Insects and People: Internal Anatomy of Insects

Respiration - Tracheal System

Tracheal System: a complex network of silvery air tubes that lead from the spiracles on the body surface to practically all cells of the body. This is how ==oxygen gets to the tissues== (NOT BY THE HEMOLYMPH) of the circulatory system.

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A sort of breathing is possible by expanding and compressing the body while alternately ==opening and closing different spiracles==. Still, oxygen must diffuse through the smaller tracheae to reach the cells.

VOCAB:
  • Spiracles: an external respiratory opening, each of a number of pores on the body of an insect
  • Hemolymph: an insect’s blood
  • Circulatory system: the system that circulates blood through the body

Aquatic Adaptations

Aquatic insects obtain oxygen in three major ways:

  1. Air tubes: these extend spiracles to water surface, like a snorkel
  2. Bubbles: these are taken from the water’s surface, carried over surface of body where spiracles are located
  3. Gills: these are structures which obtain dissolved oxygen from the water itself and supply it to the tracheal system

Digestion - Three Guts

 

This generalized gut contains most of the digestive structures found in most insects. Insects with various foods have widely differing digestive systems.

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The insect gut is made of three guts:

  1. Foregut: where food is temporarily stored and grinded down before digestion
  2. Midgut: where most of digestion and absorption takes place to absorb nutrients from the food
  3. Hindgut: where waste is prepared for excretion and water is preserved

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The Malpighian tubes are located between the midgut and the hindgut, and they pick up nitrogenous waste from the insect’s blood. Meanwhile, mammals produce nitrogenous waste as urine. Since ==insects want to conserve water,== they excrete uric acid.

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Excretion - Spaghetti

Malpighian Tubules: blind tubes that open into the junction of midgut and hindgut. They sway around in the hemolymph. ==Nitrogenous waste== (from protein metabolism) is removed from the hemolymph and passed out with feces.

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==Most common wastes:==

  1. uric acid: in terrestrial insects and birds (requires little water)
  2. Ammonia: in aquatic insects (toxic, so requires more water to flush out)

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Circulation - Slosh System

 

Hemolymph: insect blood; it contains plasma and blood cells (==hemocytes==)

  • Primary functions:
      * Acts as a lubricant and hydraulic
      * ==Transport== - chemical food, waste, hormones
      * ==Internal defense== - against pathogens

Hemocoel: the blood cavity that surrounds all organs and bathes them in hemolymph.

  • Thus insects, have an ==“open” circulatory system.==

Dorsal Vessel: consists of two parts:

  1. heart: takes in hemolymph in the abdomen, pumps it forward (anteriorly)
  2. aorta: conducts hemolymph through the thorax to head

Diaphragms: channel the flow of hemolymph so that it is distributed throughout the body

Accessory Hearts: ==pump hemolymph into wings==, legs, and other remote structures

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Storage - Fat Body

Fat Body: stores most chemical food, like fats, carbohydrates, and proteins.

  • It also serves to transform these chemicals into various products needed by the body (i.e. intermediary metabolism)

It is an irregularly shaped tissue found throughout the body, particularly in the abdomen.

 

A well-nourished insect often has so much fat body that other organs of the abdomen are obscured.

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