Download - Digestive System Part I -NSU
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Histology 10a
Gregory Rodocker
NSU
Class Taken: Spring 2009
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Digestive tract
Composed of Oral cavity, esophagus, stomach, small
and large intestines, rectum and anus Associated glands such as the salivary
glands, liver and pancreas
Digests and absorbs food for the entirebody
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General Structure
Composed of four layers mucosa,
Submucosa
Muscularis
Serosa
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Mucosa
Composed of An inner epithelial layer peculiar and appropriate
to the regions A lamina propria composed of loose CT A muscularis mucosae of smooth muscle
An inner circular layer An outer longitudinal layer
Known collectively as the mucousmembrane
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Submucosa
Composed of Dense CT
Many blood and lymph vessels
Submucosal nerve plexus (Meissners)
(glands and lymphoid tissue)
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Muscularis
Smooth muscle layer Inner circular
Outer longitudinal
Myenteric nerve plexus (Auerbachs)
between two layers
Blood vessels and lymph vesselsbetween two layers
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Serosa
Composed of Thin layer of loose CT
Blood vessels and lymph vessels
Adipose tissue
A thin epithelium called the mesothelium
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Chagas Disease
Between 16 to 18 million people worldwidehave Chagas disease, and although mostare in South America, the number of cases
in the US is growing. Chagas disease is anincurable infectious disease, and its long-term sequelae include cardiomyopathy,megaesophagus and megacolon. Importantin these complications is the fact thatTrypanosoma cruzi, the infective agent ofChagas disease, invades myocytes,neurons and glial cells.
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Megacolon/megaesophalus
Chagas Disease
Trypanosoma cruzi, the causative
organism of American trypanosomiasisattacks Auerbachs plexus (proposed)
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Triatome Bug
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Romanas Sign
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Megacolon Man
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Functions of the digestive tract
Lubricate, digests and absorb foods
Produce hormones for the control of
the tract
Protect from infective agents in the gut
Produce antibodies
Propel food along tract
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The oral cavity
Various regions covered by keratinizedand non-keratinized stratified
squamous epithelium Keratinized gingiva and hard palate Nonkeratinized soft palate, lips, cheeks
and floor of mouth Interesting transition can be seen in lips
where keratinized of skin changes into oralnonkeratinized epithelium
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Tongue
Mass of striated muscle with fibersrunning in at least three planes
Lots of CT Dorsal surface marked by papillae
Filiform poorly developed in humans
Fungiform mushroom-shaped Circumvalate largest
Some have taste buds
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Taste bud
Taste or gustatory
pore
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Taste buds
50 -100 cells with most being taste
cells with some supportive cells
Located basally are basal cells relaceall cell types
Sweet and bitter work via receptors
and bitter, sour and salty work via ionchannels
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Esophagus
Carries foodstuffs from the mouth tothe stomach
Lined by nonkeratinized, stratifiedsquamous epithelium
Upper third - striated muscle
Middle third - striated and smoothmuscle Lower third smooth muscle
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Stomach
Mix of exocrine and endocrine glandular
columnar epithelium
Partitioned into four regions Cardiac
Lysozyme?
Fundus
Body Pylorus
Lysozyme?
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Stomach wall
The mucosa of the stomach is highlyfolded resulting in gastric pits
Stem cells - totipotent Mucous neck cells Oxyntic/parietal cells HCl, intrinsic
factor (vitamin B-12) Mid to upper wall
Chief/zymogenic cells pepsinogen andlipase Lower wall
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Gastric gland of fundal
region
Goblet cells - mucus
Parietal cells
Chief/zymogenic cells
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Oxyntic/Parietal Cell
Oxyntic from Gr. sour;
make acidic
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Small Intestine
Food digestion, absorption and
hormone production
Composed of (5 meters) Duodenum
Jejunum
Ileum
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Common features
Plicae circulares Semilunar, circular and spiral fold of the
wall most obvious in the jejunum Intestinal villi
Leaf-like (duodenal) or finger-like (ileal)
folds of the mucosa and lamina propria In between villi are pits called intestinal
glands or glands of Lieberkhn
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Common features (contd)
Glands contain stem cells, absorptive
cells, Paneths cells and
enteroendocrine cells Absorptive cells with microvilli
Each cell with 3000, 1 mm2 contains 200
million
Plicae increase SA 3X, villi increase SA 10X,
microvilli increase SA 20X equaling a 600X
increase in SA in SI equaling 200 m2 total SA
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Common features (contd)
Paneths cells produce lysozyme Lysozyme is a generic antibacterial
attacking the cell walls and capsids ofbacteria and viruses
May serve role in controlling intestinal
flora
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Duodenal glands in
submucosa
Brunners Glands
Alkaline mucus
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Note the blood
supply in the villus.
What do you thinkhappens to the
oxygen level as
blood makes it to
the tip? Note lacteals in the
villus
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Large Intestine
No villi
Muscularis is modified Typical inner circular layer of muscle
Outer longitudinal layer is congregated
into three bundles called the teniae coli
What does that mean in a cross section ofthe large intestines?
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Cell renewal