Eye (histology)


 * a complex, highly specialized organ. It enables accurate analysis of object form, light intensity and colors.
 * stored in orbit
 * composed of:
 * The eyeball (bulbus oculi), in which we also find the so-called refractive structures of the eye
 * Accessory structures of the eye (organa oculi accessoria)

The eyeball (bulbus oculi)


It consists of 3 layers:


 * tunica fibrosa, which consists of:
 * cornea
 * sclera
 * tunica vasculosa, consisting of 3 other parts:
 * choroid
 * ciliary body
 * iris
 * tunica nervosa, formed by the retina, which consists of 2 parts:
 * pars caeca retinae
 * pars optica retinae

Tunica fibrosa

 * Sclera
 * white
 * formed by dense collagen tissue
 * represents 5/6 of the tunica fibrosa


 * Cornea
 * thicker than the sclera
 * colorless
 * transparent
 * avascular
 * composed of 5 layers:
 * Anterior corneal epithelium - multi-layered squamous non-keratinizing (5-6 cell layers)
 * Bowmann's membrane – formed by collagen fibers; is acellular
 * Substantia propria corneae – 50 to 60 layers of bundles of parallel collagen fibrils that cross at approximately right angles
 * Descemet's membrane - has the character of a basal lamina
 * Posterior corneal epithelium – single-layer flat
 * corneal epithelia are able to transport ions across the cell membrane
 * the regular arrangement of collagen fibrils ensures the transparency of the cornea

Tunica vasculosa

 * highly vascularized layer
 * there is also a sparse collagen fiber rich in fibroblasts and melanocytes


 * Choroid (choroidea)
 * has 4 layers:
 * Lamina suprachoroidea – a layer of thin collagenous tissue
 * Zona vasculosa
 * Lamina choriocapillaris – anastomosing network of capillaries
 * Lamina vitrea (Bruch's membrane)


 * Corpus ciliare
 * Orbiculus ciliaris – muscle ciliaris
 * Corona ciliaris – sparse collagen tissue


 * Iris
 * consists of 4 layers:
 * Anterior iris epithelium
 * Front boundary layer
 * Stroma iridis
 * Pars iridica retinae

Tunica nervosa

 * Pars ceaca retinae
 * pars ciliaris retinae
 * pars iridica retinae


 * Pars optica retinae
 * has 10 layers (ordered from outermost to innermost)
 * pigment epithelium
 * a layer of rods and cones
 * membrana limitans externa
 * outer core layer
 * outer layer plexiform
 * inner core layer
 * inner layer plexiform
 * ganglion cell layer
 * layer of nerve fibers
 * membrana limitans interna

Refractive structures of the eye

 * consists of:
 * lens (lens crystallina)
 * humor aquaeus
 * corpus vitreum (vitreous) – transparent gel, 99% water, it contains hyalocytes.

Lens (lens crystallina)

 * transparent
 * biconvex
 * consists of 3 parts:
 * capsula lentis – covers the entire lens, contains type IV collagen
 * anterior epithelium of the lens – located only on the anterior surface
 * lens fibers – hexagonal prism shape

Accessory structures of the eye

 * conjunctiva
 * eyelids (palpebrae)
 * lacrimal apparatus
 * oculomotor muscles

Conjunctiva

 * thin, transparent
 * lines the conjunctival sac
 * lined with multilayered cylindrical epithelium

Eyelids (palpebrae)

 * moving bodies
 * they are covered by skin on the outside, conjunctiva on the inside
 * the eyelashes depart from the free edge
 * the basic supporting structure is the tarsus, which is made up of dense collagenous tissue
 * striated muscle is found here
 * contains 3 types of glands:
 * Meibomian
 * long, branched, alveolar, sebaceous
 * opens into the conjunctival sac
 * Zeiss
 * small, branched, alveolar, sebaceous
 * opens into the eyelash follicle
 * Moll's
 * modified, simple, tubular, coiled, apocrine
 * opens into the eyelash follicle

Lacrimal apparatus

 * consists of the lacrimal gland and the duct system
 * the function of the lacrimal gland is to moisten the surface of the eye


 * 1) glandula lacrimalis – compound tuboalveolar gland, its serous compartment consists of cylindrical cells of the serous type, and its ducts merge into
 * 2) ductuli lacrimales, which are lined with a single-layer cubic epithelium and open into
 * 3) conjunctival sac, from which tears are drained using
 * 4) lacrimal canals (canaliculi lacrimales), they are lined with multi-layered squamous epithelium and merge into one canal and open into
 * 5) saccus lacrimalis, which continues as
 * 6) ductus nasolacrimalis and opens into the meatus nasi inferior


 * saccus lacrimalis and ductus nasolacrimalis are lined with multi-rowed cylindrical epithelium, which is found in the greater part of the lining of the respiratory system

Related articles

 * Eye (biophysics)
 * Eye (biophysics)/Principle of vision
 * Eye (biophysics)/Disorders of the eye
 * Oculomotor muscles