23 PART 1

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23 PART 1

• The Digestive System

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Overview of the Digestive System

• Organs are divided into two groups
• Alimentary canal
• Mouth, pharynx, and esophagus
• Stomach, small intestine, and large intestine
• Accessory digestive organs
• Teeth and tongue
• Gallbladder, salivary glands, liver, and pancreas
• Accessory organs are connected to the alimentary
  canal by ducts
• Secretions contribute to breakdown of foodstuffs

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Figure 23.1 The alimentary canal and the
accessory digestive organs.
Mouth (oral cavity)
Parotid gland
Sublingual gland
Salivary glands
Tongue
Submandibulargland
Pharynx
Esophagus
Stomach
Pancreas
(Spleen)
Liver
Gallbladder
Transversecolon
Descendingcolon
Duodenum
Jejunum
Smallintestine
Ascendingcolon
Ileum
Large intestine
Cecum
Sigmoid colon
Rectum
Appendix
Anus
Anal canal
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Digestive Processes

• Ingestionoccurs in the mouth
• Propulsionmovement of food
• Peristalsismajor means of propulsion
• Mechanical breakdownprepares food for chemical
  digestion
• Chewing, churning food in stomach, segmentation
• Segmentation is rhythmic local constrictions of
  intestine

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Digestive Processes

• Chemical digestioncomplex molecules broken down
  to chemical components
• Mouth
• Stomach
• Small intestine
• Absorptiontransport of digested nutrients
• Defecationelimination of indigestible substances
  as feces

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Figure 23.5 Activities of the gastrointestinal
tract.
Ingestion
Food
Mechanicalbreakdown
Pharynx
Esophagus

• Chewing (mouth)
• Churning (stomach)
• Segmentation(small intestine)

Propulsion

• Swallowing(oropharynx)
• Peristalsis(esophagus,stomach,small
  intestine,large intestine)

Digestion
Stomach
Absorption
Lymphvessel
Smallintestine
Bloodvessel
Largeintestine
Mainly H2O
Feces
Anus
Defecation
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Peristalsis

• Major means of propulsion
• Adjacent segments of the alimentary canal relax
  and contract

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Figure 23.6a Peristalsis and segmentation.
From mouth
Peristalsis Adjacent segmentsof alimentary
tract organsalternately contract and
relax,moving food along the tractdistally.
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Segmentation

• Rhythmic local contractions of the intestine
• Mixes food with digestive juices

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Figure 23.6b Peristalsis and segmentation.
Segmentation Nonadjacentsegments of alimentary
tractorgans alternately contract andrelax,
moving the food forwardthen backward. Food is
mixedand slowly propelled.
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Figure 23.3 Peritoneum and the Digestive System
Organs (1 of 2)
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Figure 23.3 Peritoneum and the Digestive System
Organs (2 of 2)
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The Peritoneal Cavity and Peritoneum

• Peritoneuma serous membrane
• Visceral peritoneumsurrounds digestive organs
• Parietal peritoneumlines the body wall
• Peritoneal cavitya slitlike potential space

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The Peritoneal Cavity and Peritoneum

• Mesenterya double layer of peritoneum
• Holds organs in place
• Sites of fat storage
• Provides a route for circulatory vessels and
  nerves

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The Peritoneal Cavity and Peritoneum

• Ventral mesenteries
• Falciform ligament
• Binds anterior part of liver to anterior
  abdominal wall
• Lesser omentum
• Attaches liver to the lesser curvature of stomach

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The Peritoneal Cavity and Peritoneum

• Dorsal mesenteries
• Greater omentum
• Connects greater curvature of stomach to
  posterior abdominal wall
• A fatty apron
• Transverse mesocolon
• Holds transverse colon in place
• Sigmoid mesocolon
• Connects the sigmoid colon to posterior pelvic
  wall

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Figure 23.4a The mesenteries.
Falciform ligament
Liver
Gallbladder
Spleen
Stomach
Ligamentum teres
Greater omentum
Small intestine
Cecum
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Figure 23.4b The mesenteries.
Liver
Gallbladder
Lesser omentum
Stomach
Duodenum
Transverse colon
Small intestine
Cecum
Urinary bladder
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Figure 23.4c The mesenteries.
Greater omentum
Transverse colon
Transversemesocolon
Descending colon
Mesentery
Sigmoidmesocolon
Jejunum
Sigmoid colon
Ileum
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Figure 23.4d The mesenteries.
Ligamentum teres
Gallbladder
Lesser omentum
Spleen
Liver
Gastrosplenic ligament
Transversemesocolon
Pancreas
Stomach, pyloric part
Duodenum,superior part
Transverse colon
Duodenojejunal flexure
Duodenum,horizontal part
Greater omentum
Descending colon
Ascending colon
Mesentery (cut)
Sigmoidmesocolon
Rectum
Ileum
Cecum
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The Peritoneal Cavity and Peritoneum

• Retroperitoneal organs
• Behind the peritoneum
• Peritoneal organs
• Digestive organs that keep their mesentery

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Secondarily Retroperitoneal Organs

• Initially formed within peritoneum
• Become retroperitoneal
• Fuse to posterior abdominal wall

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Table 23.1 Summary of Intraperitoneal and
Secondarily Retroperitoneal Digestive Organs in
the Abdomen and Pelvis
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Histology of the Alimentary Canal Wall

• Same four layers from esophagus to anus
• The mucosainnermost layer
• Consists of
• Epithelium
• Lamina propria
• Muscularis mucosae
• The submucosaexternal to the mucosa
• Contains blood and lymphatic vessels, nerve fibers

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Histology of the Alimentary Canal Wall

• The muscularis externaexternal to the submucosa
• Two layers
• Circular muscularisinner layer
• Longitudinal muscularisouter layer
• The serosathe outermost layer
• Is the visceral peritoneum

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Figure 23.7a Histological layers of the
alimentary canal.
Intrinsic nerve plexuses
Myenteric nerve plexus
Submucosal nerve plexus
Glands in submucosa
Mucosa
Epithelium
Lamina propria
Muscularis mucosae
Submucosa
Muscularis externa
Circular layer
Longitudinal layer
Serosa
Epithelium
Connective tissue
Nerve
Lumen
Gland in mucosa
Artery
Vein
Duct of gland outsidealimentary canal
Mucosa associatedlymphoid tissue
Lymphatic vessel
Mesentery
Longitudinal and cross-sectional views through
the small intestine
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Figure 23.7b Histological layers of the
alimentary canal.
Mucosa
Submucosa
Muscularis externa
Serosa
Light micrograph cross section through the small
intestine (85?)
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Smooth Muscle

• Primarily found in walls of viscera
• Fibers elongated
• Have one centrally located nucleus
• Grouped into sheets
• Longitudinal layerparallel to long axis of organ
• Circular layerdeeper layer, fibers run around
  circumference of organ

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Figure 23.8 Arrangement of smooth muscle in the
walls of hollow organs.
Longitudinal layer ofsmooth muscle (showssmooth
muscle fibers incross section, 215?)
Small intestine
Mucosa
Circular layer of smoothmuscle (shows
longitudinalviews of smooth musclefibers, 215?)
Location and plane ofsection shown in (b)
Cross section of the intestineshowing the smooth
musclelayers (one circular and theother
longitudinal) running atright angles to each
other
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Innervation of Smooth Muscle

• Innervated by ANS
• Few fibers per sheet innervated
• Sheet of smooth muscle contracts as a unit
• Called single-unit innervation
• Multiunit innervation
• Each smooth muscle cell innervated
• Iris of eye and arrector pili muscles

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Figure 23.10 Innervation of smooth muscle.
Varicosities
Autonomicnerve fibersinnervatemost
smoothmuscle fibers.
Smoothmusclecell
Varicosities releasetheir neurotransmittersinto
a wide synapticcleft (a diffuse junction).
Synapticvesicles
Mitochondrion
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Nerve Plexuses

• Myenteric nerve plexus
• Lies between circular and longitudinal muscularis
• Controls peristalsis and segmentation
• Submucosal nerve plexus
• Lies in submucosa
• Signals glands to secrete
• Innervation
• Sympathetic and parasympathetic motor fibers
• Visceral sensory fibers

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The Mouth and Associated Organs

• Mouth (oral cavity) Go to Picture
• Mucosa-lined cavity
• Boundaries are
• Lips anteriorly
• Cheeks laterally
• Palate superiorly
• Tongue inferiorly
• Fauces of oropharynx posteriorly

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The Mouth and Associated Organs

• The mouthoral cavity
• Mucosal layer
• Stratified squamous epithelium
• Lamina propria
• The lips and cheeks
• Formed from orbicularis oris and buccinator
  muscles, respectively

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Figure 23.11a Anatomy of the mouth.
Soft palate
Palatoglossal arch
Uvula
Hard palate
Oral cavity
Palatinetonsil
Tongue
Oropharynx
Lingual tonsil
Epiglottis
Hyoid bone
Laryngopharynx
Esophagus
Trachea
Sagittal section of the oral cavity and pharynx
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Anatomy of the Mouth

• The labial frenulum
• Connects lips to gum
• The palate
• Forms the roof of the mouth
• Boundaries of the fauces
• Palatoglossal arches
• Palatopharyngeal arches

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Figure 23.11b Anatomy of the mouth.
Gingivae(gums)
Upper lip
Superior labialfrenulum
Palatineraphe
Palatoglossalarch
Hard palate
Soft palate
Palatopharyngealarch
Uvula
Posterior wallof oropharynx
Palatinetonsil
Tongue
Sublingualfold withopenings ofsublingual ducts
Lingual frenulum
Opening ofsubmandicularduct
Oral vestibule
Gingivae (gums)
Lower lip
Inferior labialfrenulum
Anterior view
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The Tongue

• Interlacing fascicles of skeletal muscle
• Grips food and repositions it
• Helps form some consonants
• Intrinsic muscleswithin the tongue
• Extrinsic musclesexternal to the tongue
• Lingual frenulum
• Secures tongue to floor of mouth

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The Superior Surface of the Tongue

• Tongue papillae
• Filiform papillaeno taste buds
• Fungiform papillae
• Vallate papillae
• Sulcus terminalis
• Marks border between mouth and pharynx
• Posterior one-third of tongue lies in oropharynx
• Lined with lingual tonsil

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Figure 23.12 The dorsal surface of the tongue.
Epiglottis
Palatopharyngealarch
Palatine tonsil
Lingual tonsil
Palatoglossalarch
Terminal sulcus
Foliate papillae
Vallate papilla
Medial sulcusof the tongue
Dorsum of tongue
Fungiform papilla
Filiform papilla
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Figure 23.14 Longitudinal section of a canine
tooth within its bony tooth socket.
Enamel
Dentin
Crown
Dentinal tubules
Pulp cavity (containsblood vesselsand nerves)
Neck
Gingival sulcus
Gingiva (gum)
Cement
Root canal
Root
Periodontalligament
Apical foramen
Bone
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The Salivary Glands

• Produce saliva
• Compound tubuloalveolar glands
• Parotid glands
• Parotid ductparallel to zygomatic arch
• Contain only serous cells
• Submandibular glands
• Lie along medial surface of mandible
• Sublingual glands
• Lie in floor of oral cavity
• Contain primarily mucous cells

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Figure 23.15 The major salivary glands.
Tongue
Teeth
Parotidgland
Ducts ofsublingualgland
Parotid duct
Masseter muscle
Frenulumof tongue
Body of mandible(cut)
Sublingualgland
Posterior belly ofdigastric muscle
Mylohyoidmuscle (cut)
Submandibularduct
Anterior belly ofdigastric muscle
Serous cellsformingdemilunes
Mucous cells
Submandibulargland
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The Pharynx

• Oropharynx and laryngopharynx
• Passages for air and food
• Lined with stratified squamous epithelium
• External muscle layer
• Consists of superior, middle, and inferior
  pharyngeal constrictors

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The Esophagus

• Gross anatomymuscular tube
• Begins as a continuation of the pharynx
• Joins the stomach inferior to the diaphragm
• Cardiac sphinctercloses lumen to prevent stomach
  acid from entering esophagus

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The Esophagus

• Microscopic anatomy
• Epithelium is stratified squamous epithelium
• When empty, mucosa and submucosa are in
  longitudinal folds
• Mucous glandsprimarily compound tubuloalveolar
  glands

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The Esophagus

• Muscularis externa
• Skeletal muscle
• First one-third of length
• Mixture of skeletal and smooth muscle
• Middle one-third of length
• Smooth muscle
• Inferior one-third of length
• Adventitia
• Most external layer of esophagus

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Figure 23.16 Microscopic structure of the
esophagus.
Mucosa(stratified squamousepithelium)
Esophagus-stomachjunction
Submucosa (areolar connective tissue)
Lumen
Muscularis externa
Simple columnarepithelium ofstomach
Circular layer
Longitudinal layer
Adventitia (fibrousconnective tissue)
Cross section throughesophagus (3?)
Esophagus-stomach junction,longitudinal section
(85?)
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The Stomach

• Site where food is churned into chyme
• Secretion of pepsin begins protein digestion
• Functions under acidic conditions
• Food remains in stomach approximately 4 hours
• Regions of the stomach
• Cardial part
• Fundus
• Body
• Pyloric part

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Figure 23.17a Gross anatomy of the stomach.
Cardia
Fundus
Esophagus
Muscularis externa
Serosa
Longitudinal layer
Circular layer
Body
Oblique layer
Lumen
Lessercurvature
Rugae ofmucosa
Greatercurvature
Pyloricantrum
Pyloriccanal
Pyloric sphincter(valve) at pylorus
Duodenum
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Figure 23.17b Gross anatomy of the stomach.
Fundus
Liver(cut)
Body
Spleen
Lessercurvature
Greatercurvature
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Microscopic Anatomy of the Stomach

• Muscularis has three layers
• Circular and longitudinal layers and oblique
  layer
• Epithelium is simple columnar epithelium
• Mucosa dotted with gastric pits
• Gastric glandsdeep to gastric pits

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Microscopic Anatomy of the Stomach

• Gastric glands of fundus and body
• Mucous neck cells
• Secrete a special mucus
• Parietal (oxyntic) cells
• Secrete hydrochloric acid and gastric intrinsic
  factor
• Chief (zymogenic) cells
• Secrete pepsinogen
• Pepsinogen is activated to pepsin when it
  encounters acid in the gastric glands

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Figure 23.18 Microscopic anatomy of the stomach.
Gastric pits
Surface epithelium(mucous cells)
Gastricpit
Surfaceepithelium
Mucous neck cells
Parietal cell
Gastricgland
Mucosa
Lamina propria
Chief cell
Muscularismucosae
Submucosa(containssubmucosalplexus)
Obliquelayer
Enteroendocrine cell
Pepsinogen
Pepsin
HCl
Enlarged view ofgastric pits andgastric glands
Circularlayer
Muscularisexterna(containsmyentericplexus)
Longitudinallayer
Mitochondria
Parietal cell
Stomach wall
Serosa
Layers of the stomach wall, longitudinal section
Chief cell
Mucus-secretingcells
Gastric pits
Enteroendocrinecell
Surface mucous cell
Mucous neck cells
Location of the HCl-producing parietalcells and
pepsin-secreting chief cells ina gastric gland
HCl-secreting parietal cells
Gastricgland
Enzyme-secreting chief cells
Muscularismucosae
Micrograph of the stomach mucosa, view similar to
part (b) (110?)
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The Small IntestineGross Anatomy

• Longest portion of the alimentary canal
• Site of most enzymatic digestion and absorption
• Three subdivisions
• Duodenum
• Jejunum
• Ileum
• Innervation
• Parasympathetic fibers from vagus nerve
• Sympathetic from thoracic splanchnic nerves

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The Duodenum

• Receives digestive enzymes and bile
• Main pancreatic duct and common bile duct enter
  duodenum
• Sphincters control entry of bile and pancreatic
  juices

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Figure 23.19 The duodenum of the small
intestine, and related organs.
Right and left hepaticducts of liver
Common hepatic duct
Cystic duct
Bile duct and sphincter
Accessory pancreatic duct
Mucosawith folds
Tail of pancreas
Pancreas
Gallbladder
Jejunum
Major duodenalpapilla
Main pancreatic duct and sphincter
Hepatopancreaticampulla and sphincter
Duodenum
Head of pancreas
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The Small IntestineMicroscopic Anatomy

• Modifications for absorption
• Circular folds
• Transverse ridges of mucosa and submucosa
• Villi
• Fingerlike projections of the mucosa
• Covered with simple columnar epithelium
• Microvilli
• Further increase surface area for absorption

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Histology of the Intestinal Wall

• Absorptive enterocytes
• Uptake digested nutrients
• Goblet cells
• Secrete mucus that lubricates chyme
• Enteroendocrine cells
• Secrete hormones
• Intestinal crypts
• Epithelial cells secrete intestinal juice

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Figure 23.20 Structural modifications of the
small intestine that increase the surface area
for digestion and absorption.
Vein carryingblood tohepatic portalvessel
Musclelayers
Lumen
Circularfolds
Villi
Microvilli(brush border)
Absorptive enterocytes
Absorptiveenterocytes
Gobletcells
Lacteal
Villi
Goblet cell
Vilus
Bloodcapillaries
Mucosaassociatedlymphoidtissue
Enteroendocrinecells
Intestinalcrypt
Venule
Muscularismucosae
Lymphatic vessel
Duodenalgland
Submucosa
Intestinal crypt
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The Large Intestine

• Digested residue contains few nutrients
• Small amount of digestion by bacteria
• Main functions
• Absorb water and electrolytes
• Mass peristaltic movements force feces toward the
  rectum

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Gross Anatomy of Large Intestine

• Subdivided into
• Cecum, appendix, colon, rectum, anal canal
• Special features of large intestine
• Teniae coli
• Thickening of longitudinal muscularis
• Haustra
• Puckering created by teniae coli
• Epiploic appendages
• Fat-filled pouches of visceral peritoneum

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Gross Anatomy of Large Intestine

• Cecum
• Blind pouch
• Beginning of large intestine
• Appendix
• Contains lymphoid tissue
• Neutralizes pathogens
• Colon
• Divided into distinct segments
• Ascending, transverse, descending, and sigmoid
  colon

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Gross Anatomy of Large Intestine

• Rectum
• Descends along the inferior half of the sacrum
• Anal canal
• The last subdivision of the large intestine
• Lined with stratified squamous epithelium

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Figure 23.21a Gross anatomy of the large
intestine.
Left colic(splenic) flexure
Transverse mesocolon
Right colic(hepatic) flexure
Epiploic appendages
Transverse colon
Superiormesenteric artery
Descending colon
Haustrum
Ascending colon
Cut edge of mesentery
Ileum
Ileocecal valve
Teniae coli
Sigmoid colon
Cecum
Rectum
Appendix
Anal canal
External anal sphincter
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Figure 23.21b Gross anatomy of the large
intestine.
Rectal valve
Rectum
Hemorrhoidalveins
Levator ani muscle
Anal canal
Anal columns
External analsphincter
Internal analsphincter
Anal valves
Pectinate line
Anal sinuses
Anus
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Vessels and Nerves of the Large Intestine

• First half of large intestine
• Arterial supplysuperior mesenteric artery
• Innervation
• Sympathetic innervationsuperior mesenteric and
  celiac ganglia
• Parasympathetic innervationvagus nerve

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Vessels and Nerves of the Large Intestine

• Distal half of large intestine
• Arterial supplyinferior mesenteric artery
• Innervation
• Sympathetic innervationinferior mesenteric and
  hypogastric plexuses
• Parasympathetic innervationpelvic splanchnic
  nerves

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Figure 23.22 Defecation reflex. (1 of 2)
Impulses fromcerebral cortex(consciouscontrol)
Sensory nerve fibers
Feces move into and distendthe rectum,
stimulating stretchreceptors there. The
receptorstransmit signals along afferentfibers
to spinal cord neurons.
Voluntary motornerve to externalanal sphincter
Sigmoid colon
Stretch receptors in wall
A spinal reflex is initiated in
whichparasympathetic motor (efferent)
fibersstimulate contraction of the rectal walls
andrelaxation of the internal anal sphincter.
Rectum
Involuntary motor nerve(parasympathetic division)
External analsphincter(skeletal muscle)
Internal anal sphincter(smooth muscle)
If it is convenient to defecate,voluntary
motor neurons areinhibited, allowing the
externalanal sphincter to relax so thatfeces
may pass.
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Microscopic Anatomy of Large Intestine

• Villi are absent
• Contains numerous goblet cells
• Intestinal cryptssimple tubular glands
• Lined with simple columnar epithelial tissue
• Epithelium changes at anal canal
• Becomes stratified squamous epithelium

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Figure 23.23 The mucosa of the large intestine.
Colonocytes
Goblet cells
Lamina propria
Intestinal crypt
Muscularismucosae
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Figure 23.24 Digestive Processes and Histology
of the Alimentary Canal (1 of 2)
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Figure 23.24 Digestive Processes and Histology
of the Alimentary Canal (2 of 2)
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The Liver

• Largest gland in the body
• Performs over 500 functions
• Digestive function
• Bile production
• Performs many metabolic functions

76
Figure 23.25 Anterior view of the liver.
Sternum
Nipple
Bare area
Liver
Falciformligament
Right lobeof liver
Left lobe of liver
Roundligament(ligamentumteres)
Gallbladder
77
Figure 23.26a Visceral surface of the liver
(posteroinferior view).
Lesser omentum(in fissure)
Bare area
Caudate lobeof liver
Sulcus for inferiorvena cava
Left lobe of liver
Porta hepatiscontaining hepaticartery (left)
andhepatic portal vein(right)
Hepatic vein (cut)
Bile duct (cut)
Quadrate lobeof liver
Right lobe of liver
Gallbladder
Ligamentum teres
78
Figure 23.26b Visceral surface of the liver
(posteroinferior view).
Hepatic veins
Hepatic portal vein
Inferior venacava
Caudate lobe
Bare area
Left lobe
Ligamentumvenosum infissure
Right hepaticartery
Porta hepatis
Right hepaticduct
Left hepatic artery
Left hepatic duct
Cystic duct
Common hepatic duct
Gallbladder
Fissure
Right lobe
Falciform ligament
Quadratelobe
Ligamentum teres
79
Microscopic Anatomy of the Liver

• Hepatocytefunctional cells of the liver
• Portal triad composed of
• Bile duct tributary
• Branch of hepatic portal vein
• Branch of hepatic artery
• Hepatic macrophagesdestroy bacteria

80
Microscopic Anatomy of the Liver

• Some functions of hepatocytes
• Rough ER manufactures blood proteins
• Smooth ER produces bile salts, detoxifies poisons
• Peroxisomes detoxify poisons (alcohol)
• Golgi apparatus packages secretory products
• Mitochondria provide energy for liver processes
• Glycosomes store sugar
• Great capacity for regeneration

81
Figure 23.27 Microscopic anatomy of the liver.
Lobule
Centralvein
Connectivetissue septum
Interlobular veins(to hepatic vein)
Central vein
Sinusoids
Bile canaliculi
Plates ofhepatocytes
Bile duct (receivesbile from bilecanaliculi)
Fenestratedlining (endothelialcells) of
sinusoids
Bile duct
Portal triad
Portal venule
Stellate macrophagesin sinusoid walls
Portal arteriole
Portal vein
82
The Gallbladder

• Stores and concentrates bile
• Expels bile into duodenum
• Bile emulsifies fats
• Cholecystokininreleased from enteroendocrine
  cells in response to fatty chyme

83
Figure 23.19 The duodenum of the small
intestine, and related organs.
Right and left hepaticducts of liver
Common hepatic duct
Cystic duct
Bile duct and sphincter
Accessory pancreatic duct
Mucosawith folds
Tail of pancreas
Pancreas
Gallbladder
Jejunum
Major duodenalpapilla
Main pancreatic duct and sphincter
Hepatopancreaticampulla and sphincter
Duodenum
Head of pancreas
84
The Pancreas

• Has both exocrine and endocrine functions
• Endocrine function
• Produces insulin and glucagon
• Regulates blood sugar
• Exocrine function
• Produces most enzymes that digest food in the
  small intestine

85
The Pancreas

• Is secondarily retroperitoneal
• Main pancreatic duct
• Extends the length of the pancreas
• Joins bile duct to form the hepatopancreatic
  ampulla
• Empties into duodenum
• Arterial supply is from hepatic, splenic, and
  superior mesenteric arteries

86
Figure 23.28 The gross and microscopic anatomy
of the pancreas.
Small duct
Diaphragm
Acinar cell
Liver
Basementmembrane
Spleen
Zymogengranules
Pancreas
Tail
Roughendoplasmicreticulum
Body
Ductcell
Head
One acinus
Illustration of the pancreaticacinar cells
Duodenum
Dissection illustrating the pancreas andits
relationship to surrounding organs inthe
superior abdomen
Acinar cells
Pancreaticduct
Photomicrograph of the exocrineacinar cells of
the pancreas (130?)
87
The Pancreas

• Exocrine function
• Acinar cells make, store, and secrete pancreatic
  enzymes
• Enzymes are activated in the duodenum

88
Peptic Ulcers

• Are erosions of the mucosa of a region of the
  alimentary canal
• Gastric ulcers
• Occur in pyloric region of the stomach
• Duodenal ulcers
• Occur in duodenum of the small intestine

89
Peptic Ulcers

• Caused by Helicobacter pylori
• H. pylori
• Acid-resistant
• Binds to gastric epithelium
• Induces oversecretion of acid and inflammation

90
Figure 23.29 Peptic ulcers.
A gastric ulcer lesion
Bacteria
Mucosalayer ofstomach
H. pylori bacteria
91
Disorders of the Digestive System

• Intestinal obstruction
• Mechanical obstructions
• Adhesions, tumors, or foreign objects
• Nonmechanical obstruction
• Halt in peristalsis
• Trauma
• Intestines touched during surgery

92
Disorders of the Digestive System

• Inflammatory bowel disease
• Inflammation of intestinal wall
• Crohns disease
• Ulcerative colitis
• Viral hepatitis
• Jaundice and flulike symptoms
• Major typesA, B, C, and G

93
Disorders of the Digestive System

• Cystic fibrosis and the pancreas
• Pancreatic ducts become blocked with mucus
• Clogged ducts prevent pancreatic juices from
  entering small intestine
• Leads to malabsorption of fats and other nutrients

94
The Digestive System in Later Life

• Middle age
• Gallstones and ulcers
• Old age
• Activity of digestive organs declines
• Fewer digestive juices and enzymes are produced
• Absorption is less efficient
• Dehydration of fecal mass leads to constipation
• Diverticulosis and cancer of digestive organs