Types of blastula, Biology

TYPES OF BLASTULA -

Blastulas are of following type -

1567_blastulation.png                  876_blastulation1.png

1.       STEREOBLASTULA -

The blastocoel is very small. It's blastomere are less in number but large in size.

It is formed as a result of spiral cleavage. eg. Neries and some molluscs.

2.       COELOBLASTULA -

The blastula of echinoderm and amphioxis is called coeloblastula.

It is formed through complete holoblastic cleavage. The blastoderm is formed of a single layer of cells.

Its blastocoel is filled wiht mucopolysaccaharide. In microlecithal egg blastocoel is centric.

In megalecithal egg blastocoel is excentric, eg. Some animal of echinodermes and amphioxis.

3.       PERIBLASTULA OR SUPERFICIAL BLASTULA -

It is formed as a result of superficial cleavage. The blastocoel is absent.

There is a single layer of blastomeres around the uncleaved yolky part, eg. Insect.

4.       DISCOBLASTULA -

It is formed as a result of discoidal cleavage. The blastocoel is small & it is called as subgerminal space. It is situated below the blastoderm, eg. Boney fishes, reptile, birds & prototherian mammals.

1732_blastula.png

5.      AMPHIBLASTULA -

It is formed of two types of structurally different blastomeres.

Example, in sycon the anterior half fo blastula is formed of flagellated cells while the posterior half is formed of large rounded granular cells on in amphibians where the two types of cells are micromeres and macromeres.

eg. Amphibians.

6.      BLASTOCYST -

It is formed in mammals as a result of holoblastic cleavage.

Outer cells are called as trophoblasts or cells of Rauber. They form a trophoderm. This layer get attached to the uterine wall.

Inner cells form the embryo & are called as inner cell mass.

eg. Human beings.

1893_types of blastula.png

Posted Date: 10/3/2012 9:23:47 AM | Location : United States







Related Discussions:- Types of blastula, Assignment Help, Ask Question on Types of blastula, Get Answer, Expert's Help, Types of blastula Discussions

Write discussion on Types of blastula
Your posts are moderated
Related Questions
Nature of Stress - Responses of Plants to Stress As mentioned in the preceding section, stress can be considered as any deviation in environmental condition from optimal for t

Explain Management of Ledge - Non-Surgical Endodontic Retreatment Place a bend of approximately 45 degree in the apical 1-2 mm of a #15 to 25 file. By gentle reciproca

Sterile Technique Every effort should be made to conduct implant surgery under sterile operating conditions. Chlorhexidine 0.2% is used as a pre-operative mouthwash and skin pr

Insect resistant crops (IRC) Should reduce use of insecticides. This is beneficial to environment because:  -  More beneficial insects around as they are not killed by in


Explain Procedure for the use of Light Microscope? Now carry out the exercise following the steps enumerated herewith. 1. Place the microscopic slide with any specimen on th

If the titration is done by adding NaOH to a solution containing 2.661 moles of lysine, how many milliliters (mL) of a 5 M solution of NaOH would you have to add to reach point "E"

Pupillary reflexes There are two types of reflexes which control the pupillary reaction-the light reflex and near reflex. When light is shown on one eye, there is a constrictio

what is r and k selection

Define Theory for Check the Presence of Rhodamine B? Addition of artificial colours to pulses, spices and tea is not permitted by PFA act. But certain colours, which contain le