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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
In the stomach, small intestine and large intestine spontaneous electrical activity occurs as slow waves, what are they?
Rhythmic patterns of membrane depolarization and repolarization that spread from cell to cell via gap junctions
26
Interstitial cells of Cajal (ICCs)
Pacemaker cells located largely between the circular and longitudinal muscle layers Drive slow wave electrical activity
27
Slow wave Electrical activity
determines the frequency, directions
28
Contraction in the intestines
occurs only id the slow wave amplitude is sufficient to reach a threshold to trigger smooth muscle cell calcium action potentials
29
Factors determining whether slow wave amplitude reaches threshold
Neuronal stimuli Hormonal stimuli Mechanical stimuli
30
Autonomic Innervation of GI tract- parasympathetic
Preganglionic fibres (releasing ACh) synapse with ganglion cells within enteric nervous system
31
Excitatory influences on parasympathetic innervation
increased gastric, pancreatic and small intestinal secretion, blood flow and smooth muscle contraction
32
Inhibitory influences on parasympathetic innervation
relaxation of some sphincters, receptive relaxation of stomach
33
Autonomic innervation of GI tract- sympathetic
preganglionic fibres (releasing ACh) synapse in the prevertebral ganglia, postganglionic fibres (releasing NA) innervate mainly enteric neurones
34
excitatory influences of sympathetic innervation
Increased sphincter tone
35
Inhibitory influences of sympathetic innervation
decreased motility, secretion and blood flow
36
Myenteric plexus
mainly regulates motility sphincters
37
Submucous plexus
mainly modulates epithelia and blood vessels
38
ENS
Cell bodies located in ganglia connected by fibre tracts withing myenteric or submucous plexus Intrinsic to GI tissue
39
how does ENS moderate activity
Sensory neurones (mechanoreceptors, chemoreceptors, thermoreceptors) Interneurones (majority, co-ordinating reflexes and motor programs) Effector neurones
40
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
41
segmentation
rhythmic contractions of the circular muscle layer that mix and divid luminal contents
42
Colonic mass movement
powerful sweeping contraction that forces faeces into the rectum- occurs a few times a day
43
Migrating motor complex
Power sweeping contraction from stomach to terminal ileeum
44
6 Sphincters
``` Upper oesophageal sphincter Lower oesophageal sphincter Pyloric sphincter Ileocaecal Valve Internal and external anal sphincters ```
45
Uppoer oesophageal sphincter
skeletal muscle | relaxes to allow swallowing, closes during inspiration
46
Lower oesophageal sphincter
relaxes to permit entry of food to stomach, closes to prevent reflux of gastric contents to oesophagus
47
Pyloric sphincter
regulates gastric emptying, usually prevents duodenal gastric reflux
48
Ileocaecal valve
regulates flow from ileum to caecum, distentions of ileum opens, distension of proximal colon closes
49
Internal and external anal sphincters
Internal- smooth muscle External- skeletal regulated by defaecation reflex
50
parotid gland
produces least saliva- innervated by glossopharyngeal nerve (CNIX)
51
Submandibular gland
produces the most saliva | innervated by facial nerve (CNVII)
52
Sublingual gland
produces most viscous saliva | innervated by facial nerve (CNVII)
53
structure of salivary glands
external capsule > septae separating lobes and lobules > lobules composed of salivons
54
3 phases of gastric secretion
Cephalic- before food reaches stomach Gastric- food in the stomach Intestinal- after food left the stomach

GI (25 decks)

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