Neck uterus. Thus the adjective "cervical" may refer either to the neck (as in "cervical vertebrae" or "cervical lymph nodes") or to the uterine cervix (as in "cervical cap" or "cervical cancer"). The neck contains vessels that link structures in the head to the body. In humans these structures include part of the esophagus, larynx, trachea, thyroid and parathyroid glands, lymph nodes, and the first part of the spinal cord. Major blood vessels present include the carotid arteries and the jugular veins. Cervical lymph nodes surround the blood vessels. The thyroid gland and parathyroid gland are endocrine glands involved in the
Drug delivery to the brain that they must pass through the cell membranes of the endothelial cells. Because of this, the only molecules that are easily able to transverse the blood–brain barrier are ones that are very lipid-soluble. These are not the only molecules that can transverse the blood–brain barrier; glucose, oxygen and carbon dioxide are not lipid-soluble but are actively transported across the barrier, to support normal cellular function of the brain. The fact that molecules have to fully transverse the endothelial cells makes them a perfect barricade to unspecified particles from entering the brain, working to protect the brain at all costs. Also,