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MCAT BIO my flashcards > Digestive System > Flashcards

Digestive System Flashcards

1
Q

Intracellular digestion

A

As part of metabolism, involves the oxidation of glucose and fatty acids for energy

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2
Q

Alimentary canal

A

Runs from the mouth to the anus and is sectioned off by sphincters, or circular smooth muscles around the canal that can contract to allow compartmentalization of function

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3
Q

Mechanical digestion

A

The physical breakdown of large food particles into smaller food particles, but does not involve breaking chemical bonds

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4
Q

Chemical digestion

A

The enzymatic cleavage of chemical bonds, such as the peptide bonds of proteins or the glycosidic bonds of starches

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5
Q

Absorption

A

Involves the transport of products of digestion from the digestive tract into the circulatory system for distribution to the body’s tissues and cells.

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6
Q

Pathway of food in the digestive tract

A

Oral cavity/mouth –> pharynx –> esophagus –> stomach –> small intestine –> large intestine –> rectum

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7
Q

Enteric nervous system

A

A collection of one hundred million neurons that govern the function of the gastrointestinal system –> trigger peristalsis

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8
Q

Mastication

A

Chewing: helps to increase surface area-to-volume ratio of food, creates more surface area for enzymatic digestion as it passes through the gut tube

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9
Q

Salivary amylase

A

Capable of hydrolyzing starch into smaller sugars (maltose and dextrins)

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10
Q

Lipase

A

Catalyzes the hydrolysis of lipids

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11
Q

Pharynx

A

Cavity that leads from the mouth and posterior nasal cavity to the esophagus

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12
Q

3 parts of the pharynx

A

Nasopharynx (behind the nasal cavity), the oropharynx (at the back of the mouth), and the laryngopharynx (above the vocal cords)

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13
Q

Epiglottis

A

A cartilaginous structure that folds down to cover the laryngeal inlet –> prevents food from entering the larynx

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14
Q

Esophagus

A

Muscular tube that connects the pharynx to the stomach

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15
Q

Muscular composition of esophagus

A

Top third of the esophagus is composed of skeletal muscle, bottom third is composed of smooth muscle, and middle third is a mix of both

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16
Q

Emesis

A

vomiting

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17
Q

Upper esophageal sphincter

A

Where swallowing is inititaed; in the orpharynx

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18
Q

Lower esophageal sphincter (cardiac sphincter)

A

Relaxes and opens to allow the passage of food

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19
Q

What are the 3 main energy sources for the body

A

Carbohydrates, fats, and proteins

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20
Q

Stomach

A

Highly muscular organ with a capacity of approximately 2 liters. In humans, the stomach is located in the upper left quadrant of the abdominal cavity, underneath the diaphragm.

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21
Q

The 4 main anatomical divisions of the stomach

A

The fundus and body, which contain mostly gastric glands,

antrum and pylorus, which contain mostly pyloric glands.

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22
Q

Lesser curvature

A

The internal curvature of the stomach

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23
Q

Greater curvature

A

External curvature of the stomach

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24
Q

Rugae

A

Lining of the stomach is thrown into folds

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25
Q

Gastric glands

A

Respond to signals from the vagus nerve of the parasympathetic nervous system, which is activated by the brain in response to the sight, taste, and smell of food.

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26
Q

What are the 3 different cell types in gastric glands

A

Mucous cells, chief cells, and parietal cells

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27
Q

Mucous cells

A

Produce the bicarbonate-rich mucus that protects the muscular wall from the harshly acidic (pH = 2) and proteolytic environment of the stomach

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28
Q

Gastric juice

A

A combination of secretions from the other 2 cell types in the gastric glands: chief cells and parietal cells

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29
Q

Chief cells

A

Secretes pepsinogen: the inactive, zymogen form of pepsin, a proteolytic enzyme.

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30
Q

Parietal cells

A

Secrete hydrogen ions in the stomach as hydrochloric acid, which cleave pepsinogen to pepsin. Also secretes intrinsic factor.

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31
Q

Pepsin

A

Digests proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments

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32
Q

Intrinsic factor

A

A glycoprotein involved in the proper absorption of vitamin B12.

33
Q

Pyloric glands

A

Contain G-cells that secrete gastrin, a peptide hormone –> Induces the parietal cells in the stomach to secrete more HCL and signals the stomach to contract, mixing its contents.

34
Q

Chyme

A

Acidic, semifluid mixture from digestion of solid food in the stomach

35
Q

What are the 3 segments of the small intestine

A

The duodenum, the jejunum, and the ileum

36
Q

Where does the majority of chemical digestion in the small intestine occur

A

Duodenum

37
Q

Where does the majority of absorption in the small intestine occur

A

The jejenum and the ileum

38
Q

Pyloric sphincter

A

Sphincter between the stomach and the duodenum

39
Q

Brush-border enzymes

A

Present on the luminal surface of cells lining the duodenum and break down dimers and trimers of biomolecules into absorbable monomers –> released by presence of chyme

40
Q

Disaccharidases

A

Digest disaccharides: maltase digests maltose, isomaltase digests isomaltose, lactase digests lactose, and sucrase digests sucrose.

41
Q

Peptidases

A

Break down proteins (or peptides)

42
Q

Aminopeptidase

A

A peptidase secreted by glands in the duodenum that removes the N-terminal amino acid from a peptide

43
Q

Dipeptidases

A

Cleave the peptide bonds of dipeptides to release free amino acids.

44
Q

Enteropeptidase

A

An enzyme critical for the activation of trypsinogen, a pancreatic protease, to trypsin. It also activates procarboxypeptidases A and B to their active forms

45
Q

Secretin

A

A peptide hormone that causes pancreatic enzymes to be released into the duodenum. Also regulates the pH of the digestive tract by reducing HCl secretion from parietal cells and increasing bicarbonate secretion from the pancreas.

46
Q

Enterogastrone

A

Includes secretin; A hormone that slow motility through the digestive tract –> increases time for digestive enzymes to act on chyme

47
Q

Cholecystokinin (CCK)

A

A peptide hormone secreted in response to the entry of chyme into the duodenum –> stimulates the release of both bile and pancreatic juices and also acts in the brain, where it promotes satiety

48
Q

Bile

A

A complex fluid composed of bile salts, pigments, and cholesterol

49
Q

Bile salts

A

Derived from cholesterol: not enzymes but they emulsify fats and cholesterol into micelles. These micelles increase the surface area of the fats and prevent them from spontaneously separating out, allowing lipase to act.

50
Q

Pancreatic juices

A

A complex mixture of several enzymes in a bicarbonate-rich alkaline solution. The bicarbonate helps neutralize acidic chyme and provides ideal pH for digestive enzymes. Contains enzymes that digest carbs, fats, and proteins.

51
Q

Accessory organs of digestion

A

Pancreas, liver, and gallbladder. They all originate as outgrowths of endoderm from the gut tube during development.

52
Q

Acinar cells

A

Make up the bulk of the pancreas: exocrine cells that produce pancreatic juices.

53
Q

Pancreatic amylase

A

Breaks down large polysaccharides into small disaccharides and is therefore responsible for carb digestion

54
Q

Pancreatic peptidases (trypsinogen, chymotrypsinogen, and carboxypeptidases A and B)

A

Released in their zymogen form, but once activated are responsible for protein digestion.

55
Q

Pancreatic lipase

A

Breaks down fats into free fatty acids and glycerol

56
Q

Major and minor duodenal papillae

A

Ducts that empty into the duodenum and through which acinar cells secrete their products

57
Q

Liver’s location

A

Located in the upper right quadrant of the abdomen

58
Q

Liver’s functions

A

Include processing and synthesis of nutrients (glycogenesis and glycogenolysis, storage and mobilization of fats, gluconeogenesis), production of urea, detoxification of chemicals, production of bile, and synthesis of albumim and clotting factors

59
Q

Bile ducts

A

Connect the liver with both the gallbladder and small intestine: bile is produced in liver and travels down bile ducts where it may be stored in the gallbladder or secreted into the duodenum

60
Q

Hepatic portal vein

A

Vein through which the liver receives all blood draining from the abdominal portion of the digestive tract.
Nutrient-rich blood can be processed by the liver before draining into the inferior vena cava on its way to the right side of the heart.

61
Q

Bilirubin

A

Major pigment in bile, a byproduct of the breakdown of hemoglobin.

62
Q

Gallbladder

A

Located just beneath the liver and both stores and concentrates bile. Upon release of CCK, the gallbladder contracts and pushes bile out into the biliary tree

63
Q

Villi

A

Small, fingerlike projections from the epithelial lining of the small intestine

64
Q

Microvilli

A

Many are present on each villus –> drastically increases the surface area available for absorption

65
Q

Concentration gradient between blood and epithelial cells

A

Blood always has a lower concentration of monosaccharides and amino acids than inside the epithelial cells. Thus, simple carbs and amino acids diffuse from the epithelial cells into the capillaries –> absorbed molecules then go to the liver via the hepatic portal circulation.

66
Q

Chylomicrons

A

Packages for triglycerides and esterified cholesterol molecules

67
Q

How do chylomicrons enter the lymphatic circulation

A

through lacteals, which converge and enter the venous circulation at the thoracic duct in the base of the neck, which empties into the left subclavian vein.

68
Q

Where are vitamins absorbed

A

Small intestine

69
Q

What are the 4 fat-soluble vitamins

A

A, D, E, and K

70
Q

How are fat-soluble vitamins absorbed

A

They dissolve directly into chylomicrons to enter the lymphatic circulation

71
Q

How are water-soluble vitamins absorbed

A

They are taken up, along with water, amino acids, and carbohydrates, across the endothelial cells of the small intestine, passing directly into the plasma.

72
Q

How is water absorbed into blood

A

Transcellularly (across the cell membrane) and paracellularly (squeezing between cells)

73
Q

What is the primary function of the large intestine

A

Primarily involved in water absorption

74
Q

What are the 3 major sections of the large intestine

A

The cecum, the colon, and the rectum.

75
Q

Cecum

A

Simply an outpocketing that accepts fluid exiting the small intestine through the ileocecal valve and is the site of attachment of the appendix.

76
Q

Parts of the colon

A

Ascending, transverse, descending, and sigmoid colons

77
Q

Main function of colon

A

To absorb water and salts (such as sodium chloride) from the undigested material left over from the small intestine. –> material concentrated to form feces

78
Q

Purpose of rectum

A

Serves as a storage site for feces, which consists of indigestible material, water, bacteria, and certain digestive secretions that are not reabsorbed (enzymes and some bile).

79
Q

What are the 2 sphincters of the anus

A

The internal and external anal sphincters. External sphincter is under voluntary control (somatic), but the internal sphincter is under involuntary control (autonomic).

MCAT BIO my flashcards (15 decks)

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