Question

1. Differentiate between arteries, veins, and capillaries.

2. Describe the three tunics of a typical blood vessel.

3. Describe the three types of arteries based on structure and function.

4. What are the three main arterial sense organs, what do they sense, and where are they found?

5. Describe the differences between a continuous capillary, a fenestrated capillary and a sinusoid.

6. What are precapillary sphincters?

7. Why are veins called the capacitance vessels?

8. Briefly describe the five type of veins:

   • • • • •

9. What is the simplest and most common circulatory route of blood?

10. What is the portal system, and how does it differ from the simplest circulatory route?

Answer 1

1)

	Arteries	Veins	Capillaries
Pressure	High	low	low
Valves	no	yes	no
Lumen diameter	narrow	wide	narrowest
Wall	thick	thin	very thin
Layers	tunica adventitia Tunia media Tunica intima	Tunica adventitia Tunica media Tunica intima	Tunica intima only.
Functions	carry blood from heart to periphery	carry blood from periphery to the heart	exchange of nutrients

2)

TUNICA INTIMA:- it is the innermost coat of the blood vessel. It consists of

• Endothelial lining which is very smooth and consists of single layer of cells
• Basal lamina lines the external aspect of endothelium
• Sab endothelial connective tissue is a delicate layer connective tissue
• Internal elastic lamina is a thin membrane formed by elastic fibres

TUNICA MEDIA:- it is the middle thickest coat of The vessel wall. It consists of smooth muscles and elastic tissue. The ratio of these tissues varies from vessel to vessel. on the outside tunica media is lined by a membrane formed by elastic fibres called the external elastic lamina.

TUNICA ADVENTITIA:- it is the outermost coat of the vessel wall. it is made up of connective tissue in which collagen fibres are prominent. This layer prevents undue stretching and distension of the blood vessel.

3) Three types of Arteries are:-

1. Large arteries: they have a dominant elastic tissue in their tunica media which provides them property of a distensibility and elastic recoil. Example: aorta
2. Medium arteries:- in these arteries the elastic tissue in both intima and media is much less and this proportion of smooth muscle increases. Example:- brachial artery.
3. Arterioles:- they have a characteristically no elastic tissue. Their media consists of a thick layer of smooth muscles and they have a relatively narrow lumen. Because of their structural characteristics they act as resistance vessels.

4) Three main arterial sense organs are:-

Carotid sinuses:- they are baroreceptors present in walls of internal carotid artery and sense rise in blood pressure and signals brainstem to increase the Parasympathetic supply.

Carotid bodies:- they are chemoreceptors located in the carotids. They sense the change in blood chemistry and alter the ventilation to normalise the change

Aortic bodies:- they are chemoreceptors located in the bifurcation of aorta. They have same role as that of carotid bodies.