 Functions: 1. Produce spermatozoa 2. Deliver spermatozoa to female repro system 3. Produce male sex hormones BullDog

 Site of spermatogenensis (seminiferous tubules) and testosterone (interstitial cells) production  Located outside abdomen in inguinal region  Housed in a sac of skin - the scrotum

1. Head - contains nucleus of cell › Covered by acrosome  Contains digestive enzymes that help spermatozoon penetrate egg 2. Midpiece - large concentration of mitochondria arranged in a spiral pattern 3. Tail - contains musclelike contractile fibrils › Produces whiplike movement of tail to propel cell forward

Mosby items and derived items © 2008 by Mosby, Inc., an affiliate of Elsevier Inc. 1.gubernaculum 4. testes 2.Penis5. abd cavity 3.inguinal ring6. vas deferens ► Gubernaculum – band of connective tissue that attaches testes to scrotum ► Testes gradually pulled caudally and ventrally ► Inguinal rings - openings in abdominal muscles thru which testes descend

 Sac of skin that houses testes  Helps regulate temperature of testes › Testes must be kept slightly cooler than body temperature  Cremaster muscle attaches to scrotum  Adjusts position of testes relative to body depending on temperature

 Links the testes with the rest of the body.  Contains blood vessels, nerves, lymphatic vessels, and vas deferens. › Only one artery (testicular artery) carries blood down to the testis. › Artery is surrounded by pampiniform plexus-network of veins.  This network helps keep temperature lower than rest of body.  As blood passes down from body, it is cooled by blood returning from the testis in the pampiniform plexus.  Also blood in pampiniform plexus is warmed by the blood in the testicular artery as it goes back to body.

 Connective tissue that forms sheath-like layers around testes and spermatic cord  Visceral vaginal tunic (thin, inner layer) and parietal vaginal tunics (thick, outer layer)form a sac around each testis and spermatic cord  Tunica albuginea - fibrous connective tissue capsule surrounding each testis beneath tunics › Septa divide each testis Into lobules that contain Seminiferous tubules

 Site of spermatogenesis  Long, convoluted U-shaped tube attached to rete testis, a system of ducts  Interstitial cells – endocrine cells between seminiferous tubules – produce testosterone › Under the influence of LH/Interstitial cell- stimulating hormone  Sertoli cells - Support developing spermatids › Large “nurse” cells that shield spermatazoa from the body’s immune system

 After detaching from Sertoli cells, spermatozoa enter rete testis, then flow through efferent ducts to epididymis › Long convoluted tube that connects efferent ducts of testis with vas deferens › Storage and maturation of spermatozoa  Must mature for at least a week before ejaculation. If they never leave this site, they will die out and be reabsorbed (vasectemized animals) › “ Head" - site where spermatozoa enter from efferent ducts › “ Body" - lies along surface of testis › “ Tail" – continues on to become vas deferens Sperm produced Sperm stored

 Muscular tube within the spermatic cord that connects the epididymis to the urethra › must propel sperm quickly at time of ejaculation  In the abdomen it passes through inguinal ring then separates from spermatic cord and connects with urethra  Ampulla – enlargement of vas deferens just before it joins urethra › contain glands that contribute material to semen

 Pelvic portion - entry point of vas deferens and accessory reproductive glands  Penile portion - runs length of penis › Spermatozoa from vas deferens and secretions from accessory reproductive glands enter urethra and are pumped out as semen  Carries urine from bladder › Urine flow temporarily blocked during ejaculation

 Prostate, Seminal Vesicles, Bulbourethral glands › Produce alkaline fluid to help neutralize acidity of female reproductive tract › Provide nutrients for sperm (electrolytes, fructose for energy, prostaglandins for female contractions)  Ducts of all accessory reproductive glands enter pelvic portion of urethra › Different species have different combinations of accessory reproductive glands

Prostate gland  Surrounds urethra and has multiple ducts to carry secretions into urethra Bulbourethral glands (Cowper's glands)  Ducts enter urethra near caudal border of pelvis  Secrete mucinous fluid just before ejaculation that clears and lubricates urethra for passage of semen Seminal Vesicles (vesicular ducts)  Present in all animals except dog and cat  Enter pelvic urethra in same area as vas deferens A = stallion B = bull C = boar D = dog

 Male breeding organ composed of muscle, erectile tissue, and connective tissue › Proportion of each varies between species  Urethra runs down the center  Has large blood supply and many sensory nerve endings  When the male is aroused and stimulated, the erectile tissue becomes engorged with blood and the penis will enlarge and stiffen to allow for copulation.  Three main parts: root, body, and glans › Roots of penis - bands of connective tissue (crura) that attach penis to pelvis and are covered by ischiocavernous muscles

› Body of penis – Largest part, mainly composed of two bundles of erectile tissue (spongy network of fibrous connective tissue and many tiny, blood-filled spaces called sinuses )  In non-erectile state, amount of blood in = amount of blood out  During erection, more blood flows in and sinuses engorge, causing penis to enlarge and stiffen. Less blood is able to flow out.  The two areas of erectile tissue are smaller the corpus cavernosum urethrae (corpus spongiosum) and the larger corpus cavernosum penis

 Glans of penis – distal end; numerous sensory nerve endings › structure varies among species  cat- spines, ruminants – small glans, horses – large amount erectile tissue  Prepuce - sheath of skin that encloses the penis when it is not erect › Inner portion is smooth, moist mucous membrane. Outer portion is normal skin.

 Os penis - bone in penis; urethra runs through groove on ventral surface  Bulb of glans - enlargement toward rear of glans › Engorges with blood (derived from tissue of corpus spongiosum); reaches full size after ejaculation › Remains clamped in place by contractions of muscles surrounding vagina and vulva, preventing the male from withdrawing the penis › Erection of bulb subsides in 15 – 20 minutes Os penis Urethra Bulb of glans

 S shape of nonerect penis of bull, ram, boar  Higher proportion of CT to erectile tissue than other species (so penis doesn’t enlarge much during an erection)  Erection results from straightening of sigmoid flexure  Causes penis to protrude from prepuce for breeding › Retractor penis muscle stretches during erection

 Erection : enlargement and stiffening of the penis › results from a parasympathetic reflex triggered by sexual stimuli  Stress inhibits reproduction › Often involves olfactory cues (pheromones) and behavioral changes › Arteries dilate and increase blood flow into penis › Veins are compressed against brim of pelvis reducing outflow of blood

 Ejaculation : reflex expulsion of semen from penis › Produced by stimulus of erection as well as physical sensations of breeding. › 2 stages:  Movement of spermatozoa to pelvic portion of urethra  Sphincter in urinary bladder closes  Rhythmic contractions of urethra that pump semen out