Development of the Brain

Question 1

explain the development to the brain

Answer 1

• The cranial part of the neural tube becomes the brain
• The neural tube dilates in the 4th week which produces the:
• forebrain (prosencephalon), midbrain (mesencephalon), hindbrain (rhombencephalon)
• during the 5th week of development, 5 secondary brain vesicles were developed when the fore and hindbrain divide
• head folding causes the development of the midbrain (cranial) and cervical flexure (caudal)

Question 2

What brain vesicles are formed from the forebrain

Answer 2

• telencephalon (cranial)
• diencephalon (caudal)

Question 3

What brain vesicles are formed from the hindbrain

Answer 3

• metencephalon
• myelencephalon

Question 4

What are the adult derivatives of the secondary brain vesicles

Answer 4

• cerebrum
• thalami
• midbrain
• pons and cerebellum
• medulla

Question 5

What do the 5 vesicles of the brain differentiate to

Answer 5

• Telencephalon: cerebral hemispheres, lateral ventricles
• Diencephalon: Thalamus, hypothalamus, epithalamus, third ventricle
• Mesencephalon: anterior & posterior colliculi, cerebral aqueduct of Sylvius
• Metencephalon: cerebellum, pons, upper fourth ventricle
• Myelencephalon: medulla oblongata, lower fourth ventricle

Question 6

Explain the development of the rhombencephalon

Answer 6

• The cervical flexure demarcates the hindbrain from the spinal cord
• The pontine flexure divides the hindbrian into the myel and metencephalon
• Myelencephalon → medulla oblongata (gracile (medial) and cuneate (lateral) nuclei formed by neuroblasts from alar plate → marginal zone)
• Metencephalon → pons, cerebellum

Question 7

What are the two regions of the medulla oblongata

Answer 7

• The caudal closed region: neuroblasts of alar plate form gracile and cuneate nuclei
• The cranial opened region (wide and flat): motor nuclei medial to sensory nuclei. neural canal is part of the 4th ventricle

Question 8

What signals do the neuroblasts in the alar plates receive?

Answer 8

• They are arranged in 4 columns from medial → lateral
• general visceral afferent neuroblasts (from viscera)
• special visceral afferent neuroblasts (taste fibers)
• general somatic afferent (from surface of the head)
• special somatic afferent (from the ear)

Question 9

What signals do the neuroblasts in the basal plates receive?

Answer 9

• They are arranged in 3 columns from medial → lateral
• general somatic efferent neuroblasts (going to hypoglossal nerve)
• special visceral efferent neuroblasts (going to muscles from the pharyngeal arches)
• general visceral efferent neuroblasts (going to neurons of the vagus and glossopharyngeal nerves)

Question 10

Explain the formation of the choriod plexus and the CSF

Answer 10

• The pia mater covers the external part of the fourth ventricle
• pia mater + ependymal roof of fourth ventricle = tela choriodea
• The pia mater proliferates making the tela choroidea invaginate into the fourth ventricle = choriod plexus
• The choriod plexus secretes a fluid that later becomes the CSF

Question 11

Explain the development of the pons and cerebellum

Answer 11

• alar plates thicken to form the cerebellum and neuroblasts → marginal zone = cerebellar cortex (grey matter)
• The pons has fibers connecting the cerebrum to the cerebellum and spinal cord

Question 12

Explain the development of the mesencephalon

Answer 12

• Doesn’t go thru that much change (similar to spinal cord)
• Neuroblasts of alar plate → superior (cranial) and inferior (caudal) colliculi which are involved in the visual and auditory reflexes
• the ventral aspect of the basal plate neuroblasts have 2 bulges → cerebral peduncles (fiber tracts form the cerebrum)
• neural canal = cerebral aqueduct

Question 13

Explain the development of the prosencephalon

Answer 13

• It develops into the diencephalon and telencephalon
• Diencephalon: caudal part of the forebrain, gives rise to epithalamus, thalamus and hypothalamus
• Neural canal becomes the third ventricle
• Telencephalon: cranial part of the forebrain → cerebrum
• 2 bubble like cerebral vesicles → left and right cerebral hemispheres → 1 C-shaped hemisphere
• Neural canal → lateral ventricles
• Intermediate layer cells → marginal zone = cerebral cortex
• cerebral surface becomes convoluted → gyri & sulci

Question 14

What two tissues develop the pituitary gland?

Answer 14

• Hypophyseal diverticulum (roof of stomodeum)
• Neurohypophyseal diverticulum (floor of diencephalon)