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
Heart arteries, arterioles, and ultimately capillaries. In the capillaries, oxygen and nutrients from blood are supplied to body cells for metabolism, and exchanged for carbon dioxide and waste products. Capillary blood, now deoxygenated, travels into venules and veins that ultimately collect in the superior and inferior vena cavae, and into the right heart. The cardiac cycle refers to the sequence of events in which the heart contracts and relaxes with every heartbeat. The period of time during which the ventricles contract, forcing blood out into the aorta and main pulmonary artery, is known as systole, while the period during which the