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NOTES: CH 41 – Animal
Nutrition & Digestion
NUTRITION
*Nutrition is the study of nutrients and how
the body utilizes them!
*ESSENTIAL NUTRIENTS: nutrients that
human cells cannot synthesize (i.e. certain
amino acids)
 CARBOHYDRATES
● Carbohydrate sources:
-starch
-disaccharides
-glycogen
-monosaccharides
-cellulose (not digested, but provides
FIBER)
 CARBOHYDRATES
● How are carbohydrates used?
-they are broken down (oxidized) which
releases energy from glucose
-excess glucose is stored as glycogen or
converted to fat
-most carbohydrates supply ENERGY
 CARBOHYDRATES
● Carbohydrate requirements:
-recommended that carbs make up 60%
of a person’s diet
-physically active individuals require more
fuel than sedentary ones
-cellulose is a complex carbohydrate that
humans cannot digest; provides FIBER
 LIPIDS
● Lipid sources:
-plant oils (unsaturated): corn oil, olive oil
-animal products (saturated): butter, lard
 LIPIDS
● How are lipids used?
-the liver and adipose (fat) tissue work
together to regulate triglyceride
metabolism
-lipids supply energy (long-term)
-lipids are used to build cell structures
-cholesterol is present in membranes and
is also used to synthesize certain
hormones
 LIPIDS
● Lipid requirements:
-recommended that not more than 30%
of diet is fat intake
-saturated fats should comprise no more
than 10% of diet
-must be sufficient to carry fat-soluble
vitamins
 PROTEINS
● Protein sources
-meats, fish, poultry,
dairy products, cereals, legumes
-complete proteins have adequate
amounts of all essential amino acids
-incomplete proteins lack adequate
amounts of one or more essential amino
acids
 PROTEINS
● How are proteins used?
-structural (collagen, elastin, keratin)
-enzymes (lactase, lipase, amylase) that control
metabolic reactions
-antibodies (fight infection)
-messengers (hormones)
-transport (hemoglobin; cell membrane proteins)
-may provide energy
 PROTEINS
● Protein requirements:
-should make up about 10% of diet
-must supply essential amino acids
-pregnant and nursing women should
increase their protein intake
 VITAMINS
(organic compounds required in small
amounts)
 VITAMINS
● Fat-soluble vitamins:
-dissolve in (and stored in) fat
-include vitamins A, D, E, and K
-resist the effects of heat (therefore
cooking does not destroy them)
 VITAMINS
● Water-soluble vitamins:
-dissolve in water
-include the B vitamins and
vitamin C
-cooking or processing food
destroys some water-soluble
vitamins
 MINERALS
(elements, other than carbon, needed in
small amounts for normal metabolism)
 MINERALS
● Characteristics:
-most are stored in the bones and teeth
-can be incorporated into organic
molecules (parts of enzymes, vitamins,
etc.)
-can be in the form of free ions (example:
Ca2+ ions in muscle cells)
 MINERALS
● Mineral functions include:
-structural materials
-can function as part of enzymes
-play vital roles in metabolic processes
-maintaining pH of body fluids
 MINERALS
● Examples of Major Minerals:
-calcium
(Ca)
-chlorine (Cl)
-phosphorus (P)
-magnesium (Mg)
-potassium (K)
-sulfur
(S)
-sodium
(Na)
 MINERALS
● Examples of Trace Elements:
-iron
(Fe)
-cobalt (Co)
-manganese (Mn)
-zinc
(Zn)
-copper
(Cu)
-fluorine (F)
-iodine
(I)
-selenium (Se)
 ADEQUATE DIETS
● an adequate diet provides sufficient:
Energy
Essential nutrients
*essential nutrients are
necessary to support
optimal growth,
maintenance, and tissue
repair
● malnutrition is poor
nutrition due to:
-Lack of food
-Failure to make the
best use of available
food
MALNUTRITION
*Malnutrition may be due to:
UNDERNUTRITION
(deficiency diseases)
OVERNUTRITION
(excess diseases)
Food processing occurs in 4
stages:
1) Ingestion (act of eating)
2) Digestion (into smaller molecules)
3) Absorption (of nutrients)
4) Elimination (of wastes)
DIGESTION…
Digestion is the process of
mechanically and chemically
breaking down foods and
absorbing the breakdown products.
The digestive system consists of an
alimentary canal and several accessory
organs.
Alimentary canal includes:
● mouth
● pharynx
● esophagus
● stomach
● small intestine
● large intestine
● rectum
● anus
Accessory organs are:
● salivary glands
● liver
● gallbladder
● pancreas
THE ALIMENTARY CANAL
*The alimentary
canal is a muscular
tube that passes
through the body’s
ventral cavity.
Different regions
carry out different
functions.
Movements of the tube:
MIXING MOVEMENTS
and
PROPELLING MOVEMENTS
(include a wavelike motion
called PERISTALSIS)
MOUTH (Oral Cavity)
*receives food and
begins digestion
 Tongue:
-rough projections (PAPILLAE)
on surface of tongue provide friction to
handle food
-papillae also contain TASTE BUDS
MOUTH (Oral Cavity)
 TEETH: teeth are used to mechanically
break food into smaller pieces
(this increases the surface area
of food allowing digestive
enzymes to react more
effectively with the food
molecules)
SALIVARY GLANDS
*3 pairs of salivary glands
secrete SALIVA, which
moistens food, helps
bind food particles,
begins chemical
digestion of
carbohydrates, makes
taste possible, and helps
cleanse the mouth.
SALIVARY GLANDS
 secrete a watery fluid that contains the
digestive enzyme AMYLASE (starts to
break down starch and glycogen into
smaller disaccharides)
 secrete a thick fluid called MUCUS,
which binds food particles and lubricates
during swallowing
Pharynx / Throat
● leads to esophagus and trachea
● when food is swallowed, trachea is
blocked by EPIGLOTTIS (cartilage flap)
ESOPHAGUS
ESOPHAGUS: a food passageway
from the pharynx to the stomach
-at distal end, circular smooth muscle fibers thicken
and close the entrance to the stomach (prevents
regurgitation);
-if some of the acidic stomach
contents are regurgitated
(reflux) into the esophagus,
may cause HEARTBURN
STOMACH
*the stomach receives food, mixes it with
gastric juice, initiates protein digestion,
carries on a limited amount of absorption,
and moves food into the small intestine.
STOMACH
 Structure / Parts:
-has a capacity of about 1 L
-separated from the small intestine by a
powerful circular muscle: PYLORIC
SPHINCTER
PYLORIC SPHINCTER
STOMACH
 Gastric secretions include:
● mucus
● digestive enzymes
● hydrochloric acid (HCl)
*together, these secretions form
GASTRIC JUICE
STOMACH
 PEPSIN: most important digestive enzyme
in gastric juice
-secreted in an inactive form: PEPSINOGEN
-when it comes into
contact with
hydrochloric acid,
it becomes the
active PEPSIN
(a protease)
STOMACH
*a layer of thick mucus is produced by
cells in the stomach’s inner lining…this
protective coating prevents the
stomach from digesting itself.
STOMACH
 Mixing and emptying actions:
- CHYME = a mixture
of food particles and
gastric juice produced by
mixing
-chyme is emptied into the small intestine
where chemical digestion continues
PANCREAS
Structure of the pancreas:
● the pancreas produces PANCREATIC
JUICE that is then secreted into the
PANCREATIC DUCT, which leads to the
DUODENUM (first portion of the small
intestine)
PANCREAS
Pancreatic juice contains enzymes that
split or break down:
● carbohydrates
● fats / lipids
● proteins
● nucleic acids
*pancreatic juice also has a high
bicarbonate ion concentration that helps
neutralize chyme and causes intestinal
contents to be alkaline (basic).
Hormones regulate / control
pancreatic secretion:
● as chyme enters the duodenum, the duodenal
mucous membrane secretes the hormone
SECRETIN
 stimulates secretion of pancreatic juice
that has a high conc. of bicarbonate ions
● proteins and fats in the chyme within the
duodenum cause the duodenal membrane to
release the hormone CHOLECYSTOKININ!

 stimulates secretion of pancreatic juice
that has a high conc. of digestive enzymes
CHOLECYSTOKININ (CCK)
word #3 on my list!!!...let’s see, so far we have:
1) Okazaki fragments
2) plasmodesmata
3) cholecystokinin
4) acetylcholinesterase
5) ???
6) rubisco
7) oxaloacetate
8) Islets of Langerhans
9) Batesian mimicry
10) nodes of Ranvier
LIVER
Structure of the liver:
● The liver is divided into a
large RIGHT LOBE and a
smaller LEFT LOBE.
Liver functions
include:
● metabolizing
carbohydrates, lipids, and
proteins;
● storage of some
substances;
● filtering the blood;
● destroying toxins;
● secreting bile.
**Bile is the only liver
secretion that directly
affects DIGESTION!!
Composition of BILE:
● BILE contains:
*bile salts
bile pigments
cholesterol
electrolytes
*only the BILE SALTS have digestive
functions!
GALLBLADDER
 the gallbladder stores bile between meals
and releases bile into the small intestine via
the CYSTIC DUCT and COMMON BILE
DUCT
 cholesterol in the bile may form solid
GALLSTONES which could block the ducts
Functions of Bile Salts:
● emulsify fats (surround and break them
down into small droplets)
● aid in the absorption of fatty acids,
cholesterol, and certain vitamins
SMALL INTESTINE
*the small intestine receives secretions from
the pancreas and liver, completes nutrient
digestion, absorbs the products of
digestion, and transports the residues to
the large intestine.
SMALL INTESTINE
● the small intestine consists of the:
DUODENUM (first 25 cm)
JEJUNUM
ILEUM
Structure of the small intestine wall:
● the wall is lined with VILLI that increase
the surface area and aid in mixing and
absorption
(these, in turn, are covered with smaller
extensions called MICROVILLI)
● intestinal glands are located between the
villi
Secretions of the small intestine:
● secretions include: MUCUS and
DIGESTIVE ENZYMES
● digestive enzymes split molecules of
SUGARS, PROTEINS, and FATS into
simpler forms
*these secretions are released when
stimulated by gastric juice, chyme, and
stretching of the small intestine’s wall
Absorption in the small intestine:
● the intestinal villi absorb
the products of carbohydrate,
protein, and fat digestion
● the villi also absorb
electrolytes and water
**if food is rushed through the small
intestine, not enough absorption of
these things takes place and the
result is DIARRHEA.
LARGE INTESTINE
*the large intestine reabsorbs water and
electrolytes, and forms and stores FECES
LARGE INTESTINE
● the large intestine
consists of the:
-CECUM
-COLON
(ASCENDING, TRANSVERSE,
DESCENDING, and
SIGMOID COLON)
-RECTUM
-ANAL CANAL
Functions of the Large Intestine:
● has little or no digestive function
● secretes mucus
● absorbs water and electrolytes
● forms and stores FECES
 FECES consist of:
-Water
-Electrolytes
-Bacteria
-Undigested material
-Mucus