BSc IV Semester Zoology Core Paper Developmental Biology - PowerPoint Presentation

Slide1

BSc IV Semester ZoologyCore Paper Developmental Biology

UNIT 1

Types

of

E

gg &

Egg

M

embranes

Types of Egg

A

lready

explained in practical class, students are directed to go through text including figures for the topic from respective practical record book.

NEXT…….

Egg membranes

INTRODUCTION

Based on the origin of the egg membrane the following classification can be

made:

Primary egg membranes

A)

Vitelline

membrane: noncellular transparent layer of mucoprotein

, forming extracellular matrix which is both fibrous and

amorphus

, often thicker and stronger than underlying plasma membrane

.

Also

Known as

Chorion

in fishes, in reptiles and mammals

zona

pelucida.B) Zona radiata: The primary envelope of shark, some bony fishes. Some amphibians and some reptiles have striated apppearance called zona radiata It represents the degraded microvilli of growing oocyte.

Continue….

Primary egg membranes

C) Jelly

envelope:

In echinoderms and many other egg of marine invertebrates, the primary egg envelope is much thicker structure of jelly coat. All

these membranes are usually adhere to plasma membrane, but at later stage a space filled

with

fluid appear between the two called

previtelline

space.

D)

Micropyle

:

In some eggs a opening

micropyle

is found in the primary egg membrane. The location of micropyle bears a definite relation to animal-vegetal polarity. E.g. Echinoderms certain mollusks, Pisces.

Secondary egg membrane/secondary envelope

Tertiary envelopes/ egg membranes

In reptiles, birds and chick five tertiary membranes make up the envelopes of the egg.

External to

vitelline

membrane are added the white of egg (albumen), two shell membranes and a porous shell (Incorporate diagram of Hen’s egg

).

Significance of egg membranes/ envelopes

References

Developmental Biology

by

T. Subramonium

Chordate

Embryology by P.S.

Verma

and

V.K.

Agarwal

.

THANKS