Zoology Assignment Help >> Blood Circulation System, Blood Vessels, Structure of a Blood Vessels

BLOOD CIRCULATION SYSTEM

(1) Open type of blood circulatory system: The circulating fluid (known as haemolymph or perilymph) is not only present in the vessels but also present in the blood spaces or lacunae or sinuses e.g. some arthropods, molluscs and annelids. blood remains(2) Close type of blood circulatory system: It is present in most of the annelids and all vertebrates.

BLOOD VESSELS

The blood remains confined in the blood vessels. of the body bDifference between- artery and vein:

Artery	Vein
Carry blood from heart to tissues.Pressure of blood is high and flows forcibly.	Comparatively low pressure and Constant speed.
Narrow lumen	Wide lumen
. Does not collapse while empty	Collapse while empty
Situated deeper in the body	Situated superficial in the body
No valve or valve like structure are found except some specialised arteries	Valves usually in pairs are present and are called watch pocket valve. They prevent back flow of blood.
Colour is pink or bright red	Colour is deep red or violet
Carry oxygenated blood except pulmonary artery	Carry deoxygenated blood except pulmonary vein

Structure of a blood vessel:

Three layers-

1. Tunica externa or Tunica adventitia: Of connective tissue, unsCarry deoxygenated blood except pulmonary vein

Structure of a blood vessel:

Three layers-

1. Tunica externa or Tunica adventitia: Of connective tissue, unstriped muscle fibre, elastic fibre etc.

2. Tunica media: Of circular unstriped muscle.

3. Tunica Interna or Tunica intina: Of endothelial tissue.

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