Chambers of heart

Chambers of heart


CHAMBERS OF HEART    
  • The human heart has four chambers: two upper chambers (the atria) and two lower ones (the ventricles)

RIGHT ATRIUM:

  • Has thinnest walls of the four chambers.
  • Forms rt. border of heart.
  • It is divided by (crista terminalis) into two parts:-

1. Rough anterior part or atrium proper (pectinate part), including auricle

  • It is derived from right half of primitive atrial chamber.
  • There is a series of transverse muscular ridges calles musculi pectinate which are attached to crista terminalis & gives appearance like“teeth of a comb”.
  • SA node is situated in the upper part of crista terminalis.
  • Auricle lies in the superomedial portion.

2. Posterior smooth part or sinus venorum

  • It is derived from absorption of right horn of sinus venosus.
  • It has openings of:

    i. Superior vena cava- Has no valve.

    ii. Inferior vena cava- 

  • Orifice is guarded by a rudimentary valve of IVC (Eustachian valve) derived from embryonic right venous valve, which directs the blood fromIVC (Eustachian valve) derived from embryonic right venous valve, which directs the blood from IVC towards foramen ovalve in fetal live.
  • This valve is nonfunctional in adults.

    iii. Coronary sinus-

  • Orifice lies b/w tricuspid orifice & IVC orifice .
  • It is guarded by a functional semilunar valve (thebesian valve)

    iv. Venae cardis minimae (thebesian veins)- Open through foramina venorum minimarum

    v. Anterior cardiac vein

    vi. Right marginal vein- open into coronary sinus (not in right atrium)

→ Crista terminalis (divides the right atrium into anterior & posterior part) is a ridge of smooth muscle fibers extending from the SVC to valve of IVC.

→ It is developed from developed from embryonic right venous valve & is represented on the surface by sulcus terminalis.

INTERATRIAL SEPTAL REGION

  • Interatrial septum develops from approximation of embryonic  septum primum & septum secundum.
  • Features on right atrial side are:
  1.Fossa ovalis
  • Oval shaped depression lying above the level of IVC opening in the interatrial septum.
  • It is the embryological remnant of foramen ovale, which connects right atrium to left atrium in embryonic life.
  • Floor of the fossa ovalis is formed by septum primum.
  2. Limbus fossa ovalis (Annulus ovalis):
  • It is thickened rim present above the fossa ovalis.
  • It presents the lower free margin of septum secundum.
  3. Triangle of Koch
  • It is a triangular region in the lower part of interatrial septum which contains AV node.
  • It is bounded above by tendon of Todaro below by base of septal leaflet of tricuspid valve & anteriorly (base) by orifices of coronary sinus.
  • Immediately above the membranous septum, the septal region shows a slight bulge known as Torus aorticus.
  • Torus aorticus is an impression in the cavity of Right atrium.  
LEFT ATRIUM:
  • Has slightly thicker walls than right atrium.
  • Left atrium forms the base of the heart.
  • Left atrium forms the anterior wall of oblique sinus of pericardium. It lies in front of esophagus.
  • Divided into:
  1.  Posteriorly smooth walled part–  receiving 4 pulmonary veins which develops from absorption of embryonic pulmonary veins.
  2. Rough walled part (left auricle)- having network of musculi pectinati developing from left half of primitive atrium.
  • Left auricle projects anteriorly to overlap infundibulum of right ventricle.

RIGHT VENTRICLE:

  • It is anteroinferior chamber & projects ro the left of right atrium.
  • It is in contact with the sternum.
  • Anterior wall forms most of the sternocostal surface of the heart.
  • Divided into:

1. Rough inflowing part (ventricle proper)

  • It is developed from right half of primitive ventricle.
  • Its interior is rough due to the presence of muscular ridges known as trabeculae carnae, which are more prominent in apical region.
  • Trabeculae carneae are of 3 types:-

  i. Ridges- Linear elevations.

  • Supraventricular crest- a ridge present b/w the pulmonary & atrioventricular orifices, extends downwards in the posterior wall of infundibulum.

  ii. Bridges- Muscular elevations with fixed ends on ventricular walls, the center being free.

  • Septomarginal trabecula: It is specialised bridge which extends from the right ventricularsetum to the base of anterior paoillary muscle.

  iii. Papillary muscles- are conical projections of muscle fiber bundles.

  • There are three papillary muscles in the right & two in the left ventricle.
  • They regulate closure of atrioventricular valves.

2. Smooth outflowing part (infundibulum or conus arteriosus)

  • Develops from midportion of bulbus cordis.
  • Surrounds pulmonary valve Supraventricular crest (crista supraventricularis) or infundibuloventricular crest separates tricuspid (AV) orifice, i.e inlet & outlet parts.
  • Crista supraventricularis Separate Tricuspid valve & Pulmonary valve and Apex trabeculated both.

LEFT VENTRICLE:

  • It has three times thicker walls than right ventricle.
  • It is divided into two parts:

i. Rouh walled inflowing part (left ventricular proper) developing from left of primitive ventricle.

  • Trabeculae carnae (muscular bridges) are more prominent than that in right ventricle.

ii. Smooth walled outflowing part (aortic vestibule) developing from bulbus cordis.

  • Aortic vestibule leads to ascending aorta.
Interventricular septum
  • The membranous part of the interventricular septum is situated in between Left ventricle and right atrium.
  • Depolarisation of cardiac ventricular muscle starts from Left side of inter ventricular septum
Exam Question
 
  • SA node is situated in the upper part of crista terminalis.
  • Auricle lies in the superomedial portion.
  • Floor of the fossa ovalis is formed by septum primum..
  • Left atrium forms the base of the heart.
  • Left atrium forms the anterior wall of oblique sinus of pericardium. It lies in front of esophagus.
  • Left auricle projects anteriorly to overlap infundibulum of right ventricle.
  • The anterior surface, or sternocostal surface, is mostly made up of the right ventricle.
  • Torus aorticus is an impression in the cavity of Right atrium
  •  Superior vena cava- Has no valve.
Don’t Forget to Solve all the previous Year Question asked on Chambers of heart

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