Structures Testes- Male gonad that produces both testosterone and germ cells (which become sperm). Contained in the scrotum. Scrotum- pouch containing the testicles and epididymis. Seminiferous Tubules- Hollow structures where germ cells differentiate into spermatozoa.
Structures Epididymis- Structure adjacent to the testicle. 3 parts: head, body, and tail. Spermatozoa mature in the head and body of the epididymis. Ductus Deferens (Vas Deferens)- The continuation of the epididymal duct at the tail of the epididymis. It travels up the spermatic cord and through the inguinal canal to reach the abdomen.
Structures The Spermatic Cord consists of- Vas deferens Testicular artery, vein, nerve, and lymphatics
Accessory Sex Glands Prostate Seminal vesicles Bulbourethral glands
Penis The male copulatory organ. Provides a passage way for semen and urine to the outside of the body. Prepuce- the cutaneous sheath around the free part of the penis when it is not erect. Preputial Orifice- the external opening of the prepuce to the outside environment.
Penis Contains the glans penis (head of the penis) Bulbus Glandis- the caudal part of the penis. Swells to lock the male into the female during copulation. +/- Os penis
Testosterone Produced by the testes. Responsible for secondary sex characteristics and sex drive. An androgen or anabolic steroid. Production is stimulated by LH.
Sperm Spermatogenesis is stimulated by FSH. Head- Contains the nucleus and haploid chromosomes. Acrosome- a “cap” which contains enzymes to permit penetration into the ovum. Midpiece- “Power plant” Numerous mitochondria carry-out metabolism that provides ATP for sperm locomotion. Tail- consists of flagellum for propulsion.
Seminal Fluid Produced by accessory sex organs. The medium for survival of the sperm. Prostatic secretion- alkalinizes the vaginal environment to prevent sperm death.
Prostatic Disease Common in dogs Benign Prostatic Hyperplasia Prostatic adenocarcinoma Bacterial All cause enlargement or inflammation
Orchitis & Epididymitis Acute- Caused by trauma, infection, or testicular torsion Chronic- Immune-mediated or neoplastic Testicular atrophy and fibrosis
Phimosis The inability to extrude the penis through an abnormally small preputial orifice Congenital or it develops due to inflammation, neoplasia, edema, or fibrosis after trauma, irritation or infection
Paraphimosis The inability to completely retract the penis Usually occurs after an erection The preputial orifice skin becomes inverted and impairs venous drainage A medical emergency!!!
Pathologies… Inguinal Hernia- The protrusion of a loop of organ or tissue through the inguinal canal. Cryptorchidism- Failure of one or both testicles to descend into the scrotum. The retained testicle can be anywhere between the scrotum and the caudal pole of the kidney.
Structures Ovaries Oviducts (uterine tubes) Uterus- horns and body Cervix- a heavy, smooth muscle sphincter that is kept tightly closed except during estrus and parturition. Vagina- glandless mucosa located within the pelvic canal. Vulva- consists of the vestibule and labia.
Ovaries Ovaries- both endocrine (hormone producing) and cytogenic (cell producing). Medulla- vascular center of the ovary. Cortex- where follicles can be found, both developing and atrophying. Functions- To produce ova or eggs ready for fertilization. Acts as an endocrine gland.
Oviducts Oviduct- the open end of the uterine tube (fallopian tube) Functions- Collects ova as they are released. Conveys ova from the ovaries to the uterine horns. Infundibulum- funnel-shaped ovarian end of the oviduct.
Uterus Highly expandable, tubular organ where the embryo/fetus develops. A hollow structure with 3 parts- neck (where the cervix is located), body, and horns. Function- Provides a receptacle for embryos to develop. Provides nutrients via the PLACENTA.
Vagina The part of the reproductive tract between the cervix and the vulva. Along with the vestibule and vulva, it is the females copulatory organ and birth canal. The hymen is the poorly developed, vestigial, mucosal folds at the junction of the vagina and vestibule.
Other Structures… Vulva- the external orifice that terminates the genital tract. Labia- the Ⓡ and Ⓛ lips of the vulva.
Types Monestrous- usually one cycle per year, usually seasonal breeders. (mink) Polyestrous- more than one cycle per year, continuous. (swine) Seasonally Polyestrous- cycles continuously in specific seasons. Induced Ovulators- requires copulation to ovulate. Spontaneous Ovulators- ovulation occurs naturally, with or without copulation.
Estrous Cycle The onset of the estrous cycle begins at puberty. The purpose is to prepare the uterus to receive fertilized ovum. Sexual maturity brings about- ovarian development, which includes the production of ova, ovulation, and the production of the corpus luteum. The estrous cycle is under the control of hormones produced by the ovaries and the pituitary gland. Animals do not undergo menopause.
Estrous Cycle At the beginning of each cycle, ova within the follicles in the ovaries begin to develop. One or more follicles (depending on the species) continue to develop until they reach a ripened follicle One or more follicles rupture, (ovulation, usually occurs during estrus.) Then the ovum is expelled from the ovary to the oviduct (uterine tube).
Estrous Cycle The ruptured follicle grows larger, filling with a yellow, lipoid material and becomes the CORPUS LUTEUM (“yellow body”). The corpus luteum secretes progesterone. If fertilization occurs, the corpus luteum continues to secrete progesterone and prevents future estrous cycles during pregnancy.
Estrous Cycle Without fertilization, the corpus luteum and its secretions diminish, forming a CORPUS ALBICANS (“white body”). The reduced levels of hormone production lead to a new estrous cycle.
1. Proestrus Period of preparation. **FSH & LH cause the development of the follicle. The follicle starts producing ESTROGEN. Estrogen stimulates the vagina and uterus for copulation and pregnancy.
2. Estrus Period of female sexual receptivity. Uterus and uterine horns are ready to receive an embryo. Release of LH causes ovulation. Dogs may have bloody discharge, cats may exhibit behavioral changes.
3. Diestrus & Metestrus Post-ovulating phase. Each ruptured follicle develops into a corpus luteum (CL). The CL starts to secrete PROGESTERONE which inhibits the development of new follicles. The CL is also responsible for maintaining the uterine lining to support the fetus during pregnancy.
3. Diestrus & Metestrus If pregnancy does not occur, the CL degenerates. If pregnancy occurs, the corpus luteum is maintained and continues to secrete hormones for: The entire pregnancy or, Until the placenta develops. Depends on the species.
4. Anestrus Periods of no estrous cycles a. Pregnancy b. Nursing c. Season of year d. Poor Nutrition e. Pathological Conditions
Gestation Periods **Dog- Pig- 57-63 days 114 days **Cat- Sheep & Goats- 65 days 150 days Horse- Mice- 330 days 19-21 days Cow- Rats- 283 days 21-23 days Rabbits- Hamsters- 30-33 days 15-18 days Guinea pigs- Gerbils- 59-72 days 23-26 days
Terms Gestation- the interval between fertilization of the ovum and the birth of the offspring. Mitosis- cell division, one cell divides into 2, 2 into 4… Zygote- fertilized ovum Embryo- stage at which major organs are developing. Fetus- stage where formation of major internal and external structures is complete until the time of parturition.
Fertilization & Cell Division Ova enter the infundibulum and are transported down by muscular contractions. Sperm travels up the female tract and fertilization takes place in the upper part of the uterine tube. Each ovum is penetrated by one sperm which results in a fertilization reaction (preventing fertilization by any other sperm). The fertilized ovum is now a zygote, and cell division begins via mitosis.
The Placenta A membranous structure that obtains nutrients and oxygen from the mother to deliver to the fetus. Attaches to the endometrial lining of the uterus. Chorion- outer layer in contact with the maternal uterus. Amnion- innermost membrane closest to the fetus. Amnionic Sac- sac in which the fetus is located.
Hormones Oxytocin- **Produced by the Posterior pituitary Stimulates milk let-down. In the presence of Estrogen, it stimulates uterine contractions during parturition. Stimulates the oviducts to help move spermatozoa.
Hormones Prolactin- **From the Anterior pituitary Helps maintain the CL during pregnancy. Stimulates the mammary glands to fill with milk at parturition. Stimulates the replenishment of milk via neonatal suckling.
Uterine Infection Infection of the uterus. Endometritis- inflammation of the endometrium. Metritis- inflammation of all layers. Pyometra- accumulation of pus in the uterus.
Pyometra A hormonally mediated disorder. An abnormal uterine endometrium combined with a secondary bacterial infection. Often occurs when progestational compounds are administered to delay or suppress estrus.
Uterine Prolapse The turning inside-out of the uterus and vagina causing it to project through the vulva. Most common in the cow and sow. The prolapsed uterus can often be pushed back in and sutured in place until it heals.
Pseudocyesis False pregnancy Common in dogs Occurs at the end of diestrus, characterized by hyperplasia of the mammary glands, lactation, and behavioral changes Falling progesterone and increasing prolactin are believed to be the cause
LABORATORY ANALYSIS VAGINAL CYTOLOGY Hendrix p. 327
Anestrus Predominantly non-cornified squamous epithelial cells Lg nucleus and rounded edges
Proestrus Above- early proestrus, below- late proestrus Cornified squamous epithelial cells Angular with jagged borders Segs(neutraphils) decrease, RBC’s increase
Estrus All squamous cells are cornified Segs- absent, RBC’s present
Diestrus Non-cornified squamous and abundant cytologic debris Segs increase, RBC’s are absent Similar to anestrus