Penis and Prepuce

Question 1

Cavernous/erectile tissue of the penis

Answer 1

-Corpus cavernosum penis: located in the root and most of the body of the penis
-Corpus spongiosum penis: located throughout the penis; more delicate that CCP; has larger blood spaces separated by thinner septae
-Corpus spongiosum glandis of the bulbus glandis: located in the bulbus glandis of the glans penis
-Corpus spongiosum glandis of the pars longa glandis: located in the pars longa glandis of the glans penis

Question 2

Ischiocavernosus m.

Answer 2

Paired skeletal muscle; arises from ischiatic tuberosity, covers the crus of the penis and inserts distally on the crus

Contraction of mm. causes blood to flow through corpus cavernosum and corpus spongiosum during erection; also aids in propelling sperm through urethra

Question 3

Bulbospongiosus m.

Answer 3

Skeletal muscle; covers bulb of penis and inserts on the body of the penis; located between ischiocavernosus muscles; palpable

Contraction of mm. causes blood to flow through corpus cavernosum and corpus spongiosum during erection; also aids in propelling sperm through urethra

Question 4

Retractor penis m.

Answer 4

Paired smooth muscle; retracts the penis

Question 5

Ischiourethralis m.

Answer 5

Paired; contracts during erection resulting in fibrous ring clamping down on dorsal vv. of the penis

Question 6

Regions of the penis

Answer 6

Root, body, glans

Question 7

Root of penis in dogs

Answer 7

-Crura (left and right) - composed of corpus cavernosum penis; covered by ischiocavernosus m.
-Bulb of penis - expansion of corpus spongiosum penis; covered caudally by bulbospongiosus m.
-Urethra surrounded by corpus spongiosum penis
-Retractor penis m. - courses along caudal aspect of penis

Question 8

Body of penis in dogs

Answer 8

-Corpus cavernosum penis surrounded by tunica albuginea
-Urethra surrounded by corpus spongiosum penis
-Proximal part of os penis - corpus cavernosum ends and os penis begins
-Retractor penis m.

Question 9

Os penis - dogs

Answer 9

Adds rigidity for intromission
Fibrocartilage tip deforms the apex of the penis in the vagina
Urethra passes through urethral groove on ventral surface
Located in distal part of body of the penis and in entire glans of penis

Question 10

Glans of penis in dogs

Answer 10

-Composed of bulbus glandis and pars longa glandis
-Os penis
-Urethra surrounded by corpus spongiosum penis

Question 11

Canine prepuce

Answer 11

-Fold of skin covering glans of penis
-Preputial orifice
-Pars longa glandis and half of bulbus glandis project into preputial cavity
-Preputial fornix
-Lymphoid nodules are present near fornix on the internal and penile laminae

Question 12

Components of feline penis

Answer 12

-Apex (directed caudoventrally)
-Small os penis
-Root
-Body
-Small glans
-Keratinized spines on free end of penis (testosterone dependent, regress completely after castration)

Question 13

Feline prepuce

Answer 13

-Preputial orifice
-Preputial fornix
-Preputial mm. pull the prepuce cranially during copulation

Question 14

Blood supply to the penis

Answer 14

-Internal pudendal artery which continues into artery of the penis - main source of blood supply
-External pudendal artery

Question 15

Artery of the penis

Answer 15

-Artery of the bulb - supplies bulb of penis, corpus spongiosum penis, penile urethra
-Deep artery of the penis - supplies the tunica albuginea, corpus cavernosum penis, and os penis
-Dorsal artery of penis - supplies the prepuce, superficial surface of penis, and pars longa glandis (preputial, deep, and superficial brs.); blood from pars longa glandis supplies bulbus glandis (no direct blood supply to bulbus glandis)

Question 16

Venous return from penis

Answer 16

Veins drain into internal and external pudendal veins
-Right and left dorsal veins of the penis join at ischial arch before diverging and draining into right and left internal pudendal veins

Question 17

Venous return flow from penis

Answer 17

Internal pudendal v. -> internal iliac v.
External pudendal v. -> external iliac v.
Right and left internal and external iliac vv. join to form common iliac vv. -> join to form caudal vena cava

Question 18

Lymphatics of the penis

Answer 18

Lymphatic vessels from penis course to superficial inguinal lymph nodes -> course through inguinal canal to medial iliac lnn.

Question 19

Innervation to the penis

Answer 19

Deep perineal brs. - innervate ischiocavernosus, bulbospongiosus, and ischiourethralis mm.
Dorsal nerve of penis - courses with dorsal arteries and veins; chief sensory nerve of glans penis

Question 20

Erection of penis

Answer 20

During non-erection, blood bypasses vascular spaces of erectile tissue
During erection:
-Pelvic n. (parasympathetic fibers) relaxes smooth muscle (retractor m.), allowing inc. in blood flow to cavernous spaces in erectile tissue; peripheral veins are compressed, occluding venous return
-Somatic sensory stimulation of glands leads to stimulation of mm.
-Somatic sensory innervation of vaginal and vestibular mucosa leads to stimulation of constrictor vestibuli and constrictor vulvae mm.
-Bulbus glandis is last structure to enlarge - no direct arterial supply

Question 21

Phimosis

Answer 21

Congenital or acquired narrowing of preputial orifice; penis is unable to protrude from prepuce

Question 22

Paraphimosis

Answer 22

Extended penis is unable to be withdrawn back into prepuce