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Malika Biology MCAT > Chapter 9 - The Digestive System > Flashcards

Chapter 9 - The Digestive System Flashcards

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1
Q

Mechanical digestion

A

Physical breakdown of large food particles into smaller food particles, no breaking of chemical bonds

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2
Q

Chemical digestion

A

Enzymatic cleavage of chemical bonds in food particles, such as the peptide bonds of proteins or glycosidic bonds of starches

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3
Q

What is the function of enteric neurons in the digestive system?

A

Enteric neurons are present in the gastrointestinal system responsible for triggering peristalsis which is the rhythmic contraction of the smooth muscle in order to move food through the system.

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4
Q

Which hormones are associated with feelings of hunger?

A

Glucagon secreted by the pancreas
ghrelin secreted by the stomach and pancreas.

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5
Q

Which hormones are associated with feelings of satiety?

A

Leptin and cholecytoskinin

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6
Q

What is mastication?

A

This is the process of chewing, which helps increase surface area to volume ratio of food for easy access for enzymes.

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7
Q

Where does chemical digestion occur in the digestive system specifically?

A

It occurs in the mouth (only carbohydrates), stomach, and in the small intestine.

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8
Q

What are the two enzymes present in saliva?

A

Salivary amylase which hydrolyzes starch into smaller sugars, and lipase which hydrolyzes lipids.

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9
Q

Where does peristalsis occur?

A

Esophagus, small intestine

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10
Q

The pharynx connects to two structures in the digestive system, what are they?

A

Esophagus and larynx

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11
Q

The top part of the esophagus is under (voluntary/involuntary) control, while, the bottom part of the esophagus is under (voluntary/involuntary) control.

A

Voluntary, involuntary

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12
Q

The stomach consists of two types of glands _________.

A

Gastric glands and pyloric glands

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13
Q

What is the function of the epiglottis?

A

It is a flap that connects the pharynx to the larynx known as the voice box, it prevents food from going down the larynx.

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14
Q

What are the main functions of the stomach?

A

Churning of food, hydrolysis (digestion) of food particles, turning food into chyme, storing chyme until secretion into the duodenum

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15
Q

What is the main enzyme responsible for hydrolysis/digestion of proteins?

A

Pepsinogen which is cleaved to form pepsin. Pepsin cleaves peptides near aromatic amino acids.

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16
Q

What are the four types of cells that line the stomach gastric pits?

A

Mucous cells, chief cells, parietal cells, G-cells

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17
Q

What is the function of mucous cells?

A

Secrete mucus which lines the stomach and protects the stomach from the acidity of the gastric juice. The mucus is alkaline because it consists of bicarbonate.

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18
Q

What is the function of chief cells?

A

Make and secrete, the zymogen pepsinogen into the stomach lumen.

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19
Q

What is the function of parietal cells?

A

Secrete HCl which is gastric juice allowing the conversion of pepsinogen to pepsin (active form of enzyme) and secrete intrinsic factor which is a glycoprotein that helps absorption of vitamin B-12.

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20
Q

What is the function of G-cells?

A

Make and secrete gastrin into the blood. Gastrin is responsible for inducing the stomach to secrete more HCl and to contract.

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21
Q

True or false:
Absorption mainly occurs in the stomach.

A

False, the stomach is mainly responsible for digestion. The small intestine is responsible for absorption.

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22
Q

What are the three parts of the small intestine?

A

Duodenum, jejunum, and the ileum

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23
Q

The duodenum releases brush border enzymes called disaccharidases which break down biomolecules into absorbable monomers. What happens if a certain disaccharidase is lacking?

A

The duodenum will not be able to break down that corresponding disaccharide. A disaccharide will instead be hydrolyzed by bacteria that produce methane gas as a byproduct.

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24
Q

The duodenum also secretes digestive enzymes. What are they and their function?

A

Peptidases such as aminopeptidase and dipeptidase - break down peptides into a smaller form
Enteropeptidse - activates trypsinogen by cleaving it, activates procarboxypeptidases A & B

25
Q

What role does the pancreas have?

A

Secrete hormones into bloodstream and secrete bicarbonate pancreatic juice into a duct that travels to the duodenum.

26
Q

What cells are responsible for secreting pancreatic juice?

A

Acinar cells

27
Q

What does pancreatic juice consist of?

A

It is made of bicarbonate (alkaline) solution and different digestive enzymes which breakdown, carbohydrates, proteins, and fats.

28
Q

Among secretion of digestive enzymes, the duodenum also secretes hormones. What are they and what are their functions?

A

Secretin - causes the pancreas to release pancreatic enzymes into the duodenum, regulates stomach pH by reducing HCl secretion from parietal cells, slows motility through digestive tract
Cholecystokinin - stimulates release of bile & pancreatic juice, promotes satiety in brain

29
Q

Pancreatic digestive enzymes released into the small intestine function ideally at a pH of ___, while digestive enzymes in the stomach function ideally at pH __.

A

8.5, 2

30
Q

What is chyme?

A

The broken down food particles produced by the stomach which results in an acidic, semifluid mixture

31
Q

Which pancreatic enzyme breaks down large polysaccharides into small disaccharides?

A

Pancreatic amylase

32
Q

Which pancreatic enzymes break down proteins?

A

Trypsinogen, chymotrypsinogen, and carboxypeptidases A & B

33
Q

What is the function of pancreatic lipase?

A

It breaks down fats into free fatty acids and glycerol

34
Q

Acinar cells are considered to be (exocrine/endocrine) cells because they secrete products into ducts.

A
35
Q

What are the functions of the liver?

A

Glycogenesis and glycogenolysis
storage & mobilization of fats
gluconeogenesis
production of urea
detoxification of chemicals/drugs/bacteria
production of bile
synthesis of albumin & clotting factors
regulation of amino acid blood levels

36
Q

What is bile made of?

A

Composed of bile salts, pigments like bilirubin, and cholesterol.

37
Q

What is the role of bile?

A

Bile contains amphipathic bile salts which emulsify fats and cholesterol into micelles allowing pancreatic lipase access to hydrolyze them. Without bile, proper fat digestion wouldn’t be able to occur.

38
Q

Where is bile produced?

A

Liver

39
Q

If the liver is damaged, what will happen to the level of ammonia in the blood?

A

The levels of ammonia would increase because the liver would not be able to convert it into urea that can be excreted by the kidneys.

40
Q

How does the liver control glucose metabolism?

A

It is able to take in excess sugar from the blood that travels through the hepatic portal vein and convert it to glycogen. On the other hand, it can also breakdown stored glycogen to form free glucose that will be released into the blood.

41
Q

What is bilirubin?

A

It is a pigment that is a byproduct of hemoglobin breakdown and is secreted into the bile to be exerted.

42
Q

What is the function of the gallbladder?

A

It stores bile.

43
Q

The duodenum is mainly responsible for digestion while the jejunum and ileum is responsible for __________.

A

Absorption

44
Q

The small intestine, especially the middle and last part of it contain finger like projections on its walls called ________.

A

Villi (singular: villus)

45
Q

What is the function of villi?

A

They contain blood vessels which absorb water soluble nutrients (proteins) and a lacteal (lymphatic channel) which absorbs fats.

46
Q

What are microvilli and their function?

A

Small hairs on each villi that increase the surface area available for absorption even more

47
Q

Which molecules in the small intestine travel from the epithelial cells to the capillaries to be absorbed?

A

Carbohydrates, amino acids (proteins), short chain fatty acids, water-soluble vitamins (B complex & C), water itself, bile salts

48
Q

Which molecules in the small intestine travel from the epithelial cells to the lacteal to be absorbed by the lymphatic system?

A

Long chain fatty acids, triacylglycerol, cholesterol, fat soluble vitamins (A, D, E, and K)

49
Q

Molecules absorbed into the lacteal are further subdivided into two categories, those that are packaged into chylomicrons and those that just diffuse freely into the lacteal. Describe the categorization.

A

Chylomicrons carry phospholipids, cholesterol, and fat soluble vitamins throughout the lacteal.
Long chain fatty acids and triglycerides freely diffuse into the lacteal.

50
Q

Physical characteristics of the large intestine

A

Larger diameter, shorter length than small intestine, contains a lot of gut bacteria

51
Q

The large intestine is divided into the

A

Cecum, colon, and rectum

52
Q

Which part of the large intestine is mainly responsible for absorbing water and salts?

A

Colon

53
Q

What is the function of the colon specifically?

A

It’s main job is to absorb water and to concentrate the remaining material left over from the small intestine to form feces.

54
Q

Apart from absorbing water and salts, the colon also absorbs ________.

A

Vitamins (specifically vitamin K, B7, thiamine, and B12) which are produced by the beneficial bacteria in the colon)

55
Q

What is the function of the rectum?

A

To store feces until defection

56
Q

Digestion and absorption for carbohydrates: where does it begin & end?

A

Begins in the mouth and is completed by the time food passes through the small intestine. Carbs are broken down into their monomers before being absorbed. They enter the bloodstream and travel to the liver through the hepatic portal vein.

57
Q

Digestion and absorption for proteins: where does it begin and end?

A

Protein digestion begins in the stomach by the enzyme pepsin and continues until it reaches the end of the small intestine. Proteins are broken down into tri-, di-, or mono- peptides before being absorbed. They enter the bloodstream and travel to the liver.

58
Q

Digestion and absorption for lipids: where does it begin and end?

A

Lipid digestion begins in the duodenum of the small intestine where is encounters bile and the enzyme lipase. When absorption occurs lipids enter lacteals instead of the capillaries (that proteins and carbohydrates enter).

59
Q

Compare the pH of the stomach, duodenum (small intestine), and mouth respectively

A

2, 6, and 7

Malika Biology MCAT (12 decks)

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