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digestion
transforming food into basic nutrients that can be absorbed and used by the body
Before food even enters the mouth, a cascade of events involving the nervous system and a variety of hormones are set off based on 5 stimulus:
cognition sound odor appearance taste
cognition
thoughts about food can start the flow of saliva
sound
hearing a description of the meal
odor
smells stimulate a hunger response and influence its taste
appearance
seeing the food
taste
begins as the food enters your mouth and also how it feels
We absorb nutrients for...
- fuel cellular growth 2)fight infections 3)provide energy to our muscles and brain
2 Processes Food is Broken Down
- mechanical
- chemical
Peristalsis
involuntary wavelike contractions that propel food along the digestive tract
Enzymes
Proteins that speed up chemical reactions
Gastrointestinal (GI) tract
a long hollow tube consisting of several layers of tissue that begins with the mouth and ends at the anus.
Absorption
The process by which nutrient molecules pass through the wall of the digestive system into the blood
6 parts of the GI tract
- Mouth
- Esophagus
- Stomach
- Small Intestine
- Large intestine
- Rectum
Membrane Transport chart
4 main organs produce and secrete substances that aid in digestion, but they are not part of the GI tract:
1 - salivary glands 2 - liver
3 - gallbladder 4 - pancreas
Mouth
The function of the mouth is to alter the food particles to prepare them to be swallowed. both mechanical and chemical digestions take place in the mouth.
mechanical digestion
occurs as the teeth break the food into smaller particles. The salivary glands are then stimulated to secrete saliva.
chemical digestion
Process by which enzymes break down food into small molecules that the body can use
Saliva
a watery fluid containing (1) a lubricant (mucus) and (2) enzymes to prepare food for the next step in the GI tract.
Epiglottis
flap that covers the trachea
During swallowing to prevent food from entering the trachea.
Mouth Enzymes
salivary amylase: break down starches lingual lipase: break down fats
intrinsic factor
a vital glycoprotein produced in the stomach. makes the absorption of vitamin B12 happen in stomach
Chyme
is the resulting substance when food particles are mixed with stomach acids and enzymes
Gastrin
is the hormone responsible for controlling the concentration of acid in the stomach. Gastrin is produced when we begin to think about eating foods as well as during the actual ingestion of food.
small intestine function
digestion and absorption. It is named the small intestine due to its small diameter.
large intestine function
Reabsorbs water and stores and eliminates undigested food, waste management
pyloric sphincter
Connects the stomach to the small intestines. Its major role is to control the release of chyme into the small intestine.
3 small intestine parts
duodenum, jejunum, ileum
Ileacecal sphincter
Between small and large intestine, prevents contents of the large intestine from entering the small intestine
Small intestine is lined with _____ folded over many times. Within the folds are finger-like projections called_____.
mucosa, villi
Villi
help trap food, and they are necessary for the processes of digestion and absorption.
Organs associated with small intestine
liver, gallbladder, pancreas
liver
secretes bile which is stored in the gallbladder to break down fats
Gallbladder
will store the bile until it receives a hormonal signal that fat has entered the small intestine.
Pancreas
constipation
the passage of a hard, dry stool
diverticulosis
increase risk with age, small pouches push out weak spot in the colon where food particles then get trapped and cause inflammation or infection
diarrhea
is the opposite of constipation. It is characterized by loose, watery, and frequent stools. Diarrhea usually results from an infection or a disease.
Glycogen
Storage form of glucose
irritable bowel syndrome (IBS)
More common in females. Symptoms include bloating, abdominal pain, cramps, diarrhea, and/or constipation. Certain foods aggravate the symptoms, including gas producing foods (such as beans), milk products, alcohol, caffeine, and fat.
Ulcers or peptic ulcer
re sores that can occur in the stomach, lower esophagus, or small intestine. Ulcers can be caused by certain bacteria (i.e. H. Pylori ), or even from medications such as nonsteroidal anti- inflammatory drugs (NSAID), which erode the protective mucus lining. Stress, smoking, and genetics also play a role in the development of an ulcer. Symptoms include a burning sensation in the stomach following a meal or at night, weight loss, nausea, vomiting, and loss of appetite.
Monosaccharides
glucose, fructose, galactose (simple sugars)
Disaccharide
A double sugar molecule made of two monosaccharides: sucrose, lactose, maltose
Polysaccharides
complex carbohydrates
insoluble fiber
fiber that does not dissolve in water and is not broken down by bacteria in the large intestine
soluble fiber
fiber that dissolves in water or is broken down by bacteria in the large intestine
functional fiber
fiber added to foods that has been shown to provide health benefits
protein sparing
the action of carbohydrate in preserving muscle. if inadequate carbohydrate is consumed, muscle is broken down to supply blood glucose
Details of digestion of carbohydrates
20 different ALL needed
nonessential amino acids
amino acids that the body can make, 11
essential amino acids
Amino acids that are needed, but cannot be made by the body, 9
Denaturation
process of disrupting and destroying a protein's structure
Pepsin
Enzyme that breaks down proteins in the stomach
Trypsin
an enzyme from the pancreas that digests proteins in the small intestine
protein functions
- Body structure
- Maintaining fluid balance
- Contribute to acid base balance
- Hormones and enzymes
- Contribute to immune function
- Provide energy and satiety
Protein in Adults
0.8g per kg of body weight
Animal protein
high quality
plant proteins
incomplete proteins
Kwashiorkor
severe protein lack; edema, weight loss, growth impairment, fatty liver, tired
Marasmus
means waste away, severe weight loss, wasting muscle and fat
fatty acids
- saturated
- mono-unsaturated
- poly-unsaturated
- trans-fats
Triglycerides
improve food taste, major form of fat in diet, carrier of fat soluble vitamins, insulation/protection
Phospholipids
a lipid consisting of a glycerol bound to two fatty acids and a phosphate group, formation of cell membranes and transport lipoproteins
Organ important in digestion that occur in small intestine...
gallbladder
IBS
Not well understood, bloating and abdominal pain
Bile
secreted in small intestine for digestion of fats
complementary proteins
2 or more plant proteins combine
LDL
delivers cholesterol into cells
Chylomicrons
delivers lipids to the liver
saturated fats
fats that are solid at room temperature, no double bonds
VLDL
triglyceride, carries lipids made and taken up by the liver to cells
protein digestion
begins in the stomach, enzyme pepsin
