Digestive System & Diet

Digestive System & Diet SBI 3U 9.5

The Pancreas • https://www.youtube.com/watch?v=NZ4zcrTzUjA • Produces digestive juices through the pancreatic duct to the duodenum. • Produces enzymes that digest carbohydrates (amylase), proteins (Trypsin) and fats (Lipase). • Produces bicarbonate salts to neutralize the stomach acid. • The pancreas is also an endocrine organ that produces insulin and glycogen to help in the metabolism of sugar

http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookDIGEST.htmlhttp://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookDIGEST.html

Liver http://www.liverdoctor.com/images/detox_pathways.jpg

Liver… • Largest internal organ • Produces Bile. Bile emulsifies fats to break them into tiny droplets called micelles • Liver continuously produce Bile and store them in the gall bladder • All blood traveling through the capillary beds of the intestine, enter the liver before returning to the heart • Liver remove toxins such as alcohol , produce and store glycogen and fat soluble vitamins • Disease: hepatitis, jaundice, cancer

Gall bladder • Lies under the liver • Stores bile – a greenish liquid • When lipid enter the duodenum, the gall bladder will contract and secrete bile to emulsify fats. • Has a common duct with the pancreas http://gensurg.co.uk/images/Biliary%20anatomy%20-%20hsk.jpg

Small Intestine • The small intestine is where final digestion and absorption occur. The small intestine is a coiled tube can be up to 7 meters long. Coils and folding plus villi give this tube the surface area of a 500-600m long tube. Final digestion of proteins and carbohydrates must occur, and fats have not yet been digested. Villi have cells that produce intestinal enzymes which complete the digestion of peptides and sugars. http://www.emc.maricopa.edu/faculty/farabee/biobk/BioBookDIGEST.html

Small intestine • The absorption process also occurs in the small intestine. Food has been broken down into particles small enough to pass into the small intestine. Sugars and amino acids go into the bloodstream via capillaries in each villus. Glycerol and fatty acids pass through the lacteals (lymphatic vessels within a Villus) to the bloodstream. Absorption is an active transport, requiring cellular energy.

Small intestine continued • Has an increased surface area due to fingerlike projections called VILLI • Produces enzymes that complete the digestion of carbohydrates, proteins and fats. • Consists of 3 areas • Duodenum • Jejunum • Ileum https://www.youtube.com/watch?v=eqV04BO_YHc

Villi

Villus http://www.colorado.edu/kines/Class/IPHY3430-200/image/villi.jpg

Absorption in Villi

Absorption in the small intestine • Passive transport is the movement of materials across a cell membrane without the use of cell energy • Amino acid will enter the bloodstream through the walls of the small intestine in a process referred to as diffusion ( area of higher conc. To lower conc.) • Water will diffuse through the cell membrane in a process called osmosis (higher conc. Of water molecule- to lower conc.)

Absorption in the small intestine • Facilitated diffusion is an example of passive transport. • Facilitated diffusion is the diffusion of molecules across a cell membrane via a transport protein • Carbohydrates are broken down into disaccharide and monosaccharide and they diffuse through cell walls using special transport proteins

Absorption in the small intestine • Active transport is the transportation of materials through a cell membrane using energy from the cell (it happens from a area of low conc to high)

Large Intestine & Appendix • Approximately 1.5 m long, about 7.6 cm wide • Cecum is where the small and large intestine meet (blind pouch) • The appendix is a small finger like projection from the cecum (no function) • The colon is longest part of the large intesitne. Comprised of the ascending, transverse, descending and sigmoid colon • Absorbs water, vitamins and minerals • rectum: last 20 cm of large intestine.Stores waste (feces) • Eliminates feces through the anus

http://www.mobyhealth.com/sub/graphics/colon.jpg

Appendix/caecum • In humans the appendix has no known function. • In herbivores such as rabbits the appendix or caecum is used to digest cellulose.

Conclusion: 5 steps of the process.. • Ingestion - taking in food. • Digestion – breaking down food. • Absorption – digested food goes into the blood. • Assimilation – digested food is used by the body. • Egestion:- Elimination, waste is removed from the body.

Summary of Digestive Enzymes

Enzymes by source

Resources http://www.innerbody.com/htm/body.html http://www.wiley.com/legacy/college/bio/tortora366927/resources/student/anatomydrill/ch24.html

Salivary gland Teeth Tongue Epiglottis Esophagus Liver Stomach Gall Bladder Duodenum Bile duct Pancreas Colon (Large Intestine) Small Intestine Appendix Rectum (Anus) http://www.lessontutor.com/digestive_system4.gif

Pancreas Gall Bladder Pancreatic Duct Bile duct Duodenum

Epithelial Lining Cells produce enzymes and absorb digested food Artery Lymph vessel Vein

Digestion of Starch “Carbohydrates are digested in the mouth, stomach and small intestine. The saliva in your mouth contains amylase. If you chew a piece of bread for long enough, the starch it contains is digested to sugar, and it begins to taste sweet.” BBC. Bitesize biology, http://www.bbc.co.uk/schools/ks3bitesize/science/biology/diet_4.shtml

Digestion of Proteins “Proteins are digested in the stomach and small intestine. Digestion of proteins in the stomach is helped by stomach acid, which is strong hydrochloric acid. This also kills harmful micro-organisms that may be in the food.” BBC; bitesize biology. http://www.bbc.co.uk/schools/ks3bitesize/science/biology/diet_4.shtml

Digestion of Fats (lipids) “Digestion of fat in the small intestine is helped by bile, made in the liver. Bile breaks the fat into small droplets that are easier for the lipase enzymes to work on.” BBC; bitesize Biology http://www.bbc.co.uk/schools/ks3bitesize/science/biology/diet_4.shtml

Digestive System & Diet