-dub-pause.
The heart sounds enable
events in the cardiac cycle to be timed. Any event which occurs in the internal
between the first and second heart sounds is occurring in systole while any
event occurring between the second heart sound and the next first sound is
occurring is diastole
events in the cardiac cycle to be timed. Any event which occurs in the internal
between the first and second heart sounds is occurring in systole while any
event occurring between the second heart sound and the next first sound is
occurring is diastole
Heart Murmurs
The flow of blood through
the heart is normally silent, but should a valve fail to open completely, it
will act as a partial obstruction. The blood will speed up and reach a high
velocity as it passes through the narrow opening. This will lead to turbulence
and to sounds and vibration in the chest.
the heart is normally silent, but should a valve fail to open completely, it
will act as a partial obstruction. The blood will speed up and reach a high
velocity as it passes through the narrow opening. This will lead to turbulence
and to sounds and vibration in the chest.
Cardiac Output
It represents the amount of
blood that is ejected from the heart in each minute through the aorta. It is
equal to the stroke volume multiplied by the heart rate. i.e (Co = Sv x HR)
blood that is ejected from the heart in each minute through the aorta. It is
equal to the stroke volume multiplied by the heart rate. i.e (Co = Sv x HR)
Stroke Volume
The amount of blood
expelled by each ventricular contraction is called the stroke volume. To large
extent, it is determined or depends on the venous return. It is about 70ml at
rest. This can be increase during exercise and is referred to as Cardiac Reserve. Stroke volume also
depends on ventricular-end-diastolic volume
(VEDV). Sometimes called pre-LOAD
which depends on venous return from the (SVC
and IVC).
expelled by each ventricular contraction is called the stroke volume. To large
extent, it is determined or depends on the venous return. It is about 70ml at
rest. This can be increase during exercise and is referred to as Cardiac Reserve. Stroke volume also
depends on ventricular-end-diastolic volume
(VEDV). Sometimes called pre-LOAD
which depends on venous return from the (SVC
and IVC).
Increased (VEDV) ventricular-end-diastolic volume
leads to stronger myocardiac contraction. There are definite limit of increment
of stroke volume. If not properly checked it may lead to heart failure. During
diastole, filling of the ventricle normally increase the volume of each
ventricle to about 110 to 120ml. This volume empty during systole, the volume
decrease to about 70ml which is stroke volume output. The remaining 40-50ml is
known as End-Systolic-Volume.
leads to stronger myocardiac contraction. There are definite limit of increment
of stroke volume. If not properly checked it may lead to heart failure. During
diastole, filling of the ventricle normally increase the volume of each
ventricle to about 110 to 120ml. This volume empty during systole, the volume
decrease to about 70ml which is stroke volume output. The remaining 40-50ml is
known as End-Systolic-Volume.
Venous Return
This is the major determinant of cardiac output. This
is the blood that returned back to the heart after circulation, through the SVC
in each minute into the right Atrium. The force of contraction of the (LV) left
ventricule is not sufficient to run the blood back to the heart. It needs other
factors to push the blood back through the right Atrium to right ventricule.
is the blood that returned back to the heart after circulation, through the SVC
in each minute into the right Atrium. The force of contraction of the (LV) left
ventricule is not sufficient to run the blood back to the heart. It needs other
factors to push the blood back through the right Atrium to right ventricule.
1. Position: Gravity plays a
good role in the veinous return, when standing or sitting. It also offer less
resistance when in lying position
good role in the veinous return, when standing or sitting. It also offer less
resistance when in lying position
2. Muscle Contraction: In the
extremities, (upper and lower limbs) the valves prevent the back flow of the
blood. The contraction of muscle also help in the pulling of blood back to the
hearty in the lower extremity the skeletal muscle cramp
extremities, (upper and lower limbs) the valves prevent the back flow of the
blood. The contraction of muscle also help in the pulling of blood back to the
hearty in the lower extremity the skeletal muscle cramp
3. Respiration Pump: This help
in the expansion of the chest cavity and creating negative pressure within the
thorax, helping the fast flow of blood back to the heart. Also during
inspiration, when the diaphragm descends, it creates pressure in the
intra-abdominal wall helping to push blood back to the heart
in the expansion of the chest cavity and creating negative pressure within the
thorax, helping the fast flow of blood back to the heart. Also during
inspiration, when the diaphragm descends, it creates pressure in the
intra-abdominal wall helping to push blood back to the heart
