Post on 18-Dec-2021
LECTURE 11 & 12: ABDOMINAL VISCERA
ABDOMINAL CONTENTS
DIVISION
The location of abdominal viscera is divided into 4 quadrants:
- horizontal line across the umbilicus divides the upper quadrants from the lower quadrants
- vertical line from the ziphisternum through the umbilicus to the pubic symphysis divides the
right quadrants from the left quadrants
OESOPHAGUS
- ~25cm long muscular tube that traverses the neck,
thorax and abdomen
o Transfer of food through peristalsis
- Begins at the cricoid cartilage at C6, and then
descends behind the trachea into the posterior
mediastinum
- Descent into the abdomen is through the
oesophageal hiatus in the diaphragm (T10) which
is made from a sling of the left crus on the right
side
o Diaphragmatic contraction closes the
oesophageal hiatus and blocks the reflux
of gastric contents
- Enters the stomach on the right side
- Oesophagus is lined by stratified squamous epithelium which abruptly changes into gastric
mucosa at the gastro-oesophageal junction
- Oesophagus has natural narrowing points along its entire length with specific vessel supply
o Cervical
Upper oesophageal sphincter (narrowing)
Inferior thyroid artery (arterial)
Brachiocephalic and systemic (venous)
Deep cervical nodes
o Thoracic
Aortic arch and left main bronchus (narrowing)
Oesophagus branches from descending aorta (arterial)
Azygous and systemic (venous)
Mediastinal nodes
o Abdomen
Oesophageal hiatus (narrowing)
Left gastric from aorta (arterial)
Left gastric portal with overlaps from systemic
(venous)
Pre-aortic nodes
HIATUS HERNIA
It is not uncommon for herniation of the stomach to occur at the
oesophageal hiatus:
- Paraosoeosophageal hiatal herniation is one sided (5%)
- Sliding hiatial herniation when a portion of the stomach is pulled upwards
STOMACH
- Located in the LUQ
- J shaped organ
o Less curvature is on the medial side
o Greater curvature on the lateral side
- Two openings
o Cardiac orifice is the point in which the
oesophagus enters (proximal part of lesser
curvature)
o Pyloric orifice is the distal opening
- Fundus is a domed shaped projection above the
stomach
o Full of gas
- Body of the stomach
o Extends from the cardiac notch to the angular
notch in the lesser curvature
- Pyloric antrum is a funnel from the body into the pylorus
(most tubular part of the stomach)
o Pylorus is characterised as a strong muscular tube
that functions as the pyloric sphincter
The lumen travelling through is called the
pyloric canal
- Organ is tether to the under surface of the liver from the
less curvature by a mesentery called the lesser omentum,
the greater curvature of the stomach is anchored in the
posterior abdominal wall by a the greater omentum
- Rugae are internal folds within the stomach which are
most prominent at the pylorus
ARTERIAL BLOOD
- Lesser curvature has a right and left gastric artery which
richly anastomose
- Greater curvature has a right and left gastroepiploic
artery which also richly anastomose
DUODENUM
- First part of the small intestine as a C shaped loop (10
inches in total) that encloses the pancreas
- Only the very first portion of the duodenum connecting
to the stomach is intraperitoneal, whilst the
remainder is retroperitoneal
- Primary function of digestion and absorption
- Duodenum is divided into 4 parts:
o Duodenal cap is the first portion and is
directed upwards and backwards over the
right crus, right psoas major and hilum of
the right kidney (2 inches)
Peptic ulcers will usually occur here
o Vertical descending portion is completely
retroperitoneal (3 inches)
Transverse mesocolon is a landmark
found here that encapsulates the
transverse colon
Choledochoduodenal junction if
found half way down inside
Major duodenal papilla is where the bile
duct pancreatic duct enters
Minor duodenal papilla is the accessory
duct to pancreas
o Horizontal part of the duodenum traverses right psoas to
left psoas (4 inches)
Slightly tethered to left psoas
Found at the level of L3
Root of the mesentery found here which anchors
the jejunum and ileum
o The final portion curves upwards on left psoas and comes
forward
Duodenal-jejunal flexure marks the point the
small intestine becomes intraperitoneal with the
jejunum
JEJUNUM AND ILEUM
- 4-6 metres in length
o 2/5 is jejunum and 3/5 is
ileum with no clear
demarcation
o Jejunum tends to be in
the situated in the LUQ
and is larger in diameter
with thicker walls and
higher degree of folding
o Ileum is in the RLQ
- Completely intraperitoneal and
suspended by mesentery
o Attachment to the
posterior abdominal wall
and 3 part of the
duodenum
o Blood supply from the
aorta feeds the small intestine by entering the mesentery
ARTERIAL BLOOD SUPPLY
- Jejunum is supplied by vasarector which arise from a few arcades (long arterial loops)
- Ileum has an abundance of arcades and much smaller vasarector compared to jejunum
LARGE INTESTINE
- The start of the large intestine is at the ileo-
caecal junction
o Ileo-caecal valve is a smooth muscle
sphincter to this opening
- 1.5 metres in length
o Caecum, ascending colon (right
colic/hepatic flexure), transverse colon
(left colic/splenic flexure), descending
colon, sigmoid colon (s-shaped bend),
and the final centred portion is the
rectum (one continuous longitudinal
muscle)
- Unlike the small intestine which is a single
longitudinal muscle coat, the large intestine
consists of three distinct muscle bands called
tinea
o The short banding gives the large
intestine a stacked appear which is
termed haustra
- The large intestine has characteristic fat tags
called epiploic appendices hanging off it
APPENDIX
- Found projecting off from the caecum at the
point in which the three tinea converge
- The tip of the appendix is variable in length
o 1/5 are found hanging off in the pelvic brim = pelvic appendix
o Most are found tucked behind the large intestine = retrocaecal appendix
LIVER
- Largest solid viscera found tucked up behind the costal
margin
- Fills the RUQ
- The anterior surface is smooth and is called the
diaphragmatic surface
o Its transition into the visceral surface is
demarcated by the sharp inferior border
o Divided into two lobes by a falciform ligament
(double folded peritoneum) that connects the
liver the anterior abdominal wall at the level of
umbilicus
Ligametum teres is an obliterated vein
and runs inferiorly
Remnant of umbilicus vein that
used to receive blood from the
placenta
- From the anterior surface the liver is divided into one
large right lobe and one small left lobe, but both are
functionally identical
- The visceral surface is imprinted by all the structures it
sits on and bears the hilum
o H shaped fissure further divides the liver into a
caudate and quadrate lobe
o Gall bladder also found next to the quadrate
lobe
o IVC is found attached to the liver next to the caudate lobe
o Ligamentum venosum is a remnant of the ductum venosum that drained directly into
the hepatic vein (and then the IVC)
HEPATIC HILUM/PORTA HEPATIS
- Hepatic artery is divided into left and right to supply each functional half of the liver (left of
hilar)
- Hepatic duct divides in half to collect bile products from both halves of the liver (right of hilar)
- Portal vein receives blood from the digestive system(middle of hilar and behind the arteries
ducts)
o The hepatic vein is responsible for draining the viscus directly into the IVC
GALL BLADDER
- Sits a groove on the visceral surface of the liver
- Fundus of the gall bladder it its bottom which narrows to
form the body; further narrowing produces the neck and
continues as a duct (cystic duct) to the common hepatic
duct
- Cystic duct and hepatic duct converge to form the common
bile duct which runs between the pancreas and
duodenum, before joining with the pancreatic duct and
emptying at the major duodenal papilla
o the opening of the papilla is controlled by a
complex sphincter, hepatopancreatic ampulla, that
closes when inactive to allow the accumulation of
bile into the gall bladder
PANCREAS
- organ both exocrine and endocrine functions
- functionally broken up into the head, neck, body and
tail
o head fills the C shaped curve of the duodenum
and has an unicinate process that is a landmark
for the superior mesenteric vessels
o body overlies the DJ flexure but is deep the
pylorus of the stomach
o the tail leads to the hilum of the spleen
- the main pancreatic duct will empty into via the major
duodenal papilla, but the accessory duct will empty at
a more proximal at the minor duodenal papilla to drain
the uncinated process
SPLEEN
- Oval shaped organ about the size of a clenched fist (tend
to atrophy over time) in the LUQ
o The spleen overlies ribs 9-11
- Smooth diaphragmatic surface
o Smooth surface is usually demarcated from the
visceral surface by notches on the margin
- The visceral surfaces bears the impressions of the
stomach and kidneys
o Hilar is found on this side
Splenic artery and splenic vein
Splenic artery follows the superior
border of the pancreas