Male reproductive system Flashcards
What does each testis consist of and what is the sight of spermatogenesis
Each testis consists of a mass of seminiferous tubules surrounded by a heavy fibrous capsule
The seminiferous tubules are the site of spermatogenesis (formation of spermatozoa)
testes function
Spermatogenesis
Delivery of spermatozoa to female to allow procreation
Hormone Production
There are cells between the seminiferous tubules
Two types of hormones produced in testes
Interstitial (or Leydig) cells
Stimulated by luteinizing hormone (LH) from anterior pituitary
Androgens produced in testes
Primarily testosterone
Responsible for male secondary sex characteristics and libido
Also anabolic
Builds muscle
Sertoli cells are
Sertoli cells
Produce small amounts of estrogens
Stimulated by FSH
These are also the support or ‘nurse’ cells for the maturing spermatids
Help shield the spermatids from attack by the body’s immune system
Vaginal tunic is and two layers
Double layered sleeve of peritoneum which lines the scrotum and inguinal canal
Very thin inner layer
Visceral vaginal tunic
Tightly adherent to the testes and spermatic cord
Difficult to see with the naked eye
Thick outer layer
Parietal vaginal tunic
Forms a fibrous sac around the testes and spermatic cord
Capsule of testes is called and does what
Beneath the tunics each testis is enclosed by a fibrous connective tissue capsule called the tunica albuginea (white tunic)
Protects and supports the soft contents of the testis
Continuous with the septae between seminiferous tubules
Testes descent into scrotum is and caused by
Testes begin development within the abdominal cavity near the kidneys
Move caudally (presumably under the influence of testosterone) into, and eventually through, the inguinal canal
Guided by a fibrous cord called the gubernaculum
Extends from the testis to the area of the skin that will become the scrotum.
The gubernaculum either fails to lengthen or actively shortens to draw the testes into the scrotum
As testis pass into the scrotum, they push out a tube of peritoneum
The vaginal tunic
When is testicular descent complete
Ruminants: prior to birth.
Pigs, just before birth
Horses: around the time of birth
K9 and feline: post-natal 10 d., up to 8 weeks.
Humans: prior to birth
Scrotum is and function
A sac of skin which houses the testes
Functions to thermoregulate and provide a favourable environment for production of sperm
Raises and lowers the testes via cremaster muscle. Depends on environmental temperature
Muscle relaxes and testes hang down if temperature is warm.
Spermatic cord is and function
The spermatic cord is the group of structures which extend from the testis through the inguinal canal
Includes blood and lymphatic vessels,nerves and the vas deferens
Link testes with rest of body
Blood vessels organized to provide cooling to arterial blood before it reaches testes
Called pampiniform plexus
Pampiniform plexus in the testes is and function
Complex of veins wrapping around the artery
Veins carry blood that is cooler than the arterial blood
Therefore, heat transfer occurs to cool arterial blood
Also warms the blood in the veins returning to the body
System is an example of a countercurrent exchange
Keeps the testes at a suitable temperature for spermatogenesis
Epididymis shape and function
An elongated organ which lies adjacent to the testes and receives immature sperm from the seminiferous tubules
Sperm enter through the efferent ducts
Efferent ducts unite to form the epididymal duct
The coiled epididymal duct is called the epididymis
The head of the epididymis attaches to the same end of the testis that the blood vessels and nerves enter
The body of the epididymis parallels the long axis of the testis
The tail of the epididymis continues as the ductus deferens which doubles back along the body of the epididymis to the region of the head, where it enters the spermatic cord
Spermatozoa are immature when they leave the testis and must undergo a period of maturation in the epididymis before they are ready for ejaculation.
Epididymis does what at ejaculation
At ejaculation, peristaltic contractions force sperm into the ductus deferens
The epididymal duct is LONG! Uncoiled, it varies from 2 meters (cat) to 75 meters (equine)
Ductus Deferens are and shape
A muscular tube
At ejaculation transports spermatozoa from the tail of the epididymis to the ejaculatory duct
Near the bladder the ductus deferens thickens to form the ampulla in some species
Ductus deferens leaves the tail of epididymis
Passes through the inguinal canal as part of the spermatic cord
At the internal inguinal ring turns caudally separating from the vascular and nervous parts of the cord
Each ductus deferens loops around a ureter as it continues past the bladder towards the urethra
Inguinal canal is
In abdominal wall
Extends from the deep inguinal ring to the superficial inguinal ring
Passageway for the external genitalia, blood vessels, lymphatic vessels, nerves, spermatic cord and superficial lymph nodes.
Accessory sex glands are
Include ampullae, vesicular glands (seminal vesicles) prostate gland and bulbourethral or cowpers glands
These glands produce the greater part of ejaculate or semen, which serves as a transport for spermatozoa, a nutrient source, and a buffer against excess acidity of female genital tract
They are closely associated with the pelvic urethra and differ among species
Know the prostate gland only.
Prostate gland is located in and produces
present in ALL domestic species.
It surrounds the pelvic urethra
Produces an alkaline secretion that helps give semen its characteristic odour
Penis function
Male organ of copulation
A highly specialized and complex organ
Surrounds the terminal part of the urethra and functions in both reproductive and urinary systems
Three ares of the penis
Glans or free extremity
Body or main portion
Two crura or roots which attach penis to pelvis
Types of penises
Depending on the relative amount of connective tissue present, penises may be classified as:
Fibroelastic (pigs and ruminants)
Musculocavernous (k9, feline and horse)
Fibroelastic penises, because of their connective tissue content, tend to be firm even when they are not erect
Penis of the dog
The dog is unique among domestic animals
Os penis
Bulb of the glans that causes dogs to ‘tie’ after mating
The tie occurs when the muscles of the vagina and vulva contract around the swollen bulb of the glans of the penis during copulation
Causes the male and female to be locked together for 15-20 minutes after breeding
Not painful
Seems to improve conception rates
Penis of the cat
Glans penis is covered with cornified, epithelial, proximally- projecting spines
Sigmoid flexure- Ruminant and pig shape and function
An “s-shaped” curve in the non-erect penis of the bull, ram, and boar
Since they have a fibroelastic penis, there is minimal enlargement during erection
Straightens instead
The penis extends through straightening of the sigmoid flexure during erection
Once erection is over, the retractor penis muscle pulls it back into normal resting shape
Pigs have a corkscrew penis to fit the corkscrew shape of the sow’s cervix
Erection is and caused by
Enlargement and stiffening of the penis
Parasympathetic reflex to sexual stimulation
Primarily pheromones in animals
Occurs when blood fills the penis due to:
Dilation of arteries
Compression of venous return
Compression occurs when contraction of the ischiocavernosus muscle presses the root of the penis against the brim of the pelvis
Ejaculation is caused by
Reflex expulsion of semen from the penis
Occurs in response to sexual stimulation and physical act of breeding
Two stages of ejaculation
Movement of spermatozoa and fluids from accessory reproductive glands to pelvic portion of the urethra
Bladder sphincter closes reflexively
Rhythmic contractions of urethra pump semen into female
Prepuce is
An invaginated fold of skin surrounding the free extremity of the penis
Aka: sheath, foreskin
The location of the “bean” in male horses.
External cremaster muscle does
External cremaster muscle- passes through the inguinal canal
Pulls the testes up against body, particularity in cold weather
Blood and nerve supply to the male reproductive organs
The testes’ blood supply is from the testicular artery, which branches directly from the aorta
The testicular vein parallels the course of the artery
Near the testis it is becomes convoluted
The nerve supply to the testis is chiefly via the autonomic nervous system
Retractor penis muscled does
following erection, the retractor penis muscles pull the penis back into the prepuce
Urethral muscle does
Surrounds pelvic portion of urethra, transports urine or seminal fluid distally by peristaltic action
Bulbospongiosus muscles do
Bulbospongiosus muscles - assist the urethral muscle in emptying the urethra by peristaltic contractions.
Ischiocavernosus muscles does
Ischiocavernosus muscles- when these contracts they pull the penis against the pelvis, aiding erection by shutting off venous drainage from the penis
