*Physiology 2 Flashcards
Where are the parotid glands located?
Anterior to the ear below the zygomatic arch
What duct carries saliva from the parotid gland to the mouth and where does it connect with the mouth?
Duct of stensen
Enters mouth opposite second maxillary molar teeth
Where are the submandibular glands located?
Medial to the body of the mandible
What duct carried saliva from the submandibular glad to the mouth and where does it enter the mouth?
Duct of Wharton
Enters the mouth under the tongue by lingula frenulum via sublingual caruncula
Where is the sublingual gland located?
Medial to the submandibular glands
What duct arises from the sublingual glands and where does it connect to?
Ducts of Rivinus/ common Bartholin
Connects with Wharton’s duct at the sublingual caruncula
Are salivary glands exocrine or endocrine?
Exocrine (secrete into ducts)
What are the main parts of a salivary gland? (3)
External capsule
Septae separating lobes and lobules
Lobules composed of salivons (the functional unit of the gland)
What are the parts of the salivon? (3)
A secretory acinus
Intercalated duct
Striated duct
What do intercalated ducts combine to form?
Striated ducts
What do striated ducts combine to form?
Excretory ducts
What type of cells is the acinus of the salivon made up of?
Pyramidal-shaped secretory acinar cells which are either:
- serous cells producing a water secretion rich in alpha-amylase
- mucous cells producing a think mucous-rich secretion
What cells surround the acinus?
contractile myoepithelial cells
What is the name of the serous cells at the distal end of a mucous, tubuloalveolar secretory unit of certain salivary glands that secretes lysozyme?
Serous demilunes
What kind of epithelium lines the intercalated ducts?
Cuboidal epithelium
What kind of epithelium lines the striated ducts?
Columnar epithelium
What are the main functions of saliva? (5)
Lubrication
Protection (against bacteria and their metabolic products)
Digestion
Copious secretion prior to vomiting (emesis)
Facilitates suckling by infants
What 3 components of saliva buffers metabolic acids?
Bicarbonate
phosphate
mucus
What component of saliva helps to prevent demineralisation of tooth enamel?
High calcium salt
What coats the teeth reducing bacterial adherence?
Protein
What component of the saliva limits the availability of iron for bacteria requiring iron for growth?
Lactoferrin (chelates iron)
What in the saliva contributes to immunity against bacteria and viruses?
IgA
What 2 enzymes are present in saliva?
Alpha-amylase (ptyalin)
Lingual lipase
What are the main electrolyte constituents of saliva? (7)
Na+, K+, Ca2+, Cl-, I-, PO4(2-) and HCO3-: present at lower concentration than plasma, apart from K+ and HCO3- which are found at higher concentrations
What type of secretions does the parotid glands secrete? (main type of cell)
Serous cells produce a watery alpha-amylase rich solution = 25% of daily secretion
What type of secretion does the submandibular glands secrete? (main type of cell)
Mixed serous and mucous cells produce a more viscous solution that the parotids = 70% of daily secretion
What type of secretion dies the sublingual gland produce? (main cell type)
Mainly mucous cells = thick solution rich in mucous = 5% of total daily secretion
Does HCO3- concentration in saliva (and therefore pH), increase or decrease with increasing rate of secretion?
Increase
Does K+ concentration increase or decrease with rate of secretion?
Decrease
What are the 2 stages involved in the formation of saliva?
Primary secretion by the acinar cells
Secondary modification by the duct cells
What drives the primary secretion of fluid and electrolytes by the acinar cells?
How does this transport ions?
The basolateral Na+K+ATPase
Secondary active transport
Summarise the movement of ions during primary secretion?
Cl- is transported into the cell via the Na+/K+/2Cl- (triple) transporter which raising the intracellular concentration of Cl- creating an electrochemical gradient driving Cl- efflux by facilitated diffusion through the apical membrane Ca2+ activated Cl- channels
Na+ and K+ diffuse into the duct to maintain electrical neutraloty via apical Ca2+ activated K+ channels and the paracellular route, respectively
H20 follows by osmosis
Summarise the movement of ions during secondary modification?
Na+ and Cl- are removed from the primary secretion
K+ and HCO3- are added to the primary secretion
(driven by basolateral Na+/K+ ATPase
What are the 2 categories of ways that secretion of saliva can be stimulated?
What part of the brain does each send afferent signals to?
Simple (unconditioned) eg. chemo-, mechano- receptors (nucleus tractus solitarius in medulla oblongata)
Acquired (conditioned) e.g. think, smell, etc. (cerebral cortex) - this causes efferent impulses via the parasympathetic nerves = stimulation of salivary glands (efferent impulses via salivary glands can also cause stimulation of salivary glands)
What nerve supplies thesubmandibular and sublingual glands?
CN VII
What nerve supplies the parotid gland?
CN IX
What 2 branches of the nervous system stimulate secretion of saliva?
Sympathetic (during stressful times)
Parasympathetic (either by unconditioned or conditioned stimuli)
*each branch produces different secretions
What type of salvia secretions does parasympathetic stimulation cause?
Large volume, watery, enzyme-rich
What is release of parasympathetic saliva mediated by?
M1/ M3 muscarinic acetylcholine receptors and VIP
What is release of sympathetic salvia mediated by?
Alpha and beta 1 adrenoceptors
What type of saliva secretions does sympathetic stimulation cause?
Small volume, thick mucus-rich
What extra smooth muscle layer is present in the stomach?
Oblique (beneath circular layer)
What nerve causes the stomach to relax receptively?
Vagus nerve
What digestion is initiated in the stomach?
Protein digestion (HCl and pepsin)
What is produced in the stomach?
Chyme (food + gastric secretions)
What is the fundus normally filled with?
Gas
What are the rugae of the stomach?
series of ridges produced by folding of the wall of an organ.
What happens to the thickness of the stomach wall as you move from the fundus to the antrum?
It increases (therefore so does the mechanical activity of the stomach)
What type of chyme can pass through the pyloric sphincter?
Semi-liquid chyme
State of the pyloric sphincter during mixing?
Closed
What are the 2 broad categories of factors that influence the strength of antral contraction and therefore movement of chyme through the stomach?
Gastric factors
Duodenal factors
In terms of chyme, what is the rate of emptying proportional to?
Volume and consistency of chyme in the stomach
What does a large volume in the stomach cause? (4) - gastric factors that cause emptying of stomach
Motility due to stretch of smooth muscle
Activity of intrinsic nerve plexuses
Vagus nerve activity
Gastrin release
How can the duodenum delay emptying of the stomach?
Neuronal response (enterogastric reflex) Hormonal response (release of enterogastrones)
What effect does the enterogastric reflex have?
Decreases antral peristaltic activity through signals from intrinsic nerve plexuses and the ANS
What do the enterogastrones do?
Inhibit stomach contraction
What are some examples of stimuli in the duodenum that drive the neuronal and hormonal response = not ready to receive chyme?
Fat
Acid (time is required for neutralisation by bicarbonate secreted from the pancreas)
Hypertonicity
Distension
