Uncus | |
---|---|
![]() Medial surface of left cerebral hemisphere. Uncus is shown in orange. | |
Human brain inferior-medial view (Uncus is #5) | |
Identifiers | |
NeuroNames | 40 |
TA98 | A14.1.09.235 |
TA2 | 5516 |
FMA | 74884 |
Anatomical terms of neuroanatomy |
The uncus is an anterior extremity of the parahippocampal gyrus. It is separated from the apex of the temporal lobe by a sulcus called the rhinal sulcus. [1] Although superficially continuous with the hippocampal gyrus, the uncus forms morphologically a part of the rhinencephalon.
An important landmark that crosses the inferior surface of the uncus is the band of Giacomini or tail of the dentate gyrus. [2]
The term comes from the Latin word uncus, meaning hook, and it was coined by Félix Vicq-d'Azyr (1748–1794). [3]
The part of the olfactory cortex that is on the temporal lobe covers the area of the uncus, which leads into the two significant clinical aspects: herniations and seizures
This causes problems associated with a non-functional or problematic CN III - the pupil on the ipsilateral side fails to constrict to light and absence of medial/superior movement of the orbit, resulting in a fixed, dilated pupil and an eye with a characteristic "down and out" position due to dominance of the abducens and trochlear nerves. Further pressure on the midbrain results in progressive lethargy, coma and death due to compression of the mesencephalic reticular activating system.
Brainstem damage is typically ipsilateral to the herniation, although the contralateral cerebral peduncle may be pushed against the tentorial notch, resulting in a characteristic indentation known as Kernohan's notch and ipsilateral hemiparesis, since fibers running in the cerebral peduncle decussate (cross over) in the lower medulla to control muscle groups on the opposite side of the body. The landmark indicates the amygdala.
A sparse amount of literature exists to propose a comprehensive overview of the functionality of the uncus. A study has indicated that psychotic-like experiences were associated with reduced expansion within the uncus between the ages of 14 and 19 in cannabis-using individuals. [5]
Articles related to anatomy include:
The brainstem is the stalk-like part of the brain that connects the forebrain with the spinal cord. In the human brain, the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch.
The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain.
The midbrain or mesencephalon is the rostral-most portion of the brainstem connecting the diencephalon and cerebrum with the pons. It consists of the cerebral peduncles, tegmentum, and tectum.
In animal anatomy, the rhinencephalon, also called the smell-brain or olfactory brain, is a part of the brain involved with smell. It forms the paleocortex and is rudimentary in the human brain.
The limbic lobe is an arc-shaped cortical region of the limbic system, on the medial surface of each cerebral hemisphere of the mammalian brain, consisting of parts of the frontal, parietal and temporal lobes. The term is ambiguous, with some authors including the paraterminal gyrus, the subcallosal area, the cingulate gyrus, the parahippocampal gyrus, the dentate gyrus, the hippocampus and the subiculum; while the Terminologia Anatomica includes the cingulate sulcus, the cingulate gyrus, the isthmus of cingulate gyrus, the fasciolar gyrus, the parahippocampal gyrus, the parahippocampal sulcus, the dentate gyrus, the fimbrodentate sulcus, the fimbria of hippocampus, the collateral sulcus, and the rhinal sulcus, and omits the hippocampus.
In neuroanatomy, the corticobulbartract is a two-neuron white matter motor pathway connecting the motor cortex in the cerebral cortex to the medullary pyramids, which are part of the brainstem's medulla oblongata region, and are primarily involved in carrying the motor function of the non-oculomotor cranial nerves. The corticobulbar tract is one of the pyramidal tracts, the other being the corticospinal tract.
The precentral gyrus is a prominent gyrus on the surface of the posterior frontal lobe of the brain. It is the site of the primary motor cortex that in humans is cytoarchitecturally defined as Brodmann area 4.
The cerebellar tentorium or tentorium cerebelli is one of four dural folds that separate the cranial cavity into four (incomplete) compartments. The cerebellar tentorium separates the cerebellum from the cerebrum forming a supratentorial and an infratentorial region; the cerebrum is supratentorial and the cerebellum infratentorial.
The lobes of the brain are the major identifiable zones of the human cerebral cortex, and they comprise the surface of each hemisphere of the cerebrum. The two hemispheres are roughly symmetrical in structure, and are connected by the corpus callosum. They traditionally have been divided into four lobes, but are today considered as having six lobes each. The lobes are large areas that are anatomically distinguishable, and are also functionally distinct to some degree. Each lobe of the brain has numerous ridges, or gyri, and furrows, the sulci that constitute further subzones of the cortex. The expression "lobes of the brain" usually refers only to those of the cerebrum, not to the distinct areas of the cerebellum.
Brain herniation is a potentially deadly side effect of very high pressure within the skull that occurs when a part of the brain is squeezed across structures within the skull. The brain can shift across such structures as the falx cerebri, the tentorium cerebelli, and even through the foramen magnum. Herniation can be caused by a number of factors that cause a mass effect and increase intracranial pressure (ICP): these include traumatic brain injury, intracranial hemorrhage, or brain tumor.
The posterior cerebral artery (PCA) is one of a pair of cerebral arteries that supply oxygenated blood to the occipital lobe, part of the back of the human brain. The two arteries originate from the distal end of the basilar artery, where it bifurcates into the left and right posterior cerebral arteries. These anastomose with the middle cerebral arteries and internal carotid arteries via the posterior communicating arteries.
Brodmann area 35, together with Brodmann area 36, comprise the perirhinal cortex. They are cytoarchitecturally defined temporal regions of the cerebral cortex.
Duret haemorrhages are small linear areas of bleeding in the midbrain and upper pons of the brainstem. They are caused by a traumatic downward displacement of the brainstem.
In the human brain, the entorhinal cortex appears as a longitudinal elevation anterior to the parahippocampal gyrus, with a corresponding internal furrow, the external rhinal sulcus. The rhinal sulcus separates the parahippocampal uncus from the rest of the temporal lobe in the neocortex. The rhinal sulcus and the hippocampal sulcus were both present in early mammals.
The olfactory tract is a bilateral bundle of afferent nerve fibers from the mitral and tufted cells of the olfactory bulb that connects to several target regions in the brain, including the piriform cortex, amygdala, and entorhinal cortex. It is a narrow white band, triangular on coronal section, the apex being directed upward.
Kernohan's notch is a cerebral peduncle indentation associated with some forms of transtentorial herniation. It is a secondary condition caused by a primary injury on the opposite hemisphere of the brain. Kernohan's notch is an ipsilateral condition, in that a left-sided primary lesion evokes motor impairment in the left side of the body and a right-sided primary injury evokes motor impairment in the right side of the body. The seriousness of Kernohan's notch varies depending on the primary problem causing it, which may range from benign brain tumors to advanced subdural hematoma.
The tentorial notch refers to the anterior opening between the free edge of the cerebellar tentorium and the clivus for the passage of the brainstem.
This article describes anatomical terminology that is used to describe the central and peripheral nervous systems - including the brain, brainstem, spinal cord, and nerves.
This article incorporates text in the public domain from page 826 of the 20th edition of Gray's Anatomy (1918)