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Class Notes for Health Unit 1 Nutrition, Digestion and
Excretion
Nutrition- the taking in and utilization of food substances
whereby growth, repair and maintenance of the body are
accomplished
Food- any substance taken into the body that yields energy
and builds tissue. These substances are called nutrients
Glucose- the body’s first source of energy
When we do work (any activity) the energy released (heat
energy) is measured in terms of calories
Calorie- the amount of heat required to raise the
temperature of 1 gram of water by 1º Centigrade
Metabolism- all processes involved in substance usage
inside the body
The more calories a food has the more energy it has
Carbohydrates yield 4 calories/gram
Proteins yield 4 calories/gram
Fats yield 9 calories/gram
Six types of nutrients
1. Carbohydrates
2. Proteins
3. Fats
4. vitamins
5. minerals
6. water
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1. Carbohydrates- sugars (simple carbohydrates) and
starches (complex carbohydrates) are made of carbon,
hydrogen and oxygen
Cellulose- a starch also called fiber that provides bulk
and exercises the smooth muscle tissue of the digestive
tract. It cannot be digested by the human digestive
system
During digestion, simple and complex carbs are broken
down into glucose which circulates in the blood.
When the body has sufficient glucose to meet its needs,
the body stores the energy in the muscles and liver as
glycogen (primary source of energy during high intensity
exercise)
When the glycogen levels are full, the body stores the
energy as fat
2. Fat- carries vitamins A, D, E and K and has twice the
energy of carbohydrates
During digestion, fats are broken down into fatty acids
which is used by most cells for energy except for red
blood cells and cells of the central nervous system
Saturated fats- come from animal flesh and are
saturated with Hydrogen
Unsaturated fats- come from vegetables, nuts and seeds
and are healthier than saturated fats
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Proteins- major component of all body tissue. Amino
acids are the building blocks of proteins
Proteins
1. maintain and repair body tissues
2. make hemoglobin which carries O2 to the cells
3. form antibodies in the blood that fight disease and
infection
4. produce enzymes and hormones that regulate body
processes
5. supply energy if necessary
Vitamins- supplied by foods in our diet.
Vitamin supplements do not provide energy
Fat Soluble Vitamins- A, D, E and K. these dissolve in
fat and can be stored in the body. Excessive amounts
(mega doses) can be harmful
A- eye and skin health. Resistance to infection
D- aids in the absorption of calcium and phosphorus.
Produced by the body when exposed to the UV rays of
the sun
E- protects arteries from the damage of cholesterol
K- has an important role in blood clotting. Rescue drug
for hemophiliacs
Water Soluble- vitamins C and the B complex are
broken down in water. Excessive amounts not harmful
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Minerals- compounds occurring in nature. Found in
the soil and water and become incorporated into plant
and animal life. Essential in all cells
Water- essential for life
1. approximately 60% of body weight is water
2. acts as a coolant to keep the body from overheating
3. lubricates joints and internal organs
4. softens food prior to swallowing
5. solvent for the elimination of fecal material
6. major component of blood
Food Groups
Meat- beef, poultry, pork, fish and beans. Soy beans are
so rich in protein they are in the meat group
Vegetables/ Fruit- source of vitamins and minerals
Bread- grains and cereals. Source of fiber (cellulose)
Milk- all dairy products. High in fat content. Source of
proteins and vitamins
Computing Your daily Nutritional Needs
See handouts and assignment online…
The Human Digestive System
Digestion- process by which is mechanically and
chemically broken down into usable forms (starches, fats
and proteins). Salt, simple carbs (simple sugars) and
water are absorbed unchanged
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Digestion begins in the mouth. When you masticate
(chew), the salivary glands secrete saliva which
lubricates the food making it easier to swallow
Saliva contains an enzyme called amylase which begins
to chemically break food down prior to swallowing
The GI tract (gastrointestinal) is a continuous tube
beginning in the mouth and ending in the anal canal
Swallowing pushes the tongue against the hard palate
of the mouth and introduces food into the esophagus
When we swallow, the epiglottis covers the trachea
preventing food from entering the windpipe. Solid food
takes approx. 9 seconds to enter the stomach. Liquids
take approx. 2 seconds
The esophagus is a tube of smooth muscle tissue approx.
12 inches long. Because it is constructed of smooth
muscle tissue, the esophagus contracts and relaxes
causing the food to move in a “wave like” motion called
peristalsis. Food now enters the stomach
The stomach is a collapsible saclike organ of smooth
muscle tissue. The shape of the stomach changes as
different stages of digestion take place
The stomach will begin to contract and relax, churning
the food. Mucous will be secreted to protect the stomach
from gastric juices (hydrochloric acid) which along with
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the muscular action of the stomach will further break
food down. Before it leaves the stomach, food has
become a thick liquid called chyme
The chyme now enters the first section of the small
intestine called the duodenum (the first 16 inches of the
20 feet of small intestine)
The pancreas deposits insulin into the chyme mixture to
break down blood sugar. The liver (the largest internal
organ) produces bile and stores it in the gall bladder.
Bile is introduced into the chime to break down lipids
(fats)
Lining the small intestine are millions of “finger like”
projections called villi which absorb nutrients from the
chime as it moves via peristalsis
Any unwanted or undigested food now enters the large
intestine (colon or bowel). It is approx. 5 feet in length
The large intestine prepares the feces for elimination via
the rectum (last section of the bowel). Complete
digestion takes approx. 24-48 hours
Disorders of the Digestive System
Ingestion- incomplete digestion accompanied by
stomach pain, heartburn (gastro-esophageal reflux
disease or GERD), nausea and or vomiting
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Diarrhea- when food moves too quickly through the
tract. Excess water in the colon produces a watery bowel
movement
Constipation- too little water in the bowel causes the
stool to become difficult to pass. Pressure to eliminate
the feces can cause the veins in the rectum to become
enlarged and painful (a condition called hemorrhoids)
Gallstones- hard, rock like substances from bile salts
that remain in the duct (connecting tube) from the liver
to the gall bladder or the bladder to the duodenum
Ulcer- open sore in the stomach or small intestine.
Digestive juices irritate the sore and cause pain. Diet
alterations may help but surgery may be required to
alleviate the problem
Diabetes- when the pancreas does not secrete any insulin
to break down blood sugar (Type I) or not enough (Type
II)
Hyperglycemia- too much sugar in the blood (need
insulin)
Hypoglycemia- too little sugar (need food/glucose)
The Urinary System
Urine- a fluid excretion of water, urea (nitrogenous
product), salt and uric acid
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Kidneys- two purplish brown organs located on either
side of the vertebral column. They filter blood and
collect urine
Each kidney contains collecting tubes (nephrons) which
are its functional unit
Urine is passed to the urinary bladder from the kidney
via the ureters (connecting tubes)
Urine leaves the body via the urethra
Kidney Stones- pebble like substances in the kidney or
urinary tract caused by urine remaining in the tract (salts
crystallize)
Dialysis- a machine that takes the place of the kidneys to
remove urine and filter blood