19 Reproductive System
Functions
1. Production of gametes 2. Fertilization 3. Development and nourishment of a new individual 4. Production of reproductive hormones
SPERM CELL FORMATION
1. Spermatogonia (undeveloped sperm cells) divide by mitosis to form primary spermatocytes. 2. Primary spermatocytes divide by meiosis to produce first secondary spermatocytes and then spermatids. 3. The spermatids then mature to form sperm cells. 4. A spermatid develops a head, midpiece, and flagellum to become a sperm cell. The head contains the acrosome and the nucleus.
Seminal vesicles
2 sac-shaped glands near the ampulla of each ductus deferens Each is about 5 cm long Its thick, mucuslike secretion contains the sugar fructose and other nutrients that nourish sperm cells Secretions also contain proteins that weakly coagulate after ejaculation and enzymes that are thought to help destroy abnormal sperm cells Prostaglandins, which stimulate smooth muscle contractions, are present in high concentrations in the secretions and can cause contractions of the female reproductive tract, which help transport sperm cells through the tract.
Male sex act
A complex series of reflexes that result in erection of the penis, secretion of mucus into the urethra, emission, and ejaculation.
Zygote
A fertilized egg, formed by the union of a male sex cell (a sperm) and a female sex cell (an ovum) Has 46 chromosomes
Prepuce / foreskin
A loose fold of skin that covers the glans penis
SEMINAL FLUID / SEMEN
A mixture of sperm cells and secretions from the male reproductive glands Normal volume: 2-5 mL, with each mL of semen typically containing about 100 million sperm cells. Four fractions: 60% - accounts for the secretions from the seminal vesicles 30% - accounts for the secretions from the prostate gland 5% - accounts for the secretions from the testes 5% - accounts for the secretions from the bulbourethral glands
Bulbourethral glands / cowper glands
A pair of small, mucus-secreting glands located near the base of the penis In young adults, each is about the size of a pea, but they decrease in size with age Produce a mucous secretion, which lubricates the urethra, helps neutralize the contents of the normally acidic urethra, provides a small amount of lubrication during intercourse, and helps reduce acidity in the vagina.
Resolution
A phase that occurs after ejaculation. During resolution, the penis becomes flaccid, an overall feeling of satisfaction exists, and the male is unable to achieve erection and a second ejaculation.
SCROTUM
A saclike structure containing the testes Divided into right and left internal compartments by an incomplete connective tissue septum Beneath the scrotum skin are a layer of loose connective tissue and a layer of smooth muscle called the DARTOS MUSCLE Dartos and Cremaster muscles (extensions of abdominal muscles into the scrotum) help regulate testes temperature.
Acrosome
A vesicle just anterior to the nucleus containing enzymes that are released during the process of fertilization and are necessary for the sperm cell to penetrate the oocyte, or egg cell.
Orgasm / Climax
An intense sensation, that result from pleasurable sensations that occur during the male sex act
EPIDIDYMIS
Comma-shaped structure on the posterior side of the testis Maturation site of spermatozoa/sperms
SPERM MORPHOLOGY
Complete morphology evaluation: Head defects Midpiece defects Tail defects Cytoplasmic defects
Glans penis
Cap-like structure located at the distal end of the penis.
SPERMATOGENESIS
Defined as the formation of sperm cells Begins in the seminiferous tubules at the time of puberty. Sustentacular cells nourish the sperm cells and produce small amounts of hormones.
Prostate gland
Consists of both glandular and muscular tissue and is about the size and shape of a walnut Surrounds the urethra and the two ejaculatory ducts. Its thin, milky secretions have an alkaline ph and help neutralize the acidic urethra, as well as the acidic secretions of the testes, the seminal vesicles, and the vagina. Increased ph is important for normal sperm cell function. The movement of sperm cells is not optimal until the ph is increased to between 6.0 and 6.5. Secretions also contain proteolytic enzymes that break down the coagulated proteins of the seminal vesicles and make the semen more liquid
Seminiferous tubules
Contain germ cells and sustentacular cells, or sertoli cells.
Erectile Dysfunction / Impotence
Failure to achieve erections Can be due to the following reasons: Reduced testosterone secretion resulting from hypothalamic, pituitary, or testicular complications; Defective stimulation of the erectile tissue by nerve fibers, or Reduced response of the blood vessels to neural stimulation. Some men can achieve erections by taking oral medications, such as sildenafil (Viagra), tadalafil (Cialis), or verdenafil (Livitra), or by having specific drugs injected into the base of the penis. These increase blood flow into the erectile tissue of the penis, resulting in erection for many minutes.
Purposes of Seminal Fluid Analysis
Fertility testing Post-vasectomy analysis Forensic / Medico-Legal cases (rape cases)
SPERM CONCENTRATION
Improved Neubauer Counting Chamber Use WBC pipet Diluents: Formalin Sodium bicarbonate cold distilled water Dilution factor: 1:20 If 5 RBC squares were used multiply by 1,000,000 If 2 WBC squares were used multiply by 100,000 Sperm concentration = # of sperms counted x factor sperm conc./ml) Makler Counting Chamber- seminal fluid is counted undiluted; sperms are immobilized through HEATING.
Artificial insemination
In cases of infertility due to low sperm cell count or reduced motility, fertility can sometimes be achieved by collecting several ejaculations, concentrating the sperm cells, and inserting them into the female's reproductive tract, a process called
Testes
Known as male gonads Oval organs, each about 4 - 5 cm long Outer part consists of a thick, white connective tissue capsule Divided into lobules containing the seminiferous tubules (in which sperm cells develop) and interstitial cells / Leydig cells (which secrete testosteron If the testes become too warm or too cold, normal sperm cell development does not occur
Testosterone
Major male hormone secreted by the testes Causes enlargement & differentiation of the male genitals & the reproductive duct system during puberty Necessary for spermatogenesis & for the development of male secondary sexual characteristics Required for normal sex drive.
URETHRA
Male urethra extends from the urinary bladder to the distal end of the penis Can be divided into three parts: the prostatic urethra, which passes through the prostate gland; the membranous urethra, which passes through the floor of the pelvis and is surrounded by the external urinary sphincter; and the spongy urethra, which extends the length of the penis and opens at its end. A passageway for both urine and male reproductive fluids. But, urine and the reproductive fluids do not exit the urethra at the same time. While male reproductive fluids are passing through the urethra, a sympathetic reflex causes the internal urinary sphincter to contract, which keeps semen from passing into the urinary bladder and prevents urine from entering the urethra.
Specimen Collection
Masturbation Coitus Interruptus (withdrawal method of contraception) Condom method- SILASTIC Condom (non-lubricated condom that contains polymeric silicone) Vaginal vault aspiration Abstain from sex or masturbation for a period of 3-5 days and not longer than 7 days Prolonged abstinence will cause increased semen volume but decreased sperm motility. Always note the time of : Collection- usually done at room temperature but should be maintained at 370C. If done outside, semen must be transported in the laboratory within 1 hour. Liquefaction- sperm analysis should only be done after complete semen liquefaction. Normal liquefaction time: 30-60 minutes. If complete liquefaction is not necessary: Break mucus and clumps Add chemicals like amylase or bromelin, plasmin & chymotrypsin
KRUGER'S STRICT CRITERIA
Measurement of the head, neck and tail with the use of micrometer Normal sperm statistics: head: 5um long, 3um wide and the flagellar tail 45um long N. V. 30% of the evaluated sperms should be normal
SEMEN ANALYSIS
Normal volume: 2-5 ml Decreased volume- infertility or incomplete collection Increased volume- prolonged abstinence Consistency- pour in droplets (0- watery to 4 gel-like) Normal pH- alkaline (7.2-8.0) Fresh specimen with a pH < 7.2 abnormality in the epididymis, vas deferens and seminal vessicle Fresh specimen with a pH of > 8.0 infection of the male reproductive tract Sperm concentration - 20 -160 million/ml Sperm count- > 40 million/ejaculate
Sertoli cells
Nourish the germ cells and produce a number of hormones.
Gonadotropin-releasing hormone (GnRH)
Produced in the hypothalamus and released in surges. GnRH stimulates release of LH and FSH from the anterior pituitary. LH stimulates the interstitial cells to produce testosterone. FSH binds to sustentacular cells and stimulates spermatogenesis and secretion of inhibin. Testosterone has a negative-feedback effect on GnRH, LH, and FSH secretion. Inhibin has a negative-feedback effect on FSH secretion.
Infertility
Reduced or diminished fertility Most common cause of infertility in males is a low sperm cell count If the sperm cell count drops to below 20 million sperm cells per ml, the male is usually sterile Decreased sperm cell count can be due to the following: Damage to the testes as a result of trauma, radiation, cryptorchidism Infections, such as mumps, which block the ducts in the epididymis Inadequate secretion of LH and FSH, which can be caused by hypothyroidism, trauma to the hypothalamus, infarctions of the hypothalamus or anterior pituitary gland, or tumors Decreased testosterone secretion Reduced fertility is possible if sperm cell structure is abnormal, due to chromosomal abnormalities caused by genetic factors Infertility can also be caused by reduced sperm cell motility A major cause of reduced sperm cell motility is the presence of antisperm antibodies, which are produced by the immune system and bind to sperm cells.
Puberty
Sequence of events by which a child is transformed into a young adult In boys, puberty commonly begins between the ages of 12 and 14 and is largely completed by age 18. Before puberty, small amounts of testosterone, secreted by the testes and the adrenal cortex, inhibit GnRH release. During puberty, testosterone does not completely suppress GnRH release, resulting in increased production of FSH, LH, and testosterone.
Gametes
Sex cells Sperm in males & oocytes (eggs) in females
Effects of Aging on Male Reproductive System
Sexual activity is often maintained in men as they age, but the frequency of sexual intercourse usually decreases gradually Benign prostatic enlargement is common after 50 years of age. A major consequence of prostatic enlargement is blockage of the prostatic urethra The frequency of prostate cancer also increases as men age and is a significant cause of death in men. The tendency for erectile dysfunction increases as men age
ROUTINE CRITERIA
Smear stained using Wright, Giemsa, Papanicolau ( stain of choice for the evaluation of sperm morphology) Observe/evaluate 200 sperms N.V. > 50% should be normal
Meiosis
Special type of cell division that leads to formation of gametes/sex cells in males & females Each sperm cell and each oocyte contains 23 chromosomes Occurs only in the testis and ovary One cell undergoes 2 consecutive cell divisions to produce 4 daughter cells, each having half as many chromosomes as the parent cell. The 2 divisions of meiosis are called meiosis i and meiosis ii. Like mitosis, each division of meiosis has prophase, metaphase, anaphase, and telophase.
SPERM COUNT
Sperm concentration x volume of seminal fluid Normal value = greater than or equal to 40 million per ejaculate
Male Reproductive System
TESTES DUCTS Epididymis Ducta deferentia (sing. ductus deferens, vas deferens) Urethra Accessory Glands Seminal vesicles Prostate gland Bulbourethral glands Supporting structures Scrotum Penis
Embryo
The developing human between the time of fertilization and 8 weeks of development
Fetus
The developing human from 8 weeks to birth
Erection
The first major component of the male sex act
Ejaculation
The forceful expulsion of the secretions that have accumulated in the urethra to the exterior
PENIS
The male organ for copulation and functions in the transfer of sperm cells from the male to the female. Contains three columns of erectile tissue and engorgement of this erectile tissue with blood causes the penis to enlarge and become firm, a process called erection.
Emission
The movement of sperm cells, mucus, prostatic secretions, and seminal vesicle secretions into the prostatic, membranous, and spongy urethra.
Corpora spongiosum
The third, smaller erectile column that occupies the ventral portion of the penis
Secondary sexual characteristics
Those structural and behavioral changes, other than in the reproductive organs, that develop at puberty and distinguish males from females Include hair distribution and growth, skin texture, fat distribution, skeletal muscle growth, and changes in the larynx. After puberty, testosterone maintains the adult structure of the male genitals, reproductive ducts, and secondary sexual characteristics.
DUCTUS DEFERENS / VAS DEFERENS
Total length is about 45 cm It is the passageway of mature sperm cells from the epididymis. Its wall contains smooth muscle, which contracts in peristaltic waves to propel the sperm cells Increases in diameter before reaching the prostate gland to become the ampulla of the ductus deferens It is the one cut during vasectomy.
Corpora cavernosa
Two columns of erectile tissue that form the dorsal portion and the sides of the penis
Fertilization
Union of sperm cell and an oocyte, along with their genetic material (chromosomes) to produce a new individual
SPERM MOTILITY
Wet preparation, seminal fluid is spread on the slide, evaluation is done at least 20 high power field N.V. > 50% within 1 hour should be motile Grading 4- rapid straight line motility 3- slower speed some with lateral movement 2- slow forward progression, noticeable lateral movement 1- no forward progression 0- no movement N.V. 2.0 grade Abnormality in the head affects ovum/egg penetration Abnormality in the tail affects sperm motility
