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.
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.
THIGH
ABDOMEN
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
THIGH
Inguinal ligament (caudal border of the EAO)
Iliopubic eminence
Pectineus muscle
inserting on the iliopubic
eminence
ABDOMEN
Photo by Mr. Keithroy Charles
Tuber coxae
Iliopubic eminence
Modified from WD and
Bettina G Anderson: Atlas
of Canine Anatomy
Inguinal ligament
Pectineus muscle
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
cremaster muscle
vaginal tunic
Aponeurosis of the ext abdl obl
X
ext pudendal a/v and
genitofemoral n
X
Aponeurosis of the ext
abdl obl, where it covers
the rectus abdominis
muscle
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.
Structures forming the deep inguinal ring…
Psoas major m.
Iliacus m.
Psoas minor m.
Ing lig.
Supf ing ring
inguinal ligament
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.
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.
Psoas major m.
Psoas minor m.
caudal epigastric artery
VAGINAL PROCESS
After Miller, Anatomy of the Dog
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.
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?