Chapter 14 NUTRITION AND DIGESTION
The 4 Stages of Food Processing Ingestion… in another word Eating. Is the breakdown of food to small nutrient molecules. Is the uptake of the small nutrient molecules by cells lining the digestive tract.
Is the disposal of undigested materials from the food we eat.
1. The Digestive Tract Digestion dismantles food particles for use by the body. Involves physical processes like chewing.
Is the chemical breakdown of food by digestive enzymes.
Chemical digestion proceeds via hydrolysis : H monomer H 2 O polymer Hydrolases (enzymes that catalyze digestive hydrolysis reactions.) OH
Which means that it involves chemical reactions that break down polymers into monomers using water in the process.
The Human Digestive System
The Human Digestive System The human digestive system consists of: A digestive tube , the alimentary canal
Accessory organs that secrete digestive chemicals
Accessory organs Salivary glands Liver Gallbladder Pancreas Alimentary canal Oral cavity Tongue Pharynx Esophagus Stomach Small intestine Large intestine Appendix Rectum Anus
A. The Mouth The mouth, or oral cavity functions in ingestion and the preliminary steps of digestion . Saliva keeps the mouth moist. It contains enzyme salivary amylase which begins process of digesting starch
Comprised of skeletal muscles and Taste buds
The Teeth enamel dentin pulp gum cementum b. periodontal memb rane root canal jawbone root crown Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
B. The Pharynx Connects the mouth to the esophagus. Not swallowing Swallowing started Swallowing finished
Also opens to the trachea (respiratory tract). During swallowing, a reflex tips the epiglottis to close the windpipe entrance.
C. The Esophagus Connects the pharynx to the stomach. Moves food down by peristalsis.
Starts digestion of proteins
D. The Stomach Can store food for several hours.
2 major functions: digestion and defense
How Does the Stomach Work? The accidental shooting of a man in 1822 provided an opportunity for a doctor named William Beaumont to learn about the stomach ’s many functions. The hole was permanent and large enough that Beaumont could insert his entire forefinger into the stomach cavity.
What did he do to this poor man? Rate of Digestion of different food: Beaumont tied different types of food (protein, fat, carb) to the end of a silk string and dangled the food through the hole into the stomach. Beaumont pulled out the string 1, 2, 3 and 5 hours later. Stomach Stomach acid Fistula or tube String Food
Chemical Digestion in the Stomach This Churns food into a thick soup called acid chyme. The high acidity kills germs The stomach contains gastric juice made of strong acid , digestive enzymes , and mucus .
Normally empties in 2-6 hours
Stomach Ailments Are erosions of the stomach lining.
Are often caused by a bacterium named Helicobacter pylori, NOT stress .
Nothing to do with the heart! Discomfort or pain caused by the stomach contents traveling up from the stomach up into the gullet (lower part of your esophagus). The gullet is not made to withstand acid and is irritated and inflamed when acid from the stomach travels up into it.
Happens when you eat too much, wear tight clothes, bad posture….
E. The Small Intestine Longest part of the alimentary canal. Major organ for chemical digestion and absorption. Chemical Digestion in the Small Intestine: hydrolases break down food to monomers.
Duodenum (close to stomach)
Receives digestive agents from several organs. secretes bile, which helps digest fats . Duodenum
Secretes juice that neutralizes stomach acids into the duodenum.
Absorption of Nutrients Although food has been ingested,
It is not technically “in” the body yet .
Are parts of the small intestine specialized for absorption. The jejunum and ileum The intestinal wall contains villi and microvilli , which provide a large surface area for absorption.
Interior of intestine Villi Epithelial cells Blood vessels Epithelial cell Nutrient absorption microvilli
F. The Large Intestine (and Beyond) shorter, but wider, than the small intestine. Makes up most of the length of the large intestine. Absorbs water, salt and some vitamins from the alimentary canal .
Produces feces , the waste product of food.
Is the last 15 cm (6 inches) of the large intestine.
Regulates the opening of the rectum.
Food processing takes place along the alimentary canal. Ingestion Digestion Absorption Elimination http://video.about.com/ibdcrohns/Digestion.htm
G. Accessory Organs of Digestion Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. bile a. pancreas common hepatic duct pancreatic duct gallbladder common bile duct duodenum pancreatic juice
The Pancreas http://diabetes.emedtv.com/diabetes-video/what-does-the-pancreas-do-video.html Endocrine function (internal secretion) Exocrine function – pancreatic juice (external secretion) Sodium bicarbonate: neutralizes the stomach acid Pancreatic amylase: starch digestion
Trypsin: protein digestion
The Liver Largest gland in the body Lobules are the structural and functional units A bile duct takes bile away A branch of the hepatic artery brings O 2 rich blood A branch of the hepatic portal vein transports nutrients from the intestines
Each lobule has a central vein that enters a hepatic vein
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. bile canals bile duct b. branch of hepatic artery branch of hepatic portalvein central vein
Acts as a gatekeeper for the blood Removes poisonous substances and detoxifies them Removes and stores iron and vitamins A, D, E, K, and B 12 Regulates blood glucose, stored as glycogen Bilirubin – hemoglobin breakdown product The liver has many roles
Bile salts – emulsify fat
The Gallbladder Liver produces 400-800 ml of bile each day Water reabsorbed – thickens bile
Secreted through common bile duct into duodenum via common bile duct
Digestive Enzymes Proteins that speed up specific chemical reactions
Break down carbohydrates, proteins, nucleic acids, and fats
Human Nutritional Requirements
Nutrition Proper nutrition helps to maintain homeostasis. Fuel energy for cellular work.
to construct needed materials.
6 major classes of Nutrients Regulate metabolism (with vitamins and minerals)
Serves many important roles
Physical activity: 30 min at least/day A lot little Amount of food and proportion for each category The more active you are the more you should eat. But the proportions should remain the same
Balancing Calories: - Enjoy your food, but eat less - Avoid oversized portions Foods to Increase: - Make half your plate fruits and veg - Make at least half your grains whole grains - Switch to fat-free or 1% fat milk Foods to reduce - Lower sodium - Drink water instead of sugary drinks
Any food made from wheat , rice , oats , cornmeal , barley or another cereal grain . Examples: Bread, pasta, oatmeal, breakfast cereals, tortillas, 2 subgroups: Whole grains contain the entire grain kernel -- the bran, germ, and endosperm. GRAIN GROUP Examples : whole-wheat flour, Oatmeal, brown rice Refined grains have been milled, a process that removes the bran and germ. This is done to give grains a finer texture and improve their shelf life, but it also removes dietary fiber, iron, and many B vitamins.
Examples : white flour, white bread, white rice
OILS, FAT GROUP Fats, oils and cholesterol Unsaturated vs saturated lipids: Liquid at room temperature Found in vegetables and whole grains Solid at room temperature Animal origin (butter, meat)
Associated with cardiovascular disease
Fats That Cause Disease Plaques form in and block arteries Contain cholesterol and saturated fats Not soluble in blood, ie needs carriers, which are low density lipoprotein (LDL) and high density lipoprotein (HDL) LDL ( “bad” cholesterol) - transports cholesterol from the liver to cells
HDL- ( “good” cholesterol) - transports cholesterol away from arteries to the liver to make bile salts
Calories are a measure of the energy stored in your food . A measure of the energy you expend in daily activities . A kilocalorie is 1000 calories (The unit listed on food labels).
Food as Building Material The cells of your body assemble polymers from the monomers found in food. Essential nutrients are substances needed by the body that it cannot make itself.
A. Essential Amino Acids There are 8 essential amino acids (needed to make proteins).
Different foods contain different ones.
B. Vitamins Are organic molecules required in the diet for good health. Vitamins are defined by their biological activity , not their structure. Function mostly as assistants to enzymes.
Illnesses Due to Vitamin Deficiency Rickets due to vitamin D deficiency Pellagra dermatitis due to niacin deficiency Bleeding of gums is a symptom of scurvy, a vitamin C deficiency
Recommended daily allowances (RDAs) Minimal standards established by nutritionists for preventing nutrient deficiencies. Male 19-24 2900 kcal/day Female 19-24 2200 kcal/day
C. Minerals Are inorganic substances required in the diet (which means other than the 4 elements carbon, hydrogen, nitrogen and oxygen which are present in common organic molecules.) Calcium : construction of bones and teeth. Osteoporosis can be counteracted by uptake of Ca 2+ Chloride (salt) water balance Phosphorus: ATP, phospholipids, nucleic acids Iron: hemoglobin synthesis
Magnesium: nerve and muscle contraction, protein synthesis
D. Essential Fatty Acids Our cells make fats and other lipids by combining fatty acids with other molecules. Essential fatty acids are the fatty acids we cannot make from simpler molecules.
They are involved in inflammation, cell signaling. Produce various hormones and plasma membrane of cells
E. Decoding Food Labels
On food labels, the FDA requires:
7. Nutritional Disorders
7. Nutritional Disorders Nutritional dysfunction can cause severe problems. Malnutrition is a dietary deficiency of one or more of the essential nutrients. Protein deficiency is an example.
Undernutrition is caused by inadequate intake of nutrients. Can cause anorexia.
Obesity is an inappropriately high ratio of weight to height.
The majority of Americans consume too many fatty foods. This may be done to satisfy fat cravings. These cravings may have an evolutionary basis (sugar & fat give energy, good for reproduction, the brain wired us to like them). Mutation in one gene caused this mouse to be overweight even if its diet was low in fat.
To some extent, a tendency toward obesity is inherited ( Low metabolism could be an advantage in time of starvation, selection for such individuals).
Eating Disorders Can coexist with either obesity or anorexia nervosa Habit of binge eating and then purging Self-induced vomiting or use of a laxative Can be dangerous – abnormal heart rhythm, damage to kidneys, erosion of teeth Morbid fear of gaining weight
All the symptoms of starvation – death may result
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Donna Day/Stone/Getty Images Persons with bulimia nervosa have obsession about body shape and weight . recurrent episodes of binge eating: consuming a large amount of food in a short period and experiencing feelings of lack of control during the episode. Body weight is regulated by increase in fine body hair, halitosis, and gingivitis.
purging (self-induced vomiting or misuse of
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Persons with anorexia nervosa have Body weight is kept too low by a morbid fear of gaining weight; body weight no more than 85% normal. a distorted body image so that person feels fat even when emaciated. in females, an absence of a menstrual cycle for at least three months. a restrictive diet, often with excessive exercise. binge eating/purging (person engages in binge eating and then self-induces © Tony Freeman/PhotoEdit
vomiting or misuses laxatives).
28 years old - 59 pounds