Grand tour of the alimentary canal Flashcards
What are the functions of the digestive system?
Digestion
Secretion
Absorption
Motility
What is the function of the mouth in the digestive system?
Foodstuffs broken down by chewing
Saliva added as lubricant
Amylase present to start digestion of starch
What is the function of the oesophagus in the digestive system?
Conduit between mouth and stomach
What is the function of the stomach in the digestive system?
Digestion of proteins
Foodstuffs reduced to liquid form
Storage
Sterilisation
What is the purpose of foodstuffs being stored in the stomach?
Stored in the stomach for slow release
Essential or you would have to constantly eat small amounts
How are foodstuffs sterilised in the stomach?
Hydrochloric acid present
What is the function in the pancreas in the digestive system?
Releases enzymes for digestion of fats, proteins and carbohydrates
What is the function o the liver in the digestive system?
Production of bile salts for digestion and absorption of fats in the small intestine
What is the function of the gallbladder in the digestive system?
Stores and concentrates up to 50ml of bile
What is the function of the small intestine in the digestive system?
Nutrient absorption
Final stages of digestion
What is the function of the large intestine in the digestive system?
Primarily water absorption
Bacterial fermentation
Formation of faeces
What is the general structure of the alimentary canal?
Continuous hollow tube of varying diameter
Roughly how long is the alimentary canal?
8m
What are the 4 layers of the alimentary canal wall?
Mucosa
Submucosa
Muscularis externa
Serosa/adventitia
What are the layers of the mucosa?
Mucous epithelium
Lamina propria
Muscularis mucosae
What is the structure of the mucous epithelium in the mouth, oesophagus and anal canal?
Stratified squamous
What is the structure of the mucous epithelium in the stomach and small and large intestines?
Simple columnar
Why is there a difference in structure of the mucous epithelium in the alimentary canal?
In the mouth, oesophagus and anal canal, there is lots of abrasion and several layers of cells are needed to present ulcer formation and holes being created
What is the function of the mucous epithelium?
Separates the lumen of the alimentary canal from the body
Synthesis and secretion of digestive enzymes, hormones and mucus
What is the lamina propria?
Loose connective tissue
What is contained in the lamina propria?
Glands
Blood vessels
Lymph vessels
What is the muscular mucosae?
Thin smooth muscle layer
What is the submucosa?
Thick irregular connective tissue that supports the mucosa
What is contained in the submucosa?
Neurones
Blood vessels
Lympathic vessels
Glands (in oesophagus and duodenum)
In what regions are hands present in the submucosa?
Oesophagus and duodenum
What do the neutrons in the submucosa form?
Submucosal plexus
What is the function of the submucosal plexus?
Gut control along with myenteric plexus
What is the muscular externa?
2 concentric layers of smooth muscle
What are the 2 layers of the muscular externa?
Inner layer of circular muscle
Outer layer of longtidinal muscle
What are the functions of the 2 layers of the muscular externa?
Circular muscle- constricts lumen for peristalsis
Longitudinal muscle- Shortens tube for segmentation
What is present between the circular and longitudinal muscle?
Myenteric plexus
What allows for independent control of gut function?
Submucosal and myenteric plexuses- enteric nervous system
What is the serosa/adventitia?
Connective tissue sheath that is the outermost layer of the alimentary canal
What is the function of the serosa outside the peritoneal cavity?
Attaches oesophagus and rectum to surrounding structures
What is the function of the serosa inside the peritoneal cavity?
Surrounds stomach, small intestine and large intestine
What are the 2 nervous networks in the alimentary canal?
Submucosal plexus
Myenteric plexus
What nerve in the main parasympathetic control of th alimentary canal?
Vagus
What nerves control salivation?
Facial and glossopharyngeal nerves
What does activation of the parasympathetic system do to the alimentary canal?
Increase secretion and motility
What is the main sympathetic nerve in control of the alimentary canal?
Splanchnic nerve
What does activation of the sympathetic system so to the alimentary canal?
Decreases secretion and motility
Doesn’t have this effect on salivation
What Are the 3 main supplies to the alimentary system?
Celiac trunk
Superior mesenteric
Inferior mesenteric
What does the celiac trunk supply?
Stomach
Small intestine
Pancreas
Liver
What does the superior mesenteric supply?
Small intestine
Caecum
Ascending colon
Transverse colon
What does the inferior mesenteric supply?
Descending colon
Sigmoid colon
Rectum
What is the venous drainage of the stomach?
Gastric vein
What is the venous drainage of the pancreas?
Splenic veins
Whatis the venous drainage of the small intestine, caecum, ascending colon and transverse colon?
Superior mesenteric
What is the venous drainage of the descending colon, sigmoid colon and rectum?
Inferior mesenteric
What do the gastric veins drain?
Stomach
What do the splenic veins drain?
Pancreas
What do the superior mesenteric veins drain?
Small intestine
Caecum
Ascending colon
Transverse colon
What do the inferior mesenteric veins drain?
Descending colon
Sigmoid colon
Rectum
Where do the veins eventually drain?
Hepatic portal vein
Portal vein
IVC
Where does the hepatic portal vein drain to?
Liver
Where does the hepatic vein pick up from and drain to?
Liver to IVC
