Small & Large Intestine Anatomy & Histology

Front 1

Where does the small intestine extend from?

Back 1

pylorus to ileocaecal junction

Front 2

What embryological origin does the SI predominantly have?

Back 2

Midgut

Front 3

Name the 3 SI regions

Back 3

- duodenum
- jejunum
- ileum

Front 4

How does the SI have a maximised surface area?

Back 4

- long 6-7m
- circular folds (valvulae conniventes or plivae circularis)
- villi
- microvilli

Front 5

What classification of epithelium does the SI have?

Back 5

simple columnar epithelium

Front 6

What is a 'brush border'?

Back 6

When villi have microvilli on their surface to maximise surface area.

Front 7

What are crypts of Lieburkuhn?

Back 7

Tubular intestinal glands that extend from the muscularis mucosae, through the lamina propria, & open at the base of the villi

Front 8

Name 6 different cells of the SI

Back 8

enterocytes, goblet cells, paneth cells, enteroendocrine cells, stem cells, lymphocytes

Front 9

What is the functions of enterocytes?

Back 9

principally absorptive but also secretory

Front 10

What is the function of goblet cells?

Back 10

secrete mucous

Front 11

What is the function of enteroendocrine cells?

Back 11

produce peptide hormones e.g. secretin & cholecystokinin (CCK)

Front 12

what is the function of paneth cells & where are they found?

Back 12

Phagocytic cells which produce antibacterial lysozyme, present in the crypts of Lieberkuhn

Front 13

Where are stem cells found in the stomach & what do they allow?

Back 13

Crypts of Lieberkuhn - allow regeneration of epithelial cells every 3-4 days

Front 14

What role do lymphocytes play in the SI?

Back 14

immune surveillance & protection

Front 15

What 2 structures define the ends of the midgut?

Back 15

- entry of common bile duct into duodenum
- left colic flexure

Front 16

What is the difference between pylorus & duodenum?

Back 16

mucous membrane changes from gastric to intestinal type, where intestinal membrane has villi

Front 17

What forms the pyloric sphincter?

Back 17

inner circular layer of muscle is thickened

Front 18

What is the main blood supply to the SI?

Back 18

superior mesenteric artery, with jejunal, ileal & ileocolic branches

Front 19

Which part of the SI has contribution from the coeliac trunk?

Back 19

duodenum

Front 20

How does nutrient-rich blood get from the SI to the liver?

Back 20

the superior mesenteric vein via the portal vein

Front 21

What marks the foregut/midgut interface?

Back 21

Major duodenal papilla

Front 22

What neutralises acidic stomach chyme in the SI?

Back 22

Duodenum submucosa contains compound tubular glands - Brunner's glands - which secrete alkaline mucous

Front 23

Where does the jejunum begin & end?

Back 23

duojejunal junction & ileum

Front 24

Are the duodenum & jejunum retro or intra peritoneal?

Back 24

duodenum - retroperitoneal
jejunum - mesentery, intraperitoneal

Front 25

What is important about the terminal ileum?

Back 25

Important for absorption of vitamin B12 & bile salts

Front 26

Briefly describe coeliac disease, what part of the SI it affects & symptoms.

Back 26

Caused by intolerance to proteins in cereal crops, leads to inflammation & damage to proximal SI mucosa, destroying villi. This reduces surface area leading to malabsorption & diarrhoea

Front 27

briefly describe Crohn's disease, what part of the SI it affects & clinical features/symptoms.

Back 27

Patchy. chronic inflammation that can affect any of the GI tract, but common in the terminal ileum due to high conc of lymphoid follicles (Peyer's patches). Inflammation is transmural & clinical features include malabsorption, strictures, fistulae.

Front 28

Why are ulcers common in the first part of the duodenum?

Back 28

acidic chyme enters this area

Front 29

What are the 4 regions of the large intestine?

Back 29

caecum (+ appendix)
colon
rectum
anal canal

Front 30

What embryological origin does the LI have?

Back 30

midgut & hindgut

Front 31

What is the key function of the LI?

Back 31

absorbs water & forms faeces

Front 32

What are 4 distinctive features of the LI?

Back 32

taenia coli
appendices apiploicae
haustrations
semilunar folds

Front 33

what are taenia coli & where are they usually?

Back 33

3 thickened bands of longitudinal muscle, usually in caecum & colon

Front 34

What are appendices epiploicae?

Back 34

fatty tags found mostly on outside of colon

Front 35

What are haustrations?

Back 35

visible sacculations of the colon

Front 36

What are semilunar folds?

Back 36

incomplete folds on smooth mucosal surface of LI

Front 37

Describe LI epithelium

Back 37

simple columnar epithelium with no villi

Front 38

what is the difference between crypts of Lieberkuhn in SI & LI?

Back 38

LI only have mucous-secreting cells, no Panth cells

Front 39

What is the difference between the outer longitudinal muscle layers of the SI & LI?

Back 39

SI - continuous
LI - discontinuous, organised into 3 bands - taenia coli

Front 40

What is intestinal venous drainage?

Back 40

small & large intestine venous drainage is via branches to the portal vein

Front 41

What is the surface marking for the base of the appendix?

Back 41

McBurney's point - 1/3 of the way along a line connecting the anterior superior iliac spine (ASIS) to the umbilicus

Front 42

Which parts of the colon are intra- & retro peritoneal?

Back 42

ascending & descending - retro
transverse & sigmoid - intra

Front 43

Where is the transverse colon & why is it important?

Back 43

between hepatic & splenic flexures, distal to ascending & proximal to descending colon, & it is the midgut-hindgut interface

Front 44

where is the midgud-hindgut interface?

Back 44

transverse colon

Front 45

how does the rectum differ to the colon?

Back 45

no taenia coli

Front 46

What does the ampulla of the rectum have & what is their name?

Back 46

3 transverse folds - valves of Houston

Front 47

what is the internal anal sphincter formed by?

Back 47

inner circular layer of muscle

Front 48

what is the external anal sphincter formed by>

Back 48

skeletal muscle

Front 49

what happens at the anal transition zone?

Back 49

endoderm meets ectoderm, & simple columnar epithelium changes to stratified squamous

Front 50

how does the stratified squamous epithelium of the anus differ to that of the oesophagous?

Back 50

it is keratinised

Front 51

what are 2 complications of appendicitis?

Back 51

perforation & peritonitis

Front 52

describe ulcerative colitis & where it affects

Back 52

type of IBD - diffuse chronic inflammation. Affects only the mucosa of the LI & presents as malabsorption of water (diarrhoea) & ulceration (bleeding)

Front 53

Describe diverticular disease.

Back 53

Outpouchings of mucosa into the wall of colon, predominantly in the descending & sigmoid colon

Front 54

What parts of the intestine are mobile (have mesentery) & which are fixed (retroperitoneal)

Back 54

mesentery: jejunum, ileum, appendix, trans colon, sigmoid colon
retroperitoneal: duodenum, ascending & descending colon, caecum, rectum