Thursday, January 14 th, 2010 DAILY QUIZ #1 You will need a sheet of lined paper + pen/pencil Clear off desk Put up a binder/text between person next to you Put your NAME & PERIOD at the top of sheet

Daily Quiz #1 1.a) This nutrient is used in our bodies as a quick source of energy. b) Give one food source you can obtain it from. 2.Give one reason for chewing. 3.What is the function of salivary amylase? 4.Give one example of how your body ensures that a food bolus enters the esophagus. 5.What is the term used to describe the rhythmic contractions of the esophagus? 1-1

Daily Quiz #1 1.a) This nutrient is used in our bodies as enzymes. b) Give one food source you can obtain it from. 2.Give one example of mechanical digestion. 3.Why is the phrase “Salivary amylase digests disaccharides” incorrect? 4.Give one example of how your body ensures that a food bolus enters the esophagus. 5.What is the term used to describe the rhythmic contractions of the esophagus? 1-2

Daily Quiz #1 1.a) This nutrient is used in our bodies as a “cushion” for our organs. b) Give one food source you can obtain it from. 2.Where does chemical digestion FIRST occur?. 3.What does salivary amylase digest? 4.Can you breathe while swallowing? Explain. 5.What is the term used to describe the rhythmic contractions of the esophagus? 1-4

The Digestive System …cont’d Thursday, January 14 th, 2010

Esophagus  Stomach Food bolus travels down esophagus  arrives at cardiac sphincter (muscles around opening to stomach)  valves that open when relax & close when contract  normally, this sphincter prevents food from moving up out of stomach, but when vomiting occurs, a reverse peristaltic wave causes the sphincter to relax and contents of stomach are propelled outward

The Stomach a thick-walled, J-shaped organ that lies on left side of the body beneath the diaphragm can stretch to hold 2-4L of solids/liquids in an average adult (baby stomach holds 60 mL, cow stomach holds 300L) 2 sphincter muscles: cardiac (closer to heart) and pyloric sphincter ( into small intestine)

The Stomach 3 layers of muscle contract to churn and mix contents pacemaker cells at top of stomach stimulate contractions at rate of 3/minute  fuller the stomach, the more peristalsis /data/animals/008/index.html

Cells of Stomach Lining the mucus lining of the stomach contains inner GASTRIC GLANDS which produce GASTRIC JUICE. 3 types of stomach cells: Mucus cells – secrete a protective coat (mucus) Parietal cells – secrete HCl (pH 3) to kill bacteria and help break food down Peptic cells – secrete pepsinogen

Protein Breakdown in the Stomach In the presence of HCl, pepsinogen forms PEPSIN, a HYDROLYTIC ENZYME that breaks down proteins into smaller chains of amino acids called peptides. (Note: peptides are further broken down into individual amino acids by other enzymes later on) pepsin 2 protein + H 2 O > peptides

Think About It Why doesn’t the stomach digest itself?

Why Doesn’t the Stomach Digest Itself? 1)Mucus layer prevents HCl from eating through 2)HCl not formed until it crosses the stomach lining 3)Pepsin could digest protein in stomach cells, but it is INACTIVE until mixes with HCl

Gastric Ulcers Lesions in the stomach lining – Are caused mainly by the bacterium Heliobacter pylori Figure µm Bacteria Mucus layer of stomach assets/img/gastro/Gastric_Ulcer.jpg

Animations + Quizzes hill.com/classware/ala.do?isbn= & alaid=ala_996429&showSelfStudyTree=true Hydrochloric Acid Production… of the Stomach Ch 41 hill.com/classware/ala.do?isbn= & alaid=ala_996429&showSelfStudyTree=true hill.com/classware/ala.do?isbn= & alaid=ala_996426&showSelfStudyTree=true Hormones ad Gastric Secretion Ch 41 hill.com/classware/ala.do?isbn= & alaid=ala_996426&showSelfStudyTree=true

Supplementary Articles Fat Vaccine &article_id= &article_id= Fat microbes &article_id= &article_id= Hunger hormone &article_id= &article_id= Fat and exercise &article_id= &article_id=

The Small Intestine Most of digestion (enzymatic hydrolysis of food) and absorption of nutrients occur in the small intestine. About 6 m in length, tapers from about 3cm in diameter at the pyloric sphincter to about cm at the ileocecal valve (where joins large intestine)

Made up of 3 major sections: Duodenum: cm long, receives food from stomach, receives bile and pancreatic juice through the common duct about 10 cm along from the stomach  site of most active enzyme production and digestion Jejunum: m long, has fewer intestinal glands, more specialized for absorption. Ileum: 4-5 m long, produces no enzymes but does most of the absorption The Small Intestine

The large surface area of the SI (about 300 m 2 ) is the result of several levels of folding: The lining of the small intestine is not smooth: Circular folds in the submucosa slow the passage of food and increase the area. They are covered with... Villi, millions of microscopic fingerlike projections which are, in turn, covered with... Microvilli, tiny cytoplasmic projections from the surface of individual columnar epithelial cells.

20 Circular folds  Villi  Microvilli

The enormous microvillar surface is an adaptation that greatly increases the rate of nutrient absorption Epithelial cells Key Nutrient absorption Vein carrying blood to hepatic portal vessel Villi Large circular folds Intestinal wall Villi Epithelial cells Lymph vessel Blood capillaries Lacteal Microvilli (brush border) Muscle layers Figure 41.23

Structure of a Villus 1.An outer layer of columnar epithelial cells: - some cells covered in microvilli for absorption - some are glandular cells which produce and release enzymes or mucus into the intestinal lumen - some have digestive enzymes bound to their outer membrane

Structure of a Villus 2. A layer of blood capillaries that absorb the sugars and amino acids and carry them back towards the mesenteric blood vessels, the hepatic portal vein and the liver

Structure of a Villus 3. A small blind-ended lymph vessel called the lacteal that returns fluids and lipoprotein droplets to the blood stream

Functions of the Small Intestine 1. Neutralize acidity of stomach contents with bicarbonate from pancreas 2. Mechanically mix the chyme with pancreatic juice, bile and intestinal secretions 3. Continue the breakdown of food 4. Absorb simple sugars and amino acids into the blood by active transport (requires ATP)

The first portion of the small intestine is the duodenum – Where acid chyme from the stomach mixes with digestive juices from the pancreas, liver, gallbladder, and intestine itself Enzymatic Action in the Small Intestine Figure LiverBile Acid chyme Stomach Pancreatic juice Pancreas Intestinal juice Duodenum of small intestine Gall- bladder

Accessory Organ - Pancreas Produces proteases (protein-digesting enzymes) that are activated once they enter the duodenum -Trypsinogen  Trypsin Peptidase Amylase Lipase Nuclease Pancreas Membrane-bound enteropeptidase Trypsin Active proteases Lumen of duodenum Inactive trypsinogen Other inactive proteases Figure 41.20

Chemical Breakdown in the SI

hill.com/classware/ala.do?isbn= & alaid=ala_996426&showSelfStudyTree=true Enzyme Action and the Hydrolysis of Sucrose Brooker Ch 41 hill.com/classware/ala.do?isbn= & alaid=ala_996426&showSelfStudyTree=true

Oral cavity, pharynx, esophagus Carbohydrate digestion Polysaccharides (starch, glycogen) Disaccharides (sucrose, lactose) Salivary amylase Smaller polysaccharides, maltose Stomach Protein digestion Nucleic acid digestion Fat digestion Proteins Pepsin Small polypeptides Lumen of small intes- tine Polysaccharides Pancreatic amylases Maltose and other disaccharides Epithelium of small intestine (brush border) Disaccharidases Monosaccharides Polypeptides Pancreatic trypsin and chymotrypsin (These proteases cleave bonds adjacent to certain amino acids.) Smaller polypeptides Pancreatic carboxypeptidase Amino acids Small peptides Dipeptidases, carboxypeptidase, and aminopeptidase (These proteases split off one amino acid at a time, working from opposite ends of a polypeptide.) Amino acids DNA, RNA Pancreatic nucleases Nucleotides Nucleotidases Nucleosides Nucleosidases and phosphatases Nitrogenous bases, sugars, phosphates Fat globules (Insoluble in water, fats aggregate as globules.) Bile salts Fat droplets (A coating of bile salts prevents small drop- lets from coalescing into larger globules, increasing exposure to lipase.) Pancreatic lipase Glycerol, fatty acids, glycerides Enzymatic digestion is completed as peristalsis moves the mixture of chyme and digestive juices along the small intestine Figure 41.21

What happens to the food we eat? Supplementary Reading =faq&dbid=16#dig5

Absorption Occurs in the jejunum and to a lesser extent in the ilieum

Absorption Amino acids and sugars – Pass through the epithelium of the small intestine and enter the bloodstream Glycerol and fatty acids are absorbed by epithelial cells – Where they are recombined into fats within these cells

These fats are then mixed with cholesterol and coated with proteins – Forming small molecules called chylomicrons, which are transported into lacteals Figure 41.24

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Learning Log describe how the small intestine is specialized for chemical & physical digestion & absorption describe the structure of the villus, including microvilli, & explain the functions of the capillaries & lacteals within it relate specific digestive enzymes to their glandular sources & describe the digestive reactions they promote