Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

GI lectures > structure and function of the alimentary canal > Flashcards

structure and function of the alimentary canal Flashcards

1
Q

What does the GI tract consist of?

A

series of hollow organs between mouth and anus (alimentary canal, separated by sphincters.
also several accessory structures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is the function of the mouth and oropharynx?

A

1) chops up and lubricates food
2) starts carbohydrate digestion (amylase)
3) propels food to oesophagus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the function of the oesophagus?

A

actively propels food from the oropharynx to the stomach via peristalsis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is the function of the stomach?

A

1) storage organ
2) churns food
3) continues carbohydrate digestion and begins protein digestion
4) regulates delivery of chyme to duodenum (via enzyme/churning activity and secretions)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what 3 structures does the small intestine consist of?

A

duodenum (short)
jejunum (longer)
ileum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the function of the small intestine?

A

principal site of digestion and absorption via secretions from small intestine and pancreas
begins fat digestion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what parts of the small intestine are mainly involved in absorption?

A

duodenum and jejunum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the 3 component structures of the large intestine?

A

caecum, appendix and colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the functions of the large intestine?

A

1) contains left over substances
2) colon reabsorbs water and electrolytes
3) delivers fairly solid stool to the rectum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the function of the rectum?

A

storage and expulsion of faeces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the 3 accessory structures?

A

pancreas
salivary glands
liver and gall bladder (hepatobiliary system)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

describe the motility activity of the alimentary canal

A

mechanical activity mainly involving smooth muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe the secretion activity action of the alimentary canal

A

secretion into the digestive tract from itself and accessory structures in response to food.
required for digestion, protection and lubrication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe the digestion activity of the alimentary canal

A

chemical breakdown by enzymatic hydrolysis of complex foodstuffs into smaller absorbable units

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe the absorptive activity of the alimentary canal

A

transfer of absorbable products of digestion from the digestive tract to the blood or lymph
(involves specialised transport mechanisms)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

name the 4 layers of the GI wall from the lumen inwards (7-10 cm)

A

mucosa
submucosa
muscularis externa
serosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is the mucosa?

A

epithelial/endocrine/exocrine cells, lamina propria, muscularis mucosae (thin, circular smooth muscle that changes shape of mucosa so involved in mixing of contents of lumen)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is the submucosa?

A

elastic connective tissue, larger blood and lymph vessels, glands, submucous plexus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what is the muscularis externa?

A

circular muscle layer and longitudinal muscle layer with nerve network in between (myenteric plexus)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is the serosa?

A

connective tissue, squamous cell layer covering it allowing smooth movement of lumen contents over it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what special adaptations exist in the GI wall in the stomach?

A

another oblique smooth muscle layer in muscularis externa

22
Q

what drives GI motility?

A

smooth muscle activity (circular and longitudinal)

23
Q

what parts of the GI tract are skeletal muscle?

under autonomic control

A 
mouth
pharynx
upper oesophagus
external anal sphincter
(rest is smooth)
24
Q

GI smooth muscle acts as a single unit, how does this happen?

A

cells linked via gap junctions allowing electrical continuity between cells and depolarization spreads through all of them as a synchronous wave and they contract as one

25
Q

what drives spontaneous activity across the syncytium (group of SM cells) and how is this modulated?

A

driven by specialised pacemaker cells

modulated by intrinsic (enteric) and extrinsic (autonomic) nerves and numerous hormones

26
Q

what are “slow waves”?

A

rhythmic patterns of depolarization spreading via gap junctions (occurs in stomach and both intestines)

27
Q

how so slow waves determine smooth muscle activity?

A

contraction only occurs if small wave peak reaches threshold and action potential fires
Number/direction/velocity proportional to number of AP’s

28
Q

what drives slow waves?

A

interstitial cells of cajal (ICCs) - pacemaker cells interspersed between muscle layers

29
Q

why does basic electrical rhythm vary along the length of the GI tract?

A

not all slow waves reach threshold

30
Q

what determines whether slow wave amplitude reaches threshold?

A

neuronal stimuli
hormonal stimuli
mechanical stimuli - eg. food
(don’t affect amplitude of wave, just shift starting point of wave)

31
Q

BER of stomach?

A

3 slow waves per min

3 contraction per min when food present

32
Q

BER of small intestine?

A

12 per min in duodenum
8 per min in terminal ileum
propels matter downwards

33
Q

BER of large intestine?

A

8 per min proximal colon
16 per min distal colon
pushes matter back up so more time to reabsorb

34
Q

describe parasympathetic innervation of smooth muscle cells

A

preganglionic fibres synapse with post ganglionic within the enteric NS
excitory = increased gastric/pancreatic/small intestine secretion, blood flow and muscle contraction
Inhibitory = relaxes smooth muscle and sphincters

35
Q

describe sympathetic innervation of smooth muscle cells

A

preganglionic fibres synapse in the prevertebral ganglia (celiac, superior and inferior mesenteric)
Excitory = increased sphincter tone
Inhibitory = decreased motility, secretion and blood flow

36
Q

what 2 plexuses is the enteric nervous system contained within?

A

myenteric (auerbach’s) plexus (motility and sphincters)
Submucous (Meissner’s) plexus (epithelia and blood vessels)
All within the GI tissue

37
Q

what 3 types of neurones of the enteric nervous system co-ordinate muscular, secretive and absorptive activities?

A 
sensory neurons
interneurons (majority)
effector neurons (excitory and inhibitory motor neurones supplying the 2 smooth muscle layers, secretory epithelium, endocrine cells and blood vessels)
38
Q

describe local nerve reflex in the GI tract

A

occurs completely in the walls of the GI tract

39
Q

describe the short nerve reflex of the GI tract

A

intestine-intestinal inhibitory reflex (neurone leaves GI wall, activating sensory neurones exciting sympathetic fibres that inhibit muscle activity in adjacent areas)

40
Q

describe the long nerve reflex in the GI tract

A

neurone goes all the way to CNS (nucleus of vagus in medulla)
gastroileal reflex - brain tells muscles to deficate

41
Q

how does peristalsis happen?

A

before bolus: circular muscle contracts, longitudinal relaxes
after bolus: circulator relaxes, longitudinal contracts

42
Q

What is segmentation?

A

rhythmic contractions of adjacent portions of circular smooth muscle that mix and divide lumen contents
(called haustration in large intestine)

43
Q

what is colonic mass movement?

A

powerful sweeping contraction wave that forces faeces into rectum

44
Q

what is migrating motor complex?

A

powerful sweeping contraction wave from the stomach t the terminal ileum (cleans out small intestine)

45
Q

describe tonic contraction in the sphincters and storage organs

A

high pressure in sphincters

low pressure in storage organs

46
Q

how many sphincters are there in the GI tract?

A

6 (excluding sphincter of Oddi)

47
Q

what are sphincters made of?

A

circular smooth muscle

external anal sphincter and …. are skeletal

48
Q

how do sphincters work?

A

act as one way valves by maintaining a positive resting pressure (tone) relative to two adjacent structures (eg. oesophagus and stomach)

49
Q

describe the function of each sphincter

A

upper oesophageal = entry to oesophagus, open in swallowing, closed on inspiration
lower oesophageal = permits entry of food into stomach then closes to prevent reflux
Pyloric = regulates gastric emptying, prevents reflux of duodenal contents)
ileocaeccal = one way movement of ileum contents to caecum
internal/external anal = control exit of faeces

50
Q

what is gastric outlet obstruction?

A

overactive pyloric sphincter so stomach doesn’t empty into duodenum so backs up causing vomiting

GI lectures (75 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions