Flashcards in GI Deck (145)
Describe the main components of saliva
-Hypotonic solution containing water, mucous and electrolytes, antibodies, amylase and lysozyme, lymphocytes and neutrophils
Give 3 consequences of failure of continuous saliva secretion (xerostomia)
-Bacterial over growth
What physical mechanisms trigger the release of saliva from the major salivary glands?
-Senses ie sight, smell, taste and thought of food
Describe the location of the 3 major paired salivary glands and state whether their secretions are mainly serous, mucus or mixed
-Parotid = in front of ears (preauricular) -> serous
-Sublingual =under tongue -> mucous
-Submandibular = floor of mouth -> mixed
What are the main purposes of saliva?
-Lubrication of food for swallowing
-Maintenance of teeth integrity by neutralising acid
-Iodide is a bacteriostatic
-Initiate digestion of foods by amylase/lipase
Name the ducts of parotid and submandibular glands
-Parotid = stensons (second molar tooth of maxilla)
-Submandibular = whartons (either side of lingual frenulum)
Describe the general secretory units of a salivary gland and what each component does to produce saliva
-Acinus -> secretion of fluid isotonic with plasma
-Striated ducts -> ductal modifiction of isotonic solution by removing Na and Cl and adding K+, I-and HCO3-. ducts are impermeable so water cannot follow
Describe the difference between unstimulated and stimulated saliva
-Unstimulated -> low flow rate provides lots of time to remove Na/Cl and basal hco3 added.
-Stimulated -> high flow rate means limited time to remove Na and lots of HCO3- added
What does the gag reflex test?
-Sensation of soft palate
-Motor innervation of soft palate
Name the two arches anterior and posterior to the palatine tonsils
-Anterior = palatoglossus
-Posterior = palatopharyngeal
Describe the three phases of swallowing
-Oral -> food chewed to form bolus, pushed to back of mouth causing reflex activation of pharyngeal phase
-Pharyngeal -> involuntary control - pharyngeal receptors communicate with swallowing centres in brain causing soft palate to raise and close off nasopharynx, hyoid bone and larynx raise closing epiglottis, food passes into oesophagus
-Oesophageal -> passage through upper oesophageal sphinter causing constriction of sphincter and peristaltic wave causing relaxation of lower oesophageal sphincter
What is achalasia?
-Failed relaxation of lower oesophageal sphincter causing dysphagia
Give 3 common causes of dysphagia
-Stroke causing paralysis of muscles on one side
What is a pharyngeal pouch?
-also known as zenkers diverticulum
-diverticulum of oesophagus through killians dehiscence between cricopharyngeus and inferior pharyngeal constrictor
How does the autonomic nervous system affect salivary glands?
-Parasympathetic -> stimulates acinus and ductal cells to add HCO3-
-Sympathetic -> reduction in bloodflow to glands limits salivary flow
describe the differences in voluntary and unvoluntary control of the oesophagus
-Upper 1/3 voluntary striated muscle
-Lower 2/3 unvoluntary smooth muscle
Describe the results on the GI system of lateral and craniocaudal folding
-Lateral = ventral body wall and pinching from yolk sac
-Craniocaudal = blind ended primitive gut tube from stomatoduem to proctoduem with opening at umbilicus
Of what tissue origin are epithelial linings and musculature of gut wall?
-Epithelia = endoderm
-Musculature = splanchnic mesoderm
What are the adult derivatives of the foregut, midgut and hindgut?
-Foregut -> Oesophagus, stomach, 1st part duodenum, liver, gallbladder, pancreas
-Midgut -> distal 3/4 of duoedenum to 2/3 transverse colon
-Hindgut-> distal 1/3 transverse colon to upper anal canal. also internal lining of bladder and urethra
Describe the branches of the coeliac trunk and which art og the gut it supplies
-Splenic artery (left gastroepiloic, fundus)
-Common hepatic -> proper hepatic (R/L hepatic, cystic), gastroduodenal (superior pancreaticoduodenal, right gastroepiploic) right gastric
-Left gastric (oesopagus)
Describe the main branches of superior mesenteric artery and which part of the gut it supplies
Describe the main branches of inferior mesenteric artery and which part of the gut it supplies
-Continues as superior rectal
Which structures in the gut have a dual blood supply by CT and SMA?
-Duodenum (gastroduodenal and sup. pancreatico duodenal from CT and inf. pancreaticoduodenal from SMA)
-Pancreas (sup. pancreatico duodenal from CT and inf. pancreaticoduodenal from SMA)
What is a mesentery and why is it important? What is the embryonic origin of mesentery? Describe the locations of the dorsal and ventral mesentery
-Double layer of peritoneum which attaches the gut to the abdominal wall
-Allows blood and nerve supply to organs
-Dorsal along length of gut tube, ventral only to foregut
What are omenta and describe their formation?
-Double folds of mesentery formed during rotation of the stomach
-As the stomach rotates clockwise in longitudinal axis it drags the dorsal and ventral mesentery with it producing double folds forming greater and lesser omenta.
-As it rotates on an obligue (AP) axis it puts the omenta into their anatomical positions -> greater hangs from greater curvature of stomach, lesser from lesser curvature of stomach
What lays in the free edge of the lesser omentum?
Where does the liver develop? How does the liver help anatomical positioning?
-Within the ventral mesentery
-Grows so fast and so large within cavity that pushes stomach to left
What is retropetitoneal/secondary retroperitoneal and what organs?
-Retroperitoneal -> organs never within the peritoneum/enveloped in mesentery - abdominal aorta and kidneys
-Secondary retroperitoneal > once within the peritoneum and covered in mesentery but got pushed dorsally and became fused with posterior abdominal wall to loose its mesentery -> distal 3/4 duodenum, ascending/descending colon
Explain the association between the foregut and the respiratory tract
-Resp tract started as a blind diverticular ventral outpuching from the foregut.
-Tracheoesophageal septum gows and separates resp diverticulum from foregut. puts trachea ventrally and oesophagus dorsally