CSB329H1 Lecture Notes - Lecture 2: Testicle, Paracrine Signalling, Unicellular Organism
9 May 2018
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Lecture 2(a): Stem Cell Systems in Porifera and Cnidarins
If we totally dissociate demosponge and hydra; capable of completely regenerating a new organism
ð Choanoflagellates is a unicellular organism; multi cellular organism is derived from
Porifera – Demosponge:
• Sponges have an impressive ability to reconstitute when destroyed under unfavorable
environmental conditions and regenerate damaged surfaces
(Simple) Sponge Anatomy:
a) Ostium Inhalant Pores/Porocytes:
o Allows water carrying nutrients are brought
into the sponge
b) Collar Cell (choanocyte):
o Flagellated cells that will trap food; and
undergo synchronized spinning that allows
water to come in and pushed out of the central cavity
c) Amoeboid Cells/Archeocytes:
o Interstitial cell – they do not have a mesoderm
§ Diploid organism: inner endoderm and outer ectoderm
(‘choanoderm’ because many choanocytes are lining the cavity)
• Between the two cell layers is the collagenous
Sponge Stem Cells, Amoeboid Cell => Amoebocytes:
• Referred to as also Amoebocytes because they are migratory
o Contain both stem-cell activity and phagocytic activity
§ Phagocytic activity – take up toxic molecules by collar cells where they are
broken down
o Flagellum:
§ Unidirectional flow of water towards the osculum
o Choanocytes:
§ Bipotent stem cells that are capable of giving rise to germ cells
o Amoebocytes:
§ Totipotent stem cells that can give rise to all cell types
ð Food that is ingest by the choanocytes are transferred to Amoebocytes where they are
digested within the cell
Document Summary
Lecture 2(a): stem cell systems in porifera and cnidarins. If we totally dissociate demosponge and hydra; capable of completely regenerating a new organism. Choanoflagellates is a unicellular organism; multi cellular organism is derived from. Diploid organism: inner endoderm and outer ectoderm ( choanoderm" because many choanocytes are lining the cavity: between the two cell layers is the collagenous. Sponge stem cells, amoeboid cell => amoebocytes: referred to as also amoebocytes because they are migratory, contain both stem-cell activity and phagocytic activity. Phagocytic activity take up toxic molecules by collar cells where they are broken down: flagellum: Unidirectional flow of water towards the osculum: choanocytes: Bipotent stem cells that are capable of giving rise to germ cells: amoebocytes: Totipotent stem cells that can give rise to all cell types. Food that is ingest by the choanocytes are transferred to amoebocytes where they are digested within the cell.
