Tour of The Alimentary Canal Flashcards
What are the four functions of the digestive system?
Digestion
Secretion
Absorption
Motility
What are the three salivary glands called?
Sublingual (superior), Submandibular (inferior), Parotid (posterior)
Where foodstuffs are broken down by chewing; saliva added as lubricant
Mouth
Conduit between mouth + stomach
Oesophagus
The conduit between the mouth and stomach
Oesophagus
Location where proteins are digested; foodstuffs reduced to liquid form; storage and sterilisation occurs
Stomach
Produces and secretes digestive enzymes for fat, carbohydrates and proteins
Pancreas
Forms bile salts and amphipathic molecules which emulsifies and absorbs fat in the small intestine
Liver
Stores and concentrates bile
Gallbladder
Where the final stages of chemical digestion and nutrient absorption occurs
Small intestine
Site of water absorption, bacterial fermentation and faecal formation
Large intestine
What are the four functions of the stomach?
Protein digestion
Liquifying foodstuffs
Storage
Sterilisation
For every 8-9L which enters the body how much of it leaves it?
200ml
What is the approximate length of the GI tract (Oesophagus to rectum)?
Approx 8m
What are the four distinct layers (tunics) of the GI tract called?
Mucosa
Submucosa
Muscularis Externa
Adventitia/Serosa
What are the three layers of the mucosa?
Epithelium
Lamina Propria
Muscularis Mucosae
When is it adventitia and when is it Serosa?
Adventitia is located outside the peritoneal cavity whereas the Serosa is located within
(Adventitia is the upper/proximal 2/3rds of the Oesophagus whilst lower/distal 1/3rd is Serosa)
Where are the two intramural plexuses?
Myenteric Plexus/Auerbach’s (between circular and longitudinal muscles in Muscularis externa)
Submucosal Plexus/Meissner’s plexus (between Muscularis externa + submucosa)
What is the epithelial lining in the Mouth, Oesophagus, anal canal
Stratified Squamous NON-KERATINISED epithelium
What is the epithelial lining of the stomach, small and large intestine
Simple columnar epithelium
What are the three functions of the mucosa
- A barrier dividing the intestinal lumen from the body
- Synthesis and secretion of digestive enzymes, hormones + mucus
- Absorbs products of digestion
What are the two layers of the Muscularis externa?
Circular muscle (constricts the lumen)
Longitudinal muscle (shortens tube)
What forms the enteric nervous system (ENS)?
Submucosal + myenteric plexuses
What are the two ways autonomic control affects the alimentary canal?
Long Parasympathetic (afferent to CNS)
Short ENS reflexes (both afferent + efferent, reflex in Submucosal + myenteric plexus)
What is the main nerve controlling the parasympathetic response of the alimentary system
Vagus nerve (X)
What two nerves control salivation?
Facial (VII) and glossopharyngeal (IX) (both are sympathetic)
What action does the vagus have on the alimentary system?
Stimulatory:
1) increases secretion
2) increases motility
How is the alimentary system sympathetically innervated?
Via the splanchnic nerve
What action does the sympathetic nervous system have on the alimentary system?
Inhibition:
1) inhibits secretion
2) inhibits motility
What branch of the abdominal aorta supplies the stomach, pancreas, liver and proximal small intestine?
Coeliac trunk
What organs does the coeliac trunk supply?
stomach
pancreas
liver
proximal small intestine
What branch of the abdominal aorta does supplies the caecum, ascending colon, transverse colon and distal small intestine?
Superior mesenteric artery
What organs does the superior mesenteric artery supply?
Caecum, ascending colon, transverse colon, distal small intestine
What branch of the abdominal aorta supplies the descending colon, sigmoid colon and rectum?
Inferior mesenteric artery
What organs does the inferior mesenteric artery supply?
descending colon
sigmoid colon
rectum
What veins drain the stomach?
Gastric vein
What vein drains the pancreas?
Splenic vein
What vein drains the caecum, small intestine, ascending colon, transverse colon
Superior mesenteric vein
Vein which drains the descending colon, sigmoid colon and rectum
Inferior mesenteric vein
Vein which drains the gastric veins, splenic vein, superior and inferior mesenteric veins
Hepatic portal vein
Hepatic portal vein ==> ______ ====> ______
Hepatic portal vein ===> Hepatic vein ====> inferior vena cava
What is the nutrient content and oxygenation of the blood in the hepatic portal vein, hepatic vein and inferior vena cava?
hepatic portal vein: low O2, high nutrient
Hepatic vein: High O2, low nutrient
Inferior vena cava: High O2, High nutrient
