Physiology of the small intestine and accesory organs

Question 1

What are exocrine cells in the pancreas

Answer 1

• accessory organ to digestion
• secretion of enzyme rich fluid into duodenum
• Break down all categories of digestible food

Question 2

what are endocrine glands in the pancreas?

Answer 2

• release hormones into bloodstream that affect carbohydrate metabolism
• insulin
  -glucagon
• somatostatin

Question 3

What is the structure of the pamcreas?

Answer 3

• similar to salivary glands
  acinar cells secrete enzymes and fluid into duct system
• the pancreatic duct fuses with the bile duct on entry to duodenum

Question 4

what is the aqueous component of pancreatic juices ?

Answer 4

• 200-800ml secreted a day
• rich in bicarbonate
• helps to neutralise acid chyme
• secretion stimulated by secretin

Question 5

what is the proteolytic enzyme component ?

Answer 5

Trypsin, chromotrptins and carboxypeptidases

Secreted in active form, activated by the duodenum by enterokinase

Question 6

what does pancreatic amylase do?

Answer 6

breaks down starch - secreted in active form

Question 7

what does the lipolytic enzyme in the pancreas do?

Answer 7

Fat digestion
Lipase - secreted in active form
Colipase, cholesterol esterase, phospholipase

Activated by trypsin in the duodenum

Question 8

what is the control of pancreatic secretions?

Answer 8

• Nervous and hormonal control
• Nervous reflex involves medulla and vagal innervation (cephalic phase)
• gastrin release in response to stomach distension (gastric phase)
• secretin and cck secreted by mucosa in response to presence of chyme in the duodenum (intestinal phase)

Question 9

what is pancreatitis ?

Answer 9

pancreatic enzymes are activated in the pancreas, causing them to attack the organ itself
- Acute (can resolve) or Chronic (tissue is destroyed and scarring develops)

Question 10

what are causes of pancreatitis?

Answer 10

gallstones ( pancreatic duct and bile duct fuse so blockage may affect the other)

Alcohol

Idiopathic

Question 11

what are some function of the liver?

Answer 11

• processing digested food from intestine
• manufacturing of bile
• storage
• metabolism (breaks down stored glycogen, fat or protein to glucose)

Question 12

what is the structure of the liver?

Answer 12

• hepatic (liver) cells arrange in radial pattern around central vein
• hepatocytes make up functional units called lobules
• lobules form the 2 main lobes of the liver

Question 13

what does hepatic blood supply do?

Answer 13

• receives double blood supply (oxygenated from hepatic artery, deoxygenated from portal vein)

Question 14

what does hepatic cells do?

Answer 14

Extract oxygen and most nutrients
Detoxify or story poisons and drugs
Secrete products (except bile) in hepatic vein

Question 15

what are the two characteristics of bile?

Answer 15

• excretory product of liver metabolism
• a digestive secretion

Question 16

What does bile salts do?

Answer 16

emulsifies fats into small droplets that enables them to be absorbed and digested more effectively

Question 17

what are bile pigments called and what do they do?

Answer 17

Bilirubin - yellow/brown give faeces their colour (absorbed by the blood)

Salts, cholesterol and pigments secreted by liver cells (hepatocytes)

Question 18

what does bicarbonate ions in the bile do?

Answer 18

neutralises acid chyme

it is secreted by epithelial lining bile ducts

Question 19

what happens to most bile salts and emulsifying?

Answer 19

they are recirculated and reabsorbed
5% is synthesised and lost in faeces

Question 20

what does the gall bladder do?

Answer 20

stored and concentrates bile by extracting water and ions. Can lead to increased insoluble cholesterol levels

Question 21

how does bile enter the gallbladder?

Answer 21

by the cystic duct when the SI is empty

Question 22

when does ejection of bile into the duodenum occur?

Answer 22

when protein or fat-rich chyme enters duodenum
- causes CCK release
- CCK causes gallbladder to contract and sphincter of oddi to relax thus allowing bile to enter the duodenum

Question 23

what are gallstones?

Answer 23

crystalline deposit that accumulates when there is too much cholesterol and not enough bile salts

Question 24

how can gallstones be treated?

Answer 24

can be dissolved
if severe gall bladder can be removed (cholecystectomy)

Question 25

what is jaundice a symptom of gallstones?

Answer 25

Stones can block the common bile duct which causes increased levels of bilirubin in the blood plasma causing discolouration of the skin

Question 26

what are the three parts of the small intestine?

Answer 26

duodenum
jejunum
ileum

Question 27

what is the small intestines mucosa consisting of?

Answer 27

epithelium (enterocytes)
lamina propia
muscularis mucosae

Question 28

What types of muscle causes the small intestine to contract

Answer 28

Smooth muscle (longitudinal and circular )

Question 29

what are the components of the enteric NS

Answer 29

Myeteric plexus
submucosal plexus

Question 30

what is the neutransmitter for parasympathetic and sympathetic signals?

Answer 30

para - acetylcholine
symp - noradrenaline

Question 31

what does the submucosa contain and what does it do?

Answer 31

contains brunner’s glands to secrete alkaline mucous to protect the intestinal wall and neutralise acid chyme

Question 32

what are lacteals?

Answer 32

components of the lymphatic system for fat digestion

Question 33

what is the villi’s function?

Answer 33

increase SA for absorption
Microvilli further increases this

Question 34

what is the components of a villus?

Answer 34

• arteriole and capillary bed (oxygenated blood)
• venule (nutrients from villi)
  -lymphatic (fatty end stage products)

Question 35

what is the combination required for digestion in the SI

Answer 35

pancreatic juice
bile
intestinal juice

Question 36

how is carbohydrates digested?

Answer 36

• starch converted to disaccharides by pancreatic amylase
• disaccharides converted to monosaccharides by glycosidase
• monosaccharide is absorbed in the epithelium

Question 37

what are polypeptides arriving from the stomach catabolised by?

Answer 37

trypsin and chymotrypsin

Question 38

how is glucose and galactose absorbed?

Answer 38

into epithelial cells by co-transport with Na via sodium glucose transporters
-leave epithelial cell and enter blood by facilitated diffusion via glucose transporters

Question 39

how is peptides absorbed in the SI

Answer 39

uptake into epithelial cell thought to be linked with H+ influx
Broken down to constituent amino acids inside epithelial cell

Question 40

how are amino acids absorbed in the SI?

Answer 40

uptake into epithelial cells by Na+ dependent co-transport
-leave by facilitated diffusion

Question 41

when do bile salts remain in the lumen of gut until?

Answer 41

until terminal ileum and then re-cycled into enterohepatic circulation

Question 42

what are cylomicrons?

Answer 42

when lipids(triglycerides) accumulate in vesicles of smooth ER of epithelial cell and leave by fusion with plasma membrane

Question 43

how do chylomicrons leave the intestines?

Answer 43

leave in lymph since they are too largs to enter the circulation immediately

Question 44

what is interstitial spaces ?

Answer 44

spaces between cells/organs

Question 45

what is lymphatic circulation due to?

Answer 45

muscular movements with slow contractile action of smooth muscle in walls of lymphatics pushing lymph along by peristalsis