Transcript 7_1_1-digestionlecture

Digestion
Journey of a cheeseburger
http://www.flickr.com/photos/liujoanne/2172007698/in/pool-47991555@N00
What is digestion?
• Digestion is the mechanical and chemical
breakdown of food into usable molecules
• The Alimentary Canal (GI Tract) extends
from the mouth to the anus with acessory
organs (liver and pancreas)
• It is a 9 meter long tube
• Your entire body can be thought of as a tube
within a tube.
• Movement through the tube is by wavelike
motion called peristalsis
Peristalsis
(The British spelling of esophagus is “oesophagus”)
Major Parts and Function of the
Digestive System:
• Mouth
– Teeth begin digestion mechanically
• Chewing (“mastication”) breaks apart food
• 2 sets of teeth
– Primary or “baby teeth” (20 in all)
– Permanent teeth (32 in all)
• Incisors for cutting
• Canines “fangs” for tearing
• Premolars and molars for grinding
– Tooth has a crown and a root
• Pulp contains the nerve and blood supply for
nutrients and waste removal
Tooth Diagram
Digestive System
– Saliva - begins chemical digestion of
carbohydrates & secrete amaylase (digestive
enzyme)
– Tongue - Pushes food back towards throat
– Palate (hard and soft) - roof of oral cavity
– Palatine tonsils - lymphatic tissue
– Pharyngeal tonsils (adenoids) - lymphatic
– Pharynx - connects nasal and oral cavities
Digestive system
• Esophagus - food passageway (heartburn
is caused by the effects of gastric juice on
the esophagus)
• Stomach - secretes gastric juices (pepsin,
hydrochloric acid) which digest proteins
and creates a paste of food called chyme.
• Pancreas - secretes pancreatic juice which
helps digest carbs, fats, and nucleic acids
and proteins.
Digestive system functions:
• Liver has many functions. The major are:
– production of bile, which helps carry away
waste and break down fats in the small intestine
during digestion
– production of certain proteins for blood plasma
– production of cholesterol and special proteins to
help carry fats through the body
– conversion of excess glucose into glycogen for
storage (This glycogen can later be converted
back to glucose for energy.)
Digestive system functions:
• Liver functions (continued):
– regulation of blood levels of amino acids,
which form the building blocks of proteins
– processing of hemoglobin for use of its iron
content (The liver stores iron.)
– conversion of poisonous ammonia to urea
(Urea is one of the end products of protein
metabolism that is excreted in the urine.)
– clearing the blood of drugs and other
poisonous substances
Digestive system functions:
• Liver functions (continued):
– regulating blood clotting
– resisting infections by producing immune factors
and removing bacteria from the blood stream
– stores vitamin D
• Gall Bladder
– Stores bile, releases through bile duct
– Bile in the gall bladder can precipitate and form
solids or “stones”
Digestive System functions
• Small Intestine
– Receives secretions from pancreas and
liver,completes digestion of nutrients in chyme,
absorbs products of digestion through fingerlike
projections called villi; transports residues to large
intestine
– 3 major sections
• Duodenum
• Jejunum
• Ileum
– Connected by mesentery which suspends these
portions from abdominal wall
Digestive System Components
• Large Intestine
– Absorbs water and electrolytes from chyme,
forms and stores feces
– Cecum = beginning of large intestine
– Appendix - small closed part, no longer serves a
digestive function, but contains lymphatic tissue
– Colon - 4 sections
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Ascending colon, begins at cecum
Transverse colon
Descending colon
Sigmoid colon
Digestive System
• Rectum
– Last part of large intestine
• Anus
– Expels waste - two sphincter muscles guard
the anus (one under involuntary control ,the
other, and final one, is under voluntary
control)
Nutrients
• 4 major nutrients
– Carbohydrates - supply energy (1 calorie per
gram)
– Lipids - supply energy for cellular processes
and for building cells, stores energy (9
calories per gram)
– Proteins - control metabolic rates, clotting
factors, keratin of skin and hair, source of
energy (1 calorie per gram)
Vitamins
• Organic compounds required in small amounts
for normal metabolic processes. Must come
from foods.
• Vitamins A,C,D, and E appear to have anticancer
effects. Most vitamins function as coenzymes to
help an enzyme accomplish a function
• Fat soluble - A,D,E,K
• Water-Soluble - Thiamin, Riboflavin, C, Niacin,
B6, Folate, B12, Biotin, Pantothenic acid
Vitamins
• A for healthy eyes, skin, bones and
hormone synthesis
• C for collagen, detoxification
• Folate needed for DNA and RNA
metabolism
• Niacin, Biotin, Thiamin needed for energy
metabolism
Minerals
• Concentrated in bones and teeth
• Major minerals are calcium and
phosphorous
• The body needs 7 - potassium, sulfur,
sodium, chloride and magnesium in
addition to trace amounts
• Fats and sugars have few minerals.
Minerals
• Phosphorus needed for bone and tooth
formation
• Magnesium needed for bone, tooth, and
enzyme formation
• Sulfur needed for cartilage, tendon, and proteins
• Sodium needed for nerve impulse transmission
• Potassium - nerve function
• Chloride - gastric juices and electrolyte balance
More Minerals
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Iron - for hemoglobin
Iodine for thyroid function
Fluoride - for bones and teeth
Zinc for insulin, sperm production
Selenium is an antioxidant
Copper helps produce hemoglobin
Chromium for energy metabolism
Manganese and molybdenum are
components of enzymes