The dialect of the blessing of Asher Yatzar is recorded in Tractate Brachos 60b. The Rishonim discuss the meaning behind different words stated in this blessing. There exist a number of variations of dialects of the blessing. The Arizal writes that this blessing contains 45 words, and this is the dialect that is followed in the Siddur.
בחכמה/Bichochma: The word Bichochma is recited because the creation of a human involves wondrous wisdom. Alternatively it is recited because of the great wisdom involved in Hashem creating the body in a way that the soul inside the body does not escape through the many orifices it contains. Alternatively it is recited because of the wisdom involved in Hashem first creating man’s sustenance [on the first 5 days of creation] and only afterwards did he create man [on the sixth day]. [Alternatively it is recited because Hashem created man with wisdom, in contrast to animals.]
נקבים נקבים חלולים חלולים/Nikavim Nikavim, Chalulim Chalulim: Hashem created many holes [Nikavim] such as the mouth, nostril, anus. He also created many hollow limbs [Chalulim] such as the heart, stomach, and intestines.
שאם יסתם אחד מהם/Sheim Yisasem: This refers to the mouth. Amongst the Nikavim there is one hole, which is the mouth, that when it is in its mother’s womb it is closed and when it enters the world it opens. If it were to remain closed upon entering the world one would not be able to live for even one hour. Alternatively, it refers to all the holes [Nikavim] of a person. As if the anus and urethra [Nikavim] were to close, then eventually when the limit is reached a person will not be able to live for even one hour.
או אם יפתח אחד מהם/Im Yipaseiach: This refers to the stomach and intestine [Chalulim] that if they were to be punctured one would not be able to survive. Alternatively if these holes were to be constantly open in a way that one is constantly defecating then one would not survive.
רופא כל בשר/Rofei Chol Basar: This refers to the ability to urinate and defecate, as if the excrement were to remain in one’s body for a long period it would spoil in his stomach and he would die. Thus expelling the excrement is a cure.
ומפליא לעשות/Umafli Laasos: A body is similar to a flask filled with air and hence naturally the air should leave if even a small hole is punctured. The wonder of the body is that despite it being full of holes its spirit is still guarded within it. Alternatively the wonder is that the body separates the nutrients from the waste of the food. Alternatively it is a wonder of Hashem that he guards a man’s soul in his body and hence connects a spiritual item with the physical, thus allowing a person to remain healthy. It is for this reason that we say “the healer of all flesh”.
The meaning of the blessing according to Kabala:
ברוך/Baruch: When one recites the word “Baruch” he is to intend to draw the Neshama to Keser.
אתה/Ata: To draw the Neshama to Chochma.
השם/Hashem: To draw the Neshama to Bina.
אלוקינו מלך העולם/Elokeinu Melech Haolam: This refers to Tiferes.
אשר יצר את האדם בחכמה /Asher Yatzar Es Hadam Bichochmah: That he created man with Chochma of Atzilus.
נקבים נקבים חלולים חלולים/Nikavim Nikavim, Chalulim Chalulim: The holes that remain constantly open, such as the nose and the mouth, refer to the channels of Divine flow [and Neshama] that travel from one Sefira to another [until it reaches its destination in this world]. The holes that are normally closed and only open upon need, such as the urethra and rectum, refer to the lower external channels of spiritual effluence that travel to the impure Kelipos.
שאם יסתם אחד מהם/Sheim Yisasem: If one of the respiratory organs were to close one would immediately choke and die. This refers to the channels above, that if they were to close the Midos would not receive their Divine energy and the Neshama would not descend below, hence causing massive death.
או אם יפתח אחד מהם/Im Yipaseiach: If the intestines were constantly open to allow the food to flow out one would not retain any nutrients and would die. This refers to the channels above, that if they were to be constantly open the Kelipos would receive all of the Divine energy, not allowing the side of holiness and good to nurture from it. This would cause death below. This is similar to the rectum from which the Kelipos nurture from, that if the food went straight to it without stopping and being digested into the body, one would surely die.
ומפליא לעשות/Umafli Laasos: Hashem made a wonder in the creation by creating man in a resemblance of the Divine worlds.
 Michaber 6/1; This Halacha is omitted in Admur chapter 6.
 Shaar Hakavanos Drushei Al Netilas Yadayim; Peri Eitz Chaim Shaar Habrachos 4; brought in M”A 6/2; Yifei Laleiv 1/13. The dialect of the 45 words is brought in Kaf Hachaim 6/1 and is the same as that written by Admur in the Siddur. The reason behind 45 words is because 45 is the Gematria of Adam, and it represents “Mah” which is Chochma. [Shaar Hakavanos, brought in Shaar Hakolel 1/9] There are dialects however that contain more than 45 words. [Majority of Siddurim of Nussach Sefarad] The Rokeiach writes it contains 43 words. The Yaavetz writes it contains 47 words.
 A body is similar to a flask filled with air and hence naturally the air should leave if even a small hole is punctured. The wonder of the body is that despite it being full of holes its spirit is still guarded within it. [Rashi “Umafli Laasos” Brachos 60b; Michaber ibid]
 Tosafus “Asher Yatzar” Brachos 60b; Michaber ibid
 Maharsha Brachos ibid
 Why do we repeat Chalulim Chalulim: The Midrash [Tanchuma Shemini] writes that the Gematria of Chalulim Chalulim is 248, corresponding to the 248 limbs in the body.
 What is said first; Yipaseiach or Yisaseim? In the Siddur Admur writes first Yisaseim, and so writes Siddur Rasag; Rambam Tefilah 7/5; Abudarham; Siddur Arizal; Michaber ibid; Kaf Hachaim 6/1; Darkei Chaim Veshalom 10; Ashel Avraham Butchach as he heard from Harav Levi Yitzchak of Berditchiv. However in the Gemara Brachos 60b the order is first Yipaseiach and then Yisaseim and so writes Seder Rav Amram; Rashi; Rif; Rosh; Bahag; Machzor Vitriy and so rules M”B 6/2. The Ashel Avraham Butchach 6 concludes that the order makes no difference.
 The reason the Michaber proposes that the statement is going on the mouth of a newborn is because the verse states that if it remained closed one would not survive for even a moment. We however observe that people can close their mouths for many hours and continue living. He hence establishes it to refer to a newborn of which if his mouth does not open he will not survive. [M”B 6/3] Vetzaruch Iyun as on the contrary babies breathe through their nose and not their mouth, and if we are discussing that both the mouth and nose are closed then even an adult cannot survive more than a number of minutes.
 Both explanations explain the connection between this praise and the use of the bathroom. However the second explanation is connected with the actual bowel movement as opposed to the mere digestive tract. [Michaber ibid]
 Siddur and so writes Michaber ibid; The reason for our Nussach is in order to have 45 words in the blessing. [Shaar Hakolel 1/9] Some omits the words “Afilu Shaah Echas” being that in truth one is able to survive for some time even if Hashem closes his bowels. [M”A 6/2] The M”B concludes that this is their custom. [M”B 6/3] Some write one is to say Achas opposed to Echas. [Siddur Shlah]
 This is the Nussach of the Gemara Brachos ibid.
 Some say Rofei Cholei Kol Basar. [Michaber ibid] Others rule one is not to say Cholei [Shlah; Bach; Mateh Moshe, M”A 6/3; brought in M”B 6/4] and so rules Admur in 7/5 and so writes Admur in Siddur. The Taz [6/3] concludes both versions are correct.
 What is the law if one did not recite the words “Umafli Laasos”? One fulfills his obligation. [Ashel Avraham Butchach 6] However there are Poskim that argue. [See Tzitz Eliezer 11/4]
 Michaber ibid
 The M”A 6/4 writes in name of the Arizal that this means to say that the soul receives sustenance from the spirituality contained within the food, while the body receives sustenance from the nutrients contained within the food, and through this the soul and body connect through food.
 Heichal Hakodesh 5b