Reproductive System

VTT 235/245

MALE ANATOMY

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

MALE PHYSIOLOGY

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.

MALE PATHOLOGY

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.

FEMALE ANATOMY

Structures

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.

Uterus

Uterine Walls- 3 layers

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.

FEMALE PHYSIOLOGY

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.

Stages of the 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

PREGNANCY

Gestation Periods **Dog-

57-63 days **Cat-

65 days Horse-

330 days Cow-

283 days Rabbits-

30-33 days Guinea pigs-

59-72 days

Pig- 114 days

Sheep & Goats- 150 days

Mice- 19-21 days

Rats- 21-23 days

Hamsters- 15-18 days

Gerbils- 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.

FEMALE PATHOLOGY

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 CYTOLOGYHendrix 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

LABORATORY ANALYSIS

SEMEN ANALYSIS

Semen Collection

Semen Analysis

Sample Handling- Avoid exposure to marked changes

in temperature Supplies-

Slides, coverslips, pipettes, stains and diluents

Semen Analysis

Evaluation- Volume Appearance Motility Concentration Live:Dead Ratio

Morphology- Head Midpiece Tail

Primary Abnormalities

Primary Abnormalities

Secondary Abnormalities

Semen Analysis

The End!!