Transcript Chapter 12 - Biology12-Lum

Chapter 12
Digestion
The Start of Digestion
• The Mouth  Food enters here
• The Teeth  mechanically breaks down food
• The Tongue  Chemically recognizes food.
Moves food around the mouth. Assists in
swallowing
• Salivary Glands  Releases Saliva into the
mouth. Saliva starts chemical breakdown and
moistens food for swallowing.
• The Pharynx  The area in the very back of the
mouth that receives air from the nasal cavities
(air from the nose) and food from the mouth.
• Esophagus  The food tube. The tube that goes
from the mouth to the stomach. Many muscles
surround this tube to help swallow. When
muscles work to swallow its called Peristalsis
• Trachea  Tube that goes down to the lungs to
breath. This has cartridge rings so it is always
open.
• Epiglottis  covers the Trachea when swallowing
so food does not go down into the lungs.
Teeth
Nasal Cavity
Pharynx
Mouth Cavity
During swallowing
the Trachea moves
up and forces the
Epiglottis to close
over the trachea’s
opening
Swallowing
• Step 1: food is chewed in the mouth. Saliva is
added for lubrication. Saliva also contains the
digestive enzyme Salivary amylase. This enzyme
breaks down starches into disaccharides like
maltose
• Step 2: Food is turned into a Bolus ( a ball of
food) and pushed back of mouth by tongue.
• Step 3: Muscles move the bolus down the
esophagus. This is called peristalsis. The trachea
moves up and the epiglottis closes access to the
trachea. A muscle in the pharynx closes access to
the nasal cavity
Nasal Cavity
Pharynx
Epiglottis
Trachea
Esophagus
Bolus
Trachea
Into the Stomach
• The bolus moves down the esophagus and
into the stomach.
• The cardiac sphincter prevents the food from
going from the stomach back up the
esophagus.
• A sphincter is a muscle that goes around a
tube to act as a valve.
• The cardiac sphincter is located at the joining
of the stomach and the esophagus
• The stomach has many gastric glands the
release gastric juices into the stomach
• Gastric Juice Contains:
– Pepsin  enzyme breaks proteins to peptides
– HCl acid  the acid kills some bacteria, activates
pepsin, and breaks up food (but does not digest)
– Mucus  slime that covers your stomach wall to
protect it against the acid
• Muscles around the stomach help mix the
food with the gastric juices
Cardiac Sphincter
a
Into the Small Intestine
• After the stomach the pyloric sphincter opens
and lets Chyme pass on into the small
intestine
• The first part of the small intestine is called
the duodenum
• The duodenum has ducts that enter the
duodenum that release many different
chemicals
• Duodenum releases
– Bile  comes from liver. Bile is often stored in
the Gall Bladder Emulsifies fat.
– Pancreatic Juices
• Juices from the organ called the pancreas
• Sodium bicarbonate  NaHCO3 turns the acidic
chyme basic
• Pancreatic amylase  breaks down starch into
disaccharides. Enzyme.
• Trypsin  breaks down protein into peptides.
Enzyme
• Lipase  breaks down fat. Enzyme
• Nuclease  breaks down nucleic acid into
nucleotides
• The small intestine is designed to absorb
nutrients.
– It has a huge surface area. This is because the
inside of the small intestine has finger-like
projections called villi. Each villi has finger-like
projections called microvilli
• The small intestine has a thin layer of mucus
over it. Under the mucus are the villi and
microvilli. Sugars and amino acids pass
through the mucus and get moved into the
blood vessels.
Enzymes of the Small Intestine
• The small intestine has many enzymes that
work there to help let materials pass through
the wall of the small intestine
– Maltase  digests maltose into glucose
– Peptidase  digests peptides into amino acids
– Nucleosidases  digests nucleotides into bases,
sugar, and phosphate
• Amino acids, sugars, and components of
nucleotides, move into the blood by going
through the microvilli
• The parts of Fat (glycerol and fatty acids ) get
moved into the Lacteal.
• The lacteal is part of the lymphatic system.
Moving into the Large Intestine
• The Large Intestine is shorter in length but wider in
diameter
• Made up of several parts
– Ascending colon – part of colon that goes up
– Transverse colon – part of colon that goes along side
– Descending colon – part of colon that goes down
– Cecum – attached to ascending colon. Goes nowhere
– Appendix – attached to cecum. Can get infected.
– Rectum – where all the feces is stored. End of colon.
– Anus – the muscular opening to expel feces.
Transverse Colon
Ascending
Colon
Descending
Colon
Cecum
Rectum
Appendix
Anus
What happens in the Large Intestine
• The large intestine is full of bacteria. A lot the
bacteria are anaerobic bacteria.
– Anaerobic bacteria  bacteria that do not use
oxygen. Bacteria that will die in the presence of
oxygen.
• These bacteria break down indigestible
materials. They also produce some vitamins
that are then absorbed by the large intestine
wall.
• The large intestine absorbs water out of the
waste
Identify all the parts
• Salivary Glands
Review
– Salivary amylase, moistens food
• Stomach
– Gastric Juices: Pepsin, HCl, Mucus
• Pancreas
– Pancreatic Juices: NaHCO3, Trypsin, Lipase
– Insulin hormone is secreted into the blood
• This hormone tells cells in the body to take up
glucose
• This hormone is released after eating when there
is high glucose levels in the blood
• Pancreas
– Blood glucose levels are high  releases Insulin
• Insulin causes cells to take up glucose
– Blood glucose levels are low  releases Glucagon
• Tells body to break down glycogen into glucose. Glycogen is
found in the liver
• Tells body to break down fat into glycerol and fatty acids.
• Liver
=O
– Makes Bile
– Removes any poisons from the blood
– Stores Iron and many vitamins
– Stores glycogen. This can be made into glucose
– Regulates blood cholesterol levels
– Produces Urea:
• 2NH3 + CO2  H2N-C-NH2 + H2O
Optimal pH for the Enzyme
Enzyme
Location
pH
Salivary Amylase
Pancreatic Amylase
Pepsin
Trypsin
Mouth. Salivary Gland
Duodenum. Pancreas
Stomach
Pancreas. Duodenum
Neutral
Basic
Acidic
Basic
Peptidase
Nuclease
Nucleosidase
Small Intestine
Pancreas. Duodenum
Small Intestine
Basic
Basic
Basic
Lipase
Pancreas, Duodenum
Basic
SOURCE
ENZYME
FOOD
PRODUCT
MOUTH (salivary
glands)
Salivary amylase
Polysaccharides
Maltose
STOMACH
Pepsin
Proteins
Peptides
PANCREAS
Pancreatic amylase Polysaccharides
Trypsin
Proteins
Lipase
Fats
SMALL INTESTINE Maltase
Peptidases
Maltose Peptides
Maltose Peptides
Fatty acids
and glycerol
Glucose Amino
acids
FOOD TYPE
ENZYME
SOURCE
PRODUCTS
CARBOHYDRATES
Salivary amylase
Pancreatic amylase
Maltase
Salivary glands
Pancreas
Small intestine
Maltose Maltose
Glucose
PROTEINS
Pepsin Trypsin
Peptidases
Stomach mucosa
Pancreas
Intestinal mucosa
Peptides Peptides
Amino acids
FATS
Lipase
Pancreas
Fatty acids
and glycerol

Polysaccharides
Maltose 
Salivary amylase
Pancreatic Amylase
Glucose
Maltase
Name the Enzyme Involved

Proteins
Peptides
Pepsin
Trypsin
Fats

Amino Acids
Peptidase

Lipase
Glycerol + Fatty Acids
Remember to Drink lots of water