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Drainage gradient (DG) is a term in road design, defined as the combined slope due to road surface cross slope (CS) and longitudinal slope (hilliness). Although the term may not be used, the concept is also used in roof design and landscape architecture. If the drainage gradient is too low, rain and melt water drainage will be insufficient.
The occipital lymph nodes, one to three in number, are located on the back of the head close to the margin of the trapezius and resting on the insertion of the semispinalis capitis. Their afferent vessels drain the occipital region of the scalp , while their efferents pass to the superior deep cervical glands .
This is known as second-half-of-the-day headache. This may be an initial presentation of a spontaneous CSF leak or appear after treatment such as an epidural patch, and likely indicates a slow spinal CSF leak. [30] While high CSF pressure can make lying down unbearable, low CSF pressure due to a leak can be relieved by lying flat on the back. [31]
The preauricular deep parotid lymph nodes (anterior auricular glands or preauricular glands), from one to three in number, lie immediately in front of the tragus. Their afferents drain multiple surfaces, most of which are lateral in origin.
Over drainage occurs when a shunt has not been adequately designed for the particular patient. Overdrainage can lead to a number of different complications some of which are highlighted below. Usually one of two types of overdrainage can occur. First, when the CSF drains too rapidly, a condition known as extra-axial fluid collection can occur.
Cerebral perfusion pressure is the net pressure gradient causing cerebral blood flow to the brain (brain perfusion). It must be maintained within narrow limits; too little pressure could cause brain tissue to become ischemic (having inadequate blood flow), and too much could raise intracranial pressure .
The head rests on the top part of the vertebral column, with the skull joining at C1 (the first cervical vertebra known as the atlas). The skeletal section of the head and neck forms the top part of the axial skeleton and is made up of the skull, hyoid bone, auditory ossicles, and cervical spine. The skull can be further subdivided into:
Headward erosion is a fluvial process of erosion that lengthens a stream, a valley or a gully at its head and also enlarges its drainage basin. The stream erodes away at the rock and soil at its headwaters in the opposite direction that it flows. Once a stream has begun to cut back, the erosion is sped up by the steep gradient the water is ...