VMT Exam 1

1. Female Reproductive System

The female reproductive system is primarily responsible for producing ova (eggs) and providing an environment for fertilization and fetal development. Key components include:

  • Ovaries: Produce and release eggs (oogenesis) and female sex hormones (estrogen and progesterone). (Ovulation occurs when the egg is released)

  • Fallopian Tubes (Oviducts): Transport eggs from the ovaries to the uterus; site of fertilization.

  • Uterus: A muscular organ where a fertilized egg implants and develops.

  • Cervix: The lower, narrow part of the uterus that connects to the vagina (sphincter, can relax and contract). Open for mating and birth. Closed for pregnancy

  • Vagina: A muscular canal that connects the uterus to the outside of the body; serves as the birth canal and for intercourse.

1.1 Pregnancy Hormonal

It takes 3-5 days for a zygote to move from the ovaduct to the uterus.

  1. Fertilization occurs (pregnant)

        CL Persists: In some species the persist the whole gestation     (Cows, pigs, goats, dogs)

        Other species: The placenta takes over progesterone     production (Humans, Horses, Sheep, Goats)

  2. No Fertilization: Corpus Luteum regresses, Progesterone decreases, Follicule Stimulating Hormone increases

  3. Pseudo pregnancy: No fertilization, Corpus Luteum persists and progesterone increases

2. Male Reproductive System

The male reproductive system is responsible for producing sperm (spermatogenesis) and delivering it for fertilization. Key components include:

  • Testes: Produce sperm and male sex hormones (androgens, primarily testosterone).

  • Epididymis: Stores and matures sperm (some species have an ampulla where sperm can be temporarily stored before ejaculation).

  • Ampulla: Animals that have an ampulla are known as fast ejaculators (Stallions, Bulls, Rams, Bucks)

  • Vas Deferens: Tube that runs from the epididymis to the urethra

  • Seminal Vesicles and Prostate Gland: Produce seminal fluid, which nourishes and transports sperm.

  • Urethra: Carries both urine and semen out of the body.

  • Penis: The external organ for sexual intercourse and urine excretion.

    • Vascular: Erection occurs when tissue of the penis becomes engorged with blood (Stallions, dogs, cats)

    • Fibroelastic: Sigmoid flexure, an S shaped muscle when aroused, relaxes and becomes straight (Bulls, Rams, Boars)

3. Hormonal Involvement

Hormones play a crucial role in regulating both male and female reproductive functions.

3.1. Female Hormones

  • Estrogen: Primarily produced by the ovaries. Responsible for the development of female secondary sexual characteristics, thickening of the uterine lining (endometrium), and regulating the menstrual cycle.

  • Progesterone: Primarily produced by the corpus luteum (after ovulation). Prepares the uterus for pregnancy, maintains pregnancy, and inhibits the release of GnRH, FSH, and LH during pregnancy.

  • Follicle-Stimulating Hormone (FSH): Produced by the anterior pituitary. Stimulates ovarian follicle growth and estrogen production.(Ovarian follicule growth, egg migrates)

  • Luteinizing Hormone (LH): Produced by the anterior pituitary. Triggers ovulation and stimulates the formation of the corpus luteum, which produces progesterone.

  • Corpus Luteum: A temporary endocrine structure that forms from the ovarian follicle after ovulation and produces progesterone, critical for maintaining pregnancy. (C.L body or Yellow Body)

  • Gonadotropin-Releasing Hormone (GnRH): Produced by the hypothalamus. Stimulates the anterior pituitary to release FSH and LH.

3.2. Male Hormones

  • Testosterone: Primarily produced by the testes. Responsible for the development of male secondary sexual characteristics, sperm production, and libido.

  • FSH: Stimulates sperm production (spermatogenesis) in the testes.

  • LH: Also known as Interstitial Cell-Stimulating Hormone (ICSH) in males. Stimulates Leydig cells in the testes to produce testosterone.

  • GnRH: Stimulates the anterior pituitary to release FSH and LH.

4. Variations in Animal Species

The basic structures and hormonal controls of reproduction are broadly conserved across vertebrates, but significant variations exist.

4.1. Reproductive Strategies

  • Monogamy vs. Polygamy: Different mating systems influence reproductive anatomy and physiology.

  • Internal vs. External Fertilization: Most terrestrial animals use internal fertilization

4.2. Ovarian Cycles

  • Estrous Cycle (Most mammals): Characterized by periods of sexual receptivity (estrus or 'heat') when females are fertile. No endometrial shedding. Variations include:

    • Proestrus: Period leading up to estrus, characterized by Graaphian follicule development and increasing estrogen levels.

    • Estrus: The period of sexual receptivity ('heat'), when the female is fertile and receptive to mating. Ovulation typically occurs during or shortly after estrus (after the graaphian follicole ruptures)

    • Metestrus: Follows estrus, characterized by the formation of the corpus luteum and increasing progesterone levels. The uterus prepares for potential pregnancy.

    • Diestrus: A short break of inactivity between cycles

    • Anestrus: A lage break of inactivity between cycles

    • Monoestrous: One estrous cycle per year (e.g., dogs).

    • Polyestrous: Multiple estrous cycles per year (e.g., humans, cows).

    • Seasonal Polyestrous: Multiple cycles within certain seasons (e.g., horses, sheep, goats, cats).

4.3. Testicular Descent

  • In many mammals (e.g., humans, most carnivores), testes descend into a scrotum to maintain a cooler temperature necessary for spermatogenesis.

  • Penile covering: large animals is known as sheath and small animals known as prepuse.

4.4. Accessory Sex Glands

  • Seminal Vesicals: These glands secrete a fluid that nourishes and helps transport sperm during ejaculation, contributing significantly to the volume of semen.

  • Bulbourethral glands: Also known as Cowper's glands, these are responsible for producing a pre-ejaculatory fluid that lubricates the urethra and neutralizes any acidity, preparing the passage for sperm.

  • Prostate Gland: The prostate gland secretes a milky fluid that enhances sperm motility and viability, further contributing to the overall composition of semen.

5. Specific Problems

  • Phinmosis: The opening in the prepuse is too narrow and the penis cannot come out

  • Paraphimosis: The penis is able to come out but the opening of the prepuse is too small and it cannot go back in.

  • Pyometra: Infection of the uterus, progesterone related- changes in endomtrium. Clinical signs, discharge, lethargy, high white blood cell count, abdominal pain. This can be life threatening

  • Tubular pregnancy(ectopic pregnancy): The egg doesn’t drop from the ovaduct to the uterus.

  • Dystocia: Difficult or abnormal birth

  • Uterine Exhaustion: Oxytocin wore off

  • Abnormal position: Generally in animals with 1-2 offspring

  • Abnormally large fetus

  • Small pelvic opening: Younger females

  • Crytorchidism: Testi doesn’t descend into scrotum)

4.5. Uterine Morphology and Litter Size

  • Animals that typically have litters (dogs, cats, pigs) are characterized by long uterine horns and a slender uterine body.

  • Animals that usually have 1-2 offspring (cows, sheep, goats) typically have short uterine horns and a broad uterine body.

4.6 Pregnancy Anatomically

  • Gestation: Conception to birth (Parturition)

  • Implantation: Occurs when the fertilized egg attaches itself to the uterine wall, allowing for the exchange of nutrients and waste between the mother and developing fetus.

    • Sheep 10-18 days

    • Cows 30 days

    • Horse 60 days

  • Placental attachment types:

    1. Localized attachment : This type of placental attachment involves a specific area where the placenta attaches to the uterus. (Ruminants: cattle, sheep, goats)

    2. Diffuse: Contact around whole uterine wall. (Horses and Pigs)

    3. Zonary- Zone or band of attachment that encircles the placenta in a belt-like manner. (dogs and cats)

  • Parturition (birth):

    • Fetus releases cortisol (Natural steroid)

    • Cortisol triggers the release of prostaglandin from the mother. (PGF2a)

    • Prostaglandin kills the corpus lutem which causes the decrease in progesterone levels, and an increase in estrogen.

  • Estrogen enhances:

    1. Oxytocin: Uterine contractions and milk releases into the utter (milk letdown)

    2. Relaxin: Cervix relaxation/dilation, which facilitates childbirth by allowing the baby to pass through the birth canal more easily.