AGR Veterinary Science Animal Reproduction Objectives Be able to properly List the male and female reproductive tracts Describe the functions of each of the parts of the reproductive tracts. Properly describe the processes of reproduction starting with the hormones Cow Reproductive Tract Ovary Infundibulum Oviduct Uterine horn Uterus Cervix Vagina Vulva Canine Female Repro Tract Sow Reproductive Tract Bull Reproductive Tract Testis Epididymis Vas deferens Seminal vesicles Prostate Cowper’s gland Urethra Penis Boar Reproductive Tract Repro Basics Coordinated effort between the endocrine system and the reproductive physiology and anatomic body parts of the male and female. Coordination consists of: germ cell development and maintenance, fertilization of egg by sperm, pregnancy, and parturition. Reproduction Endocrinology Hypothalamus gland begins the reproductive endocrinology. Located at the base of the brain. Releases gonadotropin releasing hormone (GnRH). GnRH is released in a pulsating manner to the anterior pituitary gland. GnRh release is triggered by environmental factors, i.e. night length, temperature, presence of the opposite sex. Anterior Pituitary Gland Located just below the hypothalamus gland. Receives GnRH and responds by releasing Luteinizing hormone (LH) Follicle-stimulating hormone (FSH) LH and FSH enter the blood stream and travel to the testes (male) and ovary (female) all so in a pulsating manner. Testosterone Male sex hormone produced by the testes. LH provides the testes the signal to produce testosterone. Testosterone is necessary for the production of the secondary sex characteristics in the male. Sperm production is a function of the testes as a result of the influence of the FSH. Ovary Activity FSH is responsible for the growth and maintenance of the follicle on the ovary. Singular birth, twins or triples, and multiple births like litters are a result of the development of one or more follicles specific to different species. Estrogen Estrogen is produced by the follicle. Estrogen surge stimulates the pituitary gland to release LH which leads to the breakdown of the follicle wall and an ova (egg) is expelled from the follicle. The process of ova being released from the follicle is called ovulation. Ovulation The released ova is captured or caught by the infundibulum of the reproductive tract. The infundibulum directs the egg into the oviduct of the tract. The top is of a cow and the lower is of a sow. Hormonal Activity After Ovulation The follicle after ovulation turns into a corpus luteum (CL). Appears or feels like a hollowed cavity on the surface of the follicle on the ovary. Early pregnancy checking by palpation in larger animals involves checking for the CL on the ovary. CL produces the hormone, progesterone. Progesterone Progesterone from the CL is the pregnancy maintenance hormone during early pregnancy (cow, mare, ewe). Required by goats, rabbits and sows throughout pregnancy. Inhibits the release of LH and FSH. Prevents the estrus signs. Placenta provides progesterone to maintain pregnancy during the later stages of pregnancy. Placenta surrounds the fetus and is attached to the uterine wall of the female. Oxygen and nutrients pass to the fetus from the female with waste passing to the female Hormonal Activity During the Estrus Cycle The Estrus Cycle Length of the estrus cycle is species specific Cattle 18 – 24 days Swine 18 – 24 days Sheep 14 – 20 days Horses 16 – 30 days Goats 15 – 24 days Dogs 3 ½ - 13 months Cats 14 – 21 days Length of Estrus Estrus by species Cattle – 14 hrs Swine – 2-3 days Sheep – 30-35 hrs Horses – 6 days Goats – 42 hrs Dogs – 6-12 days Cats – 6-7 days Timing of Ovulation Compared To Signs of Estrus (Heat) Timing by species Cattle - 10-14 hrs after end Swine - 18-60 after beginning Sheep - 1 hr before the end Horses - 1-2 days before the end Goats - near the end Dogs - 1-3 days after acceptance of male Cats - Stimulated by mating Signs of Estrus By Females Stands to be mounted Frequent urination General nervousness Anatomy of the Female Tract Ovaries Occurs in pairs Responsible for the storage, development, and release of ova. Produces progesterone and estrogen Produces multiple follicles each estrus cycle from which one or more develop to ova depending on the species. LH responsible for release of ova. Infundibulum Thin funnel shaped membrane which captures the expelled ova from the ovary. Prevents the ova from entering the abdominal cavity and directs the ova into the oviduct. Anatomy Cont’d Oviducts or Fallopian Tubes The three sections of the oviduct Infundibulum Ampulla Isthmus Site of the fertilization of the ova by the sperm cell. Most fertilization occurs in the ampulla. The oviduct provides nutrients and a transportation medium from the secretions for the ova. Eggs remain in the oviduct from 3-6 days. Anatomy Cont’d Uterine horns and uterus Shape and configuration from oviduct to uterus differs between species. Uterus provides a passageway up and through for sperm cells swimming up the tract. Provides glandular secretions for the embryo prior to implantation into the uterine wall and formation of the placenta lining the wall. Provides for the elimination of waste products from the developing fetus. Through muscular contractions of the uterus during parturition, the fetus is expelled from the female. Anatomy of the Uterus Cont’d A corpus luteum (CL)is formed from the follicle which expels the egg. The CL produces progesterone to reduces contraction of the uterus which allows for the embryo to attach itself to the thickening placenta along the uterine wall. Anatomy Cont’d The cervix is the intermediary structure between the uterus and vagina. 5 primary functions A passageway for sperm cells Serves as a storage reservoir for sperm cells for a uniform distribution over time into the uterus. Serves as a primary barrier (a mucus plug or cervical plug is formed) between external and internal environments. To provide lubrication through secretions which in turn flush the vagina of contaminants. Serves as a passageway for the fetus during parturition. Anatomy Cont’d Vagina Main copulatory organ of most species (swine are excluded). Has a well developed mucus layer. Connects cervix to vulva Vulva Exterior organ to the female tract. Appearance is an indicator of extrus or the onset of parturition. Anatomy of the Male Tract Testes Counter structure in the male versus the ovaries in the female. Produces sperm cells and testosterone. Held in place by the spermatic cord within the scrotum. Maintains the temperature of the testes 4-6 degree’s C below body temp. Contracts and expands to warm or cool. Contains the blood vesscles Anatomy of Male Cont’d Sperm cells are continuously produced by the seminiferous tubules of the testes. Sperm migrate to the epididymis for development (maturation), storage, and transport. The most mature sperm are found in the tail of the epididymis as opposed to the head. Prior to ejaculation, sperm cells move out of the epididymis to the vas deferens and the urethra. Anatomy of the Male Cont’d Sperm cells are suspended in fluid from the testes, but the semen portion of the ejaculate is provided by 3 secondary sex glands. Seminal vesicles Prostate Bulbourethral glands (Cowpers gland) Anatomy of the Male Cont’d Secondary sex glands: Produce the volume of the semen Add nutrients Provide cleansing agents for the urethra Aid in coagulation of the semen after ejaculation Produce a gelatinous fraction which seals the cervix after breeding to prevent semen loss through the vagina. Anatomy of the Male Cont’d Penis Vascular (enlarges during sexual excitement by retaining blood in the erectile tissue. Erections occur due to increased blood volume under high pressure. Following ejaculation, blood leaves the organ and the erection subsides. Horses are example of a vascular penis. Fibroelastic (penis exists in a S-shaped configuration inside the body cavity until sexual excitement) Sigmoid flexure muscle extends the penis Retractor muscle is responsible for returning penis to the body cavity. Bulls, boars, and rams have a fibroelastic penis’ Pregnancy or Gestation Zygotes are formed from the union of sperm cell and egg cell. Embryos are formed when zygotes begin to carry on mitosis or cell replication. Embryo implantation into the uterine wall lining or the placenta 14 to 40 days after fertilization. 2/3 of fetal growth takes place in the last 1/3 of gestation. Hormonal Activity of Pregnancy Corpus luteum supplies large amounts of progesterone to maintain the pregnancy. Progesterone from the placenta prevents the degradation of the CL. Fetal Membranes of the Placenta Amnion Chorion & allantois Contains a fluid which protects and cushions the fetus. In contact with the endometrium of the uterus. Yolk sac Nutrients to the embryo and early fetus. Activities of the Placenta Regulates the exchange of oxygen Nutrients to the fetus Waste materials away from the fetus Antibodies between the fetus and mother More connection between placenta and uterus in ruminants than swine Gestation Rates in Days Cattle – 283 Swine – 113 Sheep – 150 Horses – 336 Goats – 151 Dogs – 63 Parturition or Birth Initiated by hormones secreted by the offspring. Oxytocin from the posterior pituitary gland travels to the muscles of the uterus to cause contractions. Pressure against the cervix will neurologically message the pituitary. Fluids from the fetal membranes will lubricate the cervix and vagina for ease of offspring passage. The final phase of parturition is the expulsion of the fetal membranes or afterbirth.