Tag: basics of blood and heart

In a healthy individual, there are two normal heart sounds called lub and dub. Lub is the first heart sound. It is associated with the closure of the tricuspid and bicuspid valves at the beginning of systole. The second heart sound dub is associated with the closure of the semilunar valves at the beginning of diastole.

Human blood passes from the inferior vena cava into the diastolic right atrium of the heart because of a pressure differential between the atrium and the vena cava. This negative pressure gradient is created by atrial diastole and pulls blood to the atrium which is then pumped to the ventricles by contraction.

Due to one complete cardiac cycle, the two atria contract during the first 0.1 seconds, followed by ventricular systole for 0.3 seconds and finally joint diastole for 0.4 seconds. 

Out of all other leucocytes, the neutrophils (60-65%) are most abundant and the least are basophils (0.5-1%). Platelets are cell fragments produced from megakaryocytes. During the blood clotting, the enzyme thrombin converts inactive fibrinogens into active fibrins.. 

Hb contains a protein portion called globin and a pigment portion called haem. The haem portion consists of four atoms of iron, each capable of combining with a molecule of $O _{2}$. Thus, one Hb carries 4 molecules of $O _{2}$.

Nearly 20-25% of $CO _{2}$ is transported by RBCs whereas 70% of it is carried as bicarbonate in plasma. About 7% of $CO _{2}$ is carried in a dissolved state through plasma. About 97% of $O _{2}$ is carried by RBCs in the blood. About 3% of $O _{2}$ Is transported in a dissolved state through the plasma.

The sieve tubes are supporting cells in the conducting tissue of the plant and are characterised by the absence of a nucleus. 

Hemoglobin (Hb or Hgb ) is an iron-containing protein present in Erythrocytes or Red blood cells (RBC) of almost all vertebrates. Each hemoglobin is made up of 4 subunits, 2 alpha subunits, and 2 beta subunits. Each subunit surrounds the central heme group that contains iron and binds to one oxygen molecule. It carries oxygen from lungs to tissues. It also helps in the transportation of carbon dioxide, hydrogen ions back to the lungs from the tissues. Hence RBC helps in transportation of gases while WBC takes parts in immune function and protects the body from infectious diseases and foreign invaders(bacteria, viruses other pathogens) and platelets in blood coagulation.