Derivatives Of Ectoderm

Derivatives Of Ectoderm


DERIVATIVES OF ECTODERM

  • During week 4th to 8th the three germinal layers (ectoderm, mesoderm and endoderm) differentiate into various tissues and organs.

DERIVATIVES OF ECTODERM

  • Ectoderm is the outer most layer of trilaminar disc. 
  • It give rise to those organs and structures that maintain contact with the outside world.
  • During neurulation some of the ectodermal cells form neuroectoderm and the rest form surface ectoderm.

1. Derivatives of surface Ectoderm

1.

Skin & appendages

  • Epidermis, 
  • hair
  • nails
  • sweat glands
  • sebaceous glands.

2.

Mucous membrane of

  • Oral cavity, nasal cavity, oaranasal sinuses
  • lower part of anal canal, terminal part of urethra
  • outer surface of labia minora, whole labia majora
  • lower part of vagina.

 3.

 Eye

  •  Crystalline lens
  •  epithelium of cornea and conjunctiva, lacrimal gland.

 4.

 Ear

  • Outer layer of tympanic membrane
  • epithelial lining of membranous labyrinth.

 5.

 Glands

  • Exocrine glands (sweat glands, sebaceous glands
  • salivary glands, mammary glands, lacrimal glands).

 6.

 Teeth

  •  Enamel (Ameloblast).

 7.

 Pharyngeal Clefts

 

 2. Derivatives of Neuroectoderm

From NEURAL TUBE:

From NEURAL CREST:

  • CNS (brain, spinal cord),

A)     NEURAL DERIVATIVES

  • Astrocytes
  • Sensory neurons of 5th, 7th, 8th, 9th. 10th cranial nerve ganglia (trigeminal, geniculate, sphenopalatine, submandibular, cochlear, vestibular, otic and vagal parasympathetic ganglia).
  • Oligodendrocytes
  • Sensory neurons of spinal dorsal root ganglia.
  • Ependymal cells
  • Sympathetic chain ganglia and plexus(celiac/preaortic/renal ganglia, enteric plexus in GIT, I.e. Auerbachs and Meissner’s).
  • Retina
  • Parasympathetic ganglia and plexus of GIT.
  • Pineal gland
  • Schwann cells of peripheral nerves, satellite cells of all ganglia.
  • Neurohypophysis (posterior pituitary)
  • Adrenal  medulla, chromaffin cells, parafollicular C-cells of thyroid gland.
  • All cranial and spinal motor nerves
  • Melanocytes and melanoblasts.

 

  • Glomus cells

 

B)      MESENCHYMAL DERIVATIVES

 

  • Dermal bones of skull: Frontal, parietal, temporal, nasal, vomer, palatine, mandible, maxilla.

 

  • Leptomeninges : arachnoid and pia mater(Duramater is mesodermal).

 

  • Dentine of teeth (odontoblasts)

 

  • Eye : choroid, sclera, iris epithelium, pupillary muscles (sphincter and dilator pupillae, ciliary muscles).

 

  • Pharyngeal arch cartilages.

 

  • Retinal pigmented epithelium

 

  • Connective tissues of head including dermis, tendon, ligaments.

 

  • Bulbar and ronal ridges of heart.

Exam Question

Derivatives of surface Ectoderm

1.

Skin & appendages

  • Epidermis, 
  • hair
  • nails
  • sweat glands
  • sebaceous glands.

2.

Mucous membrane of

  • Oral cavity, nasal cavity, oaranasal sinuses
  • lower part of anal canal, terminal part of urethra
  • outer surface of labia minora, whole labia majora
  • lower part of vagina.

 3.

 Eye

  •  Crystalline lens
  •  epithelium of cornea and conjunctiva, lacrimal gland.

 4.

 Ear

  • Outer layer of tympanic membrane
  • epithelial lining of membranous labyrinth.

 5.

 Glands

  •  Exocrine glands (sweat glands, sebaceous glands
  •  salivary glands, mammary glands, lacrimal glands).

 6.

 Teeth

  •  Enamel (Ameloblast).

 7.

 Pharyngeal Clefts

 

 Derivatives of Neuroectoderm

 From NEURAL TUBE:

From NEURAL CREST:

  • CNS (brain, spinal cord),

A)     NEURAL DERIVATIVES

  • Astrocytes
  • Sensory neurons of 5th, 7th, 8th, 9th. 10th cranial nerve ganglia (trigeminal, geniculate, sphenopalatine, submandibular, cochlear, vestibular, otic and vagal parasympathetic ganglia).
  • Oligodendrocytes
  • Sensory neurons of spinal dorsal root ganglia.
  • Ependymal cells
  • Sympathetic chain ganglia and plexus (celiac/preaortic/renal ganglia, enteric plexus in GIT, I.e. Auerbachs and Meissner’s).
  • Retina
  • Parasympathetic ganglia and plexus of GIT.
  • Pineal gland
  • Schwann cells of peripheral nerves, satellite cells of all ganglia.
  • Neurohypophysis (posterior pituitary)
  • Adrenal  medulla, chromaffin cells, parafollicular C-cells of thyroid gland.
  • All cranial and spinal motor nerves
  • Melanocytes and melanoblasts.

 

  • Glomus cells

 

B)      MESENCHYMAL DERIVATIVES

 

  • Dermal bones of skull: Frontal, parietal, temporal, nasal, vomer, palatine, mandible, maxilla.

 

  • Leptomeninges : arachnoid and pia mater (Duramater is mesodermal).

 

  • Dentine of teeth (odontoblasts)

 

  • Eye : choroid, sclera, iris epithelium, pupillary muscles (sphincter and dilator pupillae, ciliary muscles).

 

  • Pharyngeal arch cartilages.

 

  • Retinal pigmented epithelium

 

  • Connective tissues of head including dermis, tendon, ligaments.

 

  • Bulbar and ronal ridges of heart.
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