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MADE BY :
Ujali Verma
X-A
SUBMITTED TO
MR.MANOJ PATHAK
The Digestive System
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Break up, mix, and move food material
Secrete enzymes into tube where
digestion occurs
Digest (break down) food particles intosmaller molecules
Absorb nutrients and fluids Eliminate wastes and residues
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A complete system with many
specialized organs
About 6.5 to 9 meters long if extended
Lined with mucus-secreting epithelium
Movement is one way, from mouth to
anus
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Mouth (oral cavity)
Pharynx (throat)
Esophagus
GutStomachSmall intestine Large intestine RectumAnus
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Salivary glands
Secrete saliva
Liver Secretes bile
Gallbladder
Stores and concentrates bile Pancreas
Secretes digestive enzymes
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Normal adult
number is 32
molars
premolars
canines
incisors
Lower jawenamel
dentin
Figure 41.7Pa e 729
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Produced by salivary glands at back ofmouth and under tongue
Saliva includesSalivary amylase (enzyme)
Bicarbonate (buffer)
Mucins (bind food into bolus)
Water
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Complex reflex
Tongue forces food into pharynx
Epiglottis and vocal cords close off
trachea; breathing temporarily ceases
Bolus moves into esophagus, then
through esophageal sphincter into
stomach
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J-shaped organ lies
below the diaphragm
Sphincters at both ends
Outer serosa covers
smooth muscle layers
Inner layer of glandular
epithelium faces lumen mucosa
sphincters
muscle
serosa
Figure 41.9aPa e 731
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Secreted into lumen (gastric fluid)
Hydrochloric acid (HCl)
Mucus (protective) Pepsinogen (inactive form of a protein-
digesting enzyme)
Stomach cells also secrete the hormone
gastrin into the bloodstream
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A thick mixture of food
and gastric fluid
High acidity kills many
pathogens
Mixed and moved by
waves of stomach
contractions (peristalsis)
Figure 41.9bPa e 731
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High acidity of gastric fluid denatures
proteins and exposes peptide bonds
Pepsinogen secreted by stomach lining
is activated to pepsin by HCl
Pepsin breaks proteins into fragments
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An erosion of the wall of the stomachor small intestine
Can result from undersecretion ofmucus and buffers, or oversecretionof pepsin
Most ulcers involve Helicobacterpylori bacteria and can be treatedwith antibiotics
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Movement into duodenum controlled
by pyloric sphincter
Only a small amount of chyme passes
through sphincter at a given time
Fat content of chyme affects the rate ofstomach emptying
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Wall of the duodenum secretes
Disaccharidases - digest
disaccharides to monosaccharides Peptidases - break protein fragments
down to amino acids
Nucleases - digest nucleotides downto nucleic acids andmonosaccharides
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Secreted into duodenum
Pancreatic amylase
Trypsin and chymotrypsin
Carboxypeptidase
Lipase
Pancreatic nucleases
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Liver produces bile
Bile is stored in gallbladder, then
secreted into duodenum Bile emulsifies fats; breaks them into
small droplets
This gives enzymes a greater surfacearea to work on
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Gastrin
Secretin
Cholecystokinin (CCK)
GIP (glucose insulinotropic peptide)
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Projections into
the intestinal
lumen increase
the surface area
available for
absorption
One villus
Figure 41.10Pa e 733
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Passage of molecules into internal
environment
Occurs mainly in jejunum and ileum ofsmall intestine
Segmentation mixes the lumen contents
against wall and enhances absorption
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Monosaccharides &
amino acids are
actively transportedacross plasma
membrane of
epithelial cells, then
from cell into internal
environment
Figure 41.11Pa e 734
INTESTINAL LUMEN
carbohydrates monosaccharides
EPITHELIALCELL
INTERNAL
ENVIRONMENT
proteins amino acids
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bilesalts
+
fat globules(triglycerides)
fatty acids,monoglycerides
emulsificationdroplets
micelles
chylomicrons
triglycerides + proteins
bile salts
EPITHELIALCELL
INTERNAL ENVIRONMENTFigure 41.11Page 734
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Glucose and amino acids enter blood
vessels directly
Triglycerides enter lymph vessels, which
eventually drain into blood vessels
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Food intake
POOL OF CARBOHYDRATES AND FATS POOL OF AMINO ACIDSNH3
structuralcomponents
of cells
storageforms
specializedderivatives
(e.g., steroids,acetylcholine)
used ascellularenergysource
urea
nitrogen-
containingderivatives
(e.g., hormones,nucleotides)
componentsof structural
proteins,enzymes
some surfacesecretion, cell
sloughing
cellactivities
excreted asCO2 via lungs
excretedin urine
cellactivities
some cellsloughing
dietary proteins, amino acidsdietary carbohydrates, lipids
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Concentrates and
stores feces
Sodium ions are
actively transported out
of lumen and water
follows
Lining secretes mucus
and bicarbonate
ascendingportion oflarge intestine
appendixcecum
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Slow movement of material through
colon allows growth of bacteria
Harmless--unless they escape into
abdominal cavity
Some produce vitamin K, which is
absorbed through intestinal wall
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During a meal, gastrin and autonomic
signals trigger contraction of ascending
and transverse colon
Material moves along to make room for
incoming food
Feces is stored in last part of colon
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Distension of the last part of the colon
triggers a reflex action
Smooth muscle of anal sphincter relaxes
Voluntary contraction of external
sphincter can prevent defecation
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Appendicitis
Constipation
Colon cancerSymptoms include blood in feces
Can be caused by a genetic defect
Low-fiber diet is a predisposingfactor
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bread, cereal, rice,pasta group
fruit group vegetable group
legume, nut, poultry,fish, meat group
milk, yogurt,cheese group
added fats andsimple sugars
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Bodys main energy source
Foods high in complex carbohydrates
are usually high in fiber; promotecolon health
Simple sugars lack fiber as well as
minerals and vitamins of whole foods;intake should be minimized
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Most fats can be synthesized
Essential fatty acids must be obtained
from food Fats should be about 30 percent of diet
Excess saturated fats can raise
cholesterol level and contribute to heartdisease
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Body cannot build eight of the twentyamino acids
These essential amino acids must beobtained from diet
Animal proteins are complete; supply allessential amino acids
Plant proteins are incomplete; must becombined
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Vitamins
Essential organic substances Minerals
Essential inorganic substances
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Fat soluble
Excess
accumulates intissue
Vitamins A, D,
E, K
Fat insoluble
B vitamins
Pantothenic acid
Folate
Biotin
Vitamin C
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Calcium Magnesium
Chloride Phosphorus
Copper Potassium
Fluorine Sodium
Iodine Sulfur
Iron Zinc
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Increasing numbers of Americans
are obese
Obesity-related conditions
Type 2 diabetes Breast cancer
Heart disease Colon
cancer
Hypertension GoutGallstones Osteoarthritis
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An indicator of obesity-related healthindex
BMI = Weight (lbs) X 700
-----------------------------Height (inches)2
BMI greater than or equal to 27indicates health risk
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Caloric input must equal caloricuse
Calories burned depends uponActivity level
Age
Height and build
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Hormone that affects appetite andmetabolic rate
Product of the Ob gene
Faulty Ob gene may contribute to somehuman obesity
Effects of leptin on bone may
complicate use of leptin to treat obesity
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Newly discovered peptide hormone
Secreted mainly by cells of the stomach
lining Directly stimulates the appetite control
center
Makes you feel hungry