Date: January 30, 2015
Tutor: Karen Keenan
Name: Hanin Abdullah
Introduction
“A model system is a simpler, idealized system that can be accessible and easily manipulated (Rosenblueth & Wiener, 1945)”
A model or laboratory organism is a non-human species that are widely and thoroughly experimentally studied to comprehend biological phenomena and provide an insight into how organisms work internally. They can be used in research regarding human diseases, drugs, metabolic and genetic developments, and to obtain data about humans that would be difficult to study directly.
“There is a wide range of characteristics common to model organisms, including: 1) rapid development with short life cycles, 2) small adult size, 3) ready availability, and 4) tractability (Bolker, 1995)” In addition to that, certain organisms have been chosen as model organisms due to their relativity to human bodies. All these factors are all present in rats with over 95% of its genomes similar to the human genome. Rats in laboratory research can help, especially in the pharmaceutical industry, in discovering drug efficiency on human diseases and identification of genetic risk factors. Along with learning and exploring more about biology concepts concerning the human body, studying these organisms can help scientist discover new treatments for current diseases in humans like cancer.
The aim of this practical is to observe and discern the anatomy of mammals and to gain a better comprehension of how biological systems work in the body.
Experiment
I. Rat Dissection
Figure 1 - Rat with surface facing up on the dissection pan held by strong pins ready for dissection.
Figure 2 – The Abdominal Cavity
The first incision was in mid-ventral line of the rat. The skin was then cut horizontally along this line and removed carefully from the insides without damaging or tearing any nerves of muscles. The second incision was perpendicular to the first and right below the diaphragm. Because of this technique, abdominal cavity first was opened first.
Figure 3 – The digestive system intact to the rat’s body.
Figure 4 – The digestive system solely
The central area of the rat, separating the thoracic cavity from the abdominal cavity was quite flexible in structure. The liver seems to be the prominent organ and it is inferior to the diaphragm, dark brown with several lobes. Inferior to the liver and stomach is the pancreas that is light brown in colour and long in size. The duodenum is whitish in color with a long, flat appearance. Seeing that it is connected from below to the small intestine, most chemical digestion occurs in it. It also precedes the ileum and jejunum where their walls are made up of folds and projection; thus, they mainly are responsible for the absorption of the substances.
Another organ worth pointing is the caecum. This organ mostly exists in herbivores because they are areas for digestion of high fiber materials like plants (plant material), and often serve as storage zones for cellulose digesting bacteria. It is kidney shaped, similar to the stomach, but darker in colour.
Figure 6 – The abdominal cavity of the rat after removing the digestive system, displaying the urinary system eminently.
Figure 7 – Close up of urinary and reproductive systems of the rat detached (left) attached to the rat’s body (right).
The picture on the right displays the female reproductive system with the ovaries, uterus, and vagina, while the picture on the left is a male. The male reproductive system does not seem to be very clear here, but a noticeable difference would be that vesicular glands are often only located in male mammals. Vesicular glands secrete fluids contains proteins, enzymes, fructose, and much more, this fluid eventually becomes
