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Questions and Answers
Which type of nephridium in earthworms is devoid of nephrostome?
Which type of nephridium in earthworms is devoid of nephrostome?
What is the primary function of the septal excretory canal in earthworms?
What is the primary function of the septal excretory canal in earthworms?
How many septal nephridia are present in each segment of an earthworm?
How many septal nephridia are present in each segment of an earthworm?
Which type of nephridia in earthworms is responsible for the excretion of waste directly to the outside?
Which type of nephridia in earthworms is responsible for the excretion of waste directly to the outside?
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How many pharyngeal nephridia groups are found in an earthworm?
How many pharyngeal nephridia groups are found in an earthworm?
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What is the name given to the excretory system of earthworms where waste is released into the alimentary canal?
What is the name given to the excretory system of earthworms where waste is released into the alimentary canal?
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Where do the ducts of the pharyngeal nephridia in the 6th segment of an earthworm open?
Where do the ducts of the pharyngeal nephridia in the 6th segment of an earthworm open?
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What is the primary function of the glandular cells in the nephridia of earthworms?
What is the primary function of the glandular cells in the nephridia of earthworms?
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Study Notes
Excretory System in Earthworms
- Earthworms have specialized, coiled tubes called nephridia for excretion.
- Nephridia are found in all segments except the first three.
- There are three types of nephridia: septal, pharyngeal, and integumentary.
Septal Nephridia
- Located on the septa (the walls between segments).
- Each septum typically has 40-50 nephridia.
- Approximately 80-100 septal nephridia are present in each segment.
- It comprises a nephrostome (a wide ciliated funnel), a body, and a terminal duct.
- The nephrostome opens into the coelom.
- The body has two parts: a short, straight lobe and a long, spirally twisted loop with proximal and distal limbs.
- Ciliated canals within the nephridia, which are four in the straight lobe, one in the neck, three in the lower, and two in the upper parts of the twisted loop.
- Terminal ducts from each nephridium connect to a septal excretory canal for further processing.
- The septal excretory canal runs parallel to the commissural vessel.
- The supra-excretory canal in each segment, which is connected to the alimentary canal, receives contents from the excretory canal. Excretory products enter the alimentary canal via ducts.
Pharyngeal Nephridia
- Found in segments 4, 5, and 6.
- These nephridia lack a nephrostome.
- Terminal limbs of each nephridia of a given group join to form a common duct.
- Each segment has a pair of thick-walled ducts.
- The ducts in segments 6 connect to the buccal cavity, while ducts in segments 5 and 4 connect to the pharynx.
Integumentary Nephridia
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Similar to septal nephridia, but lacking a nephrostome.
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Shaped like a small V with a short straight and a twisted loop.
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Attached to the body wall between segments to the last.
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Each nephridium directly opens via a nephridiopore to the outside.
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The number of nephridia increases significantly (2000-2500) in the clitellar region. Often referred to as forests of integumentary nephridia.
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Septal and pharyngeal nephridia are enteronephric, excreting their contents into the alimentary canal.
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Integumentary nephridia are exonephric, excreting directly to the outside of the animal.
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Glandular cells in nephridia filter water and nitrogenous wastes (urea, ammonia, amino acids).
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These wastes are collected in the excretory canals.
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Water is reabsorbed within the alimentary canal before waste is expelled via the faeces.
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Description
Test your knowledge on the excretory system of earthworms, focusing on the structure and function of nephridia. This quiz covers the different types of nephridia and their roles in excretion.
