GI System Flashcards
The GIS absorbs nutrients from food such as?
Fats, proteins, carbohydrates, vitamins, minerals and water
Name the six sections of the GIS?
Mouth and Pharynx Oesophagus Stomach Small intestine Large Intestine Rectum and Anus
Name the GI accessory organs?
Teeth, tongue, salivary glands, gall bladder, liver, pancreas
What is the function of the GIS?
The breakdown and absorption of food
What are the two mechanisms for digestion?
Mechanical digestion and chemical
What mechanisms drive mechanical digestion?
Chewing, mixing, propulsion
What is involved in mechanical digestion?
The breakdown of large food molecules into small molecules.
I.e - Large carbohydrates = glucose
What occurs following mechanical and chemical digestion?
The digestion products are absorbed by epithelial cells, nutrients transferred to blood vessels and thereby delivered to tissues
The structure of the GIS is more or less consistent from start to finish, describe it ?
(Inner to Outer) Mucosa Submucosa Muscularis Serosa
Describe the Mucosa
MUCOSA
Layer of simple columnar epithelial cells
-Lamina propria, containing connective tissue, blood vessels & supportive of epithelial layer
-Muscularis Mucosa - inner muscular layer
Describe the submucosa?
Dense connective tissue, blood vessels and connects mucous to musclaris
Describe the Muscularis?
Composed of inner circular layer that works to narrow the gut followed by outer longitude layer of muscle that works to shorten the gut.
Describe the Serosa?
Outer layer of Gut
Forms mesentery where blood vessels and nerves enter and leave the gut
Describe the function of the oral cavity in digestion?
-Mastication
-Mixing with saliva containing amylase
-Tasting safeguard
-Bolus formation
Pharynx is passage at back of mouth for food and air
Describe the function of the oesophagus in digestion?
Collapsible muscular tube which transports food to stomach with no enzymes or absorption.
Secretes mucous to lubricate and protect oesophagus wall
Projects bolus downwards by peristalsis
What is the function of the lower oesophageal sphincter?
Ring of smooth muscle at entrance of stomach that prevents acid reflux.
Describe the internal wall of the stomach?
It has many folds called to rugae.
What are the functions of the stomach?
i) Food storage
ii) mechanical digestion
iii) Chemical digestion
How does the stomach mechanically digest food?
Waves of smooth muscle contraction that breakdown food and mix it with gastric juice
How does the stomach chemically digest food?
Stomach cells secrete enzymes and hydrochloric acid (HCI) which together create gastric juice
What does the mechanical and chemical breakdown of food in the stomach produce?
Chyme
Describe Peristalsis with reference to the Oesophagus and the Duodema?
Waves of smooth muscle contraction, narrowing behind bolus while relaxing in the front propelling it forward.
Describe the build up of the stomach?
Oesophagus to the Lower oesophageal sphincter. Top section of stomach called cardia alongside fundus. Big middle section is the body followed by Antrum & pyloris. Finally the pyloric sphincter where chyme exits the stomach into the duodema
The epithelial layer of stomach is full of pits called?
Gastric pits
Gastric pits are holes lined by epithelial cells that…
vary in shape and function depending on depth
What are the four types of cell found in gastric pits?
Mucous surface and neck cells
Parietal cells
Chief Cells/Zymogenic cells
G Cells
What are mucous surface and neck cells?
Cells near the entrance of the gastric pit that secrete mucous to protect stomach lining against acidic environment
What are parietal cells?
Cells that secrete HCI and intrinsic factor thereby producing acidic environment
What are chief cells?
They secrete and synthesis digestive enzymes
What are G cells?
At the bottom of gastric pits. They secrete hormone gastrin which stimulates production of HCI
What is the Hepatobiliary System?
A system of GI accessory organs including the Liver, gall bladder and pancreas
Where does the Hepatobiliary Systems meet the GIS?
All of the organs within the hepatobiliary system flow into ducts that are attached to the duodema.
What are some of the function of the Liver?
- Carbohydrate, Lipid, Protein metabolism
- Process of drugs and detoxification
- maintain blood glucose
- synthesis of bile
- store glycogen
What are some of the function of the pancreas?
Secrete pancreatic juice and so buffers against acidic chyme
Contains several enzymes for breaking down food molecules
What does the Biliary system do?
Bile is produced in the liver and stored in the gall bladder.
The hormone CCK causes the gall bladder to release bile into the small intestine.
CCK is released when chyme is detected in the duodema
What is the function of the Small Intestine?
Digestion and absorption of material in the gut.
What are the three parts of the Small intestine?
- Duodema
- Jejunum
- Ileaum
What is the function of the Duodema?
Mix chyme with various enzymes and hepatobiliary secretions.
What is the function of the Jejunum?
Where most SI absorption takes place
What is the function of the Ileaum?
Absorbs vitamin B12 plus any remaining substances
Describe the inner surface of the small intestine?
Folds within Folds within Folds.
i) The immediate surface area has many circular folds.
ii) Circular folds have many villi on their surface. (Villi are finger like projections with blood and lacteal vessels lined by simple columnar epithelium.
iii) Microvilli, which are microscopic hair endings on the apical surface of villi epithelial cells.
Overall this gives the small intestine and absorption area of 250m2
What is the process for small intestine mechanical digestion?
Segmentation - Localised, non-propulsive movements whereby contractions mixes contents with digestive enzymes and contents brought into contact with walls for absorption
Describe the build up of the Large intestine?
Composed of caecum(wee dead end bit next to appendix) ascending colon, transverse colon, descending colon, sigmoid colon, rectum.
What is the Cecum in the large intestine?
A dead end spot in the ascending colon that contains the vermiform appendix?
What occurs to the vermiform appendix during inflammation?
It becomes inflamed giving you appendicitis. The solution is to remove the vermiform appendix.
What are the functions of the large intestine?
- Complete food and water absorption
- form and expel faeces
- Contains a biome of over 300-500 bacteria which produce smelly gas
