Reproductive System

• Male Reproductive System


  The organs of the male reproductive system are the testes; system of ducts (epididymis, ductus deferens, ejaculatory ducts, and urethra); accessory sex glands (seminal vesicles, prostate, and bulbourethral glands); and several supporting structures, including the scrotum and the penis
• Functions of the Male Reproductive System

  • The testes produce sperm and the male sex hormone testosterone
  • The ducts transport, store, and assist in the maturation sperm
  • The accessory sex glands secrete most of the liquid portion of semen
  • The penis contains the urethra, a passageway for ejaculation of semen and excretion of urine
• Anatomy of the Testes

  • The testes are a pair of oval glands located within the scrotal sac, which are covered by a fibrous membrane called the tunica albuginea
  • The tunica albuginea folds in on itself to form septa
  • The septa divide the testes into lobules, each of which contains 1 – 3 seminiferous tubules
  • The seminiferous tubules converge at the rete testis and continue as efferent ductules to the epididymis
  • The testes produce sperm and secrete hormones; testosterone, inhibin
• The epididymis


  • The epididymis is continuous with the efferent ductulus and lies on the posterolateral border of each testis
  • It is a tightly coiled tube and is one of the sites of sperm maturation
  • At its distal end the epididymis is continuous with the vas deferens
  • It can be divided into 3 sections – the head, body and tail
• The vas deferens


  • The vas deferens connects the epididymis to the urethra and transports sperm during ejaculation
  • There is a right and a left vas deferens, both of which travel around the back of the bladder, widen to form the amupullae of the vas deferens the join with the seminal vesicle duct to form the ejaculatory duct which travels through the prostate to empty into the urethra
• The Prostate Gland


  • The prostate gland is an unpaired gland lying in the midline of the body
  • It sits below the bladder and secretes up to 25% of the contents of seminal fluid
  • The urethra runs through the prostate gland and these secretions enter it through many prostatic ducts
  • The prostate is wider at the top (the base) than it is at the bottom (apex)
• The Seminal Vesicles & Bulbourethral Gland

  • The seminal vesicles are a pair of glands, whose secretions make up the majority of seminal fluid (an alkaline, viscous fluid that constitutes about 60% of the volume of semen and contributes to sperm viability)
  • The bulbourethral glands secrete mucus for lubrication and an alkaline substance that neutralizes acid
  • Semen is a mixture of sperm and seminal fluid; it provides the fluid in which sperm are transported, supplies nutrients, and neutralizes the acidity of the male urethra and the vagina
• The scrotum


  • Just below the skin of the scrotum is the dartos – a layer of mostly smooth muscle
  • This layer is superficial to the outermost layer of the spermatic cord and plays a role in the regulation of testis temperature
  • The scrotum is a suspended sac of skin and smooth muscle, which covers the testes, epididymis and the spermatic cord
• Penis


  • Composed of erectile tissue, transports urine and semen via the urethra
  • Glans penis - Formed by the terminal part of the corpus spongiosum
  • Body (corpus) contains the single corpus spongiosum and the paired corpora cavernosa
  • Corpus spongiosum - Erectile tissue surrounding the spongy urethra
  • Corpora cavernosa - Paired erectile tissues
  • Root - The attached part of the penis consisting of the bulb and two crura
• Urethra


  • The male urethra is an 18-22 cm long muscular tube that conveys urine from the urinary bladder to the exterior via an external opening in the perineum and also functions to provide an exit for semen (sperm) and glandular secretions during ejaculation
  • It runs from the internal urethral orifice of the bladder to the external urethral orifice located at the tip of the glans penis
  • In males, this organ is divisible into four parts: preprostatic (intramural), prostatic, membranous (intermediate) and spongy (penile) parts
  • The structure and function of the urethra are different between male and female anatomy. In males, the urethra is long, as it runs the length of the penis, and a part of the urinary system as well as the reproductive system. In females, the urethra is very short (about 4 cm long) and not part of the reproductive system
• Spermatogenesis


  1. Occurs in the testes and consists of meiosis I, meiosis II, and spermiogenesis

  2. It results in the formation of four haploid sperm cells from a primary spermatocyte

  3. At puberty, gonadotropin-releasing hormone (GnRH) stimulates anterior pituitary secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH)

  4. LH stimulates Leydig cells to produce testosterone

  5. FSH and testosterone initiate spermatogenesis
• Leydig cells produce testosterone
• Parts of a Sperm Cell

  • Mature sperm consist of a head and a tail
  • Their function is to fertilize a secondary oocyte
  • The acrosome contains enzymes that break down the outer membrane of an egg cell, allowing the sperm to fertilize the egg
• Hormones of Male Reproductive System

  • Testosterone controls the growth, development, and maintenance of sex organs; stimulates bone growth, protein anabolism, and sperm maturation; and stimulates development of male secondary sex characteristics
  • Inhibin is produced by Sertoli cells; its inhibition of FSH helps regulate the rate of spermatogenesis
  • The Sertoli cells are epithelial cells, support the germ cell progenitors and help to transfer nutrients from the nearby capillaries, produce testicular fluid
• Testosterone


  • Testosterone is the major androgen in the testis that regulates spermatogenesis
  • Testosterone is produced by the Leydig cell in response to stimulation with luteinizing hormone (LH) and acts as a paracrine factor that diffuses into the seminiferous tubules
  • Androgen effects are mediated by the androgen receptor (AR)
  • The testosterone diffuses into Sertoli cells binds to the AR present in the cytoplasm and nucleus to initiate the functional responses required to support spermatogenesis
• DHT


  • DHT plays a vital role in the sexual development of males
  • During embryonic life, it is involved primarily in the sexual differentiation of organs
  • Through adolescence and adult life, DHT promotes prostate growth, sebaceous gland activity, male pattern baldness, and body, facial and pubic hair growth
• Female Reproductive System


  • The organs of the female reproduction system include the ovaries, uterine (fallopian) tubes, uterus, vagina, and vulva
  • The mammary glands are also considered part of the reproductive system
• Functions of the Female Reproductive System

  • The ovaries produce secondary oocytes and hormones, including estrogens, progesterone, inhibin, and relaxin
  • The uterine tubes transport a secondary oocyte to the uterus, and normally are the sites where fertilization occurs
  • The uterus is the site of implantation of a fertilized ovum, development of the fetus during pregnancy, and labor
  • The mammary glands synthesize, secrete, and eject milk for nourishment of the newborn
• Components of the Vulva

  • Mons pubis – it is a cushion like fatty tissue that is covered by skin and public hair
  • Labia majora – These are the fleshy folds of skin tissue that surrounds the vaginal opening
  • Labia minora – There are paired folds of skin tissue under the labia majora, lacking fatty tissue
  • Clitoris – It is a tiny finger-like structure that lies at the upper joint of the two labia minora and just above the vaginal opening
• Functions of the Female Reproductive System

  • The ovaries produce secondary oocytes and hormones, including estrogens, progesterone, inhibin, and relaxin
  • The uterine tubes transport a secondary oocyte to the uterus, and normally are the sites where fertilization occurs
  • The uterus is the site of implantation of a fertilized ovum, development of the fetus during pregnancy, and labor
  • The mammary glands synthesize, secrete, and eject milk for nourishment of the newborn
• Components of the Vulva

  • Mons pubis - it is a cushion like fatty tissue that is covered by skin and public hair
  • Labia majora - These are the fleshy folds of skin tissue that surrounds the vaginal opening
  • Labia minora - There are paired folds of skin tissue under the labia majora, lacking fatty tissue
  • Clitoris - It is a tiny finger-like structure that lies at the upper joint of the two labia minora and just above the urethral opening
• Vagina


  An elastic, muscular canal with a soft, flexible lining that provides lubrication and sensation. The vagina connects the uterus to the outside world. The vulva and labia form the entrance, and the cervix of the uterus protrudes into the vagina, forming the interior end. It is lined by stratified squamous epithelial cells to protect the underlying tissue.
• Parts of the Uterus

  • Fundus - top of the uterus, above the entry point of the uterine tubes
  • Body - usual site for implantation of the blastocyst
  • Cervix - lower part of uterus linking it with the vagina. This part is structurally and functionally different to the rest of the uterus
• Uterus Wall Structure


  • Perimetrium (peritoneum) - External thin membrane
  • Myometrium - Middle dense layer of smooth muscles. It is the layer that is responsible for contractions during delivery
  • Endometrium - inner mucous membrane lining the uterus. It can be further subdivided into 2 parts: Deep stratum basalis (Changes little throughout the menstrual cycle and is not shed at menstruation), Superficial stratum functionalis (Proliferates in response to oestrogens, and becomes secretory in response to progesterone. It is shed during menstruation and regenerates from cells in the stratum basalis layer)
• Fallopian Tubes


  Each fallopian tube is around 10-12 cm long and extends from the sides of each ovary to the uterus. A small funnel-shaped portion closer to the ovary is called infundibulum. The edges of the infundibulum consist of finger-like small projections called fimbriae, which help in the collection of ovum after ovulation. The infundibulum is further extended to the wider part of the oviduct called ampulla. The last portion of the oviduct, isthmus has a narrow lumen, and it connects to the uterus.
• Ovaries


  The prime female sex organs that produce the ovum and many ovarian (steroid) hormones. The ovaries are located on each side of the lower abdomen. Each ovary is around 2 to 4 centimetres in length and is attached to the pelvic wall and uterus by ligaments. Each ovary is enveloped by a thin epithelium which encases the ovarian stroma. The stroma is further divided into two zones – an inner medulla and a peripheral cortex.
• Oogenesis


  1. Begins in the ovaries. The oogenesis sequence includes meiosis I and meiosis II. Meiosis II is completed only after an ovulated secondary oocyte is fertilized by a sperm cell

  2. The uterine (fallopian) tube, which transports a secondary oocyte from an ovary to the uterus, is the normal site of fertilization
• Components of the Female Reproductive Cycle

  • Ovarian cycle - Development of a secondary oocyte
  • Uterine (menstrual) cycle - Preparation of the endometrium each month to receive a fertilized egg
• Regulation of the Female Reproductive Cycle

  1. GnRH from the hypothalamus stimulates the release of FSH and LH by the anterior pituitary

  2. FSH stimulates development of follicles and initiates secretion of estrogens by the follicles

  3. LH stimulates further development of the follicles, secretion of estrogens by follicular cells, ovulation, formation of the corpus luteum, and the secretion of progesterone and estrogens
• Phases of the Female Reproductive Cycle

  • Menstrual phase - Part of the endometrium is shed, discharging blood and tissue cells
  • Preovulatory phase - A group of follicles in the ovaries begins to undergo maturation. One follicle outgrows the others and becomes dominant while the others die. Endometrial repair occurs in the uterus. Estrogens are the dominant ovarian hormones
  • Ovulation - The rupture of the dominant mature (Graafian) follicle and the release of a secondary oocyte into the pelvic cavity. Brought about by a surge of luteinizing hormone (LH)
  • Postovulatory phase - Both progesterone and estrogens are secreted in large quantity by the corpus luteum of the ovary, and the uterine endometrium thickens in readiness for implantation. If fertilization and implantation do not occur, the corpus luteum degenerates, and the resulting low levels of progesterone and estrogens allow discharge of the endometrium (menstruation) followed by the initiation of another reproductive cycle. If fertilization and implantation occur, the corpus luteum is maintained by human chorionic gonadotropin (hCG).
• Hormones of the Female Reproductive Cycle

  • Estrogens - Stimulate the growth, development, and maintenance of female reproductive structures; the development of secondary sex characteristics; and protein synthesis
  • Progesterone - Works together with estrogens to prepare the endometrium for implantation and the mammary glands for milk synthesis
  • Relaxin - Increases the flexibility of the pubic symphysis and helps dilate the uterine cervix to ease delivery of a baby; synthesized by the corpus luteum
  • Inhibin - Synthesized by granulosa cells. It inhibits the synthesis and release of the follicle-stimulating hormone in the pituitary gland and reduces the hypothalamic LH - releasing hormone content
• Mammary Glands


  Modified sudoriferous (sweat) glands that produce milk. The breasts lie over the pectoralis major and serratus anterior muscles and are attached to them by a layer of connective tissue. Their function is to secrete and eject milk (lactation). Mammary gland development depends on estrogens and progesterone. Milk production is stimulated by prolactin, estrogens, and progesterone; milk ejection is stimulated by oxytocin.
• Changes with Aging in the Reproductive Systems

  • Puberty - Hormone-directed changes start to occur in both sexes around age 10. The period of time when secondary sex characteristics begin to develop and the potential for sexual reproduction arises
  • Females - The reproductive cycle normally occurs once each month from menarche, the first menses, to menopause, the permanent cessation of menses
  • Males - At about age 55 a decline in testosterone synthesis leads to reduced muscle strength, fewer viable sperm, and decreased sexual desire. However, abundant sperm may be present even in old age.
• Common Disorders Affecting the Female Reproductive System

  • Uterine Fibroids - Muscle cells and other tissues that grow in and around the wall of the uterus
  • Endometriosis - The presence and growth of functioning endometrial tissue in places other than the uterus
  • Ovarian cancer
• Common Disorders Affecting the Male Reproductive System

  • Prostate Cancer
  • Benign prostatic hypertrophy