M16: Digestive System - Salivary Glands, Swallowing & Stomach Flashcards
two types of glands that secrete saliva into oral cavity
- Glands within mucous membranes of oral cavity
- LABIAL (lips)
- BUCCAL (cheeks)
- PALATAL (palate)
- LINGUAL (tongue) - Glands outside the mouth (empty their contents into ducts which deliver saliva into the oral cavity)
3 pairs
- PARATOID
- SUBMANDIBULAR
- SUBLINGUAL
parotid glands structure + function
- largest external salivary glands
- dump into area of 2nd molar
- inferior and anterior to ear
- produce most watery saliva (with lots of salivary amylase)
submandibular glands structure + function
- external salivary gland
- beneath base of tongue
- ducts beside lingual frenulum
- less liquid saliva because more mucous
sublingual glands structure + function
- external salivary gland
- superior to sublingual, floor of mouth
- series of ducts that reach floor of mouth
- thick saliva with little salivary amylase
saliva structure and function
Structure
- 99.5% water
- 0.5% solutes (mostly ions), LYSOZYME (antibacterial agent), IgA (immune function, attacks microbes)
Function
- dissolves food for tasting
- mucous - lubricates food
- CI- activates salivary amylase
- HCO3- (bicarbonate) buffer acidic foods
how do we increase salivation?
- parasympathetic stimulation
- Facial (VII) and Glossopharyngeal (IX) nerve stimulate salivary glands
- cerebral cortex (sensory stimulation like sight/smell)
how do we reduce salivation
sympathetic stimulation
mechanical vs chemical digestion in mouth
MECHANICAL
- breaks food into pieces
- mixes with saliva to form a BOLUS
CHEMICAL
Salivary amylase
- begins starch digestion (polysaccharides to disaccharides)
- when swallowed, stomach acids deactivates it
Lingual lipase
- secreted by glands in tongue
- activated by stomach acids
- begins breakdown of triglycerides into fatty acids and glycerol
order of structures that bolus moves through
- mouth: bolus formed from chewing
- pharynx: movement into pharynx begins deglutition (facilitated by saliva and mucous)
- esophagus: secretes mucous
histology of esophagus
Mucosa
- stratified sqamous
- terminal end has mucous glands
Submucosa
- mucous glands
Muscularis
- upper 1/3 is skeletal muscle
- middle is mixed
- lower 1/3 is smooth muscle
- UPPER ESOPHAGEAL SPHINCTER (skeletal)
- LOWER ESOPHAGEAL SPHINCTER (smooth)
ADVENTITIA (outer layer)
- areolar connective tissue
deglutition
swallowing
3 stages of swallowing (deglutition)
- VOLUNTARY STAGE
- bolus pushed into oropharynx - PHARYNGEAL STAGE (involuntary)
- sensory nerves send signals to deglutition centre in brainstem (medulla oblongata)
- soft palate lifted to close nasopharynx
larynx lifted up and epiglottis bent to cover glottis - ESOPHAGEAL STAGE
- bolus enters esophagus
- upper sphincter relaxes when larynx is lifted
peristalsis pushes food down
- circular fibres contract behind bolus
- longitudinal fibres shorten distance in front of bolus
-lower sphincter relaxes as food approaches
duodenum structure function
first portion of small intestine that attaches to stomach
curves in shape of stomach are called…
greater curvature
lesser curvature
4 main regions in stomach
CARDIA
- closest to esophagus
FUNDUS
- superior to cardia, forms pocket at top of stomach
BODY
- main and largest part
PYLORIC PART:
- 3 parts, leads to SI
1. PYLORIC ANTRUM
2. PYLORIC CANAL
3. PYLORUS (into SI)
- PYLORIC SPHINCTER: controls movement from stomach into SI
