Exam 2: Puberty Flashcards
What is puberty
Capacity to achieve reproduction successfully
Occurs over time, not a single event
Markers of puberty in females
First estrus
First ovulation
First menstruation (humans and primates)
Can support pregnancy without deleterious effects
Vaginal opening (rodents)
Markers of puberty in males
Age when behavioral traits expressed
Age when sperm in first appears in ejaculate
Age of sperm in urine
Age when ejaculate contains threshold number of sperm
Steps of puberty
1) Maturation of genital organs
2) Development of sexual characteristics
3) Occurrence of first estrus/ovulation or ejaculations
Development of male gonads
-Almost all post natal growth of testes takes place during puberty
-Seminiferous tubules increase in length and curl up
-Development of seminiferous epithelium: differentiation of sertoli cells and multiplication of spermatogonia
-Leydig cells differentiate when the mitotic activity is
initiated in the spermatogonia
-Production of spermatozoa in mid puberty
When do most mammals reach capacity fot reproduction
When animal reaches 30-70% of adult weight
(Humans 80-90%)
Major factor that limits pubertal onset
Hypothalamus’s failure to produce GnRH to induce gonadotropin release
Development of male hypothalamus
-Testosterone defeminizes hypothalamus during embryogenesis and eliminates surge center
-Onset of puberty is consequence of decreased hypothalamic sensitivity to negative feedback in response to testosterone/estradiol
Development of female hypothalamus
-Have surge center sensitive to positive feedback by estradiol
-Pre pubertal females don’t ovulate because ovaries do not produce enough estrogen to activate surge center
-When estrogen levels reach a certain threshold, it causes a large discharge of GnRH from the surge center by positive feedback
Estrous cycle vs menstrual cycle
Estrous: series of predictable reproductive events that occur between periods of sexual receptivity
Menstrual: series of predictable reproductive events
occurring between successive menstrual periods (~28 days) After the luteal phase, endometrium is sloughed
Characteristics of estrous cycle
-Begins and ends at estrus (heat)
- Cyclicity continues throughout the adult female’s life
-Main behavioral event: Sexual receptivity & copulation
- If conception does not occur, another cycle begins
-When conception does occur, the female enters a period of anestrus that ends after parturition, uterine involution (acquisition of normal uterine size and function) and lactation
Causes of anestrus
- Physiological causes: Pregnancy, nursing and by the season of the year in some species.
- Environmental causes: Inadequate nutrition, stress
- Pathologic causes: Uterine infections, persistent, corpora lutea, mummified, fetus
Phases of estrous cycle
Follicular phase
Luteal phase
Follicular phase
Period from regression of corpora lutea to ovulation (20% of estrous cycle)
Luteal phase
Period from ovulation until the regression of the
corpora lutea (80 % of estrous cycle).
Dominant structure of follicular phase
Follicles
Dominant hormone of follicular phase
Corpora lutea
Dominant hormone of luteal phase
Progesterone
Stages of the estrous cylcle
Proestrus
Estrus
Metestrus
Diestrus
Proestrus
Formulation of ovulatory follicle & E secretion
Begins when progesterone declines after luteolysis and terminate at onset of estrus
Estrus
Sexual receptivity & peak E secretion
Willing to accept male: standing heat
Lordosis
Metestrus
Corpus lutea formation & beginning of P secretion
Newly ovulated follicle undergoes cellular and structural remodeling –> formation of intraovarian endocrine gland: corpus luteum (aka lutenization)
Diestrus
Sustained luteal secretion of P
High P prompts uterus to prepare suitable environ,ent for early embryo development, eventual attachment of conceptus to endometrium
Anestrus length in the dog
5 months
Proestrus length in the dog
9 days
Estrus length in the dog
9 days
Diestrus length in the dog
2 months
Characteristics of proestrus in the dog
Begins with blood tinged vaginal discharge and vaginal swelling
Ends when bitch accepts male for mating
Characteristics of estrus in the dog
Ovulation completed after third day of estrus
Fertilization after 6th day
Characteristics of diestrus in the dog
Pregnancy
Pseudopregnant: uterine walls thicken, mammary glands may enlarge, no interest in mating
Cats
Pineal gland
Contains specialized secretory cells called pinealocytes which synthesize melatonin
Length of estrus cycle in each species
Circadian rhythm
Suprachiasmatic nucleus
Long day breeders
Short day breeders
T3
Kisspeptin
