Brainscape's Knowledge GenomeTM

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


See full index

GI > introduction to structure, functions and control of the alimentary canal > Flashcards

introduction to structure, functions and control of the alimentary canal Flashcards

1
Q

function of mouth and pharynx

A

chops and lubricates food, starts carbohydrate digestion and delivers food to the oesophagus

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

oesophagus

A

propels food to stomach

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

stomach

A

stores/churns food, continues carbohydrate digestion, initiates protein digestion, regulates delivery of chyme to duodenum

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

small intestine

A

(duodenum, jejunum, ileum) principal site of digestion and absorption of nutrients

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

large intestine

A

(caecum, appendix, colon)

colon reabsorbs fluids and electrolytes, stores faecal matter before delivery to rectum

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

rectum anal canal and anus

A

regulated expulsion of faeces

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

accessory structures are …

A

salivary glands
the pancreas
the liver and gall bladder
(hepatobilliary system)

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

what consists of the generalised structure of the digestive wall

A

mucosa, submucosa, muscular externa, serosa

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

mucosa

A

> mucous membrane (epithelial, exocrine gland and endocrine gland cells)
lamina propria (neuroendocrine cells)
muscular mucosae (gut motility)

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

submucosa

A

connective tissue
larger blood and lymph vessels
glands
submucous plexus (neurone network)

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

muscular externa

A 
circular, longitudinal muscle layer 
myenteric plexus (neurone network)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

serosa

A

connective tissue

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

main functions of the alimentary canal

A

motility
secretion
digestion
absorption

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

motility

A

mechanical activity mostly involving smooth muscle - skeletal muscle at mouth, oesophagus and others

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

secretin

A

into the lumen of the digestive tract occurs from itself and accessory structure in response to the presence of food,
hormonal and neural signals
this is required for 1) digestion 2) protection 3) lubrication

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

digestion

A

chemical breakdown of enzymatic hydrolysis of complex foodstuffs to smaller, absorbable units

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

absorption

A

transfer of the absorbable products of digestion - with water electrolytes and vitamins - from the digestive tract to the blood or lymph

18
Q

how does GI motility work

A

> circular muscle contraction ie the lumen becomes narrower and longer
longitudinal muscle contraction ie the intestine becomes shorter and fatter
muscular mucosae contraction ie change in absorptive and secretory area of mucosa (folding), mixing activity
*mostly due to the activity of smooth muscle but skeletal muscle is important in features such as the mouth pharynx external anal sphincter and upper oesophagus

19
Q

explain electrically coupled smooth muscle in GI tract

A

> adjacent smooth muscle cells are couples by gap junctions - electrical currents flow from cell to cell
hundreds of cells are depolarised and contract at the same time as a synchronous wave (ie a single unit of smooth muscle as opposed to multiunit smooth muscle)
spontaneous activity across the coupled cells is driven by specialised pacemaker cells and is modulated by: intrinsic (enteric) and extrinsic (autonomic) nerves and
numerous hormones
in the stomach, small, and large intestine spontaneous electrical activity occurs as slow waves - rhythmic patterns of membrane depolarization and repolarization that spread from cell to cell via gap junctions

20
Q

what is the purpose of slow wave electrical activity

A

determines: frequency, direction and velocity of rhythmic contractions

21
Q

how does slow wave electrical activity work?

A

it is driven by the interstitial cells of Cajal - pacemaker cells located largely between the circular and longitudinal muscle layers
>ICCs from gap junctions with each other and smooth muscle cells electrically coupling them
>slow waves in ICCs drive slow waves in the smooth muscle cells couple to them
>some ICCs form a bridge between nerve endings and smooth muscle cells
»depolarising slow waves do not necessarily result in smooth muscle contraction
»contraction in the intestine occurs only if the slow wave amplitude is sufficient to reach a threshold to trigger smooth muscle cell calcium action potentials (spikes)
»force is related to number of action potentials discharged ie driven in turn by the duration of the slow wave that is above threshold

22
Q

what are slow waves aka ?

A

basic electrical rhythm
>BER
»varies in frequency along the length of the GI tract ie stomach is 3 mins while small intestine is 8-12mins

23
Q

whether or not the slow wave amplitude reaches threshold depends on:

A

neuronal stimuli, hormonal stimuli, mechanical stimuli

> these generally act to depolarise smooth muscle cells rather than influence slow waves directly - depolarisation shifts slow wave peak to threshold

24
Q

what does the parasympathetic autonomic innervation of the GI tract consist of ? and how do they work

A

> Preganglionic fibres (releasing ACh) synapse with ganglion cells (in essence post-ganglionic neurones) within the enteric nervous system (ENS)
Excitatory influences
increased gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction
Inhibitory influences
relaxation of some sphincters, receptive relaxation of stomach

25
Q

what consists of the sympathetic autonomic innervation of the GI tract ? and how do they work

A

*functionally less important than the parasympathetic NS

> Preganglionic fibres (releasing ACh) synapse in the prevertebral ganglia. Postganglionic fibres (releasing NA) innervate mainly enteric neurones, but also other structures
Excitatory influences
Increased sphincter tone
Inhibitory influences
Decreased motility, secretion and blood flow

26
Q

what is the ENS

A

is is about 100 million neurones, cells mostly located in ganglia connected by fibre tracts within
- the myenteric plexus
-submucous plexus
>is intrinsic to GI tissue
-reflex circuits can operate independently but hormones and extrinsic nerves exert a strong regulatory influence
>co-ordinates muscular, secretive and absorptive activities via:
sensory neurones, interneurones, effector neurones

27
Q

myenteric plexus

A

“Auerbach’s”

>mainly regulates motility and sphincters

28
Q

submucous plexus

A

“Meissner’s”

>mainly modulates epithelial and blood vessels

29
Q

sensory neurones

A

mechanoreceptors, chemoreceptors, thermoreceptors

30
Q

interneurones

A

the majority, co-ordinating reflexes and motor programmes

31
Q

effector neurones

A

> excitatory and inhibitory motor neurones

>they supply:
both smooth muscle layers, 
secretory epithelium,
endocrine cells and
blood vessels
32
Q

what do nerve reflexes do ? and give examples

A

control motor and secretory activity

> a local reflex = peristalsis
short reflex = intestino-intestinal inhibitory reflex
long reflex = gastroileal reflex (a vaso-vagal reflex)

33
Q

the major motility patterns

A

peristalsis and

segmentation

34
Q

peristalsis

A

> Peristalsis – a wave of relaxation, followed by contraction, that normally proceeds a short distance along the gut in an aboral direction – triggered by distension of the gut wall

  • *aboral - altered activity of interneurones > altered activity of motor neurones > circular muscle relaxes (release of VIP and NO from inhibitory motor neurone) OR > longitudinal muscle contract (release of ACh and substance P from excitatory motorneurone)
  • *oral - altered activity of interneurones >altered activity of motor neurones >circular muscle contracts (release of ACh and substance P from excitatory motor neurone) OR longitudinal muscle relaxes (release of VIP and NO from inhibitory motor neurone)
35
Q

segmentation

A

> Segmentation (mixing, or churning, movements) – rhythmic contractions of the circular muscle layer that mix and divide luminal contents
occurs in the small intestine (in the fed state) and in the large intestine (where it is called haustration) (greater detail in small intestine lecture)
colonic mass movement = powerful sweeping contraction from stomach to terminal ileum
tonic contractions (sustained contractions) = low pressure ie stomach
= high pressure ie sphincter

36
Q

functions of the sphincters of the tract

A

*there are 6
>act as one way valves by maintaining a positive resting pressure relative to two adjacent structures
>stimuli (pressure) proximal and distal to a spitter cause opening and closing respectively

37
Q

upper oesophagus sphincter UOS

A

skeletal muscle relaxes to allow swallowing and closes during inspiration

38
Q

lower oesophageal sphincter LOS

A

relaxes to permit entry of food to the stomach and closes to prevent reflux of gastric contents to the oesophagus

39
Q

pyloric sphincter

A

regulates gastric emptying and usually prevents duodenal gastric reflux

40
Q

ileocaecal sphincter

A

regulates flow from ileum to caecum, distension of ileum opens and distension of proximal colon closes

41
Q

internal and external anal sphincters

A

are regulated by defaecation reflex

GI (39 decks)

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