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
ridges in stomach are called…
rugae
- found in mucosa layer
- allow for expansion
function of fundus
- holds bolus after it passes through cardia
- doesn’t come in contact with gastric juices (salivary amylase continues to work)
outermost layer of stomach
SEROSA
(visceral peritoneum)
why is muscularis layer in stomach different?
3 layers of muscle
superficial to deep
- longitudinal
- circular
- oblique
4 functions of the stomach
- mixes saliva, food and gastric juices to form CHYME
- serves as reservoir for food before release into SI
- secretes gastric juices containing…
- HCL: kills bacteria
- PEPSIN: begins pr- digestion
- INTRINSIC FACTOR: B12
absorption
- GASTRIC LIPASE: digestion of
triglycerides - secretes GASTRIN into blood: signalling digestive processes in GI tract
gastric glands
- columns of secretetory cells near the base of extensions of the lamina propria
- form narrow chanels: GASTRIC PITS
cells
- SURFACE MUCOUS CELLS
- MUCOUS NECK CELLS
produce alkaline mucous to protect outer stomach layers from stomach acid
- PARIETAL CELLS: release HCL and intrinsic factor
- CHIEF CELLS: release enzymes
entero-endocrine cell
- G CELL: secretes hormone into blood that helps controlm digestive processes
intrinsic factor function
helps with absorption of vitamin B12
function of pepsinogen
helps begin breakdown of proteins
function of gastric lipase
breakdown of triglycerides (fat)
