LEC
06A
Mammalogy
(Spring 2015 Althoff)
Mammalian Digestive System BASICS
Maintenance Systems
• __________________—various organs along the
digestive tract (from teeth to large intestine)
A) receives food
B) digests & absorbs nutrients
C) excretes undigestible parts (feces)
• __________________—lungs
A) takes in O2 from “outside” environment
B) takes out CO2 from “inside” environment
• __________________—kidneys, bladder, & tubes
A) rids blood of metabolic wastes
B) helps regulate fluid level & chemical
content of blood
Food - IN
Maintenance
CO2 OUT, O2 IN
Control
Systems
DIGESTIVE RESPIRATORY URINARY
FUNCTIONS of the Digestive System
_____________ OUT
______________OUT
Breakdown the food into small molecules
_________________ = process of breaking
Breakdown the food that we eat into
__________________
________ those molecules into the body
Eliminate __________________ waste
down food into simple molecules
Two types:
____________ = chewing, physical
breakdown
____________ = digestive enzymes
(catabolism)
Foodstuffs broken down into simple molecules:
Proteins  amino acids
Carbohydrates  monosaccharides
Lipids  glycerol and fatty acids
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ABSORB the simple molecules
_______ doesn’t really “enter” the body until
it is absorbed
Must pass through:
_________________  blood stream
Unfortunately, we do not ___________ the
process of absorption….animals designed to
maximize extraction of nutrients from
“resources” ingested.
This leads to the issue of gaining weight if we
overeat.
ELIMINATE non-digestible waste
Any compound of food (emphasis “food”) we
_______________ will be eliminated.
Ex. for humans: Cellulose (found in cell
walls of plants)
_______
in normal, functioning human being,
contains no undigestible material…so very little
waste.
Organs of the
DIGESTIVE System
Organs of the
DIGESTIVE System
•
•
•
•
•
•
•
Mouth
Pharynx-throat
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum/Anus
•
•
•
•
•
•
•
Mouth
Pharynx-throat
Esophagus
Stomach
Small Intestine
Large Intestine
Rectum/Anus
•
•
•
•
Salivary glands
Pancreas
Liver
Gall bladder
•
•
•
___________organs •
Salivary glands
Pancreas
Liver
Gall bladder
As each organ and/or “stop” is examined,
think……
1) FUNCTION--what is it
2) DIGESTION—does it occur here?
(i.e., mechanical or chemical)
3) ABSORPTION—does it occur here?
(are amino acids, fatty acids & glycerol,
and simple sugars truly “entering” the
body?)
Mouth
• Oral cavity that receives food
• Tastebuds so we can taste food
• Salivary glands secrete saliva
- moistens food to make easier to swallow
- starts digestion of starches (pH ~7.0),
some sugars
• ____ ABSORPTION, small amt. of digestion
• Some bacteria destroyed
• Mastication of food— __________________
for digestive juices to work on
2
MASTICATION:
“chewing” differences
MASTICATION:
DIFFERENT TEETH
FOR DIFFERENT DIETS
Pharynx 
• Swallowing, no
voluntary control
• Food now called
“BOLUS”
___ absorption,
___ digestion
1
Mandibular ________
and ________ groups
HERBIVORES: flat premolars & molars
HUMANS: variety
A
CARNIVORES: killing (canines),
shearing (premolars & molars
Esophagus
• Tube from pharynx to
stomach
• Food moves by
PERISTALIS …smooth
mucsle contractions
• Passes lower esophageal
sphincter into stomach:
a) prevents backup
b) acidic gastric juices
backup…heartburn
results because
lining irritated
Stomach…continued
• Muscus secreted
protects stomach lining
from pH of 2.0 – ulcers
result if insufficient
• HCl breakdowns down
connective tissue
• Pepsin enzyme starts
protein digestion
• ____________, _____
________ (alcohol &
some vitamins
• Bolus chyme (vomit)
as it leaves stomach
Position of the condyle
(arrow) relative to the plane
of teeth differs between
carnivores (A) and
herbivores (B). Thus, the
___________ muscles (1)
are primary group of
chewing muscles for
carnivores, whereas the
___________ (2) are the
primary group for herbivores
B
2
Fig. 4-193 p64 FDVMK
Stomach
• J-Shaped organ
• Functions:
1) store meal for
2 hours
2) small amt. of
protein digestion
3) _____ bacteria
in bolus “if it can
get to it”
• pH of 2.0 with HCl
added
Ruminants: 4 chambered stomach
3
Small Intestine (SI)
• 9-10 ft. in adults
• Functions:
__________ &
__________
“big time”
• Walls of SI lined
with _________ –
tremendous amt.
of surface area
Microvilli : area of absorption, link to
transport systems (cardiovascular & lymphatic capillaries )
Individual cells have ___________
Small Intestine (SI)
• _____ chemical digestion:
-pancreatic juices
breaks down
proteins & carbs.
Buffers chyme to
pH 7.0 (from 2.0)
-bile from liver and
gall bladder.
Emulsify fats
Lipase—break
down triglycerides
Different diets, different SI designs
HIGH
in protein
(meat)
CARNIVORES
Small Intestine (SI)
• ______ absorption:
-amino acids
-simple sugars
-fatty acids…..
all to the liver via
the bloodstream
Large Intestine (LI)
• 4.5-5 ft in adults
• After first few inches,
considered colon
• Functions:
-_____ digestion
(some vitamins--in cecum)
LOW
in protein
(vegetation)
-_____ absorption of
water
HERBIVORES
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Large Intestine (LI)…con’t
• Diarrhea—LI doesn’t get enough time to do its
job…that is to remove water from wastes. A
good “thing” if overload of bacteria present
• Constipation—LI tract not moving things
through at regular pace, more water removed
than normal, feces hard
• POLYPS– found here, in epithelial tissue….
caused by cancer
Auxillary Organs: __ DIGESTION, __ ABSORPTION
• LIVER— function here is producer of bile.
Contains components of dead red blood cells,
giving feces color. Bile emulsifies fat. Removes
toxic substances from foods upon arrival from
blood stream. Stores excess nutrients from
blood (sugar & vitamins). Cannot live without.
• GALL BLADDER— stores bile between meals.
Secretes bile into SI. Can live without. Gall
stones form when cholestrol content of bile
comes out of solution (crytallizes)…oh my!
• PANCREAS– secretes pancreatic juices which
contain enzymes (i.e., lactase is an example)
and buffering solution (raises pH). Can not live
without
SUMMARY - Digestion
•
•
•
•
•
•
Mouth
Phyarnx
Esophagus
Stomach
Small Intest.
Large Intest.
• Pancreas
• Liver
• Gall Bladder
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