Upper Gi tract structure and function Flashcards
Give 2 reasons why we chew
to prolong taste
defend against respiratory failure
In what 2 ways is chewing controlled?
Somatic nerves innervate skeletal muscle voluntarily
Reflex - pressure of food on parts of the mouth initiating mechanoreceptors
How many pairs of glands secrete saliva and what are they?
3 - submandibular, parotid and sublingual
What is the major component of saliva?
water
What 2 substances found in saliva mix to form mucus?
mucins and water
What are mucins?
Major protein component in saliva
What else is found in saliva?
alpha amylase to form maltose
electrolytes for pH balance
Lysozyme to kill bacteria
Are salivary glands endocrine or exocrine?
exocrine
What are the 3 types of alveoli found in salivary glands?
mucous, serous and mixed
What nervous system is stimulatory for saliva production?
both
What nerves control parasympathetic innervation of saliva production and what saliva is produced?
glossopharyngeal (4) and facial (7) cranial nerves
profuse, watery
What nerves control sympathetic innervation of saliva production and what saliva is produced?
adrenoreceptors (alpha1 - high mucus and beta 2 - high amylase) - low volume and viscous
What reflex is due to food being in the mouth on saliva production?
chemoreceptors and mechanoreceptors
What kind of epithelium line the mucosa of the oesophagus?
non keratinising stratified squamous epithelium
Explain the muscles in the muscularis externa in the oesophagus (smooth, skeletal)
smooth in the lower 2/3 and skeletal above to help with swallowing
What does the upper and lower oesophageal sphincters control?
upper - prevent regurgitation into the airway
lower - control entry into the duodenum
What are the 3 stages of getting food to the stomach?
oral, pharyngeal and oesophageal
What is the oral phase monitored by?
voluntary as bolus is put to the back of the mouth by the tongue
What muscles contract and how to help with swallowing?
pharyngeal muscles coordinated by medulla swallowing centre
What closes off the nasopharynx?
soft palette
What closes off the larynx?
epiglottis
What does the UOS contracting prevent?
reflux
How long and by what means does the bolus get from oesophagus to stomach?
10 seconds
peristaltic wave
What causes the relaxation of the stomach?
As the LOS relaxes and the food enters
vagal reflex relaxes smooth muscle of fundus and body
How does the stomach not change in pressure when going from a volume of 50ml to 1500ml?
Gastric rugae unfold
What are some functions of the stomach?
temporary store, dissolve food and digestion, control small intestine delivery, sterilisation and produce intrinsic factor
Why is intrinsic factor produced from the stomach important?
Important for vitamin B12 absorption
Explain the difference between muscle found at the top and bottom of the stomach
stretchy smooth muscle at the top and thick powerful muscle at the bottom to break down larger molecules
What is the additional layer found in the muscularis externa in the stomach? What does this allow?
oblique
like wringing a cloth
Where is the cardicac region of the stomach close to?
The heart
Where is the antrum of the stomach?
Basically the pyloric region
What layers is the rugae present in the stomach?
mucosa and submucosa
What are present in the lumen of the stomach?
mucus cells with gastric pit invaginations feeding into gastric glands
What are the 3 types of gastric glands?
chief, parietal and mucus neck cells
