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Flashcards in Digestive System Deck (229):

Alimentary Canal

  • AKA Gastrointestinal Tract (GI)
  • the muscular digestive tube that winds through the body
  • Organs:
    • mouth
    • pharynx
    • esophagus
    • stomach
    • small intestine
    • large intestine
    • anus


accesory digestive organs

  • teeth
  • tongue
  • gallbladder
  • salivary glands
  • liver (glands)
  • pancreas (glands)
    • glands secrete bile, saliva, and digestive enzymes to help breakdown foodstuffs


Digestive process

  1. Ingestion
  2. Propulsion
  3. Mechanical digestion
  4. Chemical Digestion
  5. Absorption
  6. Defecation



  • Step 1 of digestive process
  • the taking in of food into the mouth



  • step two of the digestive process
  • movement of food through the alimentary canal
  • includes:
    • swallowing (voluntary)
    • peristalsis (involuntary)



  • the major means of propulsion throughout the alimentary canal
  • involved alternate waves of contraction and relaxation of muscles in organ walls
  • squeezes food from one organ to the next 
  • mixes food


mechanical digestion

  • step 3 of the digestive process
  • physically prepares food for chemical digestion by enzymes
  • includes
    • chewing
    • churning of food in stomach
    • segmentation in small intestine



  • the rhythmic local constrictions of the intestine.
  • mixes food with digestive juices
  • increases the efficiency of nutrient absorption by repeatedly moving different parts of the food mass over the intestine wall 


chemical digestion

  • step 4 of the digestive process
  • a series of steps in which complex food molecules are broken down into their chemical building blocks.
    • Carbs/proteins/lipids-->simple sugars/amino acids/fatty acids/glycerol
  • carried out by enzymes secreted by digestive glands into the lumen of the alimentary canal



  • step 5 of the digestive process
  • the transport of digested end products from the lumen of the alimentary canal into the blood lymphatic capillaries located in the wall of the canal



  • step 6 of the digestive process
  • the elimination of indigestible substances from the body as feces



  • innermost layer of the alimentary canal
  • mucous membrane
  • contains three sublayers
    1. lining epithelium
    2. lamina propria
    3. muscularis mucosae


epithelial lining of mucosa of alimentary wall

  • exposed to the lumen of the alimentary canal
  • performs many functions related to digestion
    • absorbs nutrients
    • secretes mucus
  • continuous with ducts and secretory cells of various digestive glands (intrinsic glands)


lamina propria of mucosa of alimentary canal

  • loose areolar/reticular connective tissue
  • capillaries noruish the lining epithelium and absorb digested nutrients
  • contains most of the mucosa-associated lymphoid tissue (MALT)
    • defends against invasion by bacteria and other microorganisms in the alimentary canal


muscularis mucosae of mucosa of alimentary canal

  • external to lamina propria
  • thin layer of smooth muscles that produces local movements of the mucosa
  • ex:
    • the twitching of this muscle layer dislodges sharp food particles that become embedded in the mucosa


Submucosa of alimentary canal

  • external to mucosa layer
  • moderately dense connective tissue that contains:
    • major blood vessels
    • major lymphatic vessels
    • nerve fibers
  • sends branches of blood vessels to other two layers of the wall
  • elastic fibers enable alimentary canal to return to its shape after food passes through


muscularis externa of alimentary canal

  • external to submucosa
  • aka muscularis
  • consists of two layers of smooth muscle, responsible for peristalsis and segmentation:
    • inner circular layer:
      • fibers orient around the circumference of the canal
      • squeeze gut tube
      • thickens in some places to form sphincters that act as valves to prevent backflow of food from one organ to the net
    • outer longitudinal layer:
      • fibers orient along the length of the canal
      • shortens gut tube


Serosa of the alimentary wall

  • outermost layer of the intraperitoneal organs of the alimentary canal
  • the visceral peritoneum
  • simple squamous epithelium (mesothelium) with a layer of thin areolar connective tissue
  • parts of the canal not associated with the peritoneal cavity have adventitia instead of serosa


adventitia of alimentary canal

  • ordinary fibrous connective tissue
  • outer layer of wall in areas outside of peritoneal cavity
  • binds to other surrounding structures
  • esophagus in thorax
  • *retroperitoneal organs have serosa and adventitia


Myenteric Nerve Plexus

  • in the muscularis externa between the circular and longitudinal laters
  • innervates the muscularis externa to control peristalsis and segmentation


submucosal nerve plexus


  • lies within the submucosa, extends inward, and signals the glands in the mucosa to secrete and the muscularis mucosae to contract


enteric nervous system

  • the gut's own nervous system
  • consists of 100 million neurons (as many as the entire spinal cord)



  • the most extensive serous membrane 
  • found in the abdominalpelvic cavity


visceral peritoneum

  • covers the external surfaces of most digestive organs


parietal peritoneum

  • lines the body wall of the abdominopelvic cavity


peritoneal cavity

  • lies between visceral and parietal peritoneum
  • slitlike potential space between digestive organs and abdominal body wall
  • contains a lubricating serous fluid that allows organs to glide easily along each other during digestion



  • a double layer of peritoneum
  • two serous membranes fused back to back
  • extend to the digestive organs from the body wall
  • hold organs in place
  • sites of fat storage
  • provide a route for circulatory vessels and nerves to reach organs in the peritoneal cavity
  • some are called "ligaments" though they aren't the same fibrous ligaments that connect bones


dorsal mesenteries

  • most mesenteries
  • extend dorsally from the alimentary canal to the posterior abdominal wall


ventral mesenteries

  • in the superior abdomen
  • extends ventrally from the stomach and liver to the anterior abdominal wall


falciform ligament

  • a ventral mesentery
  • binds the anterior aspect of the liver to the anterior abdominal wall and diaphragm


lesser ormentum

  • a ventral mesentery
  • runs from the liver to the lesser curvature of the stomach and the beginning of the duodenum


greater ormentum

  • dorsal mesentery
  • connects the greater curvature of the stomach to the posterior wall--but in a roundabout way


mesentery proper

  • THE mesentery
  • fans inferiorly from the posterior abdominal wall like long, pleated curtains
  • support the jejunum and ileum


transverse mesocolon

  • mesentery of the colon
  • holds transverse colon to the posterior abdominal wall
  • a nearly horizontal sheet that is fused to the underside of the greater omentum.
  • can be viewed only inferiorly


sigmoid mesocolon

  • mesentery that connects the sigmoid colon to the posterior pelvic wall


secondarily retroperitoneal  organs

  • organs that begin with a mesentery but after development they end up fusing to the dorsal abdominal wall
  • lose mesentery and lodge behind the peritoneum
  • ie some parts of the intestine



or peritoneal organs

  • the digestive organs that keep their mesentery and remain surrounded by the peritoneal cavity
  • ie stomach




oral cavity

  • enterance of the alimentary canal
  • mucosa-lined cavity whose boundaries are the lips, cheeks, palate, and tongue.
  • posterior border is the fauces of the oropharynx


oral orifice

  • anterior opening of oral cavity/mouth


vestibule of mouth

  • porch
  • slit between the teeth and the cheeks


oral cavity proper

  • region of mouth the lies internal to the teeth


histology of mouth

  • internal mucosa made of epithelium and lamina propria
    • thick stratified squamous protects from abrasion by sharp food.
      • lining in tongue, palate, lips, and gums may show slight keratinization for extra protection
  • thin submucosa in some areas
  • external later of muscle and bone


labial frenulum

  • little bridle of the lip
  • median fold that connects to the internal aspect of each lip to the gum



  • forms the roof of the mouth
  • two distinct parts:
    • hard palate anteriorly
    • soft palate posteriorly


palatoglossal arches

  • the lateral anchors of the soft palate


palatopharyngeal arches

  • the anchoring of the softpalate to the oropharynx
  • boundary of fauces
  • pharyngeal tonsils protect nasopharynx from pathogens



  • occupies floor of mouth
  • a muscle constructed of interlacing fascicles of skeletal muscle fibers
  • grips, mixes food to form a bolus (lump)
  • moves posteriorly to push bolus into pharynx
  • helps form consonants in speech: (k,d,t,l)
  • houses most taste buds


intrinsic muscles of the tongue

  • confines within the tongue
  • not attached to bone
  • have fibers that run in several different planes
  • change shape of tongue, but not position
    • rolling tongue


extrinsic muscles of the tongue

  • extend to the tongue from bones of the skull and hyoid bone
  • alter the position of the tonge: portrude it, retract it, and move it laterally
  • ie genioglossus


lingual frenulum

  • a fold of mucosa on the undersurface of tongue
  • secures the tongue to the floor of the mouth
  • limts tongue's posterior movements
  • if abnormally short/extends far anteriorly are "tongue tied" and speech is distorted.



  • tongue tied
  • fused tongue
  • lingual frenulum is abnormally short or extends exceptionally far anteriorly
  • speech is distorted because movement of tongue is restricted
  • corrected by surgically snipping the frenulum


filiform papillae

  • conical, pointed, and keratinized
  • roughens the tongue
  • enables it to grasp and manipulate food during chewing
  • smallest and most numerous papillae
  • line up in parallell rows
  • give tongue whitish appearance


fungiform papillae

  • mushroom shaped
  • have vascular core that give them a red color
  • less abundant than filiform, but are scattered widely over the tongue surface
  • taste buds occur in the epithelium on the tops of these papillae


circumvallate papillae

  • 10-12
  • line up in a V-shaped row that is 2/3 of the way posteriorly on the tongue surface
  • directly anterior to the sulcus terminalis
  • each papilla is surrounded by a circular ridge from which it is separated by a deep furrow
  • taste buds occupy the epithelium on the sides of these papillae


lingual tonsil

  • posterior third of tongue which lies in oropharynx, not the mouth
  • covered with the bumpy lingual tonsil, not papillae



  • lie in alveoli sockets in the gum-covered margins of the mandible and maxilla


deciduous teeth

  • the primary dentition 
  • about 6 months after birth the lower central incisors are the first to appear
  • all 20 appear by about 2 years of age
  • fall out  between the ages of 6-12


permanent teeth

  • lie deep within gums
  • enlarge, develop, and erupt by the end of adolscence
    • except for the third molars (wisdom teeth)
      • emerge between 17-25
  • 32 permanent teeth in a full set
    • wisdom teeth dont fully develop or fail to erupt in some


impacted teeth

  • teeth that remain embedded deep in the jawbone and push on the roots of other teeth instead of emerging normally
  • cause pressure and pain
  • must be removed by a dentist or oral surgeon
  • Most common: Wisdom teeth



  • chisel shaped
  • for nipping off pieces of food



  • cone-shaped
  • aka cuspids/eye teeth
  • tear and pierce



  • bicuspids
  • broad crown with rounded cusps
  • for grinding



  • broad crowns with rounded cusps
  • for grinding
  • "millstone"


Dental formula for permanent dentition

2I, 1C, 2P, 3m   x2

2I, 1C, 2P, 3M       


=32 teeth


dental formula for deciduous teeth

2I, 1C, 2M    x2

2I, 1C, 2M        


=20 teeth


crown of tooth

the exposed portion of the tooth


root of tooth

portion of the tooth in the socket


neck of tooth

portion where crown and root meet near gumline



  • the surface of the crown which bears the forces of chewing
  • the hardest substance in the body
  • .96-1.6mm thick
  • lacks cells and vessels
  • 99% densely packed hydroxyapatite crystals arranged in force resisting rods/prisms




  • underlies the enamel cap 
  • forms the bulk of the tooth
  • bonelike tissue with mineral and collagen components
  • harder than bone
  • lacks internal blood vessels
  • contains dentinal tubes


dentinal tubules

  • radial striations in dentin


pulp cavity

  • in the center of the tooth
  • filled with pulp
  • contains the root canal



  • loose connective tissue 
  • contains tooth's vessels and nerves
  • supplies nutrients for the tooth's hard tissue
  • provides tooth sensation


Root canal


  • the part of the pulp cavity in the root


apical foramen

  • the opening into the root canal at the tip of each root


root canal therapy

  • needed when a tooth is damaged by a blow or by a deep cavity
    • pulp dies and becomes infected
  • all pulp is drilled out
  • pulp cavity is sterilized
  • filled with artificial, inert matierial before tooth is capped



  • calcified connective tissue
  • covers the external surface of the tooth root
  • essentially a bone layer
  • attaches the tooth to the periodontal ligament/periodontium


periodontal ligament

  • aka periodontum
  • "around the tooth"
  • anchors the tooth in the bony socket of the jaw
  • continuous with gum at the neck of the tooth



  • aka caries
  • "rottenness"
  • result from a gradual demineralization of the enamel and dentin 
  • caused by bacterial action/decay


dental plaque


  • a film of sugar, bacteria and other debris that adheres to teeth
  • accumulation begins the decay process
  • metabolism of trapped sugars by bacteria produces acids
  • acids dissolve the calcium salts from teeth
  • remaining organic matrix is broken down by protein-digesting bacterial enzymes



  • "stone"
  • calcified layer of plaque on gums
  • more plaque will accumulate on calculus layers, further inflaming gums



  • plaque accumulates around the neck of neck of teeth
  • bacteria in plaque releases toxins
  • gums become irritated and separate from teeth
  • calculus forms, on which more plaque forms
  • gums become more inflamed
  • can be reversed if calculus is removed




  • when calculus (gingivitis) is not removed
  • bacteria invade the periodontal tissues
  • pockets of infection destroy periodontal ligament
  • bone arround the tooth begins dissolving


  • begins around age 35
  • affects 75% of people
  • often results in loss of teeth--why people wear dentures


treating periodontitis

  • can be treated by 
    cleaning infected pockets around roots
  • cutting and stitching gums to shrink pockets
  • antibiotic gel injected into pockets to stimulate regeneration of gum, cementum, and periodontal ligament


salivary glands

  • produce saliva
    • mixture of water, ions, mucus and enzymes
  • compound tubuloalveolar glands



  • complex mixture of:
    • ions
    • water
    • mucus
    • enzymes
  • Function:
    • moistens mouth
    • dissolves food chemicals to be tasted
    • wets food
    • creates bolus
    • begin digestion of food carbs
    • helps neutralize acids involved in tooth decay
    • kills harmful oral microorganisms
    • stimulates growth of beneficial bacteria to outcompete harmful bacteria


intrinsic salivary glands

  • small glands
  • scattered within the mucosa of:
    • tongue
    • palate
    • lips
    • cheeks
  • saliva from these glands keep mouth moist at all times


extrinsic salivary glands

  • large glands
  • lie external to the mouth
  • connect to the mouth through ducts
  • only secrete saliva during/in anticipation of eating (mouth water)
  • paired extrinsic salivary glands:
    • parotid
    • submandibular
    • sublingual


parotid gland

  • largest extrinsic salivary gland
  • par-near otid-ear
  • lies anterior to the ear between the masseter muscle and the skin


parotid duct

  • runs parallel to the zygomatic arch
  • penetrates the muscle of the cheek
  • opens into the mouth lateral to the second upper molar

branches of the facial nerve run through this gland on their way to the muscles of facial expression. surgery on this gland can lead to facial paralysis



  • virus that spreads from one person to another through saliva
  • dominant symptom:
    • inflammation and swelling of parotid gland
      • opening mouth, chewing, movements of the mandible pull on the irritated parotid glands. Masseter compresses glands, causing pain.


submandibular gland

  • extrinsic salivary gland
  • size of a walnut
  • lies along the medial surface of the mandibular body
  • anterior to the angle of mandible
  • its duct raises the mucosa of the floor of the mouth and opens directly lateral to the tongue's lingual frenulum


sublingual gland

  • extrinsic salivary gland
  • lies in the floor of oral cavity
  • inferior to tongue
  • 10-12 ducts that open into the mouth directly superior to gland


Histology of pharyngeal wall

  • stratified squamous epithelia (oro/laryngopharynx)
    • protects against abrasion



  • muscular tube that propels swallowed food to stomach
  • lumen is collapsed when empty
  • begins as continuation of pharynx in midneck
  • descends through thorax on anterior surface of vertebral column
  • passes through diaphragm to abdomen and joins stomach


esophageal hiatus

  • opening in diaphragm through which esophagus travels to stomach
  • helps prevent regurgitation


cardiac orifice

  • where abdominal part of esophagus (2cm) joins the stomach


cardiac sphincter

  • closes of lumen of esophagus
  • prevents regurgitation of acidic stomach juices into esophagus


hiatal hernia

  • superior stomach pushes through an enlargened esophageal hiatus into thorax
  • follows a weakening of the diaphragmatic muscle fibers around the hiatus
  • cardiac sphincter no longer reinforced
  • acidic stomach juices persistently regurgitated
  • wall of the esophagus begins eroding
  • burning pain


gastroesophageal reflux disease

  • GERD
  • affects at least 4% of Americans
  • mostly due to abnormal relaxation or weakness of cardiac sphincter/esophageal hiatus
  • symptoms:
    • heartburn behind sternum
    • regurgitation of stomach contents
    • belching
  • If contents are aspirated, could lead to hoarseness, coughing, bronchial asthma


Barret's esophagus

  • persistent exposure to acidic stomach contents causes ulcers to develop on esophagus
  • epithelium becomes abnormal and precancerous
  • treatment is usually successful:
    • antacids
    • drugs that decrease the secretion of stomach acids
    • severe cases: surgery to reconstruct valve in lower esophagus


epithelial lining of esophagus

  • nonkeratinized stratified squamous epithelium (tough, thick)
  • at the junction of the esophagus and stomach, epithelium changes from thick epithelium to thin simple columnar epithelium specialized for secretion



  • j shaped
  • widest part of the alimentary canal
  • temporary storage tank 
  • food is churned and turned into paste (chyme)
  • breaks down food protein through pepsin secretion
  • water, electrolytes and some drugs (aspirin/alcohol) are absorbed
  • food remains in stomach for roughly 4 hours



  • churned food turned to paste
  • "juice"



  • a protein-digesting enzyme secreted in the stomach
  • functions only under acidic conditions
  • breaks down food protein


hydrochloric acid

  • A strong acid that destroys many harmful bacteria in food
  • helps breakdown food in stomach


cardiac region of stomach

  • aka cardia (near heart)
  • ring-shaped zone encircling the cardiac orifice at the junction with the esophagus



  • the stomach's dome
  • tucked under the diaphragm


the body of the stomach

  • large midportion
  • ends at the pyloric region
  • 3 layers of muscle:
    • longitudinal layer
    • circular layer
    • oblique layet


pyloric region of stomach

  • inferior to body
  • funnel-shaped
  • composed of the pyloric antrum and pyloric canal
  • ends at the pylorus


pylorus of stomach

  • "gate keeper"
  • the terminus of the stomach
  • contains the pyloric sphincter:
    • controls the entry of chyme into intestine


greater curvature of stomach

lesser curvature of stomach


  • convex left surface of the stomach


  • concave right margin



  • numerous longitudinal folds of mucosa
  • on the internal surface of the empty stomach
  • flatten as soon as the stomach fills
  • accomodates increasing quantities of food


Stomach capacity

  • holds 1.5 liters of food easily
  • has max capacity of 4 liters (1 gallon)


histology of stomach

  • lining epithelium is simple columnar
  • consists entirely of cells that secrete bicarbonate-buffered mucus
    • protects stomach wall from acid and pepsin


gastric pits

  • cup-shaped pits that line the surface of the stomach mucosa
  • millions of pits 
  • open into gastric glands


gastric glands

  • contain three types of secretory cells:
    1. mucous neck cells
    2. parietal (oxyntic) cells
    3. chief (zymogenic) cells


mucous neck cells

  • occur in upper ends/necks of gastric glands
  • secrete a different kind of mucous than surface cells
  • function of mucous is unknown


parietal cells

  • oxyntic cells
  • occur mainly in the middle regions of the glands
  • produce hydrochloric acid (HCl) by pumping hydrogen and chloride ions into the lumen of the gland
  • appear spherical when viewed by light microscopy
    • actually have three thick prongs like a pitchfork with microvilli
  • also secrete gastric intrinsic factor


gastric intrinsic factor

  • a protein secreted by parietal cells
  • necessary for the absorption of vitamin B12 by the small intestine
    • B12 helps create red blood cells


Chief Cells

  • zymogenic cells
  • mainly in the basal parts of the gastric glands
  • make and secrete pepsinogen
  • typical protein secreting cell
    • well developed rough ER
    • golgi apparatus
    • secretory granules in apical cytoplasm


Two other epithelial cells in gastric glands 

but also extend beyond these glands

  • enteroendocrine cells
    • ​release hormones like gastrin that signals the secretion of HCl
  • undifferentiated stem cells
    • ​divide continuously to replace lining epithelium of mucous secreting cells every 3-7 days


small intestine

  • longest part of the alimentary canal
  • site of most enzymatic digestion and absorption of nutrients
  • most digestive enzymes here are secreted by pancreas
  • during digestion, undergoes active segmentation movements
    • shuffles chyme back and forth
    • maximizes its contact with nutrient-absorbing mucosa
    • peristalsis propels chyme through small intestine in about 3-6 hours


Subdivisions of small intestine

  1. duodenum
    • "twelve finger widths long"
    • 5% of length
    • plicae circulares: microscopic folds in the small intestine which increase SA to enhance nutrient absorption
  2. jejunum
    • "empty"
    • 40% of length
  3. ileum
    • "twisted intestine"
    • 60% of length


Small intestine structural modifications for absorption

  1. Circular folds
  2. villi
  3. microvilli

these changes increase the intestinal surface area to about 200 square meters (the floor area of an average two story home)


circular folds of small intestine

  • aka plicae circulares
  • permanent transverse ridges of the mucosa and submucosa
  • nearly 1 cm tall
  • increases absorption surface area
  • force chyme to spiral through the lumen
    • slows movement of chyme 
    • allows time for complete absorption of nutrients


Villi of small intestine

  • fingerlike projections of the mucosa
  • simple columnar epithelium  made of absorptive cells
  • give it velvety texture
  • over 1mm high
  • can be seen with unaided eye
  • contain lacteal


absorptive cells

of villi

of small intestine

  • make up simple columnar epithelium
  • absorbs digested nutrients
  • aka enterocytes ("intestinal cells")



of villi

of small intestine

  • a wide lymphatic capillary within the core of lamina propria of the villa
  • receive the absorbed fats after digestion



of small intestine

  • located on the apical surface of the absorptive cells
  • exceptionally long and densely packed
  • aplifies absorptive surface
  • plasma membrane contains enzymes that complete the final stages of the breakdown of nutrient molecules


histology of small intestine wall

  1. Absorptive cells
  2. goblet cells
  3. enteroendocrine cells


absorptive cells

of wall 

of small intestine

  • contain mitochondria to supply energy for uptake of digested nutrients
  • contain abundant endoplasmic reticulum that assembles newly absorbed molecules


goblet cells 

of wall

of small intestine

  • secrete coat of mucus onto internal surface of intestine
    • lubricates the chyme
    • forms barrier that prevents enzymatic digestion of intestinal wall


enteroendocrine cells

  • secrete several hormones that signal:
    • the gallbladder to release stored bile
    • the pancreas to secrete digestive enzymes


intestinal glands

  • mucosa tubes between the villi
  • aka "crypts of lieberkuhn"
  • epithelia of these glands secrete intestinal juice that mixes with chyme


duodenal glands

of small intestine

  • in duodenum only
  • a set of tubular glands aka "Brunner's glands"
  • ducts open into intestinal glands
  • help neutralize the acidity of chyme from stomach
  • replace inner epithelium every 3-6 days
  • destroy bacteria


large intestine

  • the last major organ in the alimentary canal
  • material that reaches it is largely digested residue with few nutrients
  • remains here for 12-24 hrs
  • small amount of digestion is performed
  • Main function: absorb water and electrolytes from digested mass
  • 1.5 meters long


Mass peristaltic movements

of large intestine

  • the only strong propulsion of large intestine
  • pass over the colon a few times a day to force feces powerfully towards rectum


Subdivisions of large intestine

  • Cecum
  • vermiform
  • appendix
  • colon
  • rectum
  • anal canal


3 special features of large intestine

  1. teniae coli
  2. haustra
  3. epiploic appendages


teniae coli

  • ribbon of the colon
  • 3 longitudinal strips spaced at equal intervals around the circumfrence of the cecum and colon
  • the only thickenings of the longitudinal layer of the muscularis externa
  • maintain muscle tone
  • cause large intestine to pucker into sacs-haustra
  • helps move feces along



  • sacs in the large intestine
  • muscle tone of the teniae coli cause large intestine to pucker into these sacs


epiploic appendages

  • aka omental appendices
  • fat-filled pouches of visceral peritoneum that hang from the intestine
  • unknown significance



  • beginning of the large intestine
  • saclike pouch in the right iliac fossa


ileocecal valve

  • the opening of the ileum of the small intestine into the cecum's medial wall, surrounded internally by this. 
  • formed by two raised edges of the mucosa
  • sphincter in the distal ileum keeps valve closed until there is food in the stomach
    • sphincter then relaxes and opens valve
    • walls stretch as it fills and valve closes to prevent reflux of feces from cecum into ileum


vermiform appendix

  • worm-shaped
  • a blind tube that opens into the posteromedial wall of the cecum
  • usually illustrated as hanging inferiorly, it more often lies tucked up posterior to cecum in right iliac fossa
  • has large masses of lymphoid tissue in its walls and probably functions like tonsils
    • gathers antigens
    • neutralizes harmful pathogens
    • generates memory lymphocytes for long term immunity
    • this predisposes appendix to serious infection (like tonsils)



  • acute inflammation of the appendix
  • results from a blockage that traps infectious bacteria within its lumen
    • lump of feces
    • swelling of lymphoid tissue in wall of appendix
  • symptoms vary, difficult to diagnose
  • First symptom: pain in umbilical region
    • followed by
      • loss of appetite, fever, nausea, vomiting and relocalization of pain to lower right quadrant of abdominal surface


McBurney's Point

  • landmark used in assessing appendicitis


appendicitis stats

  • most often between ages of 15-25
  • affects 7% of people in US and Europe
  • immediate appendectomy is treatment


Ascending Colon

  • from cecum
  • ascends along the right side of the posterior abdominal wall in a secondarily retroperitoneal position
  • reaches the level of the right kidney


right colic feature

  • right angle turn of ascending colon
  • aka 'hepatic feature/flexure' because  liver lies directly superior to it


transverse colon

  • extends intraperitoneal to the left across the peritoneal cavity
  • from right colic feature
  • anterior to the spleen


left colic feature


  • aka splenic feature
  • acute downward bending of transverse colon
  • anterior to spleen


descending colon

  • following the left colic feature
  • descends along the left side of the posterior abdominal wall
  • in a secondarily retroperitoneal position


sigmoid colon

  • inferior to the descending colon
  • becomes intraperitoneal
  • enters true pelvis
  • s shaped (sigma=s in greek)



  • sacs that create herniations of the mucosa through colon wall
  • diet lacks fiber
  • most frequent in sigmoid colon
  • occurs in 30-40% of all americans over 50. 50% over 70
  • usually just leads to dull pain
    • could rupture artery and cause bleeding from anus
  • increased fiber can relieve symptoms



  • develops in 20% of diverticulosis patients 
  • diverticula become infected and perforate
  • feces leak into peritoneal cavity
  • affected region of colon may be removed and antibiotics perscribed



  • joined with sigmoid colon
  • descends along the inferior half of sacrum in secondarily retroperitoneal position
  • no teniae coli because longitudinal muscle is completely developed
    • to generate strong contractions for defecation
  • rectum means straight but has several tight bends


rectal valves

  • folds of the rectum
  • prevent feces from being passed along with flatus (gas)


anal canal

  • last subdivision of the large intestine
  • 3 cm long
  • lies entirely external to the abdominopelvic cavity in perneum


anal columns

  • longitudinal folds of mucosa
  • on superior half of anal canal, internally
  • contain the terminal portions of the superior rectal artery and vein (hemorrhoidal vessels)


anal valves

  • where neighboring anal columns join each other inferiorly at crescent-shaped transverse folds


anal sinuses

  • pockets just superior to these valves
  • release mucus when compressed by feces
    • provides lubrication in fecal passage during defecation


internal anal sphincter

  • smooth muscle
  • a thickening of the circular layer of muscularis
  • contracts involuntarily
  • prevents feces from leaking from anus
  • inhibit defecation during emotional stress


external anal sphincter

  • distinct skeletal muscle
  • contracts voluntarily
  • inhibits defecation
  • children learn to control this during toilet training



  • variscosities of the hemorrhoidal vein in the anal canal
  • result from straining to deliver baby or defecate
  • veins inflame, swell, throb and bulge into the lumen of anal canal
  • external: occur below pectinate line
    • itchier
    • more painful
  • internal: occur above pectinate line
    • tend to bleed
  • 75% of americans develop hemorroids at some point in their lives


hemorrhoid treatment

  • severe hemorrhoids are treated by thying them at base with small rubber bands
    • veins then wither and fall away
  • can be injected with hardening agent
  • can be exposed to electricity or infrared light to coagulate the blood


microscopic anatomy of large intestine

  • villi are absent
  • goblet cells are more abundant
    • more mucus eases passage of feces
  • in anal canal the simple columnar epithelium of alimentary canal changes to stratified squamous epithelium near pectinate line



  • largest gland in the body
  • weighs 1.4 kg (3lbs)
  • performs over 500 functions
  • digestive function is to produce/synthesize bile
  • also performs many metabolic functions


metabolic functions of liver

  • picks up glucose from nutrient rich blood returning from the alimentary canal and stores this carb as glycogen for use in body
  • processes fats and amino acids and stores certain vitamins
  • detoxifies many poisons and drugs in the blood
  • makes blood proteins



  • a green alkaline liquid
  • stored in the gallbladder and secreted into the duodenum
  • bile salts emulsify fats in small intestine
    • break up fatty nutrients into tiny particles
      • like detergent breaks up a pool of fat drippings in a roasted pan
  • makes blood proteins
  • detoxifies poisons



  • almost all metabolic functions of the liver carried out by this cell
  • AKA "liver cell"


Two surfaces of the liver

  • diaphramatic surface
    • faces anteriorly and superiorly
  • visceral surface
    • faces posteriorly


bare area of liver

  • the superior part of liver
  • fused to the diaphragm 
  • devoid of peritoneum


falciform ligament of liver

  • a vertical mesentery that binds the liver to the anterior abdominal wall


fissure of liver

  • a deep groove in the same sagittal plane as falciform ligament


Lobes of Liver

  • Right lobe
  • left lobe
    • two lobes once considered part of right lobe but discovered to share nerves and vessels with the left lobe. Visible on the visceral surface to the right of the fissure:
      • quadrate lobe
      • caudate lobe


porta hepatis

  • important area near the center of the visceral surface
  • gateway to the liver
  • where most major vessels and nerves enter and leave liver


hepatic portal vein

  • right and left branches
  • carry nutrient rich blood from stomach and intestines

  • enter porta hepatis


hepatic artery

  • right and left branches
  • carry oxygen-rich blood  to liver
  • enter porta hepatis


hepatic ducts

  • right and left
  • carry bile from respective liver lobes
  • exit from the porta hepatis
  • fuse to form the common hepatic duct


common hepatic duct

  • formed by fusion of left and right hepatic ducts
  • extends inferiorly toward duodenum


ligamentum teres

  • teres=round
  • AKA round ligament
  • cord-like ligament that ascends to the liver from navel
  • remnant of umbilical vein in fetus
  • within the inferior margin of the falciform ligament


ligamentum venosum

  • cordlike remnant of the ductus venosus of fetus
  • found in the superior half of the liver's fissure


liver lobules 

(microscopic anatomy of liver)

  • liver contains over a million
  • size of sesame seed
  • shaped like a hexagonal solid
  • consists of plates of hepatocytes (liver cells) radiating from a central vein


portal triad

(microscopic anatomy of liver)

  • found in almost every corner of a liver lobule
  • contains three main vessels
    • portal arteriole (branch of hepatic artery)
    • portal venule (branch of hepatic portal vein)
    • bile duct (carries bile away from liver lobules)


liver sinusoids

(microscopic anatomy of liver)

  • between the plates of hepatocytes
  • large capillaries
  • receive blood from portal arteriole/venule 
  • carry blood inward to reach central vein


kupffer cells

(microscopic anatomy of liver)

  • aka hepatic macrophages
  • in the walls of sinusoids
  • star-shaped
  • destroy bacteria and other foreign particles in the blood flowing past them
  • also destroy worn out blood cells


liver sinusoid histology

  • lined by leaky fenestrated endothelium
  • vast quantities of blood flow out, bathing hepatocytes with fluid


organelles and functions of hepatocytes:


  • Rough ER manufactures blood proteins
  • smoth ER helps produce bile salts/detoxifies posions in blood
  • peroxisomes detoxify other posions (alcohol)
  • large golgi apparatus packages the secretory products from ER
  • many mitochondria provide energy for all processes
  • many glycosomes store sugar


bile canaliculi

  • tiny intercellular spaces/channels
  • the 500-1000ml of bile produced each day is secreted and enters these canals
  • lie between adjacent hepatocytes



  • progressive inflammation of the liver
  • usually results from alcoholism. Sometimes hepatitis
  • liver's connective tissue regenerates faster than the hepatocytes 
  • liver becomes fibrous and fatty and function declines
  • patient may grow confused or comatose as toxins accumulate in the blood and depress brain functions



  • muscular sac
  • rests in the shallow depression on the visceral surface of the right lobe of the liver
  • stores and concentrates bile produced by liver
  • rounded head: fundus


cystic duct

of gallbladder

  • cyst=bladder
  • gallbladder's duct


bile duct

  • the cystic duct of the gall bladder joining with the common hepatic duct from the liver
  • empties into the duodenum


histology of the gallbladder

  1. mucosa consisting of simple columnar epithelium and lamina propria
    • concentrate bile by absorbing some of its water and ions
  2. a layer of smooth muscle
  3. a thick outer later of connective tissue that is covered by a serosa wherever it is not in direct contact with the liver



  • the crystalization of cholesterol in the gall bladder
  • caused by too much cholesterol or too few bile salts
  • can plug the cystic duct
  • causes pain when the gallbladder/ducts contract
  • show up well in ultrasound
  • treatment:
    • drugs that dissolve the stones
    • laparoscopic cholecystectomy'
      • minimally invasive surgery



  • "all meat"
  • shaped like a tadpole
  • lies in the epigastric and left hypochondriac regions of abdomen
  • exocrine gland
    • produces enzymes that digest foodstuffs in small intestine
  • endocrine gland:
    • produces hormones that regulate blood sugar levels


main pancreatic duct

  • extends through the length of the pancreas
  • joins the bile duct to form the hepatopancreatic ampulla
  • empties into duodenum at the major duodenal papilla


accessory pancreatic duct

  • lies in the head of pancreas
  • either drains to main duct or directly into duodenum


acinar cells of pancreas

  • housed in acinar glands
  • make, store, and secrete 22 kinds of pancreatic enzymes
  • capable of digesting various categories of foodstuffs


zymogen granules

  • intracellular secretory granules
  • stores enzymes in inactive form


pancreas in endocrine function

  • secretes insulin and glucagon
    • lower and raise blood sugar, respectively


pancreatic islets

  • aka islets of langerhans
  • spherical bodied, hormone secreting cell clusters
    • Secrete insulin and glucagon



  • inflammation of the pancreas
  • usually accompanied by necrosis of pancreatic tissue
  • caused by a blockage of the pancreatic duct
    • by gall stones or alcohlism-induced precipitation of protein
  • can lead to nutritional deficiencies, diabetes, pancreatic infections, and death due to circulatory shock


intestinal obstruction

  • any hindrance to the movement of chyme or feces through the intestine
  • mechanical (most)-due to hernias of the bowel or twists that pinch the bowel shut, intestinal tumors or adhesions, or foreign objects lodged in bowel
  • nonmechanical-due to halt in peristalsis
  • 85% of all obsctructions occur in small intestine
    • remainder affect large intestine
  • symptoms:
    • cramps
    • vomiting
    • nausea
    • failure to pass gass and feces


inflammatory bowel disease

  • affects 2 of every 1000 people 
  • noncontagious
  • periodic inflammation of the intestinal wall
  • chronic leukocyte infiltration of this wall
  • symptoms: cramping diarrhea, weight loss, and intestinal bleeding
  • Subtypes:
    • Crohn's disease (more serious): deep ulcers and fissueres along the whole intestine
    • Ulcerative colitis: shallow inflammation of large intestinal mucosa in rectum
  • Treatment: low in fiber/dairy diet, reduce stress, antibiotics,  and antiinflammatory/imunosupressant drugs


viral hepatitis

  • General term for any inflammation of liver.
  • largely viral in origin
  • lead to flulike symptoms and jaundice
    • yellow skin and mucous membranes-indication that liver is not removing bile pigments from blood to make bile
  • Major types are A, B, C, and G


hepatitis A

  • spread by the fecal-oral route
    • contaminated water
  • acute infection w/o long-term damage
  • recovery=lifelong immunity
  • treatment: 
    • antibodies
    • preventative vaccines


hepatitis B

  • transmitted via infected blood/body fluids or mother to child at birth
  • most recover and become immune
  • some develop chronic liver disease and eventually cirrhosis and increased likelyhood of developing cancer
  • can be helped with
    • inferon
      • substance that enhance the immune response against viruses
    • combo of drugs that stop viral replication
    • vaccine


hepatitis C

  • transmitted via body fluids
  • can lead to cirrhosis and liver cancer
  • usually produces no short-term symptoms
  • 4 mil americans have it
  • its spread is a serious health concern
  • no vaccine exists
  • treatment:
    • inferon
    • drug that inhibits viral replication can help


hepatitis G

  • as widespread as C but causes little liver damage


  • Flat embryo folds into cylinder, producing primitive gut
  • primitive gut open to yolk sac through vitelline duct


Vitelline Duct

Embryonic Development of Alimentary Canal

  • duct through which primitive gut opens into yolk sac
  • splits gut into three regions (supplied by celiac, superior mesenteric, and inferior mesenteric arteries, respectively): 
    • foregut (superior to duct)
    • midgut (open to the duct)
    • hindgut (inferior to duct)



Embryonic Development of Alimentary Canal

  • superior to vitelline duct
  • develops into first segment of digestive system
  • from pharynx to point in duodenum where bile duct enters



Embryonic Development of Alimentary Canal

  • opens to duodenum duct
  • develops from duodenum to 2/3 of the way along transverse colon



Embryonic Development of Alimentary Canal

  • forms the rest of the large intestine



Embryonic Development of Alimentary Canal

  • a tubelike outpocketing
  • the caudal part of the early hindgut joins this



  • "sewer"
  • the expanded junction between the hindgut and the allantois
  • gives rise to the rectum and most of the anal canal


oral membrane 

Embryonic Development of Alimentary Canal

  • endoderm lined gut touches the surface ectoderm 
  • lies in depression called stomodeum (on the way to becoming mouth)


Cloacal membrane

Embryonic Development of Alimentary Canal

  • end of hindgut, endoderm meets ectoderm to form this
  • in a pit called poctodeum (on the way to becoming anus)


Meckel's Diverticulum

  • failure of the vitelline duct to close completely
  • results in outpocketing of the ileum
  • the most common developmental abnormality of digestive system (2% of population)
  • often asymptomatic
  • ulceration or bleeding may occur



  • abnormal rotation during development that causes the intestine to twist around itself
  • can disrupt blood supply to the intestine
  • can lead to death of tissue in affected portion
  • can cause intestinal blockage
  • Treatment:
    • surgical removal of affected portion of gut



  • an inflammation of the alimentary canal
  • caused by contaminated food
  • symptoms: nausea, vomiting, cramps, loss of apetite or diarrhea


divisions of the anterior abdominal wall


Peptic Ulcers

  • crater-like erosion of the mucosa of any part of the alimentary canal exposed to stomach secretions
  • mostly in stomach and duodenum



  • c shaped superior portion of the small intestine that receives bile from gall bladder and digestive enzymes from pancreas
  • 12 inches
  • plicae circulares



  • the middle portion of small intestine
  • larger lumen
  • increased number of plicae circulares
  • 8 feet



  • terminal portion of small intestine
  • contains numerous lymphatics in the walls
  • 12 feet