Coelom: Definition, Types, Structure, Coelomic Cavity, Function

A coelom refers to any fluid-filled space inside an animal’s body between the outer body wall and the digestive tract in the body. In Animal Kingdom, animals are classified as acoelomates, pseudocoelomates, and coelomates based on their body cavity development. The True Coelom is a fluid-filled body cavity that is completely lined by mesoderm, which defines the coelomate animals in the Animal Kingdom Coelom classification.

This Story also Contains

1. What is a Coelom?
2. Importance Of Coelom In Animal Biology
3. Structure And Formation Of Coelom
4. Types Of Coelom
5. Functions of Coelom
6. Difference between Acoelomates, Pseudocoelomates, and Coelomates
7. Recommended Video for Coelom

The coelom in humans develops during gastrulation and later divides into the thoracic and abdominal cavities. The True Coelom supports and protects organs with coelomic fluid. By understanding the acoelomates, pseudocoelomates, and coelomate animals in the article, learn how coelomic fluid and the organisation of the coelom give effective coelom functions in Animal Kingdom.

What is a Coelom?

A coelom refers to a fluid-filled cavity lined exclusively with mesoderm, one of the three primary tissue layers in embryos. This cavity is important in that it allows for the further development of internal organs independently from the body wall. It increases the complexity and the degree of specialisation of animal physiology.

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• Notochord

• Animal Kingdom Basis Classification

• Bioluminescence

Importance Of Coelom In Animal Biology

The presence or absence of a coelom in the Animal Kingdom Coelom classification gives an animal’s character and material nature, whether an animal is acoelomate, pseudocoelomate, or coelomate. It controls the arrangement of the body structures and gives support to the organ systems. It is prominent over other physiological activities taking place in the body. Coeloms are not only basic but also very important in distinguishing the diversity and adaptive evolution of animals. The clear organisation of the coelom ensures efficient coelom functions, providing independent movement of the gut and better circulation of nutrients.

Structure And Formation Of Coelom

Coelom formation begins during early embryonic development with differentiation of the mesoderm (middle germ layer) into two layers just after gastrulation. The coelom has been formed by different mechanisms in different animals, such as

• Schizocoely: A process of the splitting of the mesoderm in protostomes

• Enterocoely: A process of the outpocketing of the archenteron in deuterostomes.

Out of these processes develops a fluid-filled cavity, separating the gut from the body wall, by which it gains a far more highly developed organ for operation. This process leads to the organisation of the coelom and allows it to function effectively in coelomate animals.

Types Of Coelom

In animal biology, the types of coelom—acoelomates, pseudocoelomates, and coelomates define how the body cavity develops and functions. The different types of coelom can be described as:

Coelomates (True Coelom)

Coelomate animals are distinguished by the presence of a True Coelom lined with mesoderm tissue. In turn, this coelom arrangement delivers a highly organised structure for the arrangement and function of the internal organs. Coelomate animals examples include phylum arthropoda, molluscs, chordates and annelids. Having a true coelom enables additional complexity and organ specialisation, thus making advanced physiological processes possible.

Pseudocoelomates

The body cavity of pseudocoelomate animals is lined only partially with mesodermal tissue. Pseudocoelom is derived from the blastocoel, the cavity within the embryo. Nematodes (roundworms) are a familiar example of pseudocoelomates. Though their level of organisation isn't as great as a true coelom, the pseudocoel provides space for nutrient distribution and organ system placement.

Acoelomates

Acoelomate animals are completely lacking in a coelom. For a fluid-filled cavity, they have solid tissue between their gut and body wall. Such an arrangement does not allow for high levels of complexity in internal structures. The primary model of an acoelomate animal is represented by the flatworms (Phylum Platyhelminthes). These animals, despite lacking a coelom, have adapted to several environments by some other mechanisms of physiological specialisation.

Diagram Of Different Types Of Coelom

The diagram given below shows the different types of coelom in organisms.

Functions of Coelom

The coelom performs many important functions related to body physiology and development in animals. It provides structural, protective, and transport-related functions mainly in coelomate animals like annelids and humans. Some functions of the Coelom are given below:

Physiological Roles

• Space for Organ Development and Placement

It allows for a space within which internal organs may grow independently from the body wall and therefore become organised. This is important in that it can then be separated, allowing more complex body plans and physiological processes. In coelomate animals, this space is crucial for the development of specialised organs and systems such as the heart, lungs, and intestines.

• Shock Absorption and Protection of Internal Organs

Fluid-filled, the coelom acts like a shock absorber and reduces the physical trauma transmitted to internal organs from outside the animal. This protective role has a critical function in maintaining the integrity and function of delicate structures, especially in animals that move actively or otherwise interact with their environment in a significant manner.

Circulatory Functions

• Transport of Nutrients and Gases

It eases the transport of gases and nutrients to various parts of the animal's body. In coelomate animals, this cavity may give these essential materials to various tissues and organs for metabolic processes. This is important in large-sized or complex organisms wherein simple diffusion cannot effectively distribute nutritional and gaseous materials.

Waste Removal

• Role in Excretion and Osmoregulation

It contributes to excretion and osmoregulation by helping in the removal of waste products and regulation of the levels of fluids and electrolytes within the body. The coelomic cavity leads to structures such as nephridia in annelids or kidneys in vertebrates for filtering wastes from the blood or coelomic fluid. This helps to get rid of waste efficiently and maintain homeostasis.

Difference between Acoelomates, Pseudocoelomates, and Coelomates

The organisation of the coelom plays a key role in the Animal Kingdom Coelom classification. Based on the presence, absence, and organisation of the coelom, animals are grouped intro Acoelomates, Pseudocoelomates, and Coelomates Animals.

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• Differences between Coelomate and Acoelomate

• Vermicomposting

• Earthworm Scientific Name

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