Week 3 GI workbook

Question 1

The entire GI Tract from oesophagus to anus shares certain common histological features. They all show 4 distinct functional layers throughout what are they?

Answer 1

mucosa
(epithelium, lamina propria, and muscular mucosae)

submucosa

muscularis propria
(inner circular muscle layer, outer longitudinal muscle layer)

serosa / adventitia

Question 2

what is the role of the mucosa?

Answer 2

layer which lines the gut tube – it is exposed to the contents of the gut tube. Therefore, it needs to serve different purposes depending on location in the gut tube

Question 3

what are the four basic mucosal types found in the GI tract?

Answer 3

protective
secretory
absorptive
absorptive / protective

Question 4

where would you find protective mucosa?

Answer 4

Oral cavity, pharynx, oesophagus & anal canal

Question 5

where would you find secretory mucosa?

Answer 5

Seen only in the stomach

Question 6

where would you find absorptive mucosa?

Answer 6

Typical of entire small intestine

Question 7

where would you find absorptive / protective mucosa?

Answer 7

Lines the whole of the large intestine

Question 8

what are the four junctions GI Tract mucosa undergoes abrupt transition?

Answer 8

Gastro -oesophageal junction
gastro-duodenal junction
ileo-cecal junction
Recto - anal junction

Question 9

what kind of epithelium would you find in the oesophagous?

Answer 9

Stratified squamous non-keratinised epithelium

Question 10

what type of muscle makes up the upper 1/3 of the muscularis mucosae in the oesophagous?

Answer 10

Muscular layer – upper 1/3 skeletal, middle 1/3 – smooth+ skeletal, lower 1/3 - smooth

Question 11

what are the three layers of the oesophagous?

Answer 11

surface epithelium
lamina propria
muscularis mucosae

Question 12

What two orientations do the muscular layers sit in?

Answer 12

inner circular
outer longitudinal 

Question 13

What do you notice about the thickness of the muscularis externa of the oesophagous?

Answer 13

notably thicker than in the stomach and intestine

Muscularis externa of the esophagus consists of the standard inner circular and outer longitudinal layers of smooth muscle, with Auerbach’s plexus in between

Question 14

What is the epithelial lining of the stomach?

Answer 14

Epithelium – simple columnar [looks very pale staining]

Question 15

What are the large folds present in the wall of the stomach?

Answer 15

When the stomach is empty, and not distended, the lining is thrown up into folds called rugae. After eating, these folds flatten, and the stomach is able to distend greatly.    [gastric pits]

Question 16

What secretory cells are present in the gastric glands of the stomach?

Answer 16

(Mucous secreting) Epithelial cells (simple columnar)

Question 17

what are four distinctive features of the small intestine?

Answer 17

Villi (finger like projection of the mucosa)


Columnar epithelium with striated borders 


Goblet cells (like bowl shaped drinking cups with no handles) 


Short tubular intestinal glands (Crypts of Leiberkuhn)

Question 18

what is the type of surface epithelium in the small intestine?

Answer 18

Simple columnar epithelium

Question 19

Muscularis mucosae (interna). What type of muscle is this in the small intestine?

Answer 19

smooth muscle

It consists of an outer longitudinal and inner circular layer of smooth muscle cells. It is a fairly thin layer, being only 3 to 10 cells thick, extending into the circular folds (plicae circularis).

Question 20

What are the cells found in the small intestine called and what do they secrete?

Answer 20

 Parietal cells (stain pink) – secrete HCl

Question 21

What type of cells are present in the surface epithelium of the small intestine?

Answer 21

Enterocytes are the major cell type in intestinal epithelium. They are simple columnar epithelial cells and play important roles in nutrient absorption (e.g., ions, water, sugar, peptides, and lipids) and in secreting immunoglobulins.

Question 22

Where, along the gut tube, do glands extend down beyond the muscularis mucosae (interna) into the submucosa?

Answer 22

occasionally, some acini) penetrate the muscularis mucosae and open into a crypt of Lieberkühn in the small intestine

Question 23

What is the distinguishing structure shown that tells you an image is the duodenum?

Answer 23

Brunner’s glands in submucosa

Question 24

What is the function of brunners glands?

Answer 24

located in the submucosa of the duodenum. They secrete an alkaline fluid containing mucin, which protects the mucosa from the acidic stomach contents entering the duodenum    

Question 25

what is found in the ileum?

Answer 25

peyers patches

Question 26

what are peyers patches?

Answer 26

Peyer's patches are small clusters of lymphatic tissue found in the wall of the small intestine. Specifically, they reside within the lamina propria and extend into the submucosa of the ileum. Peyer's patches act as the immune system's first line of defense against microbial and dietary antigens

Question 27

summarise the histological findings of the small intestine?

Answer 27

villi lymphocyte aggregation in lamina propria mucous glands in submucosa

Question 28

summarise the histological findings of the duodenum?

Answer 28

short leaf shaped abundant and closely packed of varying heights no lymphocyte aggregation brunners glands

Question 29

summarise the histological findings of the jejunum?

Answer 29

tongue shapes with swoolen ends, less abundant and of different heights lymphocyte aggregation absent or rare no mucous glands

Question 30

summarise the histological findings of the ileum?

Answer 30

thin finger shaped less abundant with upper level variable prominent lymphoid aggregations known as peyers patches mucous glands absent

Question 31

What is the predominant cell present in the surface epithelium of colon?

Answer 31

 enterocytes  

Question 32

What do you notice about the muscularis externa of the colon?

Answer 32

Muscularis externa of the colon has the standard layers of inner circular and outer longitudinal smooth muscle, with ganglia of Auerbach's plexus scattered in between. The longitudinal muscle is gathered into three distinct bands, the taenia coli. The outer layer of the colon is a serosa attached to mesentery

Question 33

appendix histological features

Answer 33

the mucosa has no villi and fewer goblet cells compared to the colon. It has a ring of lymph follicles in the lamina propria.

Question 34

what type of epithelium is present before and after the ano-rectal junction?

Answer 34

Before = simple columnar       After =  stratified squamous

Question 35

what are the main histological features of the liver?

Answer 35

Cells are arranged in sheets and converging towards the central vein At the corner of the lobule connective tissue encloses portal areas which contain blood vessels and ducts (portal tracts or portal triad)

Question 36

what are the main histological features of the pancreas?

Answer 36

Islets of Langerhans composed of clumps of small poorly stained cells Pure serous acini composed of large strongly stained cells Small lobules surrounded by connective tissue septa

Question 37

describe the histological features of the spleen?

Answer 37

The spleen is covered by a dense fibromuscular capsule formed of collagen and elastic fibres with scattered smooth muscle. Branching trabeculae radiate inside the spleen. The parenchyma of spleen is called pulp.

Question 38

what is white pulp?

Answer 38

white pulp is lymphoid tissue that usually surrounds splenic blood vessels as part of the immune system, the white pulp produces white blood cells

Question 39

what is red pulp?

Answer 39

The red pulp is a network of splenic cords (cords of Billroth) and sinusoids (wide vessels) filled with blood, and it is in the red pulp that most of the filtration occurs