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GI > structure of alimentary canal > Flashcards

structure of alimentary canal Flashcards

1
Q

mouth and pharynx

A

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

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2
Q

Oesophagus

A

propels food to stomach

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3
Q

Stomach

A

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

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4
Q

Small intestine

A

Duodenum, Jejunum, and ileum

Principle site of digestion and absorption of nutrients

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5
Q

Large intestine

A

Caecum, Appendix and Colon

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

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6
Q

Rectum anal canal and anus

A

regulated expulsion of faeces

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7
Q

Accessory structures

A

Salivary glands, pancrease, liver and gall bladder

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8
Q

structure of digestive tract wall

A

mucosa, submucosa, muscularis externa, serosa

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9
Q

Mucosa

A 
mucous membrane (epithelial exocrine gland and endocrine gland cells)
Lamina propia (capillaries enteric neurones, gut associated lymphoid tissue)
Muscularis mucosae
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10
Q

Submucosa

A

connective tissue
larger blood and lymph vessels
glands
submucous plexus

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11
Q

Muscularis externa

A

circular muscle layer
myenteric plexus
longitudinal muscle layer

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12
Q

serosa

A

connective tissue

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13
Q

4 major functions of alimentary canal

A

Motility, secretion, digestion, absorption

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14
Q

Motility

A

mechanical activity mostly involving smooth muscle (skeletal at mouth, pharynx, upper oesophagus and external anal sphincter)

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15
Q

secretion

A

required for digestion, protection and lubrication

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16
Q

Digestion

A

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

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17
Q

Absorption

A

Transfer of the absorbable products of digestions from the digestive tract to the blood or lymph

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18
Q

Motility

Circular muscle contraction

A

Lumen becomes narrower and longer

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19
Q

Motility

Longitudinal muscle contraction

A

intestine become shorter and fatter

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20
Q

Motility

Muscularis mucosae contraction

A

change in absorptive and secretory area of mucosa (folding), mixing activity

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21
Q

Smooth muscle cells in GI tract are?

A

Coupled by gap junctions which allow electrical current flow from cell to cell

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22
Q

Synchronous wave

A

Hundreds of cells are depolarized and contract at the same time

23
Q

Pacemaker cells

A

Drive spontaneous activity across the coupled cells

24
Q

Pacemaker cells are modulated by…

A

Intrinsic (enteric) and extrinsic (autonomic) nerves

Numerous hormones

25
Q

In the stomach, small intestine and large intestine spontaneous electrical activity occurs as slow waves, what are they?

A

Rhythmic patterns of membrane depolarization and repolarization that spread from cell to cell via gap junctions

26
Q

Interstitial cells of Cajal (ICCs)

A

Pacemaker cells located largely between the circular and longitudinal muscle layers
Drive slow wave electrical activity

27
Q

Slow wave Electrical activity

A

determines the frequency, directions

28
Q

Contraction in the intestines

A

occurs only id the slow wave amplitude is sufficient to reach a threshold to trigger smooth muscle cell calcium action potentials

29
Q

Factors determining whether slow wave amplitude reaches threshold

A

Neuronal stimuli
Hormonal stimuli
Mechanical stimuli

30
Q

Autonomic Innervation of GI tract- parasympathetic

A

Preganglionic fibres (releasing ACh) synapse with ganglion cells within enteric nervous system

31
Q

Excitatory influences on parasympathetic innervation

A

increased gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction

32
Q

Inhibitory influences on parasympathetic innervation

A

relaxation of some sphincters, receptive relaxation of stomach

33
Q

Autonomic innervation of GI tract- sympathetic

A

preganglionic fibres (releasing ACh) synapse in the prevertebral ganglia, postganglionic fibres (releasing NA) innervate mainly enteric neurones

34
Q

excitatory influences of sympathetic innervation

A

Increased sphincter tone

35
Q

Inhibitory influences of sympathetic innervation

A

decreased motility, secretion and blood flow

36
Q

Myenteric plexus

A

mainly regulates motility sphincters

37
Q

Submucous plexus

A

mainly modulates epithelia and blood vessels

38
Q

ENS

A

Cell bodies located in ganglia connected by fibre tracts withing myenteric or submucous plexus
Intrinsic to GI tissue

39
Q

how does ENS moderate activity

A

Sensory neurones (mechanoreceptors, chemoreceptors, thermoreceptors)
Interneurones (majority, co-ordinating reflexes and motor programs)
Effector neurones

40
Q

peristalsis

A

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

41
Q

segmentation

A

rhythmic contractions of the circular muscle layer that mix and divid luminal contents

42
Q

Colonic mass movement

A

powerful sweeping contraction that forces faeces into the rectum- occurs a few times a day

43
Q

Migrating motor complex

A

Power sweeping contraction from stomach to terminal ileeum

44
Q

6 Sphincters

A 
Upper oesophageal sphincter
Lower oesophageal sphincter
Pyloric sphincter
Ileocaecal Valve
Internal and external anal sphincters
45
Q

Uppoer oesophageal sphincter

A

skeletal muscle

relaxes to allow swallowing, closes during inspiration

46
Q

Lower oesophageal sphincter

A

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

47
Q

Pyloric sphincter

A

regulates gastric emptying, usually prevents duodenal gastric reflux

48
Q

Ileocaecal valve

A

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

49
Q

Internal and external anal sphincters

A

Internal- smooth muscle
External- skeletal
regulated by defaecation reflex

50
Q

parotid gland

A

produces least saliva- innervated by glossopharyngeal nerve (CNIX)

51
Q

Submandibular gland

A

produces the most saliva

innervated by facial nerve (CNVII)

52
Q

Sublingual gland

A

produces most viscous saliva

innervated by facial nerve (CNVII)

53
Q

structure of salivary glands

A

external capsule > septae separating lobes and lobules > lobules composed of salivons

54
Q

3 phases of gastric secretion

A

Cephalic- before food reaches stomach
Gastric- food in the stomach
Intestinal- after food left the stomach

GI (25 decks)

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