Human Anatomy

Base of the Brain ( Human Anatomy )

Base of the Brain (Anatomy )

Dr. Avinash Thawait , MD Anatomy , Pt JNM Medical College Raipur

Base of brain presents

1.Orbital and tentorial surfaces of  the frontal and temporal lobes of both the cerebral hemisphere. 2.Interpeduncular fossa.

3.Ventral aspect of brainstem and cerebellum.

4.Superficial attachments of the cranial nerves.

5.Circle of willis.

Human Brain

•The interpeduncularfossa is a somewhat rhomboid-shaped area of the base of the brain, limited in front by the optic chiasma, behind by the antero-superior surface of the pons, antero-laterally by the converging optic tracts, and postero-laterally by the diverging cerebral peduncles.

•The structures contained in it are : –

 (1) Posterior perforated substance

 (2) Corpora mamillaria/ mamillary bodies

 (3) Occulomotor nerve

 (4) Tuber cinereum,

 (5) Infundibulum

Nerves

Olfactory (I) Nerve

•Sensory nerve.

Sense of smell

Olfactory (I) Nerve

Optic (II) Nerve

•Sensory nerve.

•Ganglion cells in the retina of each eye join to form an optic nerve.

•Nerve of vision.

Optic (II) Nerve

Oculomotor (III) Nerve

•Motor cranial nerve.

•Originates in the midbrain.

•Supply extrinsic eye muscles to control movements of the eyeball and upper eyelid.

Oculomotor (III) Nerve

Trochlear (IV) Nerve

•Motor cranial nerve.

•Smallest of the 12 cranial nerves.

•Origin: midbrain.

•Controls movement of the eyeball.

•Largest intracranial course

Trochlear (IV) Nerve

Trigeminal (V) nerve

•Largest cranial nerve.

•Mixed nerve.

•Three branches: opthalmic, maxillary and mandibular. Deal with sensation of touch, pain and temperature.

•Motor axons supply muscles of mastication.

Trigeminal (V) nerve

Abducent (VI) Nerve

•Motor cranial nerve.

•Originates from the pons.

•Cause abduction of the eyeball (lateral rotation).

Abducent (VI) Nerve

Facial (VII) Nerve

•Mixed cranial nerve.

•Sensory portion extends from the taste buds of the anterior two-thirds of the tongue.

•Motor portion arises from the pons and deal with facial expression.

Facial (VII) Nerve

Vestibulocochlear (VIII) Nerve

•Sensory cranial nerve.

•Originates in the inner ear.

•Vestibular branch carries impulses for equilibrium.

•Cochlear branch carries impulses for hearing.

Vestibulocochlear (VIII) Nerve

Glossopharyngeal (IX) Nerve

•Mixed cranial nerve.

•Sensory axons carry signals from the taste buds of the posterior one-third of the tongue.

•Motor neurons arise from the medulla and deal with the release of saliva.

Glossopharyngeal (IX) Nerve

Vagus (X) Nerve

•Mixed cranial nerve.

•Distributed from the head and neck into the thorax and abdomen.

•Sensory neurons deal with a variety of sensations such as proprioception, and stretching.

•Motor neurons arise from the medulla and supply muscles of the pharynx, larynx, and soft palate that are involved in swallowing and vocalization.

Accessory (XI) Nerve

•Motor cranial nerve.

•Divided into cranial accessory and spinal accessory nerves.

•Supplies sternocleidomastoid and trapezius muscles to coordinate head movements.

Accessory (XI) Nerve

Hypoglossal (XII) Nerve

•Motor cranial nerve.

•Conduct nerve impulses for speech and swallowing.

Hypoglossal (XII) Nerve

Circle of Willis

•Major arteries supplying the cerebrum get interconnected to one another at the base of brain to form a six sided polygon of arteries.

•It is formed around the interpeduncular fossa and lies in the interpeduncular subarachnoid cistern.

Circle of Willis

APPLIED ANATOMY

•Congenital cerebral aneurysm – Due to congenital deficiency of the tunica media (elastic tissue). •Subarachnoid haemorrhage – Commonly results from rupture of congenital berry aneurysms.

Reference :-1. Human Anatomy , B D Chourasia

2 Gray’s Anatomy

3.John Wiley & Sons Inc.

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