Semen (Textbook) Flashcards
Semen Fractions and Sources
Sources:
- Testes
- Epididymis
- Seminal vesicles
- Prostate gland
- Bulbourethral glands
Sperm Secretion
Testes are paired glands in the scrotum that contain
the seminiferous tubules. These tubules contain germ cells for the production of spermatozoa in the epithelial cells.
Germ cells are supported by Sertoli cells
Sertoli cells
Sertoli cells provide support and nutrients for the germ cells as they undergo mitosis and meiosis (spermatogenesis).
Sperm Development
Once spermatogenesis is complete, the immature sperm (nonmotile) enter the epididymis where the sperm mature and develop flagella.
The entire process takes approximately 90 days.
Sperm Transport
Ejaculatory ducts receive sperm from the
ductus deferens and fluid from the seminal vesicles. The seminal vesicles produce most of the fluid present in semen (60% to 70%), and this fluid is the transport medium for the sperm.
The fluid contains a high concentration of fructose and flavin.
Semen Composition
Spermatozoa: 5%
Seminal fluid: 60% to 70%
Prostate fluid: 20% to 30%
Bulbourethral glands: 5%
Prostate Gland
- Located just below the bladder, surrounds the upper urethra and aids in propelling the sperm through the urethra by contractions during ejaculation.
- Approximately 20% to 30% of the semen volume is acidic fluid produced by the prostate gland
- Prostate Gland milky acidic fluid contains acid phosphatase, citric acid, zinc, and proteolytic enzymes responsible for both the coagulation and liquefaction of the semen following ejaculation.
Bulbourethral Glands
Located below the prostate, contribute about 5% of the fluid volume in the form of a thick, alkaline mucus that helps to neutralize acidity from the prostate secretions and the vagina.
Specimen Collection
- Most of the sperm are contained in the first portion of the ejaculate
- Imperative for accurate testing of both fertility and postvasectomy specimens.
- First portion of the ejaculate is missing: sperm count will be decreased, the pH falsely increased, and the specimen will not liquefy.
- Last portion of ejaculate is missing: semen volume is decreased, the sperm count is falsely increased, the pH is falsely decreased, and the specimen will not clot.
Pre- and Post- Specimen Collection Guidelines
- Specimens are collected following a period of sexual abstinence of at least 2 days to not more than 7 days.
- Specimens should be kept at room temperature and delivered to the laboratory within 1 hour of collection, and those awaiting analysis should be kept at 37°C
Fertility Evaluation
Consists of both macroscopic and microscopic examination.
Parameters reported include appearance, volume, viscosity, pH, sperm concentration and count, motility, and morphology.
During microscopic examination, WBCs must
be differentiated from immature sperm (spermatids).
Factors Affecting Motility Analysis
Urine is toxic to sperm, thereby affecting evaluation of motility.
Semen Liquefication
- A fresh semen specimen is clotted and should liquefy within 30 to 60 minutes after collection
- Failure to liquefaction after 60 minutes may be caused by a deficiency in prostatic enzymes
- If liquefication hasn’t occured after 2 hours, an equal volume of physiologic PBS or proteolytic enzymes such as alphachymotrypsin or bromelain may be added to induce liquefaction
Semen Volume
Normal volume: 2 - 5 mL
Decreased volume: associated with infertility and may indicate improper functioning of one of the semen producing organs, primarily the seminal vesicles.
Semen Viscosity
Droplets that form threads longer than 2cm are considered highly viscous and abnormal.
Semen pH
- The pH of semen indicates the balance between the acidic prostatic secretion and the alkaline seminal vesicles secretion.
- The pH should be measured within 1 hour of ejaculation due to the loss of CO2 that occurs.
- The normal pH of semen is alkaline with a range of 7.2 to 8.0.
- Increased pH: infection within the reproductive tract.
- Decreased pH: associated with increased prostatic fluid, ejaculatory duct obstruction, or poorly developed seminal vesicles.
Sperm Concentration and Count
- Total sperm counts >40 million per ejaculate are normal
- Counted diluted and placed in the Neubauer chamber
Preparation of Semen for Counting
- 1:20 dilution
- Dilution of the semen is essential because it immobilizes the sperm before counting.
- Diluting fluid contains sodium bicarbonate and formalin, which immobilize and preserve the cells
Sperm Motility
The percentage of sperm showing actual forward movement can then be estimated after evaluating approximately 20 high-power fields.
A minimum motility of 50% with a rating of 2.0 after 1 hour is considered normal
Sperm Morphology
Sperm morphology is evaluated with respect to the structure of the head, neckpiece, midpiece, and tail. Abnormalities in head morphology: poor ovum penetration
Abnormalities of neckpiece, midpiece, and tail: affect motility.
Head of Sperm
Oval-shaped head approximately 5 µm long and 3 µm wide and a long, flagellar tail approximately 45 µm long
Enzyme-containing acrosomal cap located at the tip of the head is critical to ovum penetration. Encompasses approximately half of the head and two thirds of the sperm nucleus.
Sperm Neckpiece, Midpiece, and Tail
The neckpiece attaches the head to the tail and the midpiece.
The midpiece is approximately 7.0 µm long and is the thickest part of the tail - surrounded by
a mitochondrial sheath that produces the energy required by the tail for motility.
Sperm Morphology Evaluation
- Evaluated on a thinly smeared, stained slide under oil immersion.
- Staining can be performed using Wright’s, Giemsa, Shorr, or Papanicolaou stain
- Air-dried slides are stable for 24 hours.
- At least 200 sperm should be evaluated and the percentage of abnormal sperm reported.
- Parameters in evaluating sperm morphology include measuring head, neck, and tail size; measuring acrosome size; and evaluating for the presence of vacuoles. Kruger’s strict criteria.
Sperm Morphology Abnormalities: Head
- Double heads
- Giant and amorphous heads
- Pinheads
- Tapered heads
- Constricted heads
Sperm Morphological Abnormalities: Tails
- Doubled
- Coiled
- Bent
- Abnormally long neckpiece may cause the sperm head to bend backward and interfere with motility
Differentiating WBCs from Spermatids
Peroxidase-positive granulocytes are the predominant form of leukocyte in semen
By counting the number of spermatids or leukocytes seen in conjunction with 100 mature sperm, the amount per milliliter can be calculated
C = (N x S)/100
Sperm Vitality
Decreased sperm vitality: specimen has a normal sperm concentration with markedly decreased motility.
Vitality is evaluated by mixing the specimen with an eosin-nigrosin stain, preparing a smear, and counting the number of dead cells in 100 sperm using a brightfield or phase-contrast microscope.
Living cells are not infiltrated by the dye and remain bluish white, whereas dead cells stain red against the purple background
Seminal Fluid Fructose
Low sperm concentration may be from low
support medium produced in the seminal vesicles, which can be indicated by a low to absent fructose levels
Low fructose levels are caused by abnormalities
of the seminal vesicles, congenital absence of the vas deferens,obstruction of theejaculatory duct, partial retrograde ejaculation,andandrogen deficiency.
Fructose Levels and Testing
Normal level equal or greater than 13 µmol per ejaculate
Screened for the presence of fructose using the resorcinol test that produces an orange color when fructose is present
Antisperm Antibodies
- Can be present in both men and women, both partners can demonstrate antibodies, although male antisperm antibodies are more common.
- Detected in semen, cervical mucosa, or serum
- Possible cause of infertility; antisperm antibodies in a female subject results in a normal semen analysis accompanied by continued infertility.
Male Antisperm Antibodies
- Blood–testes barrier separates sperm from the male immune system
- Barrier can be broken following surgery, vasectomy reversal (vasovasostomy), trauma, and infection
- Antibodies can be suspected when clumps of sperm are observed during a routine semen analysis.
- Sperm-agglutinating antibodies cause sperm to stick to each other in a head-to-head, head-to-tail, or tail-to-tail pattern.
Tests for Antisperm Antibodies
Mixed agglutination reaction (MAR) test: Screening procedure to detect the presence of IgG antibodies, AHG binds simultaneously to both the antibody on the sperm and the antibody on the latex particles or RBCs, forming microscopically visible clumps of sperm and particles or cells
Immunobead test: A more specific procedure that
detects the presence of IgG, IgM, and IgA antibodies and demonstrates what area of the sperm (head,
neckpiece, midpiece, or tail) the autoantibodies are affecting
Microbiological Semen Tests
The most frequently preformed routine aerobic and anaerobic cultures are:
- Chlamydia trachomatis
- Mycoplasma hominis
- Ureaplasma urealyticum
Other Chemical Tests to Determine Sperm Viability
Levels of neutral α-glucosidase, free L-carnitine, glycerophosphocholine, zinc, citric acid, glutamyl transpeptidase, and prostatic acid phosphatase
Decreased neutral α-glucosidase, glycerophosphocholine, and L-carnitine suggest a disorder of the epididymis.
Decreased zinc, citric acid, glutamyl transpeptidase, and acid phosphatase indicate a lack of prostatic fluid
Sperm Viablity Prior to Collection
Motile sperm can be detected for up to 24 hours after intercourse
Nonmotile sperm can persist for 3 days
Sperm die off, leaving the heads for 7 days after intercourse.
Seminal fluid contains a high concentration of prostatic acid phosphatase, so detecting this enzyme can aid in determining the presence of semen in a specimen
Post-Vasectomy Testing
Finding viable sperm in a postvasectomy patient is not uncommon, and care should be taken not to overlook even a single sperm.
Specimens are routinely tested at monthly intervals, beginning at 2 months postvasectomy and continuing until two consecutive monthly specimens show no spermatozoa
Determining Presence of Sperm in Legal Cases
Detection of seminal glycoprotein p30 (prostatic specific antigen [PSA]), which is present even in
the absence of sperm.
