Download A View of Life - lombardoscience

Chapter 3
Digestive System and Nutrition
1
Outline
•
•
The Digestive Tract
– Mouth
– Pharynx
– Esophagus
– Stomach
– Small Intestine
– Large Intestine
– Accessory Organs
Nutrition
– Eating Disorders
2
The Digestive Tract
•
•
•
Roof of the mouth composed of two parts.
 Anterior hard palate.
 Posterior soft palate.
Tonsils help protect against infection.
Three pairs of salivary glands send juices
through ducts to the mouth.
– Saliva contains bicarbonate and salivary
amylase.
3
Digestive Tract
4
The Digestive Tract
•
•
Teeth used to chew food into pieces small
enough to swallow.
– Each tooth has two main divisions.
 Crown.
 Root.
Tongue mixes chewed food with saliva and
forms a bolus in preparation for swallowing.
5
Adult Teeth and Mouth
6
The Pharynx
•
The pharynx receives air from the nasal
cavities and food from the mouth.
– Swallowing is a reflex action that occurs in
the pharynx.
 Soft palate moves to close off
nasopharynx, and the trachea moves
under the epiglottis to cover the glottis.
7
Swallowing
8
The Esophagus
•
The esophagus is a muscular tube that
passes from the pharynx through the
thoracic cavity and diaphragm into the
abdominal cavity.
– Rhythmic peristalsis pushes food along
the digestive tract.
– Sphincters encircle tubes and act as
valves.
9
The Wall of the Digestive Tract
•
Layers.
– Mucosa - Mucus membrane layer.
– Submucosa - Submucosal layer.
– Muscularis - Smooth muscle layer.
– Serosa - Serous membrane layer.
10
Wall of the Digestive Tract
11
The Stomach
•
Stomach stores food and aids in digestion.
– Columnar epithelial lining contains gastric
pits leading into gastric glands.
 Produce gastric juice containing
enzyme pepsin.
– Walls of stomach have folds which help
churn and mix food and gastric juices.
 Chyme leaves the stomach and enters
the small intestine.
12
Stomach Anatomy
13
The Small Intestine
•
The small intestine is the primary site for
nutrient absorption.
– Receives bile from liver to emulsify fat.
– Walls contain villi which increase surface
area and thus absorptive capability.
 Nutrients are eventually transported into
the cardiovascular system and fats are
transported into the lymphatic system.
14
Small Intestine Anatomy
15
Regulation of Digestive Secretions
•
Secretion of digestive juices is promoted by
the nervous system and by hormones.
– Hormones are produced by one set of
cells and affect a different set of cells.
 Gastrin.
 Gastric inhibitory peptide (GIP).
 Secretin.
 Cholecystokinin (CCK).
16
Hormonal Control of Digestive Secretions
17
The Large Intestine
•
•
The large intestine absorbs water, salts, and some
vitamins, and stores fecal material.
Cecum is blind end of large intestine.
– Colon.
 Ascending.
 Transverse.
 Descending.
 Sigmoid.
– Rectum.
– Anus.
18
The Large Intestine
•
•
•
Polyps are small growths arising from the
epithelial lining.
– May increase likelihood of colon cancer.
 Can be removed surgically.
Diarrhea is caused by infection of the lower
intestinal tract and nervous stimulation, and
results in increased peristalysis.
Constipation can be caused by a lack of
water and fiber, and leads to dry, hard
feces.
19
Three Accessory Organs
•
•
•
The pancreas secretes insulin and glucagon
that regulate blood glucose levels.
The liver maintains homeostasis by
maintaining blood glucose levels, producing
bile, and detoxifying blood.
– Disorders.
 Jaundice.
 Cirrhosis.
The gallbaldder stores excess bile.
20
Digestive Enzymes
•
Digestive enzymes are hydrolytic enzymes
that break down substances into nutrient
molecules.
– Glucose and amino acids are absorbed
into blood capillaries of the villi.
– Fatty acids and glycerol reform within
epithelial cells and enter lacteals as
lipoprotein droplets.
21
Nutrition
•
The body requires three major classes of
macronutrients to supply energy and
optimum cellular metabolism.
– Carbohydrates.
– Protein.
– Fat.
22
Food Guide Pyramid
23
Carbohydrates
•
Carbohydrates are digested to simple
sugars, which are, or can be converted to,
glucose.
– Quickest, most readily absorbed source of
energy for the body.
– Complex carbohydrates should make up
the bulk of the diet.
24
Proteins
•
Adequate protein formation requires twenty
different amino acids, including eight
essential amino acids.
– Body is unable to produce essential
amino acids.
– Amino acids are not stored in the body,
and thus a daily supply is needed.
25
Lipids
•
Fat and cholesterol are both lipids.
– Intake of fat increases weight gain, and
increases the risk of cardiovascular
disease and cancer.
 Plaque deposits contain saturated fats
and cholesterol.
 For optimal cardiovascular health, less
than 30% of calories should come from
fat and less than 10% from saturated
fat.
26
Vitamins and Antioxidants
•
Vitamins are inorganic compounds used by
the body for metabolic purposes, but cannot
be produced in adequate quantities.
– Antioxidants are vitamins that defend the
body against free radicals.
 Molecules that carry an extra electron.
27
Minerals
•
The body also requires minerals.
– Macrominerals are present at a minimal
level of 5 grams each.
 Calcium, Potassium, Sodium,
Magnesium, Phosphorus, Sulfur,
Chloride.
– Microminerals are present at levels under
5 grams each.
 Iodine, Copper, Mangenese, Zinc, Iron.
28
Calcium and Sodium
•
•
Calcium counteracts osteoporosis and
generally strengthens bones.
Sodium helps maintain osmotic balance, but
too much sodium can intensify hypertension.
– How do you reduce sodium intake?
29
Eating Disorders
•
Obesity.
– Most often defined as body weight 20% or
more above ideal weight.
 Most likely caused by a combination of
hormonal, metabolic, and social factors.
 Increases risk of heart disease.
30
Eating Disorders
•
•
Bulimia Nervosa.
– Habit of eating to excess and then purging
by artificial means.
 Alters blood composition leading to
heart rhythm problems and kidney
damage.
Anorexia Nervosa.
– Morbid fear of gaining weight.
 Self-induced starvation.
31
Review
•
•
The Digestive Tract
– Mouth
– Pharynx
– Esophagus
– Stomach
– Small Intestine
– Large Intestine
– Accessory Organs
Nutrition
32
33