Master Structure Of The Heart For Mdcat 2022

In this article, we will try to master the basic anatomy of the heart. We will also trace the pathway of the blood through the heart. This will enable you to answer each and every question on this topic. In the end, we will have some important questions on this topic to give you an idea of the type of questions asked from here in Mdcat.


Introduction: The heart we know is a muscular pumping organ. The function of the heart is to keep circulating the blood in the blood vessels by means of pressure generated as a result of the contraction of its musculature. The heart is made of a specialized muscular tissue known as cardiac muscle.
Origin: The heart is mesodermal in origin.
Location: The heart is located in the thoracic cavity in the mediastinal space(the region between the two lungs). The heart is slightly tilted towards the left as the left side of the heart is bulkier due to the greater musculature of the left ventricle.

 

Covering around the heart:  The heart is covered by a tough connective tissue sac known as the pericardium. The pericardium is double-layered, an outer fibrous pericardium and inner serous pericardium. The serous pericardium has further two layers, the one that lines fibrous pericardium on the inside is the parietal layer of the serous pericardium and the one that covers the heart is the visceral serous pericardium. There is a potential space between the visceral serous pericardium and parietal serous pericardium known as the pericardial cavity which is fluid-filled. These coverings provide a frictionless environment for the heart to contract and relax and also prevent it from over-expanding.
Layers Of The Heart: The sequence of heart layers from outside to inside is:

  • Epicardium(visceral layer of the serous pericardium)
  • The myocardium (cardiac muscle)
  • The endocardium(squamous endothelial layer)
Basic anatomy of the heart: The human heart is four-chambered. The upper two chambers are called atria which are separated by the interatrial septum. The lower two chambers are called ventricles which are separated by the interventricular septum.
The left ventricle is the thickest chamber of the heart in terms of its musculature because it has to pump blood to all parts of the body.
Leaving the left ventricle is the aorta which is the largest artery of the body whereas the pulmonary artery leaves the right ventricle.
The two largest veins of the body, the superior and inferior vena cava drain blood from the upper and lower parts of the body to the right atrium.

Valves of the heart: Valves are present in the heart to ensure one-way blood flow and prevent regurgitation(backflow of blood). There are two types of valves:



The atrioventricular valves: These valves are present between the atria and ventricles. They are of two types one is the tricuspid valve which has three cusps and is present between the right atrium and the right ventricle the other is the bicuspid or the mitral valve present between the left atrium and the left ventricle.

The semilunar valves: These valves are present between the ventricles and the arteries leaving them. One is present between the right ventricle and the pulmonary artery and the other is present between the left ventricle and the aorta.
The direction of blood flow through the heart: The heart pumps the blood in two circuits the pulmonary and the systemic circuit. Oxygenated blood flows in the systemic circuit of the body whereas deoxygenated blood flows in the pulmonary circuit of the body.
The superior and inferior vena cava collects deoxygenated blood into the right atrium. This deoxygenated blood is pumped into the right ventricle through the tricuspid valve. The right ventricle then pumps the deoxygenated blood into the pulmonary circuit(lungs) for oxygenation via the pulmonary artery through the semilunar valve. The lungs make the blood oxygenated. This oxygenated blood is returned back to the left atrium via the pulmonary veins. The left atrium pumps blood into the left ventricle through the semilunar valve.
So the direction of blood flow through the heart is:
👉 Superior and inferior vena cava👉right atrium👉right ventricle👉pulmonary artery👉lungs👉pulmonary veins👉left atrium👉left ventricle👉aorta
Expected Mcqs from this topic:
The most muscular chamber of the heart is 
a. Right ventricle
b. Left ventricle
c. Right atrium
d. Left atrium
Ans: B is correct because the left ventricle has to pump blood to all parts of the body so it needs to be more muscular.


2. Backflow of blood from the aorta to the left ventricle is prevented by which valve
a. Semilunar valve
b. Tricuspid valve
c. Mitral valve


3. Select the correct statements:
a. Both atria contract at the same time
b. Artia and ventricles both contract at the same time
c. Both ventricles contract at the same time
d. Atria contract first followed by ventricular contraction
Ans. a,c, and d statements are true because atria contract at the same time to drain ventricles. Similarly, ventricles contract simultaneously to pump blood into the two circuits mentioned earlier. Atria contracts first so that ventricles are filled up with blood which is followed by ventricular contraction to pump blood throughout the body.


4. How many pulmonary veins are in the human body:
a. 1
b. 2
c. 4
d. 6
Ans. There are four pulmonary veins that drain oxygenated blood from both the lungs to the left atrium