[I wonder if some these are biologically linked to the danger triangle: mammalian diving response, philtrum (upper lip acting as air valve), hooded nose (uniquely human), vocalization-humming(Nitruc Oxide produced in paranasal sinuses), photic sneeze-pupillary dilation-dark adaptation, wet sinus diving, eustacean tubes, valsava maneuver, etc.]
https://en.wikipedia.org/wiki/Danger_triangle_of_the_face
The danger triangle of the face consists of the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla.[1][2] (pp345–346)Due to the special nature of the blood supply to the human nose and surrounding area, it is possible for retrograde infections from the nasal area to spread to the brain causing cavernous sinus thrombosis, meningitis or brain abscess.
This is possible because of venous communication (via the ophthalmic veins) between the facial vein and the cavernous sinus. The cavernous sinus lies within the cranial cavity, between layers of the meninges and is a major conduit of venous drainage from the brain.[3]
It is a common misconception that the veins of the head do not contain one-way valves like other veins of the circulatory system. In fact, it is not the absence of venous valves but the existence of communications between the facial vein and cavernous sinus and the direction of blood flow that is important in the spread of infection from the face. Most people, but not all, have valves in the veins of the face.[4]
The relationship between this area and a risk of cavernous sinus thrombosis was described as early as 1852.[5] In 1937 a study found that 61% of the cases of cavernous sinus thrombosis were the result of furuncles on the upper part of the face.[6] While the disorder has become less common with antibiotics, it still carries a high risk of death and needs to be treated aggressively with antibiotics and blood thinners.[7][8]
https://en.wikipedia.org/wiki/Danger_triangle_of_the_face
The danger triangle of the face consists of the area from the corners of the mouth to the bridge of the nose, including the nose and maxilla.[1][2] (pp345–346)Due to the special nature of the blood supply to the human nose and surrounding area, it is possible for retrograde infections from the nasal area to spread to the brain causing cavernous sinus thrombosis, meningitis or brain abscess.
This is possible because of venous communication (via the ophthalmic veins) between the facial vein and the cavernous sinus. The cavernous sinus lies within the cranial cavity, between layers of the meninges and is a major conduit of venous drainage from the brain.[3]
It is a common misconception that the veins of the head do not contain one-way valves like other veins of the circulatory system. In fact, it is not the absence of venous valves but the existence of communications between the facial vein and cavernous sinus and the direction of blood flow that is important in the spread of infection from the face. Most people, but not all, have valves in the veins of the face.[4]
The relationship between this area and a risk of cavernous sinus thrombosis was described as early as 1852.[5] In 1937 a study found that 61% of the cases of cavernous sinus thrombosis were the result of furuncles on the upper part of the face.[6] While the disorder has become less common with antibiotics, it still carries a high risk of death and needs to be treated aggressively with antibiotics and blood thinners.[7][8]
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