Table of Contents
What is a Coelom?
A coelom is a cavity in the body that is lined with tissue derived from the mesoderm, one of the three primary germ layers in embryonic development. The coelom forms when a small hole, the blastopore, in the embryo’s surface enlarges to create a cavity. The coelom initially surrounds the gut and the heart, and later fills with fluid that helps to support and cushion organs.
Classification Based on Coelom
There are three types of body cavities:
1.coelom– a fluid filled cavity that surrounds the internal organs
2.accesory cavities- air filled cavities in the lungs and sinuses
3.cavities of the head- fluid filled cavities in the brain and eyes
Coelomates have a coelom, while accelomates do not. The coelom is a fluid filled cavity that surrounds the internal organs. Coelomates include animals such as annelids, mollusks, and arthropods. Accelomates do not have a coelom and include animals such as vertebrates.
Acoelomate and Pseudocoelomate
- Acoelomate and pseudocoelomate are two types of body cavity. An acoelomate has a body cavity that is absent of any organs, while a pseudocoelomate has a body cavity that contains some organs.
- Acoelomate and pseudocoelomate animals are two types of body plans. An acoelomate has a body cavity that is not lined with cells, while a pseudocoelomate has a body cavity that is lined with cells.
- Acoelomate animals are simple and have a smooth body surface. They do not have a gut and they digest their food outside of their body. Pseudocoelomate animals are more complex and have a gut. They digest their food inside of their body.
- Acoelomate animals include flatworms and ribbon worms. Pseudocoelomate animals include earthworms and nematodes.
- Acoelomate animals are more primitive than pseudocoelomate animals. This is because pseudocoelomate animals have a more complex body plan and gut. Acoelomate animals are not as common as pseudocoelomate animals.
Pseudocoelomate
A pseudocoelomate is an animal that has a body cavity that is not completely lined with cells. This means that the body cavity is not a true coelom. Pseudocoelomates include some worms and roundworms.
Eucoelomate
The body cavity of a eucoelomate is divided into compartments by membranes (septa). These compartments are fluid-filled and allow the animal to move its internal organs around without damaging them. This internal body fluid also allows nutrients and oxygen to reach all parts of the body.
An eucoelomate is an animal with a body cavity that is completely lined with tissue derived from the mesoderm. This tissue, the coelom, forms when the embryo splits into three layers. The outer layer, the ectoderm, becomes the skin and nervous system. The middle layer, the mesoderm, becomes the muscles, bones, and circulatory system. The inner layer, the endoderm, becomes the digestive system and lungs. In some animals, the coelom becomes filled with fluid, which helps to support and cushion the organs.
Types of Coelomates
There are three types of coelomates: pseudocoelomates, mesocoelomates, and coelomates.
- Pseudocoelomates are animals that have a body cavity that is not completely lined with cells, as is the case in coelomates. This means that pseudocoelomates do not have a true coelom. Instead, their body cavity is filled with fluid. Examples of pseudocoelomates include flatworms and nematodes.
- Mesocoelomates are animals that have a body cavity that is partially lined with cells. This means that mesocoelomates do have a true coelom. Examples of mesocoelomates include annelids and arthropods.
- Coelomates are animals that have a body cavity that is completely lined with cells. This means that coelomates do have a true coelom. Examples of coelomates include vertebrates and mollusks.
Schizocoelom
A schizocoelom is a body cavity that is split down the middle by a septum. This type of body cavity is found in invertebrates, such as worms and arthropods. The septum divides the cavity into two parts, allowing the animal to expand and contract its body cavity as needed.
A schizocoelom is a cavity in the body of an embryo that forms when the embryonic cells divide unevenly. One group of cells becomes the outer layer of cells (the ectoderm), and the other group of cells becomes the inner layer of cells (the endoderm). The space between these two layers becomes the schizocoelom.
Enterocoelom
- An acoelomate is a type of animal body plan in which there is no body cavity. This type of body plan is found in flatworms and ribbon worms.
- An enterocoelom is a body cavity that forms when the mesoderm splits into two layers. The cavity is located in the center of the embryo and is surrounded by the endoderm and ectoderm. The enterocoelom provides a space for the embryo to grow and develop.
Functions of Coelom
The coelom has several functions, including:
1. Protection – The coelom can protect the internal organs from damage.
2. Support – The coelom can help to support the internal organs.
3. Movement – The coelom can help to move the internal organs around.
4. Respiration – The coelom can help to improve respiration.
