52 Questions
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?
Submucosa layer
What is the outermost layer of the intraperitoneal organs in the GI tract?
Serosa
Which layer of the GI tract is primarily formed of areolar connective tissue covered with mesothelium?
Serosa
Which layer of the GI tract is responsible for absorbing the end products of digestion into the blood?
Mucosa layer
What surrounds the submucosa and is responsible for segmentation and peristalsis in the GI tract?
Muscularis externa
Which organ is involved in the digestion of proteins?
Stomach
Which organ initiates the digestion of polysaccharides?
Mouth
Which organ is primarily involved in the absorption of water and electrolytes?
Large intestine
Which organ delivers nutrient-rich venous blood drainage from the digestive viscera to the liver?
Liver
Which structure surrounds and supports the digestive organs in the abdomen?
Peritoneum
Which activity is not an essential activity of the digestive system?
Assimilating
Which organ is involved in the initiation of propulsion by swallowing?
Esophagus
Which blood vessels supply the intestinal blood supply?
Celiac artery
Which organ contributes to the breakdown of food by mechanical action?
Teeth
Which organ delivers the product chyme into the small intestine?
Stomach
Which organ is not considered an accessory organ of the digestive system?
Stomach
Which organ is involved in the digestion of fats?
Small intestine
What is the role of parietal cells in the stomach?
Secrete HCL and intrinsic factor
What activates the protein digesting enzyme pepsin in the stomach?
Hydrochloric acid
What is the essential role of intrinsic factor in the small intestine?
Vitamin B12 absorption
What are the stimuli for the gastric phase of gastric secretion?
Distension, peptides, and low acidity
Which chemicals influence HCl secretion in parietal cells?
Ach, gastrin, and histamine
What are the two major intrinsic nerve plexuses of the enteric nervous system?
Submucosal and myenteric
What do the exocrine glands of the pancreas produce?
Digestive enzymes and bicarbonate
Which enzymes are critical for protein digestion and are secreted by the pancreas?
Trypsin and chymotrypsin
What triggers the intrinsic myenteric defecation reflex?
Distention of rectal wall
Which reflex involves the relaxation of the internal anal sphincter?
Intrinsic myenteric defecation reflex
What is the chief bile pigment?
Bilirubin
Where is the liver located in the body?
Right hypochondriac and epigastric region
What are the two main defecation reflexes?
Intrinsic myenteric defecation reflex and parasympathetic defecation reflex
What do hepatocytes in the liver secrete?
Bile
What enhances the intrinsic myenteric defecation reflex?
Parasympathetic nerve fibers
What is the function of bile salts in the digestive process?
Digesting and absorbing fats
What are the components of bile?
Bile salts, bile pigments, cholesterol, triglycerides, phospholipids, electrolytes
What is the role of the liver sinusoids?
Blood filtration and nutrient absorption
What is the blood supply to the liver?
Hepatic artery and portal vein
What is the function of hepatocytes in the liver?
Secrete bile, store glucose as glycogen, detoxify blood
Which enzyme is responsible for digesting dietary fat into 2-monoglyceride and free fatty acids for absorption?
Pancreatic lipase
What is the primary role of the colon in the digestive system?
Absorbing water and electrolytes
What is the pattern of smooth muscle contractions that propels food through the esophagus and intestines?
Peristalsis
What is the involuntary response controlled by the autonomic and somatic nervous systems, promoting or inhibiting bowel movements?
Defecation reflex
Which enzyme hydrolyses starch into maltose and other fragments, aiding in carbohydrate digestion?
Amylase
What is the role of the pancreas in maintaining fluid balance, absorbing vitamins, processing fiber, and hosting bacteria?
Producing digestive enzymes
What is the chief function of trypsin and chymotrypsin from the pancreas?
Digesting proteins into peptides
What is the function of carboxypeptidase and peptidases on the surface of small intestinal cells?
Breaking down peptides into amino acids
What is the target of pancreatic lipase for obesity management?
Dietary fat
What is the primary role of amylase in pancreatic secretions?
Hydrolysing starch into maltose
What is the function of bicarbonate and water in pancreatic juice secreted by epithelial cells in pancreatic ducts?
Neutralizing stomach acid
What is the role of the colon in long-term health?
Absorbing water and electrolytes
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.
Test your knowledge of defecation reflexes and liver anatomy as well as digestive enzymes and colon function with this quiz. Assess your understanding of intrinsic and parasympathetic defecation reflexes, liver anatomy, digestive enzymes, fat digestion, and the role of the colon in maintaining fluid balance and processing fiber.
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