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What is the primary function of the stomach in digestion?
What is the primary function of the stomach in digestion?
Which cranial nerve is primarily responsible for the sensory input during the swallowing reflex?
Which cranial nerve is primarily responsible for the sensory input during the swallowing reflex?
What structure acts as a valve at the lower end of the esophagus?
What structure acts as a valve at the lower end of the esophagus?
What initiates the peristaltic contraction in the esophagus when swallowing?
What initiates the peristaltic contraction in the esophagus when swallowing?
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Which of the following statements describes the role of gastric juices?
Which of the following statements describes the role of gastric juices?
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What is one function of the tongue in the oral cavity?
What is one function of the tongue in the oral cavity?
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Which major nerve is responsible for the motor function of the tongue?
Which major nerve is responsible for the motor function of the tongue?
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What type of saliva does the sublingual gland produce?
What type of saliva does the sublingual gland produce?
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The parotid gland produces which type of saliva?
The parotid gland produces which type of saliva?
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What is the primary role of saliva in the digestive process?
What is the primary role of saliva in the digestive process?
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Which areas does the pharynx connect?
Which areas does the pharynx connect?
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Which condition describes the role of the nasopharynx?
Which condition describes the role of the nasopharynx?
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Which nerves provide sensory innervation to the pharynx?
Which nerves provide sensory innervation to the pharynx?
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Which region of the stomach is located superiorly to the gastroesophageal junction?
Which region of the stomach is located superiorly to the gastroesophageal junction?
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What structure prevents the reflux of duodenal contents into the stomach?
What structure prevents the reflux of duodenal contents into the stomach?
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What is the primary function of the small intestine?
What is the primary function of the small intestine?
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Which part of the small intestine is the first and widest segment?
Which part of the small intestine is the first and widest segment?
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What is the role of intestinal villi in the small intestine?
What is the role of intestinal villi in the small intestine?
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What is the average length of the small intestine?
What is the average length of the small intestine?
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Which structure marks the boundary between the duodenum and jejunum?
Which structure marks the boundary between the duodenum and jejunum?
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What is the primary blood supply to the duodenum?
What is the primary blood supply to the duodenum?
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What anatomical feature in the small intestine increases its absorption area from 0.33m2 to 200m2?
What anatomical feature in the small intestine increases its absorption area from 0.33m2 to 200m2?
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Which part of the stomach serves as the wide part of the pylorus and assists in mixing food?
Which part of the stomach serves as the wide part of the pylorus and assists in mixing food?
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What is the primary function of the jejunum?
What is the primary function of the jejunum?
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Which feature distinguishes the large intestine from the small intestine?
Which feature distinguishes the large intestine from the small intestine?
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What occurs as a result of the gastroileac reflex?
What occurs as a result of the gastroileac reflex?
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Which part of the large intestine is primarily responsible for the absorption of important vitamins produced by bacterial action?
Which part of the large intestine is primarily responsible for the absorption of important vitamins produced by bacterial action?
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What feature gives the colon its sacculated appearance?
What feature gives the colon its sacculated appearance?
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Which structure marks the ending of the ileum?
Which structure marks the ending of the ileum?
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What is NOT a function of the large intestine?
What is NOT a function of the large intestine?
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How long is the ileum on average?
How long is the ileum on average?
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Which artery supplies the viscera that derive embryologically from the hindgut?
Which artery supplies the viscera that derive embryologically from the hindgut?
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What is the significance of the Glisson's Capsule in relation to the liver?
What is the significance of the Glisson's Capsule in relation to the liver?
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Which ligament is a remnant of the left umbilical vein found in the liver?
Which ligament is a remnant of the left umbilical vein found in the liver?
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At which vertebral level is the Superior Mesenteric Artery located?
At which vertebral level is the Superior Mesenteric Artery located?
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How many segments does the liver divide into based on its vascular supply?
How many segments does the liver divide into based on its vascular supply?
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What structure serves as the starting point of the large intestine?
What structure serves as the starting point of the large intestine?
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Which part of the large intestine descends into the pelvic cavity?
Which part of the large intestine descends into the pelvic cavity?
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What type of muscle controls the external anal sphincter?
What type of muscle controls the external anal sphincter?
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What is the main stimulus for the parasympathetic defecation reflex?
What is the main stimulus for the parasympathetic defecation reflex?
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At which vertebral level does the rectum begin?
At which vertebral level does the rectum begin?
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Which artery does NOT branch from the celiac trunk?
Which artery does NOT branch from the celiac trunk?
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Which of the following is an involuntary response during defecation?
Which of the following is an involuntary response during defecation?
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What is the primary function of the rectum?
What is the primary function of the rectum?
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Study Notes
PT102 Other Organ Systems 1
- Prepared by: John Patrick R. Lentejas, PTRP, MSc
- Date: September 30, 2024
- This document is for PT102 students registered for Semester 1, Academic Year 2024–2025. Copyright belongs to the College of Allied Medical Professions, University of the Philippines Manila.
Digestive System - Learning Objectives
- Explain the function and processes of the digestive system
- Describe the structure and function of the layers of the digestive canal
- Identify the location and function of the structures found in the oral cavity
- Discuss the functional anatomy of the tongue, pharynx, esophagus, stomach, and their innervation and blood supply.
- Identify the location and function of the salivary glands
- Discuss the different stages of swallowing reflex
- Identify the organs located on each abdominal quadrant or region
- Differentiate the regions of small and large intestine in terms of histological specialization, segmental movements, and function
- Discuss the location, function, and histological specialization of the different accessory glands
- Trace the pathway of bile and pancreatic juices from their respective organs to the duodenum
- Trace the pathway of blood from the liver to the general circulation
Digestive System - Function
- Ingestion: taking food into the mouth
- Secretion: release of substances (water, acid, buffers, enzymes) into the digestive canal
- Mixing and propulsion: churning and movement of food through the digestive canal
- Digestion: mechanical and chemical breakdown of food
- Absorption: passage of digested products from the digestive canal into blood plasma and lymph plasma
- Defecation: elimination of feces from the digestive canal
Layers of the Digestive Canal
- Mucosa: inner lining, secretion and absorption, lamina propria (areolar CT), muscular mucosae (folds to increase surface area)
- Submucosa: areolar CT, binding mucosa to muscularis mucosa, blood and lymphatic vessels, MALT
- Muscularis Externa: inner circular layer (decreases lumen diameter), outer longitudinal layer (shortens tube), myenteric plexus (controls and coordinates motor activity)
- Serosa: outer covering, continuation of peritoneal membrane
Oral Cavity
- Roof: hard palate (palatine process of the maxilla and the palatine bone) and soft palate (aponeurosis of tensor palati muscle)
- Function of soft palate: separates nasal and buccal cavities, closes nasopharynx during speaking, swallowing and blowing, prevents food from entering pharynx prematurely
- Floor: tongue and mylohyoid muscles
- Laterally: cheeks (buccal region) – buccinator muscle, zygomatic bone and zygomatic arch
- Oral vestibule: narrow space between lips and cheeks, and gums and teeth
Tongue
- Floor of the oral cavity
- Function: assists in chewing and swallowing, sensory, taste receptors, mechanical processing for speech
- Innervation: anterior 2/3 (general sensation – lingual branch CN V, taste – chorda tympani of CN VII), posterior 2/3 (both taste and sensation – glossopharyngeal nerve), motor – CN XII (hypoglossal nerve)
- Blood Supply: lingual branch of the external carotid artery
Salivary Glands
- Parotid gland: largest, below external auditory meatus, behind ramus of mandible. Secretes enzymes, parasympathetic – glossopharyngeal nerve
- Sublingual gland: beneath the tongue, superior to submandibular glands; produces mucus-rich saliva.
- Submandibular gland: floor of oral cavity; produces mixed saliva (mucus and enzymes). Nerve: both submandibular and sublingual, parasympathetic, facial nerve.
Pharynx
- Musculofascial tube, incomplete anteriorly
- Area behind the nasal, oral cavities, and the larynx
- Funnel-shaped space ending at the level of the 6th cervical vertebra
- Acts as a common entrance to respiratory and alimentary tracts
- Arterial supply: superior thyroid and ascending branches of the external carotid
- Innervation: CN IX (glossopharyngeal) - sensory, CN X (vagus) - motor, Nasopharynx – sensory from maxillary division of CN V
Pharynx - Subdivisions
- Nasopharynx: Communicates with the nasal cavities, location of Pharyngo-tympanic (Eustachian tubes), prevents regurgitation of food through the nose.
- Oropharynx: Lies behind the mouth and tongue, segment between palate and hyoid bone.
- Laryngopharynx: narrowest part, behind the larynx, from tip of epiglottis to the termination of the pharynx in the esophagus at C6.
Esophagus
- Starts from cricoid cartilage (at vertebral level C6) and ends at the gastroesophageal(GE) junction
- Pierces the diaphragm through the esophageal hiatus
- Upper 5% skeletal muscle only, middle 45% both skeletal and smooth muscle, distal 50% smooth muscle only.
- Function: propels swallowed food into the stomach
Esophagus (Sphincters)
- Upper Esophageal Sphincter (UES): Skeletal muscle (Voluntary control) separates the pharynx from the esophagus.
- Lower Esophageal Sphincter (LES): smooth muscle (Involuntary control) separates esophagus from the stomach. The LES prevents GE reflux.
Swallowing Reflex
- Sensory input: CN IX glossopharyngeal
- Swallowing center in medulla oblongata
- Output: Somatic neurons of pharyngeal muscles and upper esophagus, and autonomic (lower esophagus)
- Steps: three stages (voluntary, pharyngeal, esophageal)
Abdominal Quadrants/Regions
- RUQ, LUQ, RLQ, LLQ
- Note specific organ location in each quadrant
Short Intestines
- Occupies all abdominal regions (except left hypochondriac and epigastric).
- Averages 6 meters (20 ft) in length; has a diameter ranging from 4 cm (1.6 in) at the stomach to 2.5 cm (1 in) at the large intestine junction
Duodenum
- First, widest, shortest segment of the small intestines.
- Curves in a C-shape around the head of the pancreas; overlapped by the liver and gallbladder.
- "Mixing bowl" receiving chyme from stomach and digestive secretions (bile and pancreatic juice).
- Receives the common bile duct and main pancreatic duct at the hepatopancreatic ampulla (ampulla of Vater).
- Blood Supply: Superior Mesenteric Artery
Duodenum (cont.)
- Structures relating to digestive functions: common bile duct, and the pancreatic duct.
- Duodenal papilla: opening where the ampulla of Vater is connected, closed off by the sphincter of Oddi.
Jejunum
- Duodenojejunal flexure: marks boundary between duodenum and jejunum.
- Intraperitoneal; within the peritoneal cavity, supported by mesentery
- About 2.5 meters (8 ft) long. Bulk of chemical digestion and nutrient absorption occur.
Ileum
- Intraperitoneal; third and last segment of small intestine, averaging 3.5 meters (12 ft) long.
- Site of Vitamin B12 absorption.
- Ileocecal valve: controls flow of materials from ileum to large intestine.
- Gastroileal reflex: presence of food in stomach results in elevated peristalsis in ileum, relaxing the ileocoecal sphincter, moving intestinal contents to the large intestine.
Large Intestine
- Wider caliber than the small intestine
- Features: Taenia Coli (longitudinal muscular bands), haustration (sacculated appearance of colon walls), blood supply (superior and inferior mesenteric artery)
- Mass movements: toward the rectum.
- Function: reabsorption of water and electrolytes, compaction of intestinal contents into feces, absorption of vitamins produced by bacterial actions, and storage of fecal material before defecation.
Large Intestine (cont.)
- Three parts: cecum, colon, rectum.
- Cecum: first part resembling a pouch, ileocecal junction, and vermiform appendix
- Colon (ascending, transverse, descending, sigmoid): largest section, inverted U-shape, descends into the pelvic cavity
- Rectum: last 15cm (6in) of large intestine and end of the digestive tract
- Parasympathetic defecation reflex: removes undigested feces; stimuli distension of rectal wall (S2-S4 spinal cord level)
Accessory Organs
- Liver: largest visceral organ, regenerative capacity, Glisson's capsule, falciform ligament divides into right and left parts, major segments of liver are brought by subdivisions of the hepatic artery, portal vein, and hepatic ducts (dividing L and R lobes into 4 segments each). Coronary ligament supports the liver to the diaphragm; round ligament/ligamentum teres found inferiorly of falciform ligament; remnant of left umbilical vein.
- Gall Bladder: stores and concentrates bile until it is transported to the duodenum via the common bile duct, attached to fossa at inferior surface of liver, cystic duct joins hepatic duct to form common bile duct
- Pancreas: lobulated, elongated gland at epigastric region (posterior to the stomach), retroperitoneal. Parts: head (clasped by duodenum), neck, body, tail (extends to left hypochondrium).
Liver Lobules
- Basic functional units of the liver (hexagonal in cross-sectional area)
- 6 portal areas (hepatic triads) on each corner of the lobule
- Composed of portal area which includes: hepatic portal vein, hepatic artery proper, and bile ductule
- Blood flow: Hepatic artery supplies the oxygen to the liver and hepatic portal vein supplies nutrients and other chemicals from the intestine. This blood flows through the sinusoids of the lobules > liver hepatocytes then absorb and secrete into bloodstream > central vein > hepatic vein > inferior vena cava.
Liver Functions
- Metabolic regulation: all blood from GI tract enters hepatic portal system; absorbs nutrients and toxins; absorbs fat-soluble vitamins (A, D, E, K). Removal of old red blood cells, synthesis of plasma proteins, synthesis and secretion of bile.
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Description
Test your knowledge on the digestive system's anatomy and functions in this comprehensive quiz. Covering key structures, functions, and specific nerves, this quiz is ideal for students in biology or health sciences. Explore how various components work together in digestion.
