Nutrition and the Digestive System 379
The Importance of Vitamins
health Alert in Our DietsVitamins are essential nutrients necessary for
the successful functioning of our bod-ies.
Vitamin A is necessary for vision, bone
growth, and maintenance or epithelial cells.
Vitamin B 1 , also known as thiamine, is neces-
sary for muscle and nerve function and func-
tions as a coenzyme in energy metabolism. A
deficiency of B 1 causes wasted muscles
known as beriberi. Vitamin B 2 , also known as
riboflavin, is also involved as a coen-zyme in
energy metabolism as is Vitamin B 3 , also
known as niacin, nicotine acid, nico-tinamide,
and niacinamide. It is a part of NAD
(nicotinamide adenine dinucleotide), an
electron carrier. Vitamin B 5 , also known as
pantothenic acid, is part of Acetyl-CoA in the
Krebs cycle and is needed to make cer-tain
hormones and neurotransmitters. Vita-min B 6 ,
also known as pyridoxine, functions as a
coenzyme in amino acids and lipid me-
tabolism. Vitamin B 12 is also involved in the
metabolism of amino acids and fatty acids.
Thus, the Vitamin B complexes are very sig-
nificant for energy metabolism.^
Vitamin D is necessary for the miner-
alization of bone tissue; deficiencies can
surround the opening or orifice of the mouth. On the out-
side, the oral cavity is covered by skin and on the inside by
mucous membrane. During the chewing of food, the lips
and cheeks help keep food between the upper and lower
teeth. They also assist in speech. The hard (bony) pal-ate
forms the anterior part of the roof of the mouth. The soft
(muscular) palate forms the posterior portion of the roof
of the mouth. Hanging from its posterior border is a cone-
shaped muscular structure called the uvula (YOO-vyoo-
lah), which functions in the swallowing process and
prevents food from backing up into the nasal area.
The tongue and its associated muscles form the floor
of the oral cavity (Figure 16-3). It consists of skeletal
muscle covered with mucous membrane. It is divided into
symmetrical halves by a septum called the lingual
frenulum (LING-gwall FRIN-yoo-lum). The tongue is
at-tached to and supported by the hyoid bone. There are
two types of skeletal muscle found in the tongue: extrin-sic
and intrinsic. Extrinsic muscles originate outside the
cause rickets and osteomalacia. Vitamin K is
necessary for the clotting mechanism of blood
and for protein formation in the bone
mineralization process. Pantothenic acid is
part of coenzyme A in the Krebs cycle for
energy metabolism. Biotin is necessary for the
metabolism of carbohydrates, fats, and
proteins.
Vitamin E, also known as tocopherols,
prevents the breakdown of vitamin A and fatty
acids. Deficiencies lead to chronic fat
absorption disorders. Vitamin C, also known
as ascorbic acid, functions as a coenzyme in
energy metabolism, delivers hydrogen ions,
and functions as an antioxidant. A de-ficiency
of vitamin C leads to the disease scurvy that
weakens the body’s connective tissues and
can be fatal. We get our vitamins by eating
plant materials (cereals, fruits, and
vegetables) or from meat products (animals
that eat plant materials) such as meat, milk,
and eggs. Hence, we get our vitamins from
plants that can manufacture vitamins. Vita-
mins that we can make are vitamins K, Bio-tin,
and B 5 , which are produced by bacteria found
in our intestines.tongue and insert into it, moving the tongue from side to
side and in and out to manipulate food. Intrinsic mus-cles
originate and insert within the tongue, altering the size and
shape of the tongue for speech and swallowing. The upper
surface and sides of the tongue are covered with papillae
(pah-PILL-ee), which are projections of the lamina propria
covered with epithelium (Figure 16-4). They produce the
rough surface of the tongue. The ante-rior two-thirds
contain taste buds and are most numer-ous at the tip of the
tongue and on the posterior surface of the tongue. The
filiform (FILL-ih-form) papillae, found at the front of
the tongue, are rough and are important in licking. The
fungiform (FUN-jih-form) papillae and the
circumvallate (sir-kum-VAL-ate) papillae, found
toward the back of the tongue, all contain taste buds. There
are five tastes: sweet, sour, salt, umami, and bitter. The
taste of umami was identified by Japanese researchers. It
de-tects MSG (monosodium glutamate), a distinct flavor
popular in Asian foods.