Oral disc (buccal funnel)The round sucker under the head. A lamprey holds on to a stone or a fish with it. Soft papillae fringe its edge.
EyeOne on each side of its head. It has no eyelids.
Gill openingsSeven small openings in a row behind each eye. Each one leads to a gill pouch.
NostrilA single opening on top of the head. It leads to the olfactory sac. Most animals with backbones have two nostrils.
Pineal eyeA pale window of skin behind the nostril. Under it lies the pineal eye, an organ that senses light.
First dorsal finThe front fin on the back. Thin rods of cartilage hold it up.
Second dorsal finThe rear fin on the back. It runs on toward the tail fin.
Caudal fin (tail fin)The fin around the tip of the tail. A lamprey has no paired fins at all.
Muscle blocks (myotomes)Bands of muscle that show through the skin. They lie one behind another along the whole body.
Cut along its length 12
Horny teethPointed teeth made of horn. They line the funnel in rows and help the lamprey hold on.
TongueA toothed tongue that works like a piston. Large muscles behind it move it to rasp at food.
Gill pouchesSeven sacs on each side, lined with gills. Each opens to the outside and into the respiratory tube.
Respiratory tubeThe wide lower tube, closed at its rear end. Water passes between it and the gill pouches.
EsophagusThe narrow upper tube, for food. It passes over the heart and joins the intestine.
NotochordA stiff rod along the body. It is the main support, kept for life: there is no bony backbone.
Spinal cordThe nerve cord, lying just above the notochord. It runs back from the brain.
BrainThe lobed front end of the nerve cord. It sits above the front tip of the notochord.
Olfactory sacThe organ of smell. A short canal leads down to it from the nostril.
HeartIt lies in its own chamber behind the gill pouches. It has one atrium and one ventricle.
LiverA large organ of one lobe. The adult has no gallbladder and no bile duct.
IntestineA straight tube that runs back to the anus. There is no separate stomach.
How this list was compiled: Every name checked on 2026-10-01 and again on 2026-10-02 in two sources. L. H. Hyman, A Laboratory Manual for Comparative Vertebrate Anatomy (1922, public domain), the lamprey: its outside and the cut through the front of the body, https://archive.org/details/ost-biology-labmanualcompvert00hymarich. R. W. Hegner, College Zoology (1912, public domain), the sea lamprey, https://archive.org/details/collegezoology00hegn. T. J. Parker and W. A. Haswell, A Text-book of Zoology, volume 2 (1910, public domain), the lamprey, https://archive.org/details/textbookofzoolog02parkrich. J. Arthur Thomson, Outlines of Zoology (1892, public domain), the lamprey, https://archive.org/details/cu31924012160762. Wikipedia, Lamprey and Sea lamprey, https://en.wikipedia.org/wiki/Lamprey. U.S. Geological Survey, Nonindigenous Aquatic Species, sea lamprey fact sheet, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=836. Licence: own work
The drawing: Drawn for this site on 2026-10-01 from plain geometry, the tongue redrawn on 2026-10-02; nothing traced. Licence: own work
How it works
This lamprey anatomy quiz is drawn on an adult sea lamprey, a fish with no jaws. One view shows the outside; the other shows the front of the body cut along its length. It is a plan, not to scale.
Read the full guide
Outside
Start with the whole animal: the eye, the row of gill openings behind it, two dorsal fins and the caudal fin. The bent lines on its side are muscle blocks. Below, the head is drawn larger. From underneath you see the oral disc and its rings of horny teeth; from above, the single nostril with the pineal eye just behind it.
Cut lengthwise
The second view is cut lengthwise. Food goes up the narrow esophagus; the wide respiratory tube below it leads to the gill pouches. As a lamprey heart diagram it is simple: one atrium and one ventricle, in a chamber of their own behind the last pouch. Show me the labels first writes every name on the drawing.
A lamprey has no paired fins. Its only fins are the two on the back and the one around the tail.
Questions and answers
Do lampreys have jaws?
No. A lamprey is a jawless fish. Its mouth is a round sucking disc lined with horny teeth, with a toothed tongue in the middle.
How many gill openings does a lamprey have?
Seven on each side of the head, in a row behind the eye. Each opening leads to its own gill pouch.
Do lampreys have bones?
No. The skeleton is made of cartilage, and the main support of the body is the notochord, a stiff rod that the lamprey keeps for life.
How many chambers does a lamprey's heart have?
Two main chambers, an atrium and a ventricle. Blood reaches the atrium through a sinus venosus, and the heart lies in a chamber of its own behind the gill pouches.
Is a lamprey an eel?
No. A lamprey looks like an eel, but the two are not related. A lamprey has no jaws, no paired fins and no bones.