The<unk>  is a set of interconnected nuclei that are located throughout the brainstem. It is not anatomically well defined, because it includes neurons located in different parts of the brain. The neurons of the<unk>  make up a complex set of networks in the core of the brainstem that extend from the upper part of the midbrain to the lower part of the medulla oblongata. The<unk>  includes ascending pathways to the cortex in the ascending<unk>  activating system (ARAS) and descending pathways to the spinal cord via the reticulospinal tracts. Neurons of the<unk> , particularly those of the ascending<unk>  activating system, play a crucial role in maintaining behavioral arousal and consciousness. The overall functions of the<unk>  are modulatory and premotor, involving somatic motor control, cardiovascular control, pain modulation, sleep and consciousness, and habituation. The modulatory functions are primarily found in the rostral sector of the<unk>  and the premotor functions are localized in the neurons in more caudal regions. The<unk>  is divided into three columns: raphe nuclei (median), gigantocellular<unk>  nuclei (medial zone), and parvocellular<unk>  nuclei (lateral zone). The raphe nuclei are the place of synthesis of the neurotransmitter serotonin, which plays an important role in mood regulation. The gigantocellular nuclei are involved in motor coordination. The parvocellular nuclei regulate exhalation. The<unk>  is essential for governing some of the basic functions of higher organisms and is one of the phylogenetically oldest portions of the brain.
Reticular formation
Moist desquamation
Craterization
Hyperkeratinization
Organ gifting
Desquamation
Glomerulation
Tissue expansion