Transcript Chapter 14 - Digestive

Chapter 14
The Digestive System and Body
Metabolism
The Digestive system takes food,
breaks it down into nutrient
molecules and absorbs them into
the blood stream and then rids
the body of indigestible remains
Figure 14.1
Organs of the Digestive System (DS)
1. Alimentary Canal or
Gastrointestinal tract (GI
tract)
• Digests and absorbs
• Continuous muscular hollow
tube
A. Mouth or Oral Cavity
• Food enters – masticated
(chewed)
• Tonsils – located at the base of
the tongue
• Tongue – mixes food with saliva
and initiates swallowing – taste
receptors
Figure 14.2a
Figure 14.2b
B.Pharynx (air goes through too)
Peristalsis – contraction of
muscles that moves food involuntary
C. Esophagus (10 in)
The walls of the esophagus to
the intestines – four basic
tissue layers
Figure 14.3
D.Stomach
C shaped
10 inches long
Full – 4 L or 1 gallon
Storage tank and site of food
breakdown
Gastric pits – release gastric
juice
Chyme – digested food – like
heavy cream
Figure 14.4a
Figure 14.4c
E. Small Intestine
Major digestive organ
2 meters or 6 feet
Mesentery holds in place
3 subdivisions
a.Duodenum
b.Jejenum
c.Ileum
Chemical digestion occurs in the
stomach
Bile (fats) from liver
Pancreatin from pancreas
(contains 4 enzymes)
Almost all food absorption occurs
in the small intestine
Villi – finger-like projections that
increase the surface area for
absoprtion
F. Large Intestine
Larger diameter than Small
Intestine
1.5 m or 5 ft
Major Functions
1. absorbing water from
undigested food
2. eliminate residues as feces
2. Accessory Digestive Organs
Assist the process of digestive
breakdown
A. Pancreas
 Produces enzymes for food breakdown
 Located under the stomach
B. Liver and Gallbladder
Liver
Largest organ
Four Lobes
Very Important Organ
Produces Bile
Bile
Yellow to green watery solution
Not an enzyme
Bile salts emulsify (break down)
fats
Gallbladder
Small thin walled green sac –
attached to liver
Stores bile
Gallstones – bile stored too long –
cholesterol crystallizes
C. Salivary Glands
Three pairs empty into the mouth
Product – saliva
Bolus – mass of food binded by
mucous
Salivary amylase – breaks down
starch
D. Teeth
Masticate or chew
Permanent full set – 32 teeth
Impacted – tooth remains
embedded in the jaw
Figure 14.9 (1 of 2)
Figure 14.9 (2 of 2)
Tooth
Two regions – crown and root
Enamel – hardest substance in
the body
Pulp – supplies nutrients to the
tooth tissues
Figure 14.10
Functions of the Digestive System
Major Functions Digestion and
Absorption
Six Processes of the GI Tract
1. Ingestion – into the mouth
2. Propulsion – movement from
organ to organ (peristalsis)
3. Food Breakdown – Mechanical
Digestion
Mixing in the mouth
Churning in the stomach
4. Food Breakdown – Chemical
Digestion (breaking bonds)
Sequence of steps where large
food molecules are broken into
small ones
5. Absorption
Movement of digested end
products from the GI tract to
the blood
Occurs in the Small intestines
6. Defecation - elimination
Activities in the Mouth, Pharynx, and
Esophagus
Food Ingestion and Breakdown
Chewing – physical breakdown
Mix with saliva – chemical
breakdown
Pharynx and esophagus passageways
Food Propulsion – Swallowing and Peristalsis
Two Phases
Buccal Phase – tongue forces
food into the pharynx
2. Pharyngeal-Esophageal Phase
1.
 involuntary
 Coughing – forcing food out of
the lungs
 Gravity is not involved
Activities of the Stomach
Food Breakdown
Gastric juice released
HCl makes stomach acid –
pH of 2
Ulcers – stomach digests itself
Heartburn – stomach acid goes
into the esophagus
Pepsin – digestive enzyme –
activated by acid – digests
protein
Only protein digestion begins in
the stomach
Exception – Alcohol and
Aspirin absorb through
stomach walls
Stomach fill – mechanical
digestion continues – smashing
the food
Food Propulsion
3 mL of chyme squirted into
small intestine – stops when the
small intestine in is full
4-6 hours for stomach to empty
after a meal
Activities of the Small Intestine
Food breakdown and absorption
Food only partially digested
Carbohydrate and protein started
– no fats
3-6 hours in small intestines
Pancreas secretes enzymes to
the small intestines.
1. Pancreatic amylase – starch
2. Trypsin – proteins
3. Lipases – fats
4. Nucleases – nucleic acids
Pancreatic Juice – Bicarbonate –
pH of 8 – made of 4 enzymes
Liver secretes Bile
 Breakdown fats and helps them be
absorbed
 Fat soluble vitamins (K, A, D)
 Food absorbed a long the way
End: Water, undigested food,
bacteria
Activities of the Large Intestine
Food breakdown and absorption
12-24 hours in Large Intestine
Bacteria use some of the
remaining nutrients and release
gas - methane (CH4) and H2SO4
500mL of gas produced a day
Bacteria also make vitamins (K
& B)
Absorption – water, ions and
vitamins
Propulsion of the Residue and Defecation
Peristalsis and mass movements
cause defecation
Typically occur after eating
Diarrhea – not enough water
absorbed
Constipation – too much water
absorbed
Figure 14.11
Nutrition and Metabolism
Energy value of food is measure
in kilocalories (kcal)
Nutrition
Nutrient – substance in food that
is used by the body to promote
normal growth, maintenance and
repair
The Six Nutrients
1.Carbohydrates – sugars and
starch mostly from plants –
cellulose – fiber
2.Lipids – Fats, oil and waxes
Saturated fats – animals, meat
and dairy
Unsaturated – plants, seeds,
nuts, veggie oils
3. Proteins – (made of amino acids
– AA’s) – animal products – Eggs,
milk and meat
Vitamins – organic nutrients
needed in small amounts –
coenzymes
5. Minerals – Ca, P, K, S, Na, Cl, Mg
also needs trace amounts of
others mineral rich food –
veggies, legumes, milk and some
meat
6. Water
4.
Organic Compounds
Monomers – one unit in a macromolecule
Polymer – many monmers
Nucleic Acids
DNA and RNA
Monomers – nucleic acids
Lipids
Three fatty acids and a glycerol
Fats, oils, and waxes
Carbohydrates
Sugars
Three Types
1. Monosaccharides
2. Disaccharides
3. Polysaccharides
Examples –
Glycogen – animals
Starch – plants
Glucose
Proteins
 Monomers – amino acids – 20
 AA held together by peptide

bonds
Dipeptide – 2 amino acids
Organic
Compound
Test
Positive
Reagent Test
Examples
Carbohydrate Benedicts Orange
Sugars, milk,
Apple juice,
glucose
Carb. –
Starch
Iodine
Black
Potato,
Bread
Protein
Biuret
Purple
Meat,
enzymes
Lipids
Brown
paper
Grease
spot
Fats, oils,
Waxes
Metabolism
All the chemical reactions that
are necessary to maintain life
1. Catabolism – breaking down
2. Anabolism – building larger
molecules
How Food Stuffs are treated:
Carbohydrates – Make ATP
Fats – Cell membrane, Insulation,
Fuel when no carbohydrates
Proteins – hoarded – building cells
Body Energy Balance
When energy intake and energy
outflow are balanced, body
weight remains stable.
Metabolic Rate and Heat Production
Kilocalorie (kcal) – unit used to
measure energy value of foods
Carbohydrates and proteins = 4
kcal/g
Fats = 9 kcal/g
Basal Metabolic Rate (BMR)
Amount of
heat produced by the
body when at rest
Just what is needed for essential
life activities
154 lb adult = 60-72 kcal/hr
BMR – influenced by surface area
and gender
Thyroxine produced by the
thyroid determines BMR
Hyperthyroidism – lose weight
Hypothyroidism – gain weight
Total Metabolic Rate
Total amount of kcal the body
must consume to fuel ongoing
activities
Muscle work – causes biggest
increase
Body Temperature Regulation
60% of
energy from food
breakdown is lost as heat
The blood moves the heat to all
the tissues
Heat Promoting Mechanisms
Vasoconstriciting – blood is not
sent to the skin
Shivering – muscle movement –
heat
Frostbite – when oxygen does not
go to the skin and cells begin to
die
Hypothermia – low body
temperature, vital signs,
decrease drowsy, comfortable,
death
The End