Gastrointestinal Tract- structure and function Flashcards
What are related organs in the GI tract
Salivary glands, liver, gall bladder and pancreas
What are the main components of the upper GI tract
- Epiglottis protects the respiratory system 2. Pharynx 3. Larnyx 4. Oral cavity- surprisingly small hole 5. Tongue 6. Oral cavity
What are the 3 main functions of the GI tract
- Mixing food with saliva 2. Mastication 3. Gustation
How much saliva is produced per day
500-900 mls
Why is there so much saliva produced daily
To keep the oral cavity lubricated
What is saliva
A mixture of water and mucous
What does saliva contain
Electrolytes and amylase
Why is amylase contained in saliva
For starting the process of dissolving food so it can react with taste buds
What is saliva produced by
Salivary glands
What is mastication
Chewing
The coordination of which 6 components is required during mastication
Teeth, jaw, tongue, cheeks, palate, lips
What does mastication produce
A bolus of food to be passed into the oesophagus
What is gustation
The sense of taste
Which nerves innervate the taste receptor organs
Cranial nerves 7 and 9
Where are taste receptor organs located
On the top of the tongue
What are the 5 types of taste receptors
Salt, sweet, sour, bitter, umami
What does the sense of taste inform you of
Whether a foodstuff will benefit you or not
What can the taste and smell of food combine to stimulate
Secretion of saliva and gastric acid or vomiting
Which nerves control all GI functions that take place in the mouth
The cranial nerves
What are the layers of the GI tract (Send Mr Larry Coulsen Some Magnificant Loving Electric Vinyls)
Serosa Muscularis externa Longitudinal muscle Circular muscle Submucosa Muscularis mucosae Lamina propria Epithelium Villus
Which nerves control the gut wall
Myenteric plexus and submucosal plexus
What does the myenteric plexus control
Muscle contraction
What does the submucosal plexus control
The muscularis mucosae
What makes up the gut lining
Villus and epithelium
What combines to move food from the oral cavity to the anus
Myenteric plexus, longitudinal muscle and circular muscle
How are arteries, veins and nerves transmitted into the intestine
Via teh mesentry
What is the first phase of swallowing
Formation of the bolus
What is the second phase of swallowing
Ensuring the bolus enters the GI tract not the respiratory tract
What is the role of the epiglottis
Guiding the bolus into the oesophagus
What does the oesophagus do
Receives bolus of food and pushes it down to the stomach
What does the stomach do
Stores food, digests it with acid, churns it up (to break it down). Passes it to the duodenum of the small intestine
What does the SI consist of
Duodenum, ileum and jejunum
Where does the SI receive ducts from
Pancreas, liver and gall bladder
What is the role of the Si
To complete digestion and absorb nutrients
What does the large intestine consist of
Colon and rectum
What is the role of the LI
To absorb water and electrolytes and create faeces
How is faeces expelled
By the rectum through the anal canal
What is a sphincter
A thickening of the circular layer of the muscularis externa
What are 3 different sphincters in the GI tract
Oesophageal sphincter. Pyloric sphincter. Sphincter of Oddi
What is the role of the pyloric sphincter
Preventing HCl from entering the duodenum
What is the role of the oesophageal sphincter
Prevents HCl from entering the oesophagus
When does the sphincter of Oddi open
When food is present in the duodenum
What is peristalsis
The moving of the GI contents from oral -> anal by contractions of the muscularis externa
What 2 things must the musculature stomach be able to do
- Expand greatly. 2. Help break up the food by churning the contents of the stomach.
How is the stomach able to carry out its muscular functions
- The relaxation of the smooth muscle in the muscular externa 2. The presence of an extra oblique smooth muscle layer
Why are there villus on the small intestine mucosa
To increase the surface area for absorption of nutrients
Describe the anatomy of the small intestine
Villus, lacteal, blood capillaries, goblet cell, intestinal gland
What is the functional relationship of the pancreas to the GI tract
Secretion of pancreatic juice from the exocrine system into the pancreatic duct then into the duodenum
How does pancreatic juice enter the duodenum
Via the sphincter of Oddi
What is the functional relationship of the liver to the GI tract
- Receiving substances absorbed from the small intetsine via the hepatic portal vein. These substances are metabolised. 2. Produces bile 3. Transfers waste products of metabolism to the gall bladder
Describe the hepatic portal system
Splenic vein and superior mesenteric vein -> hepatic portal vein -> liver. Liver -> hepatic portal veins -> inferior vena cava -> heart -> abdominal aorta -> proper hepatic aorta
What is the functional relationship of the gall bladder to the GI tract
Secretion of bile into the duodenum. The bile duct joins the pancreatic duct.
What is the secretion of bile regulated by
The sphincter of Oddi
Outline the immune system of the GI tract in terms of where lymphoid tissue is found
- In the tonsils and adenoids of the oropharynx 2. In Peyer’s patches in the SI 3. In lymphoid tissue in LI
Why is lymphoid tissue in some of the mucosa of the GI tract
To detect antigenic material in the GI tract and to initiate antibody-mediated and cytotoxic immune responses. They all produce classes of antibodies
What does the submucosa plexus do
Innervated secretory cells in the mucosa and contains sensory neurones that monitor the pH and chemical composition of the GI tract contents
How do both plexuses act
Auntomonously
What regulates both plexuses
They sympathetic and parasympathetic divisions of the ANS
