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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
Histamin stimulus
Gastrin
26
Histamin actions in the stomach
Increases pepsinogen secretion (parietal)
27
Secretin stimulus
Acidity, fat
28
Secretin actions in the stomach
Increases pepsinogen secretion (Chief) Increases HCO3 (Brunner glands)
29
Somatostatin stimulus
Acidity
30
Somatostain actions in the stomach
Decreases HCl secretion (Parietal) Decreases emptying Decreases G cells, pancreatic secret, biliary secret, blood flow
31
Cholecystokinin (CCK) stimulus
Fat, proteins
32
Cholecystokinin (CKK) actions in the stomach
Increases HCl secretion (Parietal) Decreases emptying Increases gallbladder contraction Increases pancreatic secretion
33
Secretion in duodenum is done through
Brunner glands
34
Brunner glands function
Secretion of alkaline mucous, in order to protect the epithelial lining
35
Stimuli for secretion (Brunner glands)
Touch, distension or irritants PS nervous system stimulation (through X CN, vagus nerve) Secretin
36
Inhibition of secretion (Brunner glands)
Sympathetic nervous system
37
Secretion along the small intestine occurs through cells located in
Lieberkühn intestinal crypts
38
Cell types in Lieberkühn intestinal crypts
Enterocytes Goblet cells Paneth cells Stem cells Endocrine cells: S, I, D
39
Enterocytes functions
Secrete water and electrolytes (Cl), enzymes for digestion Absorb the digested products
40
Paneth cells function
Antimicrobial defense (defensins, lysozyme & PPL-A2)
41
Endocrine cells in Lieberkühn intestinal crypts
S cells → release secretin I cells → release cholecystokinin D cells —> release somatostatin
42
Mechanism of water secretion
Cl- and HCO3- actively transported Na+ diffuses passively into lumen Water gets dragged along with the diffusing Na+
43
Enzymes secreted by enterocytes
Peptidases Sacrase, maltase, isomaltase, lactase Intestinal lipase
44
Large intestine differences with small intestine
Lieberkühn crypts but NO intestinal villi More mucus (Goblet) cells Enterocytes don’t produce digestive enzymes and secrete little fluid
45
Large intestine main function
Absorption of: water, electrolytes and vitamins (B complex) (We also find secretory processes —> to secrete Cl ions)
46
Absorption in large intestine is stimulates by
PS system
47
The function of mucus in large intestine
Protection Feces cohesion
48
Exocrine pancreas cells
Ductal cells Acinar cells
49
Ductal cells
Coat inter + intralobular ducts, and main pancreatic duct
50
Acinar cells
Form glands Secrete their contents into the pancreatic ducts.
51
Stimulating pancreas hormones
Secretin —> activarte ductal cells to produce HCO3- CCK —> activate acinar cells to produce digestive enzymes
52
Acinar cells main function
Digestion
53
Ductal cells main function
Hydration and alkalinization (protects against ulceras + sets optimal pH for pancreatic enzymes to be active)
54
Intracellular HCO3- (ductal secretions) comes from
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
Intracellular HCO3- (ductal secretions) function
Reacts w/ HCl to neutralize pH HCl + NaHCO3 → NaCl + H2CO3 - H2CO3 —> H2O + CO2 - CO2 —> circulation —> respiration = stomach acid is neutralized
56
Stimuli for HCO3- secretion
Secretin Ach (PS)
57
Pancreas
Organ which secretes most enzymes per gram of tissue
58
Acinus glands produce and secrete
Enzymes (proteolytic) (accumulate on apical side and are released by exocytosis)
59
Acinar secretions regulators
Pro-colipase Monitor peptide Trypsin inhibitor
60
Acinar secretions stimuli
CKK (fatty acids + Aa, nervous system stimulation: CKK-releasing peptide and monitor peptide
61
Proteolytic enzymes
1º) Acini (trypsinogen + trypsininhibitors) 2º) Small intestine (tripsinogen —> trypsin by enterokinase) 3º) Dudenum (rest of zymogens —> active form by trypsin)
62
Gallbladder function
Stores bile produced by the liver and release it to the duodenum through Ampulla of Vater
63
Bile composition
Water Bile salts (main one) Phospholipids Cholesterol Bile pigments (bilirubin) Na+, HCO3- and other electrolytes
64
Formation bile salts
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
How do bile salts emulsify / break down large fat globules into small emulsified droplets?
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
Bile salts characteristic
Amphipatic —> assemble into micelles = emulsify / break down large fat globules into small emulsified droplets
67
Functions of bile
Helps digestion Facilitates fat emulsion and solubilization —> absorption Alkalinization of the duodenal lumen Metabolic byproducts + excretion (bilirrubin, excess cholesterol)
68
Formation canalicular secretion
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
Formation ductular secretion
Composition = modified (secretion of water and HCO3). Ductal cells hydrate and alkalize the bile.
70
Secretion bile into ducts
Bile descends through common hepatic duct —> cystic duct —> gallbladder (not an essential structure)
71
Stimuli for bile secretion
CCK = gallbladder contraction, sphincter of Oddi relaxation Ach PS system
72
Phases biliary secretion
Cephalic phase Intestinal phase
73
Cephalic phase (biliary secretion) - stimuli, response, result
Stimuli: food smell, touch, taste, sight Response: Oddi sphincter relaxation (X CN) Result: anticipation bile to chyme (duodenum)
74
Intestinal phase (biliary secretion) - stimuli, response, result
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
Enterohepatic circulation function
Bile acids and bilirrubin recycle
76
Enterohepatic circulation of bile salts - %, pathway
95% recycled, 5% through feces Full field function —> portal circulation —> Na+/bile cotransporters in basolat side of enterocytes
77
Enterohepatic circulation of bilirrubin
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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