GI System

Question 1

What is digestion?

Answer 1

The process by which foodstuffs are are degraded to produce smaller molecules which can be absorbed

Question 2

What is absorption?

Answer 2

The processes by which nutrient molecules are absorbed by cells that line the GI tract and enter the bloodstream

Question 3

Where can you find a myenteric plexus?

Answer 3

Through the whole length of the GI tract

Question 4

Where can you find a submucosal plexus?

Answer 4

Only in the small and large intestine

Question 5

Which layers make up the mucosa?

Answer 5

Epithelium, lamina propria, muscularis mucosae

Question 6

What composes the muscularis externa?

Answer 6

An internal layer of circular muscle and an external layer of longitudinal muscle

Question 7

What is the glycocalyx?

Answer 7

The network of proteins on the microvilli

Question 8

What are the 2 routes of cellular transport in the small intestine?

Answer 8

Paracellular and transcellular

Question 9

Which hormones are produced in the stomach/by which cells?

Answer 9

Gastrin (G cells) and somatostatin (D cells)

Question 10

Which hormones are produced in the small intestine/by which cells?

Answer 10

Cholecystokinin (I cells), GIP (K cells), secretin (S cells), somatostatin (D cells)

Question 11

The GI system is contained under which part of the nervous system?

Answer 11

Enteric

Question 12

What happens to the membrane potential during GI smooth muscle contraction?

Answer 12

It oscillates between -40 mV and -60 mV in slow waves - frequency of slow waves determines frequency of muscle contraction

Question 13

What type of contraction do sphincters have?

Answer 13

Long-lasting tonic contractions

Question 14

What sphincters are in the GI tract?

Answer 14

Upper and lower oesophageal, pyloric, ileocaecal, internal and external anal

Question 15

Where is the sphincter of Oddi?

Answer 15

Wraps around the ducts coming from the liver and gallbladder to the duodenum

Question 16

Where do contractions begin in the stomach?

Answer 16

Corpus (body of stomach)

Question 17

Where does mixing/grinding begin in the stomach?

Answer 17

Antrum (just before pylorus)

Question 18

What is the most common type of movement in the small intestine?

Answer 18

Non-propulsive movements (caused by rhythmic contraction and relaxation of muscularis externa)

Question 19

What is the name given to the process of moving GI contents towards the rectum/anus?

Answer 19

Segmentation

Question 20

Which nerves control defection/the rectosphincteric reflex?

Answer 20

Somatic = pudendal nerve, parasympathetic = pelvic nerves

Question 21

What important components are in saliva?

Answer 21

Mucin glycoproteins, lysozyme, a-amylase

Question 22

What is the function of lysozyme in saliva?

Answer 22

Clean and protect cavity of the mouth

Question 23

What is the function of a-amylase in saliva?

Answer 23

Reduce starch into oligosaccharides

Question 24

What type of saliva does the parotid gland secrete?

Answer 24

Serous secretion, rich in a-amylase

Question 25

What type of saliva do the submandibular and sublingual gland secrete?

Answer 25

Seromucous secretion

Question 26

What type of saliva do the minor salivary glands secrete?

Answer 26

Mucous secretion, rich in mucin glycoproteins

Question 27

What effect does acetylcholine have on the acinar and duct cells?

Answer 27

Stimulates fluid/protein secretion in the acinar cells, decreases absorption in the duct cells

Question 28

What effect does noradrenaline have on the acinar and duct cells?

Answer 28

Stimulates protein secretion in the acinar cells, stimulates bicarbonate secretion in the duct cells

Question 29

Is there any hormonal control of salivary gland secretion?

Answer 29

No!

Question 30

Which branch of the autonomic nervous system stimulates saliva secretion?

Answer 30

Both sympathetic and parasympathetic branches

Question 31

Where is B12 absorbed in the GI tract?

Answer 31

Stomach

Question 32

What is the pH of gastric secretions?

Answer 32

0.9-1.5

Question 33

What are the 5 main components of gastric secretions?

Answer 33

HCl, pepsins, intrinsic factor, mucus and bicarbonate ions

Question 34

Which cell type secretes bicarbonate ions into the stomach?

Answer 34

Surface epithelial cells

Question 35

What do the mucous neck cells of the stomach secrete?

Answer 35

A protective mucus

Question 36

What do the parietal cells of the stomach secrete?

Answer 36

HCl and intrinsic factor

Question 37

Which cell type secretes pepsinogens into the stomach?

Answer 37

Chief cells

Question 38

Where are the G cells (gastrin-producing) in the stomach?

Answer 38

Antrum region

Question 39

What is the secondary role of pepsin in the stomach?

Answer 39

Stimulate production of HCl

Question 40

How is bicarbonate and mucus release regulated in the stomach?

Answer 40

Via acetylcholine and prostaglandins

Question 41

What provides anatomical protection for the apical cells of the stomach?

Answer 41

Impermeability to H+ and the presence of tight junctions

Question 42

What provides physiological protection for the apical cells of the stomach?

Answer 42

Thick layer of mucus impregnated with bicarbonate ions (mucus gel neutralisation zone)

Question 43

Which agonist is involved in neuronal control of HCl secretion?

Answer 43

Acetylcholine and stimulation of ECL cells (indirect)

Question 44

Which agonist is involved in hormonal control of HCl secretion?

Answer 44

Gastrin (secretion by G cells) stimulation of ECL cells (indirect)

Question 45

Which agonist is involved in paracrine control of HCl secretion?

Answer 45

Histamine from ECL cell to activate cAMP within cell

Question 46

Which nerve controls the cephalic phase of secretion?

Answer 46

Vagal nerve (entirely dependent)

Question 47

What pH are pancreatic secretions?

Answer 47

7.8-8.4

Question 48

Which type of digestive enzymes are released in an inactive form?

Answer 48

Proteases (trypsin, chymotrypsin, carboxypeptidases)

Question 49

Where is cholecystokinin released from?

Answer 49

I cells in the small intestine

Question 50

What is the effect of parasympathetic/enteric Ach release on pancreatic acinar cells?

Answer 50

Stimulation of enzyme release

Question 51

How is NaCl secretion by the pancreatic acinar cells regulated?

Answer 51

Ach (neuronal) and CCK both increase intracellular calcium concentration

Question 52

What is the most powerful stimulus for bicarbonate secretion from the pancreas?

Answer 52

Secretin

Question 53

Which enzyme converts trypsinogen into trypsin?

Answer 53

Enteropeptidase

Question 54

What is produced in the hepatocytes and stored in the gallbladder?

Answer 54

Bile salts, cholesterol, phospholipids - all together form a mixed micelle

Question 55

What happens to bile acids once they have been utilised?

Answer 55

Absorbed by ileum then returned to the liver where they are taken up by hepatocytes (sodium-driven process)

Question 56

What are the main 3 differences between the small and large intestines?

Answer 56

Large intestine does not have villi and is not involved in nutrient reabsorption; large intestine actively secrets K+ but small does not

Question 57

What is the maximal absorptive capacity of the small intestine?

Answer 57

15-20L per day!!!

Question 58

Which type of small intestine cell secretes salts?

Answer 58

Crypt-lining epithelial cells

Question 59

Which type of small intestine cell absorbs salt/glucose?

Answer 59

Villus-lining epithelial cells

Question 60

How is starch broken down in the small intestine?

Answer 60

Broken down by a-amylase into maltose, maltotriose and a-limit dextrins

Question 61

How is maltose broken down in the small intestine?

Answer 61

Hydrolysed by maltase into 2 isolated glucose units

Question 62

How is maltotriose broken down in the small intestine?

Answer 62

Hydrolysed by maltase into 1 glucose and 1 maltose

Question 63

How is lactose broken down in the small intestine?

Answer 63

Hydrolysed into 1 unit glucose and 1 galactose

Question 64

How is sucrose broken down in the small intestine?

Answer 64

Hydrolysed by sucrase into 1 fructose and 1 glucose

Question 65

What is the SGLT1?

Answer 65

Sodium-coupled glucose transporter, transports glucose and galactose across the apical membrane of the SI

Question 66

What is the GLUT5?

Answer 66

Glucose-transporter 5, transports fructose across apical membrane using facilitated diffusion (small intestine)

Question 67

What is GLUT2?

Answer 67

Glucose-transporter 2, transports glucose, galactose and fructose across the basolateral membrane (small intestine) via facilitated diffusion

Question 68

How many types of amino acid transport are there across the apical membrane?

Answer 68

7