Circulation short questions chapter 12 Sindh board

 Chapter 12 short questions 

Q1: why higher animals need circulatory system?

Higher animals need a circulatory system to transport nutrients, gases, and waste products between cells, organs, and tissues throughout the body and longer distances and in short time.

Q2: why sa node is called pace maker of heart?

The SA node is called the pacemaker of the heart because it generates electrical impulses that set the rhythm for the entire heart to beat in a coordinated manner.

Q3: why the capillaries have single layer of endothelium?

Capillaries have a single layer of endothelium to facilitate the exchange of gases, nutrients, and waste products between the blood and tissues through a thin and permeable barrier.

Q4: what are lub and dub?

Lub and Dub are the sounds heard during a heartbeat. Lub is the sound of the atrioventricular (AV) valves closing when the ventricles contract, while Dub is the sound of the semilunar valves closing when the ventricles relax.

Q5: why circulatory system of arthropods is called open type?

The circulatory system of arthropods is called open type because the hemolymph (the fluid that circulates in their body) is not enclosed within vessels, but rather flows freely through the body cavity and directly bathes the organs and tissues.

Q6: why blood flow faster in arteries?

Blood flows faster in arteries because their walls are thicker and more elastic than veins, and the pressure generated by the heart's contractions pushes the blood forward with greater force.

Q7: distinguish between single circuit circulation and double circuit circulation

Single circuit circulation refers to a circulatory system in which blood flows through the heart and to the gills or lungs before returning to the heart and being pumped to the rest of the body, while double circuit circulation refers to a circulatory system in which blood flows through two separate circuits: one to the lungs for gas exchange and one to the rest of the body. Mammals have a double circuit circulation, while fish have a single circuit circulation.