• 14 parts
  • Checked October 2026

Rod and Cone Cells Diagram

One rod and one cone, side by side, with the same parts on both.

Rod and Cone Cells Diagram

Name Date

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1 2 3 4 5 6 7 8 9 10 11 12 13 14
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Write the name of each numbered part.Answer key

  1. Rod
  2. Cone
  3. Rod outer segment
  4. Cone outer segment
  5. Membrane discs
  6. Connecting cilium
  7. Inner segment
  8. Mitochondria
  9. Nucleus
  10. Axon
  11. Synaptic terminal
  12. Pigment epithelium
  13. Bipolar cell
  14. Direction of light

Drawn for this site on 2026-10-01 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the whole eye, with these cells in its retina

All 14 parts on the diagram

Show the list

The two cells 2

  1. Rod A photoreceptor that works in dim light. It is slim, with a long rod-shaped outer segment.
  2. Cone A photoreceptor for daylight and color. It is stouter, with a short tapered outer segment.

The outer end 4

  1. Rod outer segment The long, straight tip of the rod. It holds the stack of discs that catch light.
  2. Cone outer segment The short, tapered tip of the cone. Its light-catching membrane is folded like a stack of discs.
  3. Membrane discs Flat membrane sacs stacked in the outer segment. Their membrane holds the pigment that absorbs light.
  4. Connecting cilium A thin stalk that joins the inner segment to the outer segment.

The inner end 5

  1. Inner segment The thick part below the cilium. It is full of mitochondria and builds the pigment for the outer segment.
  2. Mitochondria Long, thin bodies that fill the inner segment. They supply the cell with energy.
  3. Nucleus The nucleus lies in the cell body, below the inner segment.
  4. Axon A short fiber from the cell body to the synaptic terminal.
  5. Synaptic terminal The end of the cell. It passes the signal on to bipolar and horizontal cells.

Around them 3

  1. Pigment epithelium A layer of pigmented cells at the tips of both cells.
  2. Bipolar cell The next cell in line. It takes the signal from the rod and the cone toward the ganglion cells.
  3. Direction of light Light comes from the side of the synaptic terminals. It crosses the cell before the outer segment catches it.

How this list was compiled: Every name checked on 2026-10-01 in at least two of these. (1) Webvision, University of Utah, Photoreceptors, https://webvision.med.utah.edu/book/part-ii-anatomy-and-physiology-of-the-retina/photoreceptors/. (2) Wikipedia, English edition, Photoreceptor cell, Rod cell and Cone cell, https://en.wikipedia.org/wiki/Photoreceptor_cell. (3) Neuroscience Online, McGovern Medical School at UTHealth Houston, Section 2, Chapter 14, https://nba.uth.tmc.edu/neuroscience/m/s2/chapter14.html. Detail lines are in our own words. Licence: own work

The drawing: Drawn for this site on 2026-10-01 from plain geometry; nothing traced. Licence: own work

How it works

A rod and a cone stand side by side, as they do in the retina. The right half is a cone cell diagram and the left a rod: one photoreceptor cells diagram with the same parts on both.

Read the full guide

The two cells, then down each one

Numbers 1 and 2 are the cells: the rod at the left, the cone at the right. Numbers 3 and 4 are their outer segments, long and straight on the rod, short and tapered on the cone. The rod is cut open to show its discs, 5. Then down either cell: the connecting cilium, 6; the inner segment, 7, with its mitochondria, 8; the nucleus, 9; the axon, 10; and the synaptic terminal, 11. Around them: the pigment epithelium, 12; a bipolar cell, 13; and the light, 14, coming from below.

  • Tell the two apart by the outer segment: a rod has a long tube and a cone a short taper.
  • The cells point away from the light, so it passes the synaptic terminal first and reaches the outer segment last.

Questions and answers

What is the difference between a rod and a cone cell?

Rods work in dim light and have a long, rod-shaped outer segment. Cones work in daylight, give color vision and have a short, tapered outer segment. Both have an inner segment, a nucleus, an axon and a synaptic terminal.

What are the parts of a photoreceptor cell?

From the tip: the outer segment with its discs, a thin connecting cilium, the inner segment full of mitochondria, the cell body with the nucleus, the axon and the synaptic terminal.

What do the discs in the outer segment do?

They are flat membrane sacs stacked along the outer segment. Their membrane holds the visual pigment that absorbs light. New discs are made at the cilium, and the oldest are taken up by the pigment epithelium.

Why do rods and cones point away from the light?

The retina is built that way: the photoreceptors lie at the back, with their tips against the pigment epithelium. Light crosses the other layers of the retina before it reaches them.

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