Gastrointestinal Tract

Question 1

What are the layers that we encounter as you go down the skin through the anterior abdominal wall?

Answer 1

Skin, superficial fascia, the three abdominal muscles (external, internal and transversalus) then the transversalis fascia, extraperitoneal fascia and finally the parietal peritoneum.

Question 2

What is the body framework of the abdomen? Where are the borders and where do muscles attach to?

Answer 2

Costal margin at the superior end, iliac crest with the ASAS (anterior superiorly), pubic tubercle (lump of bond at the lateral end of the pubic crest) and pubic crest.

The outermost layer of muscles will overly the anterior costal margin area.

The middle layer of muscles will attach directly to the edge of the costal margin.

The most posterior layer will have to attach behind the costal margin. It will also be in the same plane as the diaphragm.

Question 3

What happens to the three layers of abdominal muscles as it moves medially towards the mid line?

Answer 3

It is fleshy laterally and becomes aponeurotic medially. Until it meets at the midline forming the linea alba.

Question 4

Where are the external oblique muscles found, direction of fibres, origin and attachments and how it folds at the lower end of attachment?

Answer 4

This is the outermost layer of muscle with front pocket directions. The origin and attachment is found on to be overlying on the thoracic cage and it moves up towards the serratus anterior and pectoralis major. The EO will attach to the anterior half of the iliac crest as it moves down, once it gets to the ASAS it will jump and attach to the pubic crest. Also forms aponeuroses as it moves medially to the mid line.

This forms a free inferior margin.

Question 5

What is the inguinal ligament?

Answer 5

The free inferior margin of the external oblique is thickened a lot and folds onto itself.

Question 6

Where are the internal oblique muscles found, direction of fibres, origin and attachments and how it folds at the lower end of attachment?

Answer 6

It attaches directly to the superior aspect of the costal margin and meets back in the mid line linea alba and posteriorly as far back as the thoracolumbar fascia. The muscle will then attach to the ASAS. From there the lower most fibres of the internal oblique muscles originate from the lateral 2/3 of the inguinal ligament. The fibres at the lower end are arching upper then lower down to attach to the pubic crest.

It is back pocket direct of muscle fibres.

Question 7

Where are the transversus abdominus found, direction of fibres, origin and attachments and how it folds at the lower end of attachment?

Answer 7

This is the deepest layer that underlies the posterior end of the costal margin in the same plane as the diaphragm. It will continue as far posteriorly as the thoracolumbar fascia and meet in mid line. The lower most fibres originate from the lateral 1/3 of the inguinal ligament then arches to be inserted into the pubic crest too.

Question 8

What happens at the pubic crest when both the internal oblique and transversus abdominus attach to the pubic crest?

Answer 8

This forms a conjoined tendon with the two fibres fusing.

Question 9

Where are the rectus abdominus found, direction of fibres, origin and attachments and how it folds at the lower end of attachment?

Answer 9

This is found in the midline and arises inferiorly from the pubic crest. The muscle ascends up the midline while diverging. It will cross pass the costal margin (5,6,7) and attach right under the pectoralis major.

Tendinous inscriptions are disruptions found along the rectus abdominus to make the muscle fibres shorter and therefore stronger.

Question 10

What is the rectus sheath and what forms it?

Answer 10

The rectus sheath is made up of the three different aponeuroses from the three different abdominal muscles. The sheath encloses the rectus abdominus. Some areas there is also the presence of a posterior sheath behind the rectus abdominus.

Question 11

What is the arcuate line in the anterior abdominal wall?

Answer 11

The arcuate line is where the aponeuroses end and arches for the posterior.

Question 12

How is the rectus sheath organised around the rectus abdominus with respect to the upper and lower portions?

Answer 12

The upper rectus sheath will have the aponeuroses split evenly about 1.5 each around the rectus abdominus. Whereas lower down on the sheath (one inch below the umbilicus it is positioned completely in front of the rectus abdominis.

• The rectus abdominis sits directly on top of the transversalis fascia.

Question 13

What is the neurovascular supply to the anterior abdomen like?

Answer 13

It is in the same plane as the thoracic neurovascular supplies. The supplies are found between the internal oblique and the transversalis abdominis. There will be segmental innervation of the anterior abdominal wall from T10 (umbulicus) to L1 (groin)

Question 14

Where does the main arterial supply come from for the anterior abdomen wall?

Answer 14

The main supplies are the superior epigastric and the inferior epigastric that run in the rectus sheath (posterior part of the sheath).

Internal thoracic artery branches out to superior epigrastic. Inferior epigastric is a branch of the external iliac artery.

Question 15

What is the venous system like in the abdomen wall?

Answer 15

There is a dual venous drainage system, the portal venous drainage and the systemic venous drainage.

Question 16

What is the pectineal ligament?

Answer 16

This is a ligament that lines the pubic bone and marks the pelvic inlet.

Question 17

What is the lacunar ligament?

Answer 17

This is a crescentic extenion between the inguinal and pectineal ligament that forms.

Question 18

Where are the testes developed in and where must they move to?

Answer 18

Testes develop in the posterior abdominal wall in the extraperitoneal fat. They need to descend into the scrotum.

That is a move from extraperitoneal fat, transversalis fascia, transversus abdominus, internal and external oblique muscles efore you get to the superficial fascia on the skin.

Question 19

What is the pathway of the testes to the scrotum like?

Answer 19

The hole created by the testes in the fascia transversalis is found half way between the ASAS and the pubic tubercle about a finger’s breadth above the linguinal ligament. This is called the deep inguinal ring.

There are arching borders from the TA and IOM (internal oblique muscles) that coem from the lateral ends of the inguinal ligaments forming space. The testes will turn medially with the arching roof formed from the fibres forming the conjoined tendons. This is called the inguinal canal.

There is a triangular hole at the end of the external oblique called the superficial inguinal rings.

Question 20

What are the features of the inguinal canal?

Answer 20

Question 21

How is the spermatic cord formed by having addition layers added to the testes?

Answer 21

Spermatic cord is made up of all the following as it passes through the layers. The first layer is picked up from when it passes the transversalis fascia.

The second to be picked up is the cremasteric fascia (responsible for testicular contraction because of some muscle there). This is coated as it passes the inguinal canal and particularly by the internal oblique muscle.

The external spermatic fascia is obtained by passes through the external oblique.

At this point you can technically call it the spermatic cord.

Question 22

When is an abdominal hernia?

Answer 22

This is when abdominal content protrudes through an abdominal wall because of the increase pressure in the abdomen and pushes on weakened areas.

Question 23

What is the bilateral indirect inguinal hernia?

Answer 23

This is a protrusion through the deep ring into the inguinal canal then follows the same path as the testes.

The indirect hernia arises from incomplete closure of the processus vaginalis, hence the herniated peritoneal contents extend into the scrotum (or labia).

Question 24

What is bilateral direct inguinal hernia?

Answer 24

A protrusion forwards into the inguinal canal through an area of weakness in its posterior wall.

The inguinal triangle is particularly weak area in the anterior wall.

Question 25

What is the bony framework of the posterior wall of the abdomen?

Answer 25

It is made up of the five lumbar vertebra that project into the abdominal cavity and forms the para-vertebral gutters. The gutters sit on either side to the vertebra. The gutters are floored by a strong muscle.

Question 26

What is the psoas major muscle, where is it found, origin and attachments, functions?

Answer 26

Psoas major is found adjacent to the vertebral column and in 2/3 cases it will have psoas minor overlying it. It lies in the paravertebral gutter adjacent to the lumbar vertebral body and between the transverse processes. Lateral border of psoas is straight but oblique that can be used as a reference point. It is an important flexor of the vertebra and maintaining an erect spine. For a strong attachment it attaches to the vertebral body, discs and medial ends of the transverse processes along the T12 and L5.

It then attaches to the lesser trochanter of femur by converging below the inguinal ligament.

Lumbar plexus is found within the lumbar, sympathetic trunk is found in front of psoas and the lumbar vessels are found behind the psoas.

Question 27

What is the psoas minormuscle, where is it found, origin and attachments, functions?

Answer 27

It is present in 2/3 of people and has no functional role.

Question 28

What is the quadratus lumborum muscle, where is it found, origin and attachments, functions?

Answer 28

This is found superior laterally of the psoas major. It attaches to the 12th rib above and at the tips of the lumber transverse processes and then to the posterior half of the iliac crest.

Question 29

What is the iliacus muscle, where is it found, origin and attachments, functions?

Answer 29

The iliacus is found inferior laterally from the psoas major. It is an inverted triangle in shape. It originates from the iliac fossa and it is edge to edge with psoas. It also converges and heads towards the lesser trochanter by going beneat the inguinal ligament.

Question 30

What is the thoracolumbar fascia? What does it enclose? What structures does it not provide points of attachments for?

Answer 30

There are three layers of tought fibre tissues. One layer attaches to the tip of the spinous process and forms the posterior layer. The middle layer is attached to the tip of the transverse processes. The most anterior layer attaches to the front of the transverse processes. Eventually they will all focus to the tip of the 12th rib.

The posterior compartment encloses the erector spinae muscle. The anterior compartment encloses the quadratus lumborum muscle.

Psoas and iliac muscles have their own psoas and iliac fascia.

Fascia fusion at the T12 gives attachment points to the anterior abdominal muscles except for the external abdominal oblique muscles. This means that external abdominal has both inferior and posterior free borders.

Question 31

What muscle floors the para vertebral gutters?

Answer 31

Quadratus Lumborum.

Question 32

What is the peritoneal?

Answer 32

This is similar to the pleura with a parietal and visceral peritoneum lining different parts of the body.

Question 33

What is a mesentery?

Answer 33

This is a structure with a dobule fold of the peritoneal.

Question 34

What is the retroperitoneum space?

Answer 34

This is the space outside of the pleura and within the cavity.

Question 35

Where are the kidneys located in the abdominal cavity?

Answer 35

It is found lateral to the vertebral column and in the para-vertebral gutters. The right kidney sites slightly lower than the left. Positioned at T12 and L3. But kidneys move during inspiration so static position is not important. The kidney is found in front of the posterior wall of the 12th rib. Located in front of the quadratus lumborum.

Question 36

What is the lumbar and lateral approaches to surgery on the kidney?

Answer 36

Since it is located posteriorly and outside the peritoneum it is preferred to be accessed from the posterior and lateral ends. Will require to remove the 12th rib for larger surgery window as well. There is no need to pass through all the other layers to reach the kidneys if we approached from the anterior.

Question 37

How big are the kidney and what is located superior of it and what is its shape?

Answer 37

Kidneys are 10cm long, 5cm wide and 2.5 cm thick.

Superiorly is the adrenal glands. The right side looks like a party hat supra-adrenal gland. The left sound is more like a crescent shaped adrenal gland.

Question 38

What are the structures found on the anterior surface of the kidneys?

Answer 38

Kidneys are a solid visceral organ so that it will contain collections of clusters of secretory cells. These are typically enveloped by a capsule (fibrous capsule). It is often surrounded by fat (peri-renal fat) that is then enclosed by the renal fascia.

Question 39

What are the structures found within the kidneys like?

Answer 39

Secretory cells are arranged into a lighter continuous outer cortex. The triangular discontinuous and darker areas are the medulla. All the apex points towards the hilum of the kidney.

The renal sinus is full of fat and where the vein, artery and ureteric vessels are embedded.

The medulla drains into 2-3 minor calyces that drain into one major calyces. Then 2-3 major calyces will drain into the renal pelvis and leave through the ureter.

Question 40

What direction does the kidney hilum face?

Answer 40

The hilum faces anteriorly and medially while transmitting the vein, artery and ureteric duct.

Question 41

What is the blood supply of the kidneys like?

Answer 41

The main renal artery is a branch off the abdominal aorta. Once at the kidney it will segment into five different segmental arteries that supply segments of the kidney independently.

Question 42

What is the developmental history of kidney blood supply and why we may see two renal blood supplies sometimes?

Answer 42

Kidneys develop lower down on the posterior wall. it changes its position during development because of differential growth rates. As it moves up it will lose blood supply from the lower portions then eventually gain an upper blood supply. Therefore we may see accessory renal artery that is the persistence of early renal blood supplies (25% - important in surgery).

Question 43

What is the venous system of the kidney like?

Answer 43

There are multiple veins that will unite at the sinus forming the right and left renal vein. The right renal vein goes directly into the IVC. But the left renal vein has to across the FRONT of the abdominal aorta to enter the left hand side of the IVC.

Question 44

What is the pathway of the ureter down towards the bladder?

Answer 44

The ureter is 25-30cm long and descends along the posterior abdominal wall structures. The ureters descend along on psoas major. Vertically it corresponds to the tip of the lumbar transverse processes (could be used as location reference in radiology).

Ureters take blood supply from whatever they are passing.

Question 45

What are the rules for narrowing of a muscular tube?

Answer 45

there will be narrowing at the beginning and end of the tube. Any other narrowing in the middle is due to impingement from external structures.

Question 46

How does the ureter enter the bladder and what is the significance of this?

Answer 46

The ureter will enter the bladder diagonally so that during urination the bladder will contract and narrow off the ureter. This will prevent backflow and acts a physiolocal sphincter.

Question 47

Where is the fourth narrowing on the ureter found?

Answer 47

It is found as the ureter passes and kinks over the pelvin brim.