Transcript Digestive System - Ecto

Digestive System
Food Processing
• Food is processed in 4 stages:
– Ingestion
– Digestion
– Absorption
– Elimination
Digestion
• Digestion: the process that breaks down food
into small molecules so they can be absorbed
and move into the blood
• 2 types:
– Mechanical: when food is chewed, mixed, and
churned
– Chemical: chemical reactions break down large
molecules into smaller ones
Chemical Digestion
• Made possible through enzymes
• Enzyme: protein that speeds up the rate of a
chemical reaction in the body
– Reduce the amount of energy needed for
chemical reactions to begin
– Aid with chemical digestion without being used up
Enzyme Examples
• Amylase (produced by glands near mouth)
speeds up breaking down complex carbs into
simple carbs
• Pepsin in stomach aids with chemical
reactions that break down proteins
• Enzymes in small intestine aid in breaking
down proteins into amino acids
• Pancreas releases enzymes into small intestine
to help break down sugars and fats
Digestive System
• 2 types of organs: digestive tract and
accessory organs
• Digestive tract: organs that food passes
through
– Mouth, esophagus, stomach, small intestine, large
intestine, rectum, anus
• Accessory organs: food doesn’t pass through
them but they are essential for digestion
– Tongue, teeth, salivary glands, liver, gallbladder,
pancreas
The Mouth
• Mechanical digestion:
– Chew food with your teeth
– Mix food with your tongue
• Chemical digestion:
– Salivary glands release saliva, which mixes with
food
– Enzyme in saliva begins to break down starch into
sugar
• Food is swallowed and ingestion is complete
The Esophagus
• Epiglottis covers windpipe to ensure food
enters esophagus and prevent choking
• Esophagus: muscular tube about 25 cm long
• Peristalsis moves food down esophagus
• Peristalsis: waves of muscular contractions
that move food through the digestive system
• No digestion (mechanical or chemical) takes
place
The Stomach
• Mechanical digestion:
– Peristalsis causes food to mix
• Chemical digestion:
– Strong digestive solutions such as hydrochloric
acid mix with food to break it down
– Pepsin works with hydrochloric acid to digest
protein
The Stomach
• Mucus makes food slippery and protects
stomach from acid
• Takes 2-4 hours for food to move through
stomach and change into thin, watery liquid
called chyme
• Chyme then enters small intestine
The Small Intestine
• Most digestion takes place in the first part of
the small intestine, called the duodenum
• Mechanical digestion:
– Peristalsis continues to mix chyme
• Chemical digestion:
– Bile from liver breaks up large fat particles
– Digestive solution from pancreas containing
enzymes and bicarbonate ions aids digestion of
carbohydrates, proteins, and fats
– Bicarbonate ions neutralize stomach acid that is
mixed with chyme
The Small Intestine
• Entire small intestine is 4-7m long
• Villi increase surface area and allow
absorption of nutrients to take place
• Villi: fingerlike projections covering walls of
the small intestine
– Gives nutrients more places to be absorbed
• Peristalsis moves undigested and unabsorbed
materials into large intestine
The Large Intestine
• Main job: absorb water from remaining chyme
– Helps maintain homeostasis in body
• Homeostasis: regulation of an organism’s
internal, life-maintaining conditions
• Peristalsis slows down here – chyme may stay
for as long as 3 days
• Remaining undigested materials become solid
• Rectum (last section of large intestine) and
anus control release of solid waste as feces
Accessory Organs
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Tongue
Teeth
Salivary glands
Liver
Gallbladder
Pancreas
Accessory Organs in the Mouth
• Tongue: moves food around (mechanical
digestion)
• Teeth: chew food into smaller parts that can
be swallowed (mechanical digestion)
• Salivary glands: produce saliva containing
enzymes that help with the beginning of
chemical digestion
– Ex: saliva contains amylase, which breaks down
starch into simpler carbohydrates
The Liver
• Largest solid organ in the body and largest
gland in the body
• Gland: part of the body that makes and
secretes (releases) a substance
• Liver is a gland because it makes and secretes
bile, a fluid that aids digestion and transports
fats and waste
• Liver releases bile into small intestine, and bile
helps with digestion of fat and fat-soluble
vitamins (A, D, E, K)
The Liver
• Also helps store some fats and carbohydrates
• Eliminates harmful chemicals produced by the
body, such as bilirubin
• Bilirubin: harmful substance produced by the
breakdown of red blood cells
• Handles detox and removal of alcohol, drugs,
and other toxins
The Gallbladder
• Gallbladder: small organ located just below
liver that stores bile secreted by the liver
– Transports bile from liver to small intestine
• You can live without a gallbladder
– Surgery can connect liver directly to small
intestine, and a steady stream of lessconcentrated bile will flow directly from liver to
duodenum
– Less efficient but will still work
The Pancreas
• Pancreas: produces hormones that aid in
digestion, such as insulin
• Insulin: hormone that regulates the amount of
glucose (sugar) in the bloodstream and helps
break down glucose into usable energy
• Diabetes: pancreas no longer produces insulin
The Appendix
• Contains large numbers of B-cells and T-cells
• “Reboots” the digestive system by ensuring it
has the bacteria needed to protect the body
from harmful food
• Aids the immune system
• You can survive without it