Welcome to your 7th Anatomy part in the Final!
In this part, we will continue talking about the Heart.
HEART
The emotion that breaks your heart is sometimes the very one
that heals it!
WHAT ARE THE CHAMBERS Heart consists of 2 Atria (Upper) and 2 Ventricles (Lower):
OF THE HEART?
Right Atrium
Cavity of right atrium is divided by Crista terminalis into:
1. Anterior (Rough), which contains Pectinate muscles.
2. Posterior (Smooth), which contains Fossa ovalis (Remnant of
Foramen ovale in fetus).
- It receives blood from 3 sources: Superior vena cava, Inferior
vena cava, and Coronary sinus.
- It is separated from Left atrium by Interatrial septum.
- It is separated from Right ventricle by Tricuspid valve, which
has 3 cusps (parts) of dense C.T covered by Endocardium.
Right Ventricle
Right ventricle forms most of Anterior surface of the heart.
• This chamber has multiple features:
1. Trabeculae carneae, which are muscles of the ventricle.
2. Papillary muscles, which are cone-shaped trabeculae carneae
(raised bundles of cardiac muscle).
3. Chordae tendinae, which are cords between papillary muscles
and valve cusps.
4. Interventricular Septum, which separates the two ventricles.
5. Pulmonary Semilunar Valve, through which blood flows from
Right ventricle to Pulmonary trunk.
Left Atrium
Left atrium forms most of the base of the heart.
-It receives blood from the lungs via 4 pulmonary veins (R and L).
LAMB - Bicuspid valve separates Left atrium from Left ventricle. It has 2
LA = Left Atrioventricular.
cusps (parts). Remember LAMB.
M = Mitral valve.
B = Bicuspid valve.
Left Ventricle
Left ventricle forms the base of the heart. It has Trabeculae
carneae and papillary muscles attached to cusps of Mitral valve
through Chordae tendinae.
-It pumps blood to the Aorta through the Aortic Seminlunar Valve.
Above this valve are the openings of coronary arteries.
- Wall of Left ventricle is 10X thicker than wall of right ventricle.
HOW DO VALVES OPEN AND
• Atrioventricular valves (Tricuspid and Mitral) open when the
CLOSE?
ventricular pressure is lower than atrial pressure.
- This happens when ventricles are relaxed → Chordae tendinae
are slack, and papillary muscles are relaxed.
• AV valves close to prevent back flow of blood into atria.
- This happens when ventricles contract → Chordae tendinae are
pulled taut because papillary muscles contract to pull them and
prevent the cusps from everting.
• Semilunar valves (Aortic and Pulmonary) open when the
ventricles contract to allow blood to exit from the ventricles.
• Semilunar valves close with ventricular relaxation to prevent
blood from returning to the ventricles. Back-flow of blood into the
valve helps in its closure.
WHAT IS LIGAMENTUM
During fetal life, there is a blood vessels between Pulmonary
ARTERIOSUM?
artery and Aorta called Ductus arteriosus. Normally, this duct
closes and changes into Ligamentum arteriosum.
- Sometimes, it remains opened after delivery, this is called Patent
Ductus Arteriosus.
WHAT ARE THE TYPES OF In human body, there are two types of circulations:
CIRCULATION? 1. Systemic Circulation: Left ventricle → Aorta → Branches to
organs → Arterioles → Capillaries (exchange) → Venules → Veins
→ Right atrium.
2. Pulmonary Circulation: Right ventricle → Pulmonary trunk →
Pulmonary arteries → Lung (gas exchange) → Pulmonary veins
→ Left atrium.
WHAT IS AUSCULTATION? Auscultation is hearing heart sound using a stethoscope. These
sounds are the turbulence of blood flow caused by valve closure.
• First sound (Lubb) is created by closure of AV valves.
• Second sound (Dubb) is created by closure of Semilunar valves.
Heart is supplied by Right and Left coronary arteries:
I. Right Coronary Artery arises from Ascending Aorta behind
Anterior aortic sinus. It runs in right Atrioventricular groove.
- Near the inferior border, it continuous posteriorly along the
Atrioventricular groove. Finally, anastomoses with Left coronary
artery in the Posterior inter-ventricular groove.
WHAT ARE THE BRANCHES OF 1. Right Conus Artery: supplies Infundibulum and Anterior wall
RIGHT CORONARY ARTERY? (Upper part) of Right ventricle.
2. Anterior Ventricular (2-3) branches: supply anterior surface of
right ventricle.
WHAT ELSE?
3. Right Marginal Artery (largest): runs to the apex of the heart.
4. Posterior Ventricular (2) branches: for diaphragmatic surface
of right ventricle.
5. Atrial Branches: supply anterior and lateral surfaces of right
atrium. One branch supplies posterior surface of both atria.
6. Branch to the Sinoatrial (SA) Node in 60% of population.
7. Posterior Interventricular (Descending) artery, which runs
toward the apex in Posterior Interventricular groove.
- It supplies Right and Left ventricles, including inferior walls.
- It supplies posterior part of Interventricular septum (w/o Apex).
- It gives a large septal branch that supplies AV node.
WHAT ABOUT LEFT
II. Left Coronary Artery is larger than right coronary artery. It
arises from Ascending Aorta behind Posterior aortic sinus.
CORONARY ARTERY?
- Then, it passes between pulmonary trunk and left auricle and
enters into the Atrioventricular groove.
- It divides into Anterior Interventricular and Circumflex brnchs.
- It supplies greater part of Left atrium and ventricle, and IV
septum.
WHAT ARE THE BRANCHES OF
1. Anterior interventricular (Descending) artery, which runs
LEFT CORONARY ARTERY?
toward the apex in Anterior interventricular groove.
- It passes around the apex to enter Posterior interventricular
groove and anastomose with terminal branches of RCA.
- It supplies the ventricles and anterior part of ventricle septum.
- It gives the Left diagonal and Left conus branches.
2. Circumflex artery, which winds around the left margin of heart
in the Atrioventricular groove. It gives multiple branches:
a. Left Marginal branch: supply left ventricular margin to Apex.
b. Anterior and Posterior ventricular branches: for left ventricle.
c. Atrial branches: to supply the left atrium.
3. Branch to the Sinoatrial (SA) Node in 40% of population.
WHAT IS THE VENOUS
1. Coronary Sinus, which runs in Coronary sulcus (Posterior AV
DRAINAGE OF HEART?
groove). It is a continuation of the Great cardiac vein and drains
into the Right atrium. It receives blood from:
a. Great Cardiac Vein.
b. Middle Cardiac Vein.
c. Small Cardiac Vein.
2. Anterior Cardiac Veins, with open directly into Right atrium.
WHAT ARE THE CONTENTS
1. Right AV groove: Right coronary artery and Small cardiac vein.
OF HEART GROOVES? 2. Left anterior AV groove: Left coronary artery.
3. Left posterior AV groove: Coronary sinus.
4. Anterior IV groove: Anterior IV artery and Great cardiac vein.
5. Posterior IV groove: Posterior IV artery and Middle cardiac v.
WHAT IS THE CONDUCTIVE
SYSTEM OF THE HEART? 1. Sinoatrial (SA) Node, which is located in the back wall of right
atrium near the entrance of Superior vena cava.
- It initiates impulses 70-80 times per minute without any nerve
stimulation from the brain (Basic rhythm of heart = Pacemaker).
- Its impulses move through both atria causing them to contract.
- Also, the impulses reach the AV node (2nd part of conduction).
2. Atrioventricular (AV) Node, which is located at the bottom of
the right atrium near its septum.
- Impulses have a delay because they move slowly in AV node. This
gives time for atria to finish contraction before ventricles start.
3. Atrioventricular Bundle (Bundle of His) is collection of heart
muscle specialized for electrical conduction.
- It gives right and left bundle branches, which extend along right
and left sides of interventricular septum to bottom of the heart.
- Then, these bundles branch to form the Purkinje fibers, which
transmit impulses to the Myocardium (Heart muscles).
- Bundle of His, Bundle branches, and Purkinje fibers transmit
impulses quickly, causing contraction of both ventricles.
WHAT ARE BLOOD VESSELS?
Blood vessels are tubes carrying blood from the heart to tissues or
from tissues to the heart. There are 3 types of blood vessels:
1. Arteries, which carry blood away from the heart.
2. Veins, which carry blood towards the heart.
3. Capillaries, where nutrients and gas exchange occur.
- Arteries have thicker walls and narrow lumen, while veins have
thinner walls and wider lumen. Veins have valves (Back-flow).
• Wall of blood vessels consists of 3 layers:
1. Tunica externa: Connective tissue.
2. Tunica media: Smooth muscles fibers (constrict in arteries to
regulate blood flow and blood pressure).
3. Tunica interna: Endothelium.
- Capillary walls are only one cell thick to allow exchange of gases
and nutrients with tissues.
