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Vagina
 The vagina is the tube that receives the male penis and sperm during intercourse. Its opening lies below the urethra, and it ends at the cervix. At birth the baby passes through the cervix and vagina, so the vagina also is called the "birth canal."

  See Also: Components of the female reproductive system

Varicose veins
 Varicose veins are swollen and enlarged veins, usually in the legs. The veins swell due to weakening in the walls of the veins. There are various causes, but the most frequent causes are prolonged standing, obesity, pregnancy, and aging. Exercise can help prevent the problem and should be part of therapy.

  See Also: Veins, Problems in the cardiovascular system

Vas deferens
 The vas deferens carry the mature sperm to the urethra to be transported to the penis. As the sperm move through the vas deferens, fluid is added to nourish and protect the sperm and to allow them to move easier within the female body. The fluid containing the sperm is called semen.

  See Also: Components of the male reproductive system, Semen

Veins
  Veins carry blood back to the heart. The capillary system leads back to the veins. Veins do not experience the same pressure on the interior walls as arteries, so they have thinner walls. However, the walls of the veins get thicker and larger as they get closer to the heart. Veins have internal valves to keep the blood flowing in the correct direction. This is very important in the legs, where the veins must bring blood back to the heart against gravity.

  See Also: Blood vessels, Cardiovascular system

Vestibule
 The vestibule consists of the utricle and saccule. It is lined with hair cells that play a role in maintaining balance.

  See Also: Ear, Inner ear, Balance

Viruses
 Viruses are even smaller than bacteria. They are not really cells, but rather simply nucleic acid.



Common diseases caused by viruses include colds, flu, cold sores, and measles. They enter a cell, release their acid, and cause the cell to make more virus. The cell dies and releases more of the virus, which then spreads to more cells. Viruses tend to be host specific--they attack specific cells and do not affect others.

  See Also: Infectious diseases, Common infectious diseases

Vision
 Vision is the detection of light. Light rays pass through the cornea and aqueous humor and are bent and directed through the pupil. The pupil opens, called "dilation," to allow light to enter the eye or closes, called "contraction," to restrict light from entering the eye. The light penetrates the lens, which changes shape to focus the image on the retina. The lens will bulge to accommodate near objects and flatten to accommodate far objects. The retina sends nerve impulses to the brain via the optic nerve. The brain interprets the impulses and gives them meaning.

  See Also: Eye, Problems of the eye

Vitamins
 Vitamins are compounds found and produced in living organisms. They are necessary for certain chemical reactions within the body.

Fat-soluble vitamins dissolve in fat. They are stored in body fat, so excesses can be harmful. The fat-soluble vitamins are Vitamin A, Vitamin D, Vitamin E, and Vitamin K. Vitamin D and Vitamin K are produced by the body. Vitamin D, along with calcium, helps build strong bones and teeth.

Water-soluble vitamins dissolve in water. They are not stored in the body, but are excreted in urine. Therefore, you need to replenish your supply to prevent deficiencies. The water-soluble vitamins are Vitamin C and the B Vitamins-- thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, folic acid, biotin, and B (12).

In order to prevent loss of these vitamins, when cooking fruits and vegetables:

  • cook them quickly
  • steam them or use only a small amount of water
  • cover them when cooking
  • use leftover liquids in soups or stews

  See Also: Essential nutrients, Nutrition, Nutrient supplements, Nutritional guidelines

Vitreous humor
 The vitreous humor is a thick fluid that keeps the eyeball firm.

  See Also: Eye, Eyeball,Choroid

Vulva
 The vulva is the external portion of the female reproductive system. Its outer section consists of the mons pubis, a layer of fat on the pubic bone; the labia majora, the two larger folds of skin on the outside of the female pubic area; and the labia minora, the two smaller folds of skin inside the labia majora.

  See Also: Components of the female reproductive system

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