Embryology

  • 901 views
Uploaded on

Embryology

Embryology

More in: Education
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
    Be the first to like this
No Downloads

Views

Total Views
901
On Slideshare
0
From Embeds
0
Number of Embeds
1

Actions

Shares
Downloads
16
Comments
0
Likes
0

Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
    No notes for slide

Transcript

  • 1. EMBRIOLOGIA & CICLO CELULAR JUAN CARLOS MUNEVAR
  • 2. APPLICATIONS OF MITOSIS AND MEIOSIS
  • 3. A Characteristic of Living things Growth, Division, Reproduction
  • 4. New Terms: • Development – progress through lifetime • Growth – increase in size, volume, mass • Morphogenesis – development of shapes • Epigenesis – development from a formless zygote • Differentiation – cells become different from each other • Determination – fate of cells is set (before differentiation), usually at gene control level • Induction – One tissue or substance causes determination, then differentiation, of other cells
  • 5. APOPTOSIS
  • 6. EVOLTUION OF EMBRYOS •Requires multicellularity •Only becomes embryology when cells are differentiated. •Follows a common pattern in the Animal Kingdom
  • 7. Stages in Embryology Animal Examples
  • 8. The Egg • Large, sessile gamete • Yolk – the phospholipid lecithin • Haploid nucleus (notice timing for humans and Ascaris) • Oolemma – two membranes plus jelly layer • Jelly layer -- Hyaluronic Acid and Proteins • Cortical granules – vesicles in cortex
  • 9. The Sperm • Small, motile gamete • Flagellated in animals and lower plants • Haploid nucleus • Acrosome – specialized cytoplasmic vesicle for digesting jelly layer (hyaluronidase and proteases) and for attaching to Oolemma (bindin)
  • 10. Fertilization • Sperm activated by egg hormones (gynagamones) • Formation of Acrosomal Process (microfilaments) • Release of hyaluronidase and proteases • Bindin attach to bindin recognition site on oolemma
  • 11. Egg Activation • Depolarization of membrane • Evacuation of cortical granules • Elevation of vitelline membrane (separation of vitelline membrane from egg cell membrane in oolemma) • Blocking of all other bindin sites • Activation of metabolism in cytoplasm • Completion of meiosis in some organisms
  • 12. Early cleavage • First cleavage – Two-cell stage • Second cleavage – Four-cell stage • Additional cleavages in ball shape • Morula • Blastula – first morphogenetic movements (cells migrate to form hollow ball) • Blastocoel (space) and Protoderm (tissue)
  • 13. Gastrulation • Second Morphogenetic step (first is formation of the blastula). • Tissues MOVE relative to each other and relative to their position in the embryo! • Different cells move different amounts and change shape by different amounts. • Protein gradients in embryo control this. • HOX and Homeobox genes in animal kingdom
  • 14. Morphogenesis Example of invagination Cells change shape Coordinated by position Role of Cytoskeleton
  • 15. Early Cleavage Differences • Protostomes – Spiral cleavage – Determinate – Mosaic pattern – Blastopore  mouth – Arthropods, mollusks, annelids • Deuterostomes – Radial cleavage – Indeterminate – Regulated development – Blastopore  anus – Echinoderms, chordates
  • 16. Blastula Differences • Small eggs – symmetrical blastula (Echinoderms and Mammals) • Large eggs – asymmetrical blastula (Amphibians, Reptiles, Birds) • Animal Pole – active side  ectoderm • Vegetal Pole – inactive  endoderm
  • 17. Gastrulation in Frog • Morphogenesis: invagination • Epiboly and Involution for asymmetrical eggs • Triploblastic – three tissue layers – Ectoderm – outer skin, CNS in vertebrates – Endoderm – lining of the gut – Mesoderm – inner organs and tissues – Coelom – body space in proto- and Deuterostomes.
  • 18. Notocord in Chordates • First tissue to fully differentiate • Forms in mid-dorsal mesoderm (chordamesoderm) • Induces formation of neural tube and cranial space in nearby ectoderm (dorsal side) • Replaced by spinal column (cartilage and bone from mesoderm) in vertebrates
  • 19. Differentiation of Mesoderm • Mid-dorsal – chordamesoderm • Dorsal – somites – segmented parts of body • Intermediate – thin layer, contributes to kidney and/or testicular ducts (labeled “nephrotome” in previous slide) • Lateral Plate – two sheets join at mid-ventral line – Somatic – body side – Splanchnic – surroundings of gut – Coelom – body space between two layers of mesoderm
  • 20. Pattern formation • Studied first in Drosophila • HOX and Homeobox genes found throughout animal kingdom • Frequent repeated inductions followed by determination, then differentiation • Stimulates morphogenesis, part of development
  • 21. Chick • 3-D slide from dorsal side • Note: – Somites, – Neural tube and cranial space – Notocord • Compare to Frog slices
  • 22. CLONING • Dedifferentiation of carrot cells. • Demonstration that frog cells are not terminally differentiated. • More difficult in mammals!!
  • 23. Summary • Development is part of a life cycle • Involves mitosis for nuclear division • Changes in control of DNA cause differentiation (different proteins made in different concentrations) • Genes and development steps are regulated by other genes throughout life
  • 24. LIFE CYCLES
  • 25. Reproduction • To “produce again” • Life cycle includes both diploid and haploid phases • You, as an individual, are the diploid phase of a life cycle • Emphasis on phases leads to classification of life cycles
  • 26. Generalized Life Cycle Diploid phase Haploid phase meiosisFertilization/symgamy zygote gametes Diploid adult?? Haploid adult??
  • 27. Representative Examples • Chlamydomonas – haplontic (haploid dominant) life cycle, single celled • Ulothrix – haplontic life cycle, filamentous (colony?) • Ulva – diplohaplontic life cycle, multicellular in both haploid and diploid phases, phases equal. • Fern – diplontic (diploid dominant) life cycle • Animal Kingdom – extreme diplontic life cycle; learn Echinoderm, Ascaris, human
  • 28. Haploid Phase Diploid Phase HAPLONTIC STYLE OF LIFE CYCLE
  • 29. Chlamydomonas • Protist • Chloroplast • Haplontic life cycle (Haploid dominant) • No mitosis in diploid phase of cycle • Represents very early Eukaryotic life cycles
  • 30. Chlamydomonas
  • 31. ULOTHRIX • Haplontic life cycle • “Multicellular” in haploid phase (colonial?) • Both growth and asexual reproduction by mitosis in haploid phase. • Diploid phase (resting spore) can only perform meiosis (no mitosis in diploid phase)
  • 32. New Terms • Gametophyte – the gamete-producing plant. This describes a multicellular HAPLOID phase in plant life cycles. This plant produces gametes by MITOSIS (chromosome number stays the same!). • Spore – a haploid cell that will divide by mitosis (usually to produce a gametophyte).
  • 33. More New Terms • Gametangium – in Ulothrix and many similar algae, it is a specialized cell that produces gametes by mitosis. • Sporangium, or zoosporangium – a specialized cell that produces spores (zoospores) by mitosis. • Zoospore – a spore that is flagellated.
  • 34. Diploid phase Resting spore only Haploid phase Includes spores, a multicellular filament (gametophyte), and gametes Ulothrix Haplontic style life cycle
  • 35. Alternation of generations • Ulva is our example • Introduction of mitosis in the diploid phase! • Eons of evolutionary time to develop • Loss of asexual reproduction in the haploid phase for some species. • Mitosis still in haploid phase for growth and production of gametes.
  • 36. New Terms • Sporophyte – the spore producing plant. This is the multicellular DIPLOID plant. It produces spores by MEIOSIS (chromosome number reduced from diploid to haploid). • Sporangium – specialized cells or ORGAN (multicellular structure) that produces spores by meiosis. Located on the sporophyte.
  • 37. Emphasis of Diploid Phase • Ferns, Conifers, Flowering Plants • Gametophyte becomes less important in the life cycle (smaller than sporophyte and with a shorter lifetime). • Sporophyte develops complex tissues and organs.
  • 38. New Terms for Fern • Thalus – name for the gametophyte (n). • Archegonium – gametophyte (haploid) organ that produces eggs by mitosis. • Antheridium – gametophyte (haploid) organ that produces sperm by mitosis. • Sorus – structure on underside of sporophyte leaf that contains many sporangia (diploid) that produce spores by meiosis.
  • 39. Evolutionary Trends • Shift in emphasis from haploid dominant to diploid dominant life cycles. • Shift from haploid to diploid organisms. • Single to multicellular; increased tissue differentiation; longer lives • Emphasis on mitosis for reproduction in haploid phase (asexual) to use of it for growth, then growth in diploid phase • Meiosis/fertilization ONCE per life cycle (sexual reproduction)
  • 40. SUMMARY • Switch in emphasis from dominant haploid to dominant diploid phases. • Development of multicellularity, then of tissue differentiation. • Role of MITOSIS undergoes significant change. • Roles of meiosis and fertilization do NOT change.