Human Digestive System Quiz

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Questions and Answers

What is the primary role of the mesocolon in the human body?

To facilitate respiration

To absorb nutrients from digested food

To produce digestive enzymes

To anchor the colon to the posterior body wall (correct)

Which of the following is NOT a component directly related to the greater omentum?

Descending colon

Transverse colon

Mesentery (correct)

Greater curvature of the stomach

What function does the mesentery serve in the digestive system?

It secretes hormones that regulate digestion

It aids in the mechanical breakdown of food

It warns the body of toxic substances

It holds many blood vessels supplying the intestines (correct)

What is the primary site for most digestion and nearly all absorption of nutrients?

Small intestine Signup and view all the answers

Which structure is responsible for carrying the sigmoid colon?

Mesocolon Signup and view all the answers

Which statement correctly describes the jejunum's relationship with the mesentery?

The jejunum is suspended within the mesentery, allowing for mobility. Signup and view all the answers

What substance contributes to digestion and is secreted by the liver?

Bile Signup and view all the answers

Which of the following describes the liver's anatomical location?

Inferior to the diaphragm Signup and view all the answers

How many lobes does the liver have?

Four Signup and view all the answers

What plays a significant role in the absorption of alcohol in the digestive system?

Stomach emptiness Signup and view all the answers

Which type of gastric cell is responsible for secreting hydrochloric acid?

Parietal cell Signup and view all the answers

What is the primary function of chief cells in the gastric glands?

Secreting gastric lipase and pepsinogen Signup and view all the answers

Which of the following statements about gastric juice is true?

It mainly consists of water, hydrochloric acid, and pepsin. Signup and view all the answers

What hormone is secreted by G cells?

Gastrin Signup and view all the answers

Which type of gastric cell secretes mucus to provide protection for the stomach lining?

Mucous neck cell Signup and view all the answers

What structure in the colon is primarily responsible for the pouches known as haustra?

Taenia coli Signup and view all the answers

Which type of muscle makes up the internal anal sphincter?

Smooth muscle Signup and view all the answers

How do the taenia coli contribute to the structure of the colon?

They maintain the haustra formation. Signup and view all the answers

Which component of the anal sphincter is under voluntary control?

External anal sphincter Signup and view all the answers

What is the role of the haustra in the colon?

Storage of fecal matter Signup and view all the answers

Which structure connects the cecum to the ileum?

Ileocecal valve Signup and view all the answers

What is the significance of the external anal sphincter being composed of skeletal muscle?

It permits voluntary control over defecation. Signup and view all the answers

What is one of the unique features of the colon that distinguishes it from other sections of the intestine?

Formation of haustra Signup and view all the answers

What is the primary function of the digestive system?

To process food and extract nutrients while eliminating waste Signup and view all the answers

Which process involves the physical breakdown of food?

Mechanical digestion Signup and view all the answers

Which organ is NOT part of the digestive tract?

Liver Signup and view all the answers

What type of nutrients are commonly found in a usable form without digestion?

Vitamins Signup and view all the answers

Which of the following is a role of mesenteries in the digestive system?

Prevent the intestines from becoming tangled Signup and view all the answers

The serous membrane lining the abdominal cavity is called the:

Parietal peritoneum Signup and view all the answers

What do digestive enzymes break dietary macromolecules into?

Monomers Signup and view all the answers

Which of the following pairs correctly match the type of digestion with its description?

Chemical digestion - hydrolysis of macromolecules Signup and view all the answers

What is the length of the digestive tract from mouth to anus approximately?

30 feet Signup and view all the answers

Which of the following is NOT considered an accessory organ of the digestive system?

Esophagus Signup and view all the answers

What is the primary function of the duodenum in the small intestine?

Emulsify fats and neutralize stomach acid Signup and view all the answers

Which of the following best describes the jejunum?

The region of the small intestine responsible for most nutrient absorption Signup and view all the answers

What role do Peyer patches play in the ileum?

Act as lymphatic nodules for immune response Signup and view all the answers

How does the ileocecal valve function?

Prevents backflow from the large intestine to the ileum Signup and view all the answers

What structure increases the surface area of the small intestine significantly?

Microvilli Signup and view all the answers

Which characteristic is associated with the jejunum's anatomical features?

Rich blood supply indicated by a red color Signup and view all the answers

Which of the following accurately describes the ileum?

Has a thinner and less muscular wall than the jejunum Signup and view all the answers

What is the main purpose of circular folds in the small intestine?

Promote thorough mixing and nutrient absorption Signup and view all the answers

Study Notes

The Digestive System

The digestive system breaks down food into smaller parts usable by the body
This process is a "disassembly line"
Gastroenterology is the study of the digestive tract, and diseases of the digestive system

Digestive Function

The digestive system processes food, extracts nutrients, and eliminates residual material
The digestive system is a complex process relying on numerous organs and glands.

Facets of Digestion

Mechanical digestion physically breaks down food using teeth and churning actions in the stomach and intestines
Chemical digestion, a series of hydrolysis reactions, breaks down macromolecules using digestive enzymes into smaller monomers
- Polysaccharides into monosaccharides
- Proteins into amino acids
- Fats into monoglycerides and fatty acids
- Nucleic acids into nucleotides
Some nutrients (vitamins, free amino acids, minerals, cholesterol) are in their usable form.

General Anatomy

The digestive system has two main parts:
- Digestive tract (alimentary canal) - a 30-foot long muscular tube starting from the mouth to the anus (mouth, pharynx, esophagus, stomach, small intestine, and large intestine).
- Accessory organs - teeth, tongue, salivary glands, liver, gallbladder, and pancreas. -Diagram of the digestive tract and its associated organs is essential for understanding the anatomy.

Relationship to Peritoneum

Mesenteries are sheets of connective tissue that suspend the stomach and intestines to the abdominal wall, allowing for movement, holding abdominal organs in place, preventing twisting, and containing blood vessels and lymphatic vessels.
Parietal peritoneum is the serous membrane lining the abdominal cavity; it turns inward to form the dorsal and ventral mesenteries that separate and surround the organs.

Mesentery and Mesocolon

Mesentery supports and holds many blood vessels.
Mesocolon anchors the colon to the posterior body wall.

Lesser and Greater Omentum

Lesser omentum–attaches the stomach to the liver
Greater omentum—covers the intestines like an apron.

The Tongue

Manipulates food between teeth while avoiding being bitten
Extracts food after a meal
Highly sensitive
Covered with nonkeratinized stratified squamous epithelium
Lingual papillae are bumps and projections on the tongue; sites for taste buds (gustation)

Teeth

Humans have two sets of teeth: primary (baby) teeth (20) and secondary (permanent) teeth (32).
Diagrams showcasing the different types of teeth are vital for memorization.

Tooth and Gum Disease

The mouth contains over 700 species of microorganisms, mainly bacteria
- Plaque is a sticky residue made of bacteria and sugars
- Calculus (calcified plaque) allows for bacterial invasion of the sulcus.
- Gingivitis is inflammation of the gums
- Periodontal disease is the destruction of the supporting bone around teeth, potentially resulting in tooth loss
- Dental caries (cavities) is created by bacteria eating sugars releasing acids that dissolve minerals in teeth.
- Root canal therapy fixes cavities that have reached the pulp.

Mastication

Mastication (chewing) breaks down food into smaller pieces, exposing more surface area for digestive enzymes.
The first step in digestive breakdown
Chewing is an involuntary reflex triggered by food stimulation of oral receptors

Saliva

Moistens the mouth Begins starch and fat digestion
Cleanses teeth and inhibits bacterial growth
Dissolves molecules for taste buds
Moistens and binds food for swallowing.

Saliva (Composition)

Hypotonic solution of water and several substances
- Salivary amylase - enzyme that begins starch digestion
- Lingual lipase- enzyme that digests fat
- Mucus- lubricates food
- Lysozyme- kills bacteria
- Immunoglobulin A (IgA)- antibody
- Electrolytes (Na+, K+, Cl-, phosphate, and bicarbonate)

Salivary Glands

Illustrations showcasing the various salivary glands are essential
Parotid, submandibular, and sublingual glands are three types commonly present and illustrated.

Pharynx

A muscular funnel connecting the oral cavity to the esophagus and the nasal cavity to the larynx.
Pharyngeal constrictors (superior, middle, and inferior) force food downwards during swallowing
The inferior constrictor remains contracted to prevent air from entering the esophagus during swallowing.

Esophagus

A 25-30 cm long muscular tube.
Extends from the pharynx to the cardiac orifice of the stomach.
Passes through the esophageal hiatus in the diaphragm.
The lower esophageal sphincter prevents stomach contents from regurgitating and protects esophageal mucosa from stomach acid.
Esophageal glands secrete mucus in the submucosa.

Swallowing (Deglutition)

A complex action involving over 22 muscles in the mouth, pharynx, and esophagus.
Occurs in two phases:
- Buccal phase- voluntary control
- Pharyngoesophageal phase- involuntary control using peristalsis.

X-ray: Swallowing in Esophagus

X-rays show the progression of the bolus through the esophagus using peristaltic contractions.

Upper GI Disorders

GERD (gastroesophageal reflux disease) - frequent reflux of stomach contents into the esophagus
Causes heartburn, esophageal erosion, and lifestyle adjustments for treatment.
Hiatal hernia–part of the stomach protrudes above the diaphragm, potentially causing heartburn. Sometimes it can strangle the stomach tissue. Treatment may include surgery for severe cases.

Stomach

A muscular sac in the upper left abdominal cavity, below the diaphragm, serves as a food storage organ.
Typically holds 1-1.5 liters after a meal, up to 4L extremes.
Mechanically breaks down food, liquefies it, and begins chemical digestion of protein and fat.
Chyme - soupy or pasty mixture of semi-digested food
Most digestion occurs after chyme moves into the small intestine.

Gross Anatomy of Stomach

A J-shaped organ with lesser and greater curvatures
Divided into four regions
- Cardiac region (cardia) is the area near the cardiac orifice.
- Fundic region (fundus) is dome-shaped portion above esophageal attachment.
- Body (corpus) is the largest part of the stomach
- Pyloric region is the narrower portion of the stomach at the inferior end.
- Contains the pyloric (gastroduodenal) sphincter, which regulates the passage of chyme into the duodenum.

Gross Anatomy of Stomach (detail)

Diagram illustrating the lesser and greater curvatures and the four regions (cardiac, fundus, body, pylorus) of the stomach.

Microscopic Anatomy of Stomach

Simple columnar epithelium covers the mucosa, apical regions of the cells are filled with mucin to form and secrete mucus.
Mucosa and submucosa become flat when the stomach is full, form longitudinal wrinkles or gastric rugae when empty.
Gastric pits are depressions in gastric mucosa with tubular glands leading into the pits base.

Cells of Gastric Glands

Gastric glands contain several types of cells:
- Mucous cells- secrete mucus
- G cells (endocrine)- secrete hormone gastrin
- Parietal cells- secrete hydrochloric acid (HCl), intrinsic factor, and ghrelin
- Chief cells - are the most numerous cells, secrete gastric lipase and pepsinogen

Gastric Secretions

Gastric juice - 2-3 liters per day, produced by gastric glands.
Mainly a mixture of water, hydrochloric acid, and pepsin.
Gastric juice is essential for several processes of mechanical and chemical digestion.

Hydrochloric Acid

Gastric juice has a high concentration of HCl.
Parietal cells produce HCl and contain carbonic anhydrase (CAH).
HCl is created and pumped into gastric glands lumen by H+-K+ ATPase pumps.
HCO3 is exchanged for Cl- (chloride shift) from blood plasma, joining H+ to form HCI.
An alkaline tide occurs in the blood, which increases HCO3 in the blood as it leaves the stomach.

Functions of HCl

Activates pepsin and lingual lipase
Breaks down connective tissues and plant cell walls
Helps liquefy food into chyme
Converts ingested ferric ions (Fe3+) into ferrous ions (Fe2+), which are used in hemoglobin synthesis
Contributes to disease resistance by destroying many pathogens

Pepsin

Zymogens - digestive enzymes secreted as inactive proteins. Pepsin is a digestive enzyme secreted in an inactive form, pepsinogen, by chief cells.
HCl removes some amino acids in pepsinogen turning it into pepsin
Autocatalytic effect: Pepsin converts more pepsinogen to pepsin.
This process is necessary to activate pepsin for protein digestion in the stomach.

Gastric Lipase

Produced by chief cells
Aids digestion of 10-15% of dietary fats in the stomach
Rest of fat digestion occurs in the small intestine.

Intrinsic Factor

A glycoprotein secreted by parietal cells
Necessary for the absorption of vitamin B12 in the small intestine.
Intestinal cells absorb the B12-intrinsic factor complex by receptor-mediated endocytosis.
Vitamin B12 needed for hemoglobin creation prevents pernicious anemia.
Stomach secretion of intrinsic factor is crucial for vitamin B12 uptake.

Chemical Messengers

Gastric and pyloric glands have enteroendocrine cells that produce 20+ chemical messengers (hormones or paracrine secretions)
These regulate digestive processes and coordinate digestive tract and central nervous system activity.

Gastric Motility

Swallowing center in the medulla oblongata signals the stomach to relax.
Food stretches stomach, activating a receptive relaxation response.
Stomach shows a rhythm of peristaltic contractions controlled by pacemaker cells.
Food is churned, mixed with gastric juice to promote physical and chemical digestion.
Antrum of pyloric region holds ~30 mL of chyme, releasing ~3 mL at a time to allow for neutralization of stomach acid and to digest nutrients.
The pyloric sphincter prevents excessive emptying into the small intestine to allow for appropriate fluid levels.
A high-fat meal may take up to 6 hours to leave the stomach.

Vomiting (Emesis)

The forceful ejection of stomach and intestinal contents (chyme) from the mouth.
Caused by over stretching of stomach or duodenum, chemical irritants (alcohol, toxins), visceral trauma, or intense pain/psychological/sensory stimuli.
Controlled by center in the medulla oblongata.
Abdominal contractions and rising thoracic pressure force the upper esophageal sphincter to open, and combined with reverse peristalsis.
Chronic vomiting often leads to imbalances in fluids, acid-base, and electrolytes, tooth enamel erosion resulting from the stomach acid, possible respiratory tract issues from acid inhalation.

Protection of the Stomach

Stomach is protected by a thick, highly alkaline mucus coat resisting acid and enzymes.
Tight junctions between epithelial cells prevent gastric juice seeping and digesting connective tissues.
Epithelial cells replace every 3-6 days.
Breakdown of these can lead to gastritis, and peptic ulcers.

Healthy Mucosa and Peptic Ulcer

Gastritis - inflammation of the stomach. Can lead to peptic ulcers as pepsin and HCl erode the stomach wall.
Most ulcers are from acid resistant bacteria, Helicobacter pylori, which can be treated with antibiotics and Pepto-Bismol.

Digestion and Absorption

Most digestion and nearly all absorption occur after the chyme has passed into the small intestine.
Stomach does not absorb any significant amount of nutrients.
Alcohol is absorbed mainly by the small intestine.
Intoxicating effects depend on how fast the stomach empties.

Liver, Gallbladder, and Pancreas

Small intestine receives chyme from the stomach and secretions from the liver and pancreas that enter near the stomach/small intestine junction.

The Liver

Reddish-brown gland inferior to the diaphragm.
Body's largest gland (approx. 1.4 kg/3lbs).
Secretes bile, which aids in digestion.

Gross Anatomy of Liver

Four lobes (right, left, quadrate, caudate).
Gallbladder adheres to a depression on the inferior surface of the liver between the right and quadrate lobes.

Gross Anatomy of Liver (detail)

Diagram illustrating the four lobes (right, left, quadrate, caudate), inferior vena cava, and gallbladder location.

Microscopic Anatomy of Liver

Hepatic lobules are tiny cylinders filling the liver (2mm long, 1mm diameter).
- Consists of central veins.
- Hepatocytes are cuboidal cells around central veins in radiating sheets or plates.
- Hepatic sinusoids are blood-filled channels between the plates, lined by fenestrated endothelium.  
Blood flow through hepatic sinusoids comes directly from intestines for passing nutrients into the blood.

Functions of Hepatocytes

After a meal, hepatocytes absorb glucose, amino acids, iron, vitamins, and other nutrients for use or storage
Remove and degrade hormones, toxins, bile pigments, and drugs.
Secrete albumin, lipoproteins, clotting factors and more.
Between meals, hepatocytes break down stored glycogen and release glucose into the blood.

Bile Ducts

Bile canaliculi are narrow channels where the liver secretes bile
Merge to form the common hepatic duct - bile duct forms by the joining of the common hepatic duct and the cystic duct.
Near duodenum, the bile duct joins the pancreatic duct which forms an expanded chamber for the hepatopancreatic duct.
Ends in the duodenal papilla. The major duodenal papilla contains the hepatopancreatic sphincter which controls opening and closing of bile and pancreatic juice.

Gross Anatomy of Gallbladder, Pancreas, and Bile Passages

Diagram Illustrating the positions of the gallbladder, common hepatic duct, cystic duct, bile duct, accessory pancreatic duct, and pancreatic duct

Gallbladder

Pear-shaped sac on the underside of the liver.
Stores and concentrates bile
About 10cm long
Head (fundus) projects slightly beyond the inferior margin of the liver
Neck leads into cystic duct

Bile

Yellow-green fluid containing minerals, cholesterol, neutral fats, phospholipids, bile pigments, and bile acids.
Bile acids (bile salts) aid in fat digestion by emulsifying fats.
Important for cholesterol removal. 
80% of bile acids reabsorbed, 20% in feces.

Gallstones

Hard masses (biliary calculi) in gallbladder or bile ducts.
Made of cholesterol, calcium carbonate, and bilirubin.
Cholelithiasis is the formation of gallstones, common in obese women over 40. 
Stones may block or create issues in the duct. 
Lithotripsy uses ultrasonic vibrations for breaking down gallstones.

Other Liver Disorders

Cholecystitis – inflammation of the gallbladder, often due to blockage. May require surgery
Hepatitis - inflammation of the liver due to a viral infection.
- Type A (usually foodborne, self-limiting)
- Type B and Type C (more serious, transmitted through body fluid contact, can lead to cirrhosis and liver cancer)
Cirrhosis - Liver inflammation and scarring

The Pancreas

Spongy gland adjacent to the duodenum
12-15cm long, 2.5 cm thick
Head encircled by duodenum, body, and tail on left
Endocrine and exocrine gland 
- Endocrine portion includes pancreatic islets secreting insulin and glucagon. 
- Exocrine portion (99% of Pancreas) secretes pancreatic juice via small ducts that converge on the main pancreatic duct.

The Pancreas (Function)

Pancreatic duct runs the length of the middle portion of the pancreas. It joins the bile duct at the hepatopancreatic ampulla.
Hepatopancreatic sphincter controls release of both bile and pancreatic juice into the duodenum
Accessory pancreatic duct- smaller duct that branches from main pancreatic duct and bypasses the sphincter. 
Pancreatic juice (alkaline) is a mixture of water, enzymes, zymogens, sodium bicarbonate, and electrolytes.

Pancreatic Zymogens

Trypsinogen - secreted into intestinal lumen, converted to trypsin by enterokinase, which is secreted by the small intestine mucosa. Trypsin is autocatalytic- it makes more trypsin.
Chymotrypsinogen- converted to chymotrypsin by trypsin
Procarboxypeptidase - converted to carboxypeptidase by trypsin
Proelastase - converted to elastase by trypsin
Trypsin catalyzes the conversion of all the above.

Pancreatic Enzymes

Other pancreatic enzymes do not digest protein and are not inactive (zymogen).
- Pancreatic amylase - digests starch
- Pancreatic lipase - digests fat
- Ribonuclease and deoxyribonuclease - digest RNA and DNA.

Activation of Pancreatic Enzymes

Illustration showcasing trypsin converting other pancreatic zymogens into their active forms.

Pancreatitis

Inflammation of the pancreas.
Often from alcohol abuse or untreated gallstones.
Sometimes cause is unknown
Common in dogs after large high fat meals
Pancreas releases trypsin, digesting itself causing potential life threatening issues. 
Diagnosis can be made by detecting high levels of amylase and lipase in the blood.

Small Intestine

Coiled mass filling most of the abdominal cavity inferior to the stomach and liver.
Nearly all chemical digestion and nutrient absorption occur here.
2.7-4.5m long.

Gross Anatomy of Small Intestine

Duodenum - the first 25 cm that begins at the pyloric valve and ends at the duodenojejunal flexure.
- Receives stomach contents, pancreatic juice, and bile.
- Neutralizes stomach acid
- Bile acids emulsify fats
- Pepsin is inactive; pancreatic enzymes take over chemical digestion.
Jejunum - first 40% beyond duodenum
Ileum - last 60% small intestine.
Ileocecal junction - ileum joins cecum of the large intestine.
Ileocecal valve regulates movement to the large intestine.

Microscopic Anatomy of Small Intestine

Tissue layers have modifications for nutrient digestion and absorption.  
- Lumen lined with simple columnar epithelium
Large internal surface area from the circular folds (plicae circulares), villi (increases surface by 10), and microvilli (increases surface by 20).

Intestinal Motility

Segmentations - movement where ring-like constrictions appear along the intestine allowing for mixing of chyme. Relax and contract in new locations, most common type of intestinal contractions. Occurs when most nutrients are absorbed, and undigested food remnants remain. Segmentation declines, and peristalsis begins. This allows for mixing of chyme with intestinal juice, bile, and pancreatic juice; churning and contact with mucosa; and movement of residue to the large intestine.
Peristalsis - gradual movement of contents towards the colon. Begins in the duodenum and travels 10-70cm, followed by another wave starting further down the tract. The Ileocecal valve is normally closed but triggered by the gastroileal reflex; segmentation is enhanced, and the valve relaxes.

Lactose Intolerance

Lactose passes undigested into the large intestine.
This increases intestinal osmolarity, causing water retention in the colon and diarrhea.
Gas production results from bacteria fermenting the undigested lactose.
Common in varying degrees across populations.

Gross Anatomy of Large Intestine

Receives 500ml of indigestible residue daily
Reduces to 150ml of feces via absorbing water and salts, and eliminates feces by defecation.
- Cecum: inferior to ileocecal valve; appendix is attached to the lower end. 
- Ascending colon
- Hepatic flexure 
- Transverse colon
- Splenic flexure 
- Descending colon
- Sigmoid colon leads to the pelvis
- Rectum - portion ending at the anal canal. 
- Anal canal - final 3cm of the large intestine
- Anal canal (column and sinuses) have anal columns and sinuses that exude mucous for defecation. 
- Hemorrhoids- distended veins that may protrude into anal canal or form bulges external to the anus

Gross Anatomy of Large Intestine (Detail) 

Diagram Illustrating the location of the different sections and their relationship to each other.

Microscopic Anatomy of Large Intestine

Simple columnar epithelium through entire large intestine (except anal canal, which has stratified squamous epithelium) 
No circular folds or villi 
Lamina propria and submucosa layers, large amounts of lymphatic tissue to guard against bacteria.

Intestinal Flora & Gas

Bacterial flora populate the large intestine, with 800+ species
Ferment cellulose and other undigested carbs resulting in the absorption of resulting sugars
Flatulence can often include gases from air, bacteria, or undigested material. 
Help in the synthesis of vitamins B & K.

Absorption and Motility 

Large Intestine (LI) takes 12-24 hours for reducing residue into feces.
Reabsorbs water and electrolytes (does not digest) 
Feces consists of 75% water and 25% solids: bacteria, fiber, fat, and mucous
Haustral Contractions(segmentation) every 30 minutes - distension of haustrum stimulates it to contract
Mass movements occur 1-3 times a day, triggered by gastrocolic and duodenocolic reflexes.

Defecation 

Stretching of rectum stimulates defecation reflex.  
Parasympathetic reflex involving the spinal cord - rectum stretching sends signals to the spinal cord, followed by pelvic nerves that send signals back intensifying peristalsis and relaxing the internal anal sphincter. The external anal sphincter must be relaxed for defecation.

Disorders of Large Intestine

Crohn's Disease: inflammation of parts of the small or large intestine caused by an inappropriate immune response. It is a chronic condition (inflammatory bowel disease or IBD), causing digestive upset, weight loss, and fever. 
Diverticulitis: Small pouches form in the lining of the intestine trapping food, leading to inflammation and pain. 
Colorectal cancer: common and deadly form of cancer which often starts as precancerous polyps. 
Associated factors include high animal fat diets.

Endocrine and ANS Control of Digestion

Three Overlapping phases: Cephalic, gastric, intestinal 
Cephalic Phase: Stimuli from food (smell, sight, taste) reach the cerebral cortex, hypothalamus, and brain stem - Brain stem signals to cranial nerves VII and IX, stimulating salivary glands, cranial nerve X stimulates gastric glands
Gastric Phase: Stretch receptors and chemoreceptors in stomach respond to food. - Parasympathetic and enteric neurons cause peristalsis. - Gastrin released by G cells, enters blood, comes back to stomach, signals release of gastric juice, and increases gastric motility 
Intestinal Phase: Slows chyme entering the small intestine. Stretch receptors cause enterogastric reflex- sends impulses to the medulla to inhibit parasympathetic stimulation for reduced gastric motility.  - Cholecystokinin (CCK) and secretin are secreted, enhancing pancreatic juice, bile release, and feelings of satiety. Secretin also produces bicarbonate-rich pancreatic juice and inhibits gastric juice.

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Test your knowledge on the human digestive system with this quiz. Questions cover the roles of various structures like the mesocolon, liver, and gastric cells, as well as the functions of different components in digestion and absorption. Perfect for students studying human anatomy and physiology.