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Physiology > Exam 3: Ch 18 Digestive System > Flashcards

Exam 3: Ch 18 Digestive System Flashcards

1
Q

Digestive System Overview

- Inside gastrointestinal (GI) tract, food is

A

broken down (digestion) by hydrolysis into molecular monomers

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2
Q

Digestive System Overview

- Absorption of monomers

A

occurs in small intestine

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3
Q

Digestive System Overview

- Ingested food molecules

A

are used to make ATP or to make additional tissue

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4
Q

Digestive System Overview

- Enzymes are required to

A
  • make polymers into monomers; usually only active in the lumen of the GI tract
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5
Q

Functions of GI Tract

A
  • Motility
  • Secretion
  • Digestion
  • Absorption
  • Storage and Elimination
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6
Q

Motility

A

movement of food through GI tract by means of:

  • ingestion
  • mastication
  • deglutition
  • peristalsis
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7
Q

Ingestion-

A

-taking food into mouth

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8
Q

Mastication–

A

chewing food & mixing it with saliva

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9
Q

Deglutition–

A

swallowing food

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10
Q

Peristalsis

A

–rhythmic wave-like contractions that move food through GI tract

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11
Q

Secretion

A

Includes release of exocrine & endocrine products into GI tract

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12
Q

Exocrine secretions include

A

HCl, H20, HC03-, bile, lipase, pepsin, amylase, trypsin, elastase, & histamine

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13
Q

Endocrine includes

A
  • hormones secreted into stomach & small intestine to help regulate GI system
    • E.g. gastrin, secretin, CCK, GIP, GLP-1, guanylin, VIP, & somatostatin
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14
Q

Digestion

A

breakdown of food molecules into their smaller subunits

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15
Q

Absorption

A

= passage of digested end products into blood or lymph

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16
Q

Storage and elimination

A

= Includes temporary storage & subsequent elimination of indigestible components of food

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17
Q

Digestive System

is composed of

A
  • GI tract (alimentary canal) & accessory digestive organs
  • GI tract is 30 ft long; extends from mouth to anus
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18
Q

Digestive system Organs include

A

oral cavity, pharynx, esophagus, stomach, & small & large intestine

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19
Q

Digestive system Accessory organs include

A

include teeth, tongue, salivary glands, liver, gallbladder, & pancreas

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20
Q

Bile is mostly

A

bile pigment, bile salts, phospholipids, cholesterol, and inorganic ions

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21
Q

Bile production is between

A

250 ml/day – 1500 ml/day

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22
Q

Bile pigment (bilirubin) is produced in

A

spleen, bone marrow, & liver

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23
Q

Bile pigment (bilirubin) is derivative of

A

heme groups (minus iron) from Hb

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24
Q

Bile pigment (bilirubin) is carried in

A

blood attached to albumin

25
Q

Free bilirubin combines with

A

with glucuronic acid to form conjugated bilirubin that is secreted into bile

26
Q

conjugated bilirubin converted by

A

intestinal bacteria to urobilinogen (produces the brown color of feces)

27
Q

30-50% of urobilinogen is absorbed by

A

by intestine & enters hepatic vein

28
Q

urobilinogen enters enterohepatic circulation to

A

to be recycled or filtered by kidneys & excreted in urine (produces amber color of urine)

29
Q

Bile acids are formed in

A

major breakdown pathway for cholesterol

30
Q

2 major bile acids

A
  • Cholic acid

- chenodeoxycholic acid

31
Q

Bile acids form bile salts by

A

combining with glycine or taurine, which aggregate as micelles

32
Q

combining with glycine or taurine, which aggregate as micelles

A

groups of molecules that are both hydrophobic and hydrophilic which allows them to surround hydrophobic molecules (emulsification)

33
Q

Bile salts recirculate (via

A

enterohepatic circulation ~ 6Xs/day)

34
Q

Liver - Detoxification of Blood

A

Liver can remove hormones, drugs, & other biologically active molecules from blood

35
Q

Liver - Detoxification of Blood by

A
  • excretion into bile
  • phagocytosis by Kupffer cells that line sinusoids
  • chemical alteration of molecules by hapatocytes
36
Q

Liver - Detoxification of Blood:

ammonia is produced by

A

deamination of aa’s; liver converts it to the less toxic urea which is excreted in urine

37
Q

Liver - Detoxification of Blood:

toxic purines

A

(Guanine and Adenine) are converted to uric acid

38
Q

Liver - Detoxification of Blood:

Liver conjugates

A

steroid hormones & xenobiotics (foreign biologically active molecules) with groups that make them anionic and hydrophilic, which can be transported into bile or urine by multispecific organic anion transport carriers & excreted

39
Q

Liver helps regulate

A
  • blood glucose by removing it from blood or releasing it to blood via glycogenesis & lipogenesis
    • Or produces it via glycogenolysis & gluconeogenesis
40
Q

Liver can also convert

A

free fatty acids into ketone bodies (ketogenesis) that can be used for energy during fasting

41
Q

Liver - Production of Plasma Proteins

-

A

Albumin & most of plasma globulins are produced by liver

42
Q

Albumin makes up

A

70% of total plasma protein & contributes most to colloid osmotic pressure of blood

43
Q

Globulins transport

A

cholesterol & hormones, inhibit trypsin (protease), & are involved in blood clotting

44
Q

Clotting factors

A

(fibrinogen) are also made in liver

45
Q

Hormone angiotensin

A

(causes vasoconstriction and has other affects)

46
Q

Most carbohydrates are ingested

A
  • asstarch
    • a polymer of glucose mostly:
      • sucrose = table sugar = glucose-fructose
      • lactose = glucose-galactose
47
Q

Salivary amylase

A

begins starch digestion

48
Q

Pancreatic amylase converts starch to

A
  • oligosaccharides

- Which are then hydrolyzed by SI brush border enzymes

49
Q

Protein digestion begins in

A

in stomach when pepsin digests proteins to form polypeptides

50
Q

In SI, endopeptidases (trypsin, chymotrypsin, elastase) cleave peptide bonds in

A

interior of polypeptides

51
Q

In SI exopeptidases (carboxypeptidase, aminopeptidase) cleave peptide bonds from

A

ends of polypeptides

52
Q

Protein digestion in SI results in

A

in free amino acids, dipeptides, & tripeptides, which are transported into SI cells where di- & tripeptides are broken down to amino acids, which are secreted into blood

53
Q

Digestion & Absorption of Lipids Occurs in

A

SI; arrival of lipids in duodenum causes secretion of bile

54
Q

Fat is emulsified by

A
  • bile salt micelles
  • Forms tiny droplets of fat isolated in bile salt micelles
  • greatly increases surface area for fat digestion by lipases
55
Q

Pancreatic lipase hydrolyzes

A

triglycerides to free fatty acids & monoglycerides

56
Q

Phospholipase A breaks down

A

phospholipids into fatty acids & lysolecithin (remainder of lecithin after 2 FAs have been removed)

57
Q

Free fatty acids, monoglycerides, & lysolecithin leave

A
  • micelles & enter epithelial cells, where they are resynthesized into triglycerides & phospholipids
    • not transported directly into blood like sugars and aa’s
58
Q

Triglycerides, phospholipids, and cholesterol combine with

A

a protein to form small particles called chylomicrons

which are secreted into central lacteals of SI villi

Physiology (27 decks)

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