BL S8 The Digestive System

Question 1

What is the alimentary canal?

Answer 1

The whole passage along which food passes through the body from mouth to anus during digestion.

Question 2

What are the four layers to the gut wall?

Answer 2

Mucosa
Submucosa
Muscularis externae
Serosa or adventia

Question 3

What are the 3 layers of the mucosa?

Answer 3

Epithelium
Lamina propria
Muscularis mucosae

Question 4

What is found in the lamina propria?

Answer 4

Aggregations of lymph tissue called lymphatic nodules.

Question 5

What is the submucosa made of and what is found in it?

Answer 5

Connective tissue

Glands
Arteries
Veins
Lymphatics 
Nerves

GAVLN

Question 6

What are the 2 layers of the smooth muscle in the muscularis externae and how can they be distinguished between?

Answer 6

Inner circular layer and outer longitudinal layer.

Inner layer - central circular nuclei
Outer layer - elongated cigar shaped

Question 7

What is the structural difference between adventitia and serosa?

Answer 7

Adventitia consists of loose connective tissue only.

Whereas serosa consists of a layer mesothelium and a layer of loose connective tissue.

Question 8

What is the difference in where adventitia is compared to serosa?

Answer 8

Adventitia is found covering retroperitoneal organs, whereas serosa is found covering intreaperitoneal organs.

Question 9

What is the functional difference between adventitia and serosa?

Answer 9

Serosa secretes fluid for lubrication, whereas adventitia is mainly there to bind to structures.

Question 10

Name the visceral and parietal layers of the serosa.

Answer 10

Visceral layer is the loos connective tissue membrane.

Parietal layer is the mesothelium.

Question 11

What are the functions of the GI tract?

Answer 11

Entry point for food
Mechanically disrupt 
Store food
Chemically digest 
Kill pathogens
Move food along tract
Absorb nutrients from resultant solution
Elimination/ defecation - residual waster

Question 12

Define digestion

Answer 12

The conversion of food by physical and chemical disruption into a sterile, isotonic and neutral pH solution from which we will absorb nutrients.

Question 13

What are some properties of saliva?

Answer 13

Enzymes - amylase and lipase - chemically digests
Bacteriostatic - IgA - halts/ prevents bacterial growth
High in calcium - protect teeth and calcium from leeching out
Alkaline - pH buffers
Assist swallowing - lubrication

Question 14

What is physical disruption in the mouth carried out by?

Answer 14

Teeth, tongue and muscle of mastication.

Question 15

Peristalsis works independant of gravity, true or false?

Answer 15

True

Question 16

Where is the fastest GI transport?

Answer 16

Entry -oesophagus

Exit - rectum/ anus

Question 17

What type of epithelium is the in the oesophagus?

Answer 17

Stratified squamous non-keratinised.

Question 18

What type of gland is found within the submucosa of the oesophagus?

Answer 18

Mucus secreting glands

Question 19

As stomach fills with food, its walls relax. What is this called?

Answer 19

Receptive relaxation.

Question 20

How does the stomach seal protect?

Answer 20

Secrets mucus

Question 21

Through the combined action of what does the stomach produced chyme?

Answer 21

Acid- HCl
Physical disruption - 3 muscle layers + rugae
Enzymes - proteolytic enzymes

Acid and enzymes = chemical disruption

Question 22

What can be said about the tonicity of the chyme produced?

Answer 22

Hypertonic

Question 23

Where is chyme from stomach delivered to?

Answer 23

Duodenum

Question 24

What is the function of the gastric rugae?

Answer 24

Allow for expansion of the stomach upon new food contents entering.

Question 25

What is the third layer of smooth muscle in the muscularis externae of the stomach called?

Answer 25

Oblique

Question 26

What four regions are gastric glands compromised of?

Answer 26

Pit Isthmus Neck Base

Question 27

What is found in the pit?

Answer 27

Surface mucous cells

Question 28

What is found in the isthmus?

Answer 28

Stem cells, mucous cells and parietal cells

Question 29

What is found in the neck of a GG?

Answer 29

Enteroendocrine cells, parietal cells and mucous neck cells.

Question 30

What is found in the base?

Answer 30

Parietal, Enteroendocrine cells, chief cells.

Question 31

What are the roles of stem cells?

Answer 31

Divide to populate gland by upward or downward migration.

Question 32

What is the function of parietal cells?

Answer 32

Secrete H+ ions into lumen and HCO3- ions into capillaries from where they will diffuse into the surface mucous cells.

Question 33

What is the function of chief cells?

Answer 33

Release pepsinogens which are converted into pepsin extracellularly. Pepsinogens partially hydrolyse proteins.

Question 34

What is the functions of Enteroendocrine cells?

Answer 34

Secrete hormone gastrin. | The gastric mucosa reacts to this by secreting acid.

Question 35

What are the properties of mucous secreted?

Answer 35

Resistant to degradation from pepsin | Contains HCO3- ions to neutralise the effects of nearby H+ ions - protecting the stomach lining.

Question 36

What is mucus released in response to?

Answer 36

Distension New stomach contents Acid secretion from gastric glands

Question 37

What is aspirin’s effect on surface mucous cells?

Answer 37

Impairs mucous production from these cells, eventually leads to their damage.

Question 38

How will damaged cells within a gastric gland be replaced?

Answer 38

Mitosis of stem cell in the isthmus.

Question 39

How long is the duodenum?

Answer 39

20-25cm

Question 40

How is the duodenum involved in the dilution and neutralisation of chyme?

Answer 40

Brunners gland - secrete bicarbonate rich mucous to neutralise. H20 drawn in from ECF - hypertonic to hypotonic Bile from liver - contains water, alkalis and bile salts - neutralisation and emulsification. Pancreas secrete alkali to neutralise.

Question 41

How is digestion of chyme completed?

Answer 41

Pancreatic, liver and intestinal enzymes which act with bile.

Question 42

What is needed for absorption?

Answer 42

Energy - active process Large SA - gut folded VIII - microvilli Goo blood supply and drainage.

Question 43

What is the length, SA and diameter of the small intestine

Answer 43

22 feet long 1 inch diameter 25m^2

Question 44

What does the duodenum absorb?

Answer 44

Iron

Question 45

What does the Jejunum absorb?

Answer 45

Sugars Amino acids Fatty acids

Question 46

What does the ileum absorb?

Answer 46

Vit B12 Bile acids Remaining nutrients

Question 47

What type of cells line the small intestine?

Answer 47

Simple columnar epithelium, with microvilli. | Goblet cells.

Question 48

What is a lacteal?

Answer 48

A dilated lymphatic capillary vessel.

Question 49

Who long in and wide in the large intestine?

Answer 49

1.2m and 6-9cm wide

Question 50

What are the crypts of Lieberkühn and where are they found?

Answer 50

Intestinal glands | Found in the small and large intestine.

Question 51

What do surface epithelial cells of the large intestine do?

Answer 51

Absorb water and Electrolytes.

Question 52

Where is faeces stored?

Answer 52

In colon.

Question 53

If urge to defecate is not acted upon what will happen?

Answer 53

Rectum contents are returns to the colon via reverse peristalsis.

Question 54

If faeces is stored for too long in the colon what will be the result?

Answer 54

More water will be reabsorbed - harden - constipation.

Question 55

What roles do GI tract bacteria carry out?

Answer 55

Synthesis of vit K, B12 and riboflavin W. Breakdown of primary to secondary bile acids. Convert bilirubin to non-pigmented metabolites.

Question 56

What can problems with fluid balance result in?

Answer 56

Dehydration and electrolyte imbalance.

Question 57

What areas of the GI tract are under somatic control?

Answer 57

Mouth and 1/3 of oesophagus | Last sphincter of anus.

Question 58

Where do the autonomic post-ganglionic neurones form plexuses?

Answer 58

Between muscle layers of muscularis externae - myentric plexus Between submucosa and muscularis externae - submucosal plexus.

Question 59

How is gut under paracrine control?

Answer 59

Histamine - controls acid production in stomach | Vasoactive - substances affect the blood flow in the gut

Question 60

How is the gut under endocrine control?

Answer 60

Range of hormones control Secretion of stomach acid Alkali secretion from liver and pancreas Enzyme secretion

Question 61

Generally the gut is controlled by enzymes it makes itself, true or false?

Answer 61

True.