ingestion of food (breaks it down)

Propulsion of food and waste

secretion of mucous, food, and enzymes

Mechanical Digestion of food particles (prepares food for uptake by the body's cells)

Provides the body with water

Chemical Digestion of Food particles

Absorption of Digested Food

Elimiminaiton of water by defecation.

SNS and PNS

Controlled by centers in the brain and by neural plexuses in the GI system. Enteric nerve circuits regulate motility reflexes, blod flow, absorption, secretion and immune response.

1. Mucosa (inner most layer)

2. Submucosa

3. Muscularis (circular and longitudinal muscle layer)

4. Serosa or adventitia

1. Submucosal plexus (meissner plexus)

2. Myenteric plexus (auerback plexus)

3. Subserosal plexus

(Neural influence control and autonomic nervous system stimuli through the enteric plexus, These enteric nerve circuits regulate motility reflexes, blood flow, absorption, secretion, and immune response)

hormones & neurotransmitters

GASTRIN

What is it's stimulus and what is it's action?

(mucosa of the stomach)

-Stimulus: Partially digested proteins in the stomach

Action: Stimulates gastric glands (HCl and pepsinogen) promotes gastric motility.

hormones & neurotransmitters

Histamine

What is it's stimulus and what is it's action?

(mucosa of the stomach)

Stimulus: Gastrin

Action: stimulates gastric gland secretions (HCl)

hormones & neurotransmitters

GASTRIN RELEASING PEPTIDE

What is it's stimulus and what is it's action?

(mucosa of stomach)

Stimulus: vagus and local nerves of stomach

Action: stimulates gastrin and gastric gland secretions (HCl and pepsinogen)

hormones & neurotransmitters

ACH

What is it's stimulus and what is it's action?

(mucosa of stomach)

Stimulus: vagus and local nerves of the stomach

Action: stimulates gastrin and gastric gland secretions (HCl and persinogen)

hormones & neurotransmitters

Motollin

What is it's stimulus and what is it's action?

(mucosa of the small intestine)

Stimulus: presence of acid and fat and duodenum

Action: increases gastrointestinal motility (move into small intestines)

hormones & neurotransmitters

Secretin

What is it's stimulus and what is it's action?

(mucosa of the small intestine)

Stimulus: presence of chyme ( acid and partially digested proteins and fats) in the duodenum.

Action: inhibits gastrin and gastric action secretion; inhibits gastrointestinal motility; stimulates pancreas to create alkaline fluid; stiumulates liver to secrete bile.

hormones & neurotransmitters

Cholecystokinin

What is it's stimulus and what is it's action?

(mucosa of the small intestine)

Stiumulus: presense of chyme (acid and partially digested proteins and fats) in the duodenum.

Action: inhibits gastrin, decreases gastric motility, delays gastric emptying, stimulates pancrease to secrete alkaline fluid, stimulates the gall bladder to eject bile.

hormones & neurotransmitters

Gastric Inhibtitory Peptide

What is it's stimulus and what is it's action?

(mucosa of the small intestine)

Stimulus: fat and glucose in the small intestine

Action: inhibits gastrin secretion and gastric emptying; stimulates insulin release.

*Reservoir for chewing and mixing food with saliva.

TASTE BUDS: salty, sour, bitter and sweet.

Tastes and food odors (olfactory nerves) initiate salvation in the mouth and secretion of gastric juice in the stomach

Submandibular, Sublingual and Parotid.

-Water with mucus, sodium, bicarbonate, chloride, potassium, and salivary alpha-amylase (initial carbohydrate digestion)

-Controlled by parasympathetic and sympathetic fibers (not by hormones).

      1. Cholinergic (ACh): stimulates salvilary gland secretion.

      2. Adrenergic (beta adrenergic): stimulates salvilary secretions.

-Bicarb concentration pH 7.4 neutralizes acids and prevents tooth decay

-Composition of saliva depends on rate of secretion.

-It conducts swallowed food to the stomach by peristalsis.

-Peristalsis is coordinated by contraction and relaxation of the outer longirudinal and inner circular layers of muscle; stimulated by stretch (change in wall tension); the greater the tension, the greater the intensity of esophageal contraction (intense contractions can cause pain similar to heartburn or angina)

Upper Third: skeletal muscle innervated by motor neurons.

Middle Third: mix of skeletal and smooth muscle.

Lower Third: smooth muscle innervated by cholinergic fibers from vagus.

-Upper prevents air into esophagus during respiration

-Lower: prevents regurgitation from stomach to esophagus.

(Muscle tone of lower sphincter changes with neural and hormonal stimulation as well as swallowing. vagal input and gastrin increase sphincter tone; swallowing relaxes sphincter tone.)

it is a complex event mediated primarily by the swallowing center located in the brainstem.

-The swallowing center and respiratory center provide the coordination innervation.

-Superior constrictor muscle of the pharynx contracts, prevents movement of food into the nasopharynx.

-Respiration inhibited and epiglottis slides downward to prevent bolus from entering the larynx or the trachea.

- Movement of the tongue and pharngeal constrictors propel the food into the esophagus in a series of coordinated events taking 1 or 2 seconds.

Perstalsis with segmental waves that travel down the esophagus.

a hollow muscular organ that stores food, secretes digestive juices, mixes food with the juices and propels partially digested food (chyme) to the small intestine.

1. Cardiac orifice

2. Fundus

3. Body

4. Pylorus

5. Pyloric Sphincter

1. Outer longitudinal

2. Middle circular.

3. Inner oblique

In gastric motility what does swallowing cause the fundus to do?

What does gastric motility increase with?

****

The initiation of peristaltic waves:

• Rate of peristalsis mediated by pacemaker cells that initiate wave of depolarization.
• Gastrin (stomach mucosa) and motilin (intestinal mucosa) and the vagus (PNS) stimulates peristalsis.
• Rate of gastric emptying: controlled to adjust the duodenums ability to neutralize acids, digestive fat, facilitate formation of isoomotic enviroment. *
• Larger volumes of food increase peristalsis and rate of emptying
• Fats and hypertonic/hypotonic contents delat gastric emptying; fats in the SI stiumulate cholecystokinin release which delays gastric emptying.

-The stomach secretes large volumes of gastric juices: mucus, acid, enzymes, hormones, Intrinsic factor (require for intestinal absorption of b12) and gastroferrin (required for intestinal absorption of iron)

1. Parietal cells: hydrochloric acid and intrinsic factor

2. Chief Cells: Pepsinogen (converts persinogen to pepsin)

3. G-cells: gastrin

4. Enterochtomaffin- like cells ( produce Histamine)

They are lower in the gastric juices then in the plasma.

1. Cephalic: Vagus stimulates Ach and GRP (gastric releasing peptide)--> Ach stiumlates parietal and chief cells--> GRP stimulates G cells.

2. Gastric: Two stimuli: distension presence of digested protein. Caffeine stimulates acid secretion and proteins buffer acid.

3. Intestinal: Entry into the intestines slows gastric secretory response--> GIP decreases gastric motility and secretion of acid when chyme enters duodenum--> Acidic chyme with presence of digested protein stimulates cholecystokinin which inhibits gastric acid secretion.

-dissolves food fibers

-bactericide

-Converts pepsinogen to pepsin.

-Acid is formed from parietal cells primarialy through the hydrolysis of water.

-At a high rate of gastric secretion, bicarbonate moves into the plasma, producing an "alkaline tide" in the venous blood, which also may result in more alkaline urine.

-Acid secretion by parietal cells is stimulated by Ach (neurotransmitter), gastrin (hormone) and histamine (a biochemical mediator).

-Histamine receptors in the gastric mucosa are the H2 receptors.

-GIP (gastric inhibitory peptide) and secretin (from the intestinal mucosa) inhibit acid secretion.

-Proteolytic enzyme that breaks down polypeptides (proteins).

-Pepsinogen converted to pepsin at pH of 2

-ACh is the strongest stimulus for pepsin secretion

-Alkaline environment of duodenum inactivates pepsin.

-Protects gastric mucosa from acid and pepsin.

-Mucous and tight junction protect the gastric mucosa.

-** Prostaglandins and Nitric Oxide protect hte mucosal barrier by stimulating the secretion of mucus and bicarbonate and by inhibiting the secretion of acid.

-ASA and NSAIDs, H.Pylori, ethanol can result in break of protective barrier; inhibit protaglandins; breaks cause inflammation and ulceration.

1. Duodenum

2. Jejunum

3. Illeum and illeocal valve. (right before the colon)

-it is the serous membrane surrounding the organs of the abdomen and pelvic cavity.

1. The visceral peritoneum lies over the organs

2. The parietal perotoneum lines the wall of the abdominal cavity.

3. The space between 1. & 2. is called the peritoneal cavity.

primarily from the gastroduodenal artery.

-the mysenteric plexus (auerbach plexus) and submucosal plexus (Meisnner plexus).

-ABSORPTION hrough the "Villi" which cover the mucosal folds and are the functional units of the intestine.

- Also SECRETES some enzymes necessary for digestion and absorption of nutrients.

-**The villus is composed of columnar cells (enterocytes) that do the ABSORPTION and Goblet cells that do the SECRETING of mucous. in the mucosal epithelium.**

Microvilli.

Brush border.

It is a connective tissue layer of the mucous membrane, lies beneath the epithelial cells of the villi and contains lymphocytes, plasma cells, which produce immunoglobulins and macrophages.

this is contained within the villus and is important in the absorption and transport of fat molecules. Contents of the lacteals flow to regional nodes and channels that eventually drain into the thoracic duct.

aciton of pancreatic enzymes, intestinal brush border enzymes and bile emulsifies fats.

Carbohydrates

What do salvilary enzymes do?

They break down starches to oligosaccharides

Carbohydrates

Carbohydrates

What do pancreatic amylase do to oligossacharides?

Carbohydrate Absorption and Digestion

What do brush border enzymes do to Lactose, Maltose and sucrose?

They become galactose, glucose and fructose (monosaccarides). Which are then absorbed by capillaries in the villi and transported to the liver by the portal vein. Active transport is used to bring them from the lumen to the blood (co transported with Na)

Protein Absorption and Digestion.

Where is does a major portion of this take place?

Protein absorption and digestion.

Proteins are brocken into Proteases and peptones by?

Protein Absorption and Digestion

What changes proteases and peptones into Small polypeptides and dipeptides?

Proteins Absorption and Digestion

What is needed to change small polypepties and dipepides into Amino Acids?

Brush Border enzymes.

(Absorbed by the capillaries in the villi and transported to the liver by hepatic portal vein.) ( Active transport of amino acids is co-transported with Na)

Fat Digestion and Absorption

What changes 'unemulsified fats' into 'Monoglycerides and fatty acids' and 'gylcerol and fatty acids'?

Fat Digestion and Absorption

How do Monoglycerides and Fatty Acids leave the small intestine?

They are absorbed by lacteals in the villi and transported to the liver in the systemic circulation, which receives lymphatic flow from the thoracic duct or via the hepatic portal vein.

Fat digestion and absorption

How do Glycerol and short chain fatty acids leave the small intestine?

Clycerol and short chain fatty acids absorbed by capillaries in the villi and transported to the liver by the portal vein.

-No, Na absorption is directly coupled to absorption of organic solutes (glucose, amino acids, water soluble vitamins)

-Na actively transported into intestinal cells from lumen in exchange for H+;  Cl is actively transported into intestinal cells from lumen in exhange for bicarb (to maintain electroneutrality)

- Na/K pump on basolateral membrane (between epthial cell and blood)

-Consists of localized rhythmic contraction of circular smooth muscles and occurs more frequently than peristalsis. The contraction waves occur at different rates in different parts of the small intestine in segments of 1-4 cm.

-It is regulated intrinsincally by the frequency of the basic electrial rhythm of myenteric plexus

-it divides, mixes and propels chyme.

-It involves short segments of longitudinal smooth muscle and propels chyme

-Wave of contraction moves slowly to enhance time for digestions and absorption (strech and shorten, moves slower than Segmentation)

It inhibits intestinal motility when one part of the intestine is over distended.

 it is activated by an increase in gastric motility and secretion, stimulates an increase in ileal motility and relaxation of the ilocecal sphincter. This empties the ileum and prepares it to receive more chyme.

Where is this located and what does it do?

ILEOCECAL VALVE (SPHINCTER)

It marks the junction between the terminal ileum and the large intestine. This valve is intrinsically regulated and is normally closed. The arrival od peristaltic waves from the last few centimeters of the ileum causes the ileocecal valve to open, allowing a small amount of chyme to pass through. Distention of the upper large intestine causes the sphincter to constrict, preventing further distention or retrograde flow of intestinal contents.

In the cecum and the colon the longitudinal muscle layer consists of three longitudinal bands called ________. They are shorter than the colon and give it a "gathered" appearance.

The mucosal surface of the colon; the folds

It initiates propulsion in the entire colon, ususally during or after eating, when chyme enters from the ileum. The gastrocolic reflex causes the fecal mass to pass rapidly into the sigmoid colon and rectum, stimulating defectation.

The movement of feces into the sigmoid colon and rectum stimulates this reflex. The rectal wall stretches and the tonically constricted internal anal sphincter (smooth muscle with the autonomic nervous system control) relaxes creating the urge to defecate.

Bile: an alkaline, bitter-tasting, yellowish-green fluid that containes bile salts (conjugated bile acids), cholesterol, bilirubin (a pigment), electrolytes, and water

It receives nutrients absorbed by the small intestine and metabolizes or synthesizes into forms that can be absorbed by the body's cells; releases nutrients into the blood stream and stores them.

It produces enzymes needed for complete digestion of carbohydrates, proteins and fats. It produces alkaline fluid that neutralizes chyme.

They all secrete substances necessary for digestion of chyme which is delilvered to the duodenum through ducts.

The Glisson Capsule which contains blood vessels, lymphatics and nerves.

Where does the liver receive blood from?

1. Hepatic Artery: receives blood from the abdominal aorta

2. Hepatic Portal Vein: receives blood from mesenteric veins and splenic veins; carries 70% of blood supply to liver, rich in nutrients.

3. Hepatic Vein: empties into the vena cava.

-They are small capillaries

-They receive blood from the hepatic artery and portal vein and drain into the central vein; with permeable epithium allowing substances to move into hepatocytes.

drains venous blood from hepatocytes and empties into the vena cava.

They take bile from the hepatocytes and drains it into the canalculi, emptying into bile ducts, common hepatic duct, common bile duct.

Common bile duct and pancreatic duct meet at ampulla of Vater and then empties into duedenum via sphincter of Oddi

The sinusoids are also lined with phagocytic cells known as these. They are part of the mononuclear phagocyte system and are the largest population of tissue of macrophages. They are bacteriocidal and are important in bilirubin production and lipid metabolism.

They contain retinoid (Vitamin A), are contractile in a liver injury, regulate sinusoidal blood flow, and may proliferate into myofibroblasts.

They are natural killer cells found in the sinusoidal lumen; they produce interferon-y and are important in tumor defense.

What are the functions of the liver?

***

-Bile production and secretion

- Metabolism of bilirubin.

- Bacterial and foreign particle removal (Kupffer and Pit cells)

- Vascular and hematologic functions

- Metabolism of nutrients

- Metabolic detoxification (HUGE)

-Storage of minerals and vitamins.

It is a byproduct of destruction of aged red blood cells. It gives bile a greenish black color and produces the yellow tinge of jaundice. Aged red blood cells are taken up and destroyed by macrophages of the mononuclear phagocyte system primarily in the spleen and the liver. (In the liver these macrophages are Kupffer cells)

In the plasma billirubin binds to albumin and is known as ______. or free billirubin. which is lipid soluble. Elevated levels may protect against cancer and cardiovascular disease.

Within the hepatocytes unconjugated billirubin joins with glucuronic acid and it forms _______ which is water soluble. Conjugation transforms bilirubin from lipid soluble substance that can cross biologic membranes to a water soluble substance

What are the vascular and hematologic functions of the liver?

What does it synthesize?

-Can store large volumes of blood.

-Sythesizes, prothombin, fibrinogen, factors I, II, and X, all necessary for clotting.

-Vitamin K is essential productin for clotting factors; Vit K absorption (fat soluble) depends on adequate bile production.

-Receives all the venous blood from the gut and the pancreas; important to have Kupffer cells to destroy bacteria and prevent infections.

LIVER FUNCTIONS

Metabolism of Carbohydrates is important why?

-Important in stability of blood glucose

- Releases in hypoglycemia.

-Takes in hyperglycemia

-Stores as glycogen

-Undergoes glucogeonesis (amino acids)

LIVER FUNCTIONS

Metabolism of Fats is important why?

-Synthesize from proteins and carbs in liver hydrolyzed to free fatty acids and glycerol to produce metabolic energy (ATP) OR released as lipoproteins; also synthesizes phospholipids and cholesterol

-important for production of bile salts, steroid hormones, components of plasma membranes

LIVER FUNCTIONS

Metabolism of Proteins is important why?

-*Produciton of plasma proteins (via amino acids obtained via digestion) including albumin and globulins (except for gamma globulins produced in lymph nodes and tissues)

- synthesizes essential and not essential amino acids and serum enzymes

-Converts amino acids to carbohydrates by deamination of ammonia

-Converts ammonia to urea for excretion

-can convert ketoacids to fatty acid for fat sythesis and storage or use in Kreb cycle for ATP energy.

-A sac-like organ; inferior surface of the liver.

-Stores and concentrate bile between meals.

-Holds about 90 ml of bile.

-From liver to right and left hepatic duct to common hepatic duct to common bile duct to duodenum via Sphincter of Oddi

-When Sphincter closed it moves via cystic duct to be stored and concentrated in the gall bladder.

it absorbs water and elctrolytes and concentrates the bile

-In the cephalic and gastric phases, sphincter of Oddi relaxes, gall bladder contracts and bile flows into the duodenum.

- Contraction is controlled via the vagus (cholinergic) and cholectystokinin (secreted via duodenum in response to presense of fat)

-Relaxation is controlled by the sympathetic nerve stimulation

-Composed of acini and networks of ducts.

-Secrete enzymes and alkaline fluids to assist in digestion.

-Pancreatic duct empties into the common bile duct at the Ampulla of Vater and then into the duodenum (with bile) via sphincter of Oddi

-Parasympathetic fibers of the vagus stimulate enzymatic and hormonal secretion

-Sympathetic fibers cause vasoconstriction of blood vessels and inhibit secretion.

-Cholectystokinin and ACh stimulate enzyme secretion.

Exocrine Pancreas

Secretions

-Potassium, Sodium, Bicarbonate, Magnesium, Calcium, and chloride

-Isotonic

-Alkaline which neutralizes acidity

-Bicarb excretion increases with flow rate

-Eating stimulates flow

Exocrine Pancreas

Enzymes

-Pancreatic enzymes hydrolyze proteins (proteases), fats (lipases), and carbs (amylase)

- Trypsinogen, chymotrypsinogen, and procarboxypeptidase

-Secreted in inactive form

-Activated in dueodenum by enterokinase (secreted by duodenal mucosa)

-Trypsin inhibitor to prevent activation while in pancreas.