Brain Gross Anatomy | Anatomy2Medicine
brain anatomy

Brain Gross Anatomy

    • The Brain weighs 350 g in the newborn and 1400 g in the adult.
    • The brain is classified into six postembryonic divisions:

 

  • Telencephalon
  • Diencephalon
  • Mesencephalon
  • Pons
  • medulla oblongata
  • cerebellum.

 

    • Telencephalon
      • consists of the cerebral hemispheres and the basal ganglia
      • The cerebral hemispheres contain the lateral ventricles.

 

  • Cerebral hemispheres consist of six lobes and the olfactory structures

 

      • Frontal lobe contains the following gyri:
        • Precentral gyrus – consists of the motor area (area 4). (MCQ)
        • Superior frontal gyrus contains the supplementary motor cortex on the medial surface (area 6).

 

  • Middle frontal gyrus contains the frontal eye field (area 8) (MCQ)
  • Inferior frontal gyrus contains the Broca speech area in the dominant hemisphere (areas 44 and 45) (MCQ)

 

        • Gyrus rectus and orbital gyri are separated by the olfactory sulcus.

 

  • Anterior paracentral lobule

 

          • is found on the medial surface between the superior frontal gyrus (paracentral sulcus) and the central sulcus.
          • represents a continuation of the precentral gyrus on the medial hemispheric surface.
      • Parietal lobe ¬†contains the following lobules and gyri:
        • Postcentral gyrus is the primary somatosensory area of the cerebral cortex (areas 3, 1, and 2).

 

  • Superior parietal lobule comprises association areas involved in somato sensory functions (areas 5 and 7 )

 

        • Supramarginal gyrus interrelates somatosensory, auditory, and visual input (area 40)
      • Temporal lobe contains the following gyri:
        • Transverse temporal gyri of Heschl is the primary auditory areas of the cerebral cortex (areas 41 and 42).
        • Superior temporal gyrus contains the Wernicke speech area in the dominant hemisphere (area 22).
      • Occipital lobe contains two structures:
        • Cuneus contains the visual cortex (areas 17, 18, and 19).

 

  • Lingual gyrus (medial occipitotemporal gyrus) contains the visual cortex (areas 17, 18, and 19).
  • Insular lobe (insula)
  • Limbic lobe

 

      • is a C-shaped structure of the medial hemispheric surface
      • includes the following structures:
        • Paraterminal gyrus and subcallosal area

 

  • Cingulate gyrus
  • Parahippocampal gyrus
  • Hippocampal formation

 

          • is connected to the hypothalamus and septal area via the fornix.
          • includes the following three structures:

 

  • Dentate gyrus
  • Hippocampus
  • Subiculum
  • Olfactory structures

 

        • are found on the orbital surface of the brain and include:

 

  • Olfactory bulb and tract

 

        • Olfactory bulb receives the olfactory nerve (cranial nerve [CN] I).

 

  • Olfactory trigone and striae

 

        • Anterior perforated substance is created by penetrating striate arteries
        • Diagonal band of Broca interconnects the amygdaloid nucleus and the septal area.

 

  • Basal ganglia

 

        • are the subcortical nuclei of the telencephalon.

 

  • Caudate nucleus
  • Putamen
  • Globus pallidus

 

          • Amygdaloid nuclear complex (amygdala)

 

  • What is striatum and lentiform nucleus (MCQ)

 

          • Striatum = Caudate nucleus + Putamen
          • lentiform nucleus = Globus pallidus + Putamen

 

  • Lateral ventricles

 

        • are ependyma-lined cavities of the cerebral hemispheres.
        • contain CSF and choroid plexus.

 

  • communicate with the third ventricle via the two interventricular foramina of Monro

 

        • are separated from each other by the septa pellucida.
      • Cerebral cortex
        • consists of a thin layer or mantle of gray substance.
        • is folded into gyri that are separated by sulci.
      • White matter includes the cerebral commissures and the internal capsule

 

  • Cerebral commissures

 

          • interconnect the cerebral hemispheres

 

  • Corpus callosum

 

            • is the largest commissure of the brain.
            • interconnects the two hemispheres.
            • has four parts: Rostrum, Genu, Body ,Splenium

 

  • Anterior commissure

 

            • interconnects the olfactory bulbs and the middle and inferior temporal lobes.
          • Hippocampal commissure (commissure of the fornix)

 

  • Internal capsule

 

          • consists of the white matter
          • located between the basal ganglia and the thalamus.
          • has three parts:

 

  • Anterior limb

 

              • located between the caudate nucleus and putamen.

 

  • Genu

 

              • located between the anterior and posterior limbs.
              • contains corticobulbar fibers

 

  • Posterior limb

 

              • located between the thalamus and lentiform nucleus
              • Contains corticospinal fibers.
    • Diencephalon
      • is located between interventricular foramen and the posterior commissure.

 

  • receives the optic nerve (CN II).
  • consists of the epithalamus, thalamus, hypothalamus, subthalamus, and the third ventricle and associated structures.

 

      • Epithalamus
        • Pineal body (epiphysis cerebri)
        • Habenular trigone
        • Medullary stria of the thalamus

 

  • Posterior commissure

 

        • mediates the consensual reaction of the pupillary light reflex.
        • Tela choroidea and choroid plexus of the third ventricle
      • Thalamus
        • consists of the following surface structures:
          • Pulvinar

 

  • Metathalamus

 

            • Medial geniculate body (auditory system)
            • Lateral geniculate body (visual system)
      • Hypothalamus

 

  • Optic chiasm
  • Mamillary body

 

        • Infundibulum
        • Tuber cinereum
      • Subthalamus (ventral thalamus)

 

  • Subthalamic nucleus

 

        • Zona incerta and fields of Forel
        • Third ventricle and associated structures
          • Lamina terminalis results from closure of the anterior neuropore.
          • Tela choroidea
          • Choroid plexus

 

  • Interventricular foramen of Monro

 

            • interconnects the lateral ventricle and the third ventricle.
          • Optic recess
          • Infundibular recess g. Suprapineal recess
          • Pineal recess
    • Mesencephalon (midbrain)

 

  • contains the cerebral aqueduct, which interconnects the third and fourth ventricles.
  • Ventral surface
  • Cerebral peduncle
  • Interpeduncular fossa
  • Oculomotor nerve (CN III)

 

        • Posterior perforated substance is created by penetrating branches of the posterior cerebral and posterior communicating arteries.

 

  • Dorsal surface
  • Superior colliculus (visual system) (MCQ)

 

        • Brachium of the superior colliculus

 

  • Inferior colliculus (auditory system) (MCQ)

 

        • Brachium of the inferior colliculus

 

  • Trochlear nerve (CN IV)

 

          • is the only cranial nerve to exit the brainstem from the dorsal aspect.
    • Pons

 

  • Ventral surface
  • Base of the pons
  • Cranial nerves (MCQ)
  • Trigeminal nerve (CN V)
  • Abducent nerve (CN VI)
  • Facial nerve (CN VII)
  • Vestibulocochlear nerve (CN VIII)
  • Dorsal surface (rhomboid fossa)
  • Locus ceruleus

 

          • contains the largest collection of norepinephrinergic neurons in the CNS. (MCQ)

 

  • Facial colliculus

 

          • contains the abducent nucleus and internal genu of the facial nerve.

 

  • Sulcus limitans (MCQ)

 

          • separates the alar plate from the basal plate.

 

  • Striae medullares of the rhomboid fossa

 

          • divide the rhomboid fossa into the superior pontine portion and the inferior medullary portion.
    • Medulla oblongata (myelencephalon)

 

  • Ventral surface

 

        • Pyramid contains the corticospinal tract.
        • Olive contains the inferior olivary nucleus. (MCQ)

 

  • Cranial nerves
  • Glossopharyngeal nerve (CN IX)
  • Vagal nerve (CN X)
  • Accessory nerve (CN XI)

 

          • Hypoglossal nerve (CN XII)

 

  • Dorsal surface

 

        • Gracile tubercle
        • Cuneate tubercle
        • Rhomboid fossa
          • Striae medullares of the rhomboid fossa

 

  • Vagal trigone

 

          • Hypoglossal trigone

 

  • Sulcus limitans
  • Area postrema (vomiting center) (MCQ)

 

    • Cerebellum
    • is located in the posterior cranial fossa.
    • is attached to the brainstem by three cerebellar peduncles.

 

  • forms the roof of the fourth ventricle.

 

    • is separated from the occipital and temporal lobes by the tentorium cerebelli.
    • consists of folia and fissures on its surface.
    • contains the following surface structures
    • Hemispheres made up of two lateral lobes.
    • Vermis is a midline structure.

 

  • Tonsil

 

        • may herniate, with increased intracranial pressure, through the foramen magnum.
    • Superior cerebellar peduncle ¬†connects the cerebellum to the pons and midbrain.
    • Middle cerebellar peduncle connects the cerebellum to the pons.
    • Inferior cerebellar peduncle connects the cerebellum to the medulla.

 

  • Anterior lobe
  • Posterior lobe
  • Flocculonodular lobe