Written by: Liz Paton, MSc

Blood Anatomy Overview

Your blood is a thick fluid that flows throughout your body that is responsible for oxygenating the cells in your body and removing carbon dioxide. It keeps you healthy by fighting infections from germs, and it carries hormones around your body. Blood forms blood clots to prevent over-bleeding, and it helps you regulate a healthy body temperature.

Anatomy of Blood

Blood is made up of a combination of liquids and solids, hence why blood is thicker than water. It is comprised of plasma, white blood cells, red blood cells and platelets.

Plasma

Plasma is the liquid that is responsible for carrying vital components throughout the body to where they are needed. This yellowish liquid is the largest constituent of blood, making up 55%. Plasma carries waste products, nutrients, antibodies, clotting proteins, hormones and more throughout the circulatory system.

Red Blood Cells

The primary function of red blood cells (RBCs) is to carry oxygen from the lungs to the rest of the body and carry carbon dioxide back to the lungs with a haemoglobin protein. Haemoglobin contains a red-coloured compound called haem, and this is the reason our blood is red. Blood types are determined by certain antigens found in red blood cells. RBCs make up 40 to 45% of our blood.

White Blood Cells

The primary function of white blood cells (WBCs), also known as leukocytes, is a defence against infection and disease. Making up about 1% of our blood, WBCs are produced in the bone marrow; they each have a nucleus and play the important role of ingesting foreign materials and debris. There are five types of WBCs, none of which contain haemoglobin. The different types include monocytes, lymphocytes, neutrophils, basophils, and eosinophils.

Platelets

Platelets, also called thrombocytes, are the tiny blood cells responsible for blood clotting. Blood clotting is important to stop bleeding. They are created in your bone marrow and make up less than 1% of your blood.

Our Blood Poster shows you a great visual representation.

Circulatory System Anatomy

The circulatory system is the organ system that allows blood to move throughout your body. It begins at the heart, the organ that pumps oxygenated and deoxygenated blood around our body. Deoxygenated blood is transported into the heart from the rest of the body via the veins. The blood is then transported to the lungs, where it becomes oxygenated and flows back into the heart, where it is transported back to the rest of the body through arteries.

The blood vessels are responsible for transporting blood around the body. Arteries carry oxygenated blood from the body to the heart. Arterioles are vessels that branch out from arteries and are much smaller. Arterioles then form into capillaries  which are very small blood vessels that supply blood to small structures within the body. Capillaries connect to venules  (small veins) which then connect to veins  and transports deoxygenated blood back to the heart.

There are two types of circulation:  pulmonary circulation and systemic circulation. Pulmonary circulation is the circuit involving the heart and the lungs. Systemic  circulation involves the circuit involving the heart and the rest of the body. Coronary circulation is a form of systemic circulation and involves the blood supply to the heart via the veins and arteries of the heart.