Accessory organs & Secretions

Anatomy of liver

-Anterior Inferior Vena cava Gallbladder -Inferior Hepatic ducts Hepatic portal vein Hepatic artery Gallbladder

Describe the large intestine secretions.

-Bacterial contributions -Fecal matter contents

secretin

-Hormone capable of stimulating secretion by the pancreas and liver. -Produced & released by the duodenum -Decrease gastric secretions in the stomach -Stimulates pancreas to release pancreatic juice, rich in bicarbonate -Stimulates the release of bile

What are the functions of hepatocytes

-Make: BILE -Store: Glycogen, fat, vitamins, Copper & iron -Nutrient metabolism: Amino Acids, & Vitamin D -Detox: Ammonia converted to urea, and remove drugs -Phagocytosis: Old Red & white blood cells & some bacteria -Synthesis of proteins: Albumin, fibrinogens, globulins, heparin, clotting factors

How is pepsin activated?

-Packed in zymogen granules -The presence of HCL and pepsin converts pepsinogen to pepsin -Pepsin catalyzes hydrolysis of peptide bonds in ingested proteins

disaccharides

-Pancreatic Amylase breaks down Short chains into disaccharides -Brush border enzymes breakdown disaccharides into simple sugars

Endocrine pancreas

-Pancreatic islets Make insulin, glucose & stomatostatin -Islets of Langerhans -alpha cells secrets glucagon -beta cells secrete insulin

What is the overall effect of bacterial action?

-Release gases -Help absorb Vitamine K -Contribute short chain fatty acids from soluble fibers

functions of bile

-Release stimulated by secretin Neutralizes & dilutes stomach acids Emulsifies lipids Recycled by enterohepatic circulation

gallbladder

-Sac to store Bile mucosa (folded into rugae) inner muscularis outer serosa -Bile arrives constantly from liver, stores, concentrates

Oral cavity secretions

-Saliva: moistens food, neutralizes acids, flush bacteria -Salivary amylase: CHO digestion -ptyalin -lingual lipase: Lipid digestion -HCL: converts pepsinogen to pepsin with help of pepsin to digest proteins

Name the secretions of the pancreas and describe the process of zymogen secretion and activation

-Trypsin; Trypsinogen activated by Enterokinase -Chymotrypsin; chymotrypsinogen activated by Trypsin -Carboxypeptidase; procarboxypeptidase activated by Trypsin -Lipase; Colipase & procolipase activated by Trypsin -Phospholipase; prophospholipase activated by Trypsin -Amylase & Cholesterolesterase sereted in active form

Describe the controls on gastric acid secretion (cephalic phase, medulla oblongata, parasympathetic, gastric phase, duodenal phase)

-medulla oblongata -parasympathetic -gastric phase -intestinal phase -cephalic phase

Describe the gastric secretions, including cell types

-mucus from mucus cells -intrinsic factor from parietal ells -pepsinogen; packed in zymogen granules -HCl: Parietal cells secretion stimulated by gastrin, histamine & parasympatheic stimulus -gastric lipase: Lipid digestion -gastric pits: secrete gastric glands -chief cells secrete Pepsinogen & Gastric lipase -endocrine cells secrete gastrin

zymogens

1. Enterokinase (brush border enzyme) converts trypsinogen to trypsin. 2.Trypsin converts remaining zymogens to their active form.

How are pancreatic secretions controlled? (role of CCK, secretin, parasympathetic stimulation)

1. Parasympathetic stimulation from the vagus nerve causes the pancreas to release pancreatic juice 2. Secretin is released from duodenum, stimulates pancreas to release pancreatic juice, 3. CCK is released from duodenum, causes pancreas to secrete pancreatic juice

How are pancreatic zymogens activated in the duodenum? (include discussion of enterokinase)

1.Enterokinase (brush border enzyme) converts trypsinogen to trypsin. 2.Trypsin converts remaining zymogens to their active form.

Common bile duct

= Common hepatic duct + cystic duct -Branch together

What is enterohepatic circulation?

A cycle -Liver secretes substances into bile duces to clear them from blood -Some molecules absorbed again in small intestine -Returned to liver

Exocrine pancreas

Acinar glands -acinar cells secrete enzymes -bicarbonate

Lactase

An enzyme in microvilli for Small intestine Disaccharide digestion -Lactose= Glucose + Galactose

Maltase

An enzyme in microvilli for Small intestine Disaccharide digestion -Maltose = 2 glucose

Sucrase

An enzyme in microvilli for Small intestine Disaccharide digestion -Sucrose= glucose + fructose

Where are micelles formed?

At the epithelial cell membrane of villus -This is where fat crosses into the enterocyte via simple diffusion

brush border enzymes

Attached to plasma membrane with active site exposed to lumen; participates in digestion of disaccharides and protein

What are the functions of HCl?

Bacteriostatic Stop CHO digestion Denatures proteins Activates pepsinogen Separates vitamin B12 from protein it is bound to

Name 2 types of secretion of the gallbladder

Bile & gall stones

What are the components of bile

Bile salts Bile pigments (bilirubin) Cholesterol Mucus Lecithin

Describe anatomy of the pancreas and secretions

Both Endocrine and Exocrine

pancreas

Both endocrine and exocrine Glands -Endocrine: Pancreatic islets Produce insulin, glucose, and somatostatin -Exocrine: Acinar glands -Hepatopancreatic ampulla = Common bile duct + Pancreatic duct

How is HCl in chyme buffered when chyme enters the duodenum?

Chime inhibits gastric secretions by -Local reflexes activated by H+ or lipids -Chemoreceptors in the duodenum are stimulated by H+ low pH or lipids. Signals generated by the chemoreceptors are carried by the vagus nerves to the medulla oblongata that inhibit action potentials therefore decreasing gastric secretions. -Secretin and CCK produced by the duodenum decrease gastric secretions

gallbladder connections

Common hepatic duct combines with CYSTIC duct from the gallbladder to form the COMMON BILE DUCT

common hepatic duct

Hepatic ducts that carry Bile from the liver lobes

What is the role of the microvilli?

Increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction. -Holds enzymes

hepatic portal vein

Inferior vein of liver

What are secretions/enzymes of the small intestine?

Mucus Brush border enzymes -Enterokinase -Peptidase -Sucrase -Maltase -Lactase

histamine

Paracrines -causes dilation of capillaries, contraction of smooth muscle, and stimulation of gastric acid secretion, that is released during allergic reactions, and that is formed by decarboxylation of histidine.

What stimulates HCl secretion?

Postganglionic neurons stimulate secretion by parietal and chief cells (HCl and pepsin)

what are gallstones, how can they be serious

Precipitated cholesterol or pigment -Can block cystic ducts

bicarbonate

Secreted from pancreas -Brunner's glands produce it to protect the duodenum from acidic chyme and to adjust the pH so that intestinal enzymes can be active -A component of Bile -A pancreatic secretion -Found in Pancreatic juice

What hormones control secretion of bile; what does secretin do, what does CCK do?

Secretin: hormone produced from duodenum -Stimulates bile secretion -Stimulates pancreas to release pancreatic juice, rich in bicarbonate CCK - Causes pancreas to secrete pancreatic juice, rich in bicarbonate -Stimulates contraction of gall bladder, releasing bile into the duodenum

Describe how HCl is secreted by a parietal cell.

Stimulated by gastrin, histamine, & parasympathetic stimulus

What are the functions and structure of the gallbladder

Store and concentrates Bile from liver -Sac with Mucosa, inner muscularis & outer serosa

sphincter of Oddi

The Sphincter of Oddi is a muscular valve at the opening into the duodenum; it is relaxed by cholecystokinen

common bile duct

The duct that carries bile from the gallbladder and liver to the small intestine (duodenum).

cystic duct

a duct draining bile from the gallbladder; merges with the common hepatic duct to form the common bile duct

gastrin

a hormone that stimulates secretion of gastric juice, and is secreted into the bloodstream by the stomach wall in response to the presence of food.

hepatopancreatic ampulla

common bile duct merges with pancreatic duct -Empties Bile and pancreatic secretions into the duodenum

zymogen

inactive form of enzyme

pepsinogen

packed in zymogen granules

cholecystokinin

produced by duodenum stimulates contraction of gall bladder, releasing bile into the duodenum -decrease gastric secretions in the stomach with help of secretin -released from duodenum, causes pancreas to secrete pancreatic juice, rich in bicarbonate.

Describe the content of pancreatic juice

secreted by the pancreas -Has a variety of enzymes, including trypsinogen, chymotrypsinogen, elastase, carboxypeptidase, pancreatic lipase, nucleases and amylase. -Alkaline in nature due to the high concentration of bicarbonate ions