GI ANATOMY Flashcards
Why is the way the abdominal organs are contained advantageous in function?
Allows protection of organs whilst still allowing flexibility for respiration, posture and locomotion.
How are the abdominal organs contained?
Diaphragm superiority, musculoaponeurotic walls laterally, pelvic muscles inferiorly.
Musculoaponeurotic walls are supported superiorly by the thorax and inferiorly by the pelvic girdle.
What is the mechanism of increasing intra-abdominal pressure? What functions does the increase in pressure allow?
Voluntary or reflexive contraction of the muscular roof and floor and musculoaponeurotic walls of the abdomen.
Allows expulsion of air from the thorax and expulsion of liquid (urine/vomit) or solid (faeces, flatus or foetuses) from the abdominopelvic cavity.
What type of epithelia makes up the peritoneum?
Both layers of peritoneum consist of a single layer of squamous epithelial cells - mesothelium.
From which embryological tissue does parietal peritoneum originate?
Somatic mesoderm.
From which embryological tissue does visceral peritoneum originate?
Splanchnic mesoderm.
Explain the concept of visceral referred pain.
Nocioceptors (2 primary sensory neurones) from several locations converge on a single ascending tract in the spinal cord. Convergence of visceral afferents with somatic afferents at a secondary sensory neurones. Skin is the usual stimulus rather than the viscera so the pain is felt over the corresponding dermatomes.
What is the name given to the doubling up of the visceral peritoneum between the stomach and other organs?
Omenta.
What is the name given to the doubling up of the visceral peritoneum between other organs and the posterior abdominal wall?
Mesentery.
What is the fate of the dorsal mesogastrium?
Persists in jejeunum and ileum as mesentery
NOT ASCENDING COLON (secondarily retroperitoneal)
Persists in transverse colon as transverse mesocolon
NOT DESCENDING COLON (secondarily retroperitoneal)
Persists in sigmoid colon as sigmoid mesocolon
NOT RECTUM
Which viscera are retroperitoneal?
Suprarenal glands Aorta/ IVC Duodenum Pancreas Ureters Colon (ascending and descending) Kidneys Esophagus Rectum
How superiorly does the abdominal cavity extend?
4th intercostal space.
What are the contents of the RUQ?
Superior ascending colon, right transverse colon, right lobe of liver, gall bladder, pylorus, D1-3, head of pancreas, right kidney and supra renal gland, hepatic flexure.
What are the contents of the LUQ?
Left lobe of liver, spleen, stomach, jejeunum, proximal ileum, body and tail of pancreas, left kidney and supra renal gland, splenic flexure, left transverse colon, superior descending colon.
What are the contents of the RLQ?
Caecum, appendix, ileum, inferior ascending colon, right ovary, right uterine tube, ureter, spermatic cord, urinary bladder.
What are the contents of the LLQ?
Sigmoid colon, inferior descending colon, left ovary, uterine tube, ureter, spermatic cord, urinary bladder.
What are the layers of the anteriolateral abdominal wall, superficial to deep?
Skin Camper's fascia Scarpa's fascia Superficial investing fascia External oblique Intermediate investing fascia Internal oblique Deep investing fascia Transversus abdominis Tranversalis fascia Extraperitoneal fat Parietal peritoneum
What are the borders of Hasselbach’s triangle?
Floor - inguinal ligament
Roof - inferior epigastric vessels
Medially - rectus abdominis
What are the borders of the inguinal canal?
Anterior - external oblique
Roof - internal oblique, transversus abdominis
Posterior - transversalis fascia
Floor - inguinal and lacunar ligament
How is the likelihood of herniation decreased by the arrangement of the inguinal canal?
Deep and superficial rings don’t overlap - lie obliquely.
When intra abdominal pressure is increased, the posterior wall is forced against the anterior wall to close the canal.
Into which compartments does the transverse mesocolon divide the abdominal cavity? How are these compartments further divided?
Supracolic
Infracolic - root of mesentery of small intestine divides this into left and right
What are the paracolic gutters?
Free communication between supracolic and infracolic regions, grooves between ascending or descending colon and posterior abdominal wall.
