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37 Cards in this Set

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Early puberty is r/t...
earlier pregnancy
The age of menarche is...
getting earlier and earlier; it use to be 16 yo
Prepubescent
hypothalamic-pituitary system is highly sensitive to very low levels of steriod hormones (negative-feedback system)
Three distinct changes occur during puberty:
1. onset of nocturnal sleep-related increase in pulsatile secretion of GnRH and LH
2. Decrease in sensitivity of hypothalamus and pituitary...increase in LH and FSH
3. in females, development of a positive feedback system
One proposed theory of puberty proposes that it is r/t a decrease in melatonin secretion by the pineal gland
Although animal studies have shown that melatonin appears to inhibit hypothalamic-pituitary gland secretion, this has not been documented in humans.
The timing of puberty is influenced by:
1. genetics
2. geographic location, exposure to light, general health and nutrition
3. critical body weight
4. greater percent of body fat (16->23.5%)
5. growth hormone and insulin-like growth factor-I levels
6. leptin production
Menarche
age at first bleed; ovulation often not occuring yet
Gametogenesis
the formation of gametes which are the sperm and egg
Major hormones involved in puberty:
1. FSH
2. LH
3. Estradiol
4. Progesterone
5. Adrenal androgens
6. Testosterone
FSH
1. gemetogenesis
2. estrogen production
LH
1. Leydig cells->testosterone
2. Theca cells->androgens and midcycle surge->ovulation
Estradiol
1. epiphyseal fusion
2. breast development
3. development of labia, vagina, uterus
4. proliferative endometrium
5. increase fat mass
6. triggers midcycle surge of LH
Progesterone
1. secretory endometrium
2. breast development
Adrenal androgens
public hair and linear growth
Testosterone
1. linear growth
2. epiphyseal fusion
3. development of penis, scrotum, prostate, seminal vesicles
4. pubic, axillary, and facial hair
5. increase in size of larynx
6. stimulates sebaceous gland to secrete oil
7. increase libido
8. increase in muscle mass
9. increase in RBC
SRY gene
in it's absence there is a tendency toward the development of female genitalia
Wolffian
male accessory organs
Mullerian
female accessory organs
genetic sex
1. determined at birth
2. determined by the presence of the SRY gene
The embryo initially has indifferent gonads which can become either oocytes or spermatocytes
true
Spermatogenesis
1. begins at puberty
2. is influenced by testosterone
3. involves premordial germ cells
Purpose of meiosis
1. reduce chromosomal number
2. genetic recombination
Oogenesis
1. begins at puberty
2. all oogonia are at the primary oocyte stage at birth (diploid)
3. first meiotic division occurs during fetal life, but is not completed until ovulation (this yields one secondary oocyte which is haploid and one polar body)
4. the secondary oocyte begins the second meiotic division but stops in metaphase until fertilization occurs
5. with fertilization of the secondary oocyte, the second meiotic division is completed and results in: one mature oocyte (23 unpaired chromosomes) and a second polar body
Sperm structure
head, middle body, and principal piece
Sperm head
contains the nucleus and acrosomal cap
Sperm middle body
contains mitochondria (ATP)
Principal piece of the sperm
ATP storage and microtubules
Regulation of Spermatogenesis
1. decrease in testosterone
2. increase in LH production
3. increase in production of testosterone by the Leydig cells
4. the increase in testosterone leads to a decrease in LH
What is the major action of LH in the male?
stimulation of the Leydig cells to secrete testosterone
Role of FSH in the male
stimulation of Sertoli cells and the production of inhibin
FSH stimulates the Sertoli cells in males which leads to...
1. the synthesis of estradiol from testosterone
2. produces androgen-binding protein->binds testosterone
3. produces activin
FSH stimulates the production of inhibin in males which leads to...
1. the blockage of the aromitization of androgens to estradiol
2. negative feedback to the anterior pituitary resulting in a decrease in FSH production
Function of testosterone
1. sexual differentiation in the embryo
2. maturation of external genitalia
3. linear body growth and enlargement of muscle mass
4. enlargement of the larynx and thickening of the vocal cords
5. beard, axillary, and pubic hair growth (also includes balding)
6. libido and sexual potential
Male Fertility
1. less than 50,000,000 sperm per ejaculate is considered infertile (the avg. is 200-300 million)
2. one sperm fertilizes one egg
3. hyaluronidase, which is produced by the sperm, is thought to be one of the enzymes necessary for capacitation
Menstural cycle overview
1. avg. age of menarche is 12.8 yo
2. avg. age of menopause is 52 yo
3. avg. menstural cycle is 28-30 days (consistency is the key)
4. avg. duration of menstruation is 4-6 days
Characteristics of the ovary:
follicle and corpus luteum
Follicle
1. Theca cells synthesize androgens (LH)
2. granulosa cells synthesize estrogens (FSH)
3. graffian follicle- the follicle that matures and ovulates