digestive system part i -nsu

8/14/2019 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

digestive system part i -nsu

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