The excretory system of the earthworm consists of three types of nephridia - septal, integumentary, and pharyngeal. Septal nephridia are located between segments and have a nephrostome, neck, body and terminal duct. They empty into septal excretory canals and supra-intestinal ducts that lead to the intestine. Integumentary nephridia are located inside the body wall and empty directly outside. Pharyngeal nephridia are located in segments 4-6 and empty into the buccal cavity or pharynx. The nephridia excrete nitrogenous wastes like ammonia, urea, and amino acids
are worm-like parasites. The clinically relevant groups are separated according to their general external shape and the host organ they inhabit. There are both hermaphroditic and bisexual species.
The definitive classification is based on the external and internal morphology of egg, larval, and adult stages.
Helminth is a general term meaning worm. The helminths are invertebrates characterized by elongated, flat or round bodies.
In flatworms or platyhelminths (platy from the Greek root meaning “flat”) include flukes and tapeworms.
Roundworms are nematodes (nemato from the Greek root meaning “thread”).
The primitive blueprint for the heart and circulatory system emerged with the arrival of the third mesodermal germ layer in bilaterians. Since then, hearts in animals have evolved from a single layered tube to a multiple chambered heart in due course of time.
are worm-like parasites. The clinically relevant groups are separated according to their general external shape and the host organ they inhabit. There are both hermaphroditic and bisexual species.
The definitive classification is based on the external and internal morphology of egg, larval, and adult stages.
Helminth is a general term meaning worm. The helminths are invertebrates characterized by elongated, flat or round bodies.
In flatworms or platyhelminths (platy from the Greek root meaning “flat”) include flukes and tapeworms.
Roundworms are nematodes (nemato from the Greek root meaning “thread”).
The primitive blueprint for the heart and circulatory system emerged with the arrival of the third mesodermal germ layer in bilaterians. Since then, hearts in animals have evolved from a single layered tube to a multiple chambered heart in due course of time.
INTRODUCTION
The term urogenital refers to something that has both urinary and genital origins. The word urogenital is used because the urinary and reproductive systems in males merge.
These are grouped together because of their proximity to each other, their common embryological origin and the use of common pathways (ex. urethra).
Kidneys and urinary ducts form the urinary system.
The Urinary system performs two important homeostatic processes like excretion and osmoregulation. This system is intimately associated both anatomically, and in terms of embryonic origin with the genital system.
The genital system includes the gonads which generate gametes and the genital ducts that serve as passages for the gametes.
Though functionally different the two organ systems the urinary and the genital system are treated together as the urino- genital system, since both develop from the same segmental blocks of trunk mesoderm or adjacent tissues and share many of the ducts.
Thus although the two systems have nothing common functionally they are closely associated in their use of common ducts and are studied under the broad heading of urinogenital system.
The function of the excretory system is crucial in considering the possible environment of the ‘vertebrate life ’. Several main functions can be attributed to all vertebrate excretory systems:
Excretion of nitrogenous waste products.
Maintaining homeostasis with regard to ions (i.e. salt balance).
Regaining valuable substances (glucose, salts, amino acids, etc.)
Maintaining a physiological osmotic value (i.e. water balance).
The excretory system is formed by a series of paired, segmental nephrons that begin with a nephrostome opening into the coelomic cavity.
A pair of glomeruli per segment, supplied by branches from the aorta, projects into the coelomic cavity close to these nephrostomes.
At a later stage of development, the glomerulus/nephrostome area becomes separated from the rest of the coelomic cavity by an epithelial fold.
The nephrons connect to a duct that is formed by caudal growth of the most anterior nephric tubules. These paired urinary ducts open near the anal region.
The vertebrate brain
The vertebrate brain is the main part of the central nervous system. The brain and the spinal cord make up the central nervous system,
In most of the vertebrates the brain is at the front, in the head. It is protected by the skull and close to the main sense organs.
Brains are extremely complex and the part of human and animal body. The brain controls the other organs of the body, either by activating muscles or by causing secretion of chemicals such as hormones and neurotransmitters.
Muscular action allows rapid and coordinated responses to changes in the environment.
The brain of an adult human weights about 1300–1400 grams .
In vertebrates, the spinal cord by itself can cause reflex responses as well as simple movement such as swimming or walking. However, sophisticated control of behaviour requires a centralized brain.
The structure of all vertebrate brains is basically the same.
At the same time, during the course of evolution, the vertebrate brain has undergone changes, and become more effective.
In so-called 'lower' animals, most or all of the brain structure is inherited, and therefore their behaviour is mostly instinctive.
In mammals, and especially in man, the brain is developed further during life by learning. This has the benefit of helping them fit better into their environment. The capacity to learn is seen best in the cerebral cortex.
Three principles
The brain and nervous system is essentially a system which makes connections. It has input from sense organs and output to muscles. It is connected in several ways with the endocrine system, which makes hormones, and the digestive system and sex system. Hormones work slowly, so those changes are gradual.
The brain is a kind of department store. It has, all inter-connected, departments which do different things. They all help each other gather senses.
Much of what the body does is not conscious. Basically, much of the body runs on automatic (breathing, heart beat, hungry, hair growth) adjusted by the autonomic nervous system. The brain, too, does much of its work without a person noticing it. The unconscious mind refers to the brain activities which are hardly ever noticed.
This presentation provide information about salient feature of cyclostomata with proper examples and explanation why they are classified in this class.
Sponges,are pore bearing,multicellular,diploblastic animals that belong to phylum Porifera
Body of all sponges is perforated by large number of pores called ostia through which water enters Inside body and flows through a system of criss-crossing canals known as canal system
Three main types of canal systems in the order of increasing complexity are Asconoid, Syconoid and Leuconoid type.
INTRODUCTION
The term urogenital refers to something that has both urinary and genital origins. The word urogenital is used because the urinary and reproductive systems in males merge.
These are grouped together because of their proximity to each other, their common embryological origin and the use of common pathways (ex. urethra).
Kidneys and urinary ducts form the urinary system.
The Urinary system performs two important homeostatic processes like excretion and osmoregulation. This system is intimately associated both anatomically, and in terms of embryonic origin with the genital system.
The genital system includes the gonads which generate gametes and the genital ducts that serve as passages for the gametes.
Though functionally different the two organ systems the urinary and the genital system are treated together as the urino- genital system, since both develop from the same segmental blocks of trunk mesoderm or adjacent tissues and share many of the ducts.
Thus although the two systems have nothing common functionally they are closely associated in their use of common ducts and are studied under the broad heading of urinogenital system.
The function of the excretory system is crucial in considering the possible environment of the ‘vertebrate life ’. Several main functions can be attributed to all vertebrate excretory systems:
Excretion of nitrogenous waste products.
Maintaining homeostasis with regard to ions (i.e. salt balance).
Regaining valuable substances (glucose, salts, amino acids, etc.)
Maintaining a physiological osmotic value (i.e. water balance).
The excretory system is formed by a series of paired, segmental nephrons that begin with a nephrostome opening into the coelomic cavity.
A pair of glomeruli per segment, supplied by branches from the aorta, projects into the coelomic cavity close to these nephrostomes.
At a later stage of development, the glomerulus/nephrostome area becomes separated from the rest of the coelomic cavity by an epithelial fold.
The nephrons connect to a duct that is formed by caudal growth of the most anterior nephric tubules. These paired urinary ducts open near the anal region.
The vertebrate brain
The vertebrate brain is the main part of the central nervous system. The brain and the spinal cord make up the central nervous system,
In most of the vertebrates the brain is at the front, in the head. It is protected by the skull and close to the main sense organs.
Brains are extremely complex and the part of human and animal body. The brain controls the other organs of the body, either by activating muscles or by causing secretion of chemicals such as hormones and neurotransmitters.
Muscular action allows rapid and coordinated responses to changes in the environment.
The brain of an adult human weights about 1300–1400 grams .
In vertebrates, the spinal cord by itself can cause reflex responses as well as simple movement such as swimming or walking. However, sophisticated control of behaviour requires a centralized brain.
The structure of all vertebrate brains is basically the same.
At the same time, during the course of evolution, the vertebrate brain has undergone changes, and become more effective.
In so-called 'lower' animals, most or all of the brain structure is inherited, and therefore their behaviour is mostly instinctive.
In mammals, and especially in man, the brain is developed further during life by learning. This has the benefit of helping them fit better into their environment. The capacity to learn is seen best in the cerebral cortex.
Three principles
The brain and nervous system is essentially a system which makes connections. It has input from sense organs and output to muscles. It is connected in several ways with the endocrine system, which makes hormones, and the digestive system and sex system. Hormones work slowly, so those changes are gradual.
The brain is a kind of department store. It has, all inter-connected, departments which do different things. They all help each other gather senses.
Much of what the body does is not conscious. Basically, much of the body runs on automatic (breathing, heart beat, hungry, hair growth) adjusted by the autonomic nervous system. The brain, too, does much of its work without a person noticing it. The unconscious mind refers to the brain activities which are hardly ever noticed.
This presentation provide information about salient feature of cyclostomata with proper examples and explanation why they are classified in this class.
Sponges,are pore bearing,multicellular,diploblastic animals that belong to phylum Porifera
Body of all sponges is perforated by large number of pores called ostia through which water enters Inside body and flows through a system of criss-crossing canals known as canal system
Three main types of canal systems in the order of increasing complexity are Asconoid, Syconoid and Leuconoid type.
The excretory system of an earthworm, like that of many other organisms, plays a crucial role in maintaining the internal balance of fluids and eliminating metabolic waste products. Earthworms are segmented worms belonging to the phylum Annelida, and their excretory system is relatively simple yet effective for their needs.
**Components of the Earthworm Excretory System:**
1. **Nephridia:** The primary excretory organs in earthworms are called nephridia (singular: nephridium). Earthworms have numerous nephridia distributed throughout their body segments. These structures resemble small, coiled tubes or tubules.
**Function of Nephridia:**
- **Filtration:** Nephridia filter the coelomic fluid, which is the fluid filling the body cavity of the earthworm. This fluid contains waste products like metabolic nitrogenous waste (ammonia and urea) and excess water.
- **Reabsorption:** Useful substances such as ions and glucose are reabsorbed from the coelomic fluid back into the bloodstream.
- **Secretion:** Nephridia also actively secrete substances, helping to regulate the composition of the coelomic fluid.
**Excretory Process in Earthworms:**
The excretory process in earthworms can be summarized as follows:
1. **Filtration:** Coelomic fluid enters the nephridium through a ciliated funnel-like structure called the nephrostome.
2. **Tubular Transport:** The fluid then moves through the tubular structure of the nephridium, where filtration, reabsorption, and secretion take place.
3. **Waste Elimination:** The waste products, including ammonia and urea, are transported out of the nephridium and are expelled from the earthworm's body through small openings called nephridiopores on the body surface. These nephridiopores are present on most segments of the earthworm, except the first few anterior segments.
**Adaptations for Terrestrial Life:**
Earthworms have evolved this excretory system as an adaptation to their terrestrial (land-dwelling) lifestyle. The excretion of nitrogenous waste as ammonia and its conversion to less toxic forms like urea is essential for conserving water in terrestrial environments.
**Importance of the Earthworm Excretory System:**
The excretory system of earthworms is vital for maintaining the internal environment of the worm, removing waste products, and regulating the composition of body fluids. This system contributes to the overall health and survival of the earthworm, allowing it to thrive in its habitat.
In summary, the excretory system of earthworms, based on nephridia, plays a critical role in maintaining the internal balance of fluids, eliminating waste products, and adapting to a terrestrial lifestyle. This system is an excellent example of how different organisms have evolved specialized mechanisms to handle excretion and osmoregulation in their unique environments.
class 11 NEET
structural organization in animal
topic FROG
morphology ,anatomy, in detail
general characteristics
digestive system
respiratory systems
circulatory system
nervous system
reproductive system
ecological values
metamorphosis
Lymphatics of head, neck & face / dental crown & bridge coursesIndian dental academy
The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and
offering a wide range of dental certified courses in different formats.for more details please visit
www.indiandentalacademy.com
The alimentary canal of Scoliodon comprises:
the mouth,
buccal cavity,
pharynx,
oesophagus,
stomach,
intestine and
rectum opening in the cloaca through anus.
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
2. Excretory System of Nephridia (Earthworm)
These are of three types according to their location in the body:
1. Septal nephridia
2. Integumentary nephridia
3. Pharyngeal nephridia.
1. Septal Nephridia:
These are found situated on the inter-segmental septum between 15th and 16th segments to the
posterior side of the body.
Each septum bears nephridia on both the surfaces arranged in semicircles around the intestine, two
rows in front of the septum and two behind it.
Each septum has about 40 to 50 nephridia in front and the same number behind, so that each segment
possesses 80 to 100 septal nephridia except the 15th segment which has only 40 to 50 nephridia.
These are not found in the segments up to 14th.
3. Structure:
The septal nephridia may be considered typical of all the
nephridia of Pheretima. Each septal nephridium consists of
nephrostome, neck, body of nephridium and the terminal
duct.
(i) Nephrostome:
It is also known as ciliated funnel or nephridiostome. It is
the proximal flattened funnel-shaped structure of the
nephridium lying in the coelom.
It has an elliptical mouth-like opening leading into an
intracellular canal of the large central cell, the margins of
the opening are surrounded by a large upper lip and a
smaller lower lip. The lips are provided with several rows
of small ciliated marginal cells and the central canal is also
ciliated.
(ii) Neck:
The nephrostome leads into a short and narrow ciliated
canal forming the neck. It joins the nephrostome to the
body of nephridium.
.
4. (iii) Body of Nephridium:
The body of nephridium has two parts a short straight lobe and a long twisted loop. The loop is
formed by two limbs- the proximal limb and the distal limb. Both these limbs are twisted spirally
around each other, the number of twists varies from nine to thirteen. The neck of nephridium and the
terminal duct join together and remain connected with the proximal limb of the twisted loop, while
the distal limb becomes the straight lobe.
Internally the nephridium is made of a connective tissue matrix having long coiled nephridial duct
forming loops. There are four such canals in the straight lobe, three in the lower part and two in the
upper part of the limbs of twisted loop. Two canals of the straight lobe out of the four are ciliated like
the ciliated canal of the neck.
(iv) Terminal Duct:
It is short and narrow with a terminal excretory duct. It joins the nephridium with septal excretory
canal.
5. Relation of septal nephridia with intestine:
The nephridia hang freely in the coelom and are attached
only by their terminal ducts. They open by their terminal
ducts into two septal excretory canals lying on the posterior
surface of the septum, one on each side of the intestine,
each begins ventrally but dorsally it opens in the supra-
intestinal excretory duct of its own side.
The supra-intestinal excretory ducts are two parallel
longitudinal canals lying above the gut and below the dorsal
vessel (Fig. 66.24). These excretory ducts begin from the
15th segment and run to the last segment, they
communicate- with each other for a short space behind each
septum, then either the right or the left duct opens by a
ductule into the lumen of the intestine near the septum.
Thus, each segment has one such opening into the intestine
of either the left or the right supra-intestinal excretory duct.
The waste collected by the nephridia is discharged through
the excretory canals and ducts into the lumen of the
intestine. Such nephridia opening into the intestine are
called enteronephric nephridia.
6. 2. Integumentary Nephridia:
In each segment of the body from 7th to the last
segment, numerous nephridia are found attached
inside the lining of the body wall. These are called
integumentary nephridia which are about 200-250 in
each segment except the segment of the clitellar
region where they number 2,000-2,500 in each
segment.
These nephridia are small-sized, without
nephrostome and without any opening into the
coelom.
Each integumentary nephridium is V-shaped with a
short straight lobe and a twisted loop, its lumen has
two ciliated canals. Each nephridium opens by a
nephridiopore on the outer surface of the body wall
directly. Since the integumentary nephridia discharge
the excretory wastes directly outside, hence, they are
called exonephric nephridia.
7. 3. Pharyngeal Nephridia:
• These nephridia lie in three paired tufts, one on either side
of the anterior region of the alimentary canal in the
segments 4th, 5th and 6th. The tufts of pharyngeal nephridia
also contain blood glands.
• Each pharyngeal nephridium is about the size of a septal
nephridium but it is of the closed type having no funnel or
nephrostome. It has a short straight lobe and a spirally
twisted loop, its lumen has ciliated canals. Ductules arise
from each nephridium and unite to form a single thick-
walled duct on each side in each segment.
• The two ducts of nephridia of segment 6th open into the
buccal cavity in segment 2nd and the paired ducts of
nephridia of segments 4th and 5th open into the pharynx in
segment 4th.
• These nephridia also discharge their wastes into the
alimentary canal and are, therefore, enteronephric but such
enteronephric nephridia which open into the anterior region
of the alimentary canal (buccal cavity and pharynx) are
called peptonephridia because they may have taken the
function of digestive glands.
• pharyngeal nephridia of P. posthuma produce a variety of
enzymes like amylase, chimosin, prolinase, prolidase,
dipeptidases, aminopeptidase, lipase, etc., which hydrolyse
various foodstuffs. Thus, such nephridia work like the
salivary glands.
8. Physiology of Excretion:
Like other animals, in earthworms also, the protein catabolism results in the formation of nitrogenous
waste substances like certain amino acids, ammonia and urea.
Uric acid is not found in the earthworms. However, the amino acids are degraded to form free ammonia
and the urea is synthesised in the chloragogen cells which are released into the coelomic fluid and also in
the blood for its removal. Free amino acids are not excreted but traces of creatinine occur in the urine.
Moreover, the nitrogen excreted in different forms in a well fed worm is about 72% NH3, 5% urea and
remaining other compounds, while in a starved worm NH3 8.6%, urea 84.5% and remaining being other
compounds. But generally, the excretion is 42% NH3, 50% urea, 0.6% amino acids and remaining being
other compounds.
So, we can say that in a well fed earthworm, NH3 predominates the nitrogenous excretory wastes, hence,
it is ammonotelic, while a starved one is ureotelic.
An earthworm excretes the nitrogenous wastes in the form of urine which generally contains urea, water,
traces of ammonia and creatinine. Nephridia excrete these substances from the body of earthworm. The
various excretory wastes from the coelomic fluid are drawn into the nephrostomes of septal nephridia or
into the excretory canals of other nephridia along with some other useful substances.
These products are either discharged into the intestine (by enteronephric nephridia) or outside by the
nephridiopores (by exonephric nephridia). The body of nephridia also absorbs some wastes. However, the
useful substances are reabsorbed and the passing out waste remains concentrated for various nitrogenous
compounds.
The excreted waste substances are removed out from the body with faeces. The nephridia, in addition to
excretory, are also osmoregulatory in function.
The nephridia help in conserving water by reabsorption from the excreted products during summers and
winters, so they pass hypertonic urine in relation to blood. During rainy season, the urine is dilute due to
lesser reabsorption of water. The enteronephric nature of nephridia provides another device for
conserving water.