FUNGSI REPRODUKSI PRIA, HORMON SEKS PRIA DAN GLANDULA PINEALIS

The male reproductive system, like that of the female, consists of those organs whose function is to produce a new individual, i.e., to accomplish reproduction. This system consists of a pair of testes and a network of excretory ducts (epididymis, ductus deferens (vas deferens), and ejaculatory ducts), seminal vesicles, the prostate, the bulbourethral glands, and the penis.
illu_repdt_male Fungsi reproduksi pria dapat dibagi dalam tiga subgolongan utama: pertama, spermatogenesis, yang hanya berarti pembentukan sperma; kedua, pelaksanaan kerja seksual pria; dan ketiga, pengaturan fungsi seksual pria oleh berbagai hormone. Yang berhubungan dengan fungsi reproduksi ini adalah efek hormone seks pria pada organ seks tambahan, pada metabolisme sel, pada pertumbuhan, dan pada fungsi tubuh lain.

Anatomi Fisiologi Organ Seks Pria.

Testis terdiri dari sejumlah besar tubulus seminiferus yang berkelok-kelok, tempat sperma dibentuk. Sperma kemudian dikosongkan ke dalam epidimis, dan kemudian menuju vas deferens, yang membesar pada ampula vas deferens segera sebelum vas masuk ke badan kelenjar prostate. Vesika seminalis, masing-masing terletak di tiap sisi prostate, bermuara dalam ujung prostatik ampula, serta isi dari kedua ampula dan vesika seminalis berjalan masuk duktus ejakulatorius yang masuk ke dalam badan kelenjar prostate untuk bermuara ke dalam uretra interna. Duktus prostatikus selanjutnya bermuara ke dalam duktus ejakulatoris. Akhirnya uretra merupakan penghubung terakhir ke luar. Uretra disuplai dengan mucus yang berasal dari banyak kelenjar Littre kecil, yang terletak sepanjang uretra dan juga dari kelenjar bulbouretralis besar bilateral yang terletak dekat pangkal uretra.

The male gonads, testes, or testicles, begin their development high in the abdominal cavity, near the kidneys. During the last two months before birth, or shortly after birth, they descend through the inguinal canal into the scrotum, a pouch that extends below the abdomen, posterior to the penis. Although this location of the testes, outside the abdominal cavity, may seem to make them vulnerable to injury, it provides a temperature about 3° C below normal body temperature. This lower temperature is necessary for the production of viable sperm.The scrotum consists of skin and subcutaneous tissue. A vertical septum, or partition, of subcutaneous tissue in the center

divides it into two parts, each containing one testis. Smooth muscle fibers, called the dartos muscle, in the subcutaneous tissue contract to give the scrotum its wrinkled appearance. When these fibers are relaxed, the scrotum is smooth. Another muscle, the cremaster muscle, consists of skeletal muscle fibers and controls the position of the scrotum and testes. When it is cold or a man is sexually aroused, this muscle contracts to pull the testes closer to the body for warmth.
Structure

Each testis is an oval structure about 5 cm long and 3 cm in diameter. A tough, white fibrous connective tissue capsule, the tunica albuginea, surrounds each testis and extends inward to form septa that partition the organ into lobules. There are about 250 lobules in each testis. Each lobule contains 1 to 4 highly coiled seminiferous tubules that converge to form a single straight tubule, which leads into the rete testis. Short efferent ducts exit the testes. Interstitial cells (cells of Leydig), which produce male sex hormones, are located between the seminiferous tubules within a lobule.
Spermatogenesis

Sperm are produced by spermatogenesis within the seminiferous tubules. A transverse section of a seminiferous tubule shows that it is packed with cells in various stages of development. Interspersed with these cells, there are large cells that extend from the periphery of the tubule to the lumen. These large cells are the supporting, or sustentacular cells (Sertoli’s cells), which support and nourish the other cells.

Early in embryonic development, primordial germ cells enter the testes and differentiate into spermatogonia, immature cells that remain dormant until puberty. Spermatogonia are diploid cells, each with 46 chromosomes (23 pairs) located around the periphery of the seminiferous tubules. At puberty, hormones stimulate these cells to begin dividing by mitosis. Some of the daughter cells produced by mitosis remain at the periphery as spermatogonia. Others are pushed toward the lumen, undergo some changes, and become primary spermatocytes. Because they are produced by mitosis, primary spermatocytes, like spermatogonia, are diploid and have 46 chromosomes.

Each primary spermatocytes goes through the first meiotic division, meiosis I, to produce two secondary spermatocytes, each with 23 chromosomes (haploid). Just prior to this division, the genetic material is replicated so that each chromosome consists of two strands, called chromatids, that are joined by a centromere. During meiosis I, one chromosome, consisting of two chromatids, goes to each secondary spermatocyte. In the second meiotic division, meiosis II, each secondary spermatocyte divides to produce two spermatids. There is no replication of genetic material in this division, but the centromere divides so that a single-stranded chromatid goes to each cell. As a result of the two meiotic divisions, each primary spermatocyte produces four spermatids. During spermatogenesis there are two cellular divisions, but only one replication of DNA so that each spermatid has 23 chromosomes (haploid), one from each pair in the original primary spermatocyte. Each successive stage in spermatogenesis is pushed toward the center of the tubule so that the more immature cells are at the periphery and the more differentiated cells are nearer the center.

illu_testis
Spermatogenesis (and oogenesis in the female) differs from mitosis because the resulting cells have only half the number of chromosomes as the original cell. When the sperm cell nucleus unites with an egg cell nucleus, the full number of chromosomes is restored. If sperm and egg cells were produced by mitosis, then each successive generation would have twice the number of chromosomes as the preceding one.

The final step in the development of sperm is called spermiogenesis. In this process, the spermatids formed from spermatogenesis become mature spermatozoa, or sperm. The mature sperm cell has a head, midpiece, and tail. The head, also called the nuclear region, contains the 23 chromosomes surrounded by a nuclear membrane. The tip of the head is covered by an acrosome, which contains enzymes that help the sperm penetrate the female gamete. The midpiece, metabolic region, contains mitochondria that provide adenosine triphosphate (ATP). The tail, locomotor region, uses a typical flagellum for locomotion. The sperm are released into the lumen of the seminiferous tubule and leave the testes. They then enter the epididymis where they undergo their final maturation and become capable of fertilizing a female gamete.

Sperm production begins at puberty and continues throughout the life of a male. The entire process, beginning with a primary spermatocyte, takes about 74 days. After ejaculation, the sperm can live for about 48 hours in the female reproductive tract.
SPERMATOGENESIS

Spermatogenesis terjadi pada semua tubulus seminiferus selama kehidupan seks aktif, mulai rata-rata pada usia 13 tahun, sebagai akibat perangsangan oleh hormone-hormon gonadotropin adenohipofisis dan terus berlangsung selama hidup.

• Langkah-langkah spermatogenesis

Tubulus seminiferus, mengandung banyak sel epitel germinativum yang berukuran kecil sampai sedang yang dinamakan spermatogonia, yang terletak dalam dua sampai tiga lapisan sepanjang pinggir luar epitel tubulus. Sel-sel ini terus mengalami proliferasi untuk melengkapi mereka kembali, dan sebagian dari mereka berdiferensiasi melalui stadium-stadium definitive perkembangan untuk membentuk sperma.

Stadium pertama spermatogenesis adalah pertumbuhan beberapa spermatogonia menjadi sel yang sangat besar yang dinamakan spermatosit. Kemudian spermatosis membelah dengan proses meiosis membentuk dua spermatosit, masing-masing mengandung 23 kromosom. Spermatid tidak membelah lagi tetapi menjadi matur selama beberapa minggu untuk menjadi spermatozoa.

Kromosom Seks.

Pada setiap spermatogonium, salah satu dari 23 pasang kromosom membawa informasi genetic yang menentukan seks dari turunan akhir. Pasangan ini terdiri dari satu kromosom “X”, yang dinamakan kromosom wanita dan satu kromosom “Y”, kromosom pria. Selama pembelahan mitosis, kromosom penentu seks dibagi diantara spermatid sehingga separoh sperma menjadi sperma pria yang mengandung kromosom “Y” dan setengah lainnya sperma wanita yang mengandung kromosom “X”. Kelamin dari keturunan ditentukan oleh jenis sperma mana yang mengadakan fertilisasi pada ovum.

Pembentukan Sperma.19471

Bila spermatid pertama kali dibentuk, mereka masih mempunyai sifat umum sel epiteloid, tetapi segera sebagian besar sitoplasmanya menghilang, dan setiap spermatid mulai memanjang menjadi spermatozoa, terdiri atas kepala, leher, badan, dan ekor. Untuk membentuk kepala, zat inti memadat menjadi suatu massa yang padat, dan membrane sel berkontraksi sekitar inti. Ini adalah zat inti yang melakukan fertilisasi ovum.

Di depan kepala sperma terdapat struktur kecil yang dinamakan akrosom, yang dibentuk dari aparatus golgi serta mengandung hialuronidase dan protease yang memegang peranan penting untuk masuknya sperma ke dalam ovum.

Sentriol mengelompok pada leher sperma dan mitokondria tersusun berbentuk spiral dalam badan.
male_reproductive_hormone_chartYang menonjol ke luar tubuh adalah ekor panjang, yang merupakan pertumbuhan keluar dari salah satu sentriol. Ekor hampir mempunyai struktur yang hampir sama seperti silia. Ekor mengandung dua pasang mikrotubulus yang turun ke tengah dan sembilan mikrotubulus ganda yang tersusun sekitar pinggir. Ekor diliputi oleh perluasan membrane sel, dan mengandung banyak adenosine trifosfat, yang niscaya memberi energi pergerakan ekor. Pada pengeluaran sperma dari saluran genitalis pria ke dalam saluran genitalis wanita, ekor mulai bergerak bolak-balik dan bergerak spiral pada ujungnya, memberikan pendorongan yang menyerupai ular yang menggerakkan sperma ke depan dengan kecepatan maksimum sekitar 20 sentimeter per jam.

The penis, the male copulatory organ, is a cylindrical pendant organ located anterior to the scrotum and functions to transfer sperm to the vagina. The penis consists of three columns of erectile tissue that are wrapped in connective tissue and covered with skin. The two dorsal columns are the corpora cavernosa. The single, midline ventral column surrounds the urethra and is called the corpus spongiosum.
illu_penis
The penis has a root, body (shaft), and glans penis. The root of the penis attaches it to the pubic arch and the body is the visible, pendant portion. The corpus spongiosum expands at the distal end to form the glans penis. The urethra, which extends throughout the length of the corpus spongiosum, opens through the external urethral orifice at the tip of the glans penis. A loose fold of skin, called the prepuce, or foreskin, covers the glans penis.

sumber ;

http://training.seer.cancer.gov/module_anatomy/images/illu_repdt_male.jpg&imgref

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