Surface anatomy of the brainstem
Completing this study unit will allow you to:
- Describe the three parts of the brainstem.
- Identify the anatomical features of the medulla oblongata, pons and midbrain seen from an external view.
- Explore the main functions of the brainstem.
The brainstem is a stalk-like projection which extends caudally from the base of the cerebrum, connecting it with the spinal cord. It is the oldest part of the brain and is composed of three parts: the midbrain, pons and medulla oblongata.
The midbrain is the shortest segment of the brainstem. It extends caudally from the base of the thalamus (of the diencephalon) to the pons. Its functions are associated with motor coordination (in particular eye movements), visual and auditory processing, arousal/consciousness as well as behavioural responses to fear and danger.
The pons is located between the medulla oblongata and midbrain and forms the largest component of the brainstem. It houses the nuclei of cranial nerves V-VIII, as well as the pontine nuclei which facilitate corticopontocerebellar communication. It also participates in the regulation of sleep and breathing.
The medulla oblongata is the narrowest and most caudal part of the brainstem. It has a tapered appearance that extends from the pons to the spinal cord. The medulla oblongata houses the nuclei of cranial nerves XI-XII and is involved in controlling respiratory function, the cardiovascular system, as well as gastrointestinal and digestive activities.
Find out more about the surface anatomy of the brainstem from an anterior view by watching the video below.
Take a closer look now at the surface anatomy of the brainstem from a dorsal perspective.
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Take a closer look at the surface anatomy of the brainstem in the galleries.
Sulci: Lateral groove
Landmarks: Cerebral peduncles, interpeduncular fossa (mamillary body, posterior perforated substance), quadrigeminal plate (inferior colliculus, superior colliculus)
Sulci: Pontomesencephalic (/superior pontine) sulcus, basilar sulcus, medullopontine(/inferior pontine) sulcus, sulcus limitans, median sulcus of rhomboid fossa
Landmarks: Upper rhomboid fossa (median sulcus, sulcus limitans, medial eminence (facial colliculus), upper part of vestibular area, caerulean nucleus,) intermediate rhomboid fossa (medullary striae of fourth ventricle)
Parts: Superior/open (caudal part of fourth ventricle), inferior/closed (contains central canal)
Sulci: Anterior median fissure, anterolateral sulcus, posterior median sulcus, retroolivary groove, preolivary groove
Landmarks: Pyramids, decussation of pyramids, olives (olivary nuclei), gracile/cuneate tubercles, lateral funiculus, obex