The inguinal canals are the two passages in the

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

abdominal wall of humans and animals which in males convey the

spermatic cord The spermatic cord is the cord-like structure in males formed by the vas deferens (''ductus deferens'') and surrounding tissue that runs from the deep inguinal ring down to each testicle. Its serosal covering, the tunica vaginalis, is an extens ...

s and in females the

round ligament of the uterus The round ligament of the uterus is a ligament that connects the uterus to the labia majora. Structure The round ligament of the uterus originates at the uterine horns, in the parametrium. The round ligament exits the pelvis via the deep ingui ...

. The inguinal canals are larger and more prominent in males. There is one inguinal canal on each side of the

midline In typography, the mean line is the imaginary line at the top of the x-height. upright 2.0, alt=A diagram showing the line terms used in typography Round glyphs will tend to break ( overshoot) the mean line slightly in many typefaces, since thi ...

Structure

The inguinal canals are situated just above the medial half of the inguinal ligament. In both sexes the canals transmit the

ilioinguinal nerve The ilioinguinal nerve is a branch of the first lumbar nerve (L1). It separates from the first lumbar nerve along with the larger iliohypogastric nerve. It emerges from the lateral border of the psoas major just inferior to the iliohypogastric, an ...

s. The canals are approximately 3.75 to 4 cm long. , angled anteroinferiorly and medially. In males, its diameter is normally 2 cm (±1 cm in standard deviation) at the deep inguinal ring.The diameter has been estimated to be ±2.2cm ±1.08cm in Africans, and 2.1 cm ±0.41cm in Europeans. A first-order approximation is to visualize each canal as a cylinder.

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". These consist of the following:

Deep inguinal ring

The deep inguinal ring (internal or deep abdominal ring, abdominal inguinal ring, internal inguinal ring) 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 . However, the surface anatomy of the point is disputed. In a recent study it was found to be in a region between the mid-inguinal point (situated midway between the

anterior superior iliac spine The anterior superior iliac spine ( abbreviated: ASIS) is a bony projection of the iliac bone, and an important landmark of surface anatomy. It refers to the anterior extremity of the iliac crest of the pelvis. It provides attachment for the in ...

and the

pubic symphysis The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubi ...

) and the midpoint of the inguinal ligament (i.e. midway between the

and the

pubic tubercle The pubic tubercle is a prominent tubercle on the superior ramus of the pubis bone of the pelvis. Structure The pubic tubercle is a prominent forward-projecting tubercle on the upper border of the medial portion of the superior ramus of th ...

). 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 The transversalis fascia (or transverse fascia) is a thin aponeurotic membrane of the abdomen. It lies between the inner surface of the transverse abdominal muscle and the parietal peritoneum. It forms part of the general layer of fascia lining ...

Description

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 In human anatomy, inferior epigastric vessels refers to the inferior epigastric artery and inferior epigastric vein. See also *Terms for anatomical location *Hesselbach's triangle In human anatomy, the inguinal triangle is a region of the abd ...

. It transmits the

in the male and the

in the female. From its circumference a thin funnel-shaped membrane, the

infundibuliform fascia The internal spermatic fascia (infundibuliform fascia, or Le deuxième fascia de Webster) is a thin layer, which loosely invests the spermatic cord. Structure The internal spermatic fascia is derived from the transversalis fascia. It is acquir ...

, is continued around the cord and testis, enclosing them in a distinct covering.

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 The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the tors ...

. It is a triangular opening that forms the exit of the inguinal canal, which houses the

, the genital branch of the

genitofemoral nerve The genitofemoral nerve refers to a nerve that is found in the abdomen. Its branches, the genital branch and femoral branch supply sensation to the upper anterior thigh, as well as the skin of the anterior scrotum in males and mons pubis in fema ...

, and the

(in men) or the round ligament (in women). At the other end of the canal, the

deep inguinal ring The inguinal canals are the two passages in the anterior abdominal wall of humans and animals which in males convey the spermatic cords and in females the round ligament of the uterus. The inguinal canals are larger and more prominent in males. Th ...

forms the entrance.James Harmon, M.D., Ph.D., Lecture 13. Human Gross Anatomy. University of Minnesota. September 4, 2008. It is found within the aponeurosis of the external oblique, immediately above the

pubic crest Medial to the pubic tubercle is the pubic crest, which extends from this process to the medial end of the pubic bone. It gives attachment to the conjoint tendon, the rectus abdominis, the abdominal external oblique muscle, and the pyramidal ...

, 1 centimeter above and superolateral to the

. It has the following boundaries—medial crura by pubic crest, lateral crura by pubic tubercle and inferiorly by inguinal ligament.

Development in the male

During development each

testicle A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testostero ...

descends from the starting point on the

posterior abdominal wall In anatomy, the abdominal wall represents the boundaries of the abdominal cavity. The abdominal wall is split into the anterolateral and posterior walls. There is a common set of layers covering and forming all the walls: the deepest being the vi ...

(para-aortically) from the

labioscrotal swellings The labioscrotal swellings (genital swellings or labioscrotal folds) are paired structures in the human embryo that represent the final stage of development of the caudal end of the external genitals before sexual differentiation. In both males a ...

near the kidneys, down the

, and through the inguinal canals to reach the

scrotum The scrotum or scrotal sac is an anatomical male reproductive structure located at the base of the penis that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum co ...

. This way, each testicle descends through the abdominal wall into the scrotum, behind the

processus vaginalis The vaginal process (or processus vaginalis) is an embryonic developmental outpouching of the parietal peritoneum. It is present from around the 12th week of gestation, and commences as a peritoneal outpouching. Sex differences In males, it prec ...

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

Function

The structures which pass through the canals differ between males and females: * in males: the

and its coverings + the

. * in females: the

+ the

. 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 The testicular artery (the male gonadal artery, also called the internal spermatic arteries in older texts) is a branch of the abdominal aorta that supplies blood to the testis. It is a paired artery, with one for each of the testes. It is the ...

cremasteric artery The cremasteric artery (external spermatic artery) is a branch of the inferior epigastric artery which accompanies the spermatic cord to supply the cremaster muscle as well as other coverings of the spermatic cord in the male (whereas in the female ...

; 3 fascial layers: external spermatic,