Anatomy, Histology and Control of GI tract Flashcards
what are the functions of the GI tract?
Secretion, digestion, absorption, motility, elimination, protection
What is the GI tract?
continuous muscular digestive tube extends through thorax and abdomen
What does GI tract do?
digest food mechanically and chemically into small molecules and absorbs the digested molecules through its lining into the blood
What are the organs of the alimentary canal?
Mouth, pharynx, oesophagus, stomach, intestines - seperated by sphincters
Where does large intestine terminate?
in anal canal
What are accessory digestive organs?
Teeth, tongue, gallbladder, large digestive glands - salivary, liver and pancrease
Where are the digestive glands and gallbladder?
in abdomen outside GI tract, connects via ducts
What do accessory digestive glands produce?
variety of enzyme/fluid secretions contribute to breakdown of food stuff
What is the basic structure of GI tract?
Serosa - muscularis externa - myenteric plexus - muscularis interna - submucosa plexus - submucosa
What is shape of muscle in muscularis externa?
circular and longitudinal SM muscle
Why does glandular mucosa stain dark?
Epithelial and CT nuclei it contracts
Describe muscularis mucosa?
thin strip marks
What does submucosa mainly contain?
Dense college fibres
What does serosa have an edge of?
Mesothelium from near mesenteric attachment, adipose tissue and large blood vessels
What local stimuli changes function of GI tract?
Stretch distension of tract wall
Concentration of solutes - osmolarity
acidity/alkaline PH
Concentration of nutrients - fats, peptides
What does local stimuli act on?
Sensory receptors in mucosal layer of tract to initiate reflexes which act through muscles or glands
What does signals from CNS change of GI function?
Anticipation of food, fear - not under voluntary control, performed by smooth muscles and glands
What are 2 types of control on GI?
Nervous
Hormonal
What is nervous control on GI?
Extrinsic - outside GI tract , via autonomic nerves from CNS - long reflexes
Intrinsic - solely within GI - via enteric nerves within plexuses - short reflexes
What does parasympathetic nerves do on GI control?
Via vagus nerves, stimulate blood flow, motility, secretion, relaxes sphincters
What does sympathetic nerves do on GI control?
inhibits blood flow, motility, secretion
contracts sphincters
What does object in lumen do?
Activate sensory receptors of mucosa - send impulses to submucous plexes for secretions of fluid and mucus
Myenteric plexus - contract of muscles to push object
Where are GI hormones secreted into?
Bloodstream
Where are GI hormones produced?
By specialised cells called enterochromaffin cells spread through mucosal layer
What do hormones produced do?
Regulate functions of tract itself or accessory organs - communicate with CNS
What are the hormones?
peptides 20-40 AA in length
How many peptide hormones in GI?
50 peptide hormones
What does secretin do?
Secrete alkaline fluid from pancreas to duodenum
