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Questions and Answers
What is the function of the circular muscle layer in the muscularis externa?
Which organs have an adventitia layer but lack a serosa?
In organs lacking a serosa, what is the function of the adventitia layer?
Which two organs are among those that lack a serosa and have an adventitia?
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What is the role of the longitudinal muscle layer in the muscularis externa?
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What is the role of the epiglottis during the pharyngeal phase of swallowing?
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What is the function of the lower esophageal sphincter?
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What is a common condition associated with the lower esophageal sphincter malfunction?
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Where does the esophagus pass through to enter the stomach?
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What is a complication that can arise due to a hiatal hernia?
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What type of epithelium is found in the mucosal layer of the esophagus?
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What is the primary function of the acinar cells in the pancreas?
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Where do the pancreatic islets, responsible for secreting hormones such as insulin and glucagon, come from?
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Which component of the pancreatic juice is responsible for neutralizing stomach acid in the duodenum?
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What is the approximate daily production of pancreatic juice by the human body?
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Which part of the pancreas releases the pancreatic juice into the duodenum?
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What is the function of the accessory pancreatic duct in some individuals?
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What is the function of bile?
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Where is most of the liver located in the human body?
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What is the main function of the gallbladder?
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Where does bile leave the gallbladder?
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What triggers contractions in the gallbladder to release bile?
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What are the pouches found along the large intestine called?
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True or False: The large intestine has villi like the small intestine.
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True or False: The caudate lobe of the liver is located between the right and left lobes.
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True or False: The falciform ligament separates the quadrate lobe from the caudate lobe of the liver.
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True or False: The round ligament is formed by the degeneration of the fetal umbilical vein.
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What is the function of the Myenteric neural plexus?
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What is the primary function of the submucosal neural plexus?
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What is the role of the muscularis mucosae in the digestive system?
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Which type of muscle contraction is responsible for pushing food forward in the digestive tract?
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What is the main mechanical processing of food done by in the mouth?
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Where is the lingual frenulum located?
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Study Notes
Organs and Layers
- Organs in the abdominal cavity have a serosa layer, except for those that have an adventitia layer, which includes the pharynx, esophagus, and rectum.
- Adventitia is a dense network of collagen fibers that anchors organs to nearby structures.
Muscular Layer
- The muscular layer (muscularis externa) is composed of two smooth muscle layers:
- Circular muscle layer: contraction decreases the diameter of the lumen.
- Longitudinal muscle layer: contraction shortens the length of the area.
- Contraction of both layers mechanically processes food and moves it along the tract.
Pharyngeal Phase
- Begins when the bolus reaches the pharynx.
- No longer under conscious control.
- Uvula and soft palate close off the nasopharynx.
- Pharynx constricts in an up and down motion, forcing the bolus downwards into the esophagus.
Esophageal Phase
- Begins when the bolus enters the esophagus.
- Moves food via peristalsis to the stomach.
- Two sphincters associated with the esophagus:
- Upper esophageal sphincter: prevents regurgitation.
- Lower esophageal sphincter (also called cardiac sphincter): prevents stomach acid from going back up.
Esophagus
- Carries solids and liquids from the pharynx to the stomach.
- Contains mucosa, submucosa, and muscular layers.
- Mucosa and submucosa layers produce mucus, making it easier for the bolus to travel down the esophagus.
- Two histological differences found in the esophagus.
Pancreas
- Has an endocrine and exocrine function.
- Endocrine function: produces hormones such as insulin and glucagon from pancreatic islets.
- Exocrine function: produces pancreatic juice containing digestive enzymes from pancreatic acini.
Large Intestine
- Haustra: pouches along the large intestine that house feces.
- Longitudinal layer is restricted to a strip called Taenia coli.
- Omental appendices: hanging adipose tissue.
Histology of the Large Intestine
- Typical structure of the digestive tract but with an absence of villi.
- Simple columnar epithelium lines the lumen.
- Goblet cells produce mucus.
- Intestinal glands secrete intestinal juice.
Accessory Digestive Organs
- Liver:
- Largest visceral organ.
- Four lobes: right, left, quadrate, and caudate.
- Falciform ligament separates the right and left lobes.
- Produces 700mL of bile daily.
- Gallbladder:
- Stores and modifies bile.
- Two main functions: stores bile and modifies bile.
- Bile pathway: bile from the liver goes to the gallbladder, then to the cystic duct, and finally to the bile duct.
Bile Pathway
- Bile from the liver goes to the gallbladder.
- Bile leaves the gallbladder via the cystic duct.
- Bile duct connects to the duodenum of the small intestine.
- Sphincter at the end of the bile duct opens when chyme is present in the duodenum.
Pancreas
- Found in the upper left quadrant of the abdomen.
- Behind the stomach.
- Has a sphincter that controls the release of pancreatic juice.
Histology of the Digestive Tract
- Mucosa:
- Mucosal epithelium and lamina propria.
- Laminar propria is a little bit of alveolar connective tissue.
- Sensory nerve endings, lymphatic vessels, and blood vessels nourish the avascular epithelium.
- Submucosa:
- Irregularly arranged dense fibrous connective tissue.
- Submucosal glands secrete into the lumen.
- Innervated by the submucosal neural plexus.
Movements of the Digestive System
- Peristalsis:
- Forward squeezing wave motion.
- Moves the bolus throughout the digestive tract.
- Circular muscle fibers contract in one area, then longitudinal muscles contract.
- Segmentation:
- Turning, fragmented motion.
- Mixes the bolus with digestive materials.
- Found in the small intestine.
Digestive System Video 2
- Mechanical processing of food is done by the tongue, teeth, and hard palate.
- Saliva and mucus coat food to make it easier to swallow.
- Saliva has enzymes, and digestion begins in the oral cavity.
Histology of the Oral Cavity
- Mucosa is made of non-keratinized stratified epithelium.
- Soft palate is posterior to the hard palate.
- Uvula guards the opening to the oropharynx.
Anatomy of the Mouth
- Lips:
- Under each lip is a frenulum.
- Frenulum helps keep the lips in place.
- Gingiva (gums):
- Surround the teeth.
- Protect the tooth.
- Teeth:
- Imbedded between the maxilla and mandibular bone.
- Deciduous teeth fall out, and permanent teeth push them out.
- Enamel is the hardest substance in the human body.
- Dentine is underneath the enamel.
- Pulp cavity has blood vessels and nerves.
- Root canal allows blood vessels and nerves to reach the tooth.
- Tongue:
- Has its own frenulum.
- Keeps the tongue down.
- Without it, we can choke on our own tongue.
Saliva
- Three salivary glands:
- Parotid gland: near the ear, produces 25% of saliva.
- Submandibular gland: under the jaw, produces 70% of saliva.
- Sublingual gland: under the tongue, smallest salivary gland, produces 5% of saliva.
- Two types of saliva:
- Mucus saliva: acts as a binding agent.
- Serous saliva: contains enzymes and water.
Swallowing Process
- Three phases:
- Buccal phase: conscious decision to swallow.
- Pharyngeal phase: begins when the bolus reaches the pharynx.
- Esophageal phase: begins when the bolus enters the esophagus.
- Tip of the tongue touches just behind the superior front teeth.
- Tongue protrudes backwards, forcing the bolus to the pharynx.
- Uvula prevents the bolus from going up into the nasopharynx.
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Description
Test your knowledge on the organs and tissues found in the abdominal cavity, including the mesenteric proper, lesser omentum, greater omentum, transverse mesocolon, sigmoid mesocolon, and the falciform ligament. Learn about the differences between organs with serosa and adventitia layers, and understand the composition of the muscular layer (muscularis externa).
