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Anatomy · Additional topics

Anatomy of the retina

tunica interna bulbi / retina

The retina is the internal sensory tunic of the eyeball, responsible for light perception. It contains specialized neurosensory cells that are the first to capture the light signal and transform it into a nerve impulse.

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Layers of the retinaConsists of 10 layers, from the retinal pigment epithelium to the inner limiting membrane.
Blind spotThe optic disc is completely devoid of photoreceptors.
Yellow spotThe macula lutea with the central fovea is the zone of highest visual acuity.
Type of receptionPrimary sensory organ: neurons perceive the stimulus directly.
4 min readFor medical studentsUpdated 10.10.2026
Material prepared by WhiteCoat Pro editorial team based on platform study guidesPending instructor review

Tunics of the eyeball as a framework for the retina

The retina is the internal tunic of the eye, but to understand its topography, it is essential to know the surrounding structures. The eyeball is formed by three tunics.

The outer fibrous tunic (tunica fibrosa bulbi) provides protection and shape. It consists of the opaque sclera (sclera), which thins at the exit site of the optic nerve to form the lamina cribrosa (lamina cribrosa sclerae). The anterior part of the fibrous tunic is the transparent cornea (cornea). It lacks blood vessels but is rich in nerve endings, consisting of the proper substance (substantia propria corneae), limiting laminae, and epithelium. The junction where the sclera transitions into the cornea is called the limbus (limbus corneae).

The middle vascular tunic (tunica vasculosa bulbi) is responsible for trophic support and light regulation. It includes the choroid proper (choroidea) with a dense capillary network, the ciliary body (corpus ciliare), and the iris (iris). The ciliary body comprises the ciliary ring (orbiculus ciliaris) and the ciliary crown (corona ciliaris) with processes; it is connected to the lens by the suspensory ligament (fibrae zonulares). The iris features the pupil (pupilla) and muscles that constrict (m. sphincter pupillae) and dilate (m. dilatator pupillae) it. The stroma of the iris (stroma iridis) contains blood vessels and connective tissue.

The internal sensitive tunic — the retina (tunica interna, retina) — lies tightly against the inner surface of the vascular tunic.

Regions and topographic zones of the retina

The internal tunic of the eye is functionally and anatomically heterogeneous. Two distinct parts are clearly identified:

  • Optic part (pars optica retinae) — lines the posterior segment of the eye and contains specialized photoreceptors (rods and cones).
  • Blind part — covers the inner surface of the ciliary body (pars ciliaris retinae) and the iris (pars iridica retinae). Light-sensitive elements are completely absent in these zones.

Special functional zones are located on the fundus (within the optic part):

  • Macula (macula lutea) — the area of best, sharpest vision. In the very center of the macula is a small depression called the central fovea (fovea centralis).
  • Optic disc (discus nervi optici) — the area where nerve fibers converge and leave the eyeball. Since there are neither rods nor cones here, this zone forms the physiological blind spot in the visual field.
Test your knowledge on this topicExercises from the Anatomy course question bank with instant answers and explanations.

Receptor apparatus and the pathway of a light ray

The receptor apparatus of the eye belongs to primary sensory organs. The reception mechanism here is carried out directly by neurosensory cells. The dendrites of these cells perceive light stimulation independently and generate a nerve impulse without requiring additional intermediary cells for the primary capture of the signal.

A crucial anatomical feature of the retina is its "inverted" structure. The layer of rods and cones, which forms the photosensory apparatus, lies deepest of all layers, directly bordering the outer retinal pigment epithelium. Due to this arrangement, for light to reach the photoreceptors, it must pass straight through all the inner layers of the retina. After a light quantum is captured by the receptor, the generated nerve impulse travels in the opposite direction — from the deep layers to the superficial ones, where ganglion cells are located, whose axons form the optic nerve.

10 layers of the retina

The optic part of the retina has a complex multilayered structure, including photoreceptor, nuclear, and neurofibrillar (plexiform) layers. Complete stratification includes 10 layers. Listed in order from the vascular tunic (outer) to the vitreous body (inner), they are arranged as follows:

  1. Layer of pigment epithelium — the outermost layer.
  2. Layer of rods and cones (photosensory layer) — often subdivided into the outer and inner segments of the photoreceptors.
  3. Outer limiting membrane.
  4. Outer nuclear layer — formed by the nuclei of photoreceptor cells.
  5. Outer plexiform layer — the zone of synapses between photoreceptors and subsequent neurons.
  6. Inner nuclear layer — contains the nuclei of bipolar, horizontal, and amacrine cells.
  7. Inner plexiform layer — the second zone of synaptic contacts.
  8. Ganglion cell layer — formed by the bodies of large ganglion cells.
  9. Nerve fiber layer — consists of the axons of ganglion cells heading toward the optic disc.
  10. Inner limiting membrane — borders the vitreous body.
How to memorize

To remember the order of the nuclear and plexiform layers, use the alternation rule: first come the photoreceptor nuclei (outer nuclear), then their synapses (outer plexiform), then the nuclei of intermediate neurons (inner nuclear), and again the synapses (inner plexiform).

Class and exam questions

Why is the optic disc called the blind spot?

In the region of the discus nervi optici, nerve fibers exit the eyeball. Photoreceptors are completely absent in this zone, so it is physiologically incapable of perceiving light.

In what direction does light pass through the retina?

Light passes straight through all the inner layers of the retina because the photoreceptors are located in the deepest layer adjacent to the pigment epithelium. The nerve impulse then travels in the opposite direction.

Which parts of the retina do not contain photoreceptors?

There are no light-sensitive elements in the ciliary (pars ciliaris retinae) and iridial (pars iridica retinae) parts of the retina, nor in the region of the optic disc.

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What else to study on this topic

  • Structure of the outer and inner segments of photoreceptor cells.
  • Distribution of rods and cones in various zones of the retina.
  • Visual pigments and the biochemistry of light perception.
  • The role of vitamin A in the normal functioning of the receptor apparatus.
  • Detailed anatomy of the fibrous and vascular tunics of the eyeball.

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