Questions and Answers
Which layer of the GI tract is responsible for segmentation and peristalsis?
Muscularis externa
Which layer of the GI tract secretes mucus, digestive enzymes, and hormones?
Mucosa layer
What is the major function of the mucosa layer of the GI tract?
Protect against infectious disease
Which layer of the GI tract contains areolar connective tissue and a rich blood and lymphatic vessel supply?
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What is the outermost layer of the intraperitoneal organs in the GI tract?
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Which layer of the GI tract is primarily formed of areolar connective tissue covered with mesothelium?
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Which layer of the GI tract is responsible for absorbing the end products of digestion into the blood?
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What surrounds the submucosa and is responsible for segmentation and peristalsis in the GI tract?
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Which organ is involved in the digestion of proteins?
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Which organ initiates the digestion of polysaccharides?
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Which organ is primarily involved in the absorption of water and electrolytes?
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Which organ delivers nutrient-rich venous blood drainage from the digestive viscera to the liver?
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Which structure surrounds and supports the digestive organs in the abdomen?
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Which activity is not an essential activity of the digestive system?
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Which organ is involved in the initiation of propulsion by swallowing?
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Which blood vessels supply the intestinal blood supply?
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Which organ contributes to the breakdown of food by mechanical action?
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Which organ delivers the product chyme into the small intestine?
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Which organ is not considered an accessory organ of the digestive system?
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Which organ is involved in the digestion of fats?
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What is the role of parietal cells in the stomach?
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What activates the protein digesting enzyme pepsin in the stomach?
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What is the essential role of intrinsic factor in the small intestine?
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What are the stimuli for the gastric phase of gastric secretion?
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Which chemicals influence HCl secretion in parietal cells?
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What are the two major intrinsic nerve plexuses of the enteric nervous system?
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What do the exocrine glands of the pancreas produce?
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Which enzymes are critical for protein digestion and are secreted by the pancreas?
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What triggers the intrinsic myenteric defecation reflex?
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Which reflex involves the relaxation of the internal anal sphincter?
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What is the chief bile pigment?
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Where is the liver located in the body?
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What are the two main defecation reflexes?
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What do hepatocytes in the liver secrete?
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What enhances the intrinsic myenteric defecation reflex?
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What is the function of bile salts in the digestive process?
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What are the components of bile?
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What is the role of the liver sinusoids?
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What is the blood supply to the liver?
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What is the function of hepatocytes in the liver?
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Which enzyme is responsible for digesting dietary fat into 2-monoglyceride and free fatty acids for absorption?
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What is the primary role of the colon in the digestive system?
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What is the pattern of smooth muscle contractions that propels food through the esophagus and intestines?
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What is the involuntary response controlled by the autonomic and somatic nervous systems, promoting or inhibiting bowel movements?
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Which enzyme hydrolyses starch into maltose and other fragments, aiding in carbohydrate digestion?
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What is the role of the pancreas in maintaining fluid balance, absorbing vitamins, processing fiber, and hosting bacteria?
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What is the chief function of trypsin and chymotrypsin from the pancreas?
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What is the function of carboxypeptidase and peptidases on the surface of small intestinal cells?
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What is the target of pancreatic lipase for obesity management?
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What is the primary role of amylase in pancreatic secretions?
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What is the function of bicarbonate and water in pancreatic juice secreted by epithelial cells in pancreatic ducts?
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What is the role of the colon in long-term health?
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Study Notes
Defecation Reflexes and Liver Anatomy Summary
- Two main defecation reflexes: intrinsic myenteric defecation reflex and parasympathetic defecation reflex
- Intrinsic reflex: triggered by distention of rectal wall, signals to colon increase peristalsis, involves myenteric plexus and internal anal sphincter relaxation
- Parasympathetic reflex: similar to intrinsic reflex, involves parasympathetic nerve fibers, enhances intrinsic reflex, causes rapid emptying of sigmoid colon
- Other defecation reflexes: gastrocolic reflex, gastrolienal reflex, enterogastric reflex, duodenocolic reflex, can be stimulated or inhibited by stomach or duodenum irritation
- Gastrointestinal reflexes can involve peritoneum, kidney, and bladder, including peritoneointestinal, renointestinal, and vesicointestinal reflexes
- Liver anatomy: largest gland in the body, located in the right hypochondriac and epigastric region, 4 lobes (right, left, caudate, quadrate), blood supply from hepatic artery and portal vein
- Liver cells called hepatocytes, form liver lobules, central vein, portal triad, liver sinusoids, bile canaliculi
- Hepatocytes secrete bile, store glucose as glycogen, use amino acids to make plasma proteins, store fat-soluble vitamins, detoxify blood
- Bile is alkaline, yellow/green, contains bile salts, bile pigments, cholesterol, triglycerides, phospholipids, electrolytes
- Bile salts aid in the digestive process by digesting and absorbing fats, recycled through enterohepatic circulation
- Bilirubin is the chief bile pigment, a waste product of heme of hemoglobin, absorbed from blood by liver cells, excreted into bile, metabolized by bacteria in the small intestine
- Protein absorption: dietary protein and protein from used mucosal cells digested down to amino acid monomers for absorption
Digestive Enzymes and Colon Function
- Trypsin and chymotrypsin from the pancreas digest proteins into peptides, but cannot break them down into single amino acids.
- Carboxypeptidase and peptidases on the surface of small intestinal cells further break down peptides into amino acids.
- Pancreatic lipase, delivered into the gut, digests dietary fat into 2-monoglyceride and free fatty acids for absorption.
- Normal fat digestion depends on secretions from both the pancreas and the liver, and pancreatic lipase is targeted for obesity management.
- Amylase in pancreatic secretions hydrolyses starch into maltose and other fragments, aiding in carbohydrate digestion.
- The pancreas produces various other digestive enzymes like ribonuclease, deoxyribonuclease, gelatinase, and elastase.
- Bicarbonate and water, critical for neutralizing stomach acid, are secreted into pancreatic juice by epithelial cells in pancreatic ducts.
- The colon's function includes absorbing water and electrolytes, storing undigested food, and eliminating solid waste (feces).
- Peristalsis is a pattern of smooth muscle contractions that propels food through the esophagus and intestines.
- Peristalsis is mediated by the intestine's local, intrinsic nervous system and involves distinct reflexes in response to food in the lumen.
- The defecation reflex is an involuntary response controlled by the autonomic and somatic nervous systems, promoting or inhibiting bowel movements.
- The colon's role in maintaining fluid balance, absorbing vitamins, processing fiber, and hosting bacteria is crucial for long-term health.
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