digestive system function of the digestive system ingestion - taking food in digestion - the...
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Digestive System
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Function of the Digestive System
• Ingestion - taking food in
• Digestion - the mechanical and chemical breakdown of food
• Converts food into essential nutrients that are absorbed into the body
• Moves the unused waste material out of the body. waste.
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Human DIGESTIVE
system
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Mouth• Chemical and
mechanical digestion
• Food is chewed (masticated) mechanically.
• A bolus (lump) is formed with saliva and the tongue.
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Digestive Glands• Groups of
specialized secretory cells.
• Found in the lining of the alimentary canal or accessory organs.
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mouthbreak up fooddigest starchkill germsmoisten food
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Pharynx• The back of the
throat.
• Larynx- passage for air, closes when we swallow.
• Is approximately 15cm long.
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Swallowing (& not choking)
• Epiglottis – flap of cartilage– closes trachea (windpipe) when swallowing– food travels down esophagus
• Peristalsis
– involuntary muscle contractions to move food along
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Stomach• Food is temporarily
stored here.• Gastric juices are
secreted.• Has layers of muscle that
line the inside.• Mechanically and
chemically breaks down food.
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Gastric Juices• Secreted by the stomach.• Acidic (pH 1.5-2.5) (HCl).• Pepsin- an enzyme that
breaks down large proteins into amino acids.
• Food is further broken down into a thin liquid called chyme.
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stomachkills germs break up fooddigest proteinsstore food
sphincter
sphincter
mouthbreak up fooddigest starchkill germsmoisten food
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Digestive Homeostasis Disorders
• HEART BURN –
ACID from the stomach backs up into the esophagus.
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Digestive Homeostasis Disorders
• ULCERS –
erosion of the surface of the alimentary canal generally associated with some kind of irritant
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Accessory Organs
• Pancreas
• Gall Bladder
• Liver
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Pancreas
• An organ which secretes both digestive enzymes (exocrine) and hormones (endocrine)
• Pancreatic juice digests all major nutrient types.
• Nearly all digestion occurs in the small intestine & all digestion is completed in the SI.
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Pancreas • Digestive enzymes
– digest proteins• trypsin, chymotrypsin
– digest starch• amylase
• Buffers – neutralizes
acid from stomach
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Liver • Function
– produces bile• bile stored in gallbladder until needed• breaks up fats
– act like detergents to breakup fats
bile contains color from old red blood cells collected in liver =iron in RBC rusts & makes feces brown
bile contains color from old red blood cells collected in liver =iron in RBC rusts & makes feces brown
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BILE
• Bile emulsifies lipids (physically breaks apart FATS)
• Bile is a bitter, greenish-yellow alkaline fluid, stored in the gallbladder between meals and upon eating is discharged into the duodenum where it aids the process of digestion.
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Digestive Homeostasis Disorders
• GALLSTONES – an accumulation of hardened cholesterol and/or calcium deposits in the gallbladder
• Can either be “passed” (OUCH!!) or surgically removed
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Gall bladder
• Pouch structure located near the liver which concentrates and stores bile
• Bile duct – a long tube that carries BILE. The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the pancreas, through which it passes on its way to the intestine.
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pancreasproduces enzymes to digest proteins & starch
stomachkills germs break up fooddigest proteinsstore food
mouthbreak up fooddigest starchkill germsmoisten food
liverproduces bile
- stored in gall bladderbreak up fats
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Small Intestine• Most chemical digestion takes
place here.• Simple sugars and proteins are
absorbed into the inner lining.• Fatty acids and glycerol go to
lymphatic system.• Lined with villi, which increase
surface area for absorption, one cell thick.
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Small intestine• Function
– chemical digestion• major organ of digestion & absorption
– absorption through lining• over 6 meters! • small intestine has huge surface area = 300m2
(~size of tennis court)
• Structure– 3 sections
• duodenum = most digestion• jejunum = absorption of nutrients & water• ileum = absorption of nutrients & water
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Duodenum
• 1st section of small intestines– acid food from stomach – mixes with digestive juices from:
pancreas liver gall
bladder
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stomachkills germs break up fooddigest proteinsstore food
mouthbreak up fooddigest starchkill germsmoisten food
pancreasproduces enzymes to digest proteins & starch
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Absorption in the SI • Much absorption is thought to occur directly through the wall
without the need for special adaptations
• Almost 90% of our daily fluid intake is absorbed in the small intestine.
• Villi - increase the surface area of the small intestines, thus providing better absorption of materials
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Absorption by Small Intestines• Absorption through villi & microvilli
– finger-like projections– increase surface area for absorption
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VILLI
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AppendixVestigial organVestigial organ
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Digestive Homeostasis Disorders
• APPENDICITIS – an inflammation of the appendix due to infection
• Common treatment is removal of the appendix via surgery
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Large intestines (colon)
• Function– re-absorb water
• use ~9 liters of water every day in digestive juices
• > 90% of water reabsorbed– not enough water absorbed
» diarrhea
– too much water absorbed
» constipation
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Large Intestine• Solid materials pass through the
large intestine.• These are undigestible solids
(fibers).• Water is absorbed.• Vitamins K and B are
reabsorbed with the water.• Rectum- solid wastes exit the
body.
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Digestive Homeostasis Disorders
• DIARRHEA – a gastrointestinal disturbance characterized by decreased water absorption and increased peristaltic activity of the large intestine.
• This results in increased, multiple, watery feces.
• This condition may result in severe dehydration, especially in infants
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• CONSTIPATIONCONSTIPATION – a condition in which the large intestine is emptied with difficulty.
• Too much water is reabsorbed• Solid waste hardens
Digestive Homeostasis Disorders
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You’ve got company!• Living in the large intestine is a
community of helpful bacteria– Escherichia coli (E. coli)
• produce vitamins – vitamin K; B vitamins
• generate gases– by-product of bacterial metabolism – methane, hydrogen sulfide
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Rectum
• Last section of colon (large intestines)– eliminate feces
• undigested materials– extracellular waste
» mainly cellulose from plants
» roughage or fiber – masses of bacteria
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Anal Canal / Anus… Last Stop• Exit or opening for solid
wastes• Regulated by anal sphincter
(valve)• Anal sphincter surrounded by
muscles• Elimination aided by
abdominal muscles
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Hemorrhoids
Symptoms• Anal itching • Anal ache or pain,
especially while sitting • Bright red blood on
toilet tissue, stool, or
in the toilet bowl
•Very common, especially during pregnancy and after childbirth. •Result from increased pressure in the veins of the anus. The pressure causes the veins to bulge and expand, making them painful, particularly when you are sitting..
Pain during bowel movements One or more hard tender lumps near the anus
TreatmentCreamsSurgical heat therapy to shrink
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Episiotomy
This…