Rat Dissection Report 5i6c3b

Vertebrae Dissection – Questions

1. Our specimen was a rat, and it was a female. We know it is a female because a urogenital opening was visible between its legs, and it did not have testes. 2. Our specimen (rat) belongs to the Class – Mammalia and Order – Rodentia. 3. The scientific name for a rat is – Rattus norvegicus. 4. The digestive system of our specimen (rat) was very interesting. The liver was dark in colour and was located under the diaphragm. The liver looked like a flap, which was divided into four lobes: median lobe, left lateral lobe, right lateral lobe, and a caudate lobe. Just beneath the liver lays the stomach. It was curved, light in colour, and the esophagus pierced the diaphragm and ed the stomach. Underneath the stomach was the pancreas. Near the stomach was the small intestine. It was a slender curled tube. Which consisted of three parts: duodenum (first part that comes from the stomach, mostly straight), jejunum (second part of small intestine), and ileum (last part before the small intestine becomes the large intestine). On top of the small intestine was the large intestine, it resembled the stomach, but it was much bigger. The colon leads to the anus. The colon is also known as the large intestine and it has four parts: cecum (large flat sac located in the lower abdominal cavity), ascending colon (food travels up), transverse colon (short part parallel to diaphragm), descending colon (section of large intestine travels back down to rectum), and the rectum (final part of colon that leads to anus). 5. The most important organs in our specimen, the rat, are: (a) Anus – helps excrete feces, and urine (b) Bones – structural framework, protects internal organs from injury (c) Brain – controls various functions such as movement and allows thinking. (d) Ears – allows the rat to hear other rats (communication). They can also hear ultrasonic frequencies. (e) Esophagus – allows them to swallow food (f) Eyes – allows them to see food, predators, and where they are going (g) Heart – circulates blood throughout body (h) Kidney – salt and water balance, elimination of toxic wastes, makes urine (i) Large intestine – completes absorption, manufactures vitamins , formation of feces (j) Liver – produces essential enzymes for metabolizing nutrients, essential for filtering contaminants from the blood, converting wastes into a disposable form, essential vitamins and minerals stored. (k) Lungs – helps rat to breathe, carry out gas exchange (l) Mouth – allows rat to eat, and communicate (m) Nose – allows them to breathe, and smell (n) Rectum – stores and eliminates feces (o) Skin – cover and protect organs, protects against bacterial invasion, prevent water and

electrolyte loss, keeps tissues from drying out, helps with thermal regulation (p) Small intestine – digests and absorbs nutrients (q) Stomach – adds acid to break down food, aids in digestion of proteins (r) Tail – serves as heat loss organ, used for balance when climbing 6. Rats belong to the class mammalia because: (a) They are warm blooded (b) Feed their young with their milk from hidden mammary glands (c) Have fur (d) born alive Yes the internal dissection provides a clue that rats are mammals. The internal organs of a rat are very similar to humans. However, the external features help classify the rat as mammals based on their fur, and concealed mammary glands. 7. The rat had a vertebral column. It had holes, through which the spinal cord ran through. The main function of the vertebral column is to provide protection for the spinal cord. It was thin and white in colour. It ran through the rat’s neck, back, and tail. It had 7 “cervical vertebrae”, and the first two cervical vertebrae were modified to form a universal t for head movement. It also had 13 “thoracic vertebrae” to which its ribs were attached, behind it were 5 individual cylindrical bones called “lumbar vertebra”. There were 3 or 4 “sacral vertebrae” that were ed together to form the sacrum (triangular bone in the lower back formed from the fusion of vertebrae and placed between the two hipbones of the pelvis). The “sacrum” unified with the pelvic girdle. Rats also have 26 to 30 “caudal vertebrae” in their tail. 8. In our opinion the most interesting part of our dissection was: (a) Skinning the rat so we could see its muscles and tissues (b) Seeing its internal organs and the way they were laid out (c) Cutting open its stomach to see all the food (d) cutting open the rats four chambered heart to have a better understanding how it is from the inside and how a human heart would be (e) dissevering its head to see the vertebral column, and trying to locate its brain Overall every step of the dissection was very interesting, since we were acquiring knowledge about an animal that seems very small and simple. Yet we learned how complex its system is and how similar its internal organs are to humans. 9. Our dissection didn’t have many surprises since we had thoroughly researched about our specimen in the time given to us. However, when we were dissevering its head we felt that the spinal cord wasn’t that hard to cut through. We expected it to be more rigid and more solid, since it has the vertebral column protecting the spinal cord. 10. This dissection was very different compared to that of the squid for many reasons. Externally the squid had a slimy jelly like mantle which held most of the organs except for the mouth, beak

and eyes. It was much easier to cut through the mantle since it was a jelly like covering, but the rat was much more complex with muscles and tissues making it harder to cut through the skin. They both had eyes on sides of their head allowing them to see predators. However the squid had large bulging eyes with a transparent covering on top, whereas the rat has small eyes with eyelids to protect them. The squids mouth was located in between its tentacles and has a beak made out of chitin whereas the rat has a mouth with salivary glands, teeth, tongue, and an esophagus. The squid has a complex digestive system consisting of a stomach, from there the bolus moves to cecum for digestion, food goes to liver for digestion and solid waste is ed out of the rectum. Compared to the rat, whose digestive system is complex as well, but contains many more stages. The food es through the esophagus to the stomach, to small intestine where absorption happens, to large intestine, colon and then out through anus. They both have a very different heart. The squid has three small hearts which are orange in colour, whereas the rat has one 4 chambered heart. One major difference is that squids are invertebrates (lack a backbone), compared to a rat which a vertebrate (have a backbone). We had to cut through the backbone of a rat when we didn’t have to for the squid. Both of our specimen were females, but squid are oviparous, and rats are viviparous.

Done By: Harleen Pandher, Ekampreet Boparai, Simar Narwal, Dilkiran Grewal