MRC National Institute for Medical Research, London
Science for Health
2005 meeting - Spectacular plumbing
Scientific insights into the heart and circulatory system
Human engineers sometimes give the impression that anything is within their power but the mammalian circulatory system is a marvel of ingenuity, orders of magnitude more sophisticated than anything that the human mind has yet conceived.
A remarkable aspect of human biology that we rarely think about is that the heart can keep beating once a minute for perhaps a hundred years. More remarkably, at the time a child is born the muscle cells — the cardiomyocytes — will mostly have divided for the last time.
'Creating a heart that can last a hundred years' was the theme of Dr Tim Mohun’s wide ranging presentation. Comparing the hearts of frogs and mammals, he showed how the architecture of the heart could confer important adaptations to particular habitats. The heart takes shape early in the life of a vertebrate embryo, first as a simple linear tube that acts as a peristaltic pump. This is transformed into the well-known multi-chambered organ, with valves, blood vessels and an electrical system for controlling the heart beat. For developmental biologists the most fundamental question is “how does any organ system emerge in an embryo?” The general answer is that particular genes act as switches that “turn on” more sets of genes, starting a process that creates heart tissue in the right place at the right time. Understanding the genes involved in the early stages of heart formation is going to be of great importance in understanding congenital heart disorders. Many of these disorders are treated satisfactorily by surgery but with a more profound knowledge of heart development better solutions may be possible.
The circulatory system has a vital role in transporting cells, nutrients and waste materials of all kinds through every part of the body, but the physical state of blood remains remarkably constant normally. Dr Tom Carter discussed 'Miraculous self-maintaining plumbing' and how in evolution, vertebrates have evolved a highly efficient method of repairing damage using a system that can stop “leaks” by making a blood clot in a wound. This system has to be under the most delicate control. If a blood clot blocks a blood vessel, oxygen may be excluded from critical tissues. In middle age, blood clots of this type are more likely, resulting in heart attacks and strokes. Genetic disorders are well known that cause excessive or ineffective clotting, with serious consequences for the victim. Cells lining blood vessels ultimately regulate Blood clotting and many other aspects of blood physiology. They secrete proteins that favour blood clotting (von Willebrand’s factor, vWf) and Factor VIII) and others that antagonise clotting, regulate blood flow and mediate local inflammatory responses. Understanding the capabilities of these cells is an important objective of scientists interested in the physiology of the blood stream.
© MRC National Institute for Medical Research
The Ridgeway, Mill Hill, London NW7 1AA
Top of page