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Forensic semen analysis
Forensic semen analysis
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  1. 1. SEMEN AND ITS ANALYSIS Submitted to Dr. Priyanka Verma Submitted by Apurba - 20MFS1110 Sreya Dharan - 20MFS1111 Aathmika - 20MFS1112
  2. 2. What is semen? Semen, also known as seminal fluid, is an organic fluid that may contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize female ova. In humans, seminal fluid contains several components besides spermatozoa: proteolytic and other enzymes as well as fructose are elements of seminal fluid which promote the survival of spermatozoa, and provide a azmedium through which they can move or "swim". Semen is produced and originates from the seminal vesicle, which is located in the pelvis. The process that results in the discharge of semen is called ejaculation. Semen is also a form of genetic material.
  3. 3. The mammalian sperm cell can be divided in 4 parts: head: it contains the nucleus with densely coiled chromatin fibres, surrounded anteriorly by an acrosome, which contains enzymes used for penetrating the female egg. It also contains vacuoles. neck: it contains one typical centriole and one atypical centriole such as the proximal centriole like. midpiece: it has a central filamentous core with many mitochondria spiralled around it, used for ATP production for the journey through the female cervix, uterus and uterine tubes. tail or "flagellum": it executes the lashing movements that propel the spermatocyte.
  4. 4. Semen analysis: Semen analysis is the examinations of ejaculated seminal fluid found at crime scene. Seminal fluid is a viscous, turbid fluid produced mainly from secretions of seminal vesicles (45-80% of volume) and prostate gland (15-30% of the volume ). About 10% of the total volume is the combined mixture of the epididymis glands and bulbourrethal glands . An average male ejaculate measures around 3.5 ml each ejaculation. Each milimetre can contain between 10 – 50 milion of sperm cell . This numbers can vary with the age of the male, and can be negatively impacted by the medical conditions , genetic background ,diet, habit of smoking and use of illicit drugs .
  5. 5. Analysis of semen: To naked eye seminal stains generally appear translucent or opaque spots, at times with yellowish tint and darker border depending on colour and thickness of substrata, which, if absorbent, also acquire stiffness due to dried semen. Semenial stains are usually starchy when touched.
  6. 6. The acid phosphatase reaction is a typical test in which the suspected seminal stain or an extract of it on a filter paper is reacted with a solution of the substrate, a monophenolic phosphoric acid or its ester, in acetate buffer of pH 5. A negative reaction means the absolute absence of semen.
  7. 7. Christmas tree stain test: Two main reagents are used consecutively to produce this distinctive stain: Picroindigocarmine stains the neck and tail portions of the sperm in green and blue, while Nuclear Fast Red (also known as Kernechtrot) gives the sperm heads a red color and the tips of the heads, an area known as acrosomal cap, a pink color. Although this color pattern seems quite unique and may render sperm cells easily distinguishable under a microscope, sperm cells tend to deteriorate quickly after ejaculation.
  8. 8. p30 test: p30 is a presumptive test for the presence of human prostate- specific p30 protein found in seminal fluid. The p30 test works through an antigen-antibody reaction. Antibodies are present on the p30 card and if the antigen is present (p30 protein) in a sample, then a reaction occurs on the test site (T) of the card.
  9. 9. Florence test: • Basis: Choline is detected in this method. • Procedure: A few drops of watery solution of the stain is extracted and taken on a slide and a drop of Florence reagent (8%) W/V solution of Iodine in water containing 5% W/V of Potassium Iodide) is poured & allowed to mix slowly under a cover slip. Dark brown crystals of choline periodide, generally needle shaped, formed with a few minutes. Non-specifics & false negative results are common.
  10. 10. Barberio's test: • Basis: Detection of Spermine • Procedure: A few drops of Berberio’s reagent when added to spermatic fluid produces crystals of sperm in picrate (needle shaped, rhombic & of yellow colour). • For various valid reasons, like non-specificity and lack of reproducibility, the florence and berberio’s tests have not been accepted universally.
  11. 11. References: • Arvind Singh, Sushila Singh and Teotia, Semen Analysis, Research News, Vol. 6, 2012. • Richard Li, Forensic Biology: Identification and DNA Analysis of Biological Evidences(2008).
  12. 12. THANK YOU :)

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