Anatomy of the Abdominal Wall, Inguinal Region & Hernias Flashcards
What are the bony landmarks of the pelvis
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
Describe the skeletal landmarks of the abdomen/thorax
Sternum/Xiphoid process: XP at TIX/X
Costal Cartilage: of the 6th-10th ribs forms the costal margin to which the diaphragm is attached
Which vertebrae are associated with the abdomen and pelvis
Thoracic, lumbar vertebrae, sacrum
Describe the abdominopelvic cavity
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
Why is some of the abdomen protected by the thoracic wall
note that due to the arching of the diaphragm the upper abdomen extends into the thorax and may be protected by the ribcage
Describe the axis of the pelvic cavity
Downwards and backwards
Describe the pelvic inlet
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
What is a consequence of the pelvic cavity being continuous with the abdominal cavity
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
List the visceral structures in the abdomen
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
What do the kidneys, ureter and bladder extend into
The pelvic cavity.
Describe how we can divide the abdomen into 9 regions anteriorly
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
What is sometimes used instead of the subcostal plane
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
What are the 9 regions
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
Where are the inguinal ligaments found
left and right groin
Describe the 4 quadrants of the abdominal wall
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
What structures are present in each quadrant
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
List the structures of the antero-lateral abdominal wall
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
Describe the superficial of the abdominal wall
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
Describe the deeper membranous layer
Scarpa’s fascia- little to no fat
Investing (deep) fascia between the oblique muscles
Summarise the muscles in the abdominal wall
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
Summarise the three flank muscles
The three muscles are separate in the flanks
The three flat muscle fibres continue anteriorly as aponeurotic sheets and contribute to the rectus sheath
What are the functions of the flank muscles
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.
Describe the external oblique muscles
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
Describe the aponeurosis of the external obliques and how this forms the inguinal canal
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.
What does the aponeurosis of the external obliques fuse with medially
the rectus sheath
Describe the internal oblique muscles
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
What are the functions of the internal oblique muscles
Compresses abdominal contents; both muscles flex trunk; each muscle bends trunk and turns anterior part of the trunk to the same side
Describe the transversus abdominis muscles
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
Describe the attachments of the rectus abdominis
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
What is the rectus abdominis intersected by along its course
The muscle is divided into segments by tendinous intersections (3 on each side) which are attached to the anterior wall of the rectus sheath
Describe the formation of the rectus sheath above the umbilicus (upper 3/4s of the rectus)
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.
Describe the formation of the rectus sheath below the umbilicus (lower 1/4 of the rectus)
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)
Summarise the rectus sheath
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.
What are the functions of the rectus abdominis
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
Describe the quadratus lumborum
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.
What are the functions of the quadratus lumborum
stabilises the 12th rib and a lateral flexor of the trunk
Acting together the muscles may extend the lumbar part of the vertebral column.
Describe the psoas major muscle
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.
What is the function of the psoas major
is a flexor of hip and trunk
flexes the trunk against gravity when the body is supine.
Describe the blood supply of the abdominal wall superiorly
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
Describe the blood supply of the abdominal wall deeply
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.
Describe the blood supply of the rectus muscle
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
Describe blood supply of the flank muscles
Intercostal arteries 7-11
Subcostal artery
Lumbar arteries
Deep circumflex iliac arteries
Describe venous drainage
Deep veins bearing the same names accompany the arteries
Describe the innervation of the abdominal wall
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
Describe the innervation of the peritoneum
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
Describe the innervation of the posterior wall of the abdomen
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
Describe the lumbar plexus
Lumbar plexus (L1 - L4) Motor and sensory, mainly for the lower limb. Sensory branches to the parietal peritoneum of the posterior abdominal wall
Describe the dermatomes of the abdominal wall
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.
Describe the course of T12 (subcostal) and branches of L1
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
Describe the course of the intercostal nerves T7-T11
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.
Are there any lymph nodes on the abdominal wall
NO
Describe the lymphatics of the superficial tissues
Superior to the umbilicus: drains to pectoral group of axillary nodes
Inferior to the umbilicus: drains to superficial inguinal nodes
Describe the lymphatic drainage of the deep tissues
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
Describe the transversalis fascia
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.
What happens after the transversalis fascia attaches to the crest of the ilium
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
What is meant by an aponeurosis
flat tendon of muscle
Describe the conjoint tendon
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.
