Inside of an earthworm

Transcript

Pharynx

Earthworms push the pharynx out of their mouths to grasp hold of organic matter. They pull the food back into their mouths and then wet it with saliva.

Acknowledgement: Sara L Roggemann, Three Flowers Photography

Gizzard

Earthworms do not have teeth, so they use the strong muscles of the gizzard (and grains of sand and soil) to grind up their food.

Acknowledgement: Sara L Roggemann, Three Flowers Photography

Intestine

Once the food is ground up, it moves into the intestine where digestive fluids continue to break down the food so it can be absorbed.

Acknowledgement: Sara L Roggemann, Three Flowers Photography

Aortic arches

Most earthworm species have five aortic arches or ‘hearts’ that move blood around the body. The number of aortic arches varies amongst species.

Acknowledgement: Sara L Roggemann, Three Flowers Photography

Dorsal and ventral blood vessels

The dorsal blood vessel runs along the length of the upper side of the earthworm. It contracts and pumps blood to the aortic arches. The ventral blood vessel runs along the lower length of the earthworm.

Acknowledgement: Sara L Roggemann, Three Flowers Photography

Cerebral ganglion

The earthworm’s ‘brain’. Earthworms have a simple nervous system. The cerebral ganglion is connected to a ventral nerve cord that runs the length of the body. Each segment is connected to this cord, allowing earthworms to move and respond to light, touch, chemicals, vibrations and more.

Acknowledgement: Sara L Roggemann, Three Flowers Photography

Circular muscles

Circular muscles surround each segment. When earthworms squeeze these muscles, they become long and thin. Circular muscles alternate with longitudinal muscles to help earthworms move.

Longitudinal muscles

Longitudinal muscles run the length of the earthworm. When these muscles contract, earthworms become short and fat. Longitudinal muscles alternate with circular muscles to help earthworms move.