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What molecule does our body break down for energy? Where do we get this molecule? Recall from Biology Lab, what do Iodine and Benedict’s solution test.

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Presentation on theme: "What molecule does our body break down for energy? Where do we get this molecule? Recall from Biology Lab, what do Iodine and Benedict’s solution test."— Presentation transcript:

1 What molecule does our body break down for energy? Where do we get this molecule? Recall from Biology Lab, what do Iodine and Benedict’s solution test for? Explain the reactions of these two indicators. DO NOW:Digestive Enzymes Pre-Lab

2 Objectives To use your knowledge of indicators and macromolecules to determine the effects of digestive enzymes. To explain how digestion begins in the mouth.

3 Do Now What do we already know about the digestive system? List 3 things! What would happen if you were tied upside down, would you still be able to eat? Explain.

4 The Digestive System! Chapter 15

5 Objectives To compare and contrast chemical vs. mechanical digestion. To explain the general characteristics of the alimentary canal. To explain the process of swallowing and peristalsis. To identify the structures of the mouth and explain their function. To understand the necessity of salivary glands and name each type.

6 Digestion Chemical digestion- complex molecules are broken down into smaller molecules Mechanical digestion- physical movement of food that breaks it down into smaller pieces – Ex. Chewing, grinding, mashing – Chewing is called “mastication”

7 Components of Digestive System Alimentary Canal – “digestive tract” – Mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anal canal Accessory Structures: – Salivary glands, liver, gallbladder, & pancreas

8 Alimentary Canal Muscular tube that passes through the body’s ventral cavity 9 meters long Contains 4 layers

9 Alimentary Canal 1)Mucosa: – Protects the tissues beneath it & carries out secretion and absorption – Consists of epithelium, underlying CT, and a little bit of muscle. 2) Submucosa: – Nourishes surrounding tissue and carries away absorbed materials – Consists of loose connective tissue, blood vessels, glands.

10 Alimentary Canal 3) Muscular Layer: – Layer which moves the tube – Contains: Two coats of smooth muscle tissue & nerves (plexus) – Fibers of the inner coat surround the tube When they contract the tube’s diameter decreases – Fibers on the outer muscular coat run lengthwise When they contract the tube shortens 4) Serosa: – Protects underlying tissues and secrete serous fluid

11 Alimentary Canal

12 Movements of theAlimentary Canal Mixing Movement – Occurs when smooth muscle in small units of the tube contract rhythmically – Mixes food with digestive juices secreted by the mucosa Propelling Movement – Known as peristalsis

13 Organs of the Digestive System The Mouth Receives food and begins digestion mechanically Reduces the size of solid particles and mixes them with saliva Oral cavity - Lips, cheeks, tongue & palate Vestibule - Narrow space between teeth, cheeks, & lips

14 Salivary Glands Secrete saliva Contain 2 cells –Serous cells: produce amylase (breaks down carbs) –Mucus cells: produce mucus to bind to food and lubricate during swallowing.

15 Pharynx Connects nasal and oral cavities Contains 3 parts –Nasopharynx –Oropharynx –Laryngopharynx (passageway to the esophagus)

16 Swallowing Mechanism 1.Food is chewed and mixed with saliva,tongue rolls this into a mass or bolus and forces it into the pharynx 2.Food stimulates sensory receptors around the pharyngeal opening triggering the swallowing reflex. 3.Momentarily inhibits breathing, peristalsis transports food into the esophagus and to the stomach.

17 Do Now 1) Read the story about William Beaumont and his work with St. Martin in the early 1800s. 3) Write a short summary of what you read.

18 Objectives Explain the functions of the esophagus, stomach, small intestines, and large intestines in digestion. Identify different enzymes located in the digestive system and explain their function. Understand different conditions caused by improper functioning of the digestive system.

19 Swallowing Mechanism

20 Esophagus About 25 cm long Connects pharynx to the stomach Separated from the stomach by the cardiac sphincter. Contracts and closes the sphincter to prevent regurgitation.

21 Heartburn! Regurgitation of stomach acid into the esophagus.

22 Stomach J shaped with about a 1 liter capacity. Contains rugae which allow it to expand Divided into 4 regions –Cardiac –Fundic –Body –Pyloric


24 Stomach

25 Stomach Ulcers Breaking down of the mucosal lining.

26 Stomach Juices “Gastric Juice” consists of… –HCl –Mucus –Viscous alkaline secretion that coats the stomach –Enzymes Proteases such as Pepsin- digests protein (starts as pepsinogen and when mixed with HCl makes pepsin) –Intrinsic factor which helps the small intestine absorb B12

27 Stomach Juices The mixture of gastric juice and the bolus gives us chyme. Stomach contractions push chyme a little at a time into the sm. Intestine. Type of food can effect rate of emptying –Fatty food = 3-6 hrs. in stomach –Proteins move more quickly –Carbs go through the fastest!

28 Gastric Absorbtion The stomach mostly breaks things down Can absorb only small amounts of water, certain salts, alcohol, and some lipid-soluble drugs. –EX: Aspirin

29 Pancreas Secretes pancreatic juice into the duodenum (1 st part of sm. Intestine) Pancreatic enzymes: –Pancreatic amylase Digests carbs –Pancreatic lipase Digests fats –Nucleases Digests nucleic acids –Proteases: trypsin, chymotrypsin & carboxypeptidase Digest protein

30 Liver Effects carbohydrate, lipid, and protein metabolism. Produces bile –Contains bile salts, bile pigments (bilirubin and biliverdin) –**bile salts emulsify fats (turn them into little globs instead of big globs!) and also increase absorption of fat-soluble vitamins (A,D,E, & K)

31 Review What is the process that occurs after swallowing? What is the scientific name for the digestive tract? How many layers is this tract? What are the 3 parts of the pharynx? What is absorbed in the stomach? What does the pancreas do? Why are bile salts important?


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