CHICK EMBRYO DVLPT

• 4 Hours of Incubation:

  • Differentiation of blastodisc into area pellucida and area opaca
  • One quadrant of area pelluciada becomes thickened, marking the future caudal end of embryo
• 16 Hours Embryo:

  • Primitive streak becomes distinct, characterized as being in primitive streak stage
  • Central furrow called primitive groove lined by thickened primitive ridges
  • Hensen's node at cephalic end of primitive streak
  • Area pellucida assumes elliptical shape
  • Elongated primitive streak represents long axis of future embryonic body
  • Caudal end of the streak is that which lies close to the area opaca.
• 18 Hours Chick Embryo:

  • Dark peripheral area opaca and central translucent area pellucida visible
  • Presence of pro-amnion in anterior part of area pellucida
  • Primitive streak and neural groove present, separated by Hensen's node
  • Notochord formed below primitive groove
• 24 Hours or 4 Pairs of Somites Stage of Chick Embryo:

  • The neural canal, in the region of head fold, gives rise to forebrain.
  • The foregut extends on either side into an amino-cardiac vesicle.
• 30 Hours of 8-10 Pairs of Somites Chick Embryo:

  • In the region of head fold the anterior part of neural canal has given rise to a distinct forebrain
  • The foregut and cardiac vesicles are sufficiently developed.
  • The extra embryonic area has grown in size.
• 33 Hour Chick Embryo of 11-12 Pairs Somites:

  • dark peripheral area opaca and central translucent area pellucida are not distinctly visible.
  • Primitive streak reduced due to great lengthening of neural canal and neural folds
  • brain is differentiated into fore brain, mid brain and hind brain.
  • The area opaca has changed into area vasculosa.
  • Proamnion has disappeared.
  • Anterior omphalomesenteric vein has developed.
• At 36 hours if 13-14 pairs somites in a chick embryo:

  • The notochord extends from behind the brain up to the end of the body
  • Optic vesicles have developed in the forebrain region and hindbrain region
  • vitelline artery have developed.
  • The cardiac vesicle has given rise to heart.
• At 48 hours or 26-28 pairs of somites in a chick embryo

  • brain differentiated into telencephalon, prosencephalon, mesencephalon, metancephalon, and mylencephalon
  • heart differentiated into ventricle and atrium
  • Optic cup, lens, and optic vesicle have developed
  • Sinus venosus and truncus arteriosus started developing.
  • head region has curved on the right side due to cranial flexion
  • Three pharyngeal gill-slits differentiated
  • tail bud developed behind Hensen's node
  • Lateral amniotic folds, anterior omphalomesentric vein and vitelline artery appeared
• At 72 hours (36 pairs of somites) in a chick embryo:

  • Four pairs of gill-slits have been differentiated
  • Tail bud is greatly developed and has given rise to allentoic stalk and tail.
  • Lateral amniotic folds, vitelline artery and anterior omphalomesentric vein developed.
  • In the middle region a pair of fore limb buds and in front of tail a pair of hind limb buds have developed, which will give rise to fore and hind limbs.
  • Olfactory pit, visceral arches, amnion, allantois and amniotic cavity have also developed.
• At 96 hours (41 pairs of somites) in a chick embryo:

  • The entire body has turned through 90 degrees
  • The body folds have undercut the embryo, leaving it attached to the yolk by a slender stalk
  • The yolk stalk becomes elongated, allowing the embryo to straighten in the mid-dorsal region and become convex dorsally
  • Optic cup shows a more developed lens
  • Endo-lymphatic duct arises from the auditory vesicle
  • Visceral arches have become thickened
  • Appendage buds increase rapidly in size
  • Allantois has appeared
  • Omphalomesenteric artery and vein have developed
• At 7-8 hours in a chick embryo:

  • elongation of thickening, start of primitive streak
• Hensen's node is named after Victor Hensen; organizer of development
• 21 Hours Chick Embryo:

  • Embryonic and extra embryonic regions distinguished in area pellucida
  • Head fold, pocket-like extension of neural folds in anterior ectoderm
  • foregut, pocket-like structure from ectoderm the underlying endoderm
  • The proambion is comparatively reduced in size.
• At 96 hours (41 pairs of somites) in chick emrbyo:

  progressive increase in the cranial, cervical, dorsal and caudal flexures results in the bending of the embryo on itself so that its originally straight long axis becomes C-shaped and its head and tail lie close together.
• 4 hrs incubation

  A) area opaca

  B) area pellucida

  C) beginning of primitive streak with thickened blastoderm

  
• 16 hrs incubation

  A) area opaca

  B) area pellucida

  C) hensen's node

  D) primitive pit

  E) primitive groove

  F) primitive ridge

  G) cephalic end

  H) caudal end

  
• 18 hr incbtn

  
• 18 hr incbtn

  A) cephalie end

  B) proamnion

  C) anterior border of mesoderm

  D) neural plate

  E) primitive streak

  F) area pellucida

  G) area opaca

  H) hensen's node

  I) embryonal area

  J) notochord

  
• 21 hr

  A) foregut

  B) proamnion

  C) neural fold

  D) notochord

  E) hensen's node

  F) primitive groove

  G) primitive fold

  H) area opaca

  I) extra embryonic region

  J) area pellucida

  K) embryonic region

  L) neural groove

  M) head fold

  
• 24 hrs

  A) ectoderm of head

  B) area opaca vitellina

  C) proamnion

  D) mesenchyme

  E) notochord

  F) somites

  G) hensen's node

  H) primitive streak

  I) border of mesoderm

  J) blood island

  K) area vasculosa

  L) blood island

  M) unsegmented mesoderm

  N) area pellucida

  O) neural groove

  P) neural fold

  Q) margin of anterior intestinal portal vessel

  R) subcephalic pocket

  S) border of foregut

  
• 30 hr

  A) neuropore

  B) proamnion

  C) fore brain

  D) neural groove

  E) neural fold

  F) somites

  G) embryonic area

  H) hensen's node

  I) primitive groove

  J) primitive fold

  K) mesoderm

  L) area opaca

  M) notochord

  N) area pellucida

  O) extra embryonic area

  P) intestinal portal blood vessels

  Q) head fold

  
• 33 hr

  A) fore brain

  B) optic vesicle

  C) mid brain

  D) neural groove

  E) notochord

  F) mesoderm

  G) area vasculosa

  H) area opaca

  I) primitive groove

  J) primitive fold

  K) hensen's node

  L) x somite

  M) neural fold

  N) i somite

  O) hind brain

  P) head fold

  Q) proamnion

  
• 36 hr

  A) optic vesicle

  B) proamnion

  C) neural groove

  D) neural fold

  E) area vasculosa

  F) lateral body fold

  G) vitelline artery

  H) area pellucida

  I) hensen's node

  J) primitive streak

  K) mesoderm

  L) 13th somite

  M) vitelline vein

  N) 1st somite

  O) hind brain

  P) mid brain

  Q) fore gut

  R) fore brain

  
• 48 hr

  A) metencephalon

  B) mesencephalon

  C) eye

  D) lens

  E) optic cup

  F) telencephalon

  G) ventricle

  H) foregut

  I) neural groove

  J) neural fold

  K) hensen's node

  L) tail bud

  M) tail fold

  N) mesoderm plate

  O) 28th somite

  P) vitelline artery

  Q) lateral amniotic fluid

  R) atrium

  S) i somite

  T) gill slit

  U) pharynx

  V) mylencephalon

  W) vitelline vein

  X) isthmus

  
• 72 hr

  A) amnion

  B) auditory vesicle

  C) notochord

  D) mesencephalon

  E) infundibulum

  F) eye

  G) lens

  H) diencephalon

  I) cerebrum

  J) telencephalon

  K) vitelline vein

  L) vitelline artery

  M) allentoic vesicle

  N) allentoic stalk

  O) tail

  P) hind limb bud

  Q) nerve cord

  R) body fold

  S) fore limb bud

  T) heart

  U) liver

  V) sinus venosus

  W) pharynx

  X) somite

  Y) gill cleft

  
• 96 hrs

  A) telencephalon

  B) epiphysis

  C) diencephalon

  D) lens

  E) optic cup

  F) mandibular arch

  G) mesencephalon

  H) metencephalon

  I) ganglion

  J) hyomandibular cleft

  K) ganglion

  L) auditory vesicle

  M) endolymphatic duct

  N) ganglion

  O) myelencephalon

  P) branchial arch

  Q) truncus arteriosus

  R) atrium

  S) ventricle

  T) liver prominence

  U) olfactory pit

  V) anterior appendage bud

  W) omphalomesentric artery

  X) mesonephros

  Y) posterior appendage bud

  Z) somites

  [) tail

  \) allantois

  ]) omphalomesentric vein