GI Anatomy Flashcards
What is the abdominal cavity and thorax separated by?
The diaphragm
Which cavity lies inferior to the abdomen and is continuous with it?
The pelvic cavity
What organs does the abdominal cavity contain?
- Gastrointestinal tract (Stomach, small intestine, large intestine, esophagus)
- Hepato biliary system (Liver, bile duct, gallbladder)
- Endocrine system (adrenal gland, pancreas)
- Great vessels (abdominal aorta, inferior vena cava, and their branches)
- Urinary system (kidneys and ureters)
- Spleen (a haematopoietic and lymphoid organ)- it controls the level of blood cells (it removes old or damaged red blood cells) and fights invading germs in the blood (has infection fighting white blood cells)
What are the anterior, posterior and lateral walls of the abdominal wall composed of?
- What else contributes to the structure of the posterior abdominal wall?
- Skin
- Subcutaneous tissue
- Muscles and their associated aponeurose (flat tendons)
- The 5 lumbar vertebrae contributes to the posterior abdominal cavity
What are the 3 functions of the abdominal wall?
- To protect abdominal viscera
- To increase intraabdominal pressure (for things like defecation and birth)
- Maintains posture and moves the trunk (abdomen)
What are the layers from the skin to the parietal peritoneum?
Additionally, what does the the 3 muscle layers aponeurose to form?
- Skin
- Subcutaneous tissue
- External oblique (and fascia)
- Internal oblique (and fascia) (and rectus abdominis should be same depth)
- Transversus abdominis
- Transversalis fascia
- Parietal peritoneum
- The rectus sheath is formed by fascia from the 3 muscle layers, with the rectus abdominis lying within it.
(PICTURE ON GOOGLE DOCS)
What are the boundaries of the abdominal cavity?
- Xiphisternum
- Costal margin
- Iliac crests
- Anterior superior iliac spine (ASIS)
- Pubic tubercle (a point of attachment for inguinal ligament)
- Pubic symphysis (fibrocartilaginous joints connecting the two hip bones anteriorly)
(PICTURE ON GOOGLE DOCS)
Where does the line separating the abdomen into 4 main quadrants lie?
Vertical line- Runs in the midsternal line from the xiphisternum, through the umbilicus, to the pubic symphysis
Horizontal line- Runs across the abdomen through the umbilicus.
Why would you divide the abdomen into 9 regions rather than using the 4 main quadrants?
- This is to be more precise when describing the site of a patient’s pain, or the location of tenderness, mass, swelling, injury, etc during an examination
How are the 9 regions drawn?
- Vertically, from the left and right midclavicular line from the midclaviclular point to the mid-inguinal point
2 horizontal lines - SUBCOSTAL line- horizontal line drawn through the inferior most parts of the right and left costal margin (through the 10th costal cartilage)
- INTERTUBERCULAR line- horizontal line drawn through the tubercles of the right and left iliac crests at the level of L5.
What are the terms of the 9 regions?
- Epigastrium
- Left and right hypochondrium
- Umbilical region
- Left and right lumbar
- Hypogastric/suprapubic region
- Left and right illiac fossa
What is the transpyloric plane?
A horizontal line passing through the tips of the left and right 9th costal cartilage.
It cuts through the pylorus of the stomach, the gallbladder, the pancreas and hila of the kidneys
What is the transumbilical plane?
Unreliable landmark. Its position varies depending on the amount of subcutaneous fat present. In a slender individual it lies at the level of L3.
What is the intercristal plane?
A horizontal line drawn between the highest points of the left and right iliac crests
Where and what is McBurney’s point?
It is the point 2/3 of the way from the umbilicus to the right anterior superior iliac spine.
- It is the surface marking for the base of the appendix
What are the 4 pairs of muscles that comprise the anterolateral abdominal wall and how are their fibres oriented?
- External oblique (diagonally oriented)
- Internal oblique (diagonally oriented)
- Transversus abdominis (horizontal)
- Rectus abdominis (straight)
What are the 3 muscle layers laying laterally to the rectus abdominis and in which direction are their fibres oriented?
- External oblique (Inferomedially)
- Internal oblique (superomedially)
- Transversus abdominis (horizontal)
Describe what the rectus abdominis is (3)
What is it attached to superiorly and inferiorly?
- The left and right rectus abdominis muscles lie on either side of the linea alba, within the rectus sheath
- It is attached to the sternum and costal margin superiorly and to the pubis inferiorly.
- It is comprised of muscle segments interspersed with horizontal tendinous bands
- When the muscles hypertrophy during exercise, they. bulge and can be seen on the abdominal wall as a ‘6-pack’
What arteries supply the anterolateral abdominal wall?
- Musculophrenic artery- a branch of the internal thoracic artery
- Superior epigastric artery- continuation of the internal thoracic artery. It descends into the rectus sheath
- Inferior epigastric artery- a branch of the external iliac artery. It ascends in the rectus sheath and anastomoses with the superior epigastric artery (to supply muscles of the abdominal wall)
These vessels are accompanied by deep veins.
How is the linea alba formed?
- Anteriorly, the 3 layers of muscles become aponeurotic (forming tendons), which fuse with each other at the midline.
- They fuse with aponeuroses from the other side forming a tough midline raph called the linea alba.
Aponeuroses of the muscles also form the rectus sheath enclosing the rectus abdominis.
What forms the anterior and posterior layer of the rectus sheath?
- The anterior layer of the Internal oblique aponeurosis and the external oblique aponeurosis form the anterior wall of the rectus sheath
- The posterior layer of the internal oblique aponeurosis and the transversus abdominis aponeurosis form the posterior wall of the rectus sheath.
What is the inferior part of the external oblique aponeurosis attached to?
- The anterior superior iliac spine – laterally
- The pubic tubercle —medially
- The ASIS and pubic tubercle are connected via the inguinal ligament
What nerves are the muscles and skin of the anterolateral abdominal wall innervated by?
- Thoraco-abdominal nerves T7-T11. Somatic nerves containing sensory and motor fibres.
- Subcostal nerves- originates from T12 spinal nerve.
- Iliohypogastric and ilioinguinal nerves – branches of the L1 spinal nerve.
What are the structures that comprise the foregut?
- Distal oesophagus
- Stomach
- First half (proximal) of the duodenum
- Liver
- Gallbladder
- Bile duct
- Pancreas
- Spleen
What are the structures that comprise the midgut?
- Distal half of the duodenum
- Jejunum
- Ileum
- Caecum
- Appendix
- Ascending colon
- Proximal 2/3 of transverse colon
What are the structures that comprise the hindgut?
- Distal 1/3 of the transverse colon
- Descending colon
- Sigmoid colon
- Rectum
What is the difference between pain and tendinous?
Tenderness is a sign during examination, pain is a symptom patients say they have
Name the organs in the left hypochondriac region
- Stomach
- Pancreas
- Left kidney
- Large intestines
- Spleen
- Liver’s tip
Name the organs in the epigastric region
- Liver
- Stomach
- Pancreas
Name the organs in the right hypochondraic region
- Liver
- Right kidney
- Gallbladder
- Large/small intestines
Name the organs in the left lumbar region
- Descending colon
- Small intestine
- Left kidney
Name the organs in the umbilical region
- Transverse colon
- Duodenum
Name the organs in the right lumbar region
- Right kidney
- Ascending colon
- Small intestine
Name the organs in the left iliac region
- Descending colon
- Sigmoid colon
- Small intestine
Hypogastric region
- Bladder
- Sigmoid colon
- Small intestine
- Rectum
- Reproductive organs
Right iliac region
- Appendix
- Caecum
- Ascending colon
- Small intestine
What is the parietal peritoneum and what type of nerve is the parietal peritoneum innervated by?
Can it be seen with the naked eye?
- It is a layer that lines the abdominal wall
It is innervated by somatic nerves that supply the overlying muscles and skin of the abdominal wall - It can be seen with the naked eye
What is the visceral peritoneum and what type of nerve is it innervated by?
Can it be seen with the naked eye?
- It is a layer that covers the abdominal viscera and it cannot be seen with the naked eye
- It is innervated by visceral sensory nerves which conduct ‘painful’ sensations back to the CNS via sympathetic nerves innervating the organ/structure it covers.
What lies in between the parietal and visceral peritoneum and what is its function?
- The peritoneal cavity
- It contains peritoneal fluid which allows the viscera to slide alongside each other
(the 2 layers of peritoneum are continuous with each other)
What are the 2 terms used to describe abdominal viscera based on the extent that they are covered by the peritoneum?
What is secondarily retroperitoneal?
Intraperitoneal- Almost completely covered by peritoneum e.g. the stomach
Retroperitoneal- Only covered by peritoneum on their anterior surface as they lie posterior to the peritoneum e.g. the pancreas and abdominal aorta
Secondarily retroperitoneal organs are organs that were intraperitoneal in early development but came to be ‘stuck down’ into the posterior abdominal wall
Name some intraperitoneal organs
Stomach, spleen, liver, jejunum, ileum, transverse colon, sigmoid colon, caecum
Name some retroperitoneal organs
abdominal aorta, kidneys, esophagus, pancreas, rectum, parts of the stomach.
What action is responsible for the formation of the lesser sac and retroperitoneal organs?
During development, organs grow, migrate and rotate to their final positions. In doing this, they pull their peritoneal attachments with them. This forms the lesser sac and also pushes the organs onto the posterior abdominal wall (thus being retroperitoneal organs)
What are mesenteries?
What are embedded in the mesenteries?
- Folds of peritoneum that contain fat.
- They suspend the small intestine and parts of the large intestine from the posterior abdominal wall.
- The arteries that supply the intestines from the abdominal aorta and veins of the portal venous system that drain the gut are embedded in the mesenteries.
Describe the greater and lesser omenta
What is embedded within the free edge of the lesser omentum?
- They are folds of peritoneum that are usually fatty.
- They connect the stomach to other organs
- The greater omentum hangs from the greater curvature of the stomach and lies superficial to the small intestine
- The lesser omentum connects the stomach and duodenum to the liver.
- The portal triad is embedded within the free edge of the lesser omentum. (portal triad= hepatic artery, hepatic portal vein and bile duct.
What are ligaments?
What is the falciform ligament
What is the ligament that connects the superior surface of the liver to the diaphragm?
- They are folds of peritoneum that connect organs to each other or to the abdominal wall.
- The falciform ligament connects the anterior surface of the liver to the anterior abdominal wall
- The liver connecting the superior surface of the liver to the diaphragm is the coronary and triangular ligaments
What is the median umbilical fold?
What is the medial umbiilcal fold?
Peritoneal folds are generally difficult to see
- It is a peritoneal fold that lies in the midline and represents the remnant of the urachus–> an embryological structure connecting the bladder to the umbilicus.
- The medial umbilical fold lies lateral to the median umbilical folds. These are the remnants of the paired umbilical arteries returning venous blood to the placenta (in foetal life)
What is the lateral umbilical fold?
It is a peritoneal fold that lies laterally to the medial umbilical folds.
The inferior epigastric arteries lie deep to these peritoneal folds.
What are the 2 regions of the peritoneal cavity and how do they communicate with each other? Where are the 2 regions located?
- The smaller sac (omental bursa)- is a space that lies posterior to the stomach and anterior to the pancreas
- The greater is the remaining part of the peritoneal cavity
- They communicate with each other via the epiploic foramen (lies posterior to the free edge of the lesser omentum)
What does the GI system develop from?
It develops from the embryonic gut tube which lies in the midline of the abdominal cavity, suspended from the posterior abdominal wall by the dorsal mesentery.
What do the major branches of the abdominal aorta supplying the developing gut tube (which becomes the GI system) travel through
The dorsal mesentery
What does the ventral mesentery do?
It connects the stomach to the anterior abdominal wall.
- As the liver grows within it, the anterior part of the ventral mesentery becomes the falciform ligament and the posterior part becomes the lesser omentum.
Where does the oesophagus pass through the diaphragm? At what level is this?
What is the distal oesophagus continuous with?
The oesophagus passes through the oesophageal hiatus in the diaphragm at the level of T10
It is continuous with the cardia of the stomach
What is the term for the muscle around the oesophageal hiatus and what is its function?
The muscle around the hiatus functions as a sphincter that prevents reflux of stomach contents into the oesophagus.
What is the distal oesophagus supplied by and where does blood from the distal oesophagus drain into?
- The distal oesophagus is supplied by branches from the left gastric artery.
- Its venous drainage is via both the systemic system of veins (oesophageal veins that drain into azygous veins) and the portal venous system (via the left gastric veins)
This is the site of portosystemic anastomoses.
What shape is the stomach and can it expand?
- It is J shaped and it can expand to accommodate food and fluid.
What does the stomach break food down into?
The stomach chemically and mechanically breaks down food into chyme.
Describe parts of the stomach
- The cardia (which is continuous with the oesophagus)
- The fundus (most superior part of the stomach and is usually filled with gas)
- The body (largest part of the stomach)
- The pyloric antrum (wide and tapers towards the pyloric canal)
- The pyloric canal (narrow and contains the pyloric sphincter which is a circular smooth muscle that regulates the passage of chyme into the duodenum)
- The lesser and greater curvatures of the stomach