Liver & Gall Bladder Liver produces Bile  mainly water and some bile salts Bile is stored in the Gall Bladder  the gall bladder absorbs water making the bile more concentrated Bile releases into duodenum via bile duct

Bile Salts Emulsify Fats (Emulsify - To make a suspension of small globules of one liquid in a second liquid in which the first will not mix)

Bile continued Mechanical digestion: Emulsification – bile salts break down fat globules into smaller droplets so that they can be digested by enzymes. Purpose – To increase surface area! https://www.youtube.com/watch?v=L3cJcp9G6fw

Other Liver Functions Regulate blood glucose levels (stores glycogen) Breakdown and synthesis of lipids and fats Protein breakdown and protein/non-essential amino acid synthesis Stores vitamins (A, B12, D, K) and iron Breaks down hormones, antibiotics, and other toxic substances (detoxifier) Breaks down the by-products of RBC recycling Note** these are main functions. Liver is thought to do about 500 separate functions Removes effect of poison

Gall Stones Crystalline mass formed from bile pigments, cholesterol, and calcium salts. Cause severe pain and blockage of bile duct

gallstone - A small, hard object, in the shape of a pebble, that sometimes forms in the gallbladder or bile duct; composed of cholesterol, bile pigments and calcium salts

Liver Cirrhosis Most commonly caused by alcohol, hepatitis B, hepatitis C, and fatty liver disease. Gradual build up of scar tissue that replaces normal tissue Leads to liver failure

Ethyl alcohol is toxic to the liver

Healthy Liver

Liver cirrhosis Note extensive scarring

Chronic alcoholism will typically lead to damage of the liver characterized by scarring. The damaged liver often turns an orange color. This damage of the liver is called “cirrhosis”. Cirrhosis of the liver

Jaundice One of the by-products of RBC destruction is bilirubin (yellow color) The liver filters out bilirubin from blood, and excretes in bile. If liver is failing, or bile duct is blocked, bilirubin builds up in body, causing jaundice  a yellowing of skin and whites of eyes.

Check your understanding What function does the liver have in the body? What is jaundice? And what causes it? What is the main purpose of bile salts? Explain.

Gastrointestinal Disorder Project So now that you know (almost) a lot about the normal functioning of the digestive system, it’s time to investigate some disorders!

Plagiarism Source all the materials you use! In University if caught plagiarizing you will automatically receive a zero on the assignment with the potential of receiving a failing grade in the course or a suspension from the University!

http://www.youtube.com/watch?v=yQHx9W EfT-Y&safe=active

Small Intestine Small Intestine is 7 meters in length Three parts to small intestine: Duodenum – first 25-30 cm. - Area of most digestion. Jejunum Ileum

When chyme enters the small intestine it stimulates the release of secretin and cholecystokinin by the duodenum walls. Secretin regulates pH  inhibits gastric HCl production and stimulates bicarbonate ion secretion (pancreas) Cholecystokinin causes release of bile (gall bladder) and digestive enzymes (pancreas). 9 liters of chyme a day

Pancreas Secretes pancreatic juice into the duodenum

Pancreatic juice contains: Bicarbonate – changes pH of chyme from highly acidic (pH 2) to weakly basic (pH 8) Important pH for pancreatic enzymes to function

Enzymes lipase - breaks down triglycerides into fatty acids and glycerol.

Protease – to digest proteins Amylase – to digest carbohydrates Nucleases – to digest nucleic acids

Insulin Glucagon Regulation of blood glucose levels

Check your understanding! What accessory gland produces a secretion with no digestive enzymes? What kinds of foods are broken down by the pancreas? Most enzymes are secreted as zymogens (inactive), why do you think that is?

Check your understanding! Explain two functions of pancreatic fluid. Someone recently has had a cholecystectomy, a surgical procedure to remove his gall bladder. Now he must take medication to prevent diarrhea. Why would the removal of the gall bladder cause diarrhea?

Endoscopy https://www.youtube.com/watch?v=ZvudWu vMjtA&app=desktop

Mesentery Tissue that supports the intestinal tract. A double layer of connective tissue in which blood vessels, nerves, lymphatics and other structures are contained.

Thin walls of small intestine with blood supply. Mesentery

The intestines are held in place by a pair of membranes called the mesenteries (1). The mesenteric arteries run between these parallel membranes, and give rise to a vast number of tiny arteries (2) that take blood to the jejunum and ileum. These in turn break up into the thousands of arterioles that supply the villi and help to absorb food. Near the base of the mesenteries is a row of white, fatty-looking bumps. These are lymph nodes on the lymph ducts that drain the lacteals. Since you take so much foreign material into your gut, it makes sense that you should have a strong line of defense against any invading microorganisms that might escape the digestive processes.

Adhesions often form following abdominal surgery or after an abdominal infection (peritonitis).

Peritonitis can also follow a penetrating abdominal injury.

Made up of three parts: Duodenum Jejunum Ileum Small Intestine

Segmentation Smooth muscle contractions in both directions that mix and further break down contents of small intestine (chyme) Is this mechanical or chemical digestion?

Absorption The small intestine absorbs the majority of nutrients such as The breakdown products of Carbohydrates Protein Fats Vitamins Minerals by active and passive mechanisms

Intestinal villi

Each villus contains blood capillaries and a lymph capillary (lacteal) Each villus contains blood capillaries and a lymph capillary (lacteal). Each villus is covered with microvilli.

Microvilli – “brush border”  further increases surface area Villi – tiny, finger-like projections on the walls of the small intestine Microvilli – “brush border”  further increases surface area Absorptive surface 185m !

Within villi structures are blood vessels that carry the absorbed nutrients to the rest of the body Also contained in the villi are structures called lacteal, which absorbs fats to be delivered into the bloodstream

The liver and homeostasis Almost all the blood circulating from the intestines to the heart passes through the liver. Therefore, everything you eat that gets into the bloodstream passes through your liver.

Liver Almost all the blood circulating from the intestines to the heart passes through the liver. The liver then either stores the nutrients absorbed or further metabolizes them

Other Liver Functions Regulate blood glucose levels (stores glycogen) Breakdown and synthesis of lipids and fats Protein breakdown and protein/non-essential amino acid synthesis Stores vitamins (A, B12, D, K) and iron Breaks down hormones, antibiotics, and other toxic substances (detoxifier) Breaks down the by-products of RBC recycling Note** these are main functions. Liver is thought to do about 500 separate functions Removes effect of poison

The Colon (AKA large intestine)

Water absorption 9 liters of water every day in digestive juices. Over 90% of water is reabsorbed! If not enough water is reabsorbed an individual will experience diarrhea. If too much water is absorbed an individual will experience constipation.

Chemical Digestion Indigestible food matter (e.g. cellulose) is digested by enteric bacteria (ex. E. Coli) that thrive in the large intestine. These bacteria produce vitamin K and some B vitamins which are absorbed.

Appendix Vestigial organ  has lost function but retained structure However, some scientists now think it does serve a function stores good bacteria to help repopulate gut after infection.

These wax models of human anatomy were made in the 19th century to help train doctors. They are now seen in the medical wing of this great museum in Vienna, (Wien). http://www.flickr.com/photos/moonjazz/3530268320/

Endoscopic view of appendix Cecum

Rectum Connected to the sigmoid colon of the large intestine Damp Mass of indigestible food remaining in large intestine is called FECES. Temporarily stores feces before elimination (egestion)

Anus The ending portion of the gastrointestinal tract in which feces (undigested food matter) leaves the body Anal sphincter controls opening of anus.

Bowel Movement Receptors in the walls of the large intestine give the central nervous system (brain) signals when a bowel movement is needed. Some substances stimulate the bowel movements like caffeine.

Defecation to eliminate feces.

Check you understanding!!! In your table groups discuss the major functions of the large intestine.

Main Functions of the Large Intestine Water absorption Absorption of vitamins produced by bacteria Mass movements (defecation) – removes undigested food

Summary

Digestion Time Summary 50% of stomach contents emptied 2.5 to 3 hours Total emptying of the stomach 4 to 5 hours 50% emptying of the small intestine 2.5 to 3 hours Transit through the colon 30 to 40 hours Digestion takes different lengths of time depending on the food being consumed. For healthy adults, it's usually between 24 and 72 hours.

Washing your hands is essential! Bacteria Food poisoning Parasites Worms (Tapeworms) * All can be transferred through the mouth!

The Bacteria in your Gut? Good, bad or ugly? Good √ E.coli helps you digest food that you could not digest otherwise. Bad √  The bacteria that help you out, also produce flatulence as a by-product. Gas is a normal part of digestion. Ugly √  Some bacteria cause food poisoning, resulting in severe stomach cramps, vomiting and diarrhea.

More important stuff... Our bodies make two hormones that contribute to homeostasis. GASTRIN: Releases gastric juice (HCl) and relaxes gastric sphincter. SECRETIN: Help release bicarbonate ions that neutralize HCl. Our pancreas also helps with homeostasis in regulating blood glucose.

Insulin and Glucagon in Digestive System Two hormones secreted by pancreas. Work with liver to control level of glucose in body (blood). Insulin released after meal  allows cells to become permeable to glucose. Excess glucose stored by liver as glycogen. Can change back to glucose if blood glucose becomes too low  Glucagon

Check your understanding What is the purpose of villi and microvilli as it pertains to absorption of nutrients ? What role does the large intestine play in the body? Are all bacteria in your G.I. tract bad ? Explain your reasoning. Describe one negative feedback loop in the digestive system.