Description
An “Earthworm: Blood Circulation, Respiratory & Nervous System” (55×90 cm) educational chart provides clearly labeled diagrams showing the closed circulatory system, skin-based respiration, and segmentally organized nervous system, supporting zoology and biology lessons.
Circulatory (Blood) System
Closed Circulatory System: Blood circulates only within vessels—a dorsal blood vessel runs above the digestive tract, and a ventral vessel below, connected by five pairs of aortic arches (pseudohearts) in segments 7–13.
Directionality: Dorsal vessel collects blood and pumps it forward; aortic arches pump blood to the ventral vessel, distributing it through lateral vessels and capillaries to tissues.
Blood Composition: Blood contains plasma and colorless corpuscles, with hemoglobin dissolved in plasma (not in cells) giving it a red color.
Respiratory System
Skin Respiration: Earthworms lack lungs or gills—gas exchange occurs by diffusion across their moist skin.
Moist Cuticle: The skin must remain moist to enable effective exchange of oxygen and carbon dioxide between blood capillaries and the environment.
Nervous System
Central Nervous System: Comprised of a dorsal brain (cerebral ganglia) in the third segment, subpharyngeal ganglia below the pharynx, and a ventral nerve cord with paired ganglia in each segment.
Peripheral & Sympathetic Nerves: Lateral nerves arise from the main cord, supplying the body wall and organs for movement and response.
Sensory Ability: Despite lacking eyes, earthworms possess receptor cells in the skin and anterior end sensitive to light, touch, vibration, and chemicals.
This chart is ideal for illustrating the functional anatomy and physiology of earthworms, reinforcing comparative biology lessons between vertebrate and invertebrate organ systems.