The cardiovascular or circulatory system is responsible for the movement of blood throughout the body, with the purpose of delivering oxygen and nutrients to tissues, disposing waste products from the tissues plus carrying hormones as cellular signals.

It consists of a pump (the heart) and an extensive network of channels (the arteries, capillaries and veins). The arteries carry blood away from the heart; the capillaries allow for exchange of material between the blood and the tissues; the veins return the blood to the heart.

In addition to blood vessels, a second network of channels, the lymphatic vessels, will also be studied in this exercise. These vessels carry lymph (intercellular fluid) which is filtered through lymph nodes and eventually returned back to the blood.

Learning Objectives:

• To understand the overall organization and histological features of the heart and major blood vessels.
• To recognize the histological features that distinguish arteries from veins.
• To recognize arterioles, capillaries and venules in LM preparations and understand how their structures relate to their functions.
• To be able to recognize lymphatic vessels

Let's first look at the heart.