Blood Vessels – Class 11 | Chapter – 18 | Biology Short Notes Series PDF

Blood Vessels: The blood vessel’s meaning is defined as a vessel that is present in the animal or human body, where the blood circulates. The vessels which carry the blood away from the heart are referred to as arteries, and their very small branches are referred to as arterioles. The very small branches that collect the blood from different parts and organs are known as venules, and they unite together to form veins, which in turn return the blood to the heart.

Blood Vessels

Layers of Blood Vessels

There are three layers of blood vessels: the tunica intima, the tunica media, and the tunica adventitia.

  • The tunica intima is the innermost layer and is made up of endothelial cells, which line the inside of the blood vessel. The endothelial cells secrete a layer of glycoprotein called the basement membrane, which separates the endothelial cells from the next layer, the tunica media.
  • The tunica media is the middle layer and is made up of smooth muscle cells and elastic tissue. The smooth muscle cells contract to change the diameter of the blood vessel and the elastic tissue helps the blood vessel recoil to its original size.
  • The tunica adventitia is the outermost layer and is made up of connective tissue. The connective tissue provides support for the blood vessel and also contains nerve endings, which help to control the diameter of the blood vessel.

Arteries and Veins

There are two types of blood vessels in the body- arteries and veins.

  • Arteries are responsible for carrying blood away from the heart, while veins carry blood back to the heart.
  • Arteries are thicker and stronger than veins, as they need to be able to withstand the high pressure of blood being pumped out of the heart.
  • Veins are thinner and less muscular than arteries, and are often described as ‘soft’ or ‘pliable’.
  • Arteries have a higher concentration of oxygen-rich blood, while veins have a higher concentration of carbon dioxide-rich blood.

Functions of the Blood Vessels

There are four main functions of the blood vessels:

1. Transporting blood throughout the body.

2. Regulating blood pressure.

3. Regulating body temperature.

4. Supporting the body’s immune system.

Disease Caused by breaking of Blood Vessels

A disease caused by blood vessels breaking is called a hemorrhagic disease. There are many types of hemorrhagic diseases, but they all have one thing in common: the breaking of blood vessels. This can lead to internal bleeding, which can be deadly.

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By Team Learning Mantras