Basics of human embryology 101

Ramray Bhat

Assignment 1

3 dissimilar disorders each of epithelial tissues, connective tissues, muscular tissues and neuronal tissues with cellular and molecular details

Plagiarism checkTime-bound

The first week

Tuchmann-Duplessis, H., G. David and P. Haegel. 1972.

Mulnard J G. Arch. Biol. 1967

Cleavage

-first stage of division of cells in embryogenesis.

-first 8 cells – size does not change. Cycling times ~24 h

-equal distribution of cytoplasm, protein synthesis but no mRNA transcription

-each cell called blastomere

Cleavage

-Earliest time at which different types of

cells can be identified within the

cleaving embryo is when 8 to 16 cells

are present.

-Cells spherical; no specialized

intercellular junctions or ECM;

cytoplasm organized radially around

central nucleus

-compaction, protoepithelial cyst

formation.

-asymmetric and symmetric division up

to 32 cell stage leads to differentiation

into two types.

-role of tight junctions and gap junctions

Copyright © 2011 John Wiley & Sons, Inc. All rights reserved.

Morula mass of cells at day 4 without a cavity

with a small group of internal cells (inner cell

mass) surrounded by a larger group of

external (trophectoderm) cells.

Trophectoderm forms the tissue of the chorion,

the embryonic portion of the placenta.

The cells generating the inner cell mass (ICM),

give rise to the embryo and its associated sac,

allantois, and amnion.

The distinction between trophoblast and inner

cell mass represents the first differentiation

event in mammalian development.

Morula

After division to 32 cells, the outer polar cells complete their differentiation into a

functional epithelium, display structurally complete zonular tight junctions and form

desmosomes.

The nascent trophectoderm causes vectorial fluid transport in an apical to basal

direction to generate a cavity that expands in size during the 32- to 64-cell cycles and

converts the ball of cells, the morula, to a sphere, the blastocyst or blastula with a

lumen : blastocoele

Trypsin-like enzyme used to hatch out of the

Zona pellucida by the blastocyst.

Hatched blastocysts expand and differentiation

of the inner cell mass proceeds.

Blastula

Developmental Biology. 6th edition.Gilbert SF. Sunderland (MA)

~ 4 day ~ 7-12 day

Implantation

Polar trophoblast (extraembryonic)

Epiblast (embryonic)

Hypoblast (extraembryonic)

Pregmed.org

Ectopic pregrnancy

Rejection problems

Hydatidiform moles

Placenta previa

Hydatidiform mole

Genetic examination of moles: the paternal angle

Genomic imprinting (microdeletion on chromosome 15: Prader Willi syndrome

(M) and Angelman’s syndrome (F)