A secreção gástrica

A secreção gástrica

extraído de: Vander, Sherman & Luciano, 2002 – WEBsite original: http://www.biocourse.com/mhhe/bcc/domains/quad/topic.xsp?id=000270

http://www.cristina.prof.ufsc.br/digestorio/digestivo_cap17_vander_03766_biocourse_mcgrawhill.ppt

http://www.biocourse.com/mhhe/bcc/domains/quad/topic.xsp?id=000270

Veja mais em: http://mcb.berkeley.edu/courses/mcb136/topic/Gastrointestinal/Secretion_in_GI-Tract/

http://mcb.berkeley.edu/courses/mcb136/topic/Gastrointestinal/Secretion_in_GI-Tract/

http://anatomy.iupui.edu/courses/histo_D502/D502f03/f03_labs/Lab11/Lab11f03.html

células mucosas

células principais

células parietais

muco e HCO3-

pepsinogênio

HCl e Fator Intrínseco

SECREÇÕES EXÓCRINAS

http://anatomy.iupui.edu/courses/histo_D502/D502f03/f03_labs/Lab11/Lab11f03.html



SECREÇÕES GÁSTRICAS



Interações das secreções gástricas

mucous




The protection provided to the mucosal surface of the stomach by the bicarbonate-containing mucus layer is known as the gastric mucosal barrier. In man, the mucus layer is about 0.2 mm thick. Buffering by the bicarbonate-rich secretions of the surface epithelial cells and the restraint to convective mixing caused by the high viscosity of the mucus layer allow the pH at the cell surface to remain near 7, whereas the pH in the gastric juice in the lumen is 1 to 2.

COX1: atividade ciclooxigenase da PGH2-sintase). Berne et al., 2004 e outros: http://meds.queensu.ca/medicine/physiol/undergrad/phase2/phase2e/Ph2acid.htm

secreção de muco e HCO3- pelas

células epiteliais e mucosas

fluxo sangüíneo

camada mucosa (0,2mm)

Proteção mucosa

ACh(PS e SNE)

http://meds.queensu.ca/medicine/physiol/undergrad/phase2/phase2e/Ph2acid.htm

Mecanismos intracelulares de secreção ácidagástrica (célula parietal)




Model for the regulation of gastric acid secretion. Shown are a parietal cell, an ECL cell, a D cell, and many of the important regulators of acid secretion. Parietal cells are stimulated by three main agonists: gastrin, histamine, and ACh. Gastrin binds to CCKB (gastrin/cholecystokinin-B)receptors on the parietal cell to evoke an increase in

intracellular calcium; histamine binds to H2 receptors, which primarily signal through increased cAMP; ACh binds to M3 receptors to stimulate an increase in intracellular

calcium. Parietal cell stimulation results in movement of H+/K+-ATPase pumps to the apical membrane to secrete acid. Histamine is released from ECL cells in response to gastrin stimulation as well as neuronal stimulation via PACAP (pituitary adenylate cyclase-activating polypeptide). Somatostatin (Sst) released from D cells inhibits acid secretion by reducing ECL cell histamine release, blocking gastrin release, and directly inhibiting parietal cell acid secretion. Annual Review of Physiology March 2003, Vol. 65, pp. 383-400 Samuelson and Hinkle, 2003

Regulação da secreção ácida gástrica

Olbe, Carlsson & Lindberg, 2003. Nature Reviews Drug Discovery 2, 132-139 (2003) http://www.nature.com/cgi-taf/DynaPage.taf?file=/nrd/journal/v2/n2/full/nrd1010_r.html

Regulação da secreção ácida gástrica e ações de drogas anti-ácidas:

http://www.nature.com/cgi-taf/DynaPage.taf?file=/nrd/journal/v2/n2/full/nrd1010_r.html

Regulação da secreção ácida gástricana fase cefálica

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/stomach/index.html


Regulação da secreção ácida gástricana fase gástrica



SECREÇÕES EXÓCRINASPANCREÁTICA E HEPÁTICA

http://www.nlm.nih.gov/medlineplus/ency/imagepages/1090.htm


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VOLUME SECRETADO PELO

PÂNCREAS NO INTESTINO DELGADO:

1,5 L/DIA

secreção hidro-eletrolítica

enzimas digestivas(proteases,

amilase e lipases)

Principais tipos celulares encontrados no pâncreas

Ilhotas de Langerhanshormônios: insulina (cél. β),

glucagon (cél. α), somatostatina (cél. δ) e polipeptídeo pancreático (cél. θ)

ilhota (células alfa: glucagon) ilhota (células beta: insulina)

ácinos e ilhota de Langerhanshttp://www.udel.edu/Biology/Wags/histopage/histopage.htm

HISTOLOGIA DO PÂNCREAS

PORÇÃO ENDÓCRINA (hormônios: glucagon, insulina, somatostatina e polipeptídeo pancreático)

PORÇÃO EXÓCRINA enzimas e secreção hidroeletrolítica

http://www.gastroslides.org/main/browse_deck.asp?tpc=6&mxpg=390&pg=2241#image

http://www.udel.edu/Biology/Wags/histopage/histopage.htm


The relationships and major features of the units of the exocrine pancreas. The pancreatic acinar cells of the acinus have prominently stained zymogen granules in the apical area of the cell. The connecting ductule does not contain zymogen granules. The blue cell in the cartoon depicts the centroacinar cell at the border between the acinus and ductule. The centroacinar cell functions similarly to the duct cell. The major secretory products of the acinus are digestive proenzymes and enzymes with lesser amounts of water and ions. The major secretory products of the duct are water and ions.


AS SECREÇÕES EXÓCRINAS PANCREÁTICAS: água e eletrólitos


The relationships and major features of the units of the exocrine pancreas. The pancreatic acinar cells of the acinus have prominently stained zymogen granules in the apical area of the cell. The connecting ductule does not contain zymogen granules. The blue cell in the cartoon depicts the centroacinar cell at the border between the acinus and ductule. The centroacinar cell functions similarly to the duct cell. The major secretory products of the acinus are digestive proenzymes and enzymes with lesser amounts of water and ions. The major secretory products of the duct are water and ions.


AS SECREÇÕES EXÓCRINAS PANCREÁTICAS: água e eletrólitos


Neutralization of gastric acid delivered to the duodenum is necessary for optimal digestion and absorption of a meal. Several mechanisms that are not shown are involved in the neutralization process. First, the meal provides buffers from digestion of protein and triglycerides. That is, the peptides and fatty acid products act as pH buffers. Another neutralization process is absorption of hydrogen ion by the duodenal mucosa. Finally, the pancreas, biliary system and duodenal mucosa secrete bicarbonate into the duodenal lumen for neutralization.


Importância da secreção hidroeletrolítica pancreática, rica em HCO3

-, Na+ e água na digestãoNaHCO3 + HCl NaCl + H2O + CO2 (reabsorção)


The relationships and major features of the units of the exocrine pancreas. The pancreatic acinar cells of the acinus have prominently stained zymogen granules in the apical area of the cell. The connecting ductule does not contain zymogen granules. The blue cell in the cartoon depicts the centroacinar cell at the border between the acinus and ductule. The centroacinar cell functions similarly to the duct cell. The major secretory products of the acinus are digestive proenzymes and enzymes with lesser amounts of water and ions. The major secretory products of the duct are water and ions. http://www.gastroslides.org/main/browse_deck.asp?tpc=6&mxpg=390&pg=2243#image

AS SECREÇÕES EXÓCRINAS PANCREÁTICAS: ENZIMAS


(from duodenal epithelial cells)

-Amylase (no activation needed)

secreted by duodenal epithelium

(Enterokinase)

http://mcb.berkeley.edu/courses/mcb136/topic/Gastrointestinal

AS SECREÇÕES EXÓCRINAS PANCREÁTICAS: enzimas

lipase




(Enterokinase)



lipase

Relative amounts (by weight) of the different classes of pancreatic digestive enzymes. Proteases are the most abundant class of enzymes.





(Enterokinase)



lipase

ALFA-AMILASE PANCREÁTICA:

Lipase pancreática

A secreção serosa pancreática: lipase pancreática

A secreção serosa pancreática: alfa-amilase

Amilopectina (amido) da batata

maltose dextrina-limite

ligação 1:6ligação 1:4

maltotriosealfa-amilase

Produtos da hidrólise do AMIDO pela alfa-amilase glicose

OBS: reparou que é a mesma ação da alfa-amilase salivar?

Vander, Sherman e Luciano, 1997

A secreção serosa pancreática:a ativação das pró-proteases pancreáticas no intestino

delgado pela enteroquinase (da borda-em-escova)




PRÓ-PROTEASES PANCREÁTICAS:

Tripsinogênio TripsinaENTEROQUINASE

QuimotripsinogênioPro-carboxipeptidases A e B

QuimotripsinaCarboxipeptidases

pró-proteases pancreáticas: proteases pancreáticas:

ATIVAÇÃO DAS ENZIMAS PROTEOLÍTICAS PANCREÁTICAS

A secreção serosa pancreática:a ativação das pró-proteases pancreáticas no intestino

delgado pela enteroquinase (da borda-em-escova)

EnzimasNa+, Cl-,

HCO3-, K+ e

H2O

Na+Cl- HCO3-K+

EnzimasNa+, Cl-,

HCO3-, K+ e

H2O

ductos intercalares células acinares

CCKCCK

SecretinaSecretina

H2O

+

+

AS SECREÇÕES EXÓCRINAS PANCREÁTICAS

REGULAÇÃO DA SECREÇÃO EXÓCRINA PANCREÁTICA

estimulação hormonal pancreática

A presença de gordura e de ácido no duodeno estimula a secreção endócrina intestinal das células endócrinas “S” e “I”.

As céls. “S” secretam a SECRETINA que estimula a secreção hidro-eletrolítica dos ductos pancreáticos

This image shows the stimulants for release of CCK from I cells and secretin release from S cells. Of note, the I cells and S cells “taste” the specific stimulants in the lumen of the gut to activate release of the hormones. The released CCK can mediate pancreatic secretion by either activating vagal sensory afferents that results in stimulation of pancreatic acinar cell secretion though a vago-vagal reflex involving the CNS or through the circulation (i.e. hormonal action). Secretin also acts through neural (not shown) and hormonal pathways on the pancreas stimulating secretion from both ductal cells and acinar cells. http://www.gastroslides.org/main/browse_deck.asp?tpc=2&mxpg=390&pg=1842#image

A REGULAÇÃO DA SECREÇÃO DOS DUCTOS PELA SECRETINA

REGULAÇÃO DA SECREÇÃO EXÓCRINA PANCREÁTICA

estimulação hormonal pancreática

A presença de gordura e de ácido no duodeno estimula a secreção endócrina intestinal das células endócrinas “S” e “I”.

As céls. “I” secretam a CCKque estimula a secreção serosa dos ácinos pancreáticos

This image shows the stimulants for release of CCK from I cells and secretin release from S cells. Of note, the I cells and S cells “taste” the specific stimulants in the lumen of the gut to activate release of the hormones. The released CCK can mediate pancreatic secretion by either activating vagal sensory afferents that results in stimulation of pancreatic acinar cell secretion though a vago-vagal reflex involving the CNS or through the circulation (i.e. hormonal action). Secretin also acts through neural (not shown) and hormonal pathways on the pancreas stimulating secretion from both ductal cells and acinar cells. http://www.gastroslides.org/main/browse_deck.asp?tpc=2&mxpg=390&pg=1842#image

A REGULAÇÃO DA SECREÇÃO DOS DUCTOS PELA CCK

Regulação das secreção exócrina pancéática (ductos e ácinos) pelos hormônios intestinais

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pancreas/control.html

http://arbl.cvmbs.colostate.edu/hbooks/pathphys/digestion/pancreas/control.html

The graphic in this image depicts the neurotransmission systems and neurotransmitters involved in regulating acinar and ductal secretion. The blue cell is called a centroacinar cell. These cells have characteristics more similar to ductal cells although their exact function is not known. Vagal efferents activate neurons in the intrapancreatic ganglia. Neurons from the ganglia then have processes that are in proximity to the parenchymal cells. These processes release the neurotransmitters, acetylcholine (Ach), gastrin releasing peptide (GRP) and vasoactive intestinal polypeptide (VIP) when their neurons are activated. Ach causes secretion from both acinar cells and ducts while all three neurotransmitters can cause secretion from acinar cells.


toxinas de escorpiõesinseticidas organofosforados

Exposição a inseticidas organofosforados (inibidores da acetilcolinesterase) ou toxinas específicas de escorpiões causam um aumento nos níveis de liberação de acetilcolina nas terminações nervosas, podendo causar pancreatite. A picada do escorpião Tityus serrulatus também tem sido causa de pancreatite.

(G. Robles-Diaz, Mexico).

RELEVÂNCIA CLÍNICA DE TAIS CONHECIMENTOS


A secreção exócrina hepática



Bile is a digestive fluid secreted by the liver and stored in the gallbladder which normally is released into the duodenum portion of the small intestine through the sphincter of Oddi. Bile, released after a meal containing fats, aids in absorption and digestion of the fat.

A secreção exócrina hepática: a bile





Função digestiva da bile: sais biliares




Sais biliares e a emulsificação das gorduras




Sais biliares e a emulsificação das gorduras:a formação das micelas para a digestão pela lipase pancreática

MICELA




Resumo da emulsificação, digestão e absorção de gordura




A circulação êntero-hepática dos sais biliares




REGULAÇÃO DA SECREÇÃO BILIARProdução de bile+circulação êntero-hepática dos sais biliares e esvaziamento da vesícula biliar e relaxamento de Oddi pela CCK

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A secreção exócrina intestinal:mucosa e hidroeletrolítica

Enzimas do intestino delgado:enzimas da borda-em-escova (constitucionais)

para a digestão final de proteínas e carbohidratos




Enzimas do intestino delgado:enzimas da borda-em-escova (constitucionais)

para a digestão final de proteínas e carbohidratos

A secreção exócrina intestinal:mucosa e hidroeletrolítica

LARGE INTESTINE

célula parietal

absorção da Vitamina B12

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http://www.uq.edu.au/vdu/HDUAnaemiaMegaloblastic.htm e http://www.animatedmedical.com/Pernanem/pernanem.html e http://www-ermm.cbcu.cam.ac.uk/03006434h.htm

Fator Intrínseco e a absorção da Vit. B12

http://www.uq.edu.au/vdu/HDUAnaemiaMegaloblastic.htm

http://www.animatedmedical.com/Pernanem/pernanem.html

http://www-ermm.cbcu.cam.ac.uk/03006434h.htm

Células “G” secretoras de GASTRINA

http://calloso.med.mun.ca/~tscott/digest/digtut.htm

http://calloso.med.mun.ca/~tscott/digest/digtut.htm

Regulação da secreção ácida gástricana fase intestinal



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A secreção gástrica