In 1920, Danish physiologist August Krogh was awarded the Nobel Prize in Physiology or Medication “for his discovery of the capillary motor regulating mechanism.”
His work addressed a elementary query: how does muscle obtain sufficient oxygen when its demand rises sharply throughout train? Krogh confirmed how modifications within the capillary circulation might assist meet this elevated demand by bringing blood nearer to muscle fibres and growing the floor out there for oxygen alternate.
The work had necessary implications for drugs as a result of understanding how oxygen reaches tissues is central to situations wherein blood provide is impaired, together with heart problems, peripheral vascular illness, diabetes and wounds that fail to heal. The rules of microcirculation and tissue oxygenation that Krogh helped set up are actually related to understanding tissue harm, wound therapeutic, train physiology and the results of impaired blood circulation.
From zoology to physiology
Schack August Steenberg Krogh was born on November 15, 1874, in Grenaa, Denmark. He entered the College of Copenhagen in 1893, initially learning drugs earlier than turning to zoology.
On the college, he joined the laboratory of physiologist Christian Bohr and have become all in favour of respiration and the alternate of gases in dwelling organisms. He obtained his zoology diploma in 1899 and continued working in Bohr’s laboratory.
Krogh mixed experimental biology with quantitative measurements and developed devices for learning physiological processes. His analysis included respiration, gasoline alternate and water and electrolyte regulation.
In 1916, he grew to become professor of zoophysiology on the College of Copenhagen.
The oxygen provide drawback
Krogh targeted on how oxygen strikes from blood to tissue.
Muscular tissues can enhance their oxygen consumption significantly throughout train. Oxygen carried within the blood should diffuse from capillaries via surrounding tissue earlier than reaching particular person cells. The space between a cell and a perfused capillary subsequently impacts oxygen supply.
Krogh investigated capillary distribution in muscle and in contrast resting and lively tissues. He noticed that extra capillaries appeared to comprise blood when muscle tissue have been lively.
In papers printed in The Journal of Physiology in 1919, he mixed these observations with mathematical calculations of oxygen diffusion. He proposed that bringing extra capillaries into practical use throughout exercise would enhance the out there alternate floor and shorten the space oxygen needed to journey via tissue.
This work fashioned the premise of what grew to become often known as the Krogh cylinder mannequin, a conceptual mannequin describing oxygen diffusion from a capillary into the encompassing tissue.
The Nobel-winning discovery
Krogh went additional than describing variations in capillary perfusion. He proposed a capillary motor regulating mechanism, via which capillary diameter and blood content material might change in keeping with the practical wants of tissue.
The Nobel Committee recognised this work in 1920.
In his Nobel lecture, Krogh described how the variety of blood-filled capillaries different with the exercise of tissue. He argued that extra capillaries have been introduced into use throughout muscular exercise, serving to enhance the world out there for oxygen alternate.
The invention shifted consideration in the direction of the microcirculation — the community of small vessels liable for delivering oxygen and vitamins to tissues and carrying away metabolic merchandise.
What trendy physiology says
Some parts of Krogh’s unique clarification have since been revised.
Trendy research don’t help the straightforward concept that skeletal-muscle capillaries are routinely switched between fully closed and open states. Nor are capillaries thought of the principal website of lively blood-flow regulation.
A lot of that regulation happens upstream, notably in arterioles. Trendy microscopy has additionally proven that many muscle capillaries are already perfused at relaxation.
Capillary recruitment is subsequently understood extra exactly as modifications within the sample and extent of capillary perfusion relatively than merely the opening of beforehand closed vessels.
Krogh’s central perception, nevertheless, stays necessary: the organisation of the capillary community and the space oxygen should journey via tissue are essential determinants of oxygen supply.
From capillaries to insulin
Krogh’s profession later intersected with one other main medical growth — insulin.
In 1922, he and his spouse, doctor Marie Krogh, travelled to North America. Marie had diabetes and inspired him to research the newly developed insulin therapy.
In the course of the journey, Krogh visited Toronto, the place Frederick Banting, Charles Greatest and their colleagues had developed strategies for producing insulin. Krogh subsequently obtained permission to supply insulin utilizing the Toronto technique in Scandinavia.
Again in Denmark, he labored with doctor Hans Christian Hagedorn and pharmacist August Kongsted. The primary Danish affected person was handled with insulin in March 1923, and Nordisk Insulinlaboratorium was established that 12 months.
Scientific legacy
Krogh continued learning physiology after receiving the Nobel Prize. His work on respiration, gasoline alternate and the microcirculation demonstrated how bodily rules and quantitative measurements may very well be used to know organic processes.
The Krogh cylinder stays a helpful conceptual mannequin for learning oxygen diffusion, though trendy analysis has refined the mannequin utilizing extra detailed data of blood circulation, oxygen gradients and the three-dimensional construction of capillary networks.
Krogh retired from the College of Copenhagen in 1945 however continued his analysis. He died in Copenhagen on September 13, 1949, aged 74.
Greater than a century later, oxygen supply to tissues is known to contain cardiac output, blood circulation, arteriolar regulation, capillary perfusion, blood oxygen content material, diffusion and tissue metabolism.
Krogh’s unique clarification has developed, however his resolution to review circulation on the microscopic degree modified the understanding of how blood provides particular person tissues. His work established the capillary community and oxygen diffusion as central to the examine of tissue oxygenation and microcirculation.
Printed – August 09, 2026 07:08 pm IST
