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AGR 254 ENTOMOLOGY

EXOCRINE GLANDS

AND

ENDOCRINE GLANDS

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DTypes of glands

1. Exocrine glands system

2. Endocrine glands system

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Exocrine Glands

Send chemicals/signals outside body-cuticle layer.

They may be single cells or small aggregates of secretory cells; or can be complex glands

Exocrine glands are generally of ectodermal origin and are widely scattered over the insect.

Examples of exocrine glands:A. Simple unicellular gland

B. Unicellular cell with ductule cell

C. Simple aggregations of gland cells

D. Aggregation of gland cells with common duct

E. Complex aggregation of glands with common duct

Glands that secrete their products into ducts that lead directly into the external or lumens of various organs.

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Examples of Exocrine Glands

Simple unicellular

Unicellular with ductule

Simple aggregation

Aggregation –same duct Complex-

same duct

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DFunction of exocrine

1. Defense

venoms, alarm pheremones Nastute soldiers of termite produce

sticky defensive material – from the enlarged frontal gland

2. Intraspecific Communication

Glands in many insects produce chemicals that serve as signals of various sorts for other members of the same species

These are called “pheromones”

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DFunction of exocrine

3. Building Structural Material Structural materials include wax and silk

In honeybee wax is secreted by epidermal glands – to construct honey combs

4. Transport of Materials in Liquid State Salivary glands

Accessory gland and spermathecal gland – assist transport of spermatozoa

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DEndocrine Gland Typically ductless and their secretions

are usually released directly into the Hemolymph(like blood of human).

Endocrine system – involved with the secretion of “ hormones” .

Commonly function in close coordination with one another.

In insects, the largest and most obvious endocrine glands are found in the Prothorax-just behind the head.

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DEndocrine Gland & The Nervous system-(coordinate)

Hormones are involved with long term adjustments to changes in the external and/or internal environment

Nerves system only provide short-term adjustments to changes in the external and/or internal environment

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DMajor endocrine structures are:

Corpora allata

Corpora cardiaca

Thoracic glands

Insects have special cells called Neurosecretory cells that secrete neurohormones.

act as the link between the nervous and endocrine systems

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DNeurosecretory cells location:

Protocerebrum

Subesophageal and other ventral chain ganglia

Corpus cardiacum

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Corpora allata produces and secretes juvenile hormones-it plays a crucial role in metamorphosis.

The thoracic gland or Prothoracic gland– secrete hormones that initiate the “molting process”- Ecdysal Hormone.

Prothoracic glands are only found in immature insects.

In many Diptera species, the corpus allatum is fused with the corpus cardiacum, forming a "ring gland", also known as Weismann's ring.-wiki

In Lepidoptera species, the corpus allatum acts a release site for prothoracicotropic hormone which is generated by the brain.-wiki

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Corpora allata

Thoracic gland

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DFunction Of the endocrine glands:

Regulation of molting

Determination of form at metamorphosis

Polymorphism

Regulation of diapause

Involvement in reproduction

Regulation of metabolic activities and general body functions

Regulation of behavior

Regulation of preprogrammed cell death

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THE END...THANKS

FOR YOUR ATTENTION