Page 17 - One Million Things: Animal Life - The Incredible Visual Guide

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3 A lobster is an arthropod, with a hard, jointed body, and limbs that are moved by muscles. These are controlled by the brain, which sends signals along a nerve cord. The brain also allows the lobster to see and feel. Food is digested by the digestive system—a tube with openings at each end (the mouth and anus). Blood pumped by the heart through blood vessels and body spaces distributes food and oxygen.

Cerebral
ganglion is the Mouth
lobster’s brain

Stomach crushes and limbs 3 LOBSTER
food into small
particles

Ventral artery carries blood to the body

Heart pumps
blood along
the arteries

Digestive gland ganglion Nerve cord relays signals between the body and cerebral Each arm on this cutaway diagram of a starfish (a type of echinoderm) shows a different layer of the creature’s insides. A skeleton of hard ossicles (small bones) lies just under skin. The digestive system consists of a mouth, stomach, and five sets of digestive pouches, one for each arm. Also projecting into each arm is a branch of the water vascular system, which pumps fluid into tiny tube feet, enabling
releases enzymes
used in digestion
and absorbs food

sperm STARFISH
Testis produces 2
Dorsal artery
carries blood
to intestine

bend the abdomen downward
Muscles that

Intestine carries to anus These simple invertebrates have neither respiratory (breathing) nor circulatory (blood) systems. Instead, oxygen is taken in directly through the flatworm’s surface. Food enters—and undigested food exits— through the mouth, and is distributed to all body parts by the digestive system’s many branches. A simple brain controls movement through nerve cords and picks up signals from the simple eyes.
undigested waste

Hard cuticle of body Anus FLATWORM
(exoskeleton)
covers outside
US_014_015_Systems_flatworm.indd14 14 014_015_Systems_flatworm.indd 14

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