Overview of the alimentary system Flashcards
Overall function of digestive system
digest and absorb food
Definition of absorption
Transferring nutrients to the circulation
Which two groups of organs make up the alimentary system?
Digestive tract (oesophagus, stomach, small and large intestine) and accessory organs (salivary glands, gall bladder, liver, pancreas)
What are the three major pairs of salivary glands?
Parotid, submandibular, sublingual
What are the possible consistencies of saliva secretions?
Serous (watery), mucous (thick) or seromucous (mixed)
Function of the gall bladder
Stores concentrated bile (produced by the liver) and releases it into the duodenum when fatty food is consumed (bile emulsifies lipids and neutralises acid).
Description and function of the pharynx
a 12-15cm long muscular tube responsible for the passage of food and air - digestive and respiratory role
Description of oesophagus
a 20-25cm muscular tube which extends from the pharynx to the stomach, passing behind the trachea and the heart)
Description and function of stomach
muscular organ found in UL of abdomen. Churns food and drink to form chyme and secretes HCl and enzymes to digest food.
Function of sphincters
regulates the release of secretions e.g. from oesophagus to stomach or from stomach to small intestine.
What are the 3 parts of the small intestine?
Duodenum, jejunum, ileum
Parts of the large intestine
caecum, appendix, ascending, transverse and descending colon, rectum, anus
What are the layers of the gastrointestinal histology?
Mucosa, submucosa, muscularis externa/propria, adventitia/serosa
Which layers make up the mucosa?
Epithelium, lamina propria, muscularis mucosae
What is the epithelium type in the oral cavity, pharynx and oesophagus and why?
Non-keratinised stratified squamous epithelia - protective against mechanical abrasion
What is the lamina propria?
Thin layer of connective tissue found in the mucosa beneath the epithelial layer. Contains inflammatory cells and provides support and nutrients to the epithelium.
What is the muscularis mucosae?
Layer of smooth muscle continuous throughout the alimentary system (from oral cavity to anal canal). Found in the mucosa beneath the lamina propria, above the submucosa.
What is the submucosa?
Dense irregular connective tissue containing large blood vessels, nerves and lymphatic vessels.
What is the muscularis propria/externa?
Smooth muscle found below the submucosa made up of an inner circular layer and outer longitudinal layer of muscle. Contracts to aid digestion and movement of food via peristalsis.
What is the difference between adventitia and serosa?
Either one is found encapsulating an organ. Adventitia is a fibrous CT layer while serosa is a serous membrane which secretes serous fluid to reduce friction.
Which parts of the digestive system have adventitia?
Oral cavity, upper oesophagus, ascending and descending colon and rectum. Everything else has serosa
What is GORD?
Gastro-Oesophageal Reflux Disease. Continuous reflux of acid from stomach into oesophagus which may cause Barrett’s oesophagus.
Metaplasia definition
When epithelium changes from one type to another - can be part of normal maturation or pathological.
What is Barrett’s oesophagus?
The pathological change of oesophageal-epithelium from stratified squamous to simple columnar epithelium.
What is the risk of having Barrett’s oesophagus?
Risk of dysplasia and oesophageal cancer
What is dysplasia?
The abnormal growth of cells resulting in unequal cell size, abnormally-shaped cells, excess pigment and higher number of mitotic figures.
Which organ of the alimentary system has a secretory function?
Stomach
What are the names of the glands in the stomach?
Gastric glands - cardiac, fundic, pyloric glands
Which layer of the mucosa are glands located?
Lamina propria
What do the secretory cells secrete in the stomach?
HCl, mucus, enzymes, bicarbonate
What is the epithelium type in the stomach?
Simple columnar epithelium
Which organs of the alimentary system have an absorptive function?
Small (and large) intestine