ANATOMY: DIGESTIVE SYSTEM Flashcards
Identify the organs of the digestive system.
2 components
- Gastrointestinal (GI) tract
• Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine
- Associated organs
• Tongue • Teeth • Salivary glands • Pancreas • Liver • Gallbladder
Describe the basic processes performed by the digestive system.
6 processes
- Ingestion
- Secretion
- Mixing & propulsion
- Digestion
- Absorption
- Defecation
Name and describe the abdominopelvic regions.
See diagram
Describe the peritoneum and the peritoneal folds.
The perteoneum is the serous membrane that forms the lining of the abdominal cavity
- Largest serous membrane in the body
- Parietal peritoneum
– Lines wall of abdominopelvic cavity
• Visceral peritoneum
– Covers organs in the cavity
– Serosa
Five major peritoneal folds
- Greater omentum
- Falciform ligament
- Lesser omentum
- Mesentery
- Mesocolon
– Transverse
– Sigmoid
Discuss peritonitis.
Peritonitis is an inflammation of the peritoneum, the thin tissue that lines the inner wall of the abdomen and covers most of the abdominal organs. Peritonitis may be localized or generalized, and may result from infection (often due to rupture of a hollow abdominal organ as may occur in abdominal trauma or inflamed appendix) or from a non-infectious process.
Describe the layers that form the wall of gastrointestinal tract.
1. Mucosa
- Epithelium
- Lamina propria
- Loose connective tissue
- Blood & lymph vessels
- Mucosal glands
- Gut-associated lymphatic tissue (GALT)
- Muscularis mucosae
• Usually 2 layers
– Inner circular
– Outer longitudinal
- Contraction produces movement of the mucosa
- Boundary between mucosa and submucosa
- 3 principal functions
- Protection - Barrier between lumen and tissues of the body
- Absorption - Movement of digested nutrients, water & electrolytes into blood and lymph vessels
- Secretion - Mucous, digestive enzymes, hormones & antibodies
2. Submucosa
- Dense irregular connective tissue
- Larger blood & lymph vessels
- Occasional glands
– Esophageal glands proper
– Duodenum (Brunner’s) glands
• Submucosal plexus (of Meissner)
– Part of the enteric nervous system
- Parasympathetic ganglia and postganglionic fibers
- Innervate muscularis mucosae
3. Muscularis externa
• 2 concentric & thick layers
- Inner circular
- Contraction compresses and mixes contents
- Forms sphincters at specific locations of the GI tract
– Upper esophageal sphincter
– Pyloric sphincter
– Ileocecal valve
– Internal anal sphincter
- Outer longitudinal
- Contraction propels contents by shortening the tube
- Thickened in the large intestine
– Bands called taenia coli
• Peristalsis
– Slow, rhythmic contraction of muscle layers
– Controlled by enteric nervous system
• Myenteric plexus (of Auerbach)
– Part of the enteric nervous system
– Parasympathetic ganglia and postganglionic fibers
– Located between the 2 muscle layers
– Innervate muscularis externa
- Serosa
– Serous membrane
- Simple squamous epithelium
– Mesothelium
- Small amount of underlying connective tissue
– Continuous with mesentery and lining of abdominal cavity
Describe the two nerve plexuses of the gastrointestinal tract.
• Submucosal plexus (of Meissner)
– Part of the enteric nervous system
–Parasympathetic ganglia and postganglionic fibers
– Innervate muscularis mucosae
• Myenteric plexus (of Auerbach)
– Part of the enteric nervous system
– Parasympathetic ganglia and postganglionic fibers
– Located between the 2 muscle layers
– Innervate muscularis externa
Describe the location and gross anatomy of the esophagus.
See diagram
Peristalsis is a series of wave-like muscle contractions that moves food to different processing stations in the digestive tract. The process of peristalsis begins in the esophagus when a bolus of food is swallowed.
Describe the histology and layers that form the wall of esophagus.
Mucosa
- Epithelium
• Nonkeratinized stratified squamous epithelium
- Lamina propria
- Loose connective tissue
- Diffuse lymphatic tissue
- Esophageal cardiac glands
– Mucous glands
» Neutral secretion
– Frequently present at initial region
– Present in terminal region
» Protects against regurgitatedstomach contents
» Excessive reflux results inpyrosis (heartburn)
- May progress to gastroesophageal reflux disease (GERD)
- Barrett’s esophagus
- Muscularis mucosae
- Primarily longitudinal smooth muscle
- Begins near level of cricoid cartilage
Submucosa
– Dense irregular connective tissue
– Diffuse lymphatic tissue and nodules
– Esophageal glands proper
• Mucous glands
– Slightly acidic secretion
– Lubricate lumen
- Scattered along the length
- Frequently more concentrated in upper half
- Excretory duct
– Meissner’s plexus
- Nerve fibers
- Ganglion cells
- Primarily supplies muscularis muscosae
Muscularis externa
– 2 muscle layers
- Inner circular
- Outer longitudinal
- Upper 1/3 striated muscle
- Middle 1/3 striated muscle & smooth muscle
- Lower 1/3 smooth muscle
– Myenteric (Auerbach’s) plexus
- Between inner and outer muscle layers
- Nerve fibers and ganglion cells
- Innervates muscularis externa
Adventitia
Explain the functions of the esophagus in the digestive process.
Functions
– Transport food to stomach
• Peristalsis is a series of wave-like muscle contractions that moves food to different processing stations in the digestive tract. The process of peristalsis begins in the esophagus when a bolus of food is swallowed.
– Secrete mucus
Discuss gastroesophageal reflux disease (GERD) and Barrett’s esophagus.
GERD occurs when stomach acid or, occasionally, stomach content, flows back into your food pipe (esophagus). The backwash (reflux) irritates the lining of your esophagus and causes GERD.
- Lower esophagus undergoes metaplasia (a)
- Gastroesophageal reflux through the lower esophageal sphincter
- Higher risk of developing dysplasia
- Risk of developing adenocarcinoma
Barrett’s esophagus is most often diagnosed in people who have long-term gastroesophageal reflux disease (GERD) — a chronic regurgitation of acid from the stomach into the lower esophagus.
Describe the function, location, and gross anatomy of the stomach.
Describe the histology and layers that form the wall of stomach.
1. Mucosa
– Prominent mucosal & submucosal folds (rugae)
– Gastric pits
– Gastric glands
- Extend from muscularis mucosae
- Empty into gastric pits
– 3 components
- Epithelium
– Simple columnar
» Surface mucous cells
- Lamina propria
– Surrounds gastric pits & glands
- Muscularis mucosa
– 2 thin layers
» Inner circular
» Outer longitudinal
– Some regions may have a 3rd circular layer
2. Submucosa
– Dense connective tissue
– Submucosal (Meissner’s) plexus
• Innervates blood vessels & muscularis mucosae
3. Muscularis externa
- Inner oblique
- Middle circular
- Outer longitudinal
– Myenteric (Auerbach’s) plexus
4. Serosa
What are 4 functional cell types of the gastric fundic glands?
1. Neck mucous cells
– Renewed every 5-6 days
2. Parietal cells (oxyntic)
– Renewed every 150-200 days
3. Chief cells (peptic)
– Renewed every 60-90 days
– Renewed every 60-90 days
Where are stem cells of the gastric (funic) glands located?
- Located in the isthmus & neck
- Give rise to the other cell types
How much and what are the compenents of gastric juice by the gastric glands?
Describe Parietal (Oxyntic) Cells.
Describe Chief (Peptic) Cells.
Describe Enteroendocrine Cells
Discuss peptic ulcer disease (PUD)
Peptic ulcer disease (PUD), also known as a peptic ulcer or stomach ulcer, is a break in the lining of the stomach, first part of the small intestine, or occasionally the lower esophagus.[1][2] An ulcer in the stomach is known as a gastric ulcer while that in the first part of the intestines is known as a duodenal ulcer.
Describe the function, location, and gross anatomy of the small intestine.
Describe the histology and layers that form the wall of small intestine.
Name 3 types of tissues/cell specializations found in the small intestines.
- Plicae circularis (circular folds)
– Valves of Kerckring
– Permanent transverse folds
• Contain core of submucosa
– Most numerous in distal duodenum and jejunum
– Reduced in size and frequency in ileum
- Villi
– Fingerlike & leaflike mucosal projections
• 0.5 - 1.5 mm
– Completely cover surface
– Lamina propria contains central lacteals
• Blind-ended lymphatic capillary
- Microvilli
– Major increase in luminal surface area
– Each cell possesses several thousand microvilli (Mv)
– Give the cells a striated border (SB) in the light microscope
• Brush border
– Glycocalyx (G)
– Terminal web (TW)
Describe the duodenum.
Describe the jejunum.
Describe the ileum.
Describe the intestinal glands including the cells of the small intestine.
Describe Enterocytes
Located in the small intestines
Descrie Goblet Cells
Located in the small intestines
Describe Enteroendocrine Cells
Located in the small intestines.
Describe Paneth Cells
Describe the function, location and gross anatomy of the large intestine.
Describe the histology and layers that form the wall of large intestine.
Describe the Mucosa of the large intestines.
Describe Muscularis Externa of the Large Intestines
Describe Vermiform Appendix of the Large Intestines
Describe Rectum & Anal Canal
Discuss appendicitis and Hirschsprung disease.
Appendicitis
– Inflammation
– Results from blockage of opening to the cecum
• Scarring, thick mucous or stool
What are 3 main functions of the mucosa in the GI track?
• 3 principal functions
- Protection - Barrier between lumen and tissues of the body
- Absorption - Movement of digested nutrients, water & electrolytes into blood and lymph vessels
- Secretion - Mucous, digestive enzymes, hormones & antibodies
Explain the 3 layers of the mucosa in the esophagus.
Mucosa
- Epithelium
• Nonkeratinized stratified squamous epithelium
- Lamina propria
- Loose connective tissue
- Diffuse lymphatic tissue
- Esophageal cardiac glands
– Mucous glands
» Neutral secretion
– Frequently present at initial region
– Present in terminal region
» Protects against regurgitated stomach contents
» Excessive reflux results inpyrosis (heartburn)
- May progress to gastroesophageal reflux disease (GERD)
- Barrett’s esophagus
- Muscularis mucosae
- Primarily longitudinal smooth muscle
- Begins near level of cricoid cartilage
Explain the submucosa in the esophagus.
Submucosa
– Dense irregular connective tissue
– Diffuse lymphatic tissue and nodules
– Esophageal glands proper
• Mucous glands
– Slightly acidic secretion
– Lubricate lumen
- Scattered along the length
- Frequently more concentrated in upper half
- Excretory duct
- Nerve fibers
- Ganglion cells
- Primarily supplies muscularis muscosae
What are the functions of the liver
Exocrine - bile secretion (~1000ml/day)
Describe the flow of blood (going into liver to the heart)
- Oxygenated blood from hepatic artery & nutrient-rich blood, deoxgynated blood from hepatic portal vein
- Liver sinusoids
- Central vein
- hepatic vein
- inferior vena cava
- right atrium of heart
What does the portal triad consists of?
bile duct
banch of hepatic artery
branch of hepatic portal vein
Where is the gallbladder?
posterior surface of the liver, consist of 3 regions (Fundus, body & neck)
What is the function of the gallbladder?
store and concentrate bile
Describe the exocrine component of the pancreas.
99% makes pancreatic juice that consists of water, salts, sodium bicarbonate and enzymes
Enzymes help digest carbohydrates, proteins, lipids and nucleic acids
makes ~1L a day to 1.5 L a day
Describe the endocrine component of the pancreas.
1% Composed of Isletes of Langerhans (are tiny clusters of cells scattered throughout the pancreas)
theses cells include:
alpha cells - secrete glucagon
beta cells - secrete insulin
delta & F cells
What is the main function of the pancreas?
The pancreas has two main functions: an exocrine function that helps in digestion and an endocrine function that regulates blood sugar.
The pancreas is also a digestive organ, secreting pancreatic juice containing digestive enzymes that assist digestion and absorption of nutrients in the small intestine.
What are agonists of parietal cell HCl secretion?
An agonist is a chemical that binds to a receptor and activates the receptor to produce a biological response.
H+ secretion by parietal cells is increased by
Acetylcholine (neurocrine)
Gastrin (endocrine)
Histamine (paracrine)
Gastrin-releasing peptide (GRP), which acts to increase gastrin secretion
Histamine, produced by enterochromaffin-like (ECL) cells in the mucosa, is released when stimulated by gastrin. Histamine binds to H2 receptors on parietal cells and increase cAMP via the Gs pathway. The H2 receptors can be targeted via histamine blockers (ranitidine, famotidine, cimetidine).
Gastrin, produced by G cells, primarily acts on potentiating histamine release by ECL cells. In addition, it reaches parietal cells through the bloodstream to increase intracellular IP3 and Ca2+ via the Gq pathway. Gastrin is stimulated by vagus nerve release of gastrin releasing peptide (GRP), protein digestion products in the stomach, and gastric distention.
Acetylcholine is released by cholinergic nerve terminals of the vagus nerve, act on M3muscarinic receptors to increase intracellular IP3 and Ca2+ via the Gq pathway. The vagus nerve can thus increase gastric acid secretion through direct action on parietal cells (acetylcholine), or indirectly through gastrin and histamine.
Atropine, an anticholinergic, can act to block acetylcholine action on parietal cells. Atropine only acts as a partial blockade of acid secretion because it does not act to inhibit GRP release.
In an attempt to treat a gastric ulcer, a researcher gives several infusions of gastric inhibitory peptide to a patient. Which of the following effects would he most likely observe?
A Increased serum insulin levels
B Increased gastric acid secretion
C Increased intestinal motility
D Decreased serum insulin levels
E Increased bile secretion
Despite its name, GIP stimulates insulin release. Only at supraphysiologic levels does it decrease gastric acid secretion. One way to help recall its effects on insulin is to know that an alternative name for GIP is “Glucose-dependent Insulinotropic Peptide.”Gastric Inhibitory Peptide (Glucose-dependent Insulinotropic Peptide, GIP) has an endocrine function to stimulate insulin release an an exocrine function to decrease acid secretion.
GIP is produced by K cells of the duodenum and jejunum.
GIP secretion is stimulated by the presence of the following substances in the small intestine:
Fatty acids
Amino acids
Orally ingested glucose
Oral glucose is more effective than intravenous glucose in causing insulin release due to GIP secretion.
What is the function of secretin?
Secretin acts to
Increase pancreatic HCO3- secretion, allowing for neutralization of the gastric acid in the duodenum and function of pancreatic enzymes.
Decrease gastric acid secretion
Increase bile secretion
Secretin is produced by S cells in the duodenum.
Secretin secretion is stimulated by acid and fatty acids in the lumen of the duodenum.
- Peptide hormone
- Aids regulation of duodenal pH
- Inhibits secretion of gastric acid
- Stimulates secretion of bicarbonate
