Digestive System Part II

Digestive Organs- the Stomach

Digestion is regulated by hormones and the Nervous System

Stomach hormone: Stomach hormone: GastrinGastrin

produced in the presence of protein-containing food in the stomach

stimulates the release of gastric juices and muscular contractions of stomach & intestine

Chemical Digestion

Accessory Digestive Organs

Structure of the small intestine

Small Intestine

Small intestine is 20-23’ long:Small intestine is 20-23’ long:

1) duodenum 8-10”2) jejunum 8’3) ileum 12’

duodenum – most active in digestionduodenum – most active in digestion jejunum & ileum – absorptionjejunum & ileum – absorption

Digestion in Small IntestineDigestion is regulated by hormones and the Nervous System

Duodenal hormones

1) secretinsecretin – stimulates pancreas & liver to secrete

2) cholecystokinin (CCK)cholecystokinin (CCK) – triggers release of enzymes from pancreas and gall bladder (amylase, lipase, etc.)

Activation of protein-digesting enzymes in the small intestine

Accessory Organs: Liver

largest internal organ = 3 lb chemical factory

processes food by the Hepatic Portal Hepatic Portal VeinVein delivered from digestive tract

though the liver performs many functions

Liver Functions1) Filter blood for wastes to produce urea

2) Maintain a Constant glucose level in bloodstream

Remove excess sugar from blood or release it when needed Glygogen (Liver) Glucose (Blood) Will also metabolize amino acids to make glucose if necessary!!

2) Detoxification blood of drugs & alcohol

3) Production of bile – to emulsify fat in the duodenum

4) Destroy old Red Blood Cells5) Make blood proteins

6) Regulation of cholesterol & other fats

Chopping up Protein

Cut off the NH2 to supply glucose

BileBile produced by liver, stored in gall bladder

enters small intestine by duct from gall bladder

fat emulsifier

contains bilirubin (breakdown hemoglobin) Jaundice occurs when bilirubin isn’t broken down

neutralizes stomach acid, contains sodium bicarbonate (baking soda)

Jaundice Yellow tinge to skin or

whites of eyes occurs when rbc’s bilirubin is not broken down properly by the liver

Other Liver Disorders1. Viral Hepatitis

often cause jaundice Hep A often transmitted by infected water, shellfish, etc Hep B often associated with exposure to contaminated

blood products. This one will destroy the liver over time

2. Cirrhosis Long term disease of the liver where liver becomes

fatty. Alcoholism is leading cause of cirrhosis as the toxin (ethanol) is difficult to break down over time

Cirrhosis of the Liver

The Digestive Enzymes

Enzymes are hydrolytic, meaning they introduce water to break the molecular bonds of nutrients (protein, fats, carbs, etc)

In the Mouth Starch + H2O ----------------------> Maltose

salivary amylase

Stomach

Protein Digestion

Low pH turns pepsinogen into active enzyme pepsin

Protein + H2O ----------------------> Peptides (AA chains) pepsin

Small Intestine (duodenum first)Neutralization, then Absorption

Pancreatic juice (amylase) enters. It contains sodium bicarbonate which neutralizes acid from the stomach

Starch + H2O ----------------------> maltose pancreatic amylase

Protein + H2O ----------------------> peptides trypsin

Starch + H2O ----------------------> glycerol + 3 Fatty Acids bile salts/lipase

Small IntestineFurther Breakdown …

Peptides are further broken down into Amino AcidsMaltose is broken down into glucose, the simplest sugar

Source: peptidase & maltase secreted by intestine villi

Peptides + H2O ----------------------> Amino Acids peptidases

Maltose + H2O ----------------------> Glucose maltase

Enzymes of the Digestive System

The Essential Amino Acids There are 20 amino acids we require

9 cannot be made in our bodies and must be supplied by diet

Sources:

Complete Protein ---> Meat

- supplies all 20 AA’s

Incomplete Protein ---> Vegetable products

- must use combinations to supply all 20 AA’s- ex. Beans and Rice- Soy protein is excellent but not complete by

itself

Recommended Daily Allowances

120 lb. female needs 44 grams per day 144 lb. male requires 56 grams per day

ServingsCup of milk = 8gRoast beef slice (3oz) = 25gMmmm…

The Essential Fatty Acid Fats were the enemy in the 1990’s

At 9.3 cal/g, reducing fat was identified as a “fad” method to drop weight

Reducing fat intake, while increasing exercise is a good idea to maintain weight, but cutting fat all together is foolish

Why? Fats are necessary for the production of hormones and cell membranes

Essential Fat linoleic acid. Without it, we cannot produce phospholipids for cell membranes

OBESITY 61% of North Americans are overweight or obese. Defined as 20% above desirable weight. Can lead to diabetes, hypertension, hyperlipemia,

cancer, cardiovascular disease, sleep apnea and gout. Very complex condition. Never the result of just one factor, but has many causes,

which may include: genetics, environmental/social lifestyle, food selection, inactivity, and behavioral conditions.

WEIGHT LOSS

What works?

Moderate calorie restriction, regular aerobic exercise, combined with strength training,

low fat/high fiber

diet, and behavioral changes.

WEIGHT LOSS

Body fat reduction Must include both nutrition and exercise. Educate and encourage a healthy weight loss

plan.

Exercise Long duration, low intensity aerobic. At least 30 min., but 45 min. is the best.

GOAL FOR WEIGHT LOSS With a 500 cal decrease per day = 3500 per week = 1lb. of fat. When combined with increased activity level, provides 1-2 lbs.

weight loss per week.

Monitor yourself (food/PT log)

Calorie control: Meal planning (Exchange system/Food guide pyramid) Encourage healthy balance of nutrients, portion control, variety and

choices.

Enzyme Problems / Deficiencies

Lactose Intolerance 75% of African Americans do not have

sufficient levels of LACTASE to digest lactose into glucose/galactose sugars

Result is painful cramps, diarrhea and bloating as the milk ferments in the digestive tract

Vitamin Deficiencies cause Diseases

Vitamin C - Scurvy

Niacin (B3)- Pellagra (Skin Disease)

Vitamin D - Rickets

Vitamin A - Night Blindness

Vitamin K - Blood clotting problems

Ricketts – Vitamin D deficiency

B6 Deficiency

Mild deficiency Cheilosis Mouth soreness Seborrhea – oily face/ scalp Weakness Irritability

Severe Angular Cheilosis

Recommended Sodium Intake

400-3300 mg per day

More salt makes blood hypertonic Water from surrounding tissues is

pulled in by osmosis

BP increases! This can create hypertension, leading to heart attacks, aneurisms and strokes