Hi Pam, I could not have put it any better myself. You are 100% correct.
Indeed the posterior wall is Hesselbachs triangle and it is indeed made from TA and IO collagen.
When it gets a hole in it you have a direct hernia and the fat passes through the posterior wall into the canal then begins to slide down the canal towards the superficial ring.
Correct.
Pam,
For the second part of your question:
The inguinal canal itself is a necessary pathway.
There are several locations where contents from the peritoneal cavity exit the peritoneal cavity. (Inguinal canal, femoral ring, obturator foramen etc).
The functions of the inguinal canal include:
Allowing transit of the testicle from the peritoneal cavity into the scrotum.
Passage of the pampiniform plexus
Passage of the Vas deferens
Passage of lymphatics
Passage of the genital branch of the genitofemoral nerve.
All of this is achieved by the inguinal canal.
BUT in order to perform these important functions of allowing passage of these structures it must have a seal at the peritoneal cavity end preventing other unwanted peritoneal contents to pass out of the peritoneal cavity. We call this seal the deep ring. If the deep ring is functioning properly all of the structures listed can pass through the canal but nothing more. If fat or bowel etc manages to sneak through the deep ring we have an indirect inguinal hernia.
It also happens that the posterior wall of the canal is also vulnerable and made of simply thin collagen. Immediately under the posterior wall is peritoneal contents (fat and bowel etc) and if the posterior wall is torn in any way this allows passage of the peritoneal contents into the canal in the form of a direct inguinal hernia.
I don’t really consider the anterior wall of the canal but I think the external oblique collagen is the likely source.
So yes, the canal is indeed a potential space filled with important anatomical structures, but if the deep ring or the posterior wall fail that potential space can be invaded and distended by other peritoneal contents that should have been excluded (fat and bowel mainly) in the form of a hernia.
Similar logic can be applied to the femoral ring and the obturator foramen.
It is a constant challenge in not only human design, but also design in general.
If I am building an aviary to keep birds I need a gate that allows me in to feed them but does not allow them to fly out. It also must ensure the cat can not get into the aviary when I enter it !
Same dilemma really ! How do I allow veins, nerves and lymphatics to pass from the peritoneal cavity to the scrotum without allowing fat and bowel to also exit !
Steve