Vesicles Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Vesicles and links to relevant pages within the course.
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| The microscopic features shown in this photomicrograph is of a fungus commonly associated with: | View Page |
| The bare fruiting heads shown here, characteristic of Aspergillus niger, demonstrate a spherical vesicle with phialides positioned around the entire circumference of the surface. The other Aspergillus species that also sporulates circumferentially is: | View Page |
| Semen is produced in which of the following organs? | View Page |
| Which of the following organs are normally involved in the production of semen? | View Page |
| Composition of Semen Semen is produced as a combination of secretions from the different regions of the male reproductive tract. Each fraction differs in chemical composition and function. The combination of these fractions during ejaculation results in the optimal environment for transporting sperm to the endocervical mucus in the female. Spermatozoa are produced in the testes. They mature in the epididymis. The testes also produce testosterone and inhibin.Fluid from the seminal vesicles accounts for approximately 70% of semen volume. The seminal vesicles are the source of fructose in semen. Fructose is used by the spermatozoa as an energy source.The prostate gland supplies about 20% of the volume of semen. Its fluids include acid phosphatase and proteolytic enzymes that lead to coagulation and subsequent liquefaction of semen. The prostate also contains most of the IgA found in semen.The bulbourethral gland produces mucoproteins that make up about 5% of the volume of semen. | View Page |
| Fructose Fructose makes up 99% of the reducing sugar present in semen. This sugar is produced in the seminal vesicles and its absence may indicate an obstruction proximal to these glands.
Although a fructose test is NOT part of a routine semen analysis, the clinician may want to measure this in cases of azoospermia. In azoospermia secondary to obstruction of the ejaculatory ducts or absence of the vas deferens, fructose is usually absent. When azoospermia is caused by failure of the testes to produce sperm, fructose is present. Measuring fructose levels can thus help the clinician determine the cause of azoospermia, although measurement of pH is often more useful in this regard.
The procedure for determining the amount of fructose in semen involves heating semen in a strong acid in the presence of resorcinol. Fructose gives a red color to this solution when present. | View Page |
| pH The pH of normal fresh semen is 7.0 or greater. Acid conditions can lead to reduced sperm motility and viability.Secretions of the different glands of the male reproductive tract contain fluids of different pH. The portion of semen that originates in the seminal vesicles is basic, that of the prostate gland is acidic. If the pH is low it could mean that there is an obstruction in the ejaculatory duct below the level of the seminal vesicles or it could signal absence of the vas deferens. Low pH is often associated with low volume since both basic pH and much of semen volume are products of the seminal vesicles. Measuring pH can thus help a clinician determine the cause of azoospermia (absence of sperm in semen).The pH is measured using pH testing strips. A drop of semen is placed on a pH strip and allowed to develop full color. Final color is compared to a standard. For the most accurate results, use test strips with a sensitivity in the basic range, for example from 6.0 to 10.0. | View Page |