Transcript Regulasi sistem reproduksi jantan

Regulasi sistem reproduksi
jantan
• Regulasi organ reproduksi jantan antara
lain pada testis, skrotum, epididimis, vas
deferent, uretra, dan kelenjar asesoris
• 2. Struktur pendukung: jaringan saraf dan
peredaran darah
The blood-testis barrier: its biology, regulation, and physiological role in
spermatogenesis
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The blood-testis barrier (BTB) in mammals, such as rats, is composed of the tight junction (TJ),
the basal ectoplasmic specialization (basal ES), the basal tubulobulbar complex (basal TBC) (both
are testis-specific actin-based adherens junction [AJ] types), and the desmosome-like junction
that are present side-by-side in the seminiferous epithelium. The BTB physically divides the
seminiferous epithelium into basal and apical (or adluminal) compartments, and is pivotal to
spermatogenesis. Besides its function as an immunological barrier to segregate the postmeiotic
germ-cell antigens from the systemic circulation, it creates a unique microenvironment for germcell development and confers cell polarity. During spermatogenesis, the BTB in rodents must
physically disassemble to permit the passage of preleptotene and leptotene spermatocytes. This
occurs at late stage VII through early stage VIII of the epithelial cycle. Studies have shown that
this dynamic BTB restructuring to facilitate germ-cell migration is regulated by two cytokines,
namely transforming growth factor-beta3 (TGF-beta3) and tumor necrosis factor-alpha
(TNFalpha), via downstream mitogen-activated protein kinases. These cytokines determine the
homeostasis of TJ- and basal ES-structural proteins, proteases, protease inhibitors, and other
extracellular matrix (ECM) proteins (e.g., collagen) in the seminiferous epithelium. Some of these
molecules are known regulators of focal contacts between the ECM and other actively migrating
cells, such as macrophages, fibroblasts, or malignant cells. These findings also illustrate that cellcell junction restructuring at the BTB is regulated by mechanisms involved in the junction turnover
at the cell-matrix interface. This review critically discusses these latest findings in the field in light
of their significance in the biology and regulation of the BTB pertinent to spermatogenesis.
Male Reproduction
Felix E. Grissom, Ph.D.
2219 Numa P.G. Adams
Howard University
Tel. 202 806-4512
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Male Reproductive Anatomy
and
Physiology
Testis
Epididymis
Vas deferens
Seminal vesicle
Prostate
Bulbourethral
Ejaculatory duct
Urethra
• Penis
Major Testicular Steroids
• () = Relative
activity where T
activity=100
• Androgens are C19
steroids
• Majority of 5 a-DHT
is formed in
peripheral tissues
Male Sex Steroid Synthesis
• Cholesterol may
be from plasma or
de novo synthesis
• T may be
converted in
peripheral tissues
to estradiol &
androstenedione
• Androstenedione
is the major
source of estradiol
in men
• Delta-5 pathway is
the major route in
men
Transport of Sex Steroids in
Males
• Major Sex Steroid Binding Proteins
• Testosterone-Estrogen Binding Protein
– One high affinity binding site (T1/2=22 seconds)
– Binding affinity order for sex steroids =
» DHT (100) >T (33) >E (25)
• Albumin
– One low affinity binding site (T 1/2-=1 second)
• Cortisol Binding Globulin
– No binding to DHT, T or E2. Binds Progesterone
• Normal Distribution in Blood
TEBG (30%), Albumin (68%), Free (2%)
Active fraction includes free + albumin-bound
fraction
Androgen Activity
• Increased Spermatogenesis
• Increased Bone Growth
– Increased bone matrix, calcium deposition and
promotes epiphyseal closure
• Increased Nitrogen Balance
– Increased muscle mass, larynx size
• Increased atheletic performance
– Increased basal metabolic rate, red blood cell density
oxygen utilization
• Altered Skin Function
– Increased thickness, melanin deposition sebaceous
gland secretion
Androgen Activity
• Androgen-Receptor Interactions
– Both testosterone (T) and
dihydrotestosterone (DHT) interact with
same androgen receptor
– DHT has a higher affinity for the androgen
receptor than T
• T-Androgen Receptor Interaction
– Feedback regulation of gonadotropin
secretion
– Differentiation of Wolffian duct in utero
• DHT-Androgen Receptor Interaction
– External genitalia differentiation in utero
– Virilization during puberty
Spermatogenesis: Sperm
Production in the Testis
• Seminiferous tubules
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Spermatids
Spermatocytes
Spermatozoa
Sertoli cells
• Interstitial tissue
– Leydig cells
– Capillaries
Testicular
Compartmentalization
Sertoli Cell Function
• Sertoli Cells
– Nourish healthy cells &
phagocytize damaged
germ cells
– Synthesize luminal
proteins
– Maintain tubular fluid
– Convert androgens to
estrogens
– Are site for hormonal
modulation of tubular
function
Spermatogenesis: Sperm
Production in the Testis
Figure 26-9b-e: ANATOMY SUMMARY: Male Reproduction
Spermatozoa Structure and
Functions in Review
• Head
– Acrosome:
– Nucleus:
• Midpiece
– Centrioles:
– Mitochondria:
• Tail: flagellum
– Microtubules:
Figure 26-10: Sperm structure
Regulation of
Spermatogenesis
• GnRH  LH  Leydig cells  testosterone  20
sex charact.
• GnRH  FSH  Sertoli cells  spermatoctye
maturation
• Inhibin feedback – FSH, testosterone – short &
long loops
Regulation of
Spermatogenesis
Figure 26-11: Hormonal control of spermatogenesis
Testicular Cell Interactions
• Sertoli cell products
estradiol, inhibin,
activin and other
proteins modulate
leydig cell activity
• Sertoli cell products
modulate germ cell
function
• Leydig cell testosterone
modulate peritubular &
Sertoli cell function
• Peritubular cell
products influence
Sertoli cell activity
Hypothalamic-Pituitary regulation
of Testicular Function