Nephron: The basic structural and functional unit of the kidney.
Glomerulus: It is formed by a network of capillaries and is surrounded by a Bowman’s capsule.
Filtration is the first step in urine formation.
During the reabsorption process, water, glucose, nutrients, and ions such as sodium are reabsorbed back into the blood.
Secretion: It is the last process of urine formation. It occurs at the distal and the collecting tubules of the nephron where ions ammonia, and certain metabolites are secreted from the blood into the lumen of the renal tubule to be eliminated in the urine.
Urine: An aqueous solution consisting largely of water and waste products.
Urea: The most abundant waste product in urine, resulting from the elimination of ammonia that is produced from the metabolic process of amino acids.
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The para-dimethylaminocinnamaldehyde (DMAC) assay is simple and rapid and is the most commonly used presumptive assay for the forensic identification of urine stains.
In the colorimetric method, a portion of a stain (~1 cm2) is cut and is extracted with 1 mL of distilled water. The extraction is transferred onto a piece of filter paper and is allowed to dry.
The fluorometric method is useful for locating urine stains on large pieces of evidence such as clothing and bedding.
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Androsterone: A steroid hormone with a weak potency of testosterone.
DHEA: A metabolic intermediate in the biosynthesis of the gonadal steroids. It also has a potential function as a steroid hormone.
Etiocholanolone: A metabolite of testosterone.
Eccrine sweat glands: Are distributed almost all over the body and are controlled by the sympathetic nervous system. It plays a role in regulating body temperature.
Apocrine sweat glands: Are associated with hair follicles, are usually restricted to the underarm and genital areas and are controlled by emotional stress.
Sweat evidence has been analyzed using presumptive assays such as elemental analysis using scanning electron microscopes coupled with energy dispersive x-ray spectroscopy in the detection of lactic acid.
Raman microspectroscopy is potentially useful for the identification of sweat for forensic purposes, which is based largely on the profiles of lactate, lactic acid, urea, and single amino acids in urine.
Dermcidin: Identified as a potential biomarker of human sweat. It belongs to a class of human antimicrobial peptides of the innate immune defense system and plays an important role in protecting epithelial barriers from infections.
The detection of dermcidin in sweat stains can be performed using ELISA assays utilizing antibodies specific to human dermcidin.
Dermcidin is encoded by the DCD gene. Its mRNA can be detected using reverse transcription polymerase chain reaction (RT-PCR) assays that can detect DCD mRNA in 10 ìL of sweat sample.
Feces: Are a type of waste matter that is the direct result of food that has been processed by the digestive system.
Human feces contain undigested foodstuffs, sloughed intestinal epithelial cells, intestinal bacteria, bile pigments, electrolytes, and water.
Feces are formed in the intestines during the last phase of digestion. Feces first enter the colon in liquid form.
Most of the nutrients are absorbed on the surface area of the small intestine. In the large intestine, water, sodium, and chloride are absorbed on the surface of the lumen.
Food stays for approximately 2–6 h in the stomach. It takes an additional 3–5 h to travel through the small intestine and 12–24 h to travel through the large intestine.
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Macroscopic and Microscopic Examination
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Urobilinoids Tests
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Gastric fluid can be found in stains derived from stomach wounds.
Vomiting: The forceful expulsion of the contents of the stomach through the mouth. It is usually preceded by salivation, sweating, and the sensation of nausea.
Vomiting usually begins with a deep inhalation and the closure of the glottis.
The stomach stores ingested food until it can be emptied into the small intestines.
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