Gastro Flashcards
4 layers of the GIT?
- mucosa
- submucosa
- muscularis externa
- serosa
Describe structure of musculris externa
Two layers of smooth muscle separates by a nerve complex. Inner layer = circular, outer = longitudinal
What is the difference between the mucosa and subMucosa layers?
Mucosa = innermost layer. Has many ridges in structure (like a wave) that increases surface area for absorption. Also protects from contents of food and secretes compounds for chemical digestion
Submucosa = connective tissue with nerve plexus
Describe peristalsis motility
Involves the alternating contractions of the circular and longitudinal muscles of the muscularis externa layer to propel food forward.
Mediated by=
Glossopharyngeal and vagus nerves
Describe segmentation motility
Mixing of food and digestive juices. Food is sectioned off in little sections that are closed off by circular muscles. The food moved back and forth within this section, mixing with the juices. The circular muscle then relaxes a little, allowing food to move into adjacent sections. The muscle then closes again, repeating the process. Occurs in small intestine predominantly
Glossopharyngeal nerve?
Mediates peristaltic contractions of the esophagus
Functions of oral cavity? (4)
Ingestion, mastication, lubrication, digestion
Describe digestion in the oral cavity
Very beginnings of digestion.
Salivary amylase breaks down carbohydrates
Lingual lipase breaks down lipids
(Both enzymes are found in the saliva)
Describe mastication.
Involves the teeth and tongue. The manual manipulation of food - chewing
Where is the parotid gland located and what does it secrete?
Located near the ear. Secretes salivary amylase (carb breakdown enzyme)
What does the submandibular gland secrete?
Glyoproteins, pH buffers, salivary amylase
What does the sublingual gland secrete?
Mucus - buffering and lubrication
What are the first 2 phases of the swallowing reflex?
- Ingestion
2. Buccal
What are the 3rd and 4th phases of swallowing reflex?
- Pharyngeal
4. Esophageal
Describe ingestion phase of swallowing reflex
Moving food to back of mouth voluntarily
Describe buccal phase of swallowing reflex (3 elements)
Baroreceptors recognise presence of bolus at the back of the mouth and send APs to medulla via trigeminal and glossopharyngeal nerves.
Food is pushed further into pharynx and the uvula closes
Describe pharyngeal phase of swallowing reflex
Glottis closes, preventing food moving into trachea and forcing it into esophagus
Describe esophageal phase of swallowing reflex
Food moves down esophagus towards stomach via peristaltic contractions
- vagus and glossopharyngeal nerves mediate these contractions