Lecture Notes
Heart II
-
University:
Kentucky State University -
Course:
BIO 301 | Human Anatomy Academic year:
2024
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Views:
276
Pages:
19
Author:
behend6abs
HEART II Structure of the
Heart
The walls of the heart are composed of:
• a thick layer of cardiac muscle, the myocardium
• covered externally by the epicardium
• and lined internally by the endocardium.
From google The interventricular or ventricular
septum
• septum (IVS) composed of :
MUSCULAR & MEMBRANOUS parts
•
is a strong, obliquely placed
partition between the right and left
ventricles forming part of the walls
of each.
• Because of the much higher blood
pressure in the left ventricle, the
muscular part of the IVS, which forms
the majority of the septum, has the
thickness of the remainder of the wall
of the left ventricle (two to three times
as thick as the wall of the right
ventricle)
•Thebulges
into
the cavity
theseptum
right is
smaller
upper
part ofofthe
thinventricle.
and membranous and attached to
the fibrous skeleton. Fibrous skeleton of the
heart
• is a collection of dense, fibrous
connective
tissue
• four rings with interconnecting areas in
a plane between the atria and the
ventricles.
• The four rings of the cardiac skeleton
surround the two atrioventricular
orifices, the aortic orifice and opening
of the pulmonary trunks.
• The interconnecting areas include:
I. the right fibrous trigone, which
is a thickened area of
connective tissue between the
aortic ring and right
atrioventricular ring.
II. the left fibrous trigone, which
is a thickened area of
4 Sheet Note1
Trigone: means an area where there is a connecting between different fibrous rings.
• Left Trigone ; aortic ring + left AV ring .
• Right Trigone ; aortic ring + Right AV ring. The fibrous skeleton of the
heart:
• Keeps the orifices of the AV and semilunar valves patent and prevents
them from being overly distended by an increased volume of blood
pumping through them.
•
Provides attachments for the leaflets and cusps of the valves.
•
Provides attachment for the myocardium
•
Forms an electrical “insulator,” by separating the myenterically
conducted impulses of the atria and ventricles so that they contract
independently
5 Conductive system of the
heart
• The system is formed of
specialised cardiac muscle
cells which are difficult to
distinguish from cardiac
muscle.
• It comprises the Sinu-atrial
(SA) node, the
Atrioventricular (AV) node,
the Atrioventricular bundle
(AV bundle, or bundle of
His), its right and left
branches and a terminal
subendocardial plexus
(Purkinje fibres).
• This system initiates the
complex cardiac muscle
contractions comprising the
cardiac cycle, and controls its
regularity.
#Read only NERVE SUPPLY OF THE
HEART Nerve Supply of the
Heart
The heart is innervated by sympathetic and parasympathetic fibers of the
autonomic nervous system via the cardiac plexuses situated below the arch of the
aorta.
• The sympathetic supply arises from the cervical and upper thoracic
portions of the sympathetic trunks
• The parasympathetic supply comes from the vagus nerves.
The postganglionic sympathetic fibers terminate on the sinuatrial and atrioventricular
nodes, on cardiac muscle fibers, and on the coronary arteries.
Activation of these nerves results in:
• Cardiac acceleration
• Increased force of contraction of the cardiac muscle
• Dilatation of the coronary arteries.
The postganglionic parasympathetic fibers terminate on the sinuatrial and
atrioventricular nodes and on the coronary arteries.
Activation
of theinparasympathetic
nerves
results in: of
• Reduction
the rate and force
of contraction
the heart
8 9 Surface anatomy of the
heart The lines cover the front, side, and back of the thorax
Midsternal line (anterior median line) & Lateralsternal borders : Runs down
the midline and lateral side of the sternum.
Parasternal line: midway between the lateral sternal border & midclavicular line.
Right and left midclavicular lines: Run parallel with the midsternal line,
passing through the midpoint of each clavicle Anterior axillary line: Runs along the
anterior axilliary fold, close to the front of
the thorax.
Posterior axillary line: Runs parallel with
the anterior axillary line along the posterior
axillary fold, close to the back.
Midaxillary line: Runs midway between
the anterior and posterior axillary lines,
starting at deepest part of the axilla. Midvertebral (posterior median) line:
Runs vertically down the midpoint of
the spine.
Right and left scapular lines: Run
parallel with the midvertebral line pass
through the inferior angles of scapulae the upper limit of the heart reaches as high as:
• The 3rd costal cartilage on the right side of the
sternum
• The 2nd intercostal space on the left side of the
sternum
•
(both 1.2cm from the sternal border).
#Extra to help u memorize
6
The right margin of the heart extends from:
• the right 3rd costal cartilage to near the right 6th costal
cartilage. The left margin of the heart descends laterally from:
•
the 2nd intercostal space to the apex located near the midclavicular line in
the 5th intercostal space.
6
The lower margin of the heart extends from:
• the sternal end of the right 6th costal cartilage to the apex in the 5th intercostal
space near the midclavicular line (or 9cm from the midline). Heart valves and where to listen for heart
sounds
The tricuspid valve is:
Almost vertical and centred at the 4th intercostal space just to the right of the
midline.
It can be heard just to the left of the lower part of the sternum near the 5th
intercostal space
6
صورة اوضح The mitral
valve:
is oblique, running down and left, starting opposite the 4th costal cartilages and lying
beneath the left side of the sternum.
It can be heard over the apex of the heart in the left 5th intercostal space at the
midclavicular
line.
6 The pulmonary
valve:
is horizontal and centered at the 3rd left chondro-sternal
joint. It is heard over the medial end of the left 2nd
intercostal space.
6
The aortic valve:
is oblique, running down and right, starting from the medial end of the 3rd left intercostal
space.
It can be heard over the medial end of the right 2nd intercostal space
Heart II
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