1. GROSS ANATOMY OF THE BRAIN
Dr. G.R. Leichnetz

2. The cerebrum has five lobes: frontal, parietal, temporal, occipital, and insular.
The central sulcus separates the frontal and parietal lobes (note the two vertical gyri, pre- and post-central).
The lateral sulcus separates the frontal & parietal lobes from the temporal lobe.
A line drawn from the preoccipital notch to the parieto-occipital sulcus delineates the occipital lobe from the parietal and temporal lobes.
The insular lobe is hidden in the lateral sulcus.
Parietal Lobe
Frontal Lobe
Occipital Lobe
Temporal Lobe
Insular Lobe

3. The central sulcus delineates the frontal lobe from the parietal lobe separating two vertical gyri, the pre- and post- central gyri The lateral sulcus delineates the frontal & parietal lobes from the temporal lobe.
A line drawn from the preoccipital notch to the parietooccipital sulcus on the dorsal margin of the hemisphere delineates the parietal & temporal lobes from the occipital lobe.

4. Cerebral Hemisphere Lateral Aspect
Central sulcus
Parietal Lobe
Frontal Lobe
Occipital Lobe
Temporal Lobe
Lateral sulcus
Pre-occipital notch

5. Opening the lateral sulcus reveals the insular lobe.

6. Frontal Lobe
The precentral gyrus, the primary motor cortex, runs vertically in the posterior frontal lobe (anterior to the central sulcus).
The remainder of the frontal cortex is divided into the superior, middle, and inferior frontal gyri that run in parallel, perpendicular to the frontal pole.

7. Lateral Aspect: Frontal Lobe
Precentral gyrus
Central sulcus
Superior frontal gyrus
Middle frontal gyrus
Pars opercularis, inferior frontal gyrus
Pars triangularis, inferior frontal gyrus
Inferior frontal gyrus
Broca’s motor speech area is in the pars opercularis and triangularis in the inferior frontal gyrus of the left cerebral hemisphere.
Pars orbitalis, inferior frontal gyrus

8. The frontal lobe can also be divided into functional subdivisions based upon unique cytoarchitectural differences.
The precentral gyrus is the primary motor cortex where movements are initiated. The premotor cortex is concerned with planning movements. The prefrontal cortex is involved in “executive function” (cognition, decision-making), working memory, and the orchestration of complex behavioral responses.

9. Parietal Lobe
The postcentral gyrus, the primary somatosensory cortex, is posterior to the central sulcus.
The remainder of the parietal lobe is divided by the horizontal intraparietal sulcus into superior and inferior parietal lobules.
The inferior parietal lobule is further subdivided into the supramarginal and angular gyri (U-shaped gyri at the caudal terminus of the lateral and superior temporal sulci respectively).

10. Parietal Lobe Inferior parietal lobule Postcentral gyrus
Central sulcus
Superior parietal lobule
Intraparietal sulcus
Inferior parietal lobule
Angular gyrus
Supramarginal gyrus

11. Temporal Lobe
The lateral aspect of the temporal lobe is subdivided into three parallel superior, middle, and inferior temporal gyri that run perpendicular to the temporal pole.

12. Lateral Aspect: Temporal Lobe
Superior temporal sulcus
Lateral sulcus
Superior temporal gyrus
Middle temporal gyrus
Inferior temporal gyrus

13. Temporal Lobe: Primary Auditory Cortex
Opening the lateral sulcus reveals the superior transverse temporal gyri of Heschl on the superior aspect of the temporal lobe, the primary auditory cortex.
Superior transverse temporal gyri
Insular cortex
Superior temporal gyrus

14. Inferior Aspect of the Brain
Frontal lobe
Diencephalon (hypothalamus)
Temporal lobe
Midbrain
Pons
Medulla
The brainstem consists of the midbrain, pons, and medulla.
Cerebellum

15. Inferior Aspect of Frontal and Temporal lobes
The inferior aspect of the frontal lobe contains the orbitofrontal gyri.
The inferior aspect of the temporal lobe contains the inferior temporal gyrus, occipitotemporal (fusiform) gyrus, and the parahippocampal gyrus.
Brainstem & cerebellum removed

16. Inferior Aspect, Frontal Lobe
Olfactory bulb
Orbitofrontal gyri
Olfactory tract

17. The inferior aspect of the temporal lobe contains three parallel gyri running perpendicular to the temporal pole.
The inferior temporal gyrus lies most laterally on the lateral margin of the temporal lobe, separated by the inferior temporal sulcus from the occipitotemporal (or fusiform) gyrus. The occipito- temporal gyrus is separated from the parahippocampal gyrus by the collateral sulcus.
The hippocampal formation is rolled within the parahippocampal gyrus.

18. Medial Aspect/ Cerebral Hemisphere (Mid-Sagittal Section)
Central sulcus
Parietooccipital sulcus
Parietal
Frontal
Occipital
Cerebellum
Brainstem
The central sulcus and parietooccipital sulcus are used to delineate lobes on the medial aspect of the hemisphere.

19. Medial Aspect: Frontal & Parietal Lobes
Central sulcus
Paracentral lobule
Precuneus
Superior frontal gyrus
Cingulate gyrus
Corpus callosum
Parietooccipital sulcus
The cingulate gyrus (above the corpus callosum) is part of the “limbic lobe.” The paracentral lobule is a continuation of the pre-and post-central gyri onto the medial aspect of the hemisphere, and contains the representation of the leg.

20. Medial Aspect: Occipital Lobe
Parietooccipital sulcus
Cingulate gyrus
Precuneus
The cuneus and lingual gyri are the primary visual cortex.
Splenium, corpus callosum
Cuneus gyrus
Lingual gyrus
Calcarine fissure
Cerebellum

21. Corpus Callosum- the largest commissure of the brain, is a large bridge between the specialized hemispheres.
A commissure interconnects homologous cortical areas in opposite hemispheres.
Genu
Splenium

22. Diencephalon: Thalamus & Hypothalamus

23. Mid-Sagittal: Diencephalon
Pineal gland
Septum pellucidum
Fornix
Thalamus
Anterior commissure
Superior colliculus
Inferior colliculus
Hypothalamus
Midbrain
Optic chiasm
Mammillary body
Pons
Pituitary stalk (infundibulum)

24. Thalamus
The two thalami lie in the walls of the dorsal part of the third ventricle.
It is the principal relay station for major sensory and motor pathways to the cortex.

25. Diencephalon: Inferior Aspect
Optic nerve (C.N. II)
Optic chiasm
Pituitary stalk
Tuber cinereum (hypothalamus)
Mammillary bodies

26. Mid-Sagittal: Ventricular System
Massa intermedia
Pineal gland
Lateral ventricle
Fornix
Cerebral aqueduct
Interventricular foramen of Monro
Anterior commissure
Midbrain
Fourth ventricle
Lamina terminalis
Lateral Recess & Foramen of Luschka
Pons
Third ventricle
The interventricular foramina of Monro connect the lateral ventricles to the third ventricle. The cerebral aqueduct of the midbrain connects the third ventricle of the diencephalon to the fourth ventricle which lies above the pons and medulla below the cerebellum.

27. Hypothalamus
Hypothalamus
The hypothalamus coordinates higher-level complex autonomic (visceroendocrine) functions (eg. appetite, water & electrolyte balance, reproductive function) .

28. Brainstem

29. Brainstem: Midsagittal View
Midbrain
Cerebellum
IVth vent
Pons
Medulla
The brainstem has three portions: midbrain, pons, medulla

30. The brainstem consists of the midbrain, pons, and medulla.
Netter

31. Brainstem: Dorsal (Posterior) View
Midbrain
Pons
Medulla

32. Midbrain: Dorsal Aspect
The roof of the midbrain (midbrain tectum) contains four elevations (“corpora quadrigemina”), the two superior colliculi and inferior colliculi The trochlear nerves (C.N. IV) exit through openings inferior to the inferior colliculi.

33. Midsagittal: Midbrain/ Pons
The midbrain tectum is the roof of the midbrain above the cerebral aqueduct that contains the superior and inferior colliculi.
In a midsagittal section, the midbrain tegmentum extends from the cerebral aqueduct to the interpeduncular fossa. It is contiguous inferiorly with the pontine tegmentum.

34. Midbrain: Ventral Aspect
Optic Nerve
Optic Chiasm
Optic Tract
Oculomotor Nerve (CN III)
Tuber cinereum and pituitary stalk (hypothalamus)
Trochlear Nerve (CN IV)
Mammillary bodies
Cerebral peduncle
Pons
On the ventral aspect of the midbrain the oculomotor nerves (C.N. III) exit from the interpeduncular fossa (between the two cerebral peduncles. The trochlear nerves (C.N. IV) exit from the dorsal midbrain and curve ventrally around the cerebral peduncle.

35. Brainstem: Ventral (Anterior) View

36. Ventral Aspect: Pons & Medulla
Trigeminal Nerve (CN V)
Middle cerebellar peduncle
Pons
Abducens Nerve (CN VI)
Medulla
Vestibulocochlear Nerve (CN VIII)
Glossopharyngeal (IX) and Vagus (X) Nerves
Facial Nerve (CN VII)
Hypoglossal Nerves (CN XII)
Spinal Accessory Nerve (CN XI)
Olive
Pyramid
Pyramidal Decussation

37. Cerebellar Lobes
The cerebellum has three lobes with a vermal portion and hemispheric portion.
Anterior Lobe Posterior Lobe Flocculonodular Lobe
The cerebellum is a sensorimotor integrator. It receives spinal and vestibular input and modifies the size and velocity of ongoing movements.

38. Cerebellum: Anterior (Superior) Aspect
Lateral hemisphere
Posterior Lobe
Vermis
Primary Fissure
Anterior Lobe
Midbrain

39. Cerebellum, Posterior (Inferior) Aspect
Vermis
Pyramis
Posterior Lobe Hemisphere
Uvula
Tonsils of cerebellum
Medulla

40. Mid-sagittal: Cerebellar Vermis
Primary fissure
Anterior lobe vernis
Flocculus- hemispheric portion of the flocculonodular lobe of the cerebellum
Fourth ventricle
Posterior lobe vermis
Nodule (vermal portion of the F-N lobe)
Prenodular fissure
Tonsil

41. Cerebellar Peduncles Large bundles containing tracts that connect the cerebellum to the brainstem, form the walls of the fourth ventricle.
Netter

42. Cerebellar Peduncles
The cerebellar peduncles connect the cerebellum to the three divisions of the brainstem:
SCP to midbrain
MCP to pons
ICP to medulla.
They carry major tracts into and out of the cerebellum.
Anterior lobe hemisphere removed to reveal peduncles
Superior cerebellar peduncle
Midbrain
Middle cerebellar peduncle
Pons

43. Dorsal Aspect of the Brainstem (with cerebral cortex and cerebellum removed) The cerebellar peduncles form the walls of the fourth ventricle. The floor of the fourth ventricle is the rhomboid fossa.
Thalamus
Midbrain
Midbrain
Pons
Rhomboid fossa
Medulla

44. The floor of the fourth ventricle is the rhomboid fossa.
The “rhomboid” can be divided into two triangles. The rostral triangle is over the pons. The caudal triangle is over the medulla.
The fossa is divided vertically in half by the dorsal median sulcus. The sulcus limitans separates medial motor areas from lateral sensory areas.
Superior colliculus
Inferior colliculus
Anterior medullary velum
Superior cerebellar peduncle
Pons
Middle cerebellar peduncle FC
Medulla
Obex

45. Dorsal Aspect of the Medulla
The tracts in the dorsal columns of the spinal cord (fasciculus gracilis and cuneatus) ascend to terminate in the dorsal medulla in the nucleus gracilis and nucleus cuneatus respectively.
Obex
Gracile tubercle
Cuneate tubercle
Fasciculus graciclis
Tuberculum cinereum
Fasciculus cuneatus
Dorsal intermediate sulcus
Dorsal median sulcus

46. Ventral Aspect of the Medulla
Pontomedullary junction
Glossopharyngeal (IX) and vagus (X) nerves exiting postolivary sulcus
Olive
Hypoglossal nerve (C.N. XII) exiting preolivary sulcus
Pyramidal tract
Ventral median fissure
Pyramidal decussation

47. Brainstem: Ventral Aspect Cranial Nerves
Optic (II)
Oculomotor (III)
Trigeminal (V)
Facial (VII) and Vestibulocochlear (VIII)
Glossopharyngeal (IX) & Vagus (X) Nerves