Coelom

-

 Coelom is one of the characteristic features of metazoans. The true coelom is a body cavity formed during embryo development from the three germinal layers. The body cavity meaning a fluid filled space that can accomodate organs. The coelom is lined by mesodermal epithelium cells. Presence or absence of coelom is one of the criteria for classifying animals.

 

                                   Fig :- coelom

Animal Kingdom:- 

1. Acoelomate(no coelom)

    Ex:-Porifera ; Coelenterata ; Ctenophora; Platyhelminthes

2. Pseudocoelomate(false coelom)

         Ex :- Aschelminthes

3. Coelomate(true coelom)

           Ex :- Annelida ; Arthropoda ; Mollusca ;

Echinodermata ;Hemichordata ;Chordata


Coelom Definition 

“The coelom is the fluid-filled body cavity present between the alimentary canal and the body wall.”

The true coelom has a mesodermal origin. It is lined by mesoderm. The peritoneal cavity present in the abdomen and similar spaces around other organs such as lungs, heart are parts of the coelom. Coelom differs in its structure and formation process.


Types of Coelom

There are three types of structural body formation present in animals related to coelom: -

1. Acoelomate:

Coelom is absent. The blastocoel is completely occupied by mesoderm. E.g. Porifera, Coelenterata and Flatworms (Platyhelminthes). There is only spongocoel or coelenteron present.

2. Pseudocoelomate:

True coelom is not present. The blastocoel is partly filled by mesodermal cells. The body cavity is lined by mesoderm only towards the body wall and mesoderm is not present towards the gut. E.g. Roundworms (Aschelminthes)

3. Eucoelomate:

Animals that have a true coelom. The coelom is lined by mesoderm on both the sides, towards the body wall and towards the gut. The blastocoel present in the gastrula gets completely replaced by a true coelom. The body organs are suspended in the coelom by mesenteries. E.g. from the phylum Annelida to Chordata.


Fig :- Types of coelom

Coelom Function
* Coelom works as a shock absorber and protects from any kind of mechanical shock. It gives more flexibility to the body organs to move and protects from any damage on minor bends by cushioning the internal organs.
*Coelomic fluid acts as a hydrostatic skeleton, which helps in the locomotion of soft-bodied animals and gives the body a definite shape. Contracting muscles can push against the coelomic fluid because of the fluid pressure.
* Coelomocyte cells, that either float freely in the coelom or attached to the wall, support the immune system. They support the immune system by initiating humoral immune response and phagocytosis
* Coelomic fluid also helps in gaseous transport and transport of nutrients and waste products
Coelom gives the extra space required by organs to develop and function. E.g. pumping action of the heart, carrying a child in the womb, etc. is possible due to coelom


Popular posts from this blog

Chapter -2 Biological classification

-
Image
  Biological classification is the scientific procedure of arranging organisms into groups and subgroups on the basis of their similarities and dissimilarities and placing the group in a hierarchy of categories. Importance of classification :-  It is not possible to study every organism. Study of one or two organism of a group gives sufficient information about the essential features of the group. It helps in identification of new organism. Classification helps in knowing the relationship amongst different groups of organisms. The organism of past cannot be studied without a proper system of classification. Classification :-  (i)Artificial system of classification (ii)Natural system of classification (iii)Phylogenetic system of classification (i)Artificial system of classification- Only one or two morphological characters for grouping of organism is used. Flowering and non-flowering plants, enaima and anaima. Aristotle classification. (ii)Natural system of classification- Takes into
Read more

Human Eye

-
Image
 Human Eye The human eye is a remarkable and complex organ responsible for vision, allowing us to perceive the world around us. It collects and processes light, converting it into electrical signals that are interpreted by the brain as visual images. Here's a detailed description of the eye's anatomy and its main components: Anatomy of the Eye: External Structures: 1. Eyebrows: The eyebrows are located above the eyes and serve to prevent sweat and other particles from falling into the eyes. They also play a role in nonverbal communication and facial expressions. 2. Eyelashes: Eyelashes are situated at the edges of the eyelids and help protect the eyes by sensing and reducing the amount of light, dust, and debris that enters. 3. Eyelids (Palpebrae): The upper and lower eyelids cover and protect the front of the eye. They also help distribute tears over the surface of the eye, keeping it moist and clean. 4. Conjunctiva: A thin, transparent membrane that covers the front
Read more

Origin of Bilateria

-
Image
 Origin of Bilateria                                        First meta zones are very likely to radial animals Believed that bilateral symmetry evolved in radical ancestor when it is started creeping There are several theories given by many scientists for the Bilateria symmetrical animals are as follows:- 1.Ctenophore polyclad Theroy  :-  Ctenophores provided a a bridge or intermediate forms between                 radiate coelonterate and ancestors  and bilateral polyclad flat warms. Based on resemblance:- Oval flat and shaped with dorsal ventral differentiation Creeping on entire ventral surface Presence of two dorsal tentacles Centrally located ventral mouth Radiating, anastomosing nervous system Swimming larval stages of polycalds have eight ciliated lobes and comparable  to 8 comb rows of ctenophore  Limitations:- Cleavage is biradical in ctenophore but spiral in polyclad  Acoel flatworms are now regarded to be a most primitive 2.Planuloid-Acoeloid Theroy:-   Ludwig Von Graft form
Read more