BIOL&253Ch24NotesFall11

BIOL&253Ch24NotesFall11 - Ch. 24 The Digestive...

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1 Fig. 24-1, p. 876 Ch. 24 – The Digestive System • The overall idea is to obtain nutrients from the environment • There are 2 general types of digestive organs involved: – 1. Parts of the digestive tract (= a long muscular tube from the mouth to the anus) • This is a.k.a. the gastrointestinal (GI) tract or alimentary canal • It’s made up of the oral cavity (mouth), pharynx, esophagus, stomach, small intestine, and large intestine • Food passes through these –2 . Accessory organs = the teeth, tongue, salivary glands, liver, gallbladder, and pancreas • Food does not pass through these The general functions of the digestive system •1 . Ingestion = eating •2 . Mechanical processing (e.g. by the teeth and stomach) = crushing, shearing, and mixing – This increases the surface area on food particles for attack by enzymes – Smaller pieces are easier to move •3 . Digestion = chemical breakdown (usually by enzymes) –P r o t e i n s amino acids – Triglycerides glycerol + fatty acids – Polysaccharides monosaccharides •4 . Absorption
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2 Fig. 24-1, p. 876 An overview of specific digestive organ functions The peritoneum and mesenteries We’ve previously learned about the parietal peritoneum, visceral peritoneum (serosa), and peritoneal cavity (in our discussion of serous Mesenteries = double sheets of peritoneal membrane that connect the parietal peritoneum to the visceral peritoneum – Function : stabilize and provide a route for N.A.V.a.L to the abdominopelvic organs Fig. 24-2b-c, p. 878
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3 Fig. 24-3, p. 879 The general histology of the GI tract Most parts of the tube have most (if not all) of these features • Additional details are found in the textbook and on p. 16 of the Lab Manual Lumen (interior) Exterior An example of the general histology of the GI tract: the duodenum of the small intestine Lumen (interior) Serosa not shown
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Fig. 24-4, p. 880 The movement of digestive materials • The muscular layers of the GI tract have gap junctions between cells and pacesetter cells that spontaneously depolarize – They can also be stimulated by the ANS Peristalsis = waves of rhythmic contractions that propel the “food mass” (= bolus ) forward through the tract Segmentation (not shown at right) = irregular contractions in the intestines that mix/churn/fragment the bolus Fig. 24-5, p. 881 The regulation of digestive activities At least 18 different ones! (E.g. gastrin, secretin, etc.) We’ll discuss some of the main ones later in the chapter.
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BIOL&253Ch24NotesFall11 - Ch. 24 The Digestive...

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