DIGESTION AND HUMAN NUTRITION

CHAPTER 36

DIGESTIVE TASKS

Animal digestion involves four tasks:

• Ingestion: _________________________________________

• Mechanical and chemical digestion: breaking down food into smaller components

• Absorption: _______________________________________ _________________________________________________

• Elimination: _______________________________________ ________________________________________________

SAC OR TUBE?

Flatworms and Cnidarians(marine spp specialized cells for capturing prey)

• Gastrovascular cavity: __________________________________________________________________________

• Single opening for food to enter and waste to be excreted

• Each load of food must be broken down, nutrients absorbed and wastes eliminated before a new load of food can enter

SAC OR TUBE?

Most invertebrates and all vertebrates

• Complete digestive tract: a tubular gut with _______ openings• Food exits through:

• Anus: mammals, one purpose→___________________• Cloaca: amphibians, reptiles, birds,

multipurpose→______________________________________________________________________________

• Coelomate animal (earthworm): has a fluid filled body cavity• “Tube within a tube”

PROCESSING SPECIFIC FOODSFeatures of animal digestive systems are shaped by natural selection; animals are adapted to a particular diet

• Shape of bird’s _________ determines food source

• Four types of mammalian teeth are best suited for different types of food

• Gizzard (________________________________________________________________) breaks down tough food in birds

• Ruminants (hoofed mammal) have multiple stomach chambers and beneficial microbes for a cellulose-rich diet

• https://www.youtube.com/watch?v=iHpVGJ2RhDk

COMPONENTS OF HUMAN DIGESTIVE SYSTEM

Different components of the human digestive system specialize in:

• __________________, ______________________, and concentrating and storing unabsorbed waste

Salivary glands, the pancreas, and the liver are accessory organs that secrete substances into the tube

COMPONENTS OF HUMAN DIGESTIVE SYSTEM

Food enters the body through the _____________

____________digestion begins when teeth rip and crush food

Movements of the tongue help mix food with saliva secreted by _______________glands (exocrine glands in the mouth)

• The enzyme __________________________begins the process of chemical digestion

COMPONENTS OF HUMAN DIGESTIVE SYSTEM

Food is forced into the _____________(throat) by swallowing

• ______________ blocks food from entering airways

Food then enters the _______________: tube between the pharynx and stomach

• Peristalsis: ________________________________________ _________________________________________________

Stomach: ___________________________________________ ____________________________________________________

The stomach empties into the ___________________: region where most nutrient molecules (and water) are digested and absorbed

• Secretions from the _______and __________assist the small intestines

The large intestine absorbs water and ions, thus compacting digestive wastes

• Wastes are briefly stored in the _________ before being expelled from the _____________

COMPONENTS OF HUMAN DIGESTIVE SYSTEM

THE STOMACH

The human stomach is a ____________, _____________sac with a sphincter (____________) at either end (regulates flow)

The stomach has three functions:

• _________________________________________________

• _________________________________________________

• _________________________________________________

Gastroesophageal sphincter

serosa

THE STOMACH

When empty→highly folded

Mucosa(glandular epithelium) lines the inner wall, secretes 2L gastric fluid (contains digestive enzymes, acid and mucus) each day

Stomach’s smooth muscle contracts 3 times per min.

• Mixes gastric fluid with food to form __________________• Propels chyme out through _________________________

STOMACH DISORDERS

Gastroesophageal reflux: _____________________________ ___________________________________________________; acidic chyme splashes into the esophagus

Stomach ulcers: typically arises after H. pylori releases chemicals that increase _____________secretion

• Also caused by continual use of nonsteroidal anti-inflammatory drugs, which inhibit the release of protective mucus

SMALL INTESTINE

Chyme leaves stomach through pyloric sphincter into the ______________________

Most __________and _____________takes place at the lining of the small intestine

The many folds and projections of the small intestinal lining increase its _______________ by hundreds of times

• Villi: multicelled projections• Microvilli: thin projections that increase the surface area of

epithelial cells• Brush border cells: epithelial cell with microvilli

lymph vessel

villi

blood vessels

A Longitudinal cross-section through thesmall intestine showing its folded lining.

B Intestinal fold withvilli at its surface.

C One villus with brush border cellsat its surface.

D A brush border cell with microvilliat its free surface.

E Micrograph of microvillion a brush border cell.

SMALL INTESTINE

Like the stomach, the small intestine has three layers of smooth muscle

• Muscles mix chyme, propel it forward, and force it up against the wall of the small intestine to enhance the rate of digestion and absorption (___________)

BREAKING DOWN OF FOOD AND ABSORBTION

Process of chemical digestion is completed in the ______________________________________

• Chyme from the stomach, enzymes and bicarbonate from the pancreas, and bile from the gallbladder aid in chemical digestion

THE PANCREAS

Chyme from the stomach is joined by ______and pancreatic ___________________.

• Bile is produced by the __________, stored in the ____________and enters the small intestine through the ____________________________

• https://www.youtube.com/watch?v=NZ4zcrTzUjA

BREAKING DOWN FOOD

Carbohydrates: broken down into _____________________

• Enzymes involved: _________________________________ _________________________________________________

Proteins: broken down into polypeptides and then into ___________________________

• Enzymes involved: ________________________________ _________________________________________________

BREAKING DOWN FOODFat:

• Movement of the intestinal wall break up fat globules into small droplets. ___________coat the droplets so they remain separated.

• Pancreatic enzymes digest the fat droplets to ____________and __________________

• These diffuse across the plasma membrane’s lipid bilayer, into _______________________________

• Forms triglycerides, associated with proteins to form lipoproteins, which are expelled by exocytosis into interstitial fluid

https://www.youtube.com/watch?v=H915Go4k8m8

https://www.youtube.com/watch?v=KRkYSYG5HXw

https://www.youtube.com/watch?v=G_7EchSkkc0

WATER UPTAKE

About 80 percent of water moves across the small intestinal lining and into the internal environment by ______________

• Water follows that gradient from chyme into the interstitial fluid

LARGE INTESTINE (COLON)

Substances move from the small intestine to the large intestine:

• Indigestible material, dead bacteria and mucosal cells, inorganic substances, and some water

• As wastes travel through the large intestine, they become compacted as ______________

Concentrates waste by actively pumping ___________across its wall, water follows by _______________

Favorable conditions for ___________________________

LARGE INTESTINE (COLON)

The first part of the large intestine is a cup-shaped pouch called the _____________

• A herbivore cecum contains many bacteria that help breakdown ____________________

• In humans and many other mammals, a short, tubular

appendix projects from the cecum• Serves as a ____________________________________

Cecum connects to colon, colon ascends the wall of abdominal cavity, extends across cavity, descends and connects to the ______________________.

USING CARBS, FATS AND PROTEINS

Dietary carbohydrates, fats, and proteins are _____________: substances that we require in ______________amounts

• Needed for ______________and raw materials• Breakdown products of these molecules serve as reactants in

____________________• Starch and sugars release _______________→primary

source of energy.• Excess stored• Liver stores glucose as glycogen

• Fats = energy source + build cell membranes• _________________________________

ESSENTIALS

ESSENTIAL FATTY ACIDS

Can not be synthesized, must obtain from food

______________________________________________________

ESSENTIAL AMINO ACIDS

Can not be synthesized, must obtain from food

______________________________________________________

VITAMINS AND MINERALS

Vitamins: ____________________________________________ ____________________________________________________

Minerals: ____________________________________________ ____________________________________________________

• Calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium

FRUITS, VEGETABLES, AND WHOLE GRAINS

Should make up the _________________ proportion of your diet

• These foods provide sugars and starches, your primary sources of energy

Two types of fiber: _____________________________________

• Eating foods high in ______________helps lower one’s cholesterol level and reduces the risk of heart disease

• Eating foods high in __________________prevents constipation

Whole grains provide more vitamins and fiber than their processed counterparts

• A whole grain includes all components of a grain seed• White wheat flour is made solely from endosperm

HEART-HEALTHY OILSA healthy diet includes fats that provide energy and meet your need for essential __________

Essential _________ are polyunsaturated

• Omega-3 fatty acids• Omega-6 fatty acids

LEAN MEAT AND LOW-FAT DAIRY

Meat (including poultry and fish) is the richest source of _____________and is also rich in essential iron

Lean meats minimize intake of saturated fats and cholesterol

Eating soybean products provides complete protein without harmful fats or cholesterol

Milk and dairy products are good sources of protein, vitamins, and minerals, but whole milk is rich in ________________________

MINIMAL ADDED SALT AND SUGAR

Eating foods with added salt elevates the body’s __________ level, which raises the risk of ______________________

Enough sodium from unsalted food

Commercially prepared foods and drinks are often high in added sugar

One can of soda has 30g of sugar

• Woman: 24g per day• Men: 36g per day

WEIGHT

When the food you eat contains more energy than you need, you store the excess as bond energy in organic compounds

• The body’s largest energy store is fat in _________________

For most of our species’ history, an ability to store energy as fat in adipose tissue was selectively advantageous

• However, most people in the United States now have more than enough food all of the time

• As a result, about two-thirds of adults are overweight or obese

BMIBody mass index (BMI) is a measurement designed to help assess increased health risk associated with weight

Body mass index formula:

BMI = weight (pounds) × 703

height (inches) × height (inches)

Generally, individuals with a BMI of 25 to 29.9 are said to be overweight

A score of 30 or more indicates obesity: an overabundance of fat in adipose tissue that may lead to severe health problems

To maintain a given weight, you must balance the amount of energy in the food you eat with the energy you expend in your activities

HOW MANY KILOCAL SHOULD YOU EAT?

Weight (pounds) ×10/15/20 (higher number for higher activity level)

Then subtract according to age:

25-34 0

34-44 100

45-54 200

55-64 300

Over 65 400