22 lecture presentation

Biology and Society: Stomach Surgeries

• Obesity in the United States:

– Occurs in 1 of every 3 adults

– Contributes to 300,000 deaths per year

© 2010 Pearson Education, Inc.

Figure 22.00

• Gastric bypass surgery, the most common weight-loss surgery in the U.S.:

– Reduces the stomach to the size of a chicken egg

– Bypasses the first section of the small intestine


• Weight-loss surgeries are successful in 90% of patients, when combined with:

– A healthy diet

– Exercise



OVERVIEW OF ANIMAL NUTRITION• Animals must feed on other organisms to acquire nutrients.


Animal Diets • Herbivores mainly feed on plants.

• Carnivores eat animals.

• Omnivores eat plants and animals.

Video: Shark Eating a Seal

Video: Lobster Mouth Parts

Herbivore(mainly eats plants

or algae)

Figure 22.1a

Carnivore(mainly eats animals)

Figure 22.1b

Omnivore(regularly eats animals

as well as plants or algae)

Figure 22.1c


The Four Stages of Food Processing• Ingestion is another word for eating.

• Digestion is the breakdown of food to small nutrient molecules.

• Ingestion is another word for eating.

• Digestion is the breakdown of food to small nutrient molecules.


Digestion: A Closer Look• Mechanical digestion

– Begins the process

– Involves physical processes like chewing

• Chemical digestion is the chemical breakdown of food by digestive enzymes.


• Digestion dismantles food to create:

– Molecules small enough for cells to absorb

– Monomers that can be recombined into new molecules

Cheese protein(a polymer of amino acidsin a specific sequence)

Breakdown of proteinby human digestivesystem

Amino acidmonomer

Amino acids

Figure 22.2-1



Amino acidmonomer

Amino acids

Absorption of amino acids by cells lining the smallintestine; transport via bloodstream to other cells

Figure 22.2-2



Amino acidmonomer

Amino acids

Absorption of amino acids by cells lining the smallintestine; transport via bloodstream to other cells

Human protein

Cells use amino acids from the cheese andother foods to produce new human proteins

Figure 22.2-3


• Chemical digestion proceeds via hydrolysis, chemical reactions that break down polymers into monomers using water in the process.

• Like most biological reactions, digestion also requires enzymes.

Enzyme(pepsin)

Protein digestion

Amino acidH2O

HOH

Figure 22.3a

Enzyme(amylase)

Carbohydrate digestion

SugarH2O

OH H

Figure 22.3b

Enzyme (lipase)

Fat digestion

Fatty acid

GlycerolH2O

H2O

H2O

OHH

H

H

OH

OH

Figure 22.3c


Digestive Compartments• In animals, chemical digestion is contained safely within some

kind of compartment.


• Food vacuoles are:

– Intracellular organelles filled with digestive enzymes

– The simplest of all digestive compartments

– Used by sponges as the only way to digest food


• Gastrovascular cavities:

– Are digestive compartments surrounded by cells

– Have only a single opening

Video: Hydra Eating Daphnia

Food(water

Flea)

Gastrovascular Cavity

Foodparticleengulfed

Singleopening

GastrovascularcavityHydra

Figure 22.4a


• Digestive tubes have two separate openings:

– A mouth

– An anus

Alimentary Canal (Digestive Tract)

Interior ofintestine

Earthworm

Intestine

Mouth

Anus

Figure 22.4b

A TOUR OF THE HUMAN DIGESTIVE SYSTEM System Map

• The human digestive system consists of:

– A digestive tube, the alimentary canal

– Accessory organs that secrete digestive chemicals


Salivary glands

LiverGallbladder

Pancreas

MouthTongue

Pharynx

Esophagus

Stomach

Small intestine

Colon of large intestine

AppendixRectumAnus

ACCESSORY ORGANS ALIMENTARY CANAL

Figure 22.5


The Mouth• The mouth, or oral cavity, functions in:

– Ingestion

– The preliminary steps of digestion


The Pharynx• The pharynx:

– Connects the mouth to the esophagus

– Opens to the trachea, which leads to the lungs


• During swallowing, a reflex:

– Tips the epiglottis

– Closes the entrance to the windpipe

EsophaTrachea(windpipe) open

Esophagusclosed

Epiglottisup

Ball offood

Pharynx

Tongue

NOT SWALLOWING SWALLOWING STARTED

Epiglottisdown

EsophagusopenTrachea

closed

Adam’sapple

SWALLOWING FINISHED

Epiglottisup

Tracheaopen

Esophagealsphincter(contracted)

Figure 22.7-3


The Esophagus• The esophagus:

– Is a muscular tube

– Connects the pharynx to the stomach

– Moves food down by peristalsis, alternating waves of muscular contraction and relaxation

Esophageal sphincter(contracted)

Contracted muscles

Relaxed muscles

Relaxed musclesFood ball

Stomach

Figure 22.8


The Stomach• The stomach:

– Can store food for several hours

– Churns food into a thick soup called chyme


• Fluid in the stomach contains gastric juice, made of:

– Strong acid

– Digestive enzymes

– Mucus

– The enzyme pepsin, which digests proteins


Stomach Ailments

• Heartburn is caused by backflow of chyme into the esophagus.

• Gastric ulcers are:

– Erosions of the stomach lining

– Often caused by the bacterium Helicobacter pylori

Stomach mucus Helicobacter pylori bacteria

Co

lori

zed

SE

M

Figure 22.10


The Small Intestine• The small intestine is:

– The longest part of the alimentary canal

– The major organ for chemical digestion and absorption of nutrients into the bloodstream


Chemical Digestion in the Small Intestine

• Most chemical digestion occurs in the duodenum, the first part of the small intestine.

• In the duodenum, chyme from the stomach mixes with:

– Pancreatic juice

– Bile

– A digestive juice secreted by the intestinal lining

Liver

Gallbladder

Bile

Bile

Chyme

Stomach

Pancreas

Pancreatic juice

Duodenum ofsmall intestine

Intestinalenzymes

Figure 22.11


• The pancreas secretes juice that neutralizes stomach acids in the duodenum.

• The liver secretes bile, which:

– Is stored in the gallbladder

– Helps digest fats


Absorption of Nutrients

• In the duodenum, nutrients are:

– Completely digested

– Ready to be absorbed

• Nutrients only enter the body if they are absorbed into the walls of the digestive tract.


• Villi and microvilli on the surface of the small intestine increase:

– The surface area

– Capacity for absorption

Blood vessels



Musclelayers

Nutrientabsorption

Nutrientabsorption

Nutrientabsorption

Epithelialcells

Bloodcapillaries

Lymphaticvessel

Epithelial cellsand blood capillary

Intestinal wall

Microvilli

Villi

Blood

Villi

Figure 22.13

Blood vessels

Interior ofintestineMuscle

layers

Nutrientabsorption

Intestinal wall

Villi

Figure 22.13a

Interior of intestine

Nutrientabsorption

Epithelialcells

Bloodcapillaries

Lymphaticvessel

VilliFigure 22.13b

Nutrientabsorption

Epithelial cellsand blood capillary

Microvilli

Blood

Figure 22.13c


The Large Intestine• The large intestine is:

– Shorter, but wider, than the small intestine

– About 1.5 meters in length


• The colon:

– Forms the main portion of the large intestine

– Absorbs water from the alimentary canal

– Produces feces, the waste product of food


• The rectum:

– Forms the last 6 inches of the large intestine

– Stores feces until elimination

• The anus:

– Consists of two sphincters

– Regulates the opening of the rectum

Colon oflargeintestine

Endof smallintestine

Smallintestine

Nutrientflow

Sphincter

Appendix

Rectum

Anus

Figure 22.14


• Food processing takes place along the alimentary canal.

Ingestion Food into mouth

Smallintestine

Largeintestine

Stomach

Mouth

Anus

FoodDigestion Mechanical digestion Chewing in mouth Churning in stomach

Chemical digestion Saliva in mouth Acid and pepsin in stomach Enzymes in small intestine

Absorption Nutrients and water in small intestine

Water in large intestine

Elimination Feces formed in large intestine

Elimination from anus

Figure 22.15-4


HUMAN NUTRITIONAL REQUIREMENTS• Proper nutrition helps maintain homeostasis.

• A balanced diet provides:

– Fuel for cellular work

– Materials for building molecules

– Essential nutrients for health


Food as Fuel• Cells use cellular respiration to:

– Extract energy stored in food molecules

– Generate molecules of ATP to do work

“Fuel”(organic moleculessuch as glucose)

Cellularrespiration

Mitochondrion

Cell

O2C6H12O6

Figure 22.16-1

Cellularrespiration

Mitochondrion

Cell

O2

ATP

and

energy forcellular work

“Exhaust”

H2OCO2

“Fuel”(organic moleculessuch as glucose)

C6H12O6

Figure 22.16-2


Calories

• Calories are a measure of the energy:

– Stored in your food

– Used in daily activities


• A calorie is the amount of energy required to raise the temperature of one gram of water by 1ºC.

• A kilocalorie (kcal) is:

– One thousand calories

– The unit listed on food labels

– Often called Calories with an uppercase C


Metabolic Rate

• The rate of energy consumption by the body is the metabolic rate.

• A person’s metabolic rate consists of:

– The basal metabolic rate (BMR), the amount of energy it takes to maintain body functions

– Energy needed for activities

Table 22.1


Food as Building Material• Building blocks from the breakdown of organic molecules are

used to:

– Repair tissues

– Maintain tissues

• Essential nutrients:

– Are substances needed by the body but

– Cannot be made in the body from other molecules


Essential Amino Acids

• In humans, eight essential amino acids:

– Must be obtained from the diet

– Are in different proportions in different foods

• All eight essential amino acids can be consumed by eating:

– Meat, eggs, or milk or

– A variety of plants, typically grains and legumes

Essential amino acids

Corn

Beansand otherlegumes

MethionineValineThreoninePhenylalanineLeucineIsoleucineTryptophanLysine

Figure 22.17a

Complete meals

Bread and peanut butterRice and beans Rice and tofu

Figure 22.17b


Vitamins

• Vitamins:

– Are organic molecules

– Are required in the diet in very small amounts

– Usually assist enzymes in catalyzing metabolic reactions


• Too much or too little of most vitamins can cause harm.

Table 22.2a

Table 22.2b


Minerals

• Minerals are inorganic substances required in the diet.

• Too much or too little of most minerals can cause harm.


Essential Fatty Acids

• Our cells make fats and other lipids by combining fatty acids and other molecules.

• Essential fatty acids must be obtained in the diet.


Decoding Food Labels• On food labels, the FDA requires:

– The list of ingredients

– Key nutrition facts

Figure 22.18

Figure 22.18a

Figure 22.18b


NUTRITIONAL DISORDERS• Nutritional dysfunction can cause severe problems.


Malnutrition• Malnutrition refers to health problems caused by an:

– Improper or

– Insufficient diet

• Protein deficiency:

– causes the most human suffering

– Is concentrated where there is a great gap between food supply and population size


Eating Disorders

• Eating disorders:

– Affect millions of Americans

– Are more common in women than men

– Result in malnutrition


• Anorexia nervosa is self-starvation, even when a person is underweight.

• Bulimia involves:

– Binge eating

– Purging through induced vomiting

– Abuse of laxatives, and/or

– Excessive exercise


Obesity• Obesity:

– Is an inappropriately high body mass index (BMI)

– Is the nutritional disorder of greatest concern

– Affects about one-third of all Americans

– Increases the risk of heart attack, diabetes, and other diseases

Weight (pounds)

He

igh

t

Und

erw

eigh

tB

MI <

18.5

Nor

mal

BM

I 18.

5–24

Ove

rwei

ght

BM

I 25–

29

Obe

seB

MI 3

0–39

Ext

rem

ely

obes

eB

MI >

39

6’4”

6’3”

6’2”

6’1”

6’0”

5’11”

5’10”

5’9”

5’8”

5’7”

5’6”

5’5”

5’4”

5’3”

5’2”

5’1”

5’0”

4’11”

4’10”100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260

Figure 22.20

Evolution Connection:Fat and Sugar Cravings

• Most Americans:

– Crave fatty and/or sweet foods

– Eat too many high-calorie foods

• A feast-or-famine existence in our ancestors may have favored individuals who gorged themselves on rich, fatty foods.


Figure 22.23

Ingestion

Food Food inmouth

Digestion

Mechanicaldigestion

Chemicaldigestion

via enzymes

Smallmolecules

Insidebody

Absorption

Elimination

Undigestedmaterials

Figure 22.UN1-4

Mouth(oral cavity)

Pharynx andesophagus

Stomach

Small intestine

Large intestine

Anus

Salivary glands

Liver,gallbladder,pancreas

Chewing

Churning

Salivaryamylase

Acid andpepsin (ingastric juice)

Otherenzymes

Nutrientsand water

Water

Alimentarycanal

Accessoryorgans

Digestion

Mechanical ChemicalAbsorption

Figure 22.UN2

Cell

Food

O2

Cellularrespiration

Figure 22.UN3-1

Cell

Food

O2

Cellularrespiration

H2OCO2

ATP

Figure 22.UN3-2

EssentialAmino Acids

EssentialFatty Acids

MineralsVitamins

Requiredfor proteinproduction

Organic moleculesrequired in verysmall amounts

Essential chemicalelements frominorganiccompounds

Requiredto make cellmembranes

ESSENTIAL NUTRIENTS

Figure 22.UN4

Figure 22.UN5

Nutrition FactsServing Size 1 Cookie 28 g/1 ozServings Per Container 8

Calories 140 Calories from Fat 60

Total Fat 7g

Cholesterol 10mgSodium 80mgTotal Carbohydrate 18g

Protein 2g

Saturated Fat 3g

Trans Fat 0g

Dietary Fiber 1g

Sugars 10g

% Daily Value*

11%

15%

3%

3%

6%

4%

Amount Per Serving

Science

22 lecture presentation