abdominal pain Flashcards
what are the 3 phases of gastro-intestinal tract function?
- cephalic - gastric secretions that occurs before food enters stomach
- gastric - digestive secretions after you swallow food, stimulated by increase in stretch and pH of stomach
- intestinal - duodenal response to arriving chyme
- co-ordinated function of the GIT by integration of neural and hormonal signals
- temporal overlap between phases and feed-back/forward pathways
what are the 3 types of cells in a salivary gland and what is their role in salivation
- Acini cells:
- secrete primary isotonic secretion
- NA+, Cl-, K+, HCO3-
- amylase ad mucin production - myoepithelial cells:
- stimulate ejection of primary secretion into duct - duct cells:
- secondary modification into hypotonic solution
- reabsorb Na+, Cl-
- add K+
- HCO3- altered depending on flow rate (high = increases, low = decreased)
what are the primary regulatory events in the cephalic phase?
BRAIN HIGHER INTEGRATING CENTRES: smell, think, see food
parasympathetic branch:
- increases saliva secretion
- increases HCl, mucus, pepsin, gastrin secretion in the stomach
- stimulates bile ducts, hepatocytes and pancreatic acinar cells
sympathetic branch:
- increases blood flow to glands and saliva production
- increase blood flow to stomach
what are the primary regulatory events in the gastric phase?
FOOD ENTERS STOMACH
inputs:
- parasympathetic pathways
- decreased acidity in stomach due to buffering of food
- distention of antrum
- protein, peptides and amino acids
cause:
G cells -> gastrin
effect:
- increase gastric motility
- increase parietal cells secretion of HCl
- trophic maintenance of GI epithelium
- negative feedback: HCl to G cells
what are the primary regulatory events in the intestinal phase?
PRESENCE OF FOOD IN DUODENUM
- duodenal peptides/ amino acids cause release (pH>3) or inhibit (pH<2) gastrin
- duodenal fats and breakdown products cause release of secretin and Cholecystokinin
- acid entering intestines causes secretin release
what factors increase or decrease secretion of saliva?
increase:
- parasympathetic (dominant in normal situations - large vol of watery, enzyme rich saliva)
- sympathetic (dominant in stressful situation - small vol of thick mucousy saliva)
decrease:
- sleep
- dehydration
- atropine
what factors increase or decrease gastric secretion (HCl, pepsinogen, mucous and intrinsic factor)?
increase :
- gastrin
- acetylcholine
- histamine
- parasympathetic
decrease:
- H+ in stomach
- chyme in duodenum
- somatostatin
- atropine
- cimetidine
- omeprzole
what factors increase and decrease the secretion pancreatic secretions (HCO3-, lipase, amylase and proteases)
increase:
- secretin
- cholecystokinin (potentiates secretin)
- parasympathetic supply
decrease:
-sympathetic supply
what factors stimulate biliary secretion (bile salts, pigments, cholesterol, phospholipids, HCO3-)?
- secretin (bile production),
- cholecystokinin (gallbladder contraction; relaxation of sphincter of Oddi)
- some central and enteric nerve input
what factors increase and decrease secretions in the large intestines (alkaline mucus (no digestive enzymes))?
increase:
- acetylcholine
- vasoactive intestinal peptide
decrease:
- adrenaline
- somatostatin
describe the 2 phases of swallowing
- oropharyngeal (1sec)
- oral phase: holding of formed bolus by tongue against hard palate
- oral transit phase: lifting bolus onto front of tongue then pushing it towards pharynx (all or nothing reflex as it enters pharynx)
- pharyngeal phase: elevation and retraction of velum (soft palate) + velopharyngeal closure. movement of base of tongue and pharyngeal muscles push bolus further, larynx closes and upper oesophageal sphincter opens - oesophageal (4-10secs):
- brain (swallowing centre in medulla) triggers primary peristaltic wave
- circular muscles behind and longitudinal in front of bolus
- secondary wave if food is sticky or lodged (more forceful)
name the different cells types of an oxyntic (gastric) gland found in the fundus/body of stomach and their secretions. what other cells are found in the stomach?
Chief cells secrete pepsinogen
parietal cells secrete HCl and intrinsic factor
mucous neck cell secrete mucous
G cells in antrum secrete gastrin (to circulation)
mucus cells in antrum secrete mucous
HCl secretion is inhibited when it is no longer required i.e. when the food enters duodenum. What other way is it inhibited?
via somatostatin
direct pathway: binds to parietal cells
indirect pathway: inhibit histamine and gastrin release (gastrin triggers HCl release)
what stimulates pepsinogen secretion and what activates it?
- response to vagal stimulation
- triggered by local H+
HCl activates pepsinogen to pepsin
what is the most serious consequence of loss of secretory function of the stomach?
pernicious anaemia
intrinsic factors required for vitamin B12 absorption by receptor mediated endocytosis
what are the cells involved in pancreatic secretion?
centroacinal cells:
-secrete aqueous component
acinar cells:
-secrete enzymes: pancreatic amylases and lipases in active form. pancreatic proteases in inactive form (activated in duodenum)
duct cells:
- secrete aqueous component
- modification of ion component (rich in HCO3-)
what are the 3 major pancreatic proteolytic enzymes initially stored in zymogens to prevent self digestion?
- trypsinogen- activated by enterokinase in enterocytes and trypsin itself via +ve feedback -> trypsin
- chymotrysinogen - activated by trypsin -> chymotrypsin
- procaroxypeptidase - activated by trypsin -> carboxypeptidase
what triggers pancreatic acinar cells to produce enzymes and ductal cells to produce ions (e.g. HCO3-)
acinar cell trigger = cholecystokinin secreted by I cells of duodenum in response to amino acids, small peptides and fatty acids (potentiated by vagal Ach)
ductal cell trigger = secretin from S cells of duodenum in response to chyme reaching duodenum (potentiated by vagal Ach and CCK)
relate CCK and secretin production to bile secretion and effect
CCK triggers release of stored bile, gall bladder contraction and sphincter of Oddi relaxation. leads to digestion
secretin triggers HCO3- rich bile secretion. leads to neutralisation of H+ in duodenum and micelle formation
define retropulsion, segmentation and haustration of the GIT
retropulsion =Stomach contractions originating at antrum and going backward, to prevent too rapid of gastric emptying
segmentation = Mixing and churning of materials without propelling them forward in the tract. predominately in small intestine
haustration = Slow segmental movements that move food very slowly through colon. This movement is going on continually
A person may feel uncomfortable when they are too full, or they are very hungry. Explain why this may be
- Too Full – the receptive relaxation quality of the stomach means that we can store a lot of food without altering pressure -> signals to the feeding and satiety centers in the hypothalamus and appetite center in the amygdala take time to register as it doesn’t just depend on stretch receptors but a lot of other signals combined -> you can continue to eat without realizing that you have reached your limit
- Too Hungry? Peristaltic waves from the fundus to the body to the antrum of the stomach cause this uncomfortable feeling when the stomach is empty
what conditions cause changes in capillary pressures resulting in oedema?
- cardiac failure: raise in venous pressure -> less osmotic pressure pulling fluid back into the capillaries
- liver failure: less albumin concentrating in the circulation -> smaller osmotic pressure
- leaky capillaries in anaphylaxis or sepsis
define insensible fluid loss
Water loss that can’t be measured e.g. trans epidermal diffusion and evaporative loss from respiratory tract
give examples of disease processes that will increase fluid losses
- anything that increases respiratory rate e.g. COPD, sepsis, CF, asthma
- burns
- infections e.g. pyrexia
- diarrhoea (e.g cholera)/ vomiting
- diabetes: polyuria
what 5 steps should you think about before prescribing fluids?
1) What is the condition they are suffering from?
2) Does it cause fluid loss?
3) Does the treatment they are receiving cause water loss e.g. diuretics?
4) Are they under filled, over filled, or normal fluid levels? (your review history and symptoms and signs – think of hypovolemic and over loaded symptoms)
5) Do I have to give them IV fluid or can I give oral fluid? (oral fluid is safer)
list hypovolemic and hypervolemia signs (e.g. think vital signs)
hypovolemic:
- postural BP!
- hypotension (<100mmGh)
- tachycardia (>90bpm)
- capillary refil >2secs
- tachypnoeic (20breaths/min)
- low urine output (<0.5mls/kg/hr)
- dry mucous membranes
- response to passive leg raise
hypervolemic:
- oedema
- dyspnoea
- orthopnoea
- raised JVP
- inspiratory crackles at lung bases
- Hx of cardiac or renal problems
What investigations may be useful to determine volume status?
*think is my pt’s kidneys or heart failing?
- FBC (check Hb if lost blood volume)
- U&E’s (if kidney failing would see rise in urea and creatinine and fall in eGFR)
- CXR (sign of heart failure)
- lactate (raised in hypovolemic shock)
- urine biochemistry (concentrated urine if kidneys failing)
what’s the difference between a colloid and crystalloid fluid?
colloid contains big protein particles that enter the IV space and stay there. resuscitation fluid that can be administered quickly (administration of 500ml but reassess after 15mins (can repeat up to 2L)). high risk of anaphylaxis
crystalloids can pass freely through semi-permeable membrane and are usually for maintenance
what cautions must you take when prescribing fluids?
- Weight of patient
- Elderly or frail
- Renal impairment
- Cardiac failure
- Malnourished or at risk of refeeding syndrome