Lacrimal apparatus consists of lacrimal gland lying in superolateral portion of the orbit and a series of lacrimal ducts that drain the secretion into the nasal cavity. The excretory ductuli of lacrimal gland (10-15) open into conjuctival sac of upper yeylid (superior rivus). With each blink of the eyelids, tears passe medially and downward and drains into lake and two small openings, called lacrimal puncta on both sides of the lacrimal caruncle. From here, tears drains through the lacrimal canaliculus into the lacrimal sac and continious through the nasolacrimal duct to the inferior meatus of the nasal cavity.
Optic nerve is a part of visual analyser. Three neurons of visual tract are located in retina: 1 – fotoreceptors rods and cones, 2 – bipolar cells and 3 – ganglionic (multipolar) cells. Axons of third neurons form the II Optic nerve, which passes through the optic canal and get the cranial cavity. Medial fibres of the optic nerve pass to the opposite side and form the optic chiasma. Lateral fibres part do not cross each other and keep their own side. Then fibres of the optic nerve form optic tract wich get the subcortical sight centres (lateral geniculate
body and superior colliculus of midbrain). Then 4th neurons are located under pulvinar thalami. Their axons run through the posterior leg of internal capsule (visual radiation) and reach cortical visual analyser in calcarine sulcus (occipital lobe).
Axons of optic tract contact with cells in accessory oculomotor /parasympathetic/ nucleus (Yakubovych-Edinger-Westphal`s) by means of intermediate neuron. There are link for realising the pupillar reflex and accomodation. Axons of fifth neurons run in composition of oculomotor nerve get a ciliary ganglion, where sixth neurons positioned. Their axons pass with short ciliary nerves into eyeball and give innervating for ciliary and sphincter pupillae muscles. This reflex does not depend on our will and consciousness.Поділитися цим: