Download Ch23.Digestive.System_1

Topics for Student Presentations
Presentations in lab on Mon, May 13; ~5-6 min, any style!
2-5 people per group
 Anatomy & Physiology (or Pathophysiology) of:
•Heart Disease
•Cleft Palate
•AIDS
•Leukemia
•Crohn’s Disease
•Pancreatic Cancer
•Diabetes mellitus
•Gut bacteria & the effects of antibiotics
•Gall stones
•The hepatic portal system
•Liver Disease (cirrhosis)
•Kidney Stones
•Kidney Failure & Dialysis
•Common cancers of GI tract
•Competitive Eating
•Addiction
•Obesity
•Effects of Exercise on the whole body
•Fraternal, Identical, & Siamese Twins
•Endometriosis
•Cervical & Ovarian Cancer
•Premature Ovarian Failure
•Female causes of Infertility
•Male causes of Infertility
•Prostate Cancer and/or Breast Cancer
•Androgen Insensitivity Syndrome
•Klinefelter’s Syndrome (XXY)
•Turner’s Syndrome (XO)
•Kallman’s Syndrome
•Growth Hormone Deficiency & Excess
•Disorders of the thyroid (ie. Graves’)
•Cushing’s Disease
•Addison’s Disease
The Digestive System
Ch 23
Leonardo Da Vinci
Human Anatomy
Sonya Schuh-Huerta, Ph.D.
Function of the Digestive System
Digestion = the mechanical & chemical
breakdown of food to allow absorption
of nutrients into the bloodstream
The Building Blocks
Overview of the Digestive
System
• Organs are divided into 2 groups
– Alimentary canal (= GI tract)
• Mouth, pharynx, & esophagus
• Stomach, small intestine, & large intestine
– Accessory digestive organs
• Teeth & tongue
• Salivary glands, gallbladder, liver, & pancreas
– Accessory organs are connected to the alimentary
canal by ducts
• Secretions contribute to breakdown of foodstuffs
The Alimentary Canal & Accessory
Digestive Organs
Mouth (oral cavity)
Tongue
Esophagus
Liver
Parotid gland
Sublingual gland Salivary glands
Submandibular
gland
Pharynx
Stomach
Pancreas
(Spleen)
Gallbladder
Duodenum
Small intestine Jejunum
Ileum
Anus
Transverse colon
Descending colon
Ascending colon
Cecum
Large intestine
Sigmoid colon
Rectum
Vermiform appendix
Anal canal
Digestive Processes
• 1.) Ingestion  occurs in the mouth
• 2.) Propulsion  movement of food
– Peristalsis  major means of propulsion
• 3.) Mechanical digestion  physical
breakdown of food, prepares food for
chemical digestion
– Chewing, churning of food in stomach
• Segmentation  rhythmic local constrictions
of intestine
Digestive Processes
• 4.) Chemical digestion  complex
molecules broken down to chemical
components
– Mouth
– Stomach
– Small intestine
• 5.) Absorption  transport of digested
nutrients into the blood
• 6.) Defecation  elimination of
indigestible substances as feces
Digestion in Action
animation by www.encognitive.com
Digestive Processes
Ingestion
Mechanical
digestion
• Chewing (mouth)
• Churning (stomach)
• Segmentation
(small intestine)
Chemical
digestion
Food
Pharynx
Esophagus
Propulsion
• Swallowing
(oropharynx)
• Peristalsis
(esophagus,
stomach,
small intestine,
large intestine)
Stomach
Absorption
Lymph
vessel
Small
intestine
Large
intestine
Defecation
Blood
vessel
Mainly H2O
Feces
Anus
Figure 23.2
Peristalsis
• Major means of
propulsion
• Adjacent
segments of the
alimentary canal
relax & contract
Segmentation
• Rhythmic local
contractions of the
intestine
• Mixes food with
digestive juices
Microscopic Anatomy of the
Digestive Tract
clipartguide.com
Histology of the Alimentary
Canal Wall
• Same 4 layers from esophagus to anus
• The mucosa  innermost layer (lines the
lumen)
• Consists of:
– Epithelium
– Lamina propria (many capillaries & lymphoid tissue)
– Muscularis mucosae (2 layers of smooth m.)
• The submucosa  external to the mucosa
– Contains blood & lymphatic vessels, nerve fibers,
glands, etc.
Histology of the Alimentary
Canal Wall
• The muscularis externa (or muscularis) 
external to the submucosa
– 2 layers
•Circular muscularis  inner layer
•Longitudinal muscularis  outer layer
• The serosa  the outermost layer
*Is the visceral peritoneum (remember this?…)
Histology 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
Longitudinal muscle
Circular muscle
Serosa
Epithelium
Connective tissue
Mesentery
Nerve
Artery
Gland in mucosa
Vein
Duct of gland outside
Lymphatic vessel
alimentary canal
(a) Longitudinal and cross-sectional views through the small intestine
Lumen
Mucosa-associated
lymphoid tissue
Histology of the Alimentary Canal
Mucosa
Submucosa
Muscularis externa
Serosa
(b) Light micrograph cross section through the small intestine (30)
Smooth Muscle
•
•
•
•
Primarily found in walls of viscera
Fibers elongated
Have one centrally located nucleus
Grouped into sheets
– Longitudinal layer  parallel to long axis of
organ
– Circular layer  deeper layer, fibers run
around circumference of organ
Smooth Muscle
Longitudinal layer of
smooth muscle (shows
smooth muscle fibers in
cross section, 145)
Small intestine
(a) Location and plane of
section shown in (b)
Mucosa
(b) Cross section of the intestine
showing the smooth muscle
layers (one circular and the
other longitudinal) running
at right angles to each other
Circular layer of smooth
muscle (shows longitudinal
views of smooth muscle
fibers, 145)
Smooth Muscle Contraction
• Myofilaments operate by interaction with cytoskeleton
• Dense bodies  similar to Z-discs of skeletal muscle
• No sarcomeres (but Ca2+ is a key player)
Intermediate
filament
Caveolae
Gap junctions
Dense bodies
Nucleus
(a) Relaxed smooth muscle fiber (note that adjacent
fibers are connected by gap junctions)
Nucleus
Dense bodies
(b) Contracted smooth muscle fiber
Exercising Your Muscle Memory
Innervation of Smooth Muscle
• Innervated by ANS (remember this..?)
• Few fibers per sheet innervated
– Sheet of smooth muscle contracts as a unit
• Exceptions
– Iris of eye
– Arrector pili muscles in skin
Innervation of Smooth Muscle
Varicosities
Autonomic
nerve fibers
innervate
most smooth
muscle fibers.
Smooth
muscle
cell
Synaptic
vesicles
Mitochondrion
Varicosities release
their neurotransmitters
into a wide synaptic
cleft (a diffuse junction)
Nerve Plexuses
• Myenteric nerve plexus
• Lies in muscularis externa
• Controls peristalsis & segmentation
• Submucosal nerve plexus
– Lies in submucosa
– Signals glands to secrete
• Innervation
– Sympathetic & parasympathetic motor fibers
– Visceral sensory fibers
Nerve Plexuses
Intrinsic nerve plexuses
Myenteric nerve plexus
Submucosal nerve plexus
Glands in submucosa
Mucosa
Epithelium
Lamina propria
Muscularis mucosae
Submucosa
Muscularis externa
Longitudinal muscle
Circular muscle
Serosa
Epithelium
Connective tissue
Mesentery
Nerve
Artery
Gland in mucosa
Vein
Duct of gland outside
Lymphatic vessel
alimentary canal
Lumen
Mucosa-associated
lymphoid tissue
(a) Longitudinal and cross-sectional views through the small intestine
Gross & Microscopic Anatomy
of Organs of the Digestive Tract
Use as a Lab Guide
(both lecture & lab material!)
The Mouth & Associated Organs
• The mouth  oral cavity
– Mucosal layer
• Stratified squamous epithelium
• Lamina propria
• The lips & cheeks
– Formed from orbicularis oris & buccinator
muscles, respectively (remember these?…)
Anatomy of the Mouth
Soft palate
Palatoglossal arch
Hard palate
Oral cavity
Palatine
tonsil
Tongue
Oropharynx
Lingual tonsil
Epiglottis
Hyoid bone
Laryngopharynx
Esophagus
Trachea
(a) Sagittal section of the oral cavity and pharynx
Uvula
Anatomy of the Mouth
• The labial frenulum
– Connects lips to gums
• The palate
– Forms the roof
of the mouth
Gingivae
(gums)
Palatine
raphe
Upper lip
Superior labial
frenulum
Soft palate
Palatoglossal
arch
Palatopharyngeal
arch
Uvula
Palatine
tonsil
Posterior wall
of oropharynx
Hard palate
Tongue
Sublingual
fold with
openings of
sublingual
ducts
Lingual frenulum
Opening of
submandibular
duct
Gingivae (gums)
Vestibule
Lower lip
(b) Anterior view
Inferior labial
frenulum
The Tongue
•
•
•
•
•
•
Interlacing fascicles of skeletal muscle
Grips food & repositions it – aids in mastication
Helps form some consonants in speaking
Intrinsic muscles  within the tongue
Extrinsic muscles  external to the tongue
Lingual frenulum
– Secures tongue to floor of mouth
The Superior Surface of the
Tongue
• Tongue papillae
– Filiform papillae  No taste buds
– Fungiform & vallate papillae  Taste buds
• Posterior 1/3 of tongue  lingual tonsil
Superior Surface of the Tongue
Epiglottis
Palatopharyngeal
arch
Palatine tonsil
Lingual tonsil
Palatoglossal
arch
Terminal sulcus
Vallate papilla
Midline groove
of tongue
Fungiform papilla
Filiform papilla
The Teeth
• Deciduous (“milk”) teeth  20 teeth
– Begin to appear at 6 months of age
• Permanent teeth  32 teeth
– Most erupt by the end of adolescence
• Dental formula  shorthand
– Way to indicate number & position
of teeth
• 2I, 1C, 2P, 3M
The Teeth
Deciduous teeth
Permanent teeth
Tooth Structure
Enamel
Dentin
• Longitudinal
section of tooth
in alveolus
Crown
Dentinal tubules
Pulp cavity
(contains
blood vessels
and nerves)
Neck
Gingiva
(gum)
Cementum
Root
Root canal
Periodontal
ligament
Apical
foramen
Bone
The Salivary Glands
• Exocrine glands (= have ducts)
• Produce saliva & secrete amylase enzyme 
breaks down starch (complex carbs) into
maltose  1st stage of chemical digestion!
• Compound tubuloalveolar glands
– Parotid glands
– Submandibular glands
– Sublingual glands
The Salivary Glands
Tongue
Teeth
Ducts of
sublingual
gland
Frenulum
of tongue
Sublingual
gland
Mylohyoid
muscle (cut)
Anterior belly of
digastric muscle
Parotid
gland
Parotid duct
Masseter muscle
Body of mandible
(cut)
Posterior belly of
digastric muscle
Submandibular
duct
Submandibular
gland
Mucous cells
Serous cells
forming
demilunes
The Pharynx
• Oropharynx & laryngopharynx
– Passages for air & food
– Lined with stratified squamous epithelium
– External muscle layer
• Consists of superior, middle, & inferior pharyngeal
constrictors (…remember these?)
The Pharynx
Cribriform plate
of ethmoid bone
Frontal sinus
Nasal cavity
Nasal conchae
(superior, middle
and inferior)
Sphenoid sinus
Posterior nasal
aperture
Nasopharynx
Pharyngeal tonsil
Opening of
pharyngotympanic
tube
Nasal meatuses
(superior, middle,
and inferior)
Nasal vestibule
Nostril
Uvula
Oropharynx
Palatine tonsil
Isthmus of the
fauces
Hard palate
Soft palate
Laryngopharynx
Lingual tonsil
Hyoid bone
Esophagus
Trachea
Tongue
Larynx
Epiglottis
Vestibular fold
Thyroid cartilage
Vocal fold
Cricoid cartilage
Thyroid gland
The Esophagus
• Gross anatomy  muscular tube
– Begins as a continuation of the pharynx
– Joins the stomach inferior to the diaphragm
– Hole through diaphragm that allows
esophagus through  hiatus
• Cardiac sphincter  closes lumen to prevent
stomach acid from entering esophagus
The Esophagus
• Microscopic anatomy
– Stratified squamous epithelium
– When empty, mucosa & submucosa in
longitudinal folds
– Mucus glands
– Muscularis externa
• Skeletal muscle first 1/3
of length
– Adventitia  most
external layer
Microscopic Structure of Esophagus
Mucosa
(contains a stratified
squamous epithelium)
Submucosa (areolar
connective tissue)
Lumen
Muscularis externa
Circular layer
Longitudinal layer
Adventitia (fibrous
connective tissue)
(a) Cross section through esophagus (5)
(b) Gastroesophageal
junction, longitudinal
section (85)
The Stomach
• Site where food is churned into chyme
• Secretion of pepsin begins protein digestion
– Functions under acidic conditions
• Food remains in stomach ~1–4 hours
• Rugae  ridges of stomach mucosa
• Regions of the stomach:
–
–
–
–
Cardiac region
Fundus
Body
Pyloric region
The Stomach
Cardiac region
Fundus
Esophagus
Muscularis externa
Longitudinal layer
Circular layer
Oblique layer
Serosa
Body
Lumen
Lesser
curvature
Rugae of
mucosa
Greater
curvature
Duodenum
Pyloric
canal
Pyloric sphincter
(valve) at pylorus
Pyloric
antrum
The Stomach
Liver
(cut)
Fundus
Body
Spleen
Lesser
curvature
Greater
curvature
Microscopic Anatomy of the
Stomach
• Muscularis has 3 layers
– Circular & longitudinal layers AND oblique layer
• Epithelium is  simple columnar epithelium
• Mucosa dotted with gastric pits
– Gastric glands  deep to
gastric pits
Microscopic Anatomy of the
Stomach
• Gastric glands of fundus & body
– Mucous neck cells
• Secrete a special mucus
– Parietal cells
• Secrete HCl & gastric intrinsic factor
– Chief cells
• Secrete pepsinogen
– Pepsinogen is activated to pepsin when it encounters
acid in the gastric glands
The Stomach – Microscopic Anatomy
Gastric pits
Surface epithelium
(mucous cells)
Gastric
pit
Mucous neck cells
Parietal cell
Gastric
gland
Chief cell
Enteroendocrine cell
(b) Enlarged view of gastric pits and gastric glands
The Stomach – Microscopic Anatomy
Pepsinogen
Pepsin
HCl
Mitochondria
Parietal cell
Chief cell
Enteroendocrine
cell
(c) Location of the HCl-producing parietal ells and
pepsin-secreting chief cells in a gastric gland
The Stomach – Microscopic Anatomy
Mucus-secreting
cells
Gastric pits
Surface mucous cell
Mucus neck cells
Gastric
gland
HCl secreting parietal cells
Enzyme secreting chief cells
Muscularis
mucosae
(d) Micrograph of the stomach mucosa (115)
The Small Intestine
• Longest portion of GI tract
• Site of most enzymatic digestion & absorption 
chyme here ~3–6 hrs
• 3 subdivisions:
 16 ft long!
– Duodenum
– Jejunum
– ileum
 200 square meters!
• Innervation
– Parasympathetic fibers from vagus nerve
– Sympathetic from thoracic splanchnic nerves
• Small & large intestine  site of quadrillions of
microorganisms!!!
The Gut Flora
• 10X as many microbes as there are
cells of the human body!!!
• Perform many metabolic activities  “forgotten organ”
• Bacteria  most of the flora, also fungi & protozoa
• Makes up 60% of the dry mass of feces!
• About 500 species in gut (small & large intestines)
• 99% of bacteria  from about 30–40 species
• Symbiotic Relationship!
– Fermenting unused substrates (carbs  SCFAs)
– Training Immune System
– Preventing growth of harmful pathogenic bacteria
– Regulating development of the gut
– Producing vitamins (biotin/B vitamins, vit K, etc.)
– Producing hormones (that mediate fat storage)
The Duodenum
• Receives digestive enzymes & bile from
pancreas & gallbladder
• Main pancreatic duct & common bile
duct enter duodenum
– Sphincters control entry of bile & pancreatic
juices
The Duodenum & Related Organs
Right & left
hepatic ducts
of liver
Liver
Common hepatic
duct
Cystic duct
Common Bile duct &
sphincter
Accessory pancreatic duct
Mucosa
with folds
Gallbladder
Major duodenal
papilla
Hepatopancreatic
ampulla and
sphincter
Duodenum
Tail of pancreas
Pancreas
Jejunum
Main pancreatic duct &
sphincter
Head of pancreas
Small Intestine – Adaptations for
Absorption
– Circular folds (plicae
circulares)
• Transverse ridges of mucosa
& submucosa
– Villi
• Finger-like projections of the mucosa
• Covered with  simple columnar epithelium
– Microvilli
• Many tiny microvilli on apical surface of cells
• Villi & microvilli further increase surface area for
absorption
Microscopic Anatomy of Small
Intestine
• Absorptive cells
– Uptake digested nutrients
• Goblet cells
– Secrete mucus that lubricates
chyme & forms protective barrier
• Enteroendocrine cells
– Secrete hormones that stimulate pancreas & gallbladder
• Intestinal crypts
– Epithelial cells secrete intestinal juice
– Rapidly dividing epithelial cells (stem cells)  replace
epithelium every 3–6 days!!! Without these, you would lose
your entire intestine within a week!
The Small Intestine – Structural Features
Vein carrying
blood to
hepatic portal
vessel
Muscle
layers
Microvilli
(brush
border)
Lumen
Circular
folds
Absorptive
cells
Villi
Lacteal
Goblet
cell
Blood
capillaries
(a)
Mucosa
associated
lymphoid
tissue
Intestinal
crypt
Muscularis
mucosae
(b)
Duodenal
gland
Absorptive cells
Vilus
Goblet
cells
Villi
Enteroendocrine
cells
Venule
Lymphatic vessel
Submucosa
Stem cells
(c)
Intestinal crypt
The Large Intestine
•
•
•
•
Digested residue contains few nutrients
In large intestine ~12–24 hrs
Some digestion by bacteria
Main functions:
– Absorb water & electrolytes (NaCl)
• Mass peristaltic movements force feces
toward rectum
Gross Anatomy of Large Intestine
• Subdivided into:
– Cecum, vermiform 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
Gross Anatomy of Large Intestine
Left colic
(splenic) flexure
Transverse
mesocolon
Right colic
(hepatic) flexure
Epiploic
appendages
Transverse colon
Superior
mesenteric artery
Descending colon
Haustrum
Ascending colon
Cut edge of
mesentery
IIeum
IIeocecal valve
Teniae coli
Cecum
Sigmoid colon
Vermiform appendix
Rectum
Anal canal
External anal sphincter
Gross Anatomy of Large Intestine
• Cecum
– Blind pouch
– Beginning of large intestine
• Vermiform appendix
– Contains lymphoid tissue
– Neutralizes pathogens
• Colon
– Divided into distinct segments
• Ascending, transverse, descending, & sigmoid colon
Gross Anatomy of Large Intestine
Left colic
(splenic) flexure
Transverse
mesocolon
Right colic
(hepatic) flexure
Epiploic
appendages
Transverse colon
Superior
mesenteric artery
Descending colon
Haustrum
Ascending colon
Cut edge of
mesentery
IIeum
IIeocecal valve
Teniae coli
Cecum
Sigmoid colon
Vermiform appendix
Rectum
Anal canal
External anal sphincter
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
Gross Anatomy of Rectum & Anal Canal
Rectal valve
Rectum
Hemorrhoidal
veins
Levator ani muscle
Anal canal
External anal
sphincter
Internal anal
sphincter
Anal columns
Anal valves
Pectinate line
Anal sinuses
Anus
Microscopic Anatomy of Large
Intestine
• Villi are absent
• Contains numerous
goblet cells (mucus)
• Intestinal crypts
• Lined with simple columnar
epithelium
– Epithelium changes at anal canal
Looks “fern-like”
• Becomes stratified squamous epithelium
Microscopic Anatomy of Large Intestine
Absorptive cells
Lamina propria
Goblet cells
Intestinal crypts
 Looks “fern-like”
Muscularis
mucosae
The Liver
• Largest gland in the body
– Performs over 500 functions…
– Digestive function:
• Bile production
• Bile emulsifies (breaks up) fats into tiny particles
that are more accessible to digestive enzymes
– Performs many metabolic functions!
– Body storage site of glucose (as glycogen)
– Processes fats, amino acids, & stores vitamins
– Detoxifies many poisons & toxins in the blood
– Makes & breaks down blood proteins
The Liver
Sternum
Nipple
Bare area
Liver
Falciform
ligament
Left lobe
of liver
Right lobe of liver
Gallbladder
Round
ligament
(ligamentum
teres)
Visceral Surface of the Liver
Lesser omentum
(in fissure)
Caudate lobe
of liver
Left lobe of liver
Porta hepatis
containing hepatic
artery (left) and
hepatic portal vein
(right)
Quadrate lobe
of liver
Bare area
Sulcus for
inferior
vena cava
Hepatic
vein (cut)
Bile duct
(cut)
Right lobe
of liver
Ligamentum teres
Gallbladder
Visceral Surface of the Liver
Hepatic portal vein
Caudate
lobe
Hepatic veins
Inferior vena
cava
Bare area
Left lobe
Ligamentum
venosum in
fissure
Porta hepatis
Right hepatic
artery
Left hepatic artery
Right hepatic
duct
Left hepatic duct
Cystic duct
Common hepatic
duct
Gallbladder
Fissure
Falciform ligament
Ligamentum teres
Right lobe
Quadrate lobe
Microscopic Anatomy of the
Liver
• Hepatocyte = functional cell of the liver
• Portal triad composed of:
– Bile duct tributary
– Branch of hepatic portal vein
– Branch of hepatic artery
Portal triad
Lobule
Central vein
Microscopic Anatomy of the Liver
(a)
(b)
Lobule
Central vein Connective
tissue septum
Interlobular veins
(to hepatic vein)
Central vein
Sinusoids
Bile canaliculi
Plates of
hepatocytes
Bile duct (receives
bile from bile
canaliculi)
Fenestrated
lining (endothelial
cells) of sinusoids
Hepatic
macrophages in
sinusoid walls
Portal vein
(c)
Bile duct
Portal venule
Portal arteriole
Portal triad
Functions of Hepatocytes
• 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 (as glycogen)
Great capacity for regeneration!
The Gallbladder
• Stores & concentrates bile
• Expels bile into duodenum
• Cholecystokinin 
– Released from enteroendocrine cells of small
intestine in response to fatty chyme
– Causes contraction of gallbladder &
entry of bile into duodenum
The Gallbladder & Related Organs
Right & left
hepatic ducts
of liver
Liver
Common hepatic
duct
Cystic duct
Common Bile duct &
sphincter
Accessory pancreatic duct
Mucosa
with folds
Gallbladder
Major duodenal
papilla
Hepatopancreatic
ampulla and
sphincter
Duodenum
Tail of pancreas
Pancreas
Jejunum
Main pancreatic duct &
sphincter
Head of pancreas
The Pancreas
• Exocrine function (exocrine pancreas)
– Acinar cells  make, store, & secrete
pancreatic enzymes (get dumped into duodenum)
– Enzymes are activated in duodenum
• Endocrine function (endocrine pancreas)
– Cells of pancreatic islets (Islets of
Langerhans)
 Produce insulin & glucagon &
somatostatin
 Regulate blood sugar
The Exocrine Pancreas – Histology
Diaphragm
Liver
Spleen
Pancreas
Tail
Body
Head
Duodenum
Acinar
cells
(b) Photomicrograph of the exocrine
acinar cells of the pancreas (160)
Small
duct
Acinar cells
(a) Dissection illustrating the pancreas and its
relationship to surrounding organs in the
superior abdomen
Basement
membrane
Zymogen
granules
Rough
endoplasmic
reticulum
(c) Illustration of the pancreatic acinar cells
Morphology & Function of GI Organs
Morphology & Function of GI Organs
Abdominal Regions
• 4 lines divide abdominal wall into 9 regions
– Midclavicular lines  vertical lines of grid
– Subcostal plane  superior horizontal line
• Connects inferior points of costal margin
– Transtubercular plane  inferior horizontal line
• Connects tubercles of iliac crests
9 Regions of Anterior Abdominal Surface
Right
hypochondriac
region
Right
lumbar
region
Right iliac
(inguinal)
region
Epigastric
region
Left
hypochondriac
region
Umbilical
region
Left
lumbar
region
Hypogastric
(pubic)
region
Left iliac
(inguinal)
region
(a) Nine regions delineated by four planes
9 Regions of Anterior Abdominal Surface
• How regions relate to abdominal viscera
Liver
Diaphragm
Gallbladder
Stomach
Ascending colon
of large intestine
Small intestine
Cecum
Appendix
Transverse colon
of large intestine
Descending colon
of large intestine
Initial part of
sigmoid colon
Urinary bladder
(b) Anterior view of the nine regions showing the
superficial organs
Abdominal Quadrants
• A simpler method of sectioning the anterior
abdominal wall
– Right upper quadrant
– Left upper quadrant
– Right lower quadrant
– Left lower quadrant
The Peritoneal Cavity & Peritoneum
• Peritoneum  a serous membrane
– Visceral peritoneum  surrounds digestive
organs
– Parietal peritoneum  lines the body wall
• Peritoneal cavity  a slit-like potential
space
The Peritoneal Cavity & Peritoneum
• Mesentery  a double layer of peritoneum
– Holds organs in place
– Sites of fat storage
– Provides a route for circulatory vessels & nerves
The Peritoneal Cavity & Peritoneum
Abdominopelvic
cavity
Liver
Alimentary
canal organ
Ventral
mesentery
Alimentary
canal organ
Alimentary canal organ
in a retroperitoneal
position
Parietal
peritoneum
Visceral
peritoneum
Peritoneal
cavity
Vertebra
Dorsal
mesentery
(a) Schematic cross sections of abdominal cavity
illustrating the peritonea and mesenteries
Falciform
ligament
Anterior
Visceral
peritoneum
Peritoneal
cavity (with
serous fluid)
Liver
Stomach
Parietal
peritoneum
Kidney
(retroperitoneal)
Posterior
Wall of
body trunk
(b) Illustration of the peritonea in a cross section
through the superior abdomen, inferior view
Mesentery
resorbed
and lost
(c) Some organs lose their mesentery
and become retroperitoneal during
development.
The Peritoneal Cavity & Peritoneum
• Retroperitoneal organs
– Behind the peritoneum
• Peritoneal organs
– Digestive organs that keep their mesentery
Mesenteries
• Superficial view of abdominal organs
Falciform ligament
Liver
Gallbladder
Spleen
Stomach
Ligamentum teres
Greater omentum
Small intestine
Cecum
(a)
Mesenteries
• Greater omentum
 a “fatty apron” of
peritoneum
• Greater omentum &
transverse colon
reflected
Greater omentum
Transverse colon
Transverse
mesocolon
Descending colon
Jejunum
Mesentery
Sigmoid
mesocolon
Sigmoid colon
Ileum
Mesenteries
• Lesser omentum attaches to lesser curvature
of stomach
Liver
Gallbladder
Lesser omentum
Stomach
Duodenum
Transverse colon
Small intestine
Cecum
Urinary bladder
Mesenteries
• Sagittal section
through the
abdominopelvic
cavity
• Mesenteries attach
to posterior
abdominal wall
Liver
Lesser omentum
Pancreas
Stomach
Duodenum
Transverse
mesocolon
Transverse colon
Mesentery
Greater omentum
Jejunum
Ileum
Visceral peritoneum
Parietal peritoneum
Urinary bladder
Rectum
Secondarily Retroperitoneal
Organs
• Initially formed within peritoneum
• Become retroperitoneal
– Fuse to posterior abdominal wall
Summary of Intraperitoneal &
Secondarily Retroperitoneal Organs
Disorders of the Digestive System
• 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
Peptic Ulcers
• Caused by Helicobacter pylori
• H. pylori
– Acid-resistant
– Binds to gastric epithelium
• Induces oversecretion of acid & inflammation
Peptic Ulcers
Bacteria
Mucosa
layer of
stomach
(a) A gastric ulcer lesion
(b) H. Pylori bacteria
Disorders of the Digestive System
• Intestinal obstruction
– Mechanical obstructions
• Adhesions, tumors, or foreign objects
– Nonmechanical obstruction
• Halt in peristalsis
– Trauma
– Intestines touched during surgery
Disorders of the Digestive System
• Inflammatory bowel disease
– Inflammation of intestinal wall
• Crohn’s disease
• Ulcerative colitis
• Viral hepatitis
– Jaundice & flu-like symptoms
– Major types  A, B, C, & G
• Liver Disease  acute hepatitis, cirrhosis,
liver failure, etc.
Disorders of the Digestive System
• Cystic fibrosis & the pancreas
– Pancreatic ducts become blocked with mucus
• Prevent pancreatic juices from entering sm. intest
• Leads to malabsorption of fats & other nutrients
• Many cancers of the GI tract
The Digestive System with Age
• Middle age  gallstones & ulcers, also acid reflux
• Old age  activity of digestive organs decline
–
–
–
–
Fewer digestive juices & enzymes produced
Absorption is less efficient
Dehydration of fecal mass leads to constipation
Diverticulosis & cancer of digestive organs more
common
• Healthy diet/nutrition, hydration
throughout life  can help greatly!
Questions…?
What’s Next?
Lab: Finish GI Tract & Start
Urinary System
Wed Lecture: Urinary Sys & Reprod
System
Wed Lab: Reprod System
Leonardo Da Vinci