Collagen

Elastin

Glands

Blood vessels of the gastrointestinal tract. 

Upper GI tract:

Striated m. of the upper 3rd of the esophagus, the wall of the stomach, small intestine and ascending colon

Lowe GI tract: 

Striated m. of the external anal canal and the the walls of the transverse, descending and sigmoid colon. 

75% afferent

25% efferent

A: 50%

E: 50 %

Serosa

Function:

Hormones (Endocrine cells)

Neurocrines 

Paracrines

Gastrin

CKK

Secretin

GIP (Glucose inhibitory peptide) 

Paracrines, also:

Act?

Examples:

Secreted by endocrine cells

Locally whitin the same tissue that secretes them

Diffusing (intestinal fluid/or carried short distances through capillaries) 

• Somatostatin
• Histamine (Not paracrine)

Neurocrine 

Also called bombesin

Gastrin:

Amino acid?

Where? 

which form is secreted inresponse to a meal?And between meals?

Both have?

Active peptide?

Secreted initated by?

17 amino acids

Antrum

G17(little gastrin) response to meal

G34: Between meals

Both have its own precursor, a progastrin molecule. 

Minimum fragment necessary for activity: 4 terminal C. Trp-met-Asp-Phe-NH2

Inhitated by: Small peptides + amino acids, distention of the stomach and vagal stimulation (gastrin releasing peptide)

Phenylalanine+tryptophan are the most potent stimuli for gastrin secretion. 

Duodenal ulcers

Inactivate pancreatic lipase--> Fat in the stool: steatorrhea 

Cholecytokinin 

Family?

Cells that secrete cck?

In response to?

33 Amino acids

Gastrin-cck family

5 c terminal identical to gastrin

(+gly)

Minimum fragment for biologic activity: 7

Has two recetors: CCK A(only for cck) CCK B: (cck+gastrin) 

I cells of Duodenal + jejunal mucosa

Small peptides/amino acids + Monoglyceride/fatty acids (NOT TG)

Contraction of Gall bladder and relaxation of sphincter of oddi 

Secretion of pancreatic enzymes

Secretion of Bicarbonate (potentiates secretion) 

Growth of exocrine pancreas 

Inhibition of gasric emtying

Secretin: 

Amino acids: 

Homologious to?Family

Cells that secrete secretin?

in response to? 

27: all amino acid are required for its biologic activity. Active in tertiary structure: alfa helix form. 

Glucogon: secretin-glucagon family 14/27 identical. 

S cells of duodeum

H+ and fatty acid

Inhitated phen ph smaller than 4,5

Secretin function: 

Essential for ?

Secretion of pancreatic + Biliary HC03-

Essential for fat digestion

Pancreatic lipase live in pH 6-8

Secretin also ihibits the effect of gastrin on the parietal cells. 

Glucose dependent insulinotropic peptide

Member of?

Cells

42 amino acid

Secretin-glucagon family

9 amino acid in common with secretin

16 amino acid common with glucagon

K cell of ducodemal an Jejunal mucosa

In response to: Glucose, amino acids and fatty acids. 

Stimulation of insulin secretion 

Also Inhibit Gastric H+ secretion. 

Motilin: Initate the interdigestive myoelectric complexes: 90 minutes intervals. 

Pancreatic polypeptide: In response to carbohydrates, protein and lipids. 

Physiologic role is uncertain.  

Enteroglucagon: Released in response to decreased blood glucose concentraton --> Glycogenolysis/gluconeogenesis. 

somatostatin:

Cell

in response to?

Function?

D cells, throughout the intestine

response to decreased luminal pH

Inhibit secretion of hormones, gastrin H+ secretion. 

Also secreted by the hyothalamus + by the delta cells of the endocrine pancreas. 

Neurocrines

Nonpeptide/peptides

Nonpeptides: Ach + norepinephrine

Peptides: VIP, GRP, Enkephalins, neuropeptide y, substance  

Phasic contraction: 

Tissues?

All tissues involve in mixing and propulsion

Esophagus, gastric antrum, small intestine 

Tonic contraction: 

Where?

Slow waves:

Frequency;

Not action potentials

Stomack (3 waves per minute)-Lowest

duodenum: 12 slow waves per min - highest.

Not influenced by neural or hormonal input, but can modulate both the production of action potential and the strengt of contraction. 

Cajal

abuntant in?