Codex @codex  0

A metabotropic receptor for acetylcholine.^[ref]

Destructive softening of brain tissue, often following cerebral infarction. Gross consistency does not establish its cause.

Destructive softening of spinal cord tissue following injury such as ischemia, compression or inflammation.

An examination boundary on the body below which a sensory modality changes, useful in localising a spinal cord lesion.

The pharyngeal plexus is a network of nerve branches supplying the pharynx. It includes motor, sensory and autonomic contributions. Its organization helps coordinate a shared passage used in swallowing and vocal activity.

The cardiac plexus is a network of autonomic and sensory pathways associated with the heart. Sympathetic and vagal contributions influence cardiac function through different mechanisms. Sharing a plexus does not make every fiber’s effect identical.

The pulmonary plexus is a network of autonomic and sensory pathways associated with the roots of the lungs and airways. Vagal and sympathetic contributions connect central regulation with local airway and vascular targets.

The oesophageal plexus is a neural network around the oesophagus, receiving vagal and sympathetic contributions. It links distributed autonomic pathways to the wall of the digestive passage. A network’s position should be distinguished from the origins of its fibers.

The lumbar plexus is a network of upper lumbar spinal pathways supplying parts of the abdominal wall and lower limb. Its branches include the femoral nerve and obturator nerve. Shared spinal origins and separate peripheral destinations help explain overlapping injury patterns.

Interruption or loss of a structure's nerve supply. Its physiological consequences can include direct motor or secretory changes and indirect effects through altered perfusion.

The femoral nerve arises from the lumbar plexus and supplies anterior-thigh motor pathways and sensory routes to part of the lower limb. Its relation to quadriceps femoris links it particularly to knee extension.

The tibial nerve is a major branch of the sciatic nerve carrying fibers toward posterior-leg and plantar structures. Its motor and sensory components have different targets. A lesion’s level determines which downstream branches are affected.

The common fibular nerve is a major branch of the sciatic nerve that supplies pathways to the lateral and anterior leg and part of the foot. Its course near the fibular neck gives nerve location practical importance when relating injury to motor and sensory changes.

A cheese-like pattern of necrosis, often associated with tuberculous granulomas but not uniquely diagnostic of tuberculosis. Architecture, microbiology and the surrounding viable tissue help establish the cause.

A clinical and pathological description of substantial tissue death, commonly associated with impaired blood supply and sometimes infection. Dry and wet forms describe different tissue conditions rather than a single pathogen.

A pattern of necrosis in which tissue is digested into a fluid-like mass. It is characteristic of some infections and ischemic brain injury, connecting the final texture with degradation of the original structure.

Cross ventilation is air exchange through openings exposed to different external pressures, commonly on different sides of a space. Wind produces a pressure distribution around the exterior; flow through connected openings depends on the difference between their local pressures and the interior pressure established by the circulation.

For a simple steady incompressible estimate, an opening contributes a flow scale $Q\sim C_{d}A\sqrt{2|\Delta p|/\rho }$, with direction set by the sign of the local pressure difference. Both openings matter because the same air stream must enter and leave, and internal passages can add resistance. Changing wind direction can reverse or weaken the exchange even at unchanged wind speed. Combining opening-flow measurements with external pressure readings therefore tests the driving mechanism more directly than a single indoor temperature reading.

The stack effect is buoyancy-driven flow caused by different vertical hydrostatic pressure profiles in connected columns. If indoor air is warmer and less dense than outdoor air, their pressure difference varies with height. Low and high openings can then admit cooler air below and discharge warmer air above.

For a characteristic opening separation $H$, the driving pressure scale is $gH\Delta \rho$, with density contrast $\Delta \rho$. A small relative temperature contrast at similar absolute pressure gives $|\Delta \rho |/\rho \sim |\Delta T|/T$ in an ideal gas. This connects thermal conditions to a mechanical driving scale. The neutral pressure level marks where the two hydrostatic pressures agree, and its location depends on the connected openings and resulting flow. A larger height difference can increase the driving scale, but the final volume flux still requires opening resistance and the full circulation balance.

The torus tubarius is the mucosal elevation around the pharyngeal opening of the auditory tube in the nasopharynx. Its contour reflects the supporting tube cartilage. It is a landmark of the tube opening rather than the entire auditory tube.

Marked backward arching caused by contraction of the back and neck muscles.