Digestion anD nutrition 211The Digestive System
Body cells require nutrients for energy
and for the processes that build new
cells and cell parts.
The digestive system contributes
to homeostasis by breaking down
bulk food to nutrients, vitamins, and
minerals that can be absorbed into
the bloodstream. It also absorbs
water and stores and eliminates solid
wastes as feces.The Digestive System in Homeostasis
Skeletal system
Absorbed calcium and
phosphorus are major
components of bone
tissue.Immunity and the lymphatic system
Gastric juice and stomach enzymes help
destroy microorganisms; diarrrhea helps flush
microbes from the intestines.Muscular system
Absorbed calcium, potassium, and sodium
are needed for muscle contraction; the
lactic acid produced by working muscles is
converted to glucose in the liver.Urinary system
The kidneys use absorbed water in forming
urine; absorbed sodium is essential in
adjustments to the body’s acid–base balance
and the water content of urine.
Nervous system
Glucose from digested carbohydrates or
formed in the liver is the basic source of energy
for brain cells; absorbed sodium and potassium
are requried to generate nerve impulses.
Sensory systems
Absorbed nutrients nourish all sensory organs;
vitamin A makes pigments used in vision.Endocrine system
Pancreas, stomach, and intestinal hormones
help regulate hunger and digestion; insulin and
glucagon from the pancreas regulate blood
sugar; the liver deactivates several hormones.Cardiovascular system and blood
Absorbed water maintains blood volume; iron
is used in red blood cells to make hemoglobin;
vitamin K made in the colon is used in clotting;
many plasma proteins are made in the liver.Reproductive system
Absorbed nutrients support development of
sperm and eggs and sustain growing offspring
during pregnancy.Respiratory system
Absorbed nutrients nourish lungs and other
organs; water provides moisture needed for
gas exchange; the stomach and liver provide
physical support for the diaphragm.Integumentary
system
Excess calories may
be stored as insulating
fat in the hypodermis;
absorbed copper is
used in making melanin.11.11
connecTionS
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