Question

give short answers:

16) Discuss the movement of solutes across vascular capillary walls

17) Givean illustrated account of the histology of arteries and veins

18) Describe the structure and function of the valves in the cardiovascular system. Include in your essay reference to the valves of the heart and vasculature.

19) Discuss the formation of lymphatic fluid and its movement through the lymphatic system.

20) Write short notes on both of the following features of a normal healthy

21) heart: a. The cardiac valves b. The cardiac conduction system.

22) Describe the differences in the blood pressures that may be observed within different regions of the cardiovascular system. Include in your essay brief descriptions of the mechanisms responsible for the observed pressures.

Answer 1

1. Maximum movement across capillaries occur via process of diffusion. During diffusion, the substances move from their higher concentration to lower concentration. The blood capillaries have small pores in them which allow passage of small substances.

Movement of larger molecules ocurr via various ions channels which facilitate the movement of substances.

17. Arteries and veins both are type of blood vessels. In both, the wall is made up of endothelial cells, smooth muscle and matrix (collagen and elastin).

The wall of both are arranged in 3 layers

-tunica intima

-tunica media

-tunica adventitia

Arteries have thicker wall then veins.

Veins have larger diameter of lumen than arteries and thinner wall.

18. The human heart has 4 valves. Valves of heart permit the flow of blood through heart in only one direction.

1. Atrioventricular valves. Left atrioventricular valve is also called mitral or bicuspid valve. It is formed by two cusps or flaps.

Right valve is also known as tricuspid valve and made up of 3 cusps.

Atrioventricular valve open only towards ventricles and prevent the backflow of blood into atria.

2. Semilunar valve.- present at the opening of systemic aorta and pulmonary artery and are known as aortic and pulmonary valve respectively.

Semilunar valve open only towards the aorta and pulmonary artery and prevents the backflow of blood into the ventricles.

19. Lymph is formed from interstitial fluid, due to the permeability of lymph capillaries. When blood passes via blood capillaries in tissue, 9/10th of fluid passes into venous end of capillaries from the arterial end. Remaining 1/10th of fluid passes into lymph capillaries, which have more permeability than blood capillaries.

So, when lymph passes through lymph capillaries, the composition of lymph is more or less similar to interstitial fluid including protein content. Protein enters lymph vessels.