Digestive System Flashcards
What are the 8 compartments of the digestive tract?
1) Mouth
2) Pharynx
3) Oesophagus
4) Stomach
5) Small Intestine
6) Large Intestine
7) Rectum
8) Anus
What are the 3 accessory glands?
1) Salivary glands
2) Liver
3) Pancreas
2 types of digestion that occur in the mouth?
1) Mechanical
2) Chemical (salivary glands)
What are the 3 pairs of salivary glands called?
1) Parotid gland
2) Sublingual gland
3) Submandibular gland
How much saliva is produced in a day?
1 - 1.5 L
What does the PNS stimulate the salivary glands to do?
Stimulates the salivary gland to produce saliva normally
What does the SNS stimulate the salivary gland to do?
Stimulates the salivary gland to produce thick saliva in order for the mouth to become dry and encourage the person to drink
What are the 7 components of saliva?
1) Salivary amylase - initiates carbohydrate digestion
2) Lingual lipase - initiates lipid digestion
3) Mucin - lubricates the bolus
4) Serous fluid - washes the oral cavity so the taste doesn’t lingur
5) Lysozyme - antibacterial
6) Immunoglobulin A - protection against pathogens
7) Bicarbonates - neutralise the oral cavity (prevention against tooth decay)
Where is the oesophagus located?
Extends from the pharynx to the stomach. Sits behind the trachea.
What kind of epithelium lines the oesophagus?
Stratified squamous epithelium
What muscles are in the walls of the oesophagus?
1) Smooth
2) Mixed
3) Skeletal
Where is the stomach located (in terms of abdominal regions)?
In the epigastrium and extends into the left hypocondrium
What are the 6 functions of the stomach?
1) Stores food
2) Mechanical digestion
3) Chemical digestion
4) Absorption (e.g. alcohol)
5) Hydrochloric acid (to kill micro-organisms)
6) Production of an intrinsic factor (allows Vitamin B12 to be absorbed as it will bind to this intrinsic factor)
Can we live without our stomach?
Yes - as long as we are given B12 injections
Anatomy of the stomach contains:
1) Abdominal oesophagus
2) Cardia
3) Fundus
4) Body
5) Lesser Curvature
6) Greater Curvature
7) Antrum
8) Pyloric canal
9) Pyloric Sphincter - thick & strong
10) Duodenum
What are the special features of the stomach?
Rugae (folds) - in the mucosa & submucosa layer
3 types of muscle (oblique, circular, longitudinal) - in the muscularis externa layer
The cells of the mucosa layer are split into 2 regions that form:
1) Gastric Pit
2) Gastric Glands
What cells are contained within the gastric pit and their function?
Mucous cells and mucous neck cells - both secrete mucous in order to:
1) Form a mucous layer which allows cells to be protected from the acid secretions in the stomach
2) They are in tight junction with each other so that acid in the stomach does not pass through to tissue layers underneath.
What cells are contained within the gastric glands and their functions?
1) Parietal cells - secrete hydrochloric acid and intrinsic factor
2) Chief cells - secrete pepsinogen (which is converted to pepsin by hydrochloric acid and pepsin breaks down proteins into amino acids)
3) Enteroendocrine cells - secrete gastrin (hormone)
Why doesn’t the chief cells (in the mucosa layer of the stomach) secrete pepsin?
As if it was to secrete pepsin, it would break down the chief cells as they are made of protein. Therefore, it secretes the inactive form of pepsin - pepsinogen.
Collectively, what do the secretions from the cells making up the gastric gland produce?
Gastric juice
How much gastric juice do the gastric glands produce, in a day?
1.5-2L
What 4 things stimulate the secretion of gastric juice?
1) Low pH
2) Gastrin
3) Histamine
4) Acetylcholine
What 3 things are contained in gastric juice?
1) Hydrochloric acid
2) Intrinsic factor
3) Gastrin
Where is hydrochloric acid secreted from and its function?
Parietal cells. Function: 1) Kills microbes 2) Breaks down connective tissue (meat) and cell walls (plants) 3) Activates pepsinogen into pepsin
Where is intrinsic factor secreted from and its function?
Parietal cells:
Function: Bind to Vitamin B12 so that is can be absorbed
Where is gastrin secreted from and its function?
Enteroendocrine cells (will secrete gastrin when food is present in the stomach):
Function:
1) Stimulates the secretion of gastric juice
2) Stimulates contraction of the muscle layers in the muscular externa layer of the stomahc walls
3) Works on the pyloric sphincter
Do the parietal cells produce hydrochloric acid directly?
No - they will produce hydrogen (which will then bind to chloride - to produce hydrochloric acid)
What are the 3 stages of gastric activity?
1) Cephalic stage - sight, smell and taste senses food which results in the secretion of saliva
2) Gastric stage - gastrin is secreted from the enteroendocrine cells as food enters the stomach
3) Intestinal stage - Less gastric juice is secreted into the stomach as food goes into the intestines
Where is the peritoneum by the pancreas?
The peritoneum is only infront of the pancreas (therefore the pancreas is = retroperitoneum)
Where is the pancreas located?
Behind the stomach. And sits in the curve of the duodenum
Where does the pancreatic duct (contained in the pancreas) open up?
The pancreatic duct will open up into the duodenum (via the sphincter of Oddi)
What are the 2 types of glands in the pancreas gland?
1) Exocrine gland - 99%
2) Endocrine gland - 1%
What are the 2 types of cells that make up the exocrine gland in the pancreas and their functions?
1) Acini cells = contain Zymogen granules - which produce and secrete
- Propeptidase (breaks down protein)
- Lipase
- amylase
- ribonuclease and deoxyribonuclease
2) Duct cells = secrete water and sodium bicarbonate (which will increase the pH of the chime in the duodenum from the low pH - produced from the gastric acid)
Which 2 cells make up the endocrine gland of the pancreas gland?
Islet of Langerhans:
a cells - secrete glucagon
b cells - secrete insulin
Where is the liver located?
Liver is located in the right hypocondrium and extends into the epigastrium
What are the 4 lobes of the liver?
Anterior - right (bigger side) and left lobe
Posterior - caudate lobe and quadrate lobe
Where is the gall bladder located in the liver?
Posterior - sits on top of the quadrate lobe
What are the 3 functions of the liver?
1) Bile production
2) Blood clotting
3) Blood cell production
When does the liver produce bile?
ALL THE TIME
What is the function of bile?
To break down the fats in the duodenum
What is the function of the gall bladder?
To store and concentrate the bile that is being produced by the liver but isn’t being used to break down the fats in the duodenum.
How much concentrate bile can the gall bladder store (and what helps the gall bladder to store this much)?
40 - 70 ml (rugae allows the walls of the gall bladder to expand)
What is the biliary tree?
A collection of ducts which connects the liver with the gall bladder and the duodenum.