Inguinal Region

Transversalis Fascia

Lines the inner aspect of all abdominal musculature.  Distinction between tendon of transversus above & transversalis fascia below on post wall of inguinal canal not clear-cut - debate. Anyway, this layer is stitched in some repairs.

Two thickenings: (1)  iliopubic tract (think of as “inguinal ligament” of transversalis fascia ie its lower limit), & (2)  sling around which cord structures turn to enter inguinal canal. 

Layer from transversus taken with cord = internal spermatic fascia.

Transversus Abdominis & Internal Oblique Muscles

The integrity of inguinal canal depends on the anterior wall laterally, and the posterior wall medially.

-           remember that part of IO and transversus arise from the lateral inguinal ligament.

-           The free lower border of these arch over the cord from lateral to medial, now inserting into the inguinal ligament (and pubis pectineal line) as the aponeurotic conjoint tendon (243). (not actually fused in most; old)

It is the key reinforcement of the posterior canal behind the superficial inguinal ring.

-           supplied here by L1

Testis pushes through these muscles in descent \ IO and transversus layers together give rise to cremaster muscle and fascia.

External Oblique Muscle (232)

Entirely aponeurotic in inguinal (inserting) part; superficial inguinal ring is a gap in this aponeurosis (Pl 232) (base=pubic crest; margins = crura of ring)

-           aponeurosis & superficial ring covered by fascial layer; this layer carried with testis as external spermatic fascia. 

Inguinal ligament = inferior limit of EO.  Some fibres pass back to a ridge on top of pubis (pectineal line) as the lacunar ligament of Gimbernat. 

-           the crescentric free-edge of this  lacunar ligament = medial margin of the femoral ring

-           Lateral extension of tissue from lacunar ligament = pectineal ligament, giving rise to pectineus muscle & fascia. (Pl 233,243); strong and holds sutures well

Note also the reflected inguinal ligament which passes under the spermatic cord to interdigitate in linea alba on the opposite side (Pl 233).

Deep Inguinal Ring (245)

Testis during descent pushes abdominal wall in front of it \ scrotum = extension of abdominal wall. 
Origin lies
behind internal oblique and below transversus (due to more lateral origin of transversus). 

-           Is an opening in the  transversalis fascia - which forms superior and inferior crura
Inf. epigastric artery arises vertically directly medial to the dp ring

Surface marking = 1.25 cm above mid-inguinal point; junction of line between ASIS and upper border of pubic symphysis.
Slightly medial and above the midpoint of the inguinal ligament.

Inguinal Canal (245)

6cm long in adults.  Contains spermatic cord or round ligament, and ilioinguinal nerve. 

Anterior wall: EO aponeurosis + some fleshy IO laterally

Floor: in-rolled edge of inguinal ligament , reinforced medially by lacunar ligament

Posterior wall: transversalis fascia (weak); conjoint tendon medially (strong)

Roof: arching fibres of IO and transversus.

Hesselbach’s triangle: inferior epigastric, lateral edge of rectus and inguinal ligament. (Pl243)

Integrity: depends on anterior wall laterally, and posterior wall medially.

-           when the intra-abdo P rises, the aponeuroses should push the canal flat.

-           Note (Pl245) how the conjoint tendon behind the superficial ring reinforces this area.

-           Laterally some transversus fibres (the interfoveolar ligament) arch to support deep ring.

Structures deep to posterior wall of canal (236)

Inferior epigastric artery (from external iliac) pierces transversalis fascia to run superficial to it and enter rectus sheath below arcuate line.

-           gives off cremasteric branch at deep ring (supplies cremaster and the cord coverings)

-           direct hernia pass medial to the inf epigastric, indirects pass lateral to it

-           indirects differentiated from femoral hernias as they are above/medial the pubic tubercle

Ductus deferens / round ligament hook around the interfoveolar ligament to enter deep ring

The spermatic cord (245):

Males (6 groups of constituents):

i)                       ductus deferens

ii)                     arteries: testicular artery & arteries to ductus and cremaster

iii)                   veins: the pampiniform plexus

iv)                   lymph: from testes to para-aortic nodes (and from coverings ® external iliac nodes

v)                     nerves: genital branch of the genitofemoral nerve  (® cremaster) & sympathetics

vi)                   processus vaginalis: obliterated remains autonomic nerves

Females:

i)                       round ligament

ii)                     processes vaginalis

iii)                   lymphatics (of the uterus)

Note that the ilioinguinal nerve, while a content of the canal, does not enter the deep ring, but pierces the IO (see Pl 245)

-           then it leaves via the superficial ring to supply the inguinal region, upper thigh, anterior third of scrotum (or labia majora) and the root of the penis

Fascial coverings (3):

i)                       Transversalis fascia ® internal spermatic fascia

ii)                     Transversus (and IO and inguinal ligament) ® cremasteric fascia and muscle (loops down around tunica vaginalis of testes to the pubic tubercle, can elevate testes)

iii)                   Fascia over external oblique ® external spermatic fascia

Nerves of Inguinal Canal 

Iliohypogastric and ilioinguinal nerves arise from L1 root --> pierce IO 2 & 3cm superomedial to ASIS to lie between it and EO. 

Iliohypogastric runs parallel to & above cord ® suprapubic skin.; usually 2cm+ above inguinal hernia incision.
- supplies suprapubic skin.

Ilioinguinal runs on cord superficial to cremaster ® scrotal/labial skin, base of penis. At risk opening the sheath and when superficial ring being closed at end of procedure.
- supplies scrotal or labial skin and skin in the pubic region.

Both nerves supply lowermost fibres of IO & TA; contraction of these fibres has shutter-like action tightening the conjoint tendon and high division of nerves (eg at appendicectomy) ® ­risk of direct inguinal hernia. 

Genital branch (L2) of genitofemoral nerve lies posterior to cord ® scrotal/labial skin + medial thigh + cremaster muscle. Identify with cremasteric vessels; at risk cleaning tissue of deep ring.
- division --> loss of labial / scrotal skin sensation and in male can cause a low-lying testicle.

Blood Vessels of Inguinal Canal

Important in males:

Testicular artery:  from aorta

Cremasteric Artery: from inferior epigastric ® cremaster and cord. 

Deferential Artery (to vas):  from superior vesical.

Pubic branch arises from inferior epigastric ® runs along iliopubic tract medially to anastomose with obturator vessels.  Enlargement = accessory obturator artery, if obturator artery absent this vessel = abnormal obturator artery.

Femoral sheath

Femoral sheath is formed from fascia adjacent to iliacs as they exit under the inguinal ligament and become frmoral vessels.

Posterioerly = pectineal ligament; below = pectineus fascia.
Lateral = iliopsoas muscle  is oblique; also forms part of posterior wall; as is oblique
Anterior = iliopubic tract part of transversalis fasci; this curves medially; bounds the medial part of the opening into the femoral sheath.
- eventually ends about 4cm below inguinal ligament by fusing with adventitia of the vessels
Septa divide into lateral (artery); middle (vein); and medial (fem canal) compartments.

Femoral canal
Empty of structures apart from some fat, lymph and Cloquet's node
Femoral ring is at its entrance; bounded by tissue of femoral sheath;
- anterior: iliopubic tract of TF in front of inguinal ligmant
- medial = iliopubic tract then lacunar ligament
- posterior = pectineal ligament
- laterally = femoral vein
Canal lasts 1-2cm then walls fuse.

Femoral Hernia
Initially is deep to fascia lata; difficult to feel
Enlarges --> protrudes through region where saphenous vein penetrates deeo
- limited distally by superficial fascia of abdomen inserting into thigh; so may bulge above the inguinal ligament as it expands.

Peritoneal Folds From Lap View

Median umbilical ligament is inconsistent (dome of bladder to umbilicus)
Medial ligament is obliterated umbilical artery = very consistent (anterior division of internal iliac)
Lateral umbilical ligament = not regularly seen; formed by inferior epigastric vessels.