ENT201 - Exam 1 - Blood, Guts and Other Innards

Tracheal System

Network of air tubes supplying oxygen directly to cells

Spiracles

External breathing pores

Filtered

Found on abdominal and rear thoracic segments

Tracheal ring reinforcement

Prevents air tubes from collapsing under negative pressure

Tracheae vs. Tracheoles

• Tracheae: Larger, primary air tubes.

• Tracheoles: Fine, highly branched microscopic extensions that directly contact body cells.

Respiration in Aquatic Adaptations (Mayfly, Mosquito, Diving Beetle)

• Mayflies: External gills for cold, oxygen-rich water.

• Mosquitoes: Surface snorkel tube.

• Diving Beetles: Traps air bubbles under their abdomen before diving.

Foregut

Exoskeleton-lined digestive region

Responsible for intake, suction, storage, and grinding

Midgut

Primary site for enzyme digestion and nutrient absorption; lacks chitinous lining

Hindgut

Exoskeleton-lined near region responsible for water absorption and waste excretion

Malpighian tubules

Excretory organs that filter nitrogenous wastes and regulate osmotic balance

Three Nitrogenous Waste Forms (Most Toxic to Least Toxic)

• Ammonia (3H:1N — highest toxicity)

• Urea (2H:1N — moderate toxicity)

• Uric Acid (1H:1N — lowest toxicity)

Major Advantage of Excreting Uric Acid

It is low in toxicity and precipitates out as a solid, conserving water for the insect.

Open vs. Closed Circulatory Systems

Insects have an open system where hemolymph bathes organs directly; humans have a closed system where blood stays in vessels.

Does insect hemolymph carry oxygen?

No. Respiration is handled entirely by the tracheal system.

Hemocoel

The primary blood cavity surrounding all internal organs, filled with hemolymph.

Dorsal Vessel — Components

Consists of the posterior heart (in the abdomen) and the anterior aorta.

Primary Functions of Hemolymph

Transporting nutrients, waste, and hormones; providing internal defense (hemocytes); and acting as a hydraulic lubricant.

Fat Body — Function & Location

Irregularly shaped tissue (mainly in the abdomen) that stores fats, carbs, and proteins, and converts them into vital body chemicals.