ANS 150 Exam 2 NCSU

Ovary

Contains thousands of growing follicles

Each follicle contains an ovum or"egg"

Receives a rich supply of both blood vessels and nerves

Follicles

-grow in response to hormones called gonadotropins

-either die (become atretic) or ovulate and release their egg.

Corpus Luteum (CL)

-form from the tissue that remains after a follicle has ovulated

-produce a number of hormones associated with pregnancy

-progesterone is its (their) primary product

Corpus Albicans (CA)

-scar tissue left behind after corpus luteum dies or regresses

-avascular, non-functional tissue

Oviduct

Funnel shaped organ

• Specialized end near ovary called the fimbria

• Fimbria picks up ovulated eggs

-Anterior end called ampulla

-Posterior end called isthmus

-Fertilization and early embryonic development takes place in the oviduct in most animals

Uterus

Glandular inner lining surrounded by two layers of muscle

Longitudinal and circular layers

Responsible for maintenance of pregnancy

Also releases the hormone that regresses luteal tissue

Cervix

Thick, muscular organ

Serves to isolate the uterus from external environment during pregnancy

site of semen deposition in some animals

Vulva

External female genitalia

Outer portion of the vagina

Involved with recognition of receptivity and possibly with the production of female pheromones

Testicle

Series of tubules (seminiferous tubules)

Produce spermatozoa

Produce hormones (testosterone, androgens and others).

Epididymis

continuation of tubule in testicle

specialized for maturation and storage of spermatozoa

immature sperm enter epididymis

during their passage through epididymis they become mature

Secondary sex glands

Seminal vesicles, prostate and bulbourethral glands

Produce and secrete most of the liquid portion of semen

Composition of each is fairly specialized

Penis

Male reproductive organ

Specialized to deposit semen in female reproductive tract

central canal is the urethra

urethra is common exit for reproductive and urinary systems

Sheath

specialized pouch in which penis remains when not in use

in some animals, the lining of the sheath is involved in male pheromone production.

Female endocrinology

gonadotropins - stimulate ovary

sex steroids/prostaglandins - direct control of reproductive state

mammotropins - involved with lactation

Gonadotropins (LH)

Luteinizing hormone (LH)

- produced by the pituitary gland

- stimulates final growth of follicles

- causes ovulation

- also stimulates corpus luteum

Gonadotropins (FSH)

Follicle stimulating hormone (FSH)

- produced by the pituitary gland

- stimulates all stages of follicle growth, especially early periods

sex steroids/prostaglandins (Progesterone)

Progesterone

- produced by corpus luteum and the placenta (some animals)

- responsible for maintenance of pregnancy

- inhibits gonadotropin secretion

sex steroids/prostaglandins cont (Estrogen)

Estrogen (estradiol 17beta)

- produced by growing follicles, placenta and embryos

- has both positive and negative effects on gonadotropins

Estrogen (cont.)

- stimulates pre-ovulatory surge of gonadotropins

- prepares female for breeding and parturition

- responsible for female mating behaviors

sex steroids/prostaglandins cont (Prostaglandin)

Prostaglandin F2alpha

- primarily the uterus in the reproductive system

- responsible for luteal regression

- causes uterine contractions at birth

Mammotropins

Prolactin

- produced in the pituitary

- stimulates production of milk

Oxytocin

- produced by uterus and hypothalamus

- stimulates milk excretion

- stimulates uterine contractions

Reproductive Cycle (Stages)

Puberty

Estrous Cycles

Pregnancy (Gestation)

Lactation

Post-partum period (Rebreeding)

puberty

Puberty is generally defined as the age at which an animal is capable of adult reproductive function

Females - estrus, production of fertile eggs and maintenance of pregnancy

Males - libido, mating and production of fertile sperm

In most animals, it is the brain and production of gonadotropins, specifically LH that is the last function to mature during puberty

Ovaries and testes are capable of gamete and hormone production before puberty is reached

Estrous Cycle

repeatable sequence of events that results in female becoming sexually receptive

Estrous Cycle stages

-Begins with estrus (period of sexual receptivity)

-At estrus, estrogen is high and progesterone is low

-High estrogen causes preovulatory surge of gonadotropins

-LH surge causes ovulation

-Follicles release eggs

-Estrogen decreases

-Corpora lutea (corpus luteum) form

-Progesterone is produced from CL

-Gonadotropin secretion is decreased because of progesterone

-Progesterone and CL are maintained for 12 to 16 days

-Prostaglandin is released from non- pregnant uterus

-Corpora lutea are destroyed

-Progesterone decreases

-LH and FSH increase

-Follicles grow

-Estrogen increases

-At certain level of estrogens, females exhibit estrus and then ovulate

Pregnancy

-After ovulation, fertilization occurs and embryonic development occurs

-In most females, their bodies do not realize that they are pregnant until around 12 days after fertilization

-At day 12 embryo sends a signal to mother

-prostaglandins are not released from the uterus

-progesterone is maintained

-Embryo begins to differentiate

After embryo begins to differentiate and when it begins to take the shape and form of a young animal it is referred to as a fetus.

Fetuses are still differentiating, but they also are increasing in size very rapidly.

In the blastocys,

-inner cell mass become fetus proper

-cells within inner cell mass differentiate into bones, muscle, nerves, etc.

-trophoblast becomes placental membranes of fetus

parturition (birth process)

fetus initiates parturition

prostaglandins are released

progesterone decreases (except in the horse where it increases then decreases)

endocrine changes vary among species considerably

Lactation

neural reflex arc

physical stimulation of nipple during nursing causes prolactin and oxytocin release

prolactin - milk synthesis

oxytocin - milk ejection

Rebreeding

Suckling action of young prevents release of LH and FSH (via another reflex arc)

Once suckling is terminated by weaning or decreases in intensity, then LH and FSH increase and estrus results.

The one exception is the mare.

Male endocrinology

FSH and LH stimulate sperm production (spermatogenesis)

FSH and LH stimulate testosterone production (mostly LH)

process is fairly continuous, at least during the breeding season