Gastrointestinal: Anatomy - Inguinal ligament and canal Flashcards
Where does the inguinal ligament run?
Between ASIS and pubic tubercle
What structure forms the inguinal ligament? Where does it insert?
Inferior part of the external oblique aponeurosis
Most fibres insert into pubic tubercle
Some travel posteriorly and attach to superior pubic ramus (lateral to tubercle) to form lacunar ligament
Some superior fibres cross linea alba and blend with inferior contralateral external oblique aponeurosis to form the reflected inguinal ligament
What forms the lacunar ligament?
Fibres from inguinal ligament which travel posteriorly and attach to superior pubic ramus (lateral to tubercle)
What forms the medial border of the subinguinal space?
Lacunar ligament
What structure forms the iliopubic tract?
Inferior part of transversalis fascia
Describe the course of the iliopubic tract relative to the inguinal ligament
Runs parallel and posterior (deep) to inguinal ligament to reinforce the posterior wall and floor of the inguinal canal
How long is the inguinal canal?
4cm
Where is the inguinal canal located?
Parallel and superior to the middle half of the inguinal ligament
What forms the coverings of the spermatic cord?
- Internal spermatic fascia (from transversalis fascia)
- Cremasteric fascia (investing fascia of superficial and deep surfaces of internal obliques) and muscle
- External spermatic fascia (external oblique aponeurosis and investing fascia)
Nine contents of the spermatic cord
- Ductus deferens
- Artery of ductus deferens
- Testicular artery
- Cremasteric artery
- Pampiniform venous plexus
- Lymphatic vessels
- Sympathetic nerve fibres
- Genital branch of genitofemoral nerve
- Vestige of processus vaginalis
What is the ductus deferens and how long is it?
~45cm muscular tube which conveys sperm from epididymis to ejaculatory duct
What does the pampiniform venous plexus form?
Testicular vein
What nerve innervates the cremaster?
Genital branch of the genitofemoral nerve (L1-2)
Where do the lymphatic vessels of the spermatic cord drain to?
Lumbar lymph nodes
Describe the contents of the inguinal canal in males and females
Male: spermatic cord
Female: round ligament of uterus
Both: ilioinguinal nerve
How does the ilioinguinal nerve enter the inguinal canal?
Pierces transversus abdominis and internal oblique muscles (does not enter via deep ring)
Where is the deep inguinal ring located relative to the inguinal ring and the inferior epigastric artery?
Superior to middle of inguinal ligament (2 fingers breadth above)
Lateral to inferior epigastric artery
What forms the deep inguinal ring?
Invagination in transversalis fascia
What forms the superficial inguinal ring?
Split in diagonal fibres of external oblique aponeurosis
Where is the superficial inguinal ring in relation to the pubic tubercle?
Medial to the pubic tubercle
What are the margins of the superficial ring called? Where do they attach?
Margins are crura
Lateral crus attaches to pubic tubercle
Medial crus attaches to pubic crest
Posterior and anterior boundaries, floor and roof of lateral 1/3 of inguinal canal (deep ring)
Posterior: transversalis fascia
Anterior: internal oblique, lateral crus of external oblique aponeurosis
Floor: iliopubic tract
Roof: transversalis fascia
Posterior and anterior boundaries, floor and roof of middle 1/3 of inguinal canal
Posterior: transversalis fascia
Anterior: external oblique aponeurosis
Floor: inguinal ligament
Roof: internal oblique and transversalis abdominis musculo-aponeurotic arches
Posterior and anterior boundaries, floor and roof of medial 1/3 of inguinal canal (superficial ring)
Posterior: inguinal falx (conjoint tendon to internal oblique and transversalis abdominis), reflected inguinal ligament
Anterior: external oblique aponeurosis (intracrural), external oblique fascia (which becomes the external spermatic fascia)
Floor: lacunar ligament
Roof: medial crus of external oblique aponeurosis
Seven layers of the scrotum, from superficial to deep
- Skin
- Subcutaneous tissue (dartos fascia) and dartos muscle
- External spermatic fascia
- Cremasteric muscle
- Cremasteric fascia
- Internal spermatic fascia
- Tunica vaginalis with visceral layer (covering testis and epididymis) and parietal layer
Describe the vascular supply of the scrotum
Arterial:
- Posterior scrotal branches of perineal artery (from internal pudendal)
- Anterior scrotal branches of deep external pudendal artery (branch of femoral)
- Cremasteric artery (branch of inferior epigastric)
Venous:
- Scrotal veins accompany arteries
Lymphatics:
- Drain to superficial inguinal lymph nodes
Describe the innervation of the anterolateral, anterior, posterior, and posteroinferior surfaces of the scrotum
Anterolateral: genital branch of genitofemoral nerve (L1-2)
Anterior: anterior scrotal nerves from ilioinguinal nerve (L1)
Posterior: posterior scrotal nerves from perineal branch of pudendal nerve (S2-4)
Posteroinferior: perineal branches of posterior cutaneous nerve of thigh (S2-3)
Describe the passage of sperm from the testis
- Sperm produced in seminiferous tubules
- Seminiferous tubules joined by straight tubules to form rete testis
- Efferent ductules
- Lobules of epididymis
- Head, body and tail of epididymis
- Ductus deferens
- Ductus deferens joins seminal gland and empties into ejaculatory ducts
- Ejaculatory ducts empty into prostatic urethra
What are the predisposing factors for indirect vs direct hernias?
Direct (acquired):
- Weakness of anterior abdominal wall in inguinal triangle (e.g. due to distended superficial ring, narrow inguinal falx, attenuation of aponeurosis in males >40yo)
Indirect (congenital):
- Persistent patency of processus vaginalis in younger persons
Which is more common: indirect or direct hernias?
Direct less common (1/3 to 1/4)
Indirect more common (2/3 to 3/4)
How do direct hernias exit the abdominal cavity? How does this differ from indirect hernias?
Direct hernias:
- Peritoneum plus transversalis fascia (lies outside inner one or two fascial coverings of cord)
Indirect hernias:
- Peritoneum of persistent processus vaginalis plus all three fascial coverings of cord or round ligament
Describe the course of direct vs indirect hernias
Direct hernias:
- Through or around inguinal cord
- Usually traversing only medial 1/3, external and parallel to vestige of processus vaginalis
Indirect hernias:
- Traverses inguinal canal (entire if sufficient size within processus vaginalis)
How do direct hernias exit the inguinal canal? How does this compare to indirect hernias?
Direct hernias:
- Via superficial ring, lateral to cord
- Rarely enters scrotum
Indirect hernias:
- Via superficial ring, inside cord
- Commonly passes into scrotum/labia majora
Describe the borders of the inguinal triangle. What is the clinical significance of the inguinal triangle?
Medial: lateral border of rectus abdominis
Lateral: inferior epigastric vessels
Inferior: inguinal ligament
Area of direct weakness through which direct hernias may arise
