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Digestivo > Secretion > Flashcards

Secretion Flashcards

1
Q

Oral mucosa and esophagus epithelium

A

Stratified squamous non-keratinized epithelium
(Mouth: also salivary glands // esophagus: glands, muscularis mucosae)

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2
Q

Stomach, intestine and colon epithelium

A

Columnar epithelium
(Small intestine: microvilli, villi -> crypts // colon: taeniae coli, haustras)

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3
Q

Transition site between simple squamous and columnar epithelium in GI tract

A

Cardias

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4
Q

Types of secretory glands

A

Unicelular (goblet cells)
Multicellular (exocrine or endocrine)

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5
Q

Unicelular glands

A

Part of a columnar epith

Mucous cells of stomach, globet cells from small and large intestine

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6
Q

Exocrine glands - location, secretes into, types

A

Inside submucosa / distant epith-related glands (pancreas, parotid)

Secrete the content into GI epithelium

Gastric glands (principal and parietal cells)
Duodenal glands of Brunner (mucinous cells)
Intestinal crypts of Lieberkühn (Paneth cells)
Salival glands (acinar cells)
Exocrine pancreas

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7
Q

Endocrine glands - location, secretes into, types

A

Outside epithelium

Secrete their content to the blood flow

Endocrine (alfa cells, beta cells)
Thyroid (follicular cells)
Parathyroid (principal, oxyphillic cells)
Adrenal, hypophysis
Ovaries, testicles

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8
Q

Process of secretion

A

Nutrients enter from capillary vessels into epithelial cells = glands through their basal membrane

Proteins are synthesized, folded and modified

Terminal vesicles of Golgi will form granules

When a hormone or nervous system signal arrives, the vesicles will be released through the apical side of the cells

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9
Q

Salivary secretions

A

Serosa
- by parotid and submaxillary
- contains Ptialine (amylase) and lingual lipase

Mucinous
- by sublingual and submaxillary
- contains mucous (protection and lubrication)

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10
Q

Salivary content

A

K and Bicarbonate
Na and Cl
Thiocyanate ions
Lysozyme
IgA

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11
Q

Salival secretions

A

1ª secretion
2ª secretion (modification of 1ª = rich in K + bicarbonate)

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12
Q

Stimuli for salivary secretion

A

Tongue: touch (general), taste (specific)

Info —> IX & VII CN branches —> sensory nuclei in NTS —>
- Cortex (to a region related to taste)
- Amygdala

Signal reaches hypothalamus - connects with sup and inf salivary nuclei (gastric reflex also activates them)

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13
Q

Efferent pathway from salivary nuclei

A

VII CN —> submandibular ganglion —> submandibular + sublingual glands

IX CN —> otic ganglion —> Parotid gland

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14
Q

Gastric / oxyntic glands secretory cells

A

Mucous or Principal cells → Mucus (bicarbonate)

Parietal cells → HCl = gastric acid (pH = 1-3 —> activates digestive enzymes) + Intrinsic factor (for VitB12)

Chief cells → Pepsinogen (inact) into Pepsin (act) = prot breakdown

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15
Q

Pyloric / Tubular glands endocrine cells

A

G cells: gastrin
D cells: somatostatin
Enterochromaffin-like cells (ECL): histamine

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16
Q

Stimulation / inhibition gastric secretions

A

G cells (gastrin) stimulates parietal cells (HCl)
D cells inhibit G cells (gastrin) = inhibition of parietal cells (HCl)

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17
Q

Mechanism of HCl secretion by parietal cells

A

Protons —> H+/K+ ATPase
- Needs retrodiffusion of K to lumen by passive gradient
- Needs act transport of K from interstitium (Na+/K+ pump)

Carbonic Anhydrase producing HCO3- is pumped to interstitium by cotransporter Cl-/HCO3-

Cl- will pass to the lumen through passive gradient

Cl- and H+ will combine in the lumen = HCl

Water will diffuse by osmotic gradient to the lumen

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18
Q

Stimuli for acid secretion

A

Acetylcholine —> PS nervous system (vagus nerve) which innervates parietal cells

Gastrin —> reaches parietal cells via circulation. Released upon distension, Aa in stomach, vagus stimulation,… Indirectly stimulates H+ secretion by ↑ histamine

Histamine —> reaches nearby parietal cells through paracrine diffusion

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19
Q

Phases of gastric secretion

A

Cephalic phase
- 30%
- stimuli: taste, smell, chewing, swallowing, conditional reflexes
- direct vagal stimulation or indirect

Gastric phase
- 60%
- stimuli: gastric distension, presence of peptides,…
- direct / indirect (gastrin) vagal stimulation, Aa induced Gastrin release,…

Intestinal phase
- 10%
- mediated by prot digestion products

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20
Q

PS-NS stimulus

A

Distension

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21
Q

PS-NS action in stomach

A

Increases HCL (parietal)
Increases pepsinogen (chief)
Promotes emptying
Promotes relaxation of pylorus (VIP)

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22
Q

PS-NS origin

A

Dorsal Nucleus
Vagus - Myenteric plexus

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23
Q

Gastrin stimulus

A

Distension
Proteins

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24
Q

Gastrin actions in the stomach

A

Increases HCL (parietal)
Increases pepsinogen (chief)
Increases histamin (ECL)
Promotes emptying
Promotes relaxation of pylorus (VIP)

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25
Q

Histamin stimulus

A

Gastrin

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26
Q

Histamin actions in the stomach

A

Increases pepsinogen secretion (parietal)

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27
Q

Secretin stimulus

A

Acidity, fat

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28
Q

Secretin actions in the stomach

A

Increases pepsinogen secretion (Chief)
Increases HCO3 (Brunner glands)

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29
Q

Somatostatin stimulus

A

Acidity

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30
Q

Somatostain actions in the stomach

A

Decreases HCl secretion (Parietal)
Decreases emptying
Decreases G cells, pancreatic secret, biliary secret, blood flow

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31
Q

Cholecystokinin (CCK) stimulus

A

Fat, proteins

32
Q

Cholecystokinin (CKK) actions in the stomach

A

Increases HCl secretion (Parietal)
Decreases emptying
Increases gallbladder contraction
Increases pancreatic secretion

33
Q

Secretion in duodenum is done through

A

Brunner glands

34
Q

Brunner glands function

A

Secretion of alkaline mucous, in order to protect the epithelial lining

35
Q

Stimuli for secretion (Brunner glands)

A

Touch, distension or irritants
PS nervous system stimulation (through X CN, vagus nerve)
Secretin

36
Q

Inhibition of secretion (Brunner glands)

A

Sympathetic nervous system

37
Q

Secretion along the small intestine occurs through cells located in

A

Lieberkühn intestinal crypts

38
Q

Cell types in Lieberkühn intestinal crypts

A

Enterocytes
Goblet cells
Paneth cells
Stem cells
Endocrine cells: S, I, D

39
Q

Enterocytes functions

A

Secrete water and electrolytes (Cl), enzymes for digestion
Absorb the digested products

40
Q

Paneth cells function

A

Antimicrobial defense (defensins, lysozyme & PPL-A2)

41
Q

Endocrine cells in Lieberkühn intestinal crypts

A

S cells → release secretin
I cells → release cholecystokinin
D cells —> release somatostatin

42
Q

Mechanism of water secretion

A

Cl- and HCO3- actively transported
Na+ diffuses passively into lumen
Water gets dragged along with the diffusing Na+

43
Q

Enzymes secreted by enterocytes

A

Peptidases
Sacrase, maltase, isomaltase, lactase
Intestinal lipase

44
Q

Large intestine differences with small intestine

A

Lieberkühn crypts but NO intestinal villi
More mucus (Goblet) cells
Enterocytes don’t produce digestive enzymes and secrete little fluid

45
Q

Large intestine main function

A

Absorption of: water, electrolytes and vitamins (B complex)
(We also find secretory processes —> to secrete Cl ions)

46
Q

Absorption in large intestine is stimulates by

A

PS system

47
Q

The function of mucus in large intestine

A

Protection
Feces cohesion

48
Q

Exocrine pancreas cells

A

Ductal cells
Acinar cells

49
Q

Ductal cells

A

Coat inter + intralobular ducts, and main pancreatic duct

50
Q

Acinar cells

A

Form glands
Secrete their contents into the pancreatic ducts.

51
Q

Stimulating pancreas hormones

A

Secretin —> activarte ductal cells to produce HCO3-
CCK —> activate acinar cells to produce digestive enzymes

52
Q

Acinar cells main function

A

Digestion

53
Q

Ductal cells main function

A

Hydration and alkalinization (protects against ulceras + sets optimal pH for pancreatic enzymes to be active)

54
Q

Intracellular HCO3- (ductal secretions) comes from

A

Circulation (Na+/HCO3- cotransp in basolat membrane)

Intracellular production: CO2 + H2O by Carbonic Anhydrase = HCO3- & H+:
- H+ —> interstitium (Na+/H+ exchanger in basolat membr)
- HCO3- —> lumen (Cl- / HCO3- exchanger: Cl from acinar secretions & ductal cells, which secrete Cl- using CFTR)

55
Q

Intracellular HCO3- (ductal secretions) function

A

Reacts w/ HCl to neutralize pH

HCl + NaHCO3 → NaCl + H2CO3
- H2CO3 —> H2O + CO2
- CO2 —> circulation —> respiration = stomach acid is neutralized

56
Q

Stimuli for HCO3- secretion

A

Secretin
Ach (PS)

57
Q

Pancreas

A

Organ which secretes most enzymes per gram of tissue

58
Q

Acinus glands produce and secrete

A

Enzymes (proteolytic)
(accumulate on apical side and are released by exocytosis)

59
Q

Acinar secretions regulators

A

Pro-colipase
Monitor peptide
Trypsin inhibitor

60
Q

Acinar secretions stimuli

A

CKK (fatty acids + Aa, nervous system stimulation: CKK-releasing peptide and monitor peptide

61
Q

Proteolytic enzymes

A

1º) Acini (trypsinogen + trypsininhibitors)
2º) Small intestine (tripsinogen —> trypsin by enterokinase)
3º) Dudenum (rest of zymogens —> active form by trypsin)

62
Q

Gallbladder function

A

Stores bile produced by the liver and release it to the duodenum through Ampulla of Vater

63
Q

Bile composition

A

Water
Bile salts (main one)
Phospholipids
Cholesterol
Bile pigments (bilirubin)
Na+, HCO3- and other electrolytes

64
Q

Formation bile salts

A

Liver: colesterol —> 2 1º bile acids
Intestine: 2 1º bile acids deoxygenated = 2º bile acids

Aa, Na, K conjugated to 1º,2º bile acids = bile salts (8)

65
Q

How do bile salts emulsify / break down large fat globules into small emulsified droplets?

A

Fragmentat/Emulsificat = larger surface area for enzymes (mainly pancreatic lipase) —> fatty acids + monoglyc.

Solubilization and Absorption: keeping them in solution + transporting them to enterocytes —> absorbe

66
Q

Bile salts characteristic

A

Amphipatic —> assemble into micelles = emulsify / break down large fat globules into small emulsified droplets

67
Q

Functions of bile

A

Helps digestion
Facilitates fat emulsion and solubilization —> absorption
Alkalinization of the duodenal lumen
Metabolic byproducts + excretion (bilirrubin, excess cholesterol)

68
Q

Formation canalicular secretion

A

Composition = same as bile —> exit into canaliculi through:

  • BSEP (bile salts transporter. MOST important)
  • MDR3 (phospholipid transporter)
  • MDR2 (xenobiotics)
  • MRP2 (act secretes glutathione and conjugated bilirubin)

(Act transporters + passive diffusion of water + other substances)

69
Q

Formation ductular secretion

A

Composition = modified (secretion of water and HCO3).
Ductal cells hydrate and alkalize the bile.

70
Q

Secretion bile into ducts

A

Bile descends through common hepatic duct —> cystic duct —> gallbladder (not an essential structure)

71
Q

Stimuli for bile secretion

A

CCK = gallbladder contraction, sphincter of Oddi relaxation
Ach
PS system

72
Q

Phases biliary secretion

A

Cephalic phase
Intestinal phase

73
Q

Cephalic phase (biliary secretion) - stimuli, response, result

A

Stimuli: food smell, touch, taste, sight
Response: Oddi sphincter relaxation (X CN)
Result: anticipation bile to chyme (duodenum)

74
Q

Intestinal phase (biliary secretion) - stimuli, response, result

A

Stimuli: intestinal cells detect Aa + proteins
Response: I cells release CKK (duodenum)
Result: cholagoge act (gallbladder contracts + Oddi sphincter relaxation)

Stimuli: intestinal cells detect fat
Response: S cells release secretin (duodenum)
Result: choleretic act (hepatocytes increase bile, ductal cells increase HCO3-, H2O)

75
Q

Enterohepatic circulation function

A

Bile acids and bilirrubin recycle

76
Q

Enterohepatic circulation of bile salts - %, pathway

A

95% recycled, 5% through feces

Full field function —> portal circulation —> Na+/bile cotransporters in basolat side of enterocytes

77
Q

Enterohepatic circulation of bilirrubin

A

RBC pahagocitosed —> heme group into indirect bilirrubin —> blood (bound to albumin)

Liver: indirect bilirubin conjugated w/ glucuronic acid = direct bilirubin —> bile

Intestine: bacteria hydrolyzes and reduce bile (w/conjugated bilirubin) = urobilinogen —>
- flow through GI tract: bacteria —> stercobilin (feces colour)
- reabsorbed into enterohepatic circulation: kidneys (urobilin —> urine colour) / liver (recycled, sent back to intestine)

Digestivo (4 decks)

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