Lecture 1 Flashcards
What are the 4 key functions of the GI tract?
Motility, secretion, digestion and absorption
What motility occurs in the oral cavity?
Chewing and swallowing
What secretion occurs in the oral cavity?
Mainly amylase, some lingual lipase and some protease.
What digestion occurs in the oral cavity?
Mainly of carbohydrates by salivary amylase. only some digestion of lipids and proteins
Is there any absorption in the oral cavity?
No
What is the motility of the oesophagus called?
Peristalsis
What are the three types of salivary gland?
Parotid, submandibular and sublingual
What type of saliva is secreted by the parotid salivary glands?
Watery
What type of saliva is secreted by the sublingual glands?
Thick mucus saliva
What type of saliva is secreted by the submandibular glands?
Mixture of both watery and mucus
What motility occurs in the stomach?
Peristalsis
What do parietal cells secrete?
HCl and intrinsic factor
What is the purpose of HCl?
Activates pepsin and is antibacterial
What does intrinsic factor do?
Complexes with vitamin B12 to aid its absorption
What do chief cells secrete?
Pepsinogen and gastric lipase
What does pepsinogen do?
Activated by low pH to pepsin for protein digestion
What does gastric lipase do?
Digests fat
What do D cells secrete?
Somatostatin
What does somatostatin do?
Inhibits gastric acid secretion
What do G cells secrete?
Gastrin
What does gastrin do?
Promotes gastric acid secretion
What do mucus neck cells secrete?
Mucus and bicarbonate
What does mucus do?
Physical barrier between epithelium and lumen contents
What does bicarbonate do?
Buffers gastric acid to protect the epithelium
What do ECL cells secrete?
Histamine
What is histamine for?
Stimulates gastric acid secretion
What 2 main substances are digested in the stomach?
Fats and proteins
What can be absorbed in the stomach?
Alcohol and lipid soluble substances/drugs like NSAIDS.
What is motility like in the small intestine?
Slow which allows for time for mixing up with enzymes and bicarbonate secretions
What organs secrete substances into the small intestine?
The pancreas secretes enzymes and bicarbonate, the gall bladder secretes bile.
What secretions occur in small intestines?
Mucus from goblet cells, hormones such as CCK, secretin and GIP
What is digested in the small intestines?
Carbohydrates, fats, polypeptides, nucleic acids
How are proteins absorbed in the small intestine?
Active transport
How is glucose, fructose and amino acids absorbed?
by secondary active transport.
How are fats absorbed?
Simple diffusion
How are vitamins and minerals absorbed?
Active transport
How is water absorbed?
Osmosis
What is the main function of the large intestine?
Fluid absorption
What is secreted in the large intestine?
Mucus from goblet cells
What is the external layer of the GI tract?
Serosa which is connective tissue
What are the two layers of muscle?
Longitudinal and circular
What nerve plexus sits between the two layers of muscle?
Myenteric plexus
What nerve plexus sits below the circular muscle?
Submucosal plexus
What layer is below the circular muscle?
Submucosa
What is within the submucosa?
Glands
What does the myenteric plexus control?
Motility
What does the submucosal plexus control?
Secretions from glands
What is below the submucosa?
The muscularis mucosa
What is under the muscularis mucosa?
Lamina propria
What is under the lamina propria?
Epithelium
