L11 - Intestines

Question 1

Jejunual artery

Answer 1

Located in left upper quadrant
Thick intestinal walls
Longer vasa recta (straight arteries)
Less arcades (arterial loops)

Question 2

Ileal artery

Answer 2

Located in lower right quadrant
Thin intestinal walls
Shorter vasa recta
More arcades

Question 3

Right colic artery

Answer 3

Ascending colon

Question 4

Middle colic artery

Answer 4

Transverse colon

Question 5

Ileocolic artery

Answer 5

In the right iliac fossa
Appendix
Terminal ileum and caecum

Question 6

Marginal artery

Answer 6

Sum of all the distal branches of the SMA where they anastamose

Question 7

Venous drainage of git

Answer 7

The IMV joins the splenic vein

Where the SMV and splenic vein meet, forms the portal vein that drains into the IVC

Question 8

Chyme in intestines

Answer 8

Isotonic
Neutral
Digestion nearly complete

Question 9

Adaptations of the small intestines

Answer 9

Villi
Microvilli - brush border
Plicae circulares
Segmentation shuttling - controlled segment contraction

Question 10

Intestinal epithelia

Answer 10

Enterocytes- tall columnar (absorption)
Goblet cells - produces mucus
Enteroendocrine cells - produce hormones

Crypts of Lieberkuhn (gland)
- stem cells

Question 11

Crypts of Lieberkuhn

Answer 11

• stem cells at base - mature as they migrate to surface - high turnover of epithelial cells
• Paneth cells at base - prodeuce antimicrobial peptides and protects stem cells

Question 12

Monosaccharides

Answer 12

Only monoasaccharides can be absorbed

• Glucose - only enters with Na+
• Galactose
• Fructose

Question 13

Fibre

Answer 13

Binds to bile salts so they are excreted.

Therefore, more bile salts must be made from bile acids in the liver using cholesterol

Partially digested by bacteria in the colon providing nutrients

Question 14

Common dietary carbhydrates

Answer 14

Starch
Lactose - milk
Sucrose - cane sugar

Question 15

Amylose

Answer 15

Straight chains of glucose

alpha 1-4 glycosidic bonds only

Question 16

Amylopectin

Answer 16

Branched chains of glucose

alpha 1-4 glycosidic bonds and alpha 1-6 glycosidic bonds (branched)

Question 17

Starch digestion

Answer 17

Starch is made of amylose and amylopectin.

Alpha 1-4 glycosidic bonds broken down by salivary and pancreatic amylase producing:

• maltose in amylose
• alpha dextrins in amylopectins

Isolmaltase breaks the brnachedalpha 1-6 glycosidic bonds

Question 18

Maltose

Answer 18

glucose + glucose

Question 19

Alpha dextrins

Answer 19

Branched sub unit containing 4 glucose

Question 20

Lactose

Answer 20

Glucose + galactose

Broken down by lactase

Question 21

Lactose intolerant

Answer 21

Not enough lactase when older

Lactose remains in gut drawing water in to the gut causing diarrhoea

Lactose is fermented in the gut producing gas - flatulence and bloating

Question 22

Sucrose

Answer 22

Glucose + fructose

Broken down by sucrase

Question 23

Enterocyte Na+/K+ ATPase

Answer 23

On the basolateral surface of the enterocyte.

Maintains a low Na+ conc inside the cell establishing a conc gradient

Question 24

Monosaccharide absorption

Answer 24

SGLT1 :
On lumenal surface
Absorbs Na+ and glucose/ galcatose into the enterocyte from the lumen

SGLT2 - Transports monosaccharides into the blood from the enterocyte

GLUT5 - Transports fructose from the lumen t the enterocyte via facilitated diffusion

Question 25

Pepsin

Answer 25

Pepsinogen released from chief cells Activated in the stomach at pH 2-3 to pepsin Pepsin breaks down proteins into oligopeptides which are transported to the small intestines

Question 26

Protein digestion in the small intestines

Answer 26

Pancreas releases protease zymogens: - trypsinogen - chymotrypsinogen - proelastase - procarboxypeptidase A and B

Question 27

Enterokinase

Answer 27

Converts trypsinogen to trypsin

Question 28

Exopeptidases

Answer 28

Produce dipeptides or amino acids Break bonds at the end of polypeptides - procarboxypeptidase A and B

Question 29

Endopeptidases

Answer 29

Produce shorter polypeptidases Break bonds in the middle of polypeptidases - trypsinogen - chymotrypsinogen - proelastase

Question 30

Trypsin

Answer 30

Trypsinogen is converted to trypsin by enterokinase on epithelial cells Trypsin activates other zymogens in gut lumen

Question 31

Brush border

Answer 31

- Partially digested polypeptides can be absorbed by the enterocyte via the peptide transporter 1 - Amino acids are absorbed from the lumen into the enterocyte using an Na+/ amino acid co transporter - The dipeptides in the enterocyte are broken down by cytosolic peptidases into amino acids - Amino acids are transported out of the cell into the blood

Question 32

Water uptake in large intestines

Answer 32

Large intestines contain Na+ channels induced by aldosterone

Question 33

Osmosis

Answer 33

Occurs paracellularly via tight junctions and transcellularly

Question 34

Oral rehydration

Answer 34

MIxture of glucose and salt for maximum water uptake

Question 35

Water secretion

Answer 35

Driven by chloride movement predominantly 1. Chloride enters the crypt epithelial cell from blood via the NKCC1 2. cAMP levels increases inside the cell 3. cAMP activates CFTR so Cl- are secreted into the lumen 4. Na+ is driven into the lumen via tight junctions 5. Osmotic gradient is created so water flows into the lumen

Question 36

vit B12 deficiency causes

Answer 36

Pernicious anaemia Hypochlorhydria - inadequate stomach acid Veganism Inflammatory disorders of the ileum e.g. Chron's

Question 37

Irritable bowel syndrome

Answer 37

``` Abdominal pain Bloating Flatulence Diarrhoea Constipation Rectal urgency ```

Question 38

Who does IBS affect commonly

Answer 38

Females 2:1 Young adults 20 - 40s People with psychological disorders such as depression and anxiety

Question 39

Coeliac disease

Answer 39

Immunological response to the gliadin fraction of gluten - Damages mucosa of intestines - Absence of intestinal villi - Hypertrophy and lengthening of crypts - Lymphocyte infiltration of epithelium and lamina propria - Impaired digestion and malabsorption

Question 40

Where is gluten found

Answer 40

Wheat Rye Barley

Question 41

Coeliac synptoms

Answer 41

Diarrhoea Weight loss Flatulence Abdominal pain Anaemia - impaired iron absorption Neurological symptoms - hypocalcaemia

Question 42

Investigations for coeliac's

Answer 42

Bloods - IgA to endomysium - tissue transglutaminase Upper GI endoscopy and biopsy (duodenum) - reduced villi - mucosal pathology

Question 43

Treatment of coeliac disease

Answer 43

Strict gluten free diet