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Food for Energy and Growth
The food animals eat provides both a source of energy and essential molecules that the animal body is not able to manufacture for itself
an optimal diet contains more carbohydrates than fats and also a significant amount of protein
Food for Energy and Growth Carbohydrates are obtained primarily
from cereals, grains, and breads on the average, carbohydrates contain 4.1
calories per gram the body uses carbohydrates for energy
Dietary fats are obtained from oils, margarine, and butter and are abundant in fried foods, meats, and processed snack foods fats contain 9.3 calories per gram the body uses fats to construct cell membranes,
to insulate nervous tissue, and to provide energy
Food for Energy and Growth
Proteins can be obtained from many foods, including poultry, fish, meat, and grains proteins have 4.1 calories per gram proteins are used for energy and as
building materials for cell structures, enzymes, hemoglobin, hormones, and muscle and bone tissue
Food for Energy and Growth
In wealthy countries, being significantly overweight is common this is due to habitual overeating and high-
fat diets, in which fats constitute over 35% of the total caloric intake
the standard measure of appropriate body weight is the body mass index (BMI), estimated as your body weight in kg, divided by your height in meters squared
Food for Energy and Growth
One essential characteristic of food is its fiber content fiber is the part of plant food that cannot be
digested by humans diets that are low in fiber result in a slower
passage of food through the colon low fiber is thought to be associated with
incidences of colon cancer
Food for Energy and Growth
Over the course of evolution, many animals have lost their ability to manufacture certain substances they need many vertebrates are unable to
manufacture one or more of the 20 amino acids used to make proteins humans are unable to synthesize eight amino
acids, which must be obtained from proteins in food
these are called essential amino acids
Food for Energy and Growth
In addition to supplying energy, food must also supply essential minerals, such as calcium and phosphorous some minerals are required in very small
amounts and are called trace elements
Essential organic substances that are used in trace amounts are called vitamins many vitamins are required cofactors for
enzymes
Digestion13
Processing of food Types
Mechanical (physical) Chew Tear Grind Mash Mix
Chemical Catabolic reactions Enzymatic hydrolysis
Carbohydrate Protein Lipid
Types of Digestive Systems
Heterotrophs are divided into three groups on the basis of their food sources herbivores eat plants exclusively carnivores are meat eaters omnivores eat both plants and animals
Single-celled organisms, as well as sponges, digest their food intracellularly
All other animals digest their food extracellularly, within a digestive cavity
Digestive System Organization
16
Gastrointestinal (Gl) tract (Alimentary canal) Tube within a tube Direct link/path between organs Structures
Mouth Oral Cavity Pharynx Esophagus Stomach Duedenum Jejenum kIleum Cecum Ascending colon Transverse colon
Digestive System Organization
Descending colon Sigmoid colon Rectum Anus
Accessory structures Not in tube path Organs
Teeth Tongue Salivary glands Liver Gall bladder Pancreas
17
The Mouth and Teeth
Many vertebrates have teeth, and chewing (mastication) breaks up food into small particles and mixes it with fluid secretions mammals have heterodont dentition, teeth of
different specialized types the general pattern of dentition is modified in different
mammals depending on their diet in carnivorous mammals, the canines are prominent, and
other teeth are more bladelike and sharp in herbivorous mammals, incisors are well-developed for
snipping, canines are reduced or absent, and molars are large and flat, with complex ridges well suited to grinding
The Mouth and Teeth
Humans are omnivores and human teeth are specialized for eating both plant and animal material humans are carnivores in the front of the
mouth and herbivores in the back children have only 20 teeth but these are
lost during childhood and replaced by 32 adult teeth
Deglutition (swallowing)
Sequence Voluntary stage
Push food to back of mouth
Pharyngeal stage Raise
Soft palate Larynx + hyoid Tongue to soft palate
Esophageal stage Contract pharyngeal
muscles Open esophagus Start peristalsis
25
Deglutition (swallowing)
Control Nerves
Glossopharyngeal Vagus Accessory
Brain stem Deglutition center
Medulla oblongata Pons
Disorders Dysphagia Aphagia
26
The Esophagus and Stomach
The esophagus is a muscular tube that connects the pharynx to the stomach the upper third is enveloped in skeletal
muscle for voluntary control of swallowing the lower two-thirds is surrounded by
involuntary smooth muscle rhythmic waves of contractions, called
peristalsis, propel food towards the stomach
Esophagus28
Usually collapsed (closed) 3 constrictions
Aortic arch Left primary bronchus Diaphragm
Surrounded by SNS plexus Blood vessels
Functions Secrete mucous Transport food
Esophagus30
Sphincters Upper Lower
Abnormalities Achalasia Atresia Hernia Barret’s esophagus Esophageal varices
The Esophagus and Stomach
The movement of food from the esophagus into the stomach is controlled by a ring of circular smooth muscle, called a sphincter contraction of the sphincter prevents food in the
stomach from moving back into the esophagus in humans, stomach contents can be brought
back out during vomiting the relaxing of the sphincter may lead to acid
reflux, which is when stomach acid moves into the esophagus this produces a burning sensation known as heartburn
The Esophagus and Stomach
The stomach is a saclike portion of the digestive tract the stomach contains an extra layer of
smooth muscle for churning food gastric juice is released by gastric glands
in the lining of the stomach parietal cells secrete hydrochloric acid (HCl) chief cells secrete pepsinogen
pepsinogen requires a low pH to be activated into pepsin, a protease that begins the digestion of proteins
Stomach33
Usually “J” shaped Left side, anterior to the spleen Mucous membrane
G cells – make gastrin Goblet cells – make mucous Gastric pit – Oxyntic gland – Parietal cells –
Make HCl Chief cells – Zymogenic cells
Pepsin Gastric lipase
Stomach
3 muscle layers Oblique Circular Longitudinal
Regions Cardiac sphincter Fundus Antrum (pylorus) Pyloric sphincter
Vascular Inner surface thrown
into folds – Rugae Contains enzymes that
work best at pH 1-2
35
Stomach
Functions Mix food Reservoir Start digestion of
Protein Nucleic acids Fats
Activates some enzymes
Destroy some bacteria Makes intrinsic factor –
B 12 absorption Destroys some bacteria
Absorbs Alcohol Water Lipophilic acid B 12
36
The Small and Large Intestines
The small intestine is the true digestive vat of the body only relatively small portions of chyme are
introduced into the small intestine at one time this allows time for acid to be neutralized and
enzymes to act in the small intestine, carbohydrates,
protein, and lipids are broken down and absorbed into the bloodstream
Small Intestine
Absorbs 80% ingested water Electrolytes Vitamins Minerals Carbonates
Active/facilitated transport
Monosaccharides Proteins
Di-/tripeptides Amino acids
Lipids Monoglycerides Fatty acids Micelles Chylomicrons
38
1.6 The Small and Large Intestines While some enzymes necessary for
digestion are secreted by the cells of the intestinal wall, most are made in the pancreas the pancreas is an exocrine gland,
meaning it secretes through ducts the pancreas sends it products via a duct
that empties into the first part of the small intestine, the duodenum
The Small and Large Intestines
Much of the food energy the vertebrate body harvests is obtained from fats fat digestion involves bile salts that are
secreted into the duodenum by the liver bile salts act like detergents and combine
with drops of fat to form microscopic droplets this process is known as emulsification this increases the surface area for the enzyme
lipase to work on in order to breakdown the fat
Small Intestine
Secretes digestive enzymes Peptidases
Amino- Di- Tri-
Sucrases Maltase Lactase Saccharidases
Di- Tri-
Lipase Nucleases
41
Large Intestine43
Extends from ileocecal valve to anus Regions
Cecum – Appendix Colon
Ascending Transverse Descending
Rectum Anal canal
Large Intestine45
Histology No villi No permanent circular folds Smooth muscle
Taeniae coli Haustra
Epiploic appendages Otherwise like rest of Gl tract
Large Intestine46
Functions Mechanical digestion
Haustral churning Peristalsis Reflexes
Gastroileal Gastrocolic
Chemical digestion – Bacterial digestion Ferment carbohydrates Protein/amino acid
breakdown
– Absorbs•More water•Vitamins
– B– K
– Concentrate/eliminate wastes
Feces Formation and Defecation Chyme dehydrated to
form feces Feces composition
Water Inorganic salts Epithelial cells Bacteria Byproducts of digestion
Defecation Peristalsis pushes feces
into rectum Rectal walls stretch
Control Parasympathetic Voluntary
47
Liver48
Location R. Hypochondrium Epigastric region
4 Lobes Left Quadrate Caudate Right
Each lobe has lobules – Contains hepatocytes – Surround sinusoids – Feed into central vein
Liver
Functions Makes bile
Detergent – emulsifies fats
Release promoted by: Vagus n. CCK Secretin
Contains Water Bile salts Bile pigments Electrolytes Cholesterol Lecithin
49
Liver
Detoxifies/removes Drugs Alcohol
Stores Gycolgen Vitamins (A, D, E, K) Fe and other minerals Cholesterol
Activates vitamin D Fetal RBC production Phagocytosis Metabolizes absorbed
food molecules Carbohydrates Proteins Lipids
50
Liver
Dual blood supply Hepatic portal
vein Direct input from
small intestine Hepatic
artery/vein Direct links to
heart
51
Vitmins53
• organic compounds that the body uses for metabolic purposes but is unable to produce in adequate quantity
Nutrient RDA Potential toxic effects Main function Best food sourcesVitamin A Men: 3,000 IU
Women: 2,300 IULiver toxicity, dry rough skin and
cracked lips, irritability, headache, birth defects
Healthy immune barriers and epithelial tissue, growth,
reproduction, bone and red blood cell formation, vision
Foods high in beta carotene, fortified
foods, liver
Beta carotene (as mixed
carotenoids)
N.D. Possibly increased lung cancer in smokers, harmless orange skin
colour
Antioxidant, source of vitamin A, immune booster, possible cancer
prevention, vision
Orange, yellow, red and green vegetables
and fruitsVitamin D 9-50 years: 200 IU
51-70 years: 400 IU> 70 years: 600 IU
osteoporosis: 1,000 IU
Heart/liver/kidney toxicity, hypercalcemia (excess calcium in
the blood)
Calcium metabolism, bone mineralization, possible cancer
prevention
Fortified milk, fatty fish
Vitamin E 22 IU Possible increase in heart disease, excess bleeding
Antioxidant, anticoagulant, protection from heart disease,
possible cancer prevention
Wheat germ, vegetable oils, nuts
Vitamin K M: 120 mcgW: 90 mcg
Interaction with blood thinners Bone mineralization, blood clotting
Green leafy vegetables
Vitamin C M: 90 mgW: 75 mg
smokers add 35 mg
Pro-oxidant, excess iron absorption, diarrhea
Antioxidant, immunity, antiviral in test-tubes, cancer prevention,
increases iron absorption
Fruits and vegetables, especially peppers and
citrus fruits
Thiamine (B1) M: 1.2 mgW: 0.9 mg
Very high doses may promote tumour growth
Energy metabolism, mood, nervous system
Whole grains, brown rice, fortified foods,
legumes, pork, oysters
Riboflavin (B2) M: 1.3 mgW: 1.1 mg
N.D. Energy metabolism, antioxidant, possible migraine prevention
Dairy products, leafy greens, oysters
Niacin (nicotinic acid)
M: 16 mgW: 14 mg
Itching, skin flushing,Liver toxicity, insulin resistance
Energy metabolism, lowers LDL cholesterol and triglycerides,
raises HDL cholesterol
Poultry, red meat, fish, legumes, peanut
butter, nutsVitamin B6 M: 1.3-1.7 mg
W: 1.3-1.5 mgNerve damage (neuropathy) Protein metabolism, immunity,
neurotransmitter synthesis (e.g. serotonin and dopamine), treats peripheral neuropathy and PMS
Meat, fish, poultry, eggs, potatoes, fortified cereals,
peanuts, soybeansFolate 0.4 mg High dose can mask B12 deficiency
leading to nerve damageCell division, prevents neural tube defects and perhaps other birth defects, lowers homocysteine,
possible cancer prevention
Leafy greens, legumes, oranges, broccoli,
cauliflower
Vitamin B12 (cobalamin)
2.4 mcg Rare cases of eye damage Cell division, amino acid metabolism, nervous system,
mental function
Fish, shellfish, meat, fortified soy and rice milk, fermented soy
products
Minerals
Major and trace minerals Major minerals are essentials of
cells and body fluids and are structural components of tissues
Trace minerals are for support for larger molecules to function
55
Minerals (table 8.5 in book)56
Calcium 1,000-1,200 mgCalcium deposits in soft
tissuesBone mineralization, muscle contraction
Dairy products, fortified soy and
rice milk, fish bones
MagnesiumM: 400 mgW: 320 mg
Diarrhea, decreased calcium absorption
Bone mineralization, active in more than 300 chemical reactions in the
body
Whole grains, nuts, green vegetables,
legumes
IronM: 8 mg
W: 18 mgIron overload disorders,
heart disease, liver cirrhosis
Makes hemoglobin which carries oxygen, makes
energy in the mitochondria
Meat, legumes, tofu, leafy greens, breakfast cereals
ZincM: 11 mgW: 8 mg
Immune suppression, nausea, metallic taste,
copper deficiency
Growth, immunity, wound healing, taste, sperm
production, antioxidant, prostate health
Oysters, meat, poultry, fish
Selenium 55 mcgBrittle hair and nails,
irritability, garlic breath, fatigue, nausea
Antioxidant, immunity, possible cancer
prevention, viral infections
Whole grains from selenium-rich soils, poultry, meat, dairy
Class homework
Keeping a food diary for 1 full week (7 days) Track all food and beverage consumption Use websites to track calories
Fitwatch.com Use measuring cups/spoons If you work-out; track your calorie outtake Also want 1 pg of what you learned over the
week Due via email in table format by NOV 18th
Worth: 50 points
57
Example: 58DATE: 10/16 Food Items: Calories
Breakfast: 1 egg sandwich (egg, bread, cheese, and ketchup)1 apple
27050
Snack: Hand full of almonds 150
Lunch: 2-Mc Donalds hamburgers with no cheese & NO PICKLEDiet coke
4000
Snack: Green tea with splendaAnimal crackers (20 of them)
0250
Dinner: Chicken breast (med size) with sweet potato, butter, and corn 2 cups of milk Glass of green tea sweetened with splendaPiece of pumpkin pie with cool whip
630
2000580
Activity: Walked the dogs around the neighborhood for 30 mins -250
Other notes: Had no energy when I got up this morning but by the afternoon I was feeling pretty good.
Total: 2530-250=2280