Case 11 Flashcards
(44 cards)
What are the two enteric plexi of the gut and what do they do
- Myenteric plexus (Auerbach’s plexus) - primarily regulates gastrointestinal motility, including peristalsis
- Submucosal plexus (Meissners Plexus) - regulates secretory activity, blood flow and absorptions of the mucosa
Go in order of innermost to outermost layers of GI tract
- Mucosa (contains epithelial lining and loose connective tissue called lamina propria which is below the basement membrane of the epithelium)
-Muscularis mucosa (thin layer of muscle that is the fence between the mucosa and sub muscle
- Submucosa (contains dense connective tissue, vessels and nerves aswell as the the submucosal/Meissners plexus$
- Muscularis externa (consists of inner circular and outer longitudinal smooth muscle. Between the inner and outer muscle layers u have the myenteric plexus or Auerbach’s plexus)
- Serosa (mesothelial lining known as the visceral peritoneum, it is the serous lining that makes serous fluid / peritoneal fluid)
What are the movements / what do the movements of muscle layers of the Muscularis externa do to the gut content
The inner circular smooth layer narrows the lumen and pushes the content forward
The outer longitudinal layer shortens the segment of the gut which helps pull the bolus forward
Both layers contribute to segmentation and peristalsis
How is the Muscularis externa controlled
By the pacemaker cells called the interstitial cells of Cajal which are controlled by the ENS
What are the 3 phases of swallowing
- Oral stage
- Pharyngeal stage
- Oesophageal stage
Describe the oral stage of swallowing
Consists of oral preparation and oral transport.
First chewing/mastication occurs if food is present to increase surface area, salivation occurs to lubricant bolus and begin chemical digestion
The front of the tongue then elevates and presses against the hard palate, the tongue pushes the bolus backwards towards the throat by rolling it along the hard palate.
Describe the pharyngeal stage of swallowing
The soft palate is elevated via the levator veli palatini which prevents food from entering nasal cavity
(The vagus nerve stimulates the uvula and levator veli palatini to contract)
The epiglottis tilts downward to cover the laryngeal inlet to prevent food entering the trachea/aspiration
Vocal cords adduct to further protect the airways
Pharyngeal constrictor muscles contract (superior middle and inferior) to propel the bolus downwards
Upper oesophageal sphincter (UES) relaxes which allows food to enter the oesophagus
Describe the oesphageal stage of swallowing
Lasts about 8-10 seconds
Upper oesophageal sphincter (UES) closes which prevents good from regurgitating back into the pharynx
Primary peristalsis begins which are coordinated contractions of the circular and longitudinal muscles of the oesophagus used to push the bolus down and is controlled by the swallowing centre in the medulla by the vagus nerve
Secondary peristalsis may occur if food remains stuck in oesophagus (reflex is initiated by oesophageal stretch receptors (CN 9 and 10))
Lower oesophageal sphincter (LES) then relaxes which allows bolus to enter stomach
LES contacts after bolus passes to prevent gastro-oesophageal reflux (acid reflex/GORD)
Describe the main enzymes in saliva and what glands are responsible for secreting it (and type of saliva)
- For main proteins you have Ptyalin (alpha-amylase) for starch digestion,
lingual lipase for fat digestion and mucous which contains mucins used for lubrication - Submandibular produces 70% of saliva and has a mix of both serous and mucous but predominantly serous (water)
- Parotid produces 20% of saliva is aid mainly serous (very rich in enzymes)
- Sublingual produces 5% of saliva and is mainly mucous
What two cells are salivary glands made up of
Acinar and ductal cells like the exocrine pancreas
Name the two types of salivary glands
- Extrinsic (outside oral cavity)
- Intrinsic (inside oral cavity)
Name 3 intrinsic salivary ducts
- Buccal
- Labial
- Palatine glands
What innervates the parotid gland
Glossopharyngeal nerve (CN 11)
What innervates the submandibular gland
Facial nerve (CN 7)
What innervates the sublingual gland
Facial nerve (CN 7)
What innervates the intrinsic or minor salivary glands
Facial nerve (CN 7)
Where does the parotid duct open into the oral cavity
2nd maxillary/upper molar
Where does the submandibular duct open into the oral cavity
Lingual frenulum which is what anchors the tongue
Where does the sublingual duct open into the oral cavity
10-20 of these ducts and they empty into the floor of the oral cavity
Describe ion movement into the Acinar cells from the blood (basolateral membrane)
On the basolateral membrane (membrane between blood stream and cell) you have the Na+/K+ - ATPsse pump which pump 3 Na+ out of the cell and 2K+ into the cell
On the same membrane you also have Na,K,2CL cotransporter which is a secondary active transport system that allows Na+ to re-enter the cell down its concentration gradient bringing K and Cl with it.
These ions (Na, K and Cl) enter the Acinar cells, water follow Na into the Acinar cell aswell
Finally to maintain the K+ concentration outside the cell to provide for the Na/K pump, you have K+ channels that allow passive diffusion of K+ ions to leave the cell
c
Describe ion movement from the Acinar cells to the lumen/duct of salivary glands (apical membrane)
On the apical membrane you have CFTR proteins that passively diffuse Cl- ions into the lumen. As Cl- enters the lumen a negative charge is created so Na+ enters the lumen via the tight junctions between cells
Aquaporins channels allow water to enter the lumen aswell via osmosis
The final result after the contribution of the Acinar cells is an isotonic saliva
Is the saliva isotonic, hypotonic or hypertonic after the Acinar cells (primary secretion)
Isotonic
Describe the ductal secretion part of producing saliva and its effect on the saliva composition
On the basolateral memberane there’s an Na/K ATPase pump that pumps out 3 Na+ and pumps 2K+ into the cell, this means in the ductal cell you have low intracellular Na+
Because of this Na+ is reabsorbed from the lumen into the ductal cell via Na+ channels. This creates a positive charge inside the ductal cell so Cl- follows through its channel.
Cl/HCO3 protein also exchanges Cl- from the lumen with HCO3- in the basilar cell (Cl- leaves the lumen and HCO3- enters the lumen) (bicarbonate is made from CO2 and H2O via carbonic anhydrase)
Na+ is also exchanged with H+ ions to maintain pH (So Na and Cl leave the lumen and HCO3 and H enter the lumen)
Finally ductal cells aren’t very permeable to water so water cannot follow Na and Cl leading to a hypotonic saliva
Is the saliva isotonic, hypotonic or hypertonic after the ductal cells (secondary secretion)
Hypotonic
