Development of the Brain Flashcards
explain the development to the brain
- 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)
What brain vesicles are formed from the forebrain
- telencephalon (cranial)
- diencephalon (caudal)
What brain vesicles are formed from the hindbrain
- metencephalon
- myelencephalon
What are the adult derivatives of the secondary brain vesicles
- cerebrum
- thalami
- midbrain
- pons and cerebellum
- medulla
What do the 5 vesicles of the brain differentiate to
- 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
Explain the development of the rhombencephalon
- 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
What are the two regions of the medulla oblongata
- 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
What signals do the neuroblasts in the alar plates receive?
- 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)
What signals do the neuroblasts in the basal plates receive?
- 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)
Explain the formation of the choriod plexus and the CSF
- 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
Explain the development of the pons and cerebellum
- 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
Explain the development of the mesencephalon
- 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
Explain the development of the prosencephalon
- 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
What two tissues develop the pituitary gland?
- Hypophyseal diverticulum (roof of stomodeum)
- Neurohypophyseal diverticulum (floor of diencephalon)