1. heart

2. The mediastinum extends:
The mediastinum is a broad central partition that separates the two laterally placed pleural cavities .
The mediastinum extends:
from the sternum to the bodies of the vertebrae; and
from the superior thoracic aperture to the diaphragm

3. The mediastinum is subdivided into several smaller regions BY A transverse plane extending from the sternal angle to the intervertebral disc between vertebrae T 4 and T 5 separates the mediastinum into:
1-SUPERIOR MEDIASTINUM
2-INFERIOR MEDIASTINUM, which is further divided by the pericardial sac into:
1-THE ANTERIOR
The area anterior to the pericardial sac and posterior to the body of the sternum .
2-MIDDLE
The area in the middle, which includes the pericardial sac and its contents, is the middle mediastinum
3-POSTERIOR MEDIASTINUM
The region posterior to the pericardial sac and the diaphragm and anterior to the bodies of the vertebrae is the posterior mediastinum.

4. 1-THE FIBROUS PERICARDIUM : 2- THE SEROUS PERICARDIUM:
The Pericardium
The pericardium is a fibroserous sac surrounding the heart and the roots of the great vessels
It consists of two components,
1-THE FIBROUS PERICARDIUM :
is a tough connective tissue outer layer
2- THE SEROUS PERICARDIUM:
is thin layer and consists of two parts:
A-The parietal layer lines the inner surface of the fibrous;
B- The visceral layer (epicardium) of serous pericardium adheres to the heart and forms its outer covering
The narrow space created between the two layers of serous pericardium, containing a small amount of fluid, is the pericardial cavity
Pericarditis
Pericarditis is an inflammatory condition of the pericardium

5. The walls of the heart are composed of :
The heart is a hollow muscular organ that is somewhat pyramid shaped
lies within the pericardium in the middlle mediastinum.
MYOCARDIUM
The walls of the heart are composed of :
1-EPICARDIUM : visceral serous pericardium
2-MYOCARDIUM: cardiac muscle.
3-ENDOCARDIUM: layer of endothelium.
ENDOCARDIUM
EPICARDIUM

6. 1- Sternocostal (anterior) 2-Diaphragmatic (inferior)
Surfaces of the Heart
The heart has three surfaces:
1- Sternocostal (anterior)
2-Diaphragmatic (inferior)
3- A base (posterior)
The base of the heart, or the posterior surface, is formed mainly by the left atrium,
The apex of the heart, formed by the left ventricle, is directed downward, forward, and to the left
It lies at the level of the fifth left intercostal space, 3.5 in. (9 cm) from the midline.

7. The right border is formed by the right atrium;
Borders of the Heart
These borders are important to recognize when examining a radiograph of the heart.
The right border is formed by the right atrium;
The left border, by the left auricle; and below, by the left ventricle
the apex is formed by the left ventricle.
The lower border is formed mainly by the right ventricle but also by the right atrium;

8. Grooves on its (heart) external surfaces
Anterior view
The anterior interventricular sulcus is on the anterior surface of the heart and
The coronary sulcus circles the heart, separating the atria from the ventricles
Posterior view
The posterior interventricular sulcus is on the diaphragmatic surface of the heart

9. 1-the right and left atria 2- the right and left ventricles.
Chambers of the Heart
The heart is divided by vertical septa into four chambers:
1-the right and left atria
2- the right and left ventricles.

10. 2-The inferior vena cava
A-Right Atrium
The right atrium consists of a main cavity and a small outpouching, the auricle
Openings into the Right Atrium
1-The superior vena cava :
It returns the blood to the heart from the upper half of the body.
2-The inferior vena cava
It returns the blood to the heart from the lower half of the body.
3-The coronary sinus
which drains most of the blood from the
heart.
4- The right atrioventricular orifice is guarded by the tricuspid valve
Fetal Remnants
FOSSA OVALIS
Located on the atrial septum, which separates the right atrium from the left atrium ;
which was the site of the foramen ovale in the fetus

11. through the atrioventricular orifice
B-Right Ventricle
The right ventricle communicates with
1- The right atrium
through the atrioventricular orifice
2-The pulmonary trunk
through the pulmonary orifice
As the cavity approaches the pulmonary orifice it becomes funnel shaped, at which point it is referred to as
the infundibulum.
Its internal structure shows several internal projecting ridges formed of muscle bundles known as trabeculae carneae.
An example of trabeculae carneae is the papillary muscles,
It is attached by their bases to the ventricular wall while their apices are connected by fibrous chords (the chordae tendineae) to the cusps of the tricuspid valve

12. bicuspied valve or MITRAL VALVE
C-Left Atrium
consists of a main cavity and a left auricle.
the fibrous pericardium separates it from the esophagus
Openings into the Left Atrium
1-The four pulmonary veins
(two from each lung,
2-The left atrioventricular orifice is guarded by
bicuspied valve or MITRAL VALVE

13. The left ventricle communicates with
1- The left atrium
through the atrioventricular orifice
2- The aorta through the aortic orifice
The walls of the left ventricle are three times thicker than those of the right ventricle.
There are well-developed trabeculae carneae
The part of the ventricle below the aortic orifice is called
The aortic vestibule

14. No chordae or papillary muscles are associated with these valves
Semilunar valves
The aortic valve guards the aortic orifice
The pulmonary valve guards the pulmonary orifice and consists of three semilunar cusps.
No chordae or papillary muscles are associated with these valves

15. The mitral valve The tricuspid valve
guards the left atrioventricular orifice
It consists of two cusps.
The tricuspid valve
guards the right atrioventricular orifice
consists of three cusps formed
The bases of the cusps are attached to the fibrous ring of the skeleton of the heart, whereas their free edges and ventricular surfaces are attached to the chordae tendineae.
The chordae tendineae connect the cusps to the papillary muscles.
When the ventricle contracts, the papillary muscles contract and prevent the cusps from being forced into the atrium.
Valves are opened and closed by the difference in blood pressure

16. THE POSTERIOR INTERVENTRICULAR (DESCENDING) ARTERY
Arterial Supply of the Heart
The arterial supply of the heart is provided by :
1-THE RIGHT CORONARY ARTERY
2-LEFT CORONARY ARTERIY
which arise from the ascending aorta
The right coronary artery:
One of its branches (commonly) is
THE POSTERIOR INTERVENTRICULAR (DESCENDING) ARTERY

17. The left coronary artery
is usually larger than the right coronary artery
supplies the major part of the heart
divides into
1- ANTERIOR INTERVENTRICULAR BRANCH
AND
2-A CIRCUMFLEX BRANCH.

18. Venous Drainage of the Heart
Most !blood from the heart wall drains into the right atrium through THE CORONARY SINUS which lies in the posterior part of the atrioventricular groove
tributaries of the coronary sinus.
GREAT CARDIAC VEIN
SMALL CARDIAC VEINS
MIDDLE CARDIAC VEINS

19. THE CONDUCTING SYSTEM OF THE HEART
consists of specialized cardiac muscle present in
THE SINUATRIAL NODE
THE ATRIOVENTRICULAR NODE
THE ATRIOVENTRICULAR BUNDLE
RIGHT AND LEFT TERMINAL BRANCHES
THE SUBENDOCARDIAL PLEXUS OF PURKINJE FIBERS

20. Conducting System of the Heart
The normal heart contracts rhythmically at about 70 to 90 beats per minute in the resting adult.
The rhythmic contractile process originates spontaneously in the conducting system and the impulse travels to different regions of the heart, so the atria contract first and together, to be followed later by the contractions of both ventricles together
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The slight delay in the passage of the impulse from the atria to the ventricles allows time for the atria to empty their blood into the ventricles before the ventricles contract.
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21. Nerve Supply of the Heart
The heart is innervated by
sympathetic and parasympathetic fibers of
the autonomic nervous system
via
the cardiac plexuses
The sympathetic supply arises from the cervical and upper thoracic portions of the sympathetic trunks
The parasympathetic supply comes from the vagus nerves
Activation of sympathetic nerves results in cardiac acceleration, increased force of contraction of the cardiac muscle, and dilatation of the coronary arteries.
Activation of the parasympathetic nerves results in a reduction in the rate and force of contraction of the heart and a constriction of the coronary