What are "Entresijos" and "Gallinejas"?

We've recently had in Madrid the festivities in honor of its patron saint "San Isidro" (which official day is May 15th). They're celebrated in the "pradera de San Isidro" (medow), where you can find many food stalls and fairground rides. Two of the most traditional foods in Madrid are "Entresijos" and "Gallinejas", and they can be found almost in every stall there these days.
But what are they? Find it below!

Gallinejas probably should be translated as Chitterlings and are the intestines of a suckling pig, though they can be from other animals, and in Madrid they are usually from baby lamb. They are deep fried and usually server as "bocatas" (a "bocadillo", which is short name is "bocata", is sandwich made with french bread or alike -in oposition to sliced bread), so traditional in Madrid (but I'll speak of bocadillos in another post).

Entresijos, on the other side, is the part of the intestine called "mesentery". In fact, when eating "gallinejas", part of the mesentery is left (on purpose), so they are eaten together.

Besides de "San Isidro" festivities, few restaurants in Madrid still serve it in the menu: many people find them disgusting -knowing what are they made of, not because of having tried them-. Most of the ones still serving them are in the most "traditional, pure-blood quarters of Madrid (they were villages near Madrid in the past, before being absorbed by the growth of the capital), such as Carabanchel, Vallecas and Arganzuela.

Restaurants serving Gallinejas and Entresijos all year round:

• http://www.gallinejasembajadores.com/
• https://www.facebook.com/pages/Los-Madro%C3%B1os-Gallinejas-y-Entresijos-de-Madrid-/399386920075720
• Some others: http://www.yelp.es/search?cflt=restaurants&find_desc=gallinejas&find_loc=Madrid

By the way, I personally liked Gallinejas more ;)