1. ANAPHY (GI) MS

7 to 7.9 meters (23 to 26 feet)

What is the approximate length of the GI tract?

Mouth → Esophagus → Stomach → Small intestines → Large intestines → Rectum → Anus

List the correct order of the GI tract.

Esophagus

• is located at the mediastinum

• This collapsible tube, about 25 cm (10 inches) in length

• becomes distended when food passes through it.

• It passes through the diaphragm at an opening called DIAPHRAGMATIC HIATUS

DIAPHRAGMATIC HIATUS

the one that controls the entrance of foods and other substances in the esophagus to the stomach

Stomach

• 1,500 mL capacity

• Gastroesophageal junction is the inlet to the stomach

• 4 anatomic regions

  • Cardia

  • Fundus

  • Body

  • Pylorus

• Cardia

• Fundus

• Body

• Pylorus

• 4 anatomic regions of stomach

Small intestine

• Longest segment of the GI tract accounts for about two-thirds of the total length.

• It folds back and forth

• Approximately 7,000 cm of surface area for secretion and absorption, the process by which nutrients enter the bloodstream through the intestinal walls.

• Divided into three anatomic parts:

  • The Duodenum (proximal)

  • The Jejunum (middle)

  • The Ileum (distal)

• The Duodenum (proximal)

• The Jejunum (middle)

• The Ileum (distal)

three anatomic parts of small intestine

Common Bile Duct

allows for the passage of both bile and pancreatic secretions empties into the duodenum at the ampulla of Vater.

Ileocecal Valve

• Controls the passage of intestinal contents into the large intestine.

• Prevents reflux of bacteria from the large intestine into the small intestine

Vermiform Appendix

• A narrow, worm-like tubular structure attached to the cecum

• vestigial organ

• Ascending segment (right side of the abdomen),

• Transverse Segment (extends from right to left in the upper abdomen)

• Descending Segment (left side of the abdomen)

Large intestine consists of

• sigmoid colon

• rectum - continuous with the anus.

Terminal portion (large intestine) consists

Arteries originating along the entire length of the thoracic and abdominal aorta

Where does the GI tract receive its arterial blood supply from?

• Superior Mesenteric

• Inferior Mesenteric

• Gastric Artery

• Splenic

• Cystic Veins

This portal venous system is composed of five large veins:

Which artery supplies the stomach?

Gastric artery

Which arteries supply the intestines?

Mesenteric arteries

Blood

is drained from organs by veins that merge with others in the abdomen to form a large vessel called the PORTAL VEIN

sympathetic and parasympathetic

portions of the autonomic nervous system innervate the GI tract.

About 20%

Approximately how much of the total cardiac output goes to the GI tract?

increases significantly

What happens to blood flow in the GI tract after eating?

Sympathetic Nerve

Inhibitory effect on the GI tract decreasing gastric secretion and motility → causing the sphincters and blood vessels to constrict.

Parasympathetic Nerve stimulation

• causes peristalsis and increases secretory activities.

• Sphincters relax under the influence of parasympathetic stimulation.

• upper esophagus

• external anal sphincter

Under voluntary control

1. Breakdown of food particles into the molecular form for digestion

2. Absorption into the bloodstream of small nutrient molecules produced by digestion.

3. Elimination of undigested unabsorbed foodstuffs and other waste products from the body.

Major functions of the GI tract include:

Chewing

The process of digestion begins with the act of ____ , in which food is broken down into small particles that can be swallowed and mixed with digestive enzymes.

eating, sight, smell, or taste of food

can cause reflex salivation.

• Parotid glands

• Submaxillary glands

• sublingual glands

Saliva is secreted from three pairs of glands:

1.5L

Approximately ___ of saliva is secreted daily.

saliva

first secretion that comes in contact with food.

ptyalin; salivary amylase

Saliva contains the enzymes _____ or _____ which begins the digestion of starches.

medulla oblongata

swallowing center

epiglottis

As food is swallowed, the _____ moves to cover the tracheal opening and prevent aspiration of food into the lungs.

swallowing

propels the bolus of food into the upper esophagus, thus ends as a reflex action

Stomach

• stores and mixes food with secretions

• secretes a highly acidic fluid in response to the presence or anticipated ingestion of food.

Hydrochloric acid (HCL)

• can total 2.4 L/day

• can have a pH as low as 1

• derives its acidity from secreted by the glands of the stomach.

1. To break down food into more absorbable components

2. To aid in the destruction of most ingested bacteria

Function of gastric secretion is two-fold:

2.4L/Day

stomach can produce _____ of gastric secretions

Pepsin

also contain the enzyme ____, which is important for initiating protein digestion.

• Ptyalin (Salivary Amylase)

• Amylase

• Maltase

• Sucrase

• Lactase

Enzymes that Digest Carbohydrates

Salivary glands

What is the source of Ptyalin/ salivary amylase (diastase)?

Starch → dextrin, maltose, glucose

What is the digestive action of Ptyalin/salivary amylase (diastase)?

Pancreas and intestinal mucosa

What are the sources of amylase?

Starch → dextrin, maltose, glucose

What is the digestive action of amylase?

Intestinal mucosa

What is the source of maltase?

Maltose → glucose

What is the digestive action of maltase?

Intestinal mucosa

What is the source of sucrase?

Sucrose → glucose, fructose

What is the digestive action of sucrase?

Amylase, maltase, sucrase, lactase

Which carbohydrate-digesting enzymes are produced in the intestinal mucosa?

Ptyalin/Salivary amylase (diastase)

Which enzyme begins carbohydrate digestion in the mouth?

break down proteins into amino acids

What is the general function of protein-digesting enzymes?

Gastric mucosa

What is the source of pepsin?

Protein → polypeptides

What is the digestive action of pepsin?

Pancreas

What is the source of trypsin?

Proteins and polypeptides → polypeptides, dipeptides, amino acids

digestive action of trypsin?

Intestinal mucosa

source of aminopeptidase?

Polypeptides → dipeptides, amino acids

digestive action of aminopeptidase?

Intestinal mucosa

source of dipeptidase?

Dipeptides → amino acids

digestive action of dipeptidase?

Gastric mucosa

source of hydrochloric acid (HCl)?

Protein → polypeptides and amino acids

digestive action of hydrochloric acid (HCl)?

Which enzymes are produced in the intestinal mucosa for protein digestion?

Aminopeptidase and dipeptidase

• pepsin

• trypsin

• Aminopeptidase

• Dipeptidase

• Hydrochloric acid

enzymes /secretions that digest protein

break down triglycerides into simpler components

What is the function of fat-digesting enzymes and secretions?

Pharyngeal mucosa

What is the source of pharyngeal lipase?

Triglycerides → fatty acids, diglycerides, monoglycerides

What is the digestive action of pharyngeal lipase?

Gastric mucosa

What is the source of steapsin?

Triglycerides → fatty acids, diglycerides, monoglycerides

digestive action of steapsin?

Pancreas

source of pancreatic lipase?

Triglycerides → fatty acids, diglycerides, monoglycerides

digestive action of pancreatic lipase?

Liver and gallbladder

source of bile?

Emulsification of fats

digestive action of bile?

propel stomach contents toward the pylorus

What is the role of peristaltic contractions in the stomach?

They are too big, so they are churned back into the body of the stomach

Why can’t large food particles pass through the pyloric sphincter?

Chyme

What is the term for food mixed with gastric secretions?

30 minutes to several hours, depending on particle size, meal composition, and other factors

How long can food remain in the stomach?

Hormones, neuroregulators, and local regulators in gastric secretions

What factors control the rate of gastric secretions and influence gastric motility?

• Acetylcholine

• norepinephrine

neuroregulators

Sight, smell, chewing food, stomach distention

stimulation for production of acetylcholine

Stress, other various stimuli

stimulation for production of norepinephrine

• Gastric glands,

• other secretory glands,

• gastric and intestinal muscle

target tissue of acetylcholine

• Secretory glands,

• gastric and intestinal muscle

target tissue of epinephrine

↑ Gastric Acid

effects on secretions of acetylcholine

Generally inhibitory

effects on secretions of norepinephrine

• Generally Increased;

• decreased sphincter tone.

effect on motility of acetylcholine

• Generally decreased;

• increased sphincter tone

effect on motility of norepinephrine

• gastrin

• cholecystokinin

• secretin

hormonal regulators

stomach distention with food

Stimulation for production of gastrin

Fat in duodenum

Stimulation for production of cholecystokinin

pH of chyme in duodenum below 4-5

stimulation for production of secretin

gastric glands

target tissue of gastrin

Gallbladder Pancreas Stomach

target tissue of gastrin cholecystokinin

gastric glands

target tissue of gastrin secretin

↑ Secretion of gastric juice, which is rich in HCL

effect on secretion of gastrin

• Release of bile into the duodenum

• ↑ Production of enzyme-rich pancreatic secretions

• Inhibits gastric secretion somewhat

effect on secretion of cholecystokinin

• Inhibits gastric secretion somewhat

• Increased production of bicarbonate-rich pancreatic juice

effect on secretion of secretin

• Increased motility of stomach;

• decreased time required for gastric emptying

• Relaxation of the ileocecal sphincter

• Excitation of colon

• Constriction of the gastroesophageal sphincter

effect on motility of gastrin

Inhibits stomach contractions

effect on motility of gastrin