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What goes in, must come out.

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Presentation on theme: "What goes in, must come out."— Presentation transcript:

1 What goes in, must come out.
Digestive System What goes in, must come out.

2 Major Activities of Digestive System
Ingestion Mechanical Processing Digestion Secretion Absorption Defecation Defense Peristalsis


4 Organs of the Digestive Tract
Digestive Tract consists of two parts: Alimentary Canal – actual digestive tract organs Accessory Organs – organs that help in digestion but no food ever enters

5 Alimentary Canal Accessory Organs
mouth salivary glands pharynx teeth esophagus pancreas stomach liver small intestine gall bladder large intestine anus


7 Oral Cavity Food enters the digestive system here
Teeth tear, cut and grind food into small pieces (mechanical digestion) Saliva from salivary glands moistens food Saliva also contains amylase that break down large carbohydrates

8 Salivary Glands Parotid, submandibular and sublingual glands located in the oral cavity produce the majority of the saliva Saliva is mostly water with mucous

9 What’s a bolus? The bolus is a small mass of chewed food mixed with saliva. Epiglottis, flap of cartilage, covers the opening of the larynx to prevent food from going to lungs. Soft palate raises to prevent bolus from entering into nasal cavity

10 Peristalsis Peristalsis in Action
Peristalsis is the rhythmic contraction of smooth muscles to move contents through the digestive tract. Peristalsis starts in the esophagus where the bolus is propelled down towards the stomach. Lower esophageal (cardiac) sphincter is the opening of the stomach and relaxes allowing bolus to enter Peristalsis in Action

11 Stomach Stores ingested food until it is released into the small intestine Secretes hydrochloric acid (HCl) and enzymes (pepsin) that begins protein digestion = chyme High acidic levels (low pH) kill most bacteria and other pathogens found in the food we eat Absorbs vitamin B12, alcohol, aspirin, water, and caffeine

12 Facts about the Stomach
muscular, elastic, pear-shaped can change size … 12” x 6” and can hold about 2-4 liters of food Cardiac sphincter prevents food from passing back to the esophagus (heartburn) Stomach empties into the duodenum and is separated by pyloric sphincter You re-grow a new stomach lining every 3 days

13 Layers of the Stomach Starting from inside…
Mucosa – acid and digestive juices secreted Submucosa – connective tissue Muscularis – layer of muscle that moves and mixes stomach content Subserosa and serosa – wrapping for the stomach


15 Inside of Stomach Outside of Stomach


17 The journey…. After 1 to 3 hours in the stomach, chyme moves into the small intestine Strong peristaltic waves propel chyme through pyloric canal toward pyloric orifice (the opening between stomach and small intestine) Phyloric sphincter controls the rate and amount of chyme entering intestine

18 Small Intestine Divided into three sections duodenum jejunum ileum

19 Duodenum First section of small intestine
C-shaped and ~ 10 inches long Complete digestion of food molecules occurs in the duodenum Presence of acidic chyme stimulates the release of pancreatic secretions these secretions are clear, basic, and contain mostly water and some enzymes. secretions help neutralize stomach acid

20 Pancreas Pancreas makes insulin and digestive enzymes which are ‘dumped’ into the duodenum Insulin regulates glucose levels and is related to Diabetes


22 Increase surface area of intestine so more absorption can occur
Microvilli Increase surface area of intestine so more absorption can occur

23 Jejunum and Ileum Most absorption of the digested food occurs in the jejunum Jejunum is the middle part of the small intestine Ileum is the last part of small intestine and is primarily responsible for absorbing salts and vitamin B12

24 Liver the liver is an accessory organ
produces bile that is dumped into duodenum. Bile is basic, contains water, bile salts, bile pigments, cholesterol and enzymes Absorbs alcohol Bile breaks down large fat droplets into smaller ones so enzymes can digest the fat Excess bile is stored in the gall bladder

25 Large Intestine

26 Large Intestine a.k.a. “large bowel” – part of the digestive system where waste products from food are collected and processed into feces. Large Intestine’s Functions: reabsorbs water; maintains fluid balance absorbs certain vitamins processes undigested material (fiber) stores waste before it is eliminated

27 Cecum first part of the large intestine
shaped like a small pouch and is located in the right lower abdomen it connects the small and large intestines the cecum accepts and stores processed material from small intestine and moves it towards the colon ileocecal valve is the sphincter between the two intestines the appendix extends from the cecum

28 Vermiform Appendix A blind ended tube connected to the cecum
Vermiform in Latin means “worm-like” The biological purpose of the appendix has mystified scientists for some time The most common explanation is that the appendix is a vestigial structure with no absolute purpose Some people are born without an appendix Sometimes bacteria and indigestible material become trapped in the appendix causing it to swell and rupture

29 Colon Shaped like an inverted “U” Largest part of the large intestine
Colon has four sections: Ascending colon Transverse colon Descending colon Sigmoid colon

30 What does the colon do? Fiber, small amounts of water, vitamins, etc. mix with mucus and bacteria and start to form feces The lining of the colon absorbs most of the water along with vitamins and minerals Bacteria chemically break down some fiber for their own nourishment Through muscular movement, feces is pushed along until the sigmoid colon contracts, and then the feces is moved into the rectum. The rectum is the final part of the large intestine. Stool is stored here before being passed as a bowel motion.

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