Transcript Ch15-Digestion and Nutrition

Chapter 15: Digestion & Nutrition
I.
Introduction to Digestion
A.
Digestion refers to the mechanical &
chemical breakdown of foods so that
nutrients can be absorbed by cells
B.
The digestive system includes:
1.
2.
Pg. 413
alimentary canal (AC)
– 9 meter long
muscular tube from
mouth to anus
accessory organs –
empty into the AC
Pg. 412
C.
Movements in the AC: mixing & propelling
1.
Mixing occurs when smooth muscles
contract rhythmically in small sections
of the AC
Pg 415
2.
Propelling refers to peristalsis caused
by contraction behind a mass of food
as relaxation allows the mass to enter
the next segment of the AC
II.
Organs of the Digestive System
A.
Mouth - first portion of AC; mechanical
digestion by mastication (chewing) begins
1.
Palate – forms roof of oral cavity:
 anterior hard palate –
speech sounds, pushes
food to pharynx
 posterior soft palate –
with uvula, it closes off
nasal cavity when
swallowing
Pg 415
2.
Teeth
a.
2 sets of teeth develop in sockets
within the mandible & maxilla
b.
20 primary teeth are shed in
the order they appeared and are
replaced by 32 secondary teeth
Pg 416
c.
d.
Through the actions of chewing,
teeth break food into smaller
pieces, beginning mechanical
digestion
Teeth are adapted to handle food
in different ways: incisors,
cuspids, bicuspids, & molars
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Pg 417
e.
Each tooth
consists of a
crown & a root,
and is made of
enamel, dentin,
pulp, cementum,
nerves, & blood
vessels
f.
A tooth is held
tight in its socket
by a periodontal
ligament
3.
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Salivary Glands
a.
these secrete saliva, which:
 moistens & dissolves food
particles
 binds them together
 allows tasting
 helps to cleanse mouth & teeth
 begins carbohydrate digestion
b.
saliva contains enzyme amylase
used to breakdown carbs, and
mucous cells that produce
lubricating and binding mucus
c.
Major Salivary Glands
 parotid glands secrete a clear,
watery fluid rich in amylase
 submandibular glands &
sublingual glands secrete a
viscous (thick) fluid
B.
Pharynx
1.
lies behind mouth
2.
connects nasal & oral
cavities with the
larynx (breathing)
and esophagus (food)
Pg 416
C.
Esophagus
1.
muscular tube leading to stomach
2.
produces mucus (moisture, lubrication)
3.
lower esophageal sphincter prevents
regurgitation of stomach contents
D.
Stomach: J-shaped muscular organ
1.
mixes food with digestive juices (HCl)
2.
propels food to small intestine
3.
pyloric sphincter controls the release of
food from stomach into small intestine
4.
can only absorb small quantities of
water and certain salts, alcohol, and
some lipid-soluble drugs
5.
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4 regions:
cardiac
fundic
body
pyloric
E.
Pancreas
1.
empties pancreatic juice into the small
intestine through the pancreatic duct
2.
pancreatic juice contains enzymes
that digest carbohydrates, fats,
proteins, and nucleic acids (DNA, RNA)
Pg 424
F.
Liver
1.
2.
3.
4.
Pg 425
a large, reddish-brown organ, located
in the upper right quadrant of the
abdominal cavity
metabolizes carbohydrates, lipids, &
proteins
filters blood, removing damaged red
blood cells, foreign substances, toxins
secretes bile, which performs lipid
emulsification (lipids are broken down
into smaller droplets to ↑ surface area
for faster digestion)
G.
Pg 425
Gall
1.
2.
3.
Bladder
pear-shaped green sac under the liver
stores bile for later release
gall stones may form from:
a.
insufficient bile salts
b.
excessive cholesterol (stones)
H.
Pg 430
2.
3.
4.
Small Intestine
1.
10 feet long with
3 parts:
a.
duodenum
(10-12 in)
b.
jejunum (3 ft)
c.
ileum (6 ft)
receives secretions from pancreas & liver
completes digestion &
absorption of nutrients
using villi
transports indigestible waste
to the large intestine
Pg 431
I.
Large Intestine
1.
4 Parts:
a.
b.
c.
d.
Pg 435
cecum – pouch
colon –
 ascending
 transverse
 descending
 sigmoid
rectum
anal canal
2.
Functions:
a.
NO digestion or absorption of
nutrients, but it does secrete
mucus
b.
Absorbs electrolytes (Na+, Cl-,
K+) and water
c.
Contains bacteria that make
vitamins and use cellulose
(material from plant cell walls)
d.
forms & stores feces
 composed of undigested
material, little water, few
electrolytes, mucus, & bacteria
 both the color & odor of feces
is due to the action of bacteria
3.
Movements of the Large Intestine
a.
b.
Peristalsis happens only 2-3
times per day
Defecation is stimulated by a
reflex that forces feces into the
rectum where they can be
expelled
Pg 436
4.
The anal canal opens to
the outside as the anus
& is guarded by 2 muscles:
a.
b.
internal anal sphincter (involuntary)
external anal sphincter (voluntary)
NUTRITION
I.
Nutrition and Nutrients
A.
Nutrition is the study of nutrients & how the
body utilizes them
B.
Nutrients are chemicals supplied from the
environment that an organism requires for
survival:
1.
Carbohydrates
Macro
2.
Lipids
Nutrients
3.
Proteins
4.
Vitamins
Micro
Nutrients
5.
Minerals
C.
Carbohydrates, Proteins, & Lipids contain
Calories
1.
1 calorie = the amount of energy
needed to raise the temp of 1 gram of
water by 1o Celsius
2.
1 Calorie = a kilocalorie used to
measure food energy; 1000x greater
than a calorie
3.
Carbs & Proteins = 4 Calories/gram
Lipids = 9 Calories/gram
II.
Carbohydrates
A.
Carbohydrates are used for sources of
energy in the diet (125-175 grams/day to
avoid protein breakdown)
B.
Forms:
1.
starch from grains & some vegetables
2.
glycogen from meat
3.
disaccharides – sugars from cane
sugar, beet sugar, & molasses
4.
monosaccharides – sugars from honey
& fruit
5.
cellulose – found in plant cell walls
 bacteria can digest some, but most
provides bulk (fiber), helping food
move through the intestines
C.
Carbohydrate Utilization
1.
Starches & Glycogen are broken down
into monosaccharides: fructose,
galactose, & glucose
2.
Liver enzymes further convert fructose
& galactose into glucose
3.
Excess glucose is stored as
 glycogen in the liver & muscles (1st)
 fat in adipose tissue (2nd)
4.
Neurons need a continuous supply of
glucose to survive; if glucose is scarce,
amino acids (from proteins) may be
converted to glucose
III. Lipids
A.
B.
Lipids supply energy & make up membranes
1.
3 kinds: fats, phospholipids, cholesterol
2.
No more than 30% of your daily
calories should be lipids
Dietary Lipids are triglycerides, found in
plant- & animal-based foods
1.
Saturated fats: animal origin (meat,
eggs, milk, lard); palm & coconut oils;
cholesterol
2.
Unsaturated fats: plant origin
(seeds, nuts, plant oils)
 Monounsaturated fats: olive, peanut,
& canola oils are the healthiest
IV.
Proteins
A.
Proteins are polymers of amino acids & carry
out important cellular functions:
1.
enzymes control metabolism
2.
hormones regulate processes
3.
antibodies & clotting factors for blood
4.
actin & myosin in muscle
5.
keratin in skin & hair
 potential sources of energy too
B.
Adult cells can make 12 required amino acids
1.
8 can’t be = essential amino acids
2.
All 20 must be present at the same
time for proper growth & tissue repair
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C.
D.
Protein Sources
1.
Animal protein sources are complete
proteins, b/c they contain all 8
essential amino acids
2.
Plant protein sources are missing 1+
essential amino acids making them
incomplete proteins
 Vegetarians should consume in
combinations
Daily Protein Requirements
1.
0.8 grams per kg body weight
2.
Body weight in pounds ÷ 2
3.
60-150 grams
 Increase by 20-30g if pregnant or
nursing
V.
Vitamins & Minerals – make reactions possible
that extract energy from carbs, lipids, & proteins
A.
Vitamins are required in small amounts,
and are not produced enough by cells
 water-soluble – B’s, C
fat-soluble - A, D, E, K →
B.
Minerals are derived from the soil & essential in
human metabolism (Ca, K, Fe, I, Cl etc.)
VI.
Adequate Diets
A.
An adequate diet providess sufficient energy
(calories) & nutrients to support optimal
growth and to maintain and repair body
tissues
B.
Individual requirements for nutrients vary
greatly with: age, sex, growth rate, physical
activity, stress level, and genetic &
environmental factors
C.
Malnutrition – poor nutrition
1.
undernutrition: lack of food, poor
quality food, inability to use nutrients
2.
overnutrition: overeating or taking too
many vitamin supplements
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