HEART SOUNDS
During each
cardiac cycle, four sounds are produced,of which the first and second heart
sounds can be normally head using a stethoscope.
FIRST HEART SOUND:
It is soft ,low pitched and prolonged.it is
expressed as “lubb” and lasts for 0.15 sec.
Although
the first heart sound is heard all over the precordium, it is best head in the
mitral and tricuspid areas.
SECOND HEART SOUND:
It is
sharp,loud,high pitched and lasts for 0.12 sec.
It is
expressed as “dub” and is due to the closure of the semilunar valves (aortic
and pulmonary valves) at the end of protodiastole.
This sounds is best heard in the aortic and
pulmonary areas. During deep inspiration ,
there is increased negative intrathoracic
pressure ,which increases the venous return to the heart.
As a result , there is a delay the closure of
pulmonary valve than the aortic valve. This is called physiological splitting of
the second heart sound.
THIRD HEART SOUND:
It is a
soft,low pitched sound heard at the end of first 1/3 rd of diastole and is due
to the rapid filling of ventricles : it can be sometimes normally heard in
young individuals.
FOURTH HEART SOUND:
This sound
is never heard in normal persons, using a stethoscope.it occurs just before the
first heart sound . this is due to rapid filling of ventricular hypertrophy,
the fourth heart sound is heard using a stethoscope.
APEX BEAT OR
CARDIAC IMPULSE :
Apex beat
is defined as the outermost and lowermost point on the precordium, where a
definite cardiac pulsation can be seen or felt.
Normally,apex beat lies in the 5th
left intercostal space, 1 cm medial to the midclavicular line .
The position of the apex beat is shifted in
fibrosis,pneumothorax,pleural effusion or collapse of lungs.
The object
but you will not be able to to identify it.
By moving
the object to your fingertips where meissner’s corpuscles are abuntant, you
gather information about its shape, texture , and density, information your
brain uses to identify the object.
In the
palm of your hand,you possess fewer fine-touch receptors. It’s the pacinian
corpuscles or pressure receptors located deeper in the skin that enable you to
detect the object due to its weight. These are less abundant and without
sufficient receptor density,you cannot gather more specific information about
the object.
Meissner’s
and pacinian corpuscles are both encapsulated receptor types, surrounded by concentric
layers of a specialized connective tissue. Loking like a minute onion cut in
half, the concentric layers help in the identification of the pacinian
corpuscle.
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