• 14 parts
  • Checked September 2026

Mussel Anatomy Quiz

Tap each part of a sea mussel as it is named, first on the closed shell and then inside it.

Mussel Anatomy Quiz

Name Date

Tap the byssal threads

1 of 5

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. Valve
  2. Umbo
  3. Growth lines
  4. Hinge ligament
  5. Byssal threads
  6. Mantle
  7. Visceral mass
  8. Posterior adductor muscle
  9. Anterior adductor muscle
  10. Gills
  11. Foot
  12. Labial palps
  13. Incurrent siphon
  14. Excurrent siphon

Drawn for this site on 2026-09-30 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 Read every name on the labeled mussel drawing

All 14 parts on the diagram

Show the list

The shell, outside 5

  1. Valve One of the two hinged halves of the shell. The shell supports the soft body and protects it from predators and from drying out.
  2. Umbo The oldest part of the valve, at its pointed front tip. The shell has grown outward from here.
  3. Growth lines Ridges that follow the edge of the shell. They mark the pauses between one period of growth and the next.
  4. Hinge ligament A springy band that joins the two valves along the top edge. When the muscles relax, it opens the valves again.
  5. Byssal threads Tough, stretchy threads that fix the mussel to a rock. The foot lays them down as a liquid that hardens in sea water. Cooks call them the beard.

Inside the shell 9

  1. Mantle Two flaps of the body wall, one lining each valve. The mantle makes the shell.
  2. Visceral mass The soft body in the middle. It holds the stomach, the digestive gland and the other main organs.
  3. Posterior adductor muscle The large muscle at the rear that pulls the two valves shut. In a sea mussel it does most of the work.
  4. Anterior adductor muscle The small muscle at the front. It also pulls the valves together, but in a sea mussel it is much reduced.
  5. Gills Long sheets on each side of the body. They take oxygen from the water, and their cilia move the water along and catch the food in it.
  6. Foot Small and tongue-shaped in a sea mussel. A groove along it leads from the pit where the byssal threads are made.
  7. Labial palps Small flaps beside the mouth. They pass the food caught by the gills into the mouth.
  8. Incurrent siphon The opening where water is drawn in. The water brings oxygen and food.
  9. Excurrent siphon The smaller opening where the used water and the wastes leave.

How this list was compiled: Every name checked on 2026-09-30 in two sources. Wikipedia, Mussel, Byssus, Bivalve shell and Bivalvia: the valves, ligament, adductor muscles, mantle, foot, byssal threads, gills, labial palps and siphons, https://en.wikipedia.org/wiki/Mussel. R. W. Hegner, College Zoology (1912, public domain), the fresh-water mussel: umbo, lines of growth, hinge, mantle, gills, foot, visceral mass, palps and siphons, https://archive.org/details/collegezoology00hegn. T. J. Parker and W. A. Haswell, A Text-book of Zoology, volume 1 (1910, public domain), for the sea-mussel's byssus and its unequal adductor muscles, https://archive.org/details/textbookofzoolog00park. Also H. S. Pratt, A Course in Invertebrate Zoology (1902), and Animal Diversity Web, Bivalvia, https://animaldiversity.org/accounts/Bivalvia/. Licence: own work

The drawing: Drawn for this site on 2026-09-30 from plain geometry; nothing traced. Licence: own work

How it works

This mussel anatomy quiz names one part at a time and you tap it on a sea mussel: five parts on the closed shell, then nine on the body with the near valve taken off.

Read the full guide

On the shell

The valve comes first: it is the whole half-shell facing you, and its ring sits on the shell itself. The growth lines are the curved ridges, counted in the wide part of the shell where their line ends. The umbo is the tip itself, and the hinge ligament the narrow band on the top edge behind it.

Inside: front, rear, top, bottom

Anterior means toward the pointed front end and posterior toward the rear, where the siphons open: that tells the small anterior adductor from the large posterior one. The hinge side is dorsal and the opening edge ventral, so an older textbook's ventral siphon is the incurrent one, and its dorsal siphon the excurrent.

  • The mouth is not asked. It lies between the labial palps, the small flaps at the front end of the gills.
  • The valve drawn facing you is the left one: hinge uppermost and front end to the left, by the rule for any bivalve.

Questions and answers

What is on the mussel anatomy quiz?

Fourteen parts in two rounds: the shell from outside, then the body lying in one valve. The stomach, digestive gland, heart and kidney are not asked, because none of them shows in this view.

Is a mussel a bivalve?

Yes. Bivalves are the class of mollusks whose shell is a hinged pair of half-shells called valves, and mussels belong to it. That is why the first thing this quiz asks for is a valve.

Do mussels have a head or a brain?

Neither. Bivalves as a group have no head, and they have no brain: the nervous system is a nerve network with a series of paired ganglia.

What is the mantle cavity of a mussel?

The space between the two flaps of the mantle. The gills, the foot and the visceral mass lie in it. The cavity itself is not asked; the mantle that walls it is.

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