science

We’ve moved!

In other on September 7, 2009 at 15:58

We’ve moved just down the road to: urinfo.wordpress.com

We thought the title fit better, and was easier to understand. However, we will continue to keep it interdisciplinary! So bookmark us, and subscribe to our RSS feed. That way you wont miss a thing!

‘Pumping Tissue’ – The Structure of Muscles

In human physiology on August 27, 2009 at 23:44

A vital part of the human body, the muscle enacts movement with the environment, as well as internal function in digestion, blood flow and respiration. The best example to understand muscle structure comes from the muscles that make us move.

These skeletal muscles are connected to the skeleton (with tendons). They form part of the mechanical system that moves the limbs and other parts of the body. The structure of a muscle is ordered in a decreasing hierarchy, best described alongside a diagram:

What's inside the biceps?

What's inside the biceps?

Skeletal muscles, such as the biceps above, are made up of many neighboring muscle-fiber bundles – bound together by connecting tissues. Each bundle contains a few single muscle fibers, which are cells with their own (multiple) nuclei – along a plasma membrane.

The muscle fibers themselves are made up of many parallel and elongated contractile threads known as myofibrils. These myofibrils are made up of two, even smaller, threadlike sub-units: thin filaments (consisting of coiled-up actin molecules [two] and two other regulatory proteins) and thick filaments (made up of many staggered myosin molecules) – together, these two polymers are grouped as myofilaments. (Campbell & Reece, 2005) Their organization is orderly, and repeated under a unit called ‘sarcomere’ – beginning and ending at each Z-line, as marked on the diagram (and microscope-image) above.

To summarize, another word for skeletal muscle is striated muscle, which is defined as “muscle tissue in which the contractile fibrils in the cells are aligned in parallel bundles, so that their different regions form stripes visible in a microscope [as in the photo above]. Muscles of this type are … under voluntary control”. (“Striated Muscle”, 2007) The contractile action of the muscle is controlled by an overlapping (and non-overlapping) and movement of the myofilaments.

References:
- Campbell, N.A., Reece, J.B. (2008) Biology, 8e Int’l. San Francisco: Pearson/Benjamin
Cummings.
- “Striated Muscle” (2007) New Oxford American Dictionary. Macintosh OS X Dictionary,
Version 2.0.2 (51.4).

Your Introduction to Fingerprinting

In forensic science on August 27, 2009 at 23:22

Fingerprints are a reproduction of the skin that appears on the palm side of fingers and thumbs in primates (humans included). The skin is organized into elevated friction ridges, which “appear to have evolved to assist in gripping”. (Bell, 2008, p.151)

There are two main premises that allow fingerprints to be used to identify individuals.

Firstly, formed before birth, the friction ridge pattern (or fingerprints) remains unchanged throughout the life of an individual (apart from growth, scarring/purposeful alteration). A fingerprints pattern arises from a layer in the skin (dermal papillae), which can survive even after death. (Jackson & Jackson, 2004)

Secondly, the ridge characteristics make individual fingerprints unique, and allow individualization with the probability of two matching prints at 1 out of 1 with 60 zeros. (Saferstein, 2004) Over the years, no two full prints have been found to be the same, (Jackson & Jackson, 2004) however, everyone has them.

To introduce, fingerprints can leave a trace upon contact with surfaces. Naturally, this is due to: the sweat that is released from the pores atop the ridges, present even after washing; and the oil that comes from touching oily skin (e.g. regions of the face). These prints are often accidently left by the perpetrators at the scene of a crime.

In most police forces around the world, it is common practice to record the fingerprints of  suspects and criminals. This is usually done through the use of inks, however, digital scans are also now being taken in the EU and US. Therefore, “due to recent advances in digital imaging, computer databases, and software, fingerprints can be cataloged and searched electronically”. (Bell, 2008, p. 151)

Putting fingers to faces

Putting fingers to faces

Once developed, the fingerprints from a crime scene are analyzed for possible matches. This can be performed with the aid of computer technology; however the final decision is made by the fingerprint analyst involved. Matches are identified according to uniqueness at certain points (minutiae). However, it should also be noted that in the UK, for example, there is no longer a minimum amount of minutiae needed for match (unlike the previous 16-point rule from 1953); the number of matching points needed to ascertain a match is at the discretion of the expert analyst, which can sometimes prove problematic.

Conclusively, “the technology associated with the collection of fingerprints is well developed, reliable and, in most cases, easily applied”. (Jackson & Jackson, 2004, p.35)

References:
- Bell, S. (2008) Encyclopedia of Forensic Science. New York: Facts On File, Inc.
- Jackson, A.R.W., Jackson, J.M. (2004) Forensic Science. Harlow: Pearson/Prentice Hall.
- Saferstein, R. (2004) Criminalistics: An Introduction to Forensic Science, 8e. New Jersey: Pearson/Prentice Hall.

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