Formal Practical Report

Formal Practical Report
Tittle: Rat dissection
Date: 16/10/2013
Partners: Sanketh Yadav and Joel Chittiprolu 8C Aim: To investigate the rat’s digestive system and compare the differences and similarities of the organs with the Human’s digestive system and measure them.
Materials/ Equipment:
Lab court
Nitrile Safety Gloves
Camera or Phone to take pictures
Scissors
Probe
Scalpel
Rulers
Nails
Bench
Plastic bag for excreting waste
Eucalyptus
Room spray
Newspapers for keeping dissection area clean
Chopping board
Hand wash liquid
Rat
Method:
1. The lab coat and the Nitrile Safety Gloves were worn for safety purposes.
2. A bundle of newspaper was taken and layered on the table and chopping board to keep the table and chopping board clean.
3. Then a rat was taken and placed on the chopping board. 4 nails were used to hammer on each leg of the rat to stop any movement of the rat when dissecting.
4. A small section of the fur (skin) was grabbed by forceps and cut with the scissors. Then the scissors were inserted and the skin and was gently cut through in a double YY shape as illustrated on the image to the right. Do not forget that when the rat’s fur is been cut out in this shape shown in the right hand side, as the fur is been cut in this shape it should be gently taken out so that the interior organs would not get destroyed or spoilt and even when the fur is cut out in double Y shape the scissors should not lean down but it should be tilted upwards when cutting the skin of the rat’s body.

5. After cutting the rat’s fur in double Y shape, a scalpel was taken and the skin was slightly removed in such a manner that the rat’s muscular part would never get tear. WARNING Remember that if the muscular part of the rat gets cut when removing the fur apart; it is going to smell bad.
6. After removing the fur (skin) off the rat, some nails are taken and hammered the skin of the rat apart from the body so that it won’t give any trouble when measuring and observing the interior system of the rat’s body that includes liver, heart, lungs, small intestine, large intestine, secrum bag, urinary bladder, oesophagus, van cava trachea, stomach and etc.
7. After hammering the skin of the rat apart, a scalpel is taken and carefully cut the muscular part of the rat so that the interior parts would not get destroyed or spoiled and it should be as the picture indicated below. 8. The organs were now visible to see and the organs include liver, small intestine and large intestine but the rest of the organs were visible below these organs. Eucalyptus and room spray was used if there was any unbearable smell around the dissecting environment and the rat should be like the indicated below

9. Then the organs that was visible on the top was taken out so that the rest of the below organs was visible. Then the ruler was taken to measure all the organs one by one and the measurements were noted down in the work book. Pictures of the dissected rat were taken by Phone and Camera so that it would help in some other manner.
10. After all the organs of the rat’s body was measured, the nails off the chopping board was safely taken out and wrapped the dissected rat with the newspaper that was layered on the table and chopping board and was disposed in a plastic bag so that it Was ready to be thrown.
11. After disposing the rat in the bin, a hand wash liquid was taken to was hands so that there would be no smell existing in our hands as there are many bacteria in the hand when the dissection and there are also many chemicals in organs example stomach, caecum, kidney and intestine that makes the hand smell bad even though the Nitrile Safety Gloves is worn for safety. After the hands is washed hands and cleaned, the lab coat is placed where it was taken and the Nitrile Safety Gloves is thrown to the dust bin so that it is not used again as it is dangerous to use it again.

Results: We measured the rat’s organs when we were dissecting it and the measured results were compared with the human’s organs.

Dissected rat’s organs measurement result Organs name Measurements of organs
1. Stomach
4cm
2. Small intestine
113.5cm
3. Large intestine
19cm
4. Liver
4.5cm
5. Caecum
4cm
6. Heart
2.5cm
7. Lungs
2.9cm
8. Kidney
1.5cm
9. Trachea 2.2cm
10. Oesophagus 4cm

Dissected human’s organs measurement
Organs name
Measurements of the organs
Oesophagus
35 cm
Stomach
20cm
Small intestine 600cm
Large intestine 150cm
Liver
30cm wide – 15cm length and weigh about 1,560 gram
Heart
8cm long

Discussion Questions:
Q1.) Describe the teeth of the rat you dissected. What do the teeth tell you about what rats eat?
ANS: Rats have incisors and molars. Incisors are the front most teeth in animals. In rats, these are the four, long, sharp front teeth, two on top and two on the bottom. Rat incisors are highly specialized for gnawing. They are open-rooted, which means they grow throughout life. From this we can say that Rats eat a wide variety of food. They have various appetites and will eat almost anything. They are true omnivorous scavengers, but mostly prefer grain, livestock feed, and meat. Rats have also been known to eat soap, leather, furs, candy, milk, meat, vegetables, poultry, eggs, grain, seeds, fruit, nuts, snails and other rodents. They have two pairs of incisors and six pairs of molars as the incisors are used to cut and grab the food they eat and the molars are used to grind and crush the grabbed food. A rat can eat one third of its body weight each day. The rat's main important consumption is water, as it cannot survive long without water. Rats need 1/2 to 1 ounce of water daily.

Q2.) How are the rat’s teeth different to human teeth? Find a diagram to help you explain.
Ans: Rats have two types of teethes and they are incisors and molars. They have two pairs of incisors and six pairs of molars as the incisors are used to cut and grab the food they eat and the molars are used to grind and crush the grabbed food. Whereas, in humans they have two pairs of canines, two pairs of incisors, four pairs of premolars and eight pairs of molars. The incisors are used to grab the food, canines are used to tear the food, premolars and molars are used to break down, chew and grind the food. Thus, these are the difference between a human and a rat teethes.

Q3.) List the route travelled by food in the rat from the mouth to the anus?
Ans: In the rat’s body the food travels from Mouth Oesophagus Stomach Small intestine Caecum Large intestine rectum Anus Toilet pit (EXTRA not included in any book). Food travels in this way in rat’s digestive system but it is different in human’s digestive system.
Q4.) What is peristalsis? Explain its role.
Ans: The muscle of the oesophagus push bolus that was chewed by mouth down the tube by contracting behind the bolus and relaxing in front bolus to allow or give a path way to the bolus to reach the stomach. This process of contracting and relaxing to allow the bolus to reach the stomach is called as peristalsis and this process is as tough as pushing the air of a thick tyre.

Q5.) Would the route be the same in humans? Explain.
Ans: No, the route travelled by food would not be the same in humans comparing to rat because humans do not have caecum which is used for digestion of high fibre materials (plant material), and often serve as storage zones for cellulose digesting bacteria.
Q6.) What is the function(s) of each of the following parts of a rat digestive system: stomach, large intestine, small intestine, Caecum and rectum?
Ans: 1. Stomach: The stomach's main function is digestion. It does this by: •Storing the food we eat.
•Breaking down the food into a liquidly mixture called chyme.
•Mixing enzymes which is are chemicals that break down food and this chemical is called as pepsin.
•Slowly empties that liquidly mixture into the small intestine. The stomach uses pepsin (enzyme) and peptidase (another enzyme) to break down proteins in the food we eat. The acid released by the stomach doesn't break down food it only provides a good environment for the enzymes to work in. By this point the food is squashy and mushy and the stomach then passes this mixture on to the small intestine which will further break down the food. The stomach mixed the food with stomach acid to break it down and digest it. 2. Large intestine: The function of the large intestine is to transport the waste and re-absorption the water from the food before the food is excreted. When proper metabolism (the process of extracting the nutrients from food) has taken place the waste is usually in solid form that means the faeces become solid. 3. Small intestine: Small intestine is a long tube like structure where most nutrients are absorbed from the food products and these nutrients are absorbed into the bloodstream. Small intestine is also known for breaking down of food enough to pass through to the large intestine if it is not grumbled and crushed properly by the stomach.

4. Caecum: Caecum is a storage zone or storage bag of food that comes out of the small intestine. Caecum is very important to herbivores because they eat lot of grass and plants so caecum is the best for storing plants and extract their nutrients because small intestine cannot extract all nutrients that exist in plants because the plants are hard and strong to extract and the small intestine is not strong enough to extract all the nutrients from the plants that is taken in.

5. Rectum: The rectum has a main function of storing faecal matter temporarily before it is removed from the body and excreted through the anus. The muscular walls of the rectum expand to hold faecal matter as the nerves in this area send signals to the brain for bowel movement to occur and when the faeces are ready to get excreted by the body and all the water and nutrients are absorbed. A ring shaped muscle called sphincter expand and the faeces get excreted out of the body. Q7.) What is the function of sphincters? How do they help with digestion?
Ans: A sphincter is a ring shaped muscle that is located in the beginning of the stomach; end of the stomach and in the end of the anus. The first sphincter in top of the stomach helps the food not letting out of the stomach as it comes in through the oesophagus. The second sphincter in the end of the stomach avoids the food not letting into the small intestine until the food is crumbled, churned and digested by using an enzyme called pepsin. The third sphincter in end of the anus helps the faeces not get excreted until it is ready to be excreted. Sphincter helps in our digestion as if there wasn’t a sphincter in the beginning of the stomach, then the food that was not getting digested and we would then have to ruminate (chew their cud) our food and the food would not get digested. If there wasn’t a sphincter at the end of the stomach, then the food could not be digested and broken down properly in the stomach. The sphincter is definitely needed at the end if the anus as if there wasn’t a sphincter here then the digested food turned into faeces then had been loosened and would have flown all over the way wherever we walked. So, from this we can say that sphincter helps in our digestion. Q8.) What advantages is there to the rat having such a long, small intestine?
Ans: The advantages for rats having a long small intestine are:
1. There is enough time for the small intestine to absorb all the nutrients required.
2. It enhances the property of surface absorption etc.
Q9.) What is the difference between chemical and physical digestion?
Ans: Physical digestion is just the breaking down of food by physical means like chewing, churning and gnawing.
Chemical digestion is where enzymes like pepsin, bile and other substances are involved in the process of breaking down of food substances.
Physical digestion happens in the mouth when the food is chewed by teethes.
Chemical digestion happens throughout the digestive system up to the small intestine. Which means it does not include the large intestine and anus.
Q10.) Where in the digestive system does chemical and physical digestion occur?
Ans: 1. Chemical digestion occurs in mouth when the saliva gets mixed with the chewed food. It occurs in liver where it produces bile for the breakdown of fats and converts it to glucose (sugars) to glycogen (stored sugar) filters harmful substances from the blood such as alcohol storage of vitamins and minerals (Vitamin A, D, E, & K) responsible for producing cholesterol. Liver produces about 80% within the body. Chemical digestion also occurs in stomach when an enzyme called pepsin hydrochloric acid and pancreatic juices that contain sodium hydrogen carbonate which neutralizes the acidity caused by HCL, these are in stomach to break down the food we’ve eaten. The chemical digestion also occurs in small intestine as pancreatic lipase is one of the enzymes and it is used to break down triglycerides into free fatty acids and monoglycerides. Pancreatic amylase is another one and it breaks down carbohydrates into oligosaccharides. Proteolytic enzymes such as trypsin and chymotrypsin in the pancreas degrade proteins into smaller peptides. Carboxypeptidase a brush border enzyme from pancreas degrades one amino acid. Amino peptidase and dipeptidase are the enzymes required to free the end amino acid products.
2. Physical digestion occurs in mouth as the food is chewed and grinded in the mouth by teethes but chemical digestion also occurs in mouth as the saliva gets mixed with food. Physical digestion occurs in the stomach as the food is churned in here but chemical digestion also occurs here as the enzymes like pepsin is used to break down the food in the stomach. Physical digestion occurs in large intestine as the large intestine is a mechanical digesting system; it absorbs water and is involved in peristalsis. It has nothing to do with enzymes, which is involved in chemical digestion. Physical digestion also occurs in the anus as the faeces get disposed from the body when the sphincter expands and contracts, and this motion is physical.
Q11.) Why does the rat need a digestive system?
Ans: Rats need digestive system because to get right nutrients to their cells, tissues and organs from the food they have eaten and to get rid of the waste in their body. If there was no digestive system to rats then they would not live longer as the nutrients in their food they have eaten would not be distributed to their cells and tissues as the cells and tissues becomes dead if there is no proper nutrients supplied to them.
Q12.) Is the koala, the Caecum is 2m long. What advantage would such a long organ give the koala and other herbivores?
Ans: The advantages for Koala’s of having 2m long caecum is that if they eat any plants and leaves that are hard poisonous as the Koala’s eat Eucalyptus leafs which are very hard and strong to chew and digest and also poisonous so, having a caecum of 2m long may give them enough time to extract the nutrients, digest the hard and strong leafs and get rid of the poison in that leaf. This advantage also goes with the other herbivores also.

Conclusion: I learnt that the rats have slightly different digestive system comparing to human digestive system and even the measurements of organs will also be different, and I also learnt that the rats do not have premolars and molars types of teethes in their mouth. By,
Sanketh 8C

http://answers.yahoo.com/question/index?qid=20100902041536AAoXMTh

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