Lab: Earthworm

Anatomy of the Patella

  • The patella, also known as the kneecap, resembles a Band Aid in appearance.

  • Its defining characteristic is its bright pink color that distinguishes it from surrounding structures.

Myth Debunking

  • A common myth regarding the patella is that it can be cut in half to create two separate patellae. This is false.

Anatomy of the Earthworm

General Structure

  • Earthworms have a segmented body, with a distinct head and tail end.

    • The head houses the prostomium.

    • The end of the tail is referred to as the anus.

Key Segments

  • The first segment is the prostomium:

    • Defined as the segment that is located before the mouth.

    • The term 'pro' indicates its position as 'before'.

  • The second segment is the peristomium:

    • Envelops the mouth region.

    • The prefix 'peri' suggests 'around'.

Structure Terminology

  • The skin of the earthworm is known as the cuticle.

  • The term for segments of the body is somite.

  • Each segment contains a structure known as the nephridium (plural: nephridia), which functions as a kidney.

Earthworm Cross Section

  • C Lobe: Refers to the body cavity, which can be seen as an empty space within the cross-section.

  • Intestine: The tube running through the cross-section, responsible for digestion and absorption of nutrients.

    • Important functions include:

    • Digestion: The breakdown of food substances.

    • Absorption: The uptake of nutrients into the body.

  • Tinthosole:

    • A structure that protrudes down into the intestine to increase the surface area for enhanced absorption.

    • Comprised of chlorogogue cells which function to release digestive enzymes.

Circulatory System

  • Blood vessels present in the earthworm:

    • Dorsal Blood Vessel: Located along the back of the earthworm, perceived as "fat" due to the blood it carries.

    • Ventral Blood Vessel: Found along the belly, or front of the worm.

Nerve and Muscle Structure

  • Ventral Nerve Cord: Located along the belly, this structure differentiates protostomes (like worms) from deuterostomes (like humans), where the nerve cord is found on the back.

  • Muscle Fibers:

    • There are two main types of muscle fibers in the earthworm:

    • Circular Muscle Fibers: Encircle the body; they contract inwards to facilitate movement by squeezing water into different parts of the worm.

    • Longitudinal Muscle Fibers: Extend lengthwise along the body; they contract to pull the body into a more elongated shape for crawling.

Educational Materials and Resources

  • Students are encouraged to review terminology and structures discussed during the class.

  • Instructions were given regarding slides and materials being uploaded to Canvas for better access.

  • Discussions about educational policies and regulations regarding shared educational materials among students and faculty.