Canine Inguinal Ligament, Rings, and Canal

All are in the inguinal region.

WHERE IS THE INGUINAL REGION?

• The inguinal region is the lower part of the area of junction of the abdominal wall with the thigh. The junction is demarcated by a deep sulcus that extends from the point of the hip (iliac crest and tuber coxae) to the area between the thighs.

THIGH

ABDOMEN

THE ARROWS POINT TO THE SULCUS THAT IS THE JUNCTION OF THE ABDOMINAL WALL AND THIGH. THE LOWER, SOLID, ARROWS POINT TO THE INGUINAL REGION. THE DOTTED ARROWS POINT TO THE UPPER PART OF THE SULCUS.

Photo by Mr. Keithroy Charles

• THE INGUINAL LIGAMENT…

-The ligament forms the caudal border of the aponeurosis of the external abdominal oblique muscle. -It extends from the tuber coxae to the iliopubic eminence on the cranial margin of the pubis at its junction with the ilium of the hip bone. -The ligament lies against the iliopsoas muscle and femoral vessels that pass from the abdomen to the pelvic limb. That muscle and the vessels pass caudal to the inguinal ligament. -Where the ligament abuts on the muscle and vessels, it is joined to them by fascia.

Tuber coxae

Iliopubic eminence

Pectineus muscle inserting on the iliopubic eminence

Inguinal ligament (caudal border of the EAO)

THIGH

ABDOMEN

Photo by Mr. Keithroy Charles

Tuber coxae

Iliopubic eminence

Pectineus muscle

Inguinal ligament

Modified from WD and Bettina G Anderson: Atlas of Canine Anatomy

vag tunic

testis, w/in vag tunic

WHAT ARE THE INGUINAL RINGS?

• They are two normal openings in the abdominal wall. One is internal to the other and they are designated accordingly: deep inguinal ring, superficial inguinal ring. The space between the two rings is the inguinal canal. In the dog, the two openings lie one directly internal to the other and the inguinal canal hardly exists.

• The inguinal rings and canal allow intraabdominal structures to pass through the abdominal wall, from the abdominal cavity to a subcutaneous position.

• SUPERFICIAL INGUINAL RING: • It is a narrow opening in the aponeurosis of

the external abdominal oblique. • It is about 1 cm cranial to the inguinal ligament. • It is just lateral to the rectus abdominis muscle. • It transmits the vaginal tunic and its contents,

and the external pudendal a./v., and genitofemoral nerve in the male dog.

• It transmits the vaginal process, and the external pudendal a./v., and genitofemoral nerve in the female dog (bitch).

Aponeurosis of external abdominal oblique

Superficial inguinal ring

Photo by Mr. Keithroy Charles

supf inguinal ring

vaginal tunic

cremaster muscle

ext pudendal a/v and genitofemoral n

Aponeurosis of the ext abdl obl

Aponeurosis of the ext abdl obl, where it covers the rectus abdominis muscle

X

X

Photo by Mr. Keithroy Charles

DEEP INGUINAL RING…

• -It is a triangular space directly internal to the superficial ring.

• -The borders of this triangular space are: inguinal ligament caudally; caudal border of the internal abdominal oblique muscle cranially; lateral border of the rectus abdominis medially.

• -It lies directly internal to the superficial inguinal ring and transmits the same structures.

Psoas minor m.

Psoas major m.

Iliacus m.

Ing lig.

Supf ing ring

Structures forming the deep inguinal ring…

superficial inguinal ring

deep inguinal ring shown by the dashed lines

Note that the deep inguinal ring lies directly internal to the superficial inguinal ring. This is the case in all of our domestic mammals that have a caudally located testis: dog, cat, pig.

inguinal ligament

NOTE THAT THE ILIOPSOAS MUSCLE (ILIACUS + PSOAS MAJOR MUSCLES) AND THE FEMORAL AND MEDIAL CIRCUMFLEX FEMORAL VESSELS, ALL STRUCTURES THAT PASS TO THE PELVIC LIMB, PASS CAUDAL TO THE INGUINAL LIGAMENT. The pudendoepigastric trunk is normally quite short, 1 – 2 mm in length, and may be absent. In the figure, it is present and longer than usual.

caudal epigastric artery

Psoas major m.

Psoas minor m.

VAGINAL PROCESS

EXTERNAL PUDENDAL VESSELS (WITH GENITOFEMORAL NERVE)

The bitch: Vaginal process and external pudendal artery and vein are shown in this figure. The genitofemoral nerve has been omitted. In some specimens, you can trace the round ligament of the uterus, a remnant of the gubernaculum, as a delicate fibrous cord extending caudally and ending in the fascia of the labium.

After Miller, Anatomy of the Dog

1. CAN YOU FIND THE FEMORAL ARTERY AND VEIN, WHICH ARE UNMARKED IN THE SIXTH SLIDE?

2. WHAT MUSCLE MUST BE LATERAL TO THESE VESSELS, PASSING CAUDAL TO THE INGUINAL LIGAMENT?

3. A DOG HAS A HERNIA IN WHICH A LOOP OF SMALL INTESTINE ENTERS THE VAGINAL RING AND PASSES WITHIN THE VAGINAL TUNIC, EXTENDING TO THE TESTIS. DOES THIS LOOP OF INTESTINE PASS THROUGH THE DEEP INGUINAL RING? THROUGH THE SUPERFICIAL INGUINAL RING?