Tegmentum
Encyclopedia
The tegmentum is a general area within the brainstem. It is located between the ventricular system
and distinctive basal
or ventral structures at each level. It forms the floor of the midbrain whereas the tectum forms the ceiling.
It is a multisynaptic network of neurons that is involved in many unconscious homeostatic and reflexive
pathways.
. However, for fetuses to adults, tegmentum only refers to the parts of the brain that remain relatively unchanged after development is complete, i.e. at the brain stem
and midbrain. Other parts, on the other hand, develop further, through folding and thickening, and have different names. Still, it is considered a continuous central region through all levels of the brainstem.
Structures that develop to grow ventral or lateral outside this primitive tube as add-ons (e.g. the crus cerebri in the anterior of the midbrain) are not considered part of the 'tegmentum' as they are not part of the primitive neural tube but grow as projections from the cerebral cortex
. Whereas, parts that were inside the primitive neural tube and remained an integral part of it after complete development (e.g. the red nucleus
) are considered part of the tegmentum.
and medulla
to the cerebral aqueduct
in a horizontal section of the midbrain.
The lateral tegmental field (LTF) is the source of several neurons of the noradrenaline system of the brain
Ventricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...
and distinctive basal
Basal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...
or ventral structures at each level. It forms the floor of the midbrain whereas the tectum forms the ceiling.
It is a multisynaptic network of neurons that is involved in many unconscious homeostatic and reflexive
Reflexive
Reflexive may refer to:In fiction:*MetafictionIn grammar:*Reflexive pronoun, a pronoun with a reflexive relationship with its self-identical antecedent*Reflexive verb, where a semantic agent and patient are the same...
pathways.
Development
In embryos the tegmentum is the anterior half of the neural tubeNeural tube
In the developing vertebrate, the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord...
. However, for fetuses to adults, tegmentum only refers to the parts of the brain that remain relatively unchanged after development is complete, i.e. at the brain stem
Brain stem
In vertebrate anatomy the brainstem is the posterior part of the brain, adjoining and structurally continuous with the spinal cord. The brain stem provides the main motor and sensory innervation to the face and neck via the cranial nerves...
and midbrain. Other parts, on the other hand, develop further, through folding and thickening, and have different names. Still, it is considered a continuous central region through all levels of the brainstem.
Structures that develop to grow ventral or lateral outside this primitive tube as add-ons (e.g. the crus cerebri in the anterior of the midbrain) are not considered part of the 'tegmentum' as they are not part of the primitive neural tube but grow as projections from the cerebral cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
. Whereas, parts that were inside the primitive neural tube and remained an integral part of it after complete development (e.g. the red nucleus
Red nucleus
The red nucleus is a structure in the rostral midbrain involved in motor coordination. It comprises a caudal magnocellular and a rostral parvocellular part.-Function:...
) are considered part of the tegmentum.
Divisions
The tegmentum forms distinguished divisions in the midbrain, ponsPons
The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
and medulla
Medulla oblongata
The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
Midbrain tegmentum
The midbrain tegmentum is the part of the midbrain extending from the substantia nigraSubstantia nigra
The substantia nigra is a brain structure located in the mesencephalon that plays an important role in reward, addiction, and movement. Substantia nigra is Latin for "black substance", as parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in...
to the cerebral aqueduct
Cerebral aqueduct
The mesencephalic duct, also known as the aqueductus mesencephali, aqueduct of Sylvius or the cerebral aqueduct, contains cerebrospinal fluid , is within the mesencephalon and connects the third ventricle in the diencephalon to the fourth ventricle in the mesencephalon, which is between the pons...
in a horizontal section of the midbrain.
Lateral tegmental field
The lateral tegmental field (LTF) is the source of several neurons of the noradrenaline system of the brain
Other
Other pertinent areas of the tegmentum are:- Ventral Tegmental АreaVentral tegmentumThe ventral tegmentum , better known as the ventral tegmental area , is a group of neurons located close to the midline on the floor of the midbrain...
(VTA) - Periaqueductal Gray Matter
- Reticular FormationReticular formationThe reticular formation is a part of the brain that is involved in actions such as awaking/sleeping cycle, and filtering incoming stimuli to discriminate irrelevant background stimuli...
- Red NucleusRed nucleusThe red nucleus is a structure in the rostral midbrain involved in motor coordination. It comprises a caudal magnocellular and a rostral parvocellular part.-Function:...
- Substantia nigraSubstantia nigraThe substantia nigra is a brain structure located in the mesencephalon that plays an important role in reward, addiction, and movement. Substantia nigra is Latin for "black substance", as parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in...