Anatomy of the Abdominal Wall, Inguinal Region & Hernias

Question 1

What are the bony landmarks of the pelvis

Answer 1

Iliac Crest: most superior border of the ilium
Iliac Fossa: internal face of the ilium
Anterior Superior Iliac Spine: protrusion at the most anterior part of the iliac crest
Pubic Symphysis: cartilage where the pubic tubercles are joined
Pelvic Inlet: enclosed laterally by the pelvic brim, anteriorly by the pubic tubercles and posteriorly by the sacrum

Question 2

Describe the skeletal landmarks of the abdomen/thorax

Answer 2

Sternum/Xiphoid process: XP at TIX/X

Costal Cartilage: of the 6th-10th ribs forms the costal margin to which the diaphragm is attached

Question 3

Which vertebrae are associated with the abdomen and pelvis

Answer 3

Thoracic, lumbar vertebrae, sacrum

Question 4

Describe the abdominopelvic cavity

Answer 4

Abdominal and pelvic cavities are continuous

Diaphragm separates the thoracic and abdominal cavities.

Upper part of the abdominal cavity extends beneath the thoracic cage

Pelvic inlet (pelvic brim) arbitrarily separates the abdominal from the pelvic cavity

Question 5

Why is some of the abdomen protected by the thoracic wall

Answer 5

note that due to the arching of the diaphragm the upper abdomen extends into the thorax and may be protected by the ribcage

Question 6

Describe the axis of the pelvic cavity

Answer 6

Downwards and backwards

Question 7

Describe the pelvic inlet

Answer 7

The circular margin of the pelvic inlet is formed posteriorly by the sacrum, anteriorly by the pubic symphysis and laterally by the distinct bony rim of pelvic bone

Question 8

What is a consequence of the pelvic cavity being continuous with the abdominal cavity

Answer 8

The peritoneum lining the abdominal cavity is continuous with that of the pelvic cavity- infections in one region can freely spread to the other
Bladder expands superiorly from the pelvic cavity into the abdominal cavity
During pregnancy, uterus expands superiorly into the abdominal cavity

Question 9

List the visceral structures in the abdomen

Answer 9

Stomach, duodenum, small and large intestines

Liver, pancreas & spleen

Kidneys, ureters and urinary bladder

Reproductive organs

Abdominal vessels

Spleen in a lymphatic organ
Structures belonging to G.I system, urinary system and reproductive system

Question 10

What do the kidneys, ureter and bladder extend into

Answer 10

The pelvic cavity.

Question 11

Describe how we can divide the abdomen into 9 regions anteriorly

Answer 11

Superior horizontal plane is the subcostal plane (lower border of the costal cartilage of rib 10, passing posteriorly through L3)

Inferior horizontal plane is the intertubercular plane ( connects the tubercules of the iliac crests which are palpable, passes through the upper part of L5)

The vertical lines are the mid clavicular lines

Question 12

What is sometimes used instead of the subcostal plane

Answer 12

The transpyloric plane
Found halfway between jugular notch and the symphysis pubis or halfway between the umbilicus and the inferior end of the body of the sternum
Passes posteriorly through the body of L1
Intersects with the costal margin at the ends of the 9th costal cartillage

Question 13

What are the 9 regions

Answer 13

Superiorly: right hypochondrium, epigastric region (referred pain from foregut), left hypochondrium
Inferiorly: Right flank/lumbar, umbilical (referred pain from foregut), left flank/lumbar
Inferiorly again: right groin, hypogastric/suprapubic region (referred pain from foregut), left iliac region

Question 14

Where are the inguinal ligaments found

Answer 14

left and right groin

Question 15

Describe the 4 quadrants of the abdominal wall

Answer 15

Horizontal umbilical plane passing through the umbilicus and the intervertebral disc between vertebrae L3 and L4 and intersecting with the vertical median plane divides the abdomen into 4 quadrants:

Right upper, left upper, right lower and left lower

Question 16

What structures are present in each quadrant

Answer 16

Right Upper Quadrant
Liver and gallbladder

Left Upper Quadrant
Stomach and spleen

Right Lower Quadrant
Cecum and appendix

Left Lower Quadrant
Sigmoid colon and descending colon

Question 17

List the structures of the antero-lateral abdominal wall

Answer 17

Several surface features

Costal margin, xiphoid
process, iliac crest, ASIS, pubic symphysis and tubercle

Umbilicus, epigastric fossa,

Rectus abdominis, linea alba, linea semilunaris

Abdominal wall muscle sheets

Question 18

Describe the superficial of the abdominal wall

Answer 18

Layer of fatty connective tissue- single layer and is continuous with the superficial fascia throughout other regions
Below the umbilicus- if forms two layers: as superficial and deeper and membranous layer

Superficial fatty layer (Camper’s Fascia) is continuous over the inguinal ligament

Question 19

Describe the deeper membranous layer

Answer 19

Scarpa’s fascia- little to no fat

Investing (deep) fascia between the oblique muscles

Question 20

Summarise the muscles in the abdominal wall

Answer 20

Anterior wall
Paired vertical rectus abdominis muscles within rectus sheath

Lateral wall - 3 flat sheet muscles
External oblique
Internal oblique
Transversus abdominis

Posterior wall
Post vertebral muscles –erector spinae group
Psoas, quadratus lumborum and iliacus muscles

Question 21

Summarise the three flank muscles

Answer 21

The three muscles are separate in the flanks

The three flat muscle fibres continue anteriorly as aponeurotic sheets and contribute to the rectus sheath

Question 22

What are the functions of the flank muscles

Answer 22

Compress the abdomen and increase the intra-abdominal pressure to aid forced expiration, and evacuation of urine, faeces, parturition, heavy lifting
Supports viscera – “guarding” mainly the intestines
Flex and rotate the trunk

Protects the viscera from injury and helps maintain the position of the viscera in the erect posture against the action of gravity.

Contraction of these muscles in forced and quiet expiration pushes the viscera upwards and helps push the relaxed diaphragm further upwards- also plays a role in coughing and vomiting.

Question 23

Describe the external oblique muscles

Answer 23

Attached to the outer surfaces of the lower eight ribs- no posterior border but attached to connective tissue- so you cannot put your hand up it.

Fans out to attach to xiphoid process, linea alba, pubic crest & tubercle, anterior half of iliac crest.- inserted onto the lateral lip of iliac crest; aponeurosis ending in midline raphe

Function: compresses abdominal contents, both flex trunk, each muscle bends trunk to same side, turning anterior part of abdomen to the opposite side

Muscle fibres are directed down ward and forward

Question 24

Describe the aponeurosis of the external obliques and how this forms the inguinal canal

Answer 24

Its large aponeurotic component covers the anterior component of the abdominal wall to the midline (linea alba)- where the aponeuroses are entwined and extends from the xiphoid process to the pubic symphysis

Lower border of the aponeurosis forms the inguinal ligament on each side- this thickened reinforced edge of aponeurosis passes between the ASIS laterally and the pubic tubercule medially

Folds under itself to form a trough- playing an important role in the formation of the inguinal canal.

Question 25

What does the aponeurosis of the external obliques fuse with medially

Answer 25

the rectus sheath

Question 26

Describe the internal oblique muscles

Answer 26

Lateral: Thoracolumbar fascia Iliac crest - anterior 2/3rd (between origins of other two obliques) Inguinal ligament - lateral half ``` Medial: Lower 3 ribs and costal cartilages Xiphoid process, Rectus sheath, Conjoint tendon ``` Aponeurosis ends in linea alba, pubic crest and pectineal line Muscle fibres are directed downward and backward

Question 27

What are the functions of the internal oblique muscles

Answer 27

Compresses abdominal contents; both muscles flex trunk; each muscle bends trunk and turns anterior part of the trunk to the same side

Question 28

Describe the transversus abdominis muscles

Answer 28

``` Lateral: Lower 6 costal cartilages Thoracolumbar fascia Iliac crest – anterior 2/3rd Inguinal ligament –lateral 1/3rd ``` ``` Medial: Xiphoid process Linea alba (rectus sheath) Symphysis pubis Conjoint tendon ``` Aponeurosis ends in linea alba; pubic crest and pectineal line Muscle fibres are directed horizontally The neurovascular plane lies between the internal oblique and transversus abdominis muscle layers Function: compresses abdominal contents

Question 29

Describe the attachments of the rectus abdominis

Answer 29

Superior attachment 5-7 costal cartilages Xiphoid process Inferior attachment Symphysis pubis Pubic crest Pubic tubercle Widens and thins as it ascends- two heads as it is a paired long, flat muscle of the anterior abdominal wall, separated in the midline by the line alba

Question 30

What is the rectus abdominis intersected by along its course

Answer 30

The muscle is divided into segments by tendinous intersections (3 on each side) which are attached to the anterior wall of the rectus sheath

Question 31

Describe the formation of the rectus sheath above the umbilicus (upper 3/4s of the rectus)

Answer 31

Anterior wall- consists of the aponeurosis of the external oblique and half of the aponeurosis of the internal oblique, which splits lateral to the rectus abdominis. Posterior wall- consists of the other half of the aponeurosis of the internal oblique and the aponeurosis of the transversus abdominis.

Question 32

Describe the formation of the rectus sheath below the umbilicus (lower 1/4 of the rectus)

Answer 32

Midway between the umbilicus and pubic symphysis- the beginning of the lower rectus starts All of the aponeuroses move anterior to the rectus No posterior rectus sheath From this point inferiorly, the rectus abdominis is in direct contact with the transversalis fascia Marking this point is an arch of fibres (arcuate line)

Question 33

Summarise the rectus sheath

Answer 33

Rectus sheath is formed by the aponeuroses of external & internal obliques, and transversus abdominis muscles. Rectus sheaths meet in the midline - linea alba The anterior wall of the sheath is complete from the xiphoid process and costal cartilages to pubic symphysis and crest. Posterior wall of the sheath is incomplete, stops short below the umbilicus at the arcuate line. Below arcuate line, the rectus abdominis muscle is in contact with the transversalis fascia.

Question 34

What are the functions of the rectus abdominis

Answer 34

Rectus abdominis is the most powerful flexor of the vertebral column (lower thoracic & lumbar) External and internal obliques of both sides are important partners in this action. Tenses abdominal wall and compresses contents

Question 35

Describe the quadratus lumborum

Answer 35

Arises from transverse process of LV, iliolumbar ligament and adjacent iliac crest The muscle attaches superiorly to the transverse processes of L1-L5 and the inferior border of rib 12 Overlapped medially by the psoas major muscles; along their lateral borders are the transversus abdominis muscles.

Question 36

What are the functions of the quadratus lumborum

Answer 36

stabilises the 12th rib and a lateral flexor of the trunk Acting together the muscles may extend the lumbar part of the vertebral column.

Question 37

Describe the psoas major muscle

Answer 37

Arises from the lateral surface of bodies T12 and L1-5, transverse processes of L1-L5, and the intervertebral discs between T12 and L1-L5 passing inferiorly along the pelvic brim, each muscle continues into the anterior thigh, under the inguinal ligament to attach to the lesser trochanter of the femur.

Question 38

What is the function of the psoas major

Answer 38

is a flexor of hip and trunk | flexes the trunk against gravity when the body is supine.

Question 39

Describe the blood supply of the abdominal wall superiorly

Answer 39

Superior part: branches of the musculophrenic artery- terminal branch of the internal thoracic artery Inferior part: medially placed superficial epigastric artery and the laterally placed superficial circumflex iliac artery, both branches of the femoral artery

Question 40

Describe the blood supply of the abdominal wall deeply

Answer 40

Superior part- superior epigastric- terminal branch of internal thoracic artery Lateral- 10th and 11th intercostal arteries and subcostal arteries Inferior- medially placed inferior epigastric artery and the laterally placed deep circumflex iliac artery, both branches of the external iliac artery.

Question 41

Describe the blood supply of the rectus muscle

Answer 41

Superior epigastric artery- terminal branch of internal thoracic Inferior epigastric artery- branch of external iliac These two vessels enters the rectus sheath and anastomose forming a potential by-pass to abdominal aorta. Found posterior to the muscle throughout their course- It is between internal oblique and transversus abdominis muscles in the neurovascular plane

Question 42

Describe blood supply of the flank muscles

Answer 42

Intercostal arteries 7-11 Subcostal artery Lumbar arteries Deep circumflex iliac arteries

Question 43

Describe venous drainage

Answer 43

Deep veins bearing the same names accompany the arteries

Question 44

Describe the innervation of the abdominal wall

Answer 44

External oblique: anterior rami of lower six spinal nerves Internal oblique: anterior rami of lower six spinal nerves and L1 Transversus: same as internal Rectus: same as external

Question 45

Describe the innervation of the peritoneum

Answer 45

Parietal peritoneum: Same segmental (T7-L1) nerves of the body wall provide somatic sensory supply to the underlying parietal peritoneum. Visceral peritoneum has NO somatic sensory innervation

Question 46

Describe the innervation of the posterior wall of the abdomen

Answer 46

Subcostal nerve (T12), ilio hypogastric & ilioinguinal nerves (L1) supply the antero-lateral abdominal wall Motor supply to: Quadratus lumborum- T12 & L1-L4 (anterior rami) Psoas major- L2-L4 (anterior rami) Iliacus – femoral n. L2–L4

Question 47

Describe the lumbar plexus

Answer 47

``` Lumbar plexus (L1 - L4) Motor and sensory, mainly for the lower limb. Sensory branches to the parietal peritoneum of the posterior abdominal wall ```

Question 48

Describe the dermatomes of the abdominal wall

Answer 48

t7-t9- xiphoid process to just above the umbilicus (epigastrium) T10 - skin around umbilicus T11-L1 - umbilicus to and including the pubic region- includes inguinal ligament ilio-inguinal nerve (branch of L1)- supplies the anterior surface of the scrotum or labia majora and sends a small cutaneous branch to the thigh.

Question 49

Describe the course of T12 (subcostal) and branches of L1

Answer 49

Spinal nerve T12 follows a similar course t the intercostals. Branches of L1 (the ilio-hypogastric nerve and ilio-inguinal nerve), which originates from the lumbar plexus, follow similar courses initially ( superior to inferior respectively), but deviate near their final destination

Question 50

Describe the course of the intercostal nerves T7-T11

Answer 50

Leave their intercostal spaces, passing deep to the costal cartilage, and continue onto the anterolateral abdominal wall between the internal oblique and transversus (neurovascular plane) The reach the lateral edge of the rectus sheath and pass posterior to the lateral aspect of the rectus abdominis muscle. Approaching the midline, an anterior cutaneous branch passes through the rectus abdominis muscle and the anterior wall of the rectus sheath to supply the skin.

Question 51

Are there any lymph nodes on the abdominal wall

Answer 51

NO

Question 52

Describe the lymphatics of the superficial tissues

Answer 52

Superior to the umbilicus: drains to pectoral group of axillary nodes Inferior to the umbilicus: drains to superficial inguinal nodes

Question 53

Describe the lymphatic drainage of the deep tissues

Answer 53

lymphatics accompany deep veins in the extraperitoneal tissues Superior to the umbilicus: drains to mediastinal nodes Inferior to the umbilicus: drains to external iliac/para-aortic nodes

Question 54

Describe the transversalis fascia

Answer 54

Continuous layer of deep fascia that lines the abdominal cavity and continues into the pelvic cavity. It crosses the midline anteriorly, associating with the transversalis fascia of the opposite side, and is also continuous with the fascia on the inferior side of the diaphragm It continues posteriorly with the deep fascia covering the muscles of the posterior abdominal wall and attaches to the thoracolumbar fascia.

Question 55

What happens after the transversalis fascia attaches to the crest of the ilium

Answer 55

The transversalis fascia blends with the fascia covering the muscles associated with the upper regions of the pelvic bones and with similar fascia covering the muscles of the pelvic cavity At this point it is referred to as the parietal pelvic (or endo-pelvic fascia) there is therefore a continuous layer of deep fascia that is thick in some areas and thin in others, attached or free and participates in the formation of specialised structures

Question 56

What is meant by an aponeurosis

Answer 56

flat tendon of muscle

Question 57

Describe the conjoint tendon

Answer 57

The conjoint tendon (previously known as the inguinal aponeurotic falx) is a structure formed from the lower part of the common aponeurosis of the internal oblique muscle and the transversus abdominis as it inserts into the crest of the pubis and pectineal line immediately behind the superficial inguinal ring. It is usually conjoint with the tendon of the internal oblique muscle, but they may be separate as well. It forms the medial part of the posterior wall of the inguinal canal.