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8th Grade 118: The Digestive System

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Nicole Beattie

on 8 April 2013

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Transcript of 8th Grade 118: The Digestive System

mouth the opening through which humans take in food
pH is neutral
beginning of the digestive tract
chewing takes place to break down food to be digested easier
includes teeth and tongue teeth structures found in the mouth, attached to the jaw in rows
grind together to break down food during chewing tongue movable organ in the floor of the mouth
helps move food around during chewing, so food is evenly broken down
allows humans to swallow food
coats food in saliva to help digestion in the stomach salivary glands any gland that secretes saliva, found in and around the mouth and throat
secrete saliva into the mouth
help initiate digestion
3 pairs: sides of the face, beneath the tongue, beneath the floor cavity pharynx tube or cavity that connects the mouth to the esophagus
acts as a passageway for food to the stomach epiglottis a flap at the base of the throat, open when swallowing occurs
prevents food from falling down the airway and into the respiratory system esophagus found in the throat near the trachea
receives food from the mouth after swallowing
muscular contractions deliver food to the stomach cardiac sphincter located in between the end of the esophagus and the entrance to the stomach
keeps food in the stomach for digestion
prevents food from returning into the esophagus pyloric sphincter located at the base of the stomach, it is the contracting ring of muscle guarding the entrance to the small intestine
keeps the stomach shut so that it can digest and then opens allowing the contents into the next stage stomach a hollow organ that stores, dilutes, and digests food
-mechanical digestion:
churns and mixes food with acid and gastric juice
-chemical digestion
enzymes duodenum the first section of small intestine
responsible for the breakdown of food in the small intestine, using enzymes
regulates the rate of emptying the stomach liver large organ located above and in front of the stomach
breaks down hemoglobin to bilirubin and biliverdin to be excreted along with bile salts in bile
produces bile
detoxifies blood
stores and releases glucose (store as glycogen)
breakdown amino acids to produce urea
makes blood proteins gallbladder small sac-shaped organ below the liver
stores and concentrates bile, then releases it to the duodenum pancreas large gland behind the stomach
secretes digestive enzymes into the duodenum
secretes insulin and glucagon to keep the blood glucose levels normal small intestine narrow, winding, upper part of the intestine
absorbs nutrients into capillary networks surrounding the small intestine appendix small projection off the cecum
may play a role in fighting infections large intestine lower section of the intestine that extends from the end of the small intestine to the anus
includes the cecum, colon, rectum, and anal canal
absorbs water, salts, some vitamins
store indigestible material until elimination rectum the final section of the large intestine, ending into the anus
stores feces until elimination anus the opening at the rectum
where solid waste is eliminated from the body swallowing: the soft palate closes off the nasopharynx, and the epiglottis covers the glottis, forcing the bolus to pass down the esophagus peristalsis: rhythmic contraction
pushes food along the digestive tract
begins in the esophagus and continues in all organs of the digestive tract insulin insulin is secreted when there is a high level of glucose in the blood
it stimulates liver, fat and muscle cells to take up glucose from the bloodstream and metabolize glucose for energy
stimulates liver and muscles to store glucose as glycogen
promotes buildup of fats and proteins, as energy source bile derived from the breakdown of hemoglobin
contains bile salts (derived from cholesterol) which emulsify fat in the small intestine
when fat is emulsified, it breaks into droplets which provide a larger surface area ducts from the liver and pancreas join to form one duct that enters the duodenum
small intestine receives bile from the liver and pancreatic juices from the pancreas from the duct
bile-emulsifies fat
pancreatic juice-contains sodium bicarbonate to neutralize chyme
enzymes from in pancreatic juice and enzymes from intestinal wall complete digestion process chemical digestion: physical digestion/absorption: small intestine surface area is approximately equal to that of a tennis court
6 meters in length
wall contains fingerlike projections called villi (villus as a singular), giving wall a soft appearance
a villus has an outer layer of columnar epithelial cells, each having thousands of extensions called microvilli, giving the villi a "brush border"
microvilli increase the surface area for absorption villi fingerlike projections on the wall of the small intestine
has an outer layer of columnar epithelial cells, each having thousands of microvilli creating the "brush border"
microvilli bear the intestinal enzymes, called brush border enzymes
nutrients are absorbed into the vessels of the villus
villus contains blood capillaries and a small lymphatic capillary called the lacteal
sugars and amino acids enter blood capillaries
glycerol and fatty acids enter epithelial cells and are joined and packaged as lipoprotein droplets which enter the lacteal
nutrients are absorbed then carried to cells through the bloodstream (sing. villus) colon contains anaerobic bacteria
bacteria make up a large part of solid feces
break down indigestible matieral
produce some vitamins and other molecules that can be absorbed salivary amylase produced by salivary glands
acts in the mouth
-begins digestion of starch
starch + H2O --> maltose pancreatic amylase produced by the pancreas
acts in the small intestine
-digests starch
starch + H2O --> maltose maltase produced by the small intestine
acts in the small intestine
-digests maltose
maltose + H2O --> glucose + glucose pepsin produced by gastric glands
acts in the stomach
-digests protein
protein + H2O --> peptides pepsin pancreatic amylase maltase trypsin produced by the pancreas
acts in the small intestine
-digests protein
protein + H2O --> peptides trypsin peptidases produced by small intestine
acts in the small intestine
-digests peptides
peptide + H2O --> amino acids peptidases nuclease produced by the pancreas
acts in the small intestine
-digests RNA and DNA
RNA and DNA + H2O --> nucleotides nucleosidases produced by the small intestine
acts in the small intestine
-digests nucleotides
nucleotide + H2O --> base + sugar + phosphate lipase produced by the pancreas
acts in the small intestine
-digests fat droplets
fat droplet + H2O --> glycerol + fatty acids nucleosidases lipase salivary amylase pepsinogen produced by the stomach
acts in the stomach
-digests protein
pepsinogen exposed to hydrochloric acid becomes pepsin use of water in digestion 1. hydrolysis
digestive enzymes are hydrolytic and need water to react
2. moisten and lubricate food
through saliva
important for movement through the intestines
3. main component of gastric and pancreatic juices pancreatic cells produce pancreatic juice, which contains sodium bicarbonate and digestive enzymes
sodium bicarbonate neutralizes acid chyme from the stomach hydrochloric acid (HCl) found in gastric juice
released by parietal cells, and when mixed with pepsinogen makes pepsin
HCl causes the stomach to have a high acidity with a pH of 2; this kills most bacteria in the food
HCl does not digest food, but breaks down the connective tissue of meat and activates pepsin the walls of the stomach are lined with a thick layer of mucus, secreted by the mucous cells
protects stomach from its own acid
prevent the HCl from penetrating the wall
if HCl gets past the mucus, then an ulcer forms jejunum ileum ascending colon transverse colon descending colon The Digestive System By: Tanitia Eggert whole wheat pasta
tomato sauce
turkey meatballs
salad with vegetables
water dinner time! the pasta begins to be digested all food begins to be broken down the meatballs begin to be digested pasta continues to be digested fat found in the meatballs begins to be digested meatballs continue to be digested pasta is digested and absorbed into small intestine meatballs are digested and absorbed into the small intestine fat is digested and absorbed in the small intestine food enters the mouth, and the digestion process begins the salivary glands send saliva into the mouth, the teeth chew the food, and the tongue forms it into a bolus for swallowing the bolus moves to the pharynx the food then travels down the esophagus and continues to move into the stomach the food moves from the stomach, now in the form of chyme, to the small intestine through the duodenum food then moves into the small intestine the duodenum receives bile from the liver and pancreatic juices from the pancreas, which enter the small intestine there are three parts of the small intestine, in which food travels through, the first was the duodenum then the... lastly, the... then the food travels to the large intestine off the large intestine is the appendix there are two sphincters in the stomach there are different parts of the large intestine as well, that the food travels through food travels through the large intestine, and enters the rectum the final step is for the food to be eliminated out the anus Appendicitis inflammation of the appendix
occurs when the opening of the appendix to the large intestine gets blocked; blockage can be a result from hard rock-like stool What is it? What happens? once appendix is blocked it becomes inflamed and bacteria can overgrow it
if the infected appendix is not removed then it may rupture or burst Symptoms... abdominal pain and loss of appetite
pain begins in the center of the abdomen then moves further down and to the right
once pain begins, the individual may develop a fever, loss of appetite, feel nauseated or vomit Treatment... treated with surgery by removing the infected appendix
appendectomy (name of operation) How to prevent it... eat foods high in fiber to prevent hard rock-like stool
avoid foods low in fiber glucagon glucagon is secreted when there is a low level of glucose; in between eating, during fasting
it is the opposite effect of insulin
conversion of glycerol (from fats) and amino acids to glucose
stimulates breakdown of stored nutrients so the blood glucose levels will rise during periods of starvation hormones are also used during the digestion process, to promote secretion of digestive juices produced by the lower part of the stomach and the upper part of the small intestine
made in response to protein
targets upper portion of stomach
releases more pepsinogen
starts stomach churning Gastrin:
produced by the small intestine
made in response to acid and fats in the small intestine
targets the pancreas
reduces production of gastric juices in the stomach
slows food movement out of the stomach
causes the pancreas to secrete more sodium bicarbonate and enzymes Secretin:
Cholecystokinin (CCK): produced in the small intestine
made in response to acid and fats in the small intestine
targets the liver
reduces gastric juices
slows food movement out of stomach
causes liver to secrete more bile Gastric Inhibiting Peptide (GIP): produced in the small intestine
made in response to acid and fats in the small intestine
targets the stomach and duodenum
reduces gastric juices
slows down movement out of stomach
opposite of Gastrin the small intestine has a slightly basic pH because pancreatic juice contains sodium bicarbonate which neutralizes chyme Works Cited: Inquiry into Life (Biology textbook)
Digestive System-class notes
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