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Blood Vessels

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Topics

  • Blood Vessels: Structure and Functions
  • Capillaries
  • Definition: Artery
  • Definition: Vein
  • Definition: Arteriole
  • Definition: Venule
Maharashtra State Board: Class 8

Blood Vessels: Structure and Functions

In 1628, William Harvey described the mechanism of circulation in the body. He proposed the theory that our heart is a muscular pump by which blood is circulated throughout the body. He discovered the working mechanism of the heart valves.

The heart beats continuously, which causes blood to move through a network of blood vessels. There are two main types of these vessels: arteries and veins.

Blood Vessels Arteries Veins
Function Carry blood away from the heart to different parts of the body. Carry blood toward the heart from various parts of the body.

Oxygenated or Deoxygenated Blood

Most carry oxygen-rich blood, except the pulmonary artery, which carries oxygen-poor blood. Most carry oxygen-poor blood, except the pulmonary vein, which carries oxygen-rich blood.
Location Deep within the body to handle high-pressure blood flow. Closer to the surface of the body; often visible under the skin.
Structure Thick, strong walls with three layers for strength and elasticity. Thinner walls, less muscular, are suited for lower pressure blood flow.
Valves No valves, as high pressure keeps the blood flowing in one direction. Equipped with valves to prevent backflow of blood, especially against gravity.
Connection Branch into smaller vessels and eventually form capillaries. Formed by the uniting of capillaries to carry deoxygenated blood back to the heart.

Structure of Artery and Vein

Maharashtra State Board: Class 8

Capillaries:

Arteries branch out and decrease in diameter, eventually forming fine, hair-like vessels known as capillaries.

  • Capillaries have extremely thin walls made of a single layer of cells.
  • The thin walls of capillaries enable the easy exchange of materials between capillaries and surrounding cells.
  • Oxygen, nutrients, hormones, and vitamins are delivered to the cells through capillaries.
  • Waste materials from the cells are absorbed into the blood through capillaries.
  • Capillaries merge to form larger vessels called veins.
  • A network of capillaries exists in each organ, facilitating substance exchange and aiding the circulatory system.

Capillaries

CISCE: Class 10

Definition: Artery

An ARTERY is a vessel that carries blood away from the heart towards any organ.

CISCE: Class 10

Definition: Vein

A VEIN is a vessel that carries blood away from an organ towards the heart.

CISCE: Class 10

Definition: Arteriole

The smallest or the final branch of an artery is called an arteriole.

CISCE: Class 10

Definition: Venule

A venule is the smallest branch of a vein formed by the union of capillaries. It has a thin muscular coat and gradually joins with other venules to form larger veins.

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