D4 - Rhombencephalon

Question 1

Define r**hombenchephalon

Answer 1

Hindbrain

Question 2

What does the rhombenchephalon consists of?

Answer 2

• Myencephalon (caudal, encloses caudal part of 4^th ventricle)
  
  • Medulla oblongata
• Metencephalon (rostral, above 4^th ventricle)
  
  • Pons
  • Cerebellum

Question 3

Draw rhombecephalon

Answer 3

Question 4

Myencephalon

Structures to mention

Answer 4

• 4^th ventricle
  
  • Choroid plexus (in medullary velum)
• Cranial nerves (VI through XII)
• Trapezoid body
• Dorsal nucleus of the trapezoid body
• Pyramids
• Nulceus olivaris
• Nucleus gracilis
• Medial cuneate nucleus

Question 5

Myencephalon

1. What is myencephalon composed of?
2. What does myencephaleon enclose?

Answer 5

1. It comprises the medulla oblongata
2. Encloses:
   
   • ​Caudal part of the 4^th ventricle
   • Caudal medullary velum dorsally

Question 6

Myencephalon

Medulla oblongata

Answer 6

• Continous with the spinal cord
• Location: fossa medullae oblongata
• Nuclei located in medulla oblongata:
  
  • Nuclei of cranial nerves VI → XII
  • Caudal part of nucleus of cranial nerve V
  • Corresponding parasympathetic nuclei
  • Nuclei of respiratory and circulatory center
    
    • ​Located close to 4^th ventricle within the reticular formation
• The ventral surface is divided into halves by the ventral median fissure
• Pyramidal decussation
• Trapezoid body: at the rostral end of the pyramids
• Olivary eminence with the olivary nucleus: dorsolateral to the pyramides, at the caudal medulla oblongata
  
  • Role: controlling motor functions of the body
• Functions:
  
  • Coordinating respiration and circulation
  • Reflexes:
    
    • Protection of eye
    • Coughing
    • Swallowing

Question 7

Metencephalon

Structures to mention

Answer 7

• Pons (bridge between mesencephalon and medulla oblongata)
  
  • N. trigemini
  • Pontine nuclei
  • Transverse pontine fibers
    
    • Middle cerebellar peduncle
  • 4^th​ ventricle
    
    • Rostral medullary vellum

​

• Cerebellum
  
  • Vermis & hemispheres cortex
    
    • Folium
    • sulcus
  • White matter
  • Cerebellar nuclei
  • Cerebellar peduncles
    
    • Rostral
    • Middle
    • Caudal

Question 8

Metencephalon

What is the metencephalon composed of?

Answer 8

1. Pons
2. Cerebellum
3. Tegmentum metencephali
4. Velum medullare rostrale

Question 9

Metencephalon

Pons

Answer 9

• Bridge between medulla oblongata and mesencephalon
• Ventral aspect:
  
  • Sulcus basilaris
    
    • ​Median groove, produced by right and left pyramidal tracts
  • Pedunculus cerebellaris medialis
    
    • ​Communication between pons and cerebellum
  • Tegmentum pontis / pars dorsalis pontis
    
    • ​Floor of 4^th ventricle
• Dorsal aspect:
  
  • Tegmentum ventriculi quarti
    
    • ​Roof of 4^th ventricle
  • Obex
    
    • ​Unpaired, extends sulcus medianus to medulla oblongata
  • Velum medullare rostrale
    
    • ​Lamella of white matter between right and left pedunculus cerebellaris rostralis and lingua cerebelli
  • Velum medullare caudale
    
    • ​Lamina of white matter between right and left pedunculus cerebellaris caudalis, nodulus and tela chordea ventriculi IV
  • Tenia ventriculi quarti
• The motor nucleus of cranial nerve V (n. trigemini) is located within the pons
• Other nuclei in the pons are responsible for controlling motor funcitons of the body

Question 10

Metencephalon

Cerebellum

Answer 10

• Location: above the 4^th ventricle
• Connected to the brain stem by 3 peduncles on each side, separated form cerebral hemisphere by transveres fissura → membranous tentorium cerebelli
• Grey matter: cortex
• White matter: medulla
• Cerebellum can be divided into:
  
  • Vermis
    
    • ​Lobus rostralis
    • Lobus caudalis
    • Lobus flocculonodularis
  • Lateral hemispheres

​​

• Pedunculus cerebellaris caudalis
  
  • ​Connects cerebellum to medulla
• Pedunculus cerebellaris medialis
  
  • ​Afferent fibers from pontine nuclei
• Pedunculus cerebellaris rostralis
  
  • ​Attached to midbrain (mesencephalon)
  • Afferent fibers
• Function:
  
  • Balance
  • Coordination of skeletal muscles

Question 11

4^th ventricle

Answer 11

• Openings of the central canal
• Fluid-filled cavity
• Fossa rhomboidea
  
  • ​Floor of 4^th ventricle
• Velum medullaris rostralis & caudalis
  
  • ​Thin medullary membranes that extend between fossa rhomboidea and cerebellum like a tent.
  • Together with cerebellum: roof over 4^th ventricle

Question 12

Tegmentum ventriculi quarti, dog

Answer 12

9: Recessus lateralis ventriculi quarti
20: Tegmen ventriculi quarti
21: Velum medullare caudale
22: Velum medullare rostrale
23: Frenulum veil medullaris rostralis
25: Obex
26: Tela choroidea ventriculi quarti
27: Apertura ventriculi quarti
28: Apertura lateralis ventriculi quarti