The Amazing Human Body: Blood
Did You Know? About 7-8% of your body weight is blood? Let’s marvel at this incredible river of connective tissue
Revered for millennia for its life-giving role, romanticised and dramatized in literature and entertainment – the word blood appears in every single Shakespeare play – alarming for many, stomach-churning for some, there’s no doubt blood holds a fascination for humans. We seem to instinctively know at a very young age how important this fluid is.
Blood is actually a type of connective tissue, a connective tissue that can travel! Blood’s main job is to do just that: to deliver oxygen to lungs and tissues, and to take waste products like carbon dioxide away, but it also delivers chemicals such as hormones and enzymes, helps regulate body temperature, and fights infection.
Did You Know? A little over half of what we collectively call ‘blood’ is plasma (a soupy mix of water, proteins, nutrients, electrolytes, hormones and gases), while almost all the rest is made up of red blood cells, with white blood cells and platelets occupying a tiny but important 1% of blood’s volume. Each ingredient in blood is busy performing different functions.
Red blood cells (RBCs) are in charge of the delivery of oxygen and nutrients, and the collection of waste products. Indeed, they are the only type of blood cell capable of transporting oxygen.
The colour of blood is derived from the hemoglobin in red blood cells. ‘Heme’ refers to the iron-containing molecule therein, while ‘globins’ are little chains of protein. A healthy red blood cell is shaped somewhat like a pizza, a disc shape with a sunken centre through which oxygen and carbon dioxide can diffuse.
Red blood cells will circulate the body for about 2 months before they are broken down by our little cleaning scavenger cells called phagocytes. From the rise of new blood cells, a complex feedback loop ensues, involving messages from one area to another about the rise and fall of elements such as oxygen and the dispatch of chemical instructions to produce new blood cells and breakdown old ones, keeping the body chugging away in its preferred homeostatic balance.
Did Your Know? Most of your blood began its existence in your bone marrow! All blood cells begin life as stem cells, a type of cell ‘starter kit’ that can give rise to several specific types of cells. Lymphocytes (a type of white blood cell involved with immunity) are formed in lymphatic tissue, but a whopping 95% of your blood has its origin deep within your bones.
White blood cells are associated with immunity. They are like little soldiers, travelling around your body looking for foreign invaders like bacteria, viruses, and fungi. Our white blood cell count can be lowered by certain medications like antibiotics, illnesses, overwhelming infection, or when the body is simply not producing enough, and it is thought nutrients like adequate vitamin-C help us maintain white blood cell production.
Did You Know? Australian scientists in Melbourne were able to film a white blood cell dying, where it radiated molecules into neighbouring cells. It is thought that the white blood cell may be capable of trying to warn other white blood cells about the presence of an attacking pathogen!
Plasma’s key role is to accept the collected waste and take it to organs like the kidneys and liver for excretion, but it is also busy helping regulate body temperature, maintaining fluid pressure in the blood, and helping with immune function.
Did You Know? There are 8 main blood types, Type O being the most common and known as the ‘universal donor’ as it can be given to anyone. Blood types are determined by the genetically-determined presence of certain sugars and proteins on the surface of the cells, known as ‘antigens’. If the wrong type is introduced during a blood transfusion, our body interprets it as an invader and goes into fight mode. But, as blood is produced in bone marrow, if we receive a bone marrow transplant from someone with a different blood type, it can eventually change our blood type!
We often talk about blood “flowing through our veins”, but that really only refers to blood that has already collected its waste products and is headed back towards the heart to be ‘cleaned’. Freshly oxygenated blood leaves the heart and travels in arteries, while capillaries are tiny, tiny, tiny blood vessels that form the junction between veins and arteries. Capillaries are the business end of nutrient, gas and waste exchange!
Did You Know? The average adult has about 5 litres of blood in them, and it zips around your body so fast that in one day your blood will traverse almost 20,000 kilometres – that’s across Australia about 5 times in a single day!
Pause for gratitude
Have you thanked your amazing body yet today for the amazing work is it doing for you every second of every day, to keep you alive, in balance and well? Place your hands over your heartspace and give your body some gratitude.
Written by Nicole Small, The Yoga Institute