Innervation in the context of "Endoneurium"

The cauda equina (from Latin tail of horse) is a bundle of spinal nerves and spinal nerve rootlets, consisting of the second through fifth lumbar nerve pairs, the first through fifth sacral nerve pairs, and the coccygeal nerve, all of which arise from the lumbar enlargement and the conus medullaris of the spinal cord. The cauda equina occupies the lumbar cistern, a subarachnoid space inferior to the conus medullaris. The nerves that compose the cauda equina innervate the pelvic organs and lower limbs to include motor innervation of the hips, knees, ankles, feet, internal anal sphincter and external anal sphincter. In addition, the cauda equina extends to sensory innervation of the perineum and, partially, parasympathetic innervation of the bladder.

The lacrimal apparatus is the physiological system containing the orbital structures for tear production and drainage.
It consists of:

• The lacrimal gland, which secretes the tears, and its excretory ducts, which convey the fluid to the surface of the eye; it is a j-shaped serous gland located in lacrimal fossa.
• The lacrimal canaliculi, the lacrimal sac, and the nasolacrimal duct, by which the fluid is conveyed into the cavity of the nose, emptying anterioinferiorly to the inferior nasal conchae from the nasolacrimal duct.
• The innervation of the lacrimal apparatus, which involves both a sympathetic supply through the carotid plexus of nerves around the internal carotid artery, and parasympathetically from the lacrimal nucleus of the facial nerve.

The blood supply to the lacrimal gland is provided by the ophthalmic artery with its branch - the lacrimal artery, while the venous blood is drained from this region via the superior ophthalmic vein. The lacrimal system is made up of a secretory system, which produces tears, and an excretory system, which drains the tears. The lacrimal gland is primarily responsible for producing emotional or reflexive tears. As tears are produced, some fluid evaporates between blinks, and some is drained through the lacrimal punctum. The tears that are drained through the punctum will eventually be drained through the nose. Any excess fluid that did not go into the punctum will fall over the eyelid, which produces tears that are cried.

Two-point discrimination (2PD) is the ability to discern that two nearby objects touching the skin are truly two distinct points, not one. It is often tested with two sharp points during a neurological examination and is assumed to reflect how finely innervated an area of skin is.

In clinical settings, two-point discrimination is a widely used technique for assessing tactile perception. It relies on the ability and/or willingness of the patient to subjectively report what they are feeling and should be completed with the patient's eyes closed. The therapist may use calipers or simply a reshaped paperclip to do the testing. The therapist may alternate randomly between touching the patient with one point or with two points on the area being tested (e.g. finger, arm, leg, toe). The patient is asked to report whether one or two points was felt. The smallest distance between two points that still results in the perception of two distinct stimuli is recorded as the patient's two-point threshold. Performance on the two extremities can be compared for discrepancies. Although the test is still commonly used clinically, it has been roundly criticized by many researchers as providing an invalid measure of tactile spatial acuity, and several highly regarded alternative tests have been proposed to replace it.