Pengaturan hormon: sistem reproduksi Alfiah Hayati Biologi, Unair

Spermatogenesis: Sperm Production in the Testis Seminiferous tubules Spermatids Spermatocytes Spermatozoa Sertoli cells Interstitial tissue Leydig cells Capillaries

Testicular Compartmentalization

Sertoli Cell

Sertoli Cells Function 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 Head Acrosome Nucleus Midpiece Centrioles Mitochondria Tail: flagellum Microtubules Figure 26-10: Sperm structure

The blood-testis barrier: biology, regulation, and physiological role in spermatogenesis The blood-testis barrier (BTB) in mammals (rats)  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 compartments  spermatogenesis The function: an immunological barrier to segregate the postmeiotic germ-cell antigens from the systemic circulation, it creates a unique microenvironment for germ-cell development

BTB restructuring to facilitate germ-cell migration is regulated: 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. BTB restructuring to facilitate germ-cell migration is regulated: two cytokines, namely transforming growth factor-beta3 (TGF-beta3) and tumor necrosis factor-alpha (TNFalpha), via downstream mitogen-activated protein kinases

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  regulators of focal contacts between the ECM and other actively migrating cells (macrophages, fibroblasts cells) These cell-cell junction restructuring at the BTB  regulated the cell-matrix interface

in reproduction system Hormone regulation: in reproduction system

Male Sex Steroid Synthesis

Cholesterol  from plasma Testosteron  in peripheral tissues  to estradiol & androstenedione Androstenedione  source of estradiol in men

Major Testicular Steroids () = Relative activity where T activity=100 Androgens are C19 steroids Majority of 5 a-DHT is formed in peripheral tissues

Transport of Sex Steroids in Males Major Sex Steroid Binding Proteins Testosterone-Estrogen Binding Protein (T1/2=22 seconds) Sex steroids = DHT (100) >T (33) >E (25) Albumin (T 1/2-=1 second) Cortisol Binding Globulin (No binding to DHT, T or E2, but 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 Increased Nitrogen Balance Increased muscle mass, larynx size

Androgen Activity 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 (1) Androgen-Receptor Interactions Both testosterone (T) and dihydrotestosterone (DHT) interact  androgen receptor DHT has a higher affinity for the androgen receptor than T

Androgen Activity (2) T-Androgen Receptor Interaction Feedback regulation of gonadotropin secretion Differentiation of Wolffian duct DHT-Androgen Receptor Interaction External genitalia differentiation

Regulation of Spermatogenesis GnRH  LH  Leydig cells  testosterone  sex charact GnRH  FSH  Sertoli cells  spermatocyte maturation Inhibin feedback – FSH  testosterone

Regulation of Spermatogenesis Figure 26-11: Hormonal control of spermatogenesis

Testicular Cell Interactions

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

Oogenesis

Hypothalamus-Pituitary-ovary (1)

Hypothalamus-Pituitary-ovary (2)

Hypothalamus-Pituitary-uterine (1)

Hypothalamus-Pituitary-uterine (2)

Hypothalamus-Pituitary-uterine (3)

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