[4] 4-MM & 10-MM FROG EMBRYO

• 4-MM FROG EMBRYO

  • The brain is divided into three primary regions: 
  • Prosencephalon 
  • Mesencephalon 
  • Rhombencephalon
• Prosencephalon

  • Anterior portion of the brain
  • Gives rise to the forebrain
  • Differentiates into 
  • Telencephalon - cerebral hemispheres
  • diencephalon thalamus and  hypothalamus
• Mesencephalon

  • Middle portion of the brain
  • Develops into the midbrain
• Rhombencephalon

  • Posterior portion of the brain
  • Divides into 
  • metencephalon - pons and cerebellum 
  • Myelencephalon - medulla oblongata
• • Epidermis – outermost layer
  • Prosoceol – cavity of the prosencephalon
  • Prosencephalon – first brain region exposed in the head

  
• Label:

  A) Epidermis

  B) prosocoel

  C) olfactory placode

  D) prosencephalon

  
• • Adenohypophysis (anterior pituitary) – part of the pituitary gland and serves as the anterior lobe of the pituitary
  • plays a crucial role in producing and releasing various hormones that regulate several physiological processes

  
• • Adhesive Gland – feet like structure 
  • produces a sticky secretion that helps the embryo adhere to surfaces, especially in an aquatic environment

  
• Mesocoel – cavity of the mesencephalon

  
• • Optic Cup – pair of circles seen on each lateral side
  • Arises the future eyes of the embryo
  • Optic Stalk – bridges the two optic cups
  • Adenohypophysis – serves also as the base of the optic stalk

  
• Label:

  A) mesencephalon

  B) mesocoel

  C) prosencephalon

  D) prosocoel

  E) optic cup

  F) adenohypophysis

  G) adhesive gland

  
• • Infundibulum – structure associated with the pituitary gland (in general)
  • it contributes to the formation of the pituitary gland, which plays a crucial role in producing 
  • releasing hormones that regulate various physiological processes

  
• • Rhombencephalon – last brain region
  • Rhombocoel – cavity of the rhombencephalon
  • Pharynx – passageway of food and air

  
• • Stomodeum – the primitive oral cavity
  • contributes to the formation of the mouth and oral structures during embryonic development

  
• • Optic Cup – comprises the pigmented layer of the retina, sensory layer, lens, and opticoel
  • Pigmented Layer – borders the optic cup
  • Sensory Layer – bulk layer; thick layer of the optic cup
  • Lens – circular structure
  • Opticoel – cavity of the optic cup

  
• • Notochord – found below the rhombencephalon
  • Pharynx – cavity below the notochord

  
• Label the following

  A) Notochord

  B) pharynx

  C) adhesive gland

  D) pigmented layer

  E) sensory layer

  F) lens

  G) opticoel

  
• • Optic Cup vs Otic Vesicle:
  • Optic cup  has a lens while otic vesicle does not
  • Presence of a foregut is a landmark in identifying the otic vesicle
• • Otic vesicle – the precursor to the inner ear
  • contributes to the development of structures involved in hearing and balance

  
• • Foregut – the anterior part of the primitive gut tube; gives rise to structures such as the: 
  • pharynx 
  • esophagus 
  • stomach 
  • initial portions of the respiratory and digestive systems

  
• • Heart – seen below the foregut, though not that well differentiated.

  
• Label the Following:

  A) rhombencephalon

  B) otic vesicle

  C) foregut

  D) heart

  
• • Liver Diverticulum – outgrowth from the foregut that eventually develops into the liver
  • It is the early stage of liver formation during embryonic development.
  • An extension of the foregut not a separate structure

  
• Label the structures

  A) foregut

  B) live diverticulum

  
• • Midgut – the middle portion of the primitive gut tube
  • gives rise to the small intestine and a portion of the large intestine

  
• • Spinal Cord – now seen leveled with the midgut
  • Note that by the time the otic vesicle is not visible in slides, the rhombencephalon should not be seen as well

  
• Label the structures:

  A) spinal cord

  B) middgut

  C) notochord

  D) liver diverticulum

  E) endoderm yolk mass

  
• • Hindgut – the posterior part of the primitive gut tube
  • contributes to the formation of the remaining portions of the large intestine

  
• Dorsal Fin – landmark to indicate that the specimen observed is near tail area

  
• Subnotochordal rod - dot-like structure below the notochord

  
• Somite – blocks of tissue located both laterally to the spinal cord and notochord

  
• Label the following:

  A) dorsal fin

  B) somite

  C) hindgut

  D) spinal cord

  E) notochord

  F) subnotochordal rod

  G) dorsal fin

  H) spinal cord

  I) notochord

  J) subnotochordal rod

  K) hindgut

  
• • Proctodeum – the terminal part of the primitive gut tube. 
  • it contributes to the formation of the cloaca 
  • Cloaca – common chamber for the release of digestive urinary, and reproductive products

  
• label the structures:

  A) dorsal fin

  B) subnotochordal rod

  C) proctodeum

  D) dorsal fin

  E) spinal cord

  F) notochord

  G) subnotochordal rod

  H) proctodeum

  
• 10-MM FROG EMBRYO

  • The brain is divided into five primary regions: 
  • telencephalon , diencephalon, 
  • mesencephalon
  • metencephalon, myelencephalon
• Telencephalon

  • Anterior part of the forebrain
  • Differentiates into cerebral hemispheres
• Diencephalon

  • Located between the telencephalon and midbrain
  • Differentiates into thalamus and hypothalamus
• Mesencephalon

  • The Midbrain
  • visual and auditory reflexes, motor control, and coordination of movements
• Metencephalon

  • Part of the hindbrain
  • Differentiates into pons and cerebellum
• Myelencephalon

  • Posterior part of the hindbrain
  • Develops into the medulla oblongata