E2 Lec 12 - Reproduction

Viviparity

Live-birth, evolved in all vertebrate groups except birds.

Marsupial and Eutherian viviparity differences in:

• Estrous cycles

• Rates of embryogenesis

• Degree of placentation

• Hormonal sequences

• Environmental and behavioral cues

What are some reproductive characteristics often found in Marsupials?

• Pouch

• Epipubic Bones

Epipubic bone

Found in all marsupials, monotremes, and reptiles. Function is unclear.

Male Reproductive Anatomy

• Testes - produce sperm (gametes)

• Testosterone - hormone

Spermatogonia

Undergo cell division from diploid to haploid gametes, spermatozoa, in the testes during breeding season.

Where do gametes form exactly?

Seminiferous tubules

Epididymis

Storage and maturing location for gametes. They are transported from the seminiferous tubules.

Testes can be located abdominal or scrotal (T/F).

True. Descend into scrotum in most mammals, can be seasonal to produce more sperm.

Female Reproductive Anatomy basic characters

• Ovaries

• Oviduct

• Uterus

• Cervix

• Vagina

• Follicles

Ovaries

Primary reproductive organ. Pair of small oval bodies posterior to kidneys. Produce & mature gametes.

Oviduct

Channel from ova (eggs) to uterus.

Uterus

Site of embryonic development

Cervix

Connects the uterus to the vagina.

Vagina

Opening to exterior.

Follicle

Thick layer of spherically grouped cells under the surface of the ovary. Source of steroids, each contains a single egg, present in all eggs in females at birth. Follicles respond to hormones initiated egg maturing.

Monotreme reproductive anatomy

• Infundibulum - fertilization

• Urogential sinus - duct receiving both eggs and waste

• Ovaries large with yolk

• Cloaca - waste and reproductive hole

Marsupial reproductive anatomy

• Didelphous reproductive tract (uterus, cervix, vagina paired)

• Birth through Pseudovaginal canal

• Male forked penis

Placental

• Pair ovaries

• Single vagina

• Cervix and uterus may be paired

What are the different types of morphology in female placental reproductive tracts?

• Duplex

• Bipartite

• Bicornuate

• Simplex

Duplex Placental Uterine

• 2 uteri

• 2 cervix

• 1 vagina

Rodents

Bipartite Placental Uterine

• 2 uteri

• 1 cervix

• 1 vagina

carnivores, whales

Bicornuate Placental Uterine

• 2 uteri, fused into common chamber

• 1 cervix

• 1 vagina

bats, ungulates

Simplex Placental Uterine

• 1 uterus

• 1 cervix

• 1 vagina

primates

Monotremes (duplex without vagina)

Marsupials (duplex with two lateral vaginae and a median birth canal).

Placental Duplex (with a single vagina, rodents and rabbits).

Placental Bipartite (bipartite uterus seen in pigs, marine mammals, mice).

Placental Bicornuate (seen in bats, cows, horses)

Placental simplex (most higher primates)

Generalized sequence of events in reproduction include which 6 steps?

1.   Gametogenesis

2. Insemination/ovulation (release of egg) or ovulation/insemination

3. Fertilization

4. Implantation (endometrium)

5. In utero development

6. Parturition (birth)

What are the two cycles of reproduction?

• Ovarian - inside ovary

• Uterine - inside uterus

Ovarian cycle

• Development of ova in follicle

• Follicle bursts

• Ova released from ovary

• Passage of ova to uterus

Uterine cycle

Series of cyclic changes in the uterus. Changes result in periods of heightened sexual receptivity (estrus or heat).

What are two types of uterine cycles in mammals?

• Estrus cycle

• Menstrual cycle

Estrous cycle

cyclical pattern of ovarian activity that facilitates female animals to go from a period of reproductive receptivity to non-receptivity ultimately allowing the establishment of pregnancy following mating. Endometrium, uterine lining, is reabsorbed if conception does not occur.

What are four phases of the estrous cycle?

• Proestrus

• Estrus

• Metestrus

• Diestrus

• (Anestrus)

Menstrual cycle

Endometrium is shed at menstruation instead of being reabsorbed. No discrete phases.

Both the estrous and menstrual cycle of mammals is regulated by …

Hormones

What are major hormones in reproduction?

• Estrogen - trigger ovulation

• Progesterone - hormone of pregnancy

• Follicle Stimulation Hormone (FSH) - stimulate testes/ovaries

• Luteinizing hormone (LH) - stimulate testes/ovaries

What are organs create hormones important for reproduction?

• Anterior Pituitary Gland - FSH & LH

• Ovary - estorgen

• Corpus luteum - progesterone

Proestrus

• Growth of follicle (FSH)

• Secretion of estrodial (estrogen)

Estrus

• Ovulation (egg release) with high estrogen

• Surge of LH

• Ruptured follicle develops to corpus luteum

• Spontaneous or induced ovulation initiates the process

Metestrus

• Presence of corpus luteum

• LH produced, maintains corpus luteum

• Corpus luteum secretes progesterone

• Progesterone prepared uterine lining (endometrium) for blastocyst implantation

• If fertilization does not occur - corpus luteum regresses

• If fertilization and implantation occur, progesterone continues to be secreted.

Diestrus

Leveling out of hormones

What are variation in estrous cycles found in mammals?

• Monstrous (60%)

• Polyestrous (40%)

Monestrous

Single estrous cycle

Polyestrous

Multiple estrous cycles

Which hormones are important in the Menstrual cycle?

• Follicle stimulating hormone (FSH)

• Luteinizing hormone (LH)

• Estrogen

• Progesterone

In what orders is the menstrual cycle seen?

• Primates

• Some bats

• Elephant shrews

• One rodent

The menstrual cycle is dependent/independent from the Estrous cycle.

independent

The menstrual cycle has no distinct phases but a cycle of …

hormones

What is the common hormone cycle for menstruation?

• Anterior pituitary releases FSH, stimulating follicular growth in ovary and release of estrogen.

• High estrogen levels (and FSH, LH) results in ovulation

• Uterine lining development (endometrium)

• Corpus luteum produces progesterone

How is the estrous cycle monitored be most females?

Restrict copulations for reproduction to specific time. Hormones and nervous system control periods of reproduction which are regulated by environmental cues.

How is the menstrual cycle monitored be most females?

Gradual increase and decrease of hormones, no discrete time or phases.

How is the stimulation of spermatogenesis initiated?

Anterior pituitary produces FSH and LH which stimulate the testes to produce testosterone. Testosterone promotes more production of FSH and LH in a negative feedback cycle, and stimulates growth of male secondary sexual characteristics and production of semen.