Extrinsic ocular muscles subdivide into recti (straight) and oblique
They originate in common annular tendom and insert into sclera and can rotate eyeball on frontal and vertical axis. As result pupilla moves up, down laterally and medially. Superior oblique muscle psses through a pulleylike cartilagenous loop, the trochlea, before attaching to the eyeball. Levator palpebrae superioris muscle elevates upper eyelid.
Periosteum of orbit is ‘periorbita’ forming the cover of bones and passes through the optic canal into dura mater encephali. Eyeball is enveloped by vagina of eyeball (Tenon`s capsule). Adiposal body of orbit localised between vagina of eyeball and periorbita, which formes elastic pillow for eyeball.
Superior and inferior eyelids cover and protect eyeball. Front surface of eyelids is covered by skin. Posterior surface of the eyelids and anterior free surface of eyeball are covered by thin conjuctiva. Last forms superior and inferior sac of conjuctiva.
Tarsal plates, composed of dense regular connective tissue, are important in maintaining the shape of the eyelids. Yeybrows (supercilium) consist of short, sick hair positioned transversally above both eyes along the superior orbital ridges of the scull.
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).Поділитися цим: