View source for Inguinal canal

{{short description|Human abdominal anatomy}}
{{Infobox anatomy
| Name        = Inguinal canal
| Latin       = canalis inguinalis
| Image       = Gray1227.png
| Caption     = Front of abdomen, showing surface markings for arteries and inguinal canal. (Inguinal canal is tube at lower left.)
| Image2      = Gray1143.png
| Caption2    = The [[scrotum]]. On the left side, the cavity of the [[tunica vaginalis]] has been opened; on the right side, only the layers superficial to the [[Cremaster muscle|cremaster]] have been removed. (Right inguinal canal visible at upper left.)
| System      =
}}
The '''inguinal canal''' is a passage in the [[Anatomical terms of location#Anterior and posterior|anterior]] [[abdominal wall]] on each side of the body (one on each side of the [[Anatomical terms of location#Planes|midline]]), which in males, convey the [[spermatic cord]]s and in females, the [[round ligament of the uterus]]. The inguinal canals are larger and more prominent in males.

==Structure==
The inguinal canals are situated just above the medial half of the [[inguinal ligament]]. The canals are approximately 4 to 6&nbsp;cm long,<ref name="Tuma">{{cite journal |last1=Tuma |first1=Faiz |last2=Lopez |first2=Richard A. |last3=Varacallo |first3=Matthew |title=Anatomy, Abdomen and Pelvis: Inguinal Region (Inguinal Canal) |url=https://www.ncbi.nlm.nih.gov/books/NBK470204/#:~:text=The%20inguinal%20canal%20is%20a,to%20six%20centimeters%20in%20length. |website=StatPearls |publisher=StatPearls Publishing |access-date=18 June 2023 |date=2023|pmid=29261933 }}</ref> angled anteroinferiorly and medially. In males, its diameter is normally 2 cm (±1 cm in standard deviation) at the deep inguinal ring.<ref name="MituraKozieł2018">{{cite journal|last1=Mitura|first1=Kryspin|last2=Kozieł|first2=Sławomir|last3=Pasierbek|first3=Michał|title=Ethnicity-related differences in inguinal canal dimensions between African and Caucasian populations and their potential impact on the mesh size for open and laparoscopic groin hernia repair in low-resource countries in Africa|journal=Videosurgery and Other Miniinvasive Techniques|volume=13|issue=1|year=2018|pages=74–81|issn=1895-4588|doi=10.5114/wiitm.2018.72579|pmid=29643962|pmc=5890843}}</ref><ref group="notes">The diameter has been estimated to be ±2.2cm ±1.08cm in Africans, and 2.1 cm ±0.41cm in Europeans.</ref>

A first-order approximation is to visualize each canal as a cylinder.<ref name="titleGross Anatomy Image">{{cite web |url=http://anatomy.med.umich.edu/atlas/abdo_wall64.html |title=Gross Anatomy Image |access-date=2007-11-20 |archive-url=https://web.archive.org/web/20071111202307/http://anatomy.med.umich.edu/atlas/abdo_wall64.html |archive-date=2007-11-11 |url-status=dead }}</ref>

===Walls===
To help define the boundaries, these canals are often further approximated as boxes with six sides. Not including the two rings, the remaining four sides are usually called the "anterior wall", "inferior wall ("floor")", "superior wall ("roof")", and "posterior wall".<ref name="isbn0-443-06612-4">{{cite book |author1=Adam Mitchell |author2=Drake, Richard |author3=Gray, Henry David |author4=Wayne Vogl |title=Gray's anatomy for students |publisher=Elsevier/Churchill Livingstone |year=2005 |pages=260 |isbn=0-443-06612-4 }}</ref> These consist of the following:

{| class="wikitable"
|  || '''superior wall (roof):'''<br> Medial crus of aponeurosis of external oblique<br>Musculoaponeurotic arches of internal oblique and transverse abdominal<br>Transversalis fascia<br>[[conjoint tendon]]

 |- 
 | '''anterior wall:'''<br>[[aponeurosis]] of [[external oblique]]<br>fleshy part of internal oblique (lateral third of canal only)<ref name="isbn0-7817-3639-0">{{cite book |author1=Dalley, Arthur F. |author2=Moore, Keith L. |title=Clinically oriented anatomy |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year=2006 |pages=[https://archive.org/details/clinicallyorient00moor_1/page/217 217] |isbn=0-7817-3639-0 |url-access=registration |url=https://archive.org/details/clinicallyorient00moor_1/page/217 }}</ref><br>[[superficial inguinal ring]] (medial third of canal only)<ref name="isbn0-7817-4255-2">{{cite book |author1=Arthur F., II Dalley |author2=Anne M. R. Agur |title=Grant's Atlas of Anatomy |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year= 2005|pages=102 |isbn=0-7817-4255-2 }}</ref>  || ''(inguinal canal)'' || '''posterior wall:'''<br>[[transversalis fascia]]<br>[[conjoint tendon]] ([[Inguinal falx]], reflected part of inguinal ligament, medial third of canal only)<ref name="isbn0-7817-4255-2"/><br>[[deep inguinal ring]] (lateral third of canal only)<ref name="isbn0-7817-4255-2"/>
 |- 
 |  || '''inferior wall (floor):'''<br>[[inguinal ligament]]<br>[[lacunar ligament]] (medial third of canal only)<ref name="isbn0-7817-4255-2"/><br>[[iliopubic tract]] (lateral third of canal only)<ref name="isbn0-7817-3639-0"/> ||
|}

===Deep inguinal ring===
The '''deep inguinal ring''' ('''internal or deep abdominal ring''', '''abdominal inguinal ring''', '''internal inguinal ring''', ''annulus abdominalis'') is the entrance to the inguinal canal.

====Location====
The surface marking of the deep inguinal ring is classically described as half an inch above the midpoint of the inguinal ligament.<ref name="isbn0-443-07168-3">{{cite book |author=Susan Standring |title=Gray's Anatomy: The Anatomical Basis of Medicine and Surgery |publisher=Churchill-Livingstone |year=2004 |isbn=0-443-07168-3 |page=[https://archive.org/details/graysanatomyanat0000unse/page/1098 1098] |url=https://archive.org/details/graysanatomyanat0000unse/page/1098 }}</ref>

However, the surface anatomy of the point is disputed. In a recent study,<ref>{{cite journal |vauthors=Koliyadan S, Narayan G, Balasekran P |title=Surface marking of the deep inguinal ring |journal=Clin Anat |volume=17 |issue=7 |pages=554–7 |year=2004 |pmid=15376291 |doi=10.1002/ca.10257|s2cid=30726776 }}</ref> it was found to be in a region between the mid-inguinal point (situated midway between the [[anterior superior iliac spine]] and the [[pubic symphysis]]) and the midpoint of the [[inguinal ligament]] (i.e. midway between the [[anterior superior iliac spine]] and the [[pubic tubercle]]). Traditionally, either one of these two sites was claimed as its location. However, this claim is based upon the study's dissection of 52 cadavers, and may not reflect the live ''in vivo'' anatomy.

Some sources state that it is at the layer of the [[transversalis fascia]].<ref name="isbn0-7817-5309-0"/>

====Description====
The deep inguinal ring is an opening in the [[transversalis fascia]].'''<ref name=":022">{{Cite book |last=Sinnatamby |first=Chummy S. |title=Last's Anatomy |publisher= Elsevier Australia|year=2011 |isbn=978-0-7295-3752-0 |edition=12th |pages=226–227}}</ref>''' It is of an oval form, the long axis of the oval being vertical; it varies in size in different subjects, and is much larger in the male than in the female. It is bounded, above and laterally, by the arched lower margin of the transversalis fascia; below and medially, by the [[inferior epigastric vessels]]. It transmits the [[spermatic cord]] in the male and the [[round ligament of the uterus]] in the female.

From its circumference, a thin funnel-shaped membrane, the [[infundibuliform fascia]], is continued around the cord and testis, enclosing them in a distinct covering.

===Superficial inguinal ring===
[[File:Gray393.png|thumb|right|The superficial inguinal ring]]
The '''superficial inguinal ring''' ('''subcutaneous inguinal ring''' or '''external inguinal ring''') is an anatomical structure in the anterior wall of the mammalian [[abdomen]]. It is a triangular opening that forms the exit of the inguinal canal, which houses the [[ilioinguinal nerve]], the genital branch of the [[genitofemoral nerve]], and the [[spermatic cord]] (in men) or the [[Round ligament of uterus|round ligament]] (in women). At the other end of the canal, the [[deep inguinal ring]] forms the entrance.<ref name= "James Harmon, M.D., Ph.D.">James Harmon, M.D., Ph.D., Lecture 13. Human Gross Anatomy. University of Minnesota. September 4, 2008.</ref>

It is found within the [[aponeurosis of the abdominal external oblique muscle|aponeurosis of the external oblique]], immediately above the [[pubic crest]], 1 centimeter above and superolateral to the [[pubic tubercle]]. 
It has the following boundaries—medial crura by pubic crest, lateral crura by pubic tubercle and inferiorly by inguinal ligament.<ref name="isbn0-7817-5309-0">{{cite book |author=Kyung Won, PhD. Chung |title=Gross Anatomy (Board Review) |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year=2005 |isbn=0-7817-5309-0 |page=198}}</ref>

=== Contents ===
The structures which pass through the canals differ between males and females:
* in males: the [[spermatic cord]]<ref name="titleAnatomy Table
s - Inguinal Region">{{cite web |url=http://anatomy.med.umich.edu/gastrointestinal_system/inguinal_tables.html |title=Anatomy Tables - Inguinal Region |access-date=2007-11-20 |archive-url=https://web.archive.org/web/20071121005611/http://anatomy.med.umich.edu/gastrointestinal_system/inguinal_tables.html |archive-date=2007-11-21 |url-status=dead }}</ref> and its coverings, and the [[ilioinguinal nerve]].
* in females: the [[round ligament of the uterus]], and the [[ilioinguinal nerve]].

The classic description of the contents of the spermatic cords in the male are:

3 arteries: artery to vas deferens (or ductus deferens), [[testicular artery]], [[cremasteric artery]];

3 fascial layers: [[External spermatic fascia|external spermatic]], [[Cremasteric fascia|cremasteric]], and [[internal spermatic fascia]];

3 other structures: [[pampiniform plexus]], [[vas deferens]] (ductus deferens), testicular lymphatics;

3 nerves: genital branch of the [[genitofemoral nerve]] (L1/2), sympathetic and visceral afferent fibres, [[ilioinguinal nerve]] (N.B. outside spermatic cord but travels next to it)

Note that the [[ilioinguinal nerve]] passes through the [[Superficial inguinal ring|superficial ring]] to descend into the [[scrotum]], but does not formally run through the canal.

===Development ===

==== In males ====
During development, each [[testicle]] descends from the starting point on the [[posterior abdominal wall]] (para-aortically) from the [[labioscrotal swellings]]  near the kidneys, down the [[abdomen]], and through the inguinal canals to reach the [[scrotum]]. This way, each testicle descends through the abdominal wall into the scrotum {{Clarification needed|reason=As in after?|date=July 2023|text=behind}} the [[processus vaginalis]] (which later obliterates).

==Clinical significance==
{{See also|Inguinal hernia}}
Abdominal contents (potentially including intestine) can be abnormally displaced from the abdominal cavity. Where these contents exit through the inguinal canal, having passed through the [[deep inguinal ring]], the condition is known as an [[Indirect inguinal hernia|indirect or oblique inguinal hernia]]. This can also cause infertility. This condition is far more common in males than in females, owing to the inguinal canal's small size in females.

A hernia that exits the abdominal cavity directly through the deep layers of the abdominal wall, thereby bypassing the inguinal canal, is known as a [[direct inguinal hernia]].

In males with strong presentation of the [[cremasteric reflex]], the testes can—during [[Supine position|supine]] sexual activity or manual manipulation—partially or fully retract into the inguinal canal for a short period of time. In juveniles and adults with inguinal injury, retraction can be prolonged and potentially lead to overheating-related infertility.<ref>{{cite web|last1=Mayo Clinic Staff|title=Retractile testicle|url=https://www.mayoclinic.org/diseases-conditions/retractile-testicle/symptoms-causes/syc-20377197|website=Mayo Clinic|publisher=Mayo Foundation for Medical Education and Research|access-date=10 February 2018}}</ref>

The superficial ring is [[palpation|palpable]]<ref>Moore & Agur, Essential Clinical Anatomy (2007)</ref> under normal conditions. It becomes dilated in a condition called [[athletic pubalgia]]. Abdominal contents may protrude through the ring in [[inguinal hernia]].

Thus lymphatic spread from a testicular tumour is to the para-aortic nodes first, and not the inguinal nodes.

==Additional images==
{{Commons category}}
<gallery>
File:Gray1146.png|The spermatic cord in the inguinal canal
File:Inguinal fossae.PNG|Inguinal fossae
File:Gray401.png|The abdominal inguinal ring
File:Gray547.png|The relations of the femoral and abdominal inguinal rings, seen from within the abdomen. Right side.
File:Inguinalhernia.gif|Diagram of an [[indirect inguinal hernia|indirect]], [[scrotum|scrotal]] [[inguinal hernia]] ([[Anatomical position|median]] view from the left)
File:Spermatic cord 2.jpg|Superficial inguinal ring
File:Slide4Nemo.JPG|Anterior abdominal wall. Intermediate dissection. Anterior view.
</gallery>

==See also==
* [[Superficial inguinal ring]]
* [[Inguinal hernia]]
* [[Tucking]]

==Notes==
{{reflist|group="notes"}}

==References==
{{Reflist}}

* Adam Mitchell; Drake, Richard; Gray, Henry David; Wayne Vogl (2010). Gray's anatomy for students. Elsevier/Churchill Livingstone. pp.&nbsp;286. {{ISBN|0-443-06612-4}}.

==External links==
* {{SUNYAnatomyLabs|36|01|01|02}}
* {{SUNYAnatomyFigs|36|01|03}} - "The inguinal canal and derivation of the layers of the spermatic cord."
* {{SUNYAnatomyImage|7|3|62}}
* {{SUNYAnatomyLabs|35|09|01|01}} - "Anterior Abdominal Wall: Borders of the Superficial Inguinal Ring"
* {{SUNYAnatomyFigs|36|01|13}} - "The inguinal canal and derivation of the layers of the spermatic cord."
* {{UMichAtlas|abdo_wall63}} - "The Male & Female Inguinal Canal"
* [https://web.archive.org/web/20060505130412/http://www.nurseminerva.co.uk/images/hernia2a.jpg Diagram at nurseminerva.co.uk]
* {{NormanAnatomy|inguinalregion}}
* {{UMichAtlas|abdo_wall65}} - "The Coverings of the Inguinal Canal, External & Internal Oblique & Transversus Abdominis Removed"

{{Muscles of trunk}}
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[[Category:Abdomen]]