Grand tour of the alimentary canal Flashcards
what are the functions of the alimentary canal?
- Digestion
- absorption
- Motility
- Secretion
Where does digestion take place
Stomach to SI
Where does motility take place
Throughout the gut tube
where do secretion and absorption take place?
In the SI and LI
Brief description of what occurs in different parts of the GI
-Mouth: mechanical digestion release of saliva- adds moisture -Oesophagus Connector -Stomach chemical digestion begins protein breakdown temporary storage Food into liquid form -Pancreas enzymatic breakdown of carbs, fat and protein -Liver releases bile for the breakdown of fats -Gallbladder stores and concentrates bile -SI chemical digestion- mainly in first 2/3rds -LI water absorption and formation of faeces
Structure Layers
Mucosa: -epithelium -lamina propria -muscularis mucosae Submucosa Muscular externa: -concentric -longitudinal Serosa/adventia
Stratified squamous in mucosa:
where is it found
Mouth
Oesophagus
Anal canal
Simple columnar in mucosa:
where is it found
Stomach
SI
LI
What are the main functions of the mucosa
- separates the lumen of the digestive system
- Secretes digestive enzymes
- absorbs products of digestion
what is the lamina propria made of?
Lose connective tissue containing glands, blood and lymph
what is the muscularis mucosae made of?
smooth muscle
what is submucosa made of
irregular/dense connective tissue containing neurones, blood vessels and lymph
function of inner circular muscularis external
constricts the lumen - peristalsis
function of outer longitudinal muscularis externa
shortens tube- segmentation
what type of muscle is the muscularis externa
concentric and smooth
Function of the serosa/adventia
Outside of peritoneal cavity: the adventia attaches oesophagus and rectum to surrounding organs
Inside the peritoneal cavity: the serosa surrounds the stomach, the SI and the LI
What is found between the submucosa and the muscularis externa
the submucosal plexus
what is found between the two layers of concentric muscle?
the myenteric plexus
different nervous systems?
autonomic- control gut motility -Long reflexes- gut to CNS -short reflexes- within the gut parasympathetic -vagus nerve- enhancesl secretion and motility- NOT SALIVATION sympathetic -inhibits secretion and motility
what controls salivation?
the glassopharangeal and facial nerves
Arterial supply
abdominal aorta :
celiac trunk
superior mesenteric artery
inferior mesenteric artery
venous drainage of stomach
gastric veins
venous drainage of the pancreas
splenic veins
venous drainage of SI to transverse colon
superior mesenteric vein
venous drainage from descending colon to rectum
inferior mesenteric vein
where to the gastric, splenic, SMV and IMV drain?
the hepatic portal vein- into the hepatic vein-into the IVC
why are the liver and gut in series?
so gut blood can be filtered before entering systemic circulation
What makes up the autonomic enteric nervous system
- Meissners plexus
- Myenteric plexus
