Kirioroshi- Death by a Single Cut

 

Kirioroshi is probably the most universal coup de grace within Iaido and it is the technique used to send ones enemy directly to Buddha, no passing  Go and collecting £200 with this cut. Unlike most martial arts,  the techniques of Iai were forged in actual combat-to-the-death, and so one must assume it’s exalted place at the top of the pantheon of sword cuts must be due to it’s ability to incapacitate and cause death rapidly.

For the purposes of this piece, we will assume kirioroshi is perform directly down the midline cutting through the full depth of the skull. 

The brain receives about a fifth of cardiac output and a continuous flow of arterial blood, bringing oxygen and nutrients (the brain can only use glucose as a source of energy) and flushing away the by-products of metabolism is vital for normal function. Indeed, a reduction of cerebral blood flow bu occluding the arteries supplying the brain (two internal carotid arteries entering the skull via the carotid canals and two vertebral arteries running through bony channels in the cervical vertebrae-the vertebral canals- and into the foramen magnum) produces a reflex increase in heart rate and cardiac contractility and dilation of the cerebral vessels to lower resistance to flow. Cessation of cerebral blood flow will produce unconsciousness in 10-15 seconds and irreversible brain damage after a few minutes before death. Thus the brain is highly vascular with many, many visible arteries and veins and tint penetrating arteries that dive deep into the mass of the brain.

 

 

 

 The brain is highly vascular since it requires a large blood supply to keep it functioning normally. The top diagram shows the extent of the vessels on the surface of the brain. The middle image shows the larger vessels by injecting a contrast medium and the lower shows the the tiny vessels network on the surface of the brain which give rise to penetrating arteries that dive down into the full thickness of the cortex.The lower diagram shows the relationship between the heart, the major arteries and the vessels to the brain.

 

It is perhaps dawning upon the reader as to why kirioroshi is so devastating a cut since it interrupts the vast flow of blood very efficiently. In fact ,it produces huge haemorrhage, the blade will cause extensive damage to the neural tissue which has a tendency to cease their firing of electrical messages (action potentials) when sustaining trauma thus stopping meaningful consciousness. The unfortunate enemy will likely be incapacitated in seconds and dead within a few tens of seconds upon receipt of a textbook kirioroshi.

 

It is hardly surprising, therefore, that such emphasis is placed upon training this technique within Iai.