Early Vertebrate Embryogenesis

• Gamete Formation

  sperm and eggs form, mature
• Fertilization

  sperm and egg fuse
• Cleavage

  zygote subdivides, determinants partitioned in blastomeres
• Gastrulation

  germ layers form
• Organogenesis

  body organs form, cells interact, differentiate
• Growth

  organs increase in size, adult body form attained
• Spermatogenesis

  1 spermatogonia: 1 primary spermatocyte: 2 secondary spermatocyte: 2 spermatid: 1 spermatozoa
• Oogenesis

  1 oogonia: 1 primary oocyte: 1 secondary oocyte + polar body: 1 ovum + polar body
• Spermatogenesis- starts at onset puberty of males, more differentiated

  Oogenesis- fetal stage & after birth, continues when female attained puberty
• Types of Yolk Accumulation

  fill up the table

  A) microlecithal

  B) little

  C) mesolecithal

  D) moderate

  E) macrolecithal

  F) large

  
• Microlecithal


  Type of yolk accumulation found in amphioxus, therian mammals
• Mesolecithal


  Type of yolk accumulation found in lampreys, bowfins, amphibians, and gars.
• Macrolecithal

  Type of yolk accumulation found in elasmobranchs, teleosts, reptiles, birds, and monotremes
• Type of yolk distribution

  fill up the table

  A) isolecithal

  B) even

  C) telolecithal

  D) concentrated at one pole

  
• Isolecithal


  Type of yolk distribution in therian mammals
• Telolecithal

  Type of yolk distribution in amphibians, nontherian craniates
• Process of Fertilization

  Recognition and Acrosomal Process
• Fertilization

  Fill the missing words

  A) zona pellucida

  B) hydrolytic enzymes

  C) acrosome

  D) perivitelline space

  E) plasma membrane

  F) nucleus

  G) cortical granules

  
• Polyspermy prevented through:

  formation of fertilization cone

  release of cortical granules (block other sperms to enter, solidify fertilization cone)
• Gray crescent


  region of less pigmented area in the ovuum

  after fertilization, the egg divides into two poles: vegetal and animal pole
• Gray crescent


  opposite to the point of entry of sperm

  future dorsal (back) side
• Parthenogenesis


  self division

  less male species

  during meiosis, gametes divide into 4: one cell becomes egg

  -egg (n) fertilized by a polar body= fertilized egg (zygote 2n)

  -always female (xx + xx)
• Cleavage


  rapid cell division
• Blastomeres


  cells arising from early cleavage division, makes up blastula
• Cells in:

  early cleavage- morula

  late cleavage- blastula
• Types of cleavage

  Radial cleavage- present in deuterostome

  Spiral cleavage- present in proterostome
• Types of Cleavage

  1. Holoblastic cleavage- cleavage furrow passes from the AP to the VP. two types: holoblastic equal and holoblastic unequal
  2. Meroblastic cleavage- cleavage furrow is slowed, discoidal cleavage, the yolk remains undivided and cleavage restricted at AP
• Types of Cleavage and Yolk Accumulation

  Fill the table

  A) Holoblastic equal

  B) microlecithal

  C) Holoblastic unequal

  D) mesolecithal

  E) meroblastic

  F) macrolecithal

  G) discoidal

  H) macrolecithal

  
• Holoblastic equal


  Type of cleavage found in amphioxus and therian mammals
• Holoblastic unequal


  Type of cleavage in lampreys, bowfins, gars, and amphibians
• Meroblastic


  Type of cleavage found in elasmobranchs, teleost, and fishes
• Discoidal


  Type of cleavage found in reptiles, birds, and monotremes
• Gastrulation and Neurulation


  initiation of organ development

  -two embryonic process that happens simultaneously
• Three distinct germ layers found in Gastrulation

  Ectoderm, mesoderm, endoderm
• Rearrangement of cells in gastrulation happens due to morphogenetic movements that results from:

  • active migration of cells
  • size and shape changes
  • differential cell division rates
• Patterns of Gastrulation

  A) invagination

  B) involution

  C) ingression

  D) delamination

  E) epiboly

  
• Neurulation


  process of forming ectodermal tube or the neural tube
• Neural tube


  future central nervous system
• Two types of Neurulation

  Primary Neurulation -majority of cells

  Secondary Neurulation -other parts of cells
• Notochord forms from ____

  mesodermal cells