Transcript PP Human Digestive System

Watch Pod Cast overview of
digestive system 10 mins CLICK
mouth
salivary glands
pharynx
epiglottis
oesophagus
liver
gall bladder
duodenum
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
anus
mouth
salivary glands
pharynx
epiglottis
oesophagus
liver
gall bladder
duodenum
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
anus
mouth
salivary glands
pharynx
epiglottis
NUTRIENTS
•
Carbohydrates  glucose
•
Lipids  fatty acids & glycerol
oesophagus
liver
•
Proteins  amino acids
gall bladder
•
Nucleic acids  nucleotides
duodenum
•
Vitamins
•
Minerals
•
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
Water
anus
MOUTH
pH 5.6 to 7.9 usually neutral to slightly alkaline
mouth
•Ingestion: taking food into mouth
salivary glands
• Teeth-Masticate: mechanically break
up food into smaller pieces (increasing
surface area for action of enzymes)
• Salivary Glands
• Saliva: enzyme: salivary amylase
liver
(ptyalin) begins starch digestion
gall bladder
: moistens food
•Tongue – rolls food into a bolus and
duodenum
moves it to back of throat for
swallowing
ileum/jejunum
•Epiglottis covers trachea to stop food
caecum
going down the trachea
appendix
•Soft palate covers nasal passage to
stop food going up the nose
anus
•Alcohol can be absorbed
pharynx
epiglottis
oesopha
stomach
pancrea
colon
rectum
L.S throat region of human
hard
palate
soft palate
tongue
oesophagus
trachea
Swallowing process
OESOPHAGUS
mouth
•peristalsis: wave like
muscular contractions
that move food along
You can eat standing
on your head…but
don’t try it!
salivary glands
pharynx
epiglottis
oesophagus
liver
•Mucus produced
which lubricates
oesophagus wall to
help food slide down
•No enzymes produced
•No absorption
gall bladder
duodenum
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
anus
Peristalsis
Peristalsis
To start Play
stomach clip
mouth
salivary glands
pharynx
epiglottis
oesophagus
liver
gall bladder
duodenum
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
anus
STOMACH pH 1-2
• Cardiac & Pyloric sphincters : cardiac: stops food rising in the oesophagus
pyloric: regulates the release of small quantities of chyme into the duodenum
• Storage: of food between meals
• 3- Layers of muscle:
•Churning and mixing of food
• Inner glandular layer: produces..
• GASTRIC JUICE
• hydrochloric acid
• Protease: produced in inactive from and is acidic environment of stomach
becomes the active enzyme pepsin:
pepsinogenpepsin
•Pepsin initiates protein digestion (proteins  peptides)
• Mucous: coating the stomach lining protects it from acid damage or digestion
• Heart burn & ulcers
• When food leaves stomach it is in a soupy consistency called CHYME
Gastric Ulcer
A word about Chemical
digestion of lipids
Most resources focus on the role of bile salts and pancreatic lipase in the
digestion of lipids and say lipid digestion begins in the duodenum. This isn’t
actually correct.
In 1973 it was discovered that glands in the tongue secrete some lipase into
the mouth where it mixes with food and which acts in the acid environment of
the stomach.
There is also gastric lipase secreted from cells lining the stomach. (gastric
lipase is mentioned in your text book)
However digestion by the lipase in the mouth and stomach is minor(about 30%)
in comparison to what happens in duodenum and is ignored by most resources
SMALL INTESTINE: Duodenum
pH-6-7
CHEMICAL BREAKDOWN of
Carbohydrates, peptides
mouth
salivary glands
pharynx
epiglottis
Lipids, nucleic acids
Cells in intestinal lining secrete some enzymes
oesophagus
Pancreas secretes
liver
•Bicarbonate: helps neutralize chyme
gall bladder
•Enzymes to complete digestion of biomolecules
Lipase, amylase, trypsin &
chymotrypsin
,
duodenum
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
anus
SMALL INTESTINE: Duodenum
CHEMICAL BREAKDOWN
Liver
• produces bile
• Bile is NOT an ENZYME
• emulsifier of lipids
•Also helps neutralize chyme
Emulisifaction
SMALL INTESTINE: Ileum
pH 7-8
mouth
• Absorption of nutrients and most water
salivary glands
• Villi and microvilli provide an extremely
large surface area across which nutrients
are absorbed
• rich blood supply and lacteals;
pharynx
epiglottis
oesophagus
liver
gall bladder
duodenum
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
anus
Absorbed into blood supply
via capillary
glucose
amino
acids
Absorbed into lymph
via lacteal
fatty acids
glycerol
Fatty acids and mono glycerides resulting from fat
digesion form micelles in the lumen of small intestine
EXTENSION ONLY
1. Products of fat digestion leave micelles and enter
intestinal lining cell via diffusion
2. Fatty acids used to synthesise triglycerides in S.E.R
3. Fatty globules combine with proteins with golgi
body to form chylomicrons
4. Vesicles containing chylomicrons move to membrane
and leave the intestinal cell by exocytosis
5. Chylomicrons enter lacteal and are
transported away from the intestines in
the lymph
LARGE INTESTINE: COLON
• First part Caecum (enlarged in herbivores)
mouth
• Some (limited) breakdown of fibre
salivary glands
• Second part Colon (3 parts)
• Absorption of water, vitamins, minerals
epiglottis
oesophag
• Synthesis of some vitamins by bacteria
• waste becomes more solid
pharynx
liver
gall bladder
duodenum
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
anus
LARGE INTESTINE: RECTUM
• STORAGE
mouth
salivary glands
pharynx
epiglottis
oesophagus
liver
ANUS
gall bladder
• EGESTION
duodenum
ileum/jejunum
stomach
pancreas
colon
caecum
appendix
rectum
anus