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)

ESOPHAGUSESOPHAGUS: 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) chaperonins

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