Describe the role of human male in reproduction and physiological functions of the major components of the male reproductive tract
role:
- spermatogenesis
- dispersion of sperm for fertilization major
components of tract:
- spermatic cord:
- coverings: external spermatic fascia, cremaster muscle and fascia, and internal spermatic fascia
- structures: testicular artery, cremastetr artery and vein, artery to vas deferens, pampiniform plexus of testicular veins, gen. branch of genfem nerve, vas deferes, lymphatics, and processus vaginalis. - vas deferens:
- thick, muscular tube that conveys sperm from epididymus to ejactulatory duct. - epididymus:
- long, coiled tube that stores mature sperm until ejactulation
- breaks down damaged sperm and residual products - role in final maturation of sperm - seminiferous tubules:
- internal structure of testes
- produce, maintain, and store sperm
- sertoli and leydig cells - testes:
- contain seminiferous tubules within
Describe the role of Sertoli cells, Leydig cells and the basement membrane in spermatogenesis
Sertoli cells:
- receptor for FSH (GS)
- production of inhibin, aromatase (converts testosterone into estradiol), ABP, and growth factors
Leydig cells:
- receptor for LH (Gs)
- production of testosterone from cholesterol
Basement membrane:
- surrounds seminiferous tubules - forms blood-testis-barrier
Understand aging-related changes in the hypothalamo-pituitary-goandal axis that lead to puberty, reproductive maturity, and reproductive senescence (andropause)
In FETAL development:
testosterone levels responsible for:
– development of the mesonephric duct
– differentiation of external genitalia (penis and scrotum)
– testicular descent
Antimullerian hormone responsible for:
– suppression of female development
At PUBERTY: (testosterone)
- increase size of reproductive organs
- promotion of spermatogenesis
- secondary male characteristics
- closure of epiphyseal plate
- increased BMR & RBC mass
In ADULT:
- deepening of voice
- thickening of skin and sebaceous gland secretions - male pattern baldness
- increase of body hair
- deposition of protein, increasing muscle mass
- increased strength and bone size
Describe each of these hormones GnRH , FSH, LH and their mechanism of action
GnRH (Gonadotropin Releasing Hormone):
- secreted by the hypothalamus in a pulsatile manner
- stimulates the ant. pit. to secrete FSH and LH via Gq mechanism
FSH (Follicle Stimulating Hormone):
- acts on the Sertoli cells of the testes via Gs mechanism to cause the production and secretion of inhibin, ABP, aromatase, and GFs
LH (Luteinizing Hormone):
- acts on the Leydig cells of the testes via Gs mechanism to cause the production and secretion of testosterone.
List the major target organs for testosterone and other androgens.
Target organs of testosterone:
- penis and scrotum
- accessory organs
- testes
Describe the biosynthesis, mechanism of transport within the blood, metabolism and elimination of testosterone and related androgens
Testosterone travels in the blood bound to sex-hormone binding globulin or albumin
Free testosterone is converted to more active/potent form DHT by 5’-alpha reductase
Testosterone is broken down in the liver and excreted by the kidneys
Describe the neural, vascular, and endocrine components of the erection and ejaculation response.
Formation of ejaculate:
- epididymus: 10%
- seminal vesicles: 60%; sperm, fructose, prostaglandins (for uterine contractions), and clotting factors
- prostate gland: 30%; alkalinization, semen clotters, and unclotters.
Erection: “Point and Shoot”
- psycho/physical stimuli –> increased parasympathetic activity and decreased sympathetic activity –> vasodilation via NO and/or Ach (increased cGMP) –> erection
Ejaculation:
Emission:
– sympathetic contraction of genital duct and accessory organs (vas deferens, prostate, and seminal vesicles)
Expulsion:
– semen expelled in a rhythmic muscle contraction at base of penis
Identify the causes and consequences of over secretion and under secretion of testosterone for a)prepubertal and b)postpubescent males c)infertility
LOSS of Testes: Hypogonadism or Adiposogenital syndrom (inability to secrete GnRH)
a. Prepubertal:
- infantile sex organs and characteristic
- bones longer and weaker
b. postpubescent:
- decrease in sex organ size
- increased voice pitch
- loss of bone and protein
- decreased libido
- difficulty for erection and rare ejaculation
c. Infertility:
- sperm count < 20 mil/ml
- abnormal shape
- lack of motility
** in fetus: development of female sex organs
Understand how the hypothalamo-pituitary-goandal axis regulates hormone secretion
Describe the role of human female in reproduction
- Production of egg
- Ovulation
- Implantation of egg
- Pregnancy
- Birth
- Lactation
Explain the roles of GnRH, FSH, LH, estradiol, and inhibin in oogenesis and follicular maturation in females at puberty, the start of ovarian cycle
Describe the hormonal regulation of estrogen and progesterone biosynthesis and secretion by the ovary.
GnRH (Gonadotropin Releasing Hormone):
- secreted from the hypothalamus
- acts on anterior pituitary via Gq mechanism to stimulate the production and secretion of FSH & LH
FSH (Follicle-Stimulating Hormone):
- secreted by the anterior pituitary
- acts on granulosa cells of the ovaries via Gs mechanism during the early-mid follicular phase to cause the secretion of estradiol.
LH (Luteinizing Hormone):
- secreted by the anterior pituitary
- acts on the theca cells of the ovaries via Gs mechanism to stimulate the conversion of cholesterol to pregnenolone and then androstenedione during the early-mid follicular phase.
- acts on the theca cells of ovaries vis Gs mechanism to stimulate secretion of progesterone from androstenedione during the late follicular phase
- acts on the granulosa cells of ovaries via Gs mechanism during the late follicular phase to synthesis and release progesterone and synthesize and upregulate the activity of aromatase, which converts Androstenedione secreted by theca cells to estradiol.
- peaking of LH during the late follicular phase stimulates progesterone increase, leading to ovulation.
Estradiol:
- secreted by granulosa cells and theca cells of ovaries.
- during early-mid follicular phase, negatively feeds back to hypothalamus via beta-adrenergic receptors, causing decreased secretion of GnRH.
- during late follicular phase, positively feeds back to hypothalamus via NPY receptors, causing an increase of GnRH, which increases androgens, estrogen, and progesterone levels.
Inhibin:
- secreted by the granulosa cells of ovaries
- negatively feeds back to anterior pituitary to inhibit the secretion of FSH, making progesterone levels to be greater than estrogen levels.
Describe the hormonal regulation of progesterone biosynthesis and secretion by the ovary.
Progesterone:
- secreted by corpus luteum, theca cells, and granulosa cells.
- secreted by placenta during pregnancy
- negatively feeds back to hypothalamus vis beta-endorphin receptor to decrease the levels of GnRH during the luteal phase
Functions:
- maintains and proliferates the endometrial lining of the uterus
- inhibits estrogen, role in LH and FSH surge
- stimulates ovulation via synthesis and secretion of collagenase and prostaglandins, which break down the wall of ovary and swell the follicle
- promotes breast development of lobules and alveoli of breast
- decreases uterine excitability
Describe the the hormonal changes, follicular development, ovulation formation & atresia of corpus luteum throughout the the ovarian cycle
List the major target organs for estrogen action and describe its effects on each.
- reproductive organs: increase size
- oviducts: increase number of cilia
- uterus: preparation of endometrium for puberty & menses
- vagina: preparation of epithelium for trauma
- ovaries: ovarian cycle
- breast: development
- bone and fat: building, epiphyseal plate fusion, and deposition
List the principal physiological actions of progesterone, its major effects on target organs.
- uterus: proliferation of endometrium; inhibition of excitability
- ovaries: ovulation
- breast: lobule and alveoli development
Describe how the changes in ovarian steroids produce the proliferative and secretory phases of the uterine endometrium and menstruation and the changes in basal body temperature during the menstrual cycle
Understand aging-related changes in the hypothalamo-pituitary-goandal axis that lead to puberty, reproductive maturity, and reproductive senescence (menopause).
Puberty:
- GnRH levels increased: ovarian activity
- increased estrogen levels: reproductive organ development
Menopause:
- cessation of ovarian cycle
- decreased estrogen secretion nad atrophy of estrogen dependent tissues (vaginal epithelium & bone)
- FSH > LH levels
Explain the physiological basis of steroid hormone contraception.
- administration of estrogen and progesterone at specific quantity inhibits ovulation
- suppresion of LH surge
Explain age related changes in hypogonadism in females.
At Birth:
- due to absent ovaries or non-functional ovaries
Pre-puberty:
- female eunuchism (failure of gonads to develop)
- no secondary characteristics
- no closure of epiphyseal plates
Post-puberty:
- regression of reproductive organs
- fragile vaginal epithelium
- oligo/amenorrhea
- prolonged ovarian cycle
