Lab 3: Digestive System

Anterior

Toward the head or mouth end.

Posterior

Toward the anus or rear end.

Dorsal

Toward the back.

Ventral

Toward the belly/underside.

Medial

Toward the body midline.

Lateral

Away from the midline.

PERCH — Mouth

Captures prey by drawing in water and food.

PERCH — Pharyngeal jaws

Mechanically manipulate and grind food before swallowing.

PERCH — Esophagus

Transports food from oral region to stomach.

PERCH — Stomach

Major site of chemical digestion.

PERCH — Duodenum

Chemical digestion; receives enzymes from pancreas and liver.

PERCH — Intestine

Main site of nutrient absorption.

PERCH — Anus

Eliminates undigested waste.

PERCH — Pancreas

Supplies digestive enzymes to the duodenum.

PERCH — Liver

Supplies digestive substances and processes absorbed nutrients.

PERCH — Swim bladder

Maintains neutral buoyancy; not part of the alimentary canal.

PERCH — food pathway

Mouth → Pharyngeal jaws → Esophagus → Stomach → Duodenum → Intestine → Anus.

CRAYFISH — Cheliped

Grasps and manipulates food before ingestion.

CRAYFISH — Mouth

Entry point for food.

CRAYFISH — Esophagus

Carries food from mouth to stomach.

CRAYFISH — Stomach

Receives food and digestive enzymes; contains gastric mill.

CRAYFISH — Gastric mill

Mechanically grinds food with hard chitinous teeth.

CRAYFISH — Hepatopancreas

Supplies digestive enzymes and absorbs/stores nutrients.

CRAYFISH — Intestine

Carries processed material toward anus.

CRAYFISH — Anus

Eliminates waste.

CRAYFISH — hepatopancreas pathway clue

Accessory organ; food does not pass through it.

CRAYFISH — food pathway

Cheliped → Mouth → Esophagus → Stomach/Gastric mill → Intestine → Anus.

CLAM — Gills

Collect food from the water.

CLAM — Labial palps

Guide trapped food into the mouth.

CLAM — Mouth

Entry into the alimentary canal.

CLAM — Visceral mass

Contains stomach, digestive gland, intestine, and other organs.

CLAM — Stomach

Site of chemical digestion.

CLAM — Digestive gland

Produces hydrolytic digestive enzymes delivered to stomach.

CLAM — Intestine

Nutrient absorption.

CLAM — Rectum

Carries waste toward anus.

CLAM — Anus

Eliminates waste into outgoing water.

CLAM — mouth vs anus clue

Mouth is surrounded by labial palps; anus is not.

CLAM — food pathway

Gills → Labial palps → Mouth → Stomach → Intestine → Rectum → Anus.