Order of Events: Small Intestine

stomach

esophagus

large intestine anus

small intestine

Mouth pharynx

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• Long part of the digestive tract – almost 7 m long in a human!

Small Intestine Structure

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Small Intestine Functions• Lined with villi and

microvilli to increase surface area and absorption of nutrients

• Completes digestion of food

• Receives secretions from the pancreas and the liver to aid in digestion

Villi in the small intestine

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Small Intestine: Enzymes• Enzymes from the small intestine include

Proteases=break down amino acid chains into amino acids• Carbohydrases =

break down disaccharides into monosaccharides

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Small Intestine: EnzymesExamples of Carbohydrases and proteases

Enzyme FunctionSucrase

Maltase

Lactase

Protease

Digests sucroseDigests maltoseDigests lactose

Breaks down dipeptides into amino acids

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Small Intestine •All types of foods are digested here!

Burger link

Did you notice that most of the chemical

digestion and absorption of food

molecules occurs in the SMALL INTESTINE?

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A quick review of the digestive system:

Video on the digestive system

Look at the digestive system from Inside with Dr. Oz!

Order of Events: Large Intestine

stomach

esophagus

small intestine

anuslarge intestine

Mouth pharynx

Absorption

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Large Intestine• Shorter than the small

intestine (approximately 1.5 m long) but is larger in diameter

• Joins to small intestine through the ilial-caecal sphincter

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rectumanus

small intestine

large intestine stomach

Ilial-caecal sphincter

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Cecum and Appendix• Cecum = small pouch at the

beginning of the large intestine

• Appendix = a small projection on the cecum– A vestigial organ (no longer

needed in humans)– Found in herbivorous

mammals for cellulose digestion

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Large Intestine

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Functions of the Large Intestine1. absorb water, vitamins and minerals into

blood2. Bacteria aid in digestion and help synthesize

(make) vitamin K3. Store undigested materials from digestive

tract

http://www.youtube.com/watch?v=k_WKdrFVBFg&safety_mode=true&safe=active

Bill Nye on the small and large intestine: Beg – 1:54 and 3:29- 6: 35 (peristalsis and chyme)

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Why is a diet high in fiber important to maintain good health?

• Humans do not have the enzyme cellulase to digest fibre

• BUT we still need fibre!– fiber in the diet helps

retain water throughout the digestive tract resulting in soft feces

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• Fiber-rich foods work wonders in the body, regulating blood-sugar levels, reducing the risk of coronary heart disease, stroke, hypertension, diabetes, obesity, breast cancer, colon cancer and gastrointestinal disorders such as reflux, duodenal ulcer, irritable bowel and diverticulitis (inflammation of abnormal pouches in the wall of the large intestine or colon), and also supporting weight loss.

Order of Events: Anus

stomach

esophagus

large intestine

small intestine

anus

Mouth pharynx

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Rectum & Anus• Last part of digestive

tract• Feces is stored in the

rectum and exits through a sphincter muscle called the anus

anus

rectum

Caution!!!!!

The Next Slide is for Mature Audiences only !!!!!!

Rectum & Anus

Hemorrhoids are formed when veins near the rectal opening become inflamed and swollen

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How much time does food spend in each part of the digestive system?

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Digestion Summary

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Accessory Organs in DigestionLabel and colour the following diagram showing the accessory organs of digestion

liver

gallbladder

pancreas

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Accessory Organs in DigestionLiver•Produces bile (a brown fluid) which is then stored in the gallbladder

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Liver and Bile

1) Large fat globule (small intestine)

bile

2) Smaller fat globules (small intestine)

• Bile = a fluid produced by the liver to help emulsify (physically break down) fats– Provides more surface area for lipase to work

lipaselipase

lipaselipase

• Gallbladder– Stores bile (made by the liver) and secretes bile

into the small intestine

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Gall Bladder

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• The pancreas secretes pancreatic juices to aid in digestion

• Pancreatic Juices contain: (ALTA) acronym

– Alkaline salts– Lipase– Trypsin– Amylase

Pancreatic Juice

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Pancreatic Fluid Secretions

Function of Secretion

Alkaline salts (NaHCO3 – sodium bicarbonate)

•Secretin from small intestine goes to pancreas through the blood stream and stimulates the pancreas to release bicarbonate ions•These ions go to the small intestine through the pancreatic duct where they buffer/neutralize the HCl from the stomach•Raises pH to 8

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Pancreatic Fluid Secretions Function of Secretion

Lipase •Enzyme digesting lipids (triglycerides) into fatty acids & glycerol

Protease (Trypsin)

•Enzyme secreted in inactive form (trypsinogen) which continues protein digestion•Activated by alkaline (basic) pH

Pancreatic Amylase

•Enzyme which continues the digestion of starch into maltose units (completes the digestion that started in the mouth)

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The Liver• The liver is the largest organ

in the body• Receives blood from 2

supplies

– hepatic artery•oxygen rich blood

from heart– hepatic portal vein

•nutrient rich blood from intestinal walls

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The Liver• liver acts as a

“gatekeeper” to absorb nutrients from the blood– the liver removes

excess nutrients in the blood

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Digestive Function of the Liver1) Digestive

Function– Production of bile

which emulsifies (breaks down) fats, which increases the surface area for lipase to act on

– Bile is stored in the gall bladder

Liver

gallbladder

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Regulatory Functions of the Liver2a) Regulation of Blood Glucose

– removes excess glucose from blood after meal and converts it to glycogen

– once glycogen stores are full, it converts extra glucose into fat which is released from liver into the blood and stored in adipose tissue

when blood sugar levels fall, liver converts glycogen back into glucose and releases it into blood

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Regulation of Blood Glucose• Other hormones involved (from the

pancreas)• To store glucose from foods we eat,

the liver relies on two hormones produced by the pancreas

– Insulin (converts glucose to glycogen for storage)

– Glucagon (converts stored glycogen into glucose as needed)

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The Role of Insulin & Glucagon

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Other Regulatory Functions of the Liver• 2b) Other Regulatory

Functions• In addition to storing

glucose as glycogen, the liver also stores vitamins and minerals

• The liver takes up and stores fat soluble vitamins such as A, D, E, and K and inorganic minerals such as iron

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3) Synthesis of Plasma Proteins– manufactures important

blood proteins – Examples:

•Fibrinogen (for blood clotting)

•albumin•globulin

Regulatory Function of the Liver

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Other Excretory Functions of the Liver4) Excretory Functions

Breakdown of old Red Blood Cells• the pigment is excreted in bile• the iron is stored for future RBC’sDetoxification• liver breaks down poisons and non-

food substances in blood• e.g.: alcohol, caffeine, nicotine, drugs,

excess hormonesProduction of urea• deamination (breakdown) of excess

amino acids

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Normal and Diseased Livers

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StomachThe stomach absorbs:

– some water– glucose– specific vitamins– alcohol

• After digestion is complete, the simple molecules must be absorbed into the circulatory system or lymphatic system to be carried to the body cells

• The stomach, small intestine, and large intestine play a major role in absorbing required simple molecules

Topic 4-4: Absorption

https://www.youtube.com/watch?v=vkpz7xFTWJo

ASAP Science: Your brain on alcohol 2:13

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Small Intestine• Once ALL food molecules are at

monomer stage, they are ready to be absorbed into the circulatory system

• Capillaries (blood) absorbs:– monosaccharides– amino acids– vitamins/minerals– water

• Lacteals (lymphatic system) absorb:– lipids

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Diffusion

Absorption in the Small Intestine

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Absorption in the Small Intestine

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Large Intestine• Absorbs water, minerals and vitamins• Any material not absorbed, forms the fecal

material that is removed from the body by egestion

http://www.youtube.com/watch?v=nM5kMSjBrmw

Bozeman Digestion video 9:39

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Topic 4-6 Disorders of Digestive System

• Cause: Mucous lining of stomach breaks down. Cell membrane is exposed to corrosive acid and pepsin. When cells are destroyed, an ulcer forms.

• Symptoms: pain, especially when eating acidic or hot foods

• Treatments: Lasers remove damaged tissues + seal blood vessels.

Ulcers

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Gall Stones• Cause: Cholesterol , an insoluble

component of bile, acts as a binding agent for salt crystals found in bile

• Symptoms: Pain. Inflamed and blocked gall bladder can rupture – can be life threatening

• Intense pain below ribcage that can radiate to right shoulder accompanied with loss of appetite & nausea

• Treatment: Removal of gall bladder OR medicines that dissolve gall stones ALSO shockwave therapy.

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Jaundice• Causes: Blocked bile duct or

accelerated destruction of RBC’s can cause jaundice (can lead to hepatitis). Liver is not functioning properly.

• Symptoms: A sign of the disease is yellow skin and eyes

• Treatments: Diet, therapy or exercise will help. Also fruit juices (minor cases), enemas, drugs and liver transplants (major cases)

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Appendicitis• Cause: Inflammed appendix• Symptoms: Pain in lower right

abdomen, accompanied by fever, vomiting

• Treatments: Removal of appendix

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Heartburn

• Cause: HCl being washed up from the stomach through the cardiac sphincter

• Symptoms: burning sensation in the esophagus

• Treatments: Antacids (ex. TUMs), less alcohol/tomatoes