Intro to struct./funct. of Alimentary Canal Flashcards
Alimentary Canal
series of hollow organs running from mouth to anus that are separated by sphincters, controlling movement
Aboral
towards anus
Function of Mouth
chop food, lubricate (saliva), begin carbohydrate digestion
Function of Oropharynx
propels food to oesophagus
Function of Oesophagus
propels food to stomach
Function of Stomach
stores and churns food, continues carbohydrate digestion, begins protein digestion, regulates the deliver of chyme to duodeum
Chyme
partially digested food, water, hydrochloric acid, various digestive enzymes
from bolus
Function of Small intestine
digestion and absorption of nutrients (PRINCIPLE SITE)
Function of Large Intestine
colon reabsorbs fluids/electrolytes, stores faecal matter before delivering it to the rectum
Function of the Rectum and Anus
storage and regulated expulsion of faeces
Accessory structures
Salivary glands
Pancreas
Liver and gall bladder
Motility
mechanical movements of the GI tract
4 layers of the digestive tract wall
mucosa
submucosa
muscular externa
serosa
Serosa
Releases a sticky fluid that allows sliding movement
Submucosa Plexus
Absorption + Secretin
Muscularis Externa
Circular Muscle layer
Nerve network
Longitudinal Muscle
Circular Muscular Contraction
Narrow / Long
Longitudinal Muscle Contraction
Shorter / Fatter
Muscular Mucosae Contraction
change in absorptive / secretory area of mucosa (folding) / mixing activity
Taeniea Coli
longitudinal muscle layer presents as 3 longitudinal bands
Junctions between smooth muscle
Gap junctions
Single unit smooth muscle
hundreds of cells are depolarised and contract @ the same time as a synchronous wave
Electrical activity occurs as …
slow waves
Contraction is caused by
action potentials
ICCs (interstitial cells of canal)
pacemakers cells between numerous SMCs
Slow waves reach action potentials due to
underlying depolarisation
Upstroke
Ca2+ channels
Downstroke
K+ channels
Myenteric Plexus
regulates motility and sphincters
Submucous Plexus
modules epithelia & blood vessels
Key transmitters
5-HT, ACh, NO, SiP, VIP
3 neurones
Sensory neurones
Interneurones
Effector neurones
Effector neurones
supply
- smooth muscle
- secretary epithelium
- endocrine cells
- blood vessels
Intrinsic Reflex
Local reflex
Local reflex example
local reflex
Extrinsic reflex
short reflex
long reflex
Short reflex
Intestino-intestinal inhibitory reflex
Long reflex
Gastroileal reflex
Local reflex
peristalsis
Peristalsis
an orderly wave of relaxation, followed by contraction, that normally proceeds along the hut in an aboral direction - triggered distention of the gut
VIP & NO
relax
Each + SiP
exiting