Digestion Study Guide

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What two processes are involved in digestion?

- Breaking down food, followed by absorption and elimination

What results from digestion?

Small molecules that the body is able to use.

What type of reaction is involved with the chemical breakdown of food?

An acidic reaction.

Where is most of the absorption of nutrient carried out?

Small intestine

What structures are especially designed for absorption?

Ileum

Name four materials that our bodies are able to absorb.

Sugar, Amino Acids, Glycerol, and Fatty Acids

What is another name for elimination?

Waste removal (Using the bathroom)

What is another name for the mouth in digestion?

Salivary Glands

What process are the teeth responsible for?

Mechanical Digestion (breaking down using physical force)

What two things does the saliva do to your food?

1) liquifies food
2) Lubricates and softens the BOLUS of food.

How does your tongue participate in the digestion?

- protects us against poisons
- Moves food around
- Helps swallow food

Prior to swallowing, the food is pushed to this part of the throat called the ?

swallow reflex center

What structure keeps food from entering the trachea ?

epiglottis

From the pharynx, the food enters the...

Esophagus

What is the function of the cardiac sphincter at the end of the esophagus?

ensures that no food re-enters the esophagus

Describe the stomach

A large organ that helps in the digestive process (J shaped).

Explain how the stomach is involved in physical digestion

Churns food and liquifies it

Explain how the stomach is involved in chemical digestion?

-Columnar epithelium produces an inactive enzyme called PEPSINOGEN.
-These cells contain many mitochondria for active transport.
- Chief Cells produce 3M Hydrochloric Acid (HCl).
- HCL is a strong acid and therefore very effective at breaking down materials

What is the band of muscles that closes off the far end of the stomach?

pyloric sphincter

How does the pyloric sphincter regulate the activities of digestion?

Move the chyme (an acidic liquid) into the duodenum at a slow, controlled rate.

The duodenum is actually part of what structure?

The Small Intestine

Which organs secrete their digestive enzymes in the duodenum?

Liver, Pancreas

What does the liver produce for the digestive process?

Bilirubin : A waste product from Haemoglobin

What happens to bile after it is produced by the liver?

1) The bilirubin is exported in bile to the gall bladder

2) It is also put into the blood stream where it is removed by the kidneys

What types of diet do the pancreatic enzymes digest?

Proteins, Lipids, and Carbohydrates

Where does the remaining food go after it leaves the duodenum?

The large intestine

What is the main function of the small intestine?

To complete digestion and begin absorption of nutrients.

What is found at the junction of the small intestine and the large intestine?

The Ileum

What is the function of the ileum?

to absorb all of the nutrients into the circulatory and lymphatic systems.

Another name for the colon is the what?

The large intestine

What happens in the colon?

Water is absorbed and undigested food is eliminated

What structure is found at the end of the colon?

The rectum

What is the function of the rectum?

Compress waste materials into a solid form before being eliminated

The band of muscle that releases wastes is called the what?

The anus

What foods start breaking down in the mouth?

Starch

What enzyme is responsible for the breakdown of food in the mouth?

Amylase

The stomach is used primarily for the breakdown of which type of foods?

Proteins

What is the function of Hydrochloric acid in the stomach?

Digest proteins into peptides and polypeptides

The enzyme responsible for the breakdown in the stomach is called what?

Pepsin

What is formed form the initial breakdown of proteins?

Peptides + Polypeptides

What is a protease?

an enzyme that breaks down proteins and peptides.

Name two proteases.

chymotrypsin, chymotrypsin

What three enzymes are produced by the pancreas?

Trypsin, Lipase, Amylase

Where do pancreatic enzymes do their work?

the exocrine gland

Which enzyme is used to break down carbohydrates?

Amylase

What does the enzyme trypsin produce?

peptides, di-peptides, and tri-peptides.

What are peptidases?

intestinal enzyme that completes digestion of partially digested proteins to amino acids

Before lipase can begin work, what must happen?

Fats must be broken down into smaller pieces using bile produced by blood in the liver.

What products are formed after peptidases do their work?

Amino Acids

What organ produces peptidases?

The small intestine

What enzyme is produced by the small intestine besides peptidases?

maltase

Swallowing is a reflex action. What does this mean?

Involuntary due to a give stimulus (food entering the back of the mouth)

Where in the digestive system does swallowing originate?

The Pharynx

What keeps food from going up onto the nasal cavity?

A soft palate covers the opening to the nose

What directs food into the esophagus?

The pharynx closes off the nose and trachea, and guides food with the help of the tongue

Once in the esophagus, how is food moved towards the stomach?

Involuntary constriction and relaxation of the muscles. (peristalsis of the esophagus)

What type of muscle is responsible peristalsis

cardiac sphincter

What is meant by gastric juice?

a digestive fluid secreted by the stomach.

What two substances make up the gastric juices?

HCl and Pepsinogen

Why is it important for the stomach contents to be acidic?

Breaks down molecules (acids are very corrosive)

What substances make up pancreatic juice?

Sodium Bicarbonate, trypsin, lipase, amylase

. What is the function of sodium bicarbonate (NaHCO3)?

digest food and neutralize chyme

What happens if the pancreatic juice contains an insufficient amount of sodium
bicarbonate?

acidic chyme will not be neutralized

What two enzymes make up the intestinal juice?

nuclease, maltase, peptidases

Gastric secretions are under the control of what hormone?

Gastrin

Where is gastrin produced?

the submucosa of the lower
stomach (Stomach)

What causes production of this hormone?

Presence of BOLUS in stomach

What happens to gastrin after it has been produced?

Gastric juice is released, killing bacteria and digesting protein

What effect does it have on the stomach?

The stomach becomes more acidic, and also gains the ability to Pepsinogen to Pepsin, and Pepsin to Peptides + Polypeptides

Explain how the production of gastrin is an example of negative feedback.

If HCl formed from Gastrin enters the duodenum, NaHCO3 from the pancreatic juices (high pH) lowers the acidity of the solution.

What two important hormones are produced by the duodenum?

Secretin, and CCK

What causes the production of secretin?

Presence of CHYME in duodenum

What causes the production of CCK?

Presence of fatty acids in duodenum

Which hormone causes the gall bladder to release its bile?

CCK

Both hormones causes what to release its enzymes?

The pancreas

What organ is responsible for the production of insulin?

The pancreas

What hormone besides insulin is produced by the pancreas?

glucagon

What is an endocrine gland?

A gland in the pancreas that produces hormones

Explain how insulin controls the blood sugar level in a negative feed back cycle?

If there is excess blood glucose in the liver, insulin converts it to glycogen

What happens to excess glucose in the blood?

Converted to glycogen.

Why does insulin promote protein and fat synthesis?

1. Inhibition of glycogen synthesis (liver glycogen 5-6%)

2. Activation of acetyl-CoA carboxylase, leading to an excess of citrate & isocitrate ions and conversion of acetyl-CoA to Malonyl-CoA

3. Activation of lipoprotein lipase which splits triglycerides into fatty acids, which are transported into adipose cells and stored.

What hormone raises the blood sugar level?

Glucagon

What does glucagons cause the liver to do?

produce glucose in the bloodstream

Describe the function of bile.

aids in the emulsification, digestion, and absorption of fats

Where is it produced?

the liver

Where does it function?

the gall bladder

The liver maintains this vital concentration in the blood.

sugar

The liver produces what from the breakdown of amino acids?

converted into glucose to maintain glucose concentration of plasma (this is called gluconeogenesis).

The liver metabolizes poisonous substance. What does this mean?

The liver detoxifies any poisons or harmful substances that were absorbed by the digestive tract
(ie: alcohol is metabolised into fatty acids).

The liver breaks down old red blood cells and recycles hemoglobin by turning it into what?

bilirubin and biliverdin (the components of bile)

The liver produces blood proteins such as what? Give two examples

fibrinogen and prothrombin

The small intestine has at least three features that increase the surface area. What are those features?

convoluted (folded) walls, VILLI (folds in mucose layer), and MICROVILLI (smaller folds)

Why is increased surface area vital for absorption?

Increases amount of food absorbed (more time to go through the organ)

What are the special projections on the wall of the intestine called?

villi

Within villi are special cells called what?

collumnar cells

Within each villus are blood vessels and an extension of the lymphatic system
called a what?

microvilli

What are the two functions of the blood vessels?

- Carry blood (containing oxygen and nutrients) through the body.
- Carry hormones, and enzymes to stimulate specific functions of organs

What is the function of the lacteals?

Absorb dietary lipids into the lymphatic system

What process is used to transport materials from the gut into the blood stream?

The hepatic portal vein (drains blood from the gastrointestinal tract and spleen to capillary beds in the liver)

Where do the products of fat digestion go after they are absorbed into the lacteal?

It travels through the lymphatic system until it is dumped into the circulatory system.

Where do the sugars go after they are absorbed into the bloodstream?

They are carried to all of the body's tissues and are used to supply energy

What are anaerobic bacteria?

Bacteria that does not require oxygen

Where are anaerobic bacteria found?

In the intestinal tracks

Why are anaerobic bacteria important for us?

Breakdown bio-organic materials (help with digestion)

What is one socially embarrassing problem related to anaerobic bacteria living within our intestines?

Farts

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