Grand Tour of Alimentary Canal Flashcards
What are the 4 functions of the digestive system?
- Digestion
- Secretion
- Absorption
- Motility
What happens in the mouth?
Foodstuffs broken down by chewing. Saliva added as lubricant
What happens in the oesophagus?
Acts as a conduit between the mouth and the stomach
What happens in the stomach?
- Digestion of proteins
- Foodstuffs reduced to liquid form
- Storage
- Sterilisation
What happens in the pancreas?
Digestive enzymes for digestion of fats, carbohydrates and proteins
What happens in the liver?
Bile salts for digestion/absorption of fats in small intestine
What happens in the gallbladder?
Stores and concentrates bile
What happens in the small intestine?
Final stages of chemical digestion and nutrient absorption
What happens in the large intestine?
Water absorption, bacterial fermentation and formation of faeces
What is the general structure of the alimentary canal?
- Continuous hollow tube of varying diameter
- Spans from oesophagus to the rectum
- 8m long
- Tube wall has same structural organisation throughout length
What are the 4 distinctive layers of the alimentary canal?
- Mucosa
- Submucosa
- Muscularis extena
- Serosa/adventitia
What are the 3 components of the mucosa?
- Epithelium
- Lamina propria
- Muscularis mucosae
What type of epithelium is found in the mouth, oesophagus and anal canal?
Stratified squamous
What type of epithelium is found in the stomach, small and large intestine?
Simple columnar
Why does the epithelium differ along the length of the gut tube?
Adaption for function
What is the function of the epithelium?
- Acts as a barrier separating lumen of the alimentary canal from the body
- Synthesis and secretion of digestive enzymes, hormones and mucus
- Absorbs products of digestion
What is the lamina propria?
Loose connect tissue
What is the muscularis mucosae?
Thin smooth muscle layer
What is the submucosa?
Thick, irregular connective tissue that supports mucosa
What does the submucosa contain?
Neurones, blood vessels and lymphatic
What do the blood vessels contained within the submucosa supply?
- Mucosa
- Muscularis externa
- Serosa
What do the neurones contained within the submucosa form?
An extensive network known as the submucosal plexus
Where can submucosal glands be found?
- Oesophagus
- Duodenum
What is the serosa/adventitia?
Connective tissue outer layer of the alimentary canal
What is the outer layer of the alimentary canal outside of the peritoneal cavity?
Adventitia that attaches the oesophagus and rectum to surrounding structures
What is the outer layer of the alimentary canal inside the peritoneal cavity?
Serosa surrounds the stomach, small intestine and large intestine
What is the muscularis externa composed of?
-Two concentric thick layers of smooth muscle
What are the 2 layers of the muscularis externa?
- Inner layer= circular muscle which constricts the lumen
- Outer layer= longitudinal muscle which shortens the tube
What is the function of the muscularis externa?
-Produce motility through peristalsis and segmentation
What neural plexus is located between the circular and longitudinal muscle?
Myenteric (Auerbach’s) plexus
What is the enter nervous system composed of?
- Submucosal plexus
- Myenteric plexus
What does the enteric nervous system allow?
Independent control of gut function
What is the autonomic control of the alimentary system?
- Long (parasympathetic)
- Short (ENS)
What nerve is responsible for parasympathetic control of the alimentary system?
Vagus nerve
How does the parasympathetic system act on the alimentary system?
Stimulatory
- Increase secretion
- Increases motility
How does the sympathetic system act on the alimentary system?
Inhibitory
- Decreases secretion
- Decreases motility
What nerve is responsible for sympathetic control of the alimentary system?
Splanchnic nerve
What nerves are responsible for salivation?
Facial and glossopharyngeal
What does the celiac trunk supply?
- Stomach
- Small intestine
- Pancreas
- Liver
What does the superior mesenteric artery supply?
- Small intestine
- Caecum
- Ascending colon
- Transverse colon
What does the inferior mesenteric artery supply?
- Descending colon
- Sigmoid colon
- Rectum
What drains the stomach?
Gastric veins
What drains the pancreas?
Splenic vein
What does the superior mesenteric vein drain?
- Small intestine
- Caecum
- Ascending colon
- Transverse colon
What does the inferior mesenteric vein drain?
- Descending colon
- Sigmoid colon
- Rectum
What drains into the hepatic portal vein?
- Gastric veins
- Splenic vein
- Superior mesenteric vein
- Inferior mesenteric vein
What does the hepatic portal vein drain into?
Hepatic vein
What drains into the inferior vena cava?
Hepatic vein
