Transcript Introduction to Physiology: The Cell and General Physiology

Male Reproductive
System
Figure 80-1
Guyton & Hall
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Cross section of the
seminiferous tubule
and stages of sperm
development
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Figure 80-2
Guyton & Hall
_
_
Hypothalamic-pituitarygonadal axis
hypothalamus
gonadotropin releasing hormone
_
pulsatile -- 8-14/24h
_
ant. pituitary
pulsatile
FSH
LH
+
Leydig cells
growth
factors
Sertoli cells
androgen
binding
protein
spermatogenesis
(function 2)
estrogens
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inhibin
aromatization
androgens
(function 1)
peripheral
aromatization
pulsatile
Tissues Producing Androgens
cholesterol
adrenal
testis
androstenedione
testosterone
5-reductase
DHT
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CYP 19
E2
peripheral
tissues
Different Stages of Male Sexual Function:
Plasma Testsosterone and Sperm Production
Figure 80-9; Guyton & Hall
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Cell Divisions During
Spermatogenesis
Figure 80-3;
Guyton & Hall
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Differences between Spermatogenesis and Oogenesis
1. In females, mitotic proliferation of germ cells occurs
prior to birth. In males, spermatogonia proliferate
only after puberty.
2. In female, meiotic divisions of primary oocyte produces
only one secondary oocyte. In male, meiotic divisions of
primary spermatocyte produces 4 mature
spermatozoa
3. In female, second meiotic division is completed
only upon fertilization. In male, the products of
meiosis (spermatids) undergo substantial
differentiation in the maturing process.
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Internal structures of the Uterus,
Ovary and a Fallopian Tube.
Figure 81-2; Guyton & Hall
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Fundamental reproductive unit = single ovarian
follicle, composed of one germ cell (oocyte),
surrounded by endocrine cells
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Menstrual cycle – controlled by gonadotropins,
gonadal hormones
Ovarian cycle –
follicular phase – avg 15 d (range, 9-23 days)
ovulation
luteal phase – 13-14 d – less variable than follicular
Endometrial cycle – menstruation, proliferative and
secretory phases
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Ovarian
Cycle:
follicular phase
ovulation
FSH and LH in the
Follicular phase
LH
surge
LH surge lasts 48 h
Inc
GnRH
bursts
FSH
LH
1
14 secretory phase (12d) 28
4 proliferative phase
Endometrial
(11 d)
Cycle: menstrual
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Ovarian
Cycle:
follicular phase
ovulation
LH
surge
FSH
estradiol
LH
neg
feedback--GnRH
1
14
4 Proliferative phase
Endometrial
(11 d)
Cycle: menstrual
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Increase in estradiol to stimulate
LH surge. Then estradiol has
Negative feedback on GnRH to
reduce LH, FSH.
Secretory phase (12d) 28
Stages in follicular
growth and ovulation.
Figure 81-4;
Guyton & Hall
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Phases of Endometrial Cycle
Figure 81-7; Guyton & Hall
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Contraception
Rhythm method: if periodicity of menstrual cycle is 28 d, then
ovulation should be day 13-15: temp decreases and then
increases slightly following ovulation. Also, consistency of
mucus discharge from the vagina changes. Now, ovulation kits
available.
Oral, patch contraceptives: ethinyl estradiol, mestranol;
gestodene, norgestimate – decr. androgenic effects
suppress GnRH, FSH, LH – prevent LH surge (no ovulation)
progestins: cervical mucus thickens, inhibit motility – decr.
transport of ova and sperm – endometrium not conducive to
implantation
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Implant contraceptives: norprogestins: “Norplant” lasts 5 yrs
Depoprovera – last 3 mos – inhibits ovulation, implantation
Intrauterine device – IUD – spermicidal effect caused by
sterile inflammatory reaction – secondarily prevents implantation of zygote
Barrier methods: diaphragm with spermicidal jelly, condoms
Postcoital contraceptives: RU 486 – not approved for use
“Plan B” – oral contraceptives used within 72 hrs of unprotected intercourse
Tubal ligation
Vasectomy
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Menopause
Defn: obsolescence of ovaries, no estradiol production, ova
only occasional secondary follicle, few primary follicles
Occurs at 51.4 yr of age (average)
Due to reduction in estrogen, low levels of inhibin,
no negative feedback of LH and FSH; therefore, high levels
LH and FSH
Can occur naturally, due to surgery or as a result of
chemotherapy
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Rat Data
• Females –
–
–
–
–
–
–
Average overall weight gain = 20.3%
Average weight gain during HRT on E1 = 8.1%
Average weight gain during HRT on E2 = 5.9%
Average estrous cycle length = 4.2 days
Vag smears with E1 = estrous phase
Vag smears with E2 = diestrous phase
• Males –
– Average overall weight gain = 31.2%
– Average weight gain during HRT on T1 = 8.2%
– Average weight gain during HRT on T2 = 10.8%
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