The document provides an overview of the anatomy of the heart. It describes the heart as a hollow muscular organ divided into four chambers - the right and left atria and ventricles. Each chamber is then described in detail, including its size, location within the heart, internal structures like valves and openings, and relations to other cardiovascular structures. Key components summarized include the four chambers, their internal structures like valves and openings, and basic relations to surrounding areas in the thoracic cavity.

1. ANATOMY OF HEART
Prepared by: Sharmin Susiwala

2. Front view of heart and lungs.

7. The Heart
(Cor)
• The heart is a hollow muscular organ of a somewhat conical
form; it lies between the lungs in the middle mediastinum
and is enclosed in the pericardium.
• It is placed obliquely in the chest behind the body of the
sternum and adjoining parts of the rib cartilages, and projects
farther into the left than into the right half of the thoracic
cavity, so that about one-third of it is situated on the right and
two-thirds on the left of the median plane.
Size.—
o The heart, in the adult, measures about
- 12 cm. in length,
- 8 to 9 cm. in breadth at the broadest part,
- 6 cm. in thickness.
o Its weight, in the male, varies from 280 to 340 grams; in the
female, from 230 to 280 grams.

8. Component Parts.— “gross anatomy of the heart”
• The heart is subdivided by septa into right and left halves, and a
constriction subdivides each half of the organ into two cavities,
- the upper cavity being called the atrium,
- the lower the ventricle.
• The heart therefore consists of four chambers, viz., right and left
atria, and right and left ventricles.
• The division of the heart into four cavities is indicated on its surface
by grooves.
• The atria are separated from the ventricles by the coronary
sulcus (auriculoventricular groove)
• The interatrial groove, separating the two atria
• The ventricles are separated by two grooves, one of which is,
the anterior longitudinal sulcus, the other posterior longitudinal
sulcus.

9. Base (basis cordis):
- Directed upward, backward, and to the right, is separated from the fifth, sixth,
seventh, and eighth thoracic vertebrae by the esophagus, aorta, and thoracic duct.
- It is formed mainly by the left atrium, and, to a small extent, by the back part of the
right atrium.
Apex (apex cordis):
- The apex is directed downward, forward, and to the left, and is overlapped by the
left lung and pleura
- It lies behind the fifth left intercostal space, 8 to 9 cm. from the mid-sternal line, or
about 4 cm. below and 2 mm. to the medisial side of the left mammary papilla.
Sternocostal surface:
- Directed forward, upward, and to the left.
- Its lower part is convex, formed chiefly by the right ventricle, and traversed near its
left margin by the anterior longitudinal sulcus.
- Its upper part is separated from the lower by the coronary sulcus, and is formed by
the atria; it presents a deep concavity, occupied by the ascending aorta and the
pulmonary artery.

10. Diaphragmatic surface:
- Directed downward and slightly backward
- Is formed by the ventricles, and rests upon the central tendon and a
small part of the left muscular portion of the diaphragm.
Right margin of the heart:
- Is long
- Is formed by the right atrium above and the right ventricle below.
Left or obtuse margin of the heart:
- Is shorter, full, and rounded
- It is formed mainly by the left ventricle, but to a slight extent,
above, by the left atrium.

11. • Structure.—
 The heart consists of muscular fibers, and of fibrous rings
which serve for their attachment.
 It is covered by the visceral layer of the serous pericardium
(epicardium), and lined by the endocardium.
 Between these two membranes is the muscular wall
or myocardium.
Cardiac Muscular Tissue

12. CHAMBERS OF THE HEART
Right Atrium (atrium dextrum; right auricle).—

14.  The right atrium is larger than the left, but its walls are somewhat thinner, measuring about
2 mm.
 It consists of two parts: a principal cavity, or sinus venarum, situated posteriorly, and an
anterior, smaller portion, the auricula.
Sinus Venarum (sinus venosus).—
- The sinus venarum is the large quadrangular cavity placed between the two venæ cavæ.
- Its walls, which are extremely thin, are connected below with the right ventricle, and medially with the
left atrium, but are free in the rest of their extent.
Auricula (auricula dextra; right auricular appendix).—
- The auricula is a small conical muscular pouch, the margins of which present a dentated edge.
- It projects from the upper and front part of the sinus forward and toward the left side, overlapping the
root of the aorta.
• The separation of the auricula from the sinus venarum is indicated externally by a
groove, the terminal sulcus, which extends from the front of the superior vena
cava to the front of the inferior vena cava.
• On the inner wall of the atrium the separation is marked by a vertical, smooth,
muscular ridge, the terminal crest. (crista terminalis)
• Behind the crest the internal surface of the atrium is smooth, while in front of it the
muscular fibers of the wall are raised into parallel ridges resembling the teeth of a
comb, and hence named the musculi pectinati.

15. • Its interior presents the following parts:
1. Openings »
 Superior vena cava.
 Inferior vena cava.
 Coronary sinus.
 Foramina venarum minimarum.
 Atrioventricular.
2. Valves »
• Valve of the inferior vena cava.
• Valve of the coronary sinus.
3. Others »
 Fossa ovalis.
 Limbus fossæ ovalis.
 Intervenous tubercle.
 Musculi pectinati.
 Crista terminalis.

16. 1. Openings:
• Superior Vena cava- The superior vena cava returns the blood from the upper
half of the body, and opens into the upper and back part of the atrium, the
direction of its orifice being downward and forward. Its opening has no valve.
• Inferior Vena cava- The inferior vena cava, larger than the superior, returns the
blood from the lower half of the body, and opens into the lowest part of the
atrium, near the atrial septum, its orifice being directed upward and backward,
and guarded by a rudimentary valve, the valve of the inferior vena
cava (Eustachian valve).
• Coronary sinus- The coronary sinus opens into the atrium, between the orifice of
the inferior vena cava and the atrioventricular opening. It returns blood from the
substance of the heart and is protected by a semicircular valve, the valve of the
coronary sinus (valve of Thebesius).
• Foramina Venerum minimum- The foramina venarum minimarum (foramina
Thebesii) are the orifices of minute veins (venoe cordis minimoe), which return
blood directly from the muscular substance of the heart.
• Atrioventricular Opening- The atrioventricular opening (tricuspid orifice) is the
large oval aperture of communication between the atrium and the ventricle; it
will be described with the right ventricle.

17. 2. Valves:
• Valve of inferior Venacava- The valve of the inferior vena cava (valvula venoe cavoe
inferioris [Eustachii]; Eustachian valve) is situated in front of the orifice of the
inferior vena cava. It is semilunar in form.
 In the fetus this valve is of large size, and serves to direct the blood from the
inferior vena cava, through the foramen ovale, into the left atrium.
 In the adult it occasionally persists, and may assist in preventing the reflux of
blood into the inferior vena cava; more commonly it is small, and may present a
cribriform or filamentous appearance; sometimes it is altogether wanting.
• Valve of coronary sinus- The valve of the coronary sinus (valvula sinus
coronarii [Thebesii]; Thebesian valve) is a semicircular fold of the lining membrane
of the atrium, at the orifice of the coronary sinus. It prevents the regurgitation of
blood into the sinus during the contraction of the atrium. This valve may be double
or it may be cribriform.
3. Fossa Ovalis:
• The fossa ovalis is an oval depression on the septal wall of the atrium, and
corresponds to the situation of the foramen ovale in the fetus.
• It is situated at the lower part of the septum, above and to the left of the orifice
of the inferior vena cava.

18. 4. Limbus Fossa Ovalis:
• The limbus fossæ ovalis (annulus ovalis) is the prominent oval margin of the fossa
ovalis.
5. Intervenous Tubercle:
• The intervenous tubercle (tuberculum intervenosum; tubercle of Lower) is a
small projection on the posterior wall of the atrium, above the fossa ovalis.

19. Right Ventricle (ventriculus dexter).—

20. • The right ventricle is triangular in form, and extends from the right atrium to near the apex
of the heart.
• Its anterosuperior surface is rounded and convex, and forms the larger part of the
sternocostal surface of the heart.
• Its under surface is flattened, rests upon the diaphragm, and forms a small part of the
diaphragmatic surface of the heart.
• Its posterior wall is formed by the ventricular septum, which bulges into the right ventricle,
so that a transverse section of the cavity presents a semilunar outline.
• Its upper and left angle forms a conical pouch, the conus arteriosus, from which the
pulmonary artery arises.
• A tendinous band, which may be named the tendon of the conus arteriosus, extends
upward from the right atrioventricular fibrous ring and connects the posterior surface of the
conus arteriosus to the aorta.
• The wall of the right ventricle is thinner than that of the left, the proportion between them
being as 1 to 3; it is thickest at the base, and gradually becomes thinner toward the apex.

21. • Its interior presents the following parts:
1. Openings »
• Right atrioventricular.
• Pulmonary artery.
2. Valves »
• Tricuspid.
• Pulmonary.
3. Others »
• Trabeculae carnae.
• Chordae tendineae

22. 1. Openings:
• Right atrioventricular Orifice-
 The right atrioventricular orifice is the large oval aperture of communication
between the right atrium and ventricle.
 Situated at the base of the ventricle, it measures about 4 cm. in diameter and is
surrounded by a fibrous ring, covered by the lining membrane of the heart; it is
considerably larger than the corresponding aperture on the left side, being
sufficient to admit the ends of four fingers.
 It is guarded by the tricuspid valve.
• Opening of Pulmonary artery-
 The opening of the pulmonary artery is circular in form, and situated at the
summit of the conus arteriosus, close to the ventricular septum.
 It is placed above and to the left of the atrioventricular opening, and is guarded by
the pulmonary semilunar valves.
2. Valves:
• Tricuspid valve (valvula tricuspidalis)-
 consists of three somewhat triangular cusps or segments.

23.  The largest cusp is interposed between the atrioventricular orifice and the conus
arteriosus and is termed the anterior or infundibular cusp.
 A second, the posterior or marginal cusp, is in relation to the right margin of the
ventricle, and a third, the medial or septal cusp, to the ventricular septum.
 Their central parts are thick and strong, their marginal portions thin and translucent
 Their bases are attached to a fibrous ring surrounding the atrioventricular orifice and
are also joined to each other so as to form a continuous annular membrane, while
their apices project into the ventricular cavity.
 Their atrial surfaces, directed toward the blood current from the atrium, are smooth;
their ventricular surfaces, directed toward the wall of the ventricle, are rough and
irregular, and, together with the apices and margins of the cusps, give attachment to
a number of delicate tendinous cords, the chordae tendineae

24.  The trabeculae carneae (columnoe carneoe) are rounded or irregular muscular
columns which project from the whole of the inner surface of the ventricle, with
the exception of the conus arteriosus.
 They are of three kinds: some are attached along their entire length on one side
and merely form prominent ridges, others are fixed at their extremities but free in
the middle, while a third set (musculi papillares) are continuous by their bases with
the wall of the ventricle, while their apices give origin to the chordæ tendineæ
which pass to be attached to the segments of the tricuspid valve.
 There are two papillary muscles, anterior and posterior:
- of these, the anterior is the larger, and its chordæ tendineæ are connected with the
anterior and posterior cusps of the valve
- the posterior papillary muscle sometimes consists of two or three parts; its
chordæ tendineæ are connected with the posterior and medial cusps.
 A muscular band frequently extends from the base of the anterior papillary muscle
to the ventricular septum. From its attachments it may assist in preventing over
distension of the ventricle, and so has been named the moderator band.
• Pulmonary semilunar valves:
 Three in number, two in front and one behind.
 They are attached, by their convex margins, to the wall of the artery, at its junction
with the ventricle, their free borders being directed upward into the lumen of the
vessel.

25.  The free and attached margins of each are strengthened by tendinous fibers, and
the former presents, at its middle, a thickened nodule (corpus Arantii).
 From this nodule tendinous fibers radiate through the segment to its attached
margin, but are absent from two narrow crescentic portions, the lunulae, placed
one on either side of the nodule immediately adjoining the free margin.
 Between the semilunar valves and the wall of the pulmonary artery are
three pouches or sinuses (sinuses of Valsalva).

26. Left Atrium (atrium sinistum; left auricle).—

28. • The left atrium is rather smaller than the right, but its walls are thicker,
measuring about 3 mm.
• It consists, like the right, of two parts, a principal cavity and an auricula.
• The principal cavity: is cuboidal in form, and concealed, in front, by the
pulmonary artery and aorta; in front and to the right it is separated from
the right atrium by the atrial septum; opening into it on either side are the
two pulmonary veins.
• Auricula (auricula sinistra; left auricular appendix).—
- The auricula is somewhat constricted at its junction with the principal cavity
- It is longer, narrower, and more curved than that of the right side, and its
margins are more deeply indented.
- It is directed forward and toward the right and overlaps the root of the
pulmonary artery.
The interior of the left atrium presents the following parts:
1. Openings of the four pulmonary veins.
2. Left atrioventricular opening.
3. Musculi pectinati.

29. • Opening of pulmonary veins:
 four in number, open into the upper part of the posterior surface of the left
atrium—two on either side of its middle line: they are not provided with
valves.
• Left atrioventricular opening:
 is the aperture between the left atrium and ventricle, and is rather smaller
than the corresponding opening on the right side.
• Musculi pectinati:
 Fewer and smaller than in the right auricula, are confined to the inner
surface of the auricula.
• On the atrial septum may be seen a lunated impression, bounded below by
a crescentic ridge, the concavity of which is turned upward. The depression
is just above the fossa ovalis of the right atrium.

30. Left Ventricle (ventriculus sinister).—

31. • The left ventricle is longer and more conical in shape than the right, and on
transverse section its concavity presents an oval or nearly circular outline.
• It forms a small part of the sternocostal surface and a considerable part of
the diaphragmatic surface of the heart
• It also forms the apex of the heart.
• Its walls are about three times as thick as those of the right ventricle.
• Its interior presents the following parts:
1. Openings »
• Left atrioventricular.
• Aortic.
2. Valves »
• Bicuspid or Mitral.
• Aortic.
3. Others »
• Trabeculæ carneæ.
• Chordæ tendineæ

32. 1. Openings:
• Left atrioventricular opening (mitral orifice) :
 is placed below and to the left of the aortic orifice.
 It is a little smaller than the corresponding aperture of the opposite side, admitting
only two fingers.
 It is surrounded by a dense fibrous ring, covered by the lining membrane of the
heart, and is guarded by the bicuspid or mitral valve.
• Aortic opening:
 is a circular aperture, in front and to the right of the atrioventricular, from which it
is separated by the anterior cusp of the bicuspid valve.
 Its orifice is guarded by the aortic semilunar valves.
 The portion of the ventricle immediately below the aortic orifice is termed
the aortic vestibule, and possesses fibrous instead of muscular walls.
2. Valves:
• Bicuspid or mitral valve (valvula bicuspidalis [metralis]):
 is attached to the circumference of the left atrioventricular orifice in the same
way that the tricuspid valve is on the opposite side.

33.  It consists of two triangular cusps, formed by duplicatures of the lining membrane,
strengthened by fibrous tissue, and containing a few muscular fibers.
 The cusps are of unequal size, and are larger, thicker, and stronger than those of
the tricuspid valve.
 The larger cusp is placed in front and to the right between the atrioventricular and
aortic orifices, and is known as the anterior or aortic cusp
 The smaller or posterior cusp is placed behind and to the left of the opening.
 Two smaller cusps are usually found at the angles of junction of the larger.
 The cusps of the bicuspid valve are furnished with chordæ tendineæ, which are
attached in a manner similar to those on the right side; they are, however, thicker,
stronger, and less numerous.
• Aortic semilunar valves:
 three in number, and surround the orifice of the aorta
 Two are anterior (right and left) and one posterior.
 They are similar in structure, and in their mode of attachment, to the pulmonary
semilunar valves, but are larger, thicker, and stronger
 The lunulæ are more distinct, and the noduli or corpora Arantii thicker and more
prominent.
 Opposite the valves the aorta presents slight dilatations, the aortic sinuses (sinuses
of Valsalva), which are larger than those at the origin of the pulmonary artery.

34.  The trabeculæ carneæ are of three kinds, like those upon the right side, but they
are more numerous, and present a dense interlacement, especially at the apex,
and upon the posterior wall of the ventricle.
 The musculi papillares are two in number, one being connected to the anterior, the
other to the posterior wall; they are of large size, and end in rounded extremities
from which the chordæ tendineæ arise.
 The chordæ tendineæ from each papillary muscle are connected to both cusps of
the bicuspid valve.

35. • Vessels—The arteries supplying the heart are the right and left coronary from the
aorta; the veins end in the right atrium.
• The lymphatics end in the thoracic and right lymphatic ducts.
• The nerves are derived from the cardiac plexus, which are formed partly from the
vagi, and partly from the sympathetic trunks. They are freely distributed both on
the surface and in the substance of the heart, the separate nerve filaments being
furnished with small ganglia.