GI principles Flashcards
Which drugs affect gastric secretion (5)
Antacids
Histamine H2 antagonists
Misoprostol
NSAIDs
PPIs
How do antacids work
They reduce symptoms of excessive gastric acid secretion by buffering hydrochloric acid
How do histamine H2 antagonists work
Blocking the H2 receptor reduces hydrochloric acid secretion
How do NSAIDs affect gastric secretion
Inhibit COX-1, thus disrupting the action of prostaglandins
This promotes histamine secretion and therefore hydrochloric acid secretion
how does misoprostol work
is an analogue of prostaglandin E1
How do proton pump inhibitors work
Irreversibly inhibit H+/K+ ATPase pump
Which reduces hydrochloric acid secretion
Give examples of anti-emetic drugs (5)
Antihistamines
Anti-muscarinic
5-HT3 receptor antagonists
Dopamine receptor antagonists
Neurokinin-1 receptor antagonists
Which anti-emetic drugs affect receptors in the GI tract as well as the brain
5-HT3 receptor antagonists
Dopamine receptor antagonists
Neurokinin-1 receptor antagonists
Which drugs affect gastro-intestinal motility (4)
anti-diarrhoeal drugs
Constipation reducing drugs
Laxatives
Faeca softeners
What are examples of anti-diarrhoea drugs
Opiates
What are the types of laxatives (3)
bulk
Osmotic
Stimulant
How do bulk laxatives work (2)
bulk is formed from undigested polysaccharides
The bulk triggers peristaltic reflexes
How do osmotic laxatives work
lead to increased fluid in the bowel
This promotes movement of gut contents
What are Intraperitoneal organs
organ that are almost completely covered by visceral peritoneum
And are therefore minimally mobile
What are retroperitoneal organs
organs only partially covered with peritoneal
(Only on anterior surface)
Describe organs with mesentery
organs covered in visceral peritoneum which forms a double layer
Which GI organs are intraperitoneal
stomach
Spleen
Liver
Duodenum parts 1+4
Jejunum
Ileum
Transverse colon
Sigmoid colon
Caecum
Which GI organs are retroperitoneal
duodenum parts 2+3
Pancreas (not tail)
Ascending colon
Descending colon
Rectum
Where does the oesophagus begin
Inferior edge of cricopharyngeus muscle
Function of the oesophageal plexus
to supply smooth muscle within walls of oesophagus
What does parasympathetic innervation of the oesophagus cause
increased peristalsis
Where does the caecum lie
Right iliac fossa
Where is the appendicitis orifice
Posteromedial wall of caecum
Where does the sigmoid colon lie
left iliac fossa
What is the importance of the levator ani muscle (2)
a skeletal muscle which provides continual support for pelvic organs
Reflexively contracts further if there is an increase in intra-abdominal pressure
Importance of the puborectalis (3)
part of levator ani muscle
Contraction decreases anorectal angle - acts as a sphincter
Helps to maintain continence when rectal ampulla is relaxed and filled
When is the internal anal sphincter relaxed/contracted
contacted - all the time
Relaxed - in response to distension of rectal ampulla
When is the external anal sphincter contracted relaxed
relaxed - all the time
Contracted - along with puborectalis in response to distension of the rectal ampulla and internal sphincter relaxation
What type of muscle makes up the internal anal sphincter
smooth muscle
What type of muscle makes up the external anal sphincter
skeletal muscle (voluntary control)
Which nerve supplies the external anal sphincter
Pudendal nerve
Describe the ischioanal fossae (2)
lie on either side of anal canal
Filled with fat and loose connective tissue
What are the surface lines of the abdominal wall (3)
Linea semilunaris
Linea alba
Anterior superior iliac spine
What direction do the muscles fibres of the external obliques run in
Anteroinferior
What direction do the muscle fibres of the internal obliques run in
anterosuperior
What direction do the muscle fibres of the transversus abdominis run in
Horizontal
Where is the deep inguinal ring found
superior to the midpoint of the inguinal ligament
Where is the superficial ring found
Superolateral to the pubic tubercle
Describe the peritoneal cavity (2)
a potential space of capillary thinness between parietal and visceral layers of the peritoneum
Containing peritoneal fluid secreted by the peritoneum
What is ascitic fluid
Excess fluid collecting within peritoneal cavity
Is the abdominal aorta intraperitoneal or retroperitoneal
Retroperitoneal (only partially covered by peritoneum)
What are the three branches of the abdominal aorta
Coeliac trunk
Superior mesenteric artery
Inferior mesentery artery
where does the coeliac trunk arise
level of t12 vertebral
What are the branches of the coeliac trunk (3)
splenic artery
Hepatic artery
Left gastric artery
What do the lateral branches of the abdominal aorta supply
Kidneys, adrenal glands, gonads, and posterolateral body wall
What is the marginal artery of Drummond
an arterial anastomosis between the branches of the superior mesenteric artery and the inferior mesenteric artery
Describe the blood supply to the liver (2)
Left and right hepatic arteries
Hepatic portal vein
which vessel supplies Hindgut organs
inferior mesentery artery
What is the remainder of the GI trac (past proximal half of anal canal) supplied by (vessel)
internal iliac artery
What is the function of the hepatic portal venous system
To drain venous blood from absorptive parts of the GI tract and associated organs
Takes this blood to the liver for cleaning
Which vessels are part of the hepatic portal venous system
inferior vena cava
Hepatic portal vein
Splenic vein
Superior mesenteric vein
Inferior mesenteric vein
Function of the hepatic portal vein
to drain blood from the foregut, midgut, and hindgut structures to the liver for first pass metabolism
Function of the splenic vein
Drains blood from the foregut structures to the hepatic portal vein
Function of the superior mesenteric vein
to drain blood from midgut structures to the hepatic portal vein
Function of the inferior mesenteric vein
to drain blood from hindgut structures to the splenic vein
What can cause rectal varices
portal hypertension
Collateral veins between portal and systemic venous systems dilate
