Abdominal wall, the inguinal canal and hernias Flashcards
What are the two upper horizontal planes for dividing the abdomen?
Transpyloric plane (midway between the jugular notch of the sternum and the pubic symphysis, approximately crossing the L1 vertebra)
Subcostal plane (inferior to 10th costal cartilage, approx L3) are used.
What is the lower horizontal plane for dividing the abdomen?
Transtubercular plane (passing through the tubercles of the iliac crests and the L5 vertebrae)
What defines the left and right vertical planes for dividing the abdomen?
Midclavicular lines (mid-clavicle to midway between ASIS and pubic tubercle)
What are the nine regions of the abdomen?
Hypochondrium: left and right top corners
Epigastric: top centre
Lumbar: left and right middle
Umbilical: middle centre.
Iliac/inguinal: left and right bottom
Pubic/hypogastric: middle bottom
What is the orientation and attachments of the external oblique?
Oriented forwards and downwards - inferomedial
Superiorly: attached to ribs 5-12
Some fibres pass inferiorly to the iliac crest
Some are attached to an aponeurosis - anterior to rectus abdominis, inserting on the midline linea alba.
The inferior border of the aponeurosis of the muscle forms the inguinal ligament.
What innervates the external oblique?
T6/7-T12 thoracic segmental nerves.
What role does the external oblique have?
It increases intra-abdominal pressure and laterally flexes /rotates the trunk.
What is the orientation and attachments of the internal oblique?
Orientation forwards and upwards (superomedial)
Internal oblique arises from the lumbar fascia, the iliac crest and the lateral two thirds or so of the inguinal ligament.
It attaches to the lower three or four ribs (10-12), the linea alba.
It forms the sheath of rectus abdominis (wraps around)
In the inferior part of the abdomen, the internal oblique fibres arch medially from the inguinal ligament and attach to the pubis as part of the conjoint tendon .
What innervates the internal oblique?
T7-T12 thoracic segmental nerves and to some extent the iliohypogastric and ilioinguinal (L1) nerves
What role does the internal oblique have?
It increases intra-abdominal pressure and rotates / laterally flexes the trunk.
What is the orientation and attatchments of the transversus abdominis?
Horizontal orientation run transversely
The fibres arise from the lower six costal cartilages (7-12), the lumbar fascia, the iliac crest and lateral part of the inguinal ligament and to the anterior aponeurosis.
In the superior part of the abdomen, its aponeurosis passes posterior to rectus abdominis to attach to the linea alba.
Inferiorly ,the transversus abdominis aponeurosis lies anterior to rectus abdominis, where it is joined by internal oblique to insert upon the pubis as the conjoint tendon.
What innervates the transersus abdominis?
T8-T12 thoracic segmental nerves and the iliohypogastric and ilioinguinal (L1) nerves
What role does the transversus abdominis have?
It increases intra-abdominal pressure and supports the abdominal viscera
What is the orientation and attatchments of the rectus abdominis?
Long muscles separated by the tendinous linea alba,
The fibres of rectus abdominus are interrupted by three transverse tendinous intersections giving the muscle the so-called ‘six-pack’ appearance.
Attached to the pubic symphysis and pubic crest inferiorly and the xiphisternum and 5 th to 7 th costal cartilages superiorly.
Surrounded by the rectus sheath
The superior ¾ of the muscle is completely enveloped within the rectus sheath, the point at which the rectus sheath becomes deficient posteriorly is called the arcuate line.
What innervates the rectus abdominis?
Innervated by the T7-T12 thoracic segmental nerves
What role does the rectus abdominis have?
It increases intra-abdominal pressure and flexes the trunk.
What is the arcuate line?
The point at which the rectus sheath becomes deficient posteriorly
What arterial supply do the abdominal muscles have?
Anterior: Segmental superior epigastric arteries
‘continuation’ of the segmental ‘thoracic’ ‘intercostal’ supply
Posterior: Segmental from aorta
What musculature does the posterior abdominal wall have?
Square muscle attached to the 12th rib superiorly and the iliac crest inferiorly, called quadratus lumborum, which lies lateral to the psoas major muscle.
What depth do nerves tend to lie supplying the abdominal wall?
In the neurovascular plane between the transversus abdominus and internal oblique muscles, perforating these layers as necessary to innervate more superficial structures.
What are the layers of the abdominal wall from superficial to deep?
Skin
Superficial fascia (subcutaneous tissue, which divides into a superficial fatty layer (Camper’s fascia) and a deeper, more membranous layer (Scarpa’s fascia)
Investing fascia which is directly adherent to the muscles of the wall
Three layers of abdominal muscles laterally ( external oblique, internal oblique and transversus abdominus) and a single sheet of muscle medially (rectus abdominis)
A deeper layer of fascia lining the muscles (transversalis fascia)
The parietal peritoneum.
Where does the inguinal canal lie in relation to the medial inguinal ligament?
Superior
What is the initial out pouching of peritoneum called in testicle descent?
Processus vaginalis
Normally what happens to the processus vaginalis before birth?
Obliterates, leaving the tunica vaginalis
What does a persistent processus vaginalis result in?
Provides a path for abdominal contents to pass into the scrotum, forming an indirect inguinal hernia.
What is the inguinal canal and what marks it?
A passage between the anterior abdominal muscles, essentially a tunnel with two openings; the deep and superficial inguinal rings
What passes through the inguinal canal in males and females?
Spermatic cord (males) or round ligament of the uterus (females) and ilioinguinal nerve
Does the ilioinguinal nerve pass through both the deep and superficial rings, why?
Does not enter the canal through the deep ring, but passes through internal oblique muscle and out of the superficial ring.
The nerve lies between the transversus abdominus and the internal oblique
What forms the roof, anterior wall, posterior wall and floor of the canal?
Roof of canal is formed by arching fibres of the internal oblique and transversus abdominus
Anterior wall formed by external oblique apopneurosis
Posterior wall by the transversalis fascia and medially the conjoint tendon
Floor formed by infolding of inguinal ligament
Where does the deep inguinal ring lie?
Midpoint of the inguinal ligament (mid-way between the anterior superior iliac spine (ASIS) and the pubic TUBERCLE)
If pubic symphysis then this is the mid-inguinal point (different)
Where does the superficial ring lie?
Position inferred by Hesselbach’s triangle
What is an inguinal hernia?
Protrusion of tissue from within the peritoneal cavity through the abdominal wall, which is associated with the inguinal canal. Hernia contents may include fat, mesentery and bowel
What is an indirect inguinal hernia?
Traverse the inguinal canal, pass through the deep inguinal ring and along the inguinal canal.
Congenital, their existence dependent on a patent processus vaginalis
May reach the scrotum or labia majora.
What is a direct inguinal hernia?
Develop due to a weakness in the conjoint tendon area within Hesselbach’s triangle
Bulge directly through the posterior wall of the canal from behind the superficial inguinal ring.
They pass through the region of Hesselbach’s triangle.
What are the borders of Hesselbach’s triangle?
Rectus abdominis medially
The inferior epigastric vessels superiorly
Inguinal ligament inferiorly.
5 muscles which contribute to posterior abdominal wall
Psoas major Psoas minor Iliacus Quadrator lumborum Diaphragm
Innervation of posterior wall muscles
Psoas major L1-L3 Psoas minor L1 Iliacus femoral nerve Quadrator lumborum T12-L4 Diaphragm phrenic C3-C5
Abdominal skin reflex
Firmly stroke the skin around the umbilicus - T7-T12 contraction of abdominal muscles
Hiccoughing reflex arc
Sensory fibres travelling with vagus or phrenic then reach the upper spinal cord, medulla RF or hypothalamus
Efferent is phrenic nerve to diaphragm - contraction
Closure of glottis by recurrent laryngeal
Which hernias are medial to the inferior epigastric vessels?
Direct
Which hernias are lateral to the inferior epigastric vessels?
Indirect
Which hernia is more common in elderly men?
Direct
Which hernia can pass into the scrotum or labia majora?
Indirect
….. hernias are far more common in women
Femoral
Femoral hernias are found … to the inguinal ligament
Inferior
