Reproductive System Part # 1 Flashcards
Reproductive system -
The function of the reproductive system is to make new individuals of the species, continuation.
Gonads - The testes and ovaries, they produce the gametes and secrete sex hormones. Ducts - transport and store gametes (sperm/egg).
Accessory sex glands - provide for protection and transport of gametes.
Review of Mitosis: The cell cycle
Interphase - is the period of the cells life when it is caring out normal metabolic activities (growth and final preperation for division (Mitosis). Interphase is not a part of Mitosis! DNA material is in the form of Chromatin.
First Phases of Mitosis: Prophase (Early / late), Metaphase , Anaphase, Telophase - final phase of mitosis. Cytokinesis is occurring during late anaphase and continues beyond telophase and the contractile ring of actin microfilaments form and cleavage furrow develops and pinches the cell apart.
Terminology of Mitosis/Meiosis -
Sister chromatids - during interphase, the DNA gets duplicated which results in the formation of identical sister chromatids connected by a centromere.
Homologous pairs of chromosomes - most of our cells are diploid, meaning they have two copies of chromosome. They are not identical because we get one copy from each of our parents. Nonsister chromatids - chromatids that are within a homologous pair of chromosomes but on different chromosomes. They are not identical.
Meiosis -
How is meiosis different from mitosis? Meiosis consists of two rounds of cell division (2PMATs) During Prophase I , homologous chromosome pairs synapse line up to form tetrads, (4 chromatids), the non sister chromatids cross over forming a chiasmata. This event contributes to the genetic diversity in the gametes. Homologous chromosomes seperate from each other in anaphase I at the end of telophase I, haploid cells with sister chromatids form Sister chromatids do not seperate until anaphaseII. Gametes are formed fro reproduction rather than new cell for groth or repair. Note: no DNA synthesis occurs between Meiosis I and Meiosis II. Haploid cells result ( a single set of 23 chromosomes).
Male Reproductive system -
Scrotum - sac of loose skin surrounding the testes. Scrotal septum - forms 2 internal sacks ( one for each testis) and contains smooth muscle, the dartos muscle. Dartos muscle - smooth muscle that functions to maintain the temperature of the testes 2-3 C below the core body temperature. Relaxation of the dartos moves the testes away from the warmth of the body and increases the surface area of the scrotal surface for cooling. Contraction of the dartos results in wrinkling of the scrotum.
Spermatic cord - a sheath that encloses the ductus deferens , blood vessels and nerves. Cremaster - skeletal muscle found in the spermatic cord that is a continuation of the internal oblique muscle, similar function as the dartos muscle (elevate the testes with contraction when external environment is cold). Testes (aka tesicles) - glands that are 1” in diameter x 2” long, development is close to the kidneys but they start to lower into the scrotum in the 7th month of fetal development. Cryptorchidism is associated with a higher risk of testicular cancer and sterility if the testies don’t descend. Surgery or hormonal therapies can be used. Tunica vaginalis - a double layer membrane that is derived from the peritoneum. Tunica abuginea of the testies - “ white coat”, the fibrous capsule of the testis that has walls that separate each testis into 200-300 lobules that contain the seminiferous tubules. Seminiferious tubules - “sperm factories” 1-4 per lobule, they converge to form one straight tubule that merges with the rete testis. Efferent ductules - tiny tubes that connect the rete testis to the ductus epididymis.
Spermatogenesis -
Prior to puberty- spermatogonia (2n) divide via mitosis to form primary spermatocytes (2n).
Spermatogenesis - the formation of sperm, (aka spermatoza), the process is divided into 2 phases (early and late), about 300 million sperm per day. Early spermatogenesis (meiosis) : primary spermatocytes (2n) are converted into spermitids (n). Meiosis I forms 2 secondary spermatocytes (haploid cell). In meiosis II, 2 secondary spermatocytes are converted into 4 early spermatids. Late spermatogenesis ( spermiogenesis) : 4 spermatids are converted into 4 spermatoza, the cytoplasmic covering of sustentocytes is removed (spermiation) and the sperm cell is converted into a specialized cell with a flagellum.
3 regions of the sperm cell -
Head - necleus and acrosome ( a specialized lysosome that contains hyaluronidase). Midpiece - mitochondria, ATP production. Tail - flagellum for movement.
Other Cells -
Sustenocytes - ( aka sustentacular cells) found from the basal lamina to the lumen of the seminiferous tubules. They form the blood - testis barrier since the mature sperm are seen as non-self. These cells also produce fluid for the movement of sperm and secrete the hormones inhibin and androgen - binding protein (ABP). ABP binds and concentrates testosterone. Interstitial endocrine cells - (also called Leydig cells) - found in the spaces surrounding the seminiferous tubules. These cells secrete testosterone. GnRH - gonadotropin relesing hormone, secreted by the hypothalamis, stimulates the release of LH and FSH (both are gonadotropins). Luteinizing hormone (LH) - stimulates the interstitial endocrine cells to secrete testosterone which increases sperm production and maintains secondary sex characteristics. Follicle - stimulating hormone (FSH) - stimulates spermatogenesis and stimulates the sustenocytes to secrete ABP ( androgen binding protein). Feedback inhibition: FSH stimulates the sustentocytes to secrete ABP. Testosterone inhibits the release of GnRH , LH, FSH. Inhibin ( secreted by the sustentocytes) inhibits the release of FSH. Inhibin is secreted when the sperm count is greater than 20 million per ml.
Testosterone can be converted into DHT (dihydrotestosterone) by some cells. Both hormones are responsible for: Male pattern of development, at puberty development of primary and secondary sex characteristics, protein anabolism which results in thicker muscle and bone mass.
Continuation of Ducts -
Epididymis - a comma shaped structure that is located on the posterior side of the testis. It functions in the storage of sperm and increases sperm motility ( a part of the maturation process). Ductus (vas) Deferens - after the ductus epididymis straightens ou it becomes the ductus deferens, the pouch at the end is the ampulla. Also used for sperm storage. Ejaculatory ducts - the ampulla of the ductus deferens and the seminal gland feed into the ejaculatory duct which feeds into the urethra. Urethra - three sections: prostatic, intermediate part and the spongy urethra.
Accessory sex glands -
Seminal glands - (2) - (aka seminal vesicle) located between the urinary bladder and the rectum, 60% of the fluid of the semen comes from here, they secrete an alkaline fluid that contains fructose, prostaglandins, and a clotting enzyme (vesiculase). This secretion also contains a yellow fluorescent pigment that is useful for detecting sperm in criminal investigations. Prostate gland (1) - a donut shaped gland, secretes 20% of the seminal fluid which is milky, slightly acidic (6.5), contains citrate (a nutrient), prostate specific antigen (PSA), several enzymes and the antibiotic siminal plasmic. Bulbo-urethral gland (2) - aka the Cowpwr’s gland, the size of a pea, located on either side of the intermediate part of the urethra, the ducts open into the spongy urethra. The secretion is alkaline and is secreted prior to ejaculation to cleanse the urethra, (10% contribution).
Semen - Functions -
Sperm plus seminal fluid (from accessory glands) Overall pH is 7.2 -7.7 “alkaline”. 2-5 ml per ejaculation, 20 -
150 million sperm/ml, less than 20 million sperm/ml = sterile.
Functions : Liquid to transport the sperm, nutrients for sperm motility (movement), Alkalinity to neutralize acidity of the vigina, Enzymes to digest layers of the oocyte, The antibiotic (seminal plasmic( to protect against bacteria in the female reproductive tract.
Penis - 3 main parts - body, root , glans penis
Body - 3 cylinders of tissue, each has its own tunica albuginea: 3 cylinders- 2 corpus cavernosa, a single corpus spongiosum ( spongy urethra passes through here) The erectile tissue present becomes erect with vasodialation ( under parasympathetic control). Root - bulb attached to the body of the penis and 2 crura (tapered ends of the corpus cavernosum). Glands penis - distal end of the penis. Prepuce - foreskin..
Female reproductive system -
Ovaries - they have the same embryonic origin as the testes, size and shape of an unshelled almond.
Ovarian ligament - attaches to the ovary to the uterus, medially. Suspensory ligament - attaches the ovary to the pelvic wall, ;aterally. It is a part of the board ligament. Mesovarium - the part of the peritoneum that is made up of the board ligament. THe mesovarioum and suspensory ligament keep the ovary suspended.
Board ligament - a tent - like fold of the perioneum that is made up of the mesovarium and the suspensory ligament.
Histology of the ovary -
Germinal epithelium - on the outside of the ovary. It is made up of Squamous or low cubidal epithelium. It is not really germinal because it does not produce the eggs. Tunica albuginea - whitish connective tissue located deep to the germinal epithelium. Ovarian cortex - dense connective tissue and ovarian follicles. Ovarian medulla - loose connective tissue with blood vessels, lymphatics and nerves. Follicles are the combination of the oocyte that contains the DNA and the surrounding nutritive cells.
Ovarian follicles ( from least to most mature) -
Primordial follicle - a primary oocyte with a single layer of squamous per-granulosa cells. Primary follicle - a primary oocyte with a single layer of cuboidal granulosa cells. Secondary follicle - a primary oocyte with multiple layers of cuboidal granulosa cells. Vesicular (antral/Greefian) follicle - the mature, fluid - filled, follicle that ruptures to release an ovulated secondary oocyte in a process known as ovulation. Note the secondary oocyte is stuck at metaphae II unless fertilization occurs. Corpus Hemorrhagicum - the ruptured follicle cells that remain briefly right after ovulation. Corpus luteum (“yellow body”) - formed from the remains of the corpus hemorrhagicum. It produces progesterone, estrogens, relaxin and inhibin. Corpus albicans - “whit body”, further degeneration of the corpus luteum if pregnancy does not occur.
