Earthworm Cross Section Under the Microscope
Earthworm (Cross Section), Lumbricus terrestris
This is a cross section of an earthworm stained with H&E. It shows the classic body plan of a segmented worm, with a tube (the gut) inside a tube (the body wall) and a fluid-filled cavity between them.
This cross section of an earthworm (Lumbricus terrestris) is stained pink with H&E. The outside is the body wall: a thin cuticle and skin, a thin ring of circular muscle, and then thick bundles of longitudinal muscle that look like rows of feathers. These two muscle layers work against each other, squeezing and shortening the body so the worm can crawl. Inside the wall is the coelom, the body cavity. The gut in the middle is torn and only partly present, so the muscle layers are the clearest part to study.
What to look for
- Cuticle and epidermis: A thin outer covering over a single layer of skin cells.
- Circular muscle: A thin layer of muscle just inside the epidermis.
- Longitudinal muscle: A thicker layer of muscle, pink with H&E, arranged in feather-like bundles.
- Coelom: The open body cavity between the body wall and the intestine.
- Intestine and typhlosole: The central gut, with a fold called the typhlosole dipping in from the top.
- Ventral nerve cord: A small round cord along the bottom of the body cavity.
Questions and answers
What are the parts of an earthworm cross section?
An earthworm cross section shows the cuticle and epidermis, circular and longitudinal muscle layers, the coelom (body cavity), and the intestine with its typhlosole fold. You can also find the dorsal blood vessel above the gut and the ventral blood vessel and nerve cord below it.
What is the typhlosole?
The typhlosole is a fold of the intestine wall that hangs down into the gut. It increases the surface area for absorbing food, similar to how villi work in the human small intestine.
How do earthworms move using two muscle layers?
When circular muscles contract, the worm gets long and thin. When longitudinal muscles contract, it gets short and fat. Alternating these, along with small bristles that grip the soil, lets it crawl.
Compare it
- Category
- Invertebrates
- Scan magnification
- 20x
- Stain
- H&E
Viewing this slide in class
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