L34 Structure & Function Of The Small And Large Intestines

Front 1

What is the small intestine the site of?

Back 1

The small intestine is the site of terminal digestion of food

Front 2

What does the ileum consist of?

Back 2

Itconsists of three parts: the duodenum, the jejunum and the ileumwhich have common histological and topographical features aswell as distinctions allowing each region to be identified

Front 3

Which sections are retroperitoneal and which are intraperitoneal?

Back 3

Theduodenum is, for the most part, a retroperitoneal structure whilethe jejunum and ilium are intraperitoneal.

Front 4

What does the inner lining of the small intestine form?

Back 4

Throughout its length the inner lining forms a series of ridges, theplicae circularis, which are covered with tall finger-like projectionsof the mucosa to form villi

Front 5

What are between these tubular glands?

Back 5

Between these are the tubular glandsor crypts of Lieberkuhn which extend to or beyond the musculariscoat

Front 6

What is the epithelium of the small intestine?

Back 6

The epithelium of the small intestine is simple columnar(enterocytes) with goblet cells

Front 7

What are the simple columnar cells?

Back 7

The simple columnar cells are theabsorptive cells and have a brush border to increase their surfacearea.

Front 8

What features of the small intestine enhance it's surface area?

Back 8

The small intestine hasa folded mucosal coat,a series of villi and anepithelium with a brushborder. All thesefeatures greatlyincrease the surfacearea.

Front 9

Why do the ducts of the gall bladder and pancreas open into the duodenum?

Back 9

The ducts of the gall bladder and pancreas open into the duodenum bringing digestiveenzymes, bicarbonate (to counter the acidic chyme entering the duodenum from thestomach and bile salts from the liver to emulsify the fats

Front 10

How does the membrane change from the jejunum to the ileum?

Back 10

There is a decrease inthe folding of themucous membraneand an increase inlymphoid tissue fromjejunum to ileum

Front 11

What are the layers of the small intestine?

Back 11

The layers of thesmall intestine followthe same pattern asthe rest of the GIT inhaving a mucosa, asubmucosa, amuscular layer anda serosa.

Front 12

What types of cells does the epithelium consist of?

Back 12

The epithelium consistsof 5 types of cells:

1. Enterocytes

2. Goblet

3. Paneth

4. Endocrine

5. Stem

Front 13

What are the enterocytes?

Back 13

The enterocytes are thetall columnar cell withbasely placed nucleiwhich contain between 2-3000 microvilli and,which in turn, are coatedwith glycoproteinscontaining a number ofenzymes.

The enterocytes are theabsorptive cells.

Front 14

How are Glucose and galactose absorbed by the enterocyte?

Back 14

Glucose and galactose are absorbedby the enterocyte by active transportusing Na+ dependent glucosetransporters (SGLT1)

Front 15

How is fructose absorbed by the enterocyte?

Back 15

Fructose is absorbed by theenterocyte by active transport usingNa+ dependent glucose transporters (GLUT5)

Front 16

How do the absorbed monosaccharides pass through the basal membrane?

Back 16

The absorbed monosaccharidespass through the basal membraneusing GLUT2 glucose transporters

Front 17

How are proteins digested and absorbed in the small intestine?

Back 17

Protein digestion starts in thestomach with pepsin whichhydrolyses proteins into largepolypeptides.

Pancreatic proteolytic enzymesacting in the small intestine breakdown the polypeptides into freeamino acids which are transportedinto the cell and from there into theunderlying capillaries.

Front 18

Describe the Digestion & Absorption of Lipids

Back 18

Front 19

What are the goblet cells of the epithelium of the small intestine?

Back 19

These are situated amongst the enterocytes and in thesmall intestine are as numerous as the enterocytes.

Front 20

What are the paneth cells of the epithelium?

Back 20

Paneth cells are found in the lower third of the cryptsand have basal nuclei and prominent granules. Theyrelease digestive enzymes, immunoglobulins andlysozyme. Paneth cells secretions therefore help todestroy parasites and bacteria

Front 21

what are the endocrine cells?

Back 21

These are usually found in the lower 1/3rd of thecrypts and secrete a number of hormones

Front 22

What are the functions of the endocrine cells?

Back 22

1. Regulate water and electrolyte metabolism andenzyme secretion.

2. Regulation of gastrointestinal motility and mucosalgrowth.

3. Stimulation of the release of other hormones

Front 23

What does the lamina propria consist of?

Back 23

The lamina propria consists of loose connective tissue with bloodand lymph vessels, nerve fibres and smooth muscle

Front 24

What types of tissue can be seen indicative of the lamina propria?

Back 24

The quantityof lymphoid tissue increases and in the ileum Peyer’s patches areclearly seen. There are also varying amounts of glandular tissue

Front 25

What do the peyer's patches contain?

Back 25

Peyer’s patches contain a germinal centre and a dome and arecovered by M cells. The dome cells are B lymphocytes and thegerminal cells are IgA positive B cells.

Front 26

What does the submucosa contain in the duodenum?

Back 26

The submucosa contains the Brunner gland in the duodenum.

Front 27

What are the features of the muscularis?

Back 27

Themuscularis is well developed and composed of an inner circularand outer longitudinal layers of smooth muscle.

Front 28

What is the distinctive feature of the duodenum?

Back 28

The distinctive feature of the duodenum is thesubmucosal Brunner glands which are mostly of themucous type which aid in neutralising the acid chymeextruded from the pylorus

Front 29

Where can the brunners glands be seen?

Back 29

Beneath the surfacevilli the Brunnerglands can clearlybe seen. Thesediminish in numberalong the length ofthe duodenum. Theglands secreteapprox. 200ml perday.

Front 30

What are the features of the jejunum?

Back 30

The jejunum has the tallest villi, there are no BrunnerGlands and few lymphoid follicles

Front 31

How can the ileum be identified?

Back 31

The ileum is easily identified due to its aggregations oflymphoid tissue, Peyer’s patches

Front 32

What is the Blood, Lymph & Nerve Supply to the Small Intestine?

Back 32

Front 33

What are the parts of the large intestine?

Back 33

The parts of thecolon are thecaecum, vermiformappendix,ascending,transverse anddescending colon,the sigmoid colon,the rectum andanal canal

Front 34

What is the function of the colon?

Back 34

The colon acts to resorb fluid andelectrolytes and form the faecalmass.

Front 35

What is one of the more obvious external features of the Colon?

Back 35

One of the more obviousexternal features of the largeintestine is the taenia coli which arethe three ribbon like thickenings ofthe longitudinal muscle. They givethe large intestine its distinctive‘puckered’ appearance

Front 36

Internally, what does the mucous membrane contain?

Back 36

Internally the mucous membranecontain a large number of glands tolubricate the colon to ease thepassage of the increasingly drymass

Front 37

Why are there large numbers of lymphocytes in the colon?

Back 37

There are large numbers oflymphocytes both in small groupsand large aggregates to counter thebacteria found in this region.

Front 38

What are the features of the layers of the colon?

Back 38

There are no villi in the colon. Thesurface cells are columnar with thecrypts containing large quantities ofgoblet cells

Front 39

What is the morphology of the enterocytes in the colon?

Back 39

The morphology of the enterocytes issame as for the small intestine andreabsorption is accomplished by thesame Na+/K+ activated ATPase driventransporter system

Front 40

Why do the goblet cells continually secrete?

Back 40

The goblet cellscontinually secrete to lubricate the bowelto facilitate the passage of theincreasingly solid contents

Front 41

Why is there considerable reabsorption in the colon?

Back 41

There is considerable reabsorption asseveral litres of fluid are added duringthe digestive process which does notinclude fluid taken in with the food

e.g.1litre from saliva, 1litre from thepancreas, 500ml from bile production