Flashcards in Physiology Deck (45):
What is the function of the mouth and saliva?
Foodstuffs broken down by chewing (mastication) and saliva is added as lubricant
What is the function of the oesophagus?
Conduit between the mouth and the stomach
What is the function of the pancreas?
Digestion enzymes for digestion of lipids.
Helps with the absorption of fats, carbohydrates and proteins
What is the function of the liver?
Secretes bile salts to aid the absorption of fats in the ileum
What is the function of the gallbladder?
Stores and concentrates bile
What is the function of the small intestine?
Final stage of chemical digestion and nutrient absorption
What is the function of the stomach?
Digestion of proteins; foodstuffs reduced to liquid.
Also plays a role in storage and sterilisation
What is the function of the large intestine?
Water absorption, bacterial fermentation and formation of faeces
Describe the length, diameter and organisation of the GI tract
Approx. 8m long, varying diameter and organisation of cells vary depending on function
Describe the difference in the microscopic composition of the GI tract
Mouth, anal canal and oesophagus - Stratified Squamous epithelium
Stomach and intestines - simple columnar epithelium
What are the four layers common to the GI tract?
- Muscularis externa
What structures comprise the mucosa?
Epithelium, lamina propria, muscularis mucosa
What is the function of the mucosa?
- Synthesis and secretion of enzymes
- Absorbs products of digestion
What is the lamina propria?
Loose connective tissue containing glands and blood/lymph vessels
What is the muscularis externa?
A thin layer of muscle
What is the structure of the submucosa?
Thick, irregular connective tissue
What is the function of the submucosa?
Supports the mucosa
What structures permeate the submucosa?
Neurones, blood vessels (to the mucosa, adventitia and muscularis externa)
What is the network of neurones in the mucosa known as?
Meissner's plexus (parasympathetic)
Where are submucosal glands located?
Oesophagus and duodenum
What is the structure of the muscularis externa?
Two layered ring of muscle
What are the function s of the two layers of muscle in the muscularis externa?
Inner - circular - contraction of lumen
Outer - longitudinal - constriction of tube length
Allows peristalsis and segmentation
What is peristalsis?
Rhythmic longitudinal contractions of the lumen of the GI tract to promote transit of bolus
What is segmentation?
Contraction of the circular (inner) muscles of the gut tube - slowing down the transit of chyme through the system.
What neural system lies between the layers of the muscularis externa?
Auerbach's Myenteric Plexus
What is the enteric nervous system comprised of?
Submucosal (Meissner's) and Myenteric (Auerbach's) plexi
What is the function of the enteric nervous system?
Independent control of the GI tract
What is the difference between the adventitia and the serosa?
Both are outer layers of connective tissue for the alimentary canal
Location is the difference:
Serosa = inside the peritoneal cavity
Adventitia = outside the peritoneal cavity
What division of the autonomic nervous system governs long reflexes in the alimentary canal?
What division of the autonomic nervous system governs short reflexes in the alimentary canal?
What nerve delivers parasympathetic innervation?
Vagus nerve (CN X) except for salivation (Facial CN VII and glossopharyngeal IX)
What is the effect of the parasympathetic system in the GI tract?
Increases gut motility and secretion
What is the effect of the sympathetic system on the GI tract?
Decreases gut motility and secretion
What nerve delivers sympathetic innervation to the GI tract?
What three branches of the descending aorta supply the GI tract?
Celiac trunk, superior and inferior mesenteric arteries
What organs does the coeliac trunk supply?
Stomach, small intestine, pancreas and liver
What organs does the superior mesenteric artery supply?
Small intestine, caecum, ascending colon and transverse colon
What organs do the inferior mesenteric artery supply?
Descending colon, sigmoid colon and rectum
What vein(s) drain from the stomach?
What vein(s) drain from the pancreas?
What organs rain into the superior mesenteric vein?
Small intestine, caecum, ascending and transverse colon
What organs drain into the inferior mesenteric vein?
Descending colon, sigmoid colon and rectum
Where do the gastric, splenic and mesenteric veins drain into?
Hepatic portal vein
Outline the route to the inferior vena cava from the hepatic portal vein
Hepatic portal vein (through the liver) to the hepatic vein and into he inferior vena cava