BIO230H1 Lecture Notes - Lecture 16: Zona Pellucida, Mammary Gland, Morphogenesis
How do multicellular organisms develop?
Lecture 16: Tissue morphogenesis
Multicellular development
1. Morphogenesis
- The generation of tissue shapes that form organs and bodies
2. Cell differentiation
- The generation of the different cell types in tissues
Multicellular development requires:
- Cell proliferation
- Cell specialization
- Cell interaction
- Cell movement
Multicellular development creates different organisms and different organs within organisms
- E.g., in adults, multicellular development continually occurs from stem cells
o Basal cell layer: stem cells of skin, can become other specialized cells
o When dividing, it loses contact and becomes specialized to different cells
- E.g., adults can initiate new developmental processes, such as in the mammary
gland epithelia
o Alveoli on mammary gland dilate with milk
o Alveolar cells send proteins inwards into glands and milk is expelled into duct
Embryogenesis
- Best studied form of multicellular development
- Embryogenesis, organogenesis and stem cell development share common
mechanisms of morphogenesis and cell differentiation
o Begins when an egg is fertilized by a sperm and ends just before birth
- Animal embryogenesis begins with the formation of a ball of cells: the blastocyst.
E.g., mouse egg:
1. Fertilized mouse egg has zona pellucida (jelly-like capsule), maternal and
paternal pronuclei and polar body (non-viable products of meiosis that is
eventually destroyed)
2. 1.5 days: cell divides into two cells
3. 2.5 days: divides into 8 cells known as morula (or little mulberry). Compaction
4. 3 days: 16 cells that can become anything
5. 4 days: section of blastocysts with: zona pellucida, blastocael (fluid), inner cell
mass (becomes baby mouse; cells are very packed and can become any part of
the mouse), trophectoderm (becomes extraembryonic tissues e.g., placenta).
- Throughout development, cells become more specialized and thus lose potency
- Embryonic cells of the blastocyst undergo minimal morphogenesis and cell
differentiation
Morphogenesis
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BIO230H1 Full Course Notes
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Document Summary
The generation of tissue shapes that form organs and bodies: cell differentiation. The generation of the different cell types in tissues. Multicellular development creates different organisms and different organs within organisms. E. g. , in adults, multicellular development continually occurs from stem cells: basal cell layer: stem cells of skin, can become other specialized cells, when dividing, it loses contact and becomes specialized to different cells. E. g. , adults can initiate new developmental processes, such as in the mammary gland epithelia: alveoli on mammary gland dilate with milk, alveolar cells send proteins inwards into glands and milk is expelled into duct. Embryogenesis, organogenesis and stem cell development share common mechanisms of morphogenesis and cell differentiation: begins when an egg is fertilized by a sperm and ends just before birth. Animal embryogenesis begins with the formation of a ball of cells: the blastocyst. Throughout development, cells become more specialized and thus lose potency. Embryonic cells of the blastocyst undergo minimal morphogenesis and cell differentiation.
