Digestion, Absorption, and Transport (Part 2)

A vocabulary flashcard based on the lecture notes regarding the role of bile in digestion.

Bile

A substance produced by the liver and stored in the gallbladder that is necessary for fat digestion and absorption; it mixes with fat in the small intestine and breaks it into smaller globules, allowing lipases to access it.

Lining of Small Intestine (absorption)

Large surface area for absorption (the size of a tennis court)

▪ Intestinal walls arranged in circular/spiral folds

▪ Covered with Villi, and Microvilli (brush border)

▪ The villi contain one cell layer that needs to be crossed to reach bloodstream and lymphatic system.

Pancreas: Exocrine tissue

Secretes pancreatic juices

✓Bicarbonate: brings up pH

✓Enzymes: Amylase, Trypsin, Chymotrypsin, and Lipase

Digestive enzymes (Amylase, Lipase, and Protease)

Protein molecules that aid in the breakdown of food for absorption

-Amylase splits carbohydrates into simple sugars -Lipase breaks fats into fatty acids and glycerol

-Protease breaks proteins into single amino acids

Pancreas: exocrine

Produces two very important hormones: INSULIN and GLUCAGON

Insulin

released when blood sugar rises, allowing muscles and other tissues to take in glucose for fuel

Glucagon

released when blood sugar is low, causing liver to breakdown glycogen and release to the blood

Insulin’s role in digestion

Allows cells to take in glucose

✓Promotes storage of glycogen by the liver

✓Leads to uptake of glucose for energy and synthesis of glycogen in muscle

✓Promotes protein synthesis in muscle

✓Promotes conversion of glucose to fat in fat cells

Gallbladder

Stores and secretes BILE

Secreted into the Small Intestine, mixes with fat, and breaks it into smaller globules, allowing lipases to access it

Liver: gatekeeper

Amino acids, sugars, water soluble vitamins cross the mucosal cells and end up moving to the hepatic portal vein which goes to the liver

In the liver they are processed, some stored, or sent to general circulation

▪ The liver modifies products of protein breakdown to make them safe to go to the kidneys

Blood Flow: transport of nutrients

When at rest: ¼ of blood goes to GI, 1/5 to your skeletal muscles, and the rest goes to the heart, kidneys, brain, skin and all other organs.

❖Blood flow changes when you eat and exercise

❖When you are exercising about 85% goes to skeletal muscles to deliver oxygen

❖When you eat a large meal more blood flows to the GI to help digestion

❖The vascular system is a closed system of vessels with the heart as a pump

❖Veins, Arteries, and capillaries to reach every cell.

❖Lymphatic system is a one-way route for fluids to travel from tissue spaces into the blood (squeezing action

Large intestines

Anything that has not been absorbed by the Small Intestine moves into the Large Intestine

▪ Has a diameter of 2-3 inches

▪ Is about 5 feet long and includes the colon and the rectum

▪ Slow movement; fecal matter may stay up to 24 hours which favors growth of bacteria

Intestinal microflora

Permanent residents of the Large Intestine

▪ There are between 300 and 500 different species

- Bacteria in gut are 10 times greater than cells in body

▪ Breakdown unabsorbed portion of food (fiber)

▪ Producing nutrients for bacteria to flourish

▪ These micronutrients synthesize some of the B Vitamins and Vitamin K, which are absorbed

▪ This breakdown produces flatulence

Colon

absorbs small amounts of water and electrolytes ▪Material not absorbed is excreted

▪ Amount of water in feces depends on intake of fiber and water

Feces

undigested matter, dead cells, water, and bacteria

Rectum

End of the colon

▪ Feces stored prior to excretion

▪ Connected to the anus

▪ Defecation is regulated by a sphincter that is under voluntary control

GI tract and factors effecting it

The GI tract deals with all the nutrients that will ultimately maintain the health status of the whole body.

✓ The GI tract is sensitive and responsive to conditions in the body and the environment.

✓ Lifestyle factors such as sleep, physical activity, state of mind, emotional state, nutrition, and food choices AFFECT the performance of the GI tract.

✓ Adequate sleep allows for repair and maintenance of tissue

✓ Physical activity promotes healthy muscle tone

✓ Mental state profoundly affects digestion and absorption through activity of nerves and hormones that help regulate the process.

✓ Emotional state (mood) also affects digestion and absorption through hormonal activity.

Vascular system

Is a CLOSED system of vessels through which blood flows continuously in a figure eight.

▪ Pumped by the heart.

▪ Blood travels from heart to arteries to capillaries to veins and back to heart

Lymphatic system

Is a one-way route for fluids to travel from tissue spaces into the blood.

▪ It has NO pump, instead lymph is squeezed from one portion of the body to another like water in a sponge as muscles contract and create pressure here and there.

Transport of lipids

Lipids always travel bundled with protein

✓Chylomicrons and lipoproteins (VLDL, LDL, and HDL)