Download NOTES: Introduction to Histology (Ch 5)

NOTES: CH 41 – Animal Nutrition and Digestion
*Nutrition is the study of nutrients and
!
*ESSENTIAL NUTRIENTS: nutrients that human cells cannot synthesize (i.e.
)
 CARBOHYDRATES
• Carbohydrate sources:
-
(not digested, but provides FIBER)
• How are carbohydrates used?
-they are broken down (oxidized) which releases
-excess glucose is stored as
-most carbohydrates supply
from glucose
• Carbohydrate requirements:
-recommended that carbs make up
-physically active individuals require more fuel than sedentary ones
-cellulose is a complex carbohydrate that humans cannot digest; provides
 LIPIDS
• Lipid sources:
-plant oils (unsaturated):
-animal products (saturated):
• How are lipids used?
-the liver and adipose (fat) tissue work together to regulate triglyceride metabolism
-lipids are used to build cell structures
-cholesterol is present in membranes and is also used to
• Lipid requirements:
-recommended that
-saturated fats should comprise no more than
-must be sufficient to carry fat-soluble vitamins
 PROTEINS
• Protein sources
-complete proteins have adequate amounts of all essential amino acids
-incomplete proteins lack adequate amounts of one or more essential amino acids
• How are proteins used?
-structural (
-enzymes (
,
,
,
,
-antibodies (
-messengers (
)
) that control metabolic reactions
)
)
-transport (hemoglobin; cell membrane proteins)
-may provide energy
• Protein requirements:
-should make up about
-must supply
-pregnant and nursing women should increase their protein intake
 VITAMINS (organic compounds required in small amounts)
• Fat-soluble vitamins:
-dissolve in (and stored in) fat
-include vitamins
-resist the effects of heat (therefore cooking does not destroy them)
• Water-soluble vitamins:
-dissolve in water
-include the
-cooking or processing food destroys some water-soluble vitamins
 MINERALS (elements, other than carbon, needed in small amounts for normal metabolism)
• Characteristics:
-most are stored in the
-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)
• Mineral functions include:
structural materials
can function as part of enzymes
play vital roles in metabolic processes
maintaining pH of body fluids
• Examples of Major Minerals:
-calcium , (
)
-phosphorus, (
)
-potassium, (
-sulfur, (
)
• Examples of Trace Elements:
-iron, (
)
-manganese, (
)
-iodine, (
-selenium, (
)
)
)
-chlorine, (
-magnesium, (
)
-cobalt
-zinc
(
(
-sodium, (
)
-copper, (
-fluorine, (
)
)
)
)
)
 ADEQUATE DIETS
• an adequate diet provides sufficient:
*essential nutrients necessary to support optimal growth, maintenance, and tissue repair
• malnutrition is poor nutrition due to:
Failure to make the best use of available food
*Malnutrition may be due to:
UNDERNUTRITION (
)
OVERNUTRITION (
)
Food processing occurs in 4 stages:
1)
(act of eating)
3)
(of nutrients)
2)
(into smaller molecules)
4)
(of wastes)
Digestion is the process of mechanically and chemically breaking down foods and absorbing the breakdown products.
The digestive system consists of an
and several
Alimentary canal includes:
●
●
●
●
Accessory organs are:
●
●
●
●
●
●
.
●
●
*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:
*motor functions include:
and
MOUTH (Oral Cavity)
*receives food and begins digestion
 Tongue:
-rough projections (
-papillae also contain
(include a wavelike motion called
) on surface of tongue provide friction to handle food
)
 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
, which
chemical digestion of carbohydrates, makes taste possible, and helps cleanse the mouth.
, helps bind food particles, begins
 secrete a watery fluid that contains the digestive enzyme
glycogen into smaller disaccharides)
(starts to break down starch and
 secrete a thick fluid called
, which binds food particles and lubricates during swallowing
PHARYNX / THROAT
 leads to esophagus and trachea
 when food is swallowed, trachea is blocked by
(cartilage flap)
ESOPHAGUS
 ESOPHAGUS: a food passageway from the
-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
STOMACH
*the stomach receives food,
,
limited amount of absorption, and moves food into the small intestine.
 Structure / Parts:
-has a capacity of
-separated from the small intestine by a powerful circular muscle:
.
, carries on a
 Gastric secretions include:
•
•
•
*together, these secretions form
 PEPSIN: most important digestive enzyme in gastric juice
-secreted in inactive form:
-when it comes into contact with hydrochloric acid, it becomes the active
(a protease)
*a layer of thick mucus is produced by cells in the stomach’s inner lining…this protective coating prevents the
stomach from digesting itself.
 Mixing and emptying actions:
-CHYME =
-chyme is emptied into the small intestine where chemical digestion continues
PANCREAS
Structure of the pancreas:
● The pancreas produces
the
that is then secreted into a pancreatic duct, which leads to
(first portion of the small intestine)
Pancreatic juice contains enzymes that split or break down:
●
●
●
●
*pancreatic juice also has a high
intestinal contents to be
concentration that helps
.
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
● 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
and causes
LIVER
Structure of the liver: The liver is divided into a large
and a smaller
Liver functions include:
● metabolizing carbohydrates, lipids, and proteins;
● storage of some substances;
●
;
.
● destroying toxins;
●
.
**Bile is the only liver secretion that directly affects digestion!!
Composition of BILE:
● BILE contains:
*
*only the BILE SALTS have digestive functions!
GALLBLADDER
 the gallbladder stores bile between meals and releases bile into the small intestine via the
 cholesterol in the bile may form solid
and
which could block the ducts
Functions of Bile Salts:
● emulsify fats (
● aid in the absorption of fatty acids, cholesterol, and certain vitamins
)
SMALL INTESTINE
*the small intestine receives secretions from the pancreas and liver,
products of digestion, and transports the residues to the large intestine.
, absorbs the
● the small intestine consists of the:
(first 25 cm)
Structure of the small intestine wall:
● the wall is lined with
turn, are covered with smaller extensions called
● intestinal glands are located between the villi
Secretions of the small intestine:
that increase the surface area and aid in mixing and absorption (these, in
)
● secretions include:
and
● digestive enzymes split molecules of
,
, and
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
.
LARGE INTESTINE
*the large intestine
, and forms and stores
● the large intestine consists of the:
(ASCENDING, TRANSVERSE, DESCENDING, and SIGMOID COLON)
Functions of the Large Intestine:
● has little or no digestive function
●
•
• forms and stores
 FECES consist of:
-
-
-
-
-