SI and pancreas anatomy

Question 1

Describe the layers of the SI

Answer 1

Mucosa:
- epithelial layer
- lamino propria
Submucosa
Tunica muscularis
Serosa

Question 2

Describe the anatomy and function of the mucosa of the SI

Answer 2

Single epithelial layer:
- semi-permeable
- secretion and absorption
- protection
- mucous covered
Lamina propria:
- loose connective tissue
- immune cells
Crypts of Lieberkuhns
Mucosa folds to creates dams to slow flow of chyme

Question 3

Describe the anatomy and function of the submucosa of the SI

Answer 3

structural support
BVs
lymphatics
nerves
fine smooth muscle layer that projects into lamina propria (muscularis mucosae) that alters folding and ‘pumps’ villi up and down

Question 4

Describe the anatomy and function of the tunica muscularis of the SI

Answer 4

main smooth muscle
circular and longitudinal layers
provides motility
nerve cell layers control the contractions

Question 5

Descrive the function of the serosa of then SI

Answer 5

strong
protective, supportive outer layer

Question 6

Label the SI wall

Answer 6

Question 7

What adaptations increase the SA of the SI

Answer 7

ridges/folds
villi
microvilli

Question 8

Describe the function of the crypts of lieberkuhns in the SI

Answer 8

intestinal glands/crypts
contain a stem cell region which produces immature enterocytes and other gut cells

Question 9

What is the function of mature enterocytes in the SI?

Answer 9

Found on villi
absorb nutrients:
- carbs
- AAs
- lipids
- vits
- minerals

Question 10

What is the function of lacteals in the SI wall?

Answer 10

blind-end lymphatic capillaries
transport emulsified fats (As chylomicrons) into GIT lymphatic drainage

Question 11

What is the function of blood capillaries in the lamina propria of the SI?

Answer 11

have large fenestrations so plasma proteins (inculding serum albumin) can move into interstitial space

Question 12

What is the function of the Brunner’s glands in the duodenum?

Answer 12

tubular sub-mucosal glands
Produce serous or mucous secretion
Secretion protects duodenal epithelium from incoming gastric acid and provides alkaline conditions for intestinal enzymes

Question 13

What joins the caecum and ileum?

Answer 13

ileocaecal fold
ileocaecal sphincter

Question 14

How do you identify the ileum?

Answer 14

Double mesentery
Double blood supply from caecum and colon
has mesenteric and antimesenteric blood vessels

Question 15

What are the 6 cells types in the SI?

Answer 15

Question 16

What is the function of entero-endocrine cells?

Answer 16

Dark basal granules
secrete peptide hormones and CCK

Question 17

What is the function of paneth cells in the SI?

Answer 17

apical granules
innate mucosal defences (defensins and lysozymes)
found at bottom of crypts

Question 18

What is the function of M-cells in the SI?

Answer 18

APC that covers Peyer’s patches

Question 19

What is the function of tuft cells in the SI?

Answer 19

make links with immune system

Question 20

Describe the formation and distribution of cells in the SI

Answer 20

stem cell zone at neck of crypts
most cell types migrate up villi:
- enterocyte
- goblet cell
- endocrine cell
Paneth cells migrate down into crypts

Question 21

How do enterocytes work?

Answer 21

smooth endoplasmic reticulum allows intracellular transport of nutrients
pinocytosis into enterocytes allows foreign materials to enter as vesicles
vesicles fuse with enzyme-packed intracellular lysosomes
tight junctions prevent leakage

Question 22

Label the villus of the SI

Answer 22

Question 23

What are the mature enterocyte brush border enzymes?

Answer 23

integral membrane enzymes
peptidases
CHO hydrolases (lactase, maltase, sucrose)

Question 24

What is the function of entero-endocrine cells?

Answer 24

sample intestinal lumen and react
found along entire GIT epithelium
chemosensors at the luminal surface
Have links with immune system
open type - open into lumen
Closed type - cell sits on basement membrane, no extension to mucosal surface

Question 25

What is the function of paneth cells in the SI

Answer 25

equids and bovids produce anti-microbial defensin peptides keep crypt clear of high bacterial count

Question 26

What is GALT?

Answer 26

gut associated lymphoid tissues

Question 27

Describe the anatomy and function of the Peyer's patches

Answer 27

Raised ovoid areas in the mucosa of the ileum always in antimesenteric mucosa lots of macrophages and lymphocytes Covered by M-cells which transport antigens to lymphocytes and macrophages Reactive to changes in gut flora - immune responses

Question 28

Describe the anatomy of lymphoid follicles in the SI

Answer 28

aggregations of lymphocytes and macrophages within lamina propria No contact with lumen M-cells over them in epithelial boundary

Question 29

Where are lymph nodes found in the SI?

Answer 29

within the mesentery

Question 30

Which section of SI is this?

Answer 30

duodenum

Question 31

Which section of the SI is this?

Answer 31

jejunum

Question 32

Which section of the SI is this?

Answer 32

ileum

Question 33

What is the function of M-cells in the SI?

Answer 33

special epithelial cells that cover Peyer's patches direct contact with ingesta (no mucous layer) folded apical surface increases SA lymphocytes and macrophages in indentation on basal surface transport antigens from lumen to immune cells

Question 34

What is the function of Tuft cells in the SI?

Answer 34

long 'fingers' project sideways into neighbouring epithelial cells and into luminal space modulate responses against protists and metazoa (multicellular endoparasites)

Question 35

Where is the pancreas found?

Answer 35

duodenal flexure

Question 36

Why do you need to be careful handling the pancreas in surgery?

Answer 36

heavy handling can lead to pancreatic enzymes being released into the pancreas leading to autolysis (breaking down itself)

Question 37

Why is there high conc of pancreatic hormones in the liver?

Answer 37

venous drainage of pancreas via hepatic portal vein into liver

Question 38

What are the secretions of the pancreas?

Answer 38

dual function: exocrine: - digestive enzymes - alkaline fluids endocrine: - insulin - glucagon - somastostatin - pancreatic polypeptide

Question 39

How is the pancreas stimulated?

Answer 39

duodenum entero-endocrine cells sense acidic chyme secretin release acts on pancreatic ducts epithelial cells in pancreas ducts produce bicarbonate and water flush acinar enzymes into SI lumen

Question 40

What are Islets of Langerhans and what types are there?

Answer 40

enteroendocrine cells in the pancreas alpha cells - glucagon beta cells - insulin delta cells - somatostatin PP cells - pancreatic polypeptide - epsilon cells - ghrelin

Question 41

What GIT structures does the coeliac artery supply?

Answer 41

liver stomach rumen spleen duodenum pancreas

Question 42

What GIT structures does the cranial mesenteric artery supply?

Answer 42

duodenum pancreas jejunum ileum caecum large colon

Question 43

What GIT structures does the caudal mesenteric artery supply?

Answer 43

part of descending colon rectum

Question 44

What are the branches of the coeliac artery?

Answer 44

left gastric hepatic: - right gastric Splenic: - splenic branches - short gastric

Question 45

What local nerve networks control the smooth muscles of the GIT?

Answer 45

Meissner's plexus - submucosa Auerbach's plexus - between smooth mm layers

Question 46

Which nerves supply sensory info to the brain from the GIT?

Answer 46

mechanosense and chemosense - vagus pain - sympathetics

Question 47

Describe the sympathetic pathways to the gut

Answer 47

Fibres run through vagus nerve => dorsal vagal trunk => coeliac and mesenteric ganglion => along BVs => gut Sacral part of parasympathetic NS: pelvic nerve forms retroperitoneal plexus which supplies descending colon and rectum

Question 48

What are the autonomic ganglion involved in innervation of the GIT?

Answer 48

sympathetic synapses: paravertebral ganglion Parasympathetic: prevertebral ganglion (coeliac and cranial mesenteric ganglion = solar plexus)