Biology Overview Dissection Assignment

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Drusilla Bryan
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1 Biology Overview Dissection Assignment What is this assignment about? After learning several major systems of the human body, this overview dissection assignment is for you to review all of those major systems in a rat via dissection. How should you approach this assignment? ü Read all of the info carefully before you start ü Take your time and be detailed. ü You have 4 periods to work on this. READ ALL OF THE INFO CAREFULLY BEFORE YOU START! ü Work with a partner who shares similar work ethics as you. Systems we have studied and should be included in your dissection lab book: ü Cardiovascular unit (heart, major blood vessels, and circulation) ü Urinary system (excretion) kidneys, bladder, ureters, urethra ü Digestive system entire alimentary tract from mouth, oral cavity, larynx, esophagus, small intestines, large intestines, liver, pancreas, and others. ü Respiratory system lungs, diaphragm, and oral cavity. ü Homeostasis overall, how does the rat regulate its body (temperature, food, nutrient absorption, gas exchange) when all these systems work together. CLEAN UP BY WASHING AND DRYING ALL OF YOUR DISSECTION KITS. PLACE YOUR RAT IN A ZIP LOC BAG

The rat (and all vertebrates) has anatomical regions to help locate structures.

2 Rat Dissection! Put your gloves on! Rats may be bloated from the chemicals, so be careful when making the first incision. 1st stage: Identifying the exterior Examine your rat Place your rat in a dissecting tray and examine the external features. The rat (and all vertebrates) has anatomical regions to help locate structures. ü cranial region head cervical region neck ü pectoral region - area where front legs attach ü thoracic region - chest area abdomen belly ü pelvic region - area where the back legs attach Step 2: Locate the vibrissae (whiskers) and the pinna (ears). Rats are gnawing mammals and two large incisors should be visible. Eyes are usually pink or black with a black pupil and covered by a nictitating membrane. The sex of the rat can be determined by looking for external testes, found on males and the presence (or absence) of teats, which are only found on female rats. Female rat, urogenital opening visible between legs.

3 Draw: Draw (or you can take a picture, print it out and glue it onto this page) the cranial region of your rat and label the following: Pinna, vibrissae, eyes, incisors, Draw (or you can take a picture, print it out and glue it onto this page) the entire body of your rat with the belly facing up. Label the following: Cranial region, pectoral region, pelvic region, thoracic region, external testes (if male), or urogenital opening

You can start at the incision point where the latex was injected and continue toward the tail.

4 2nd stage: Skinning and revealing the muscles of the rat. You will carefully remove the skin of the rat to expose the muscles below. This task is best accomplished with scissors and forceps where the skin is gently lifted and snipped away from the muscles. You can start at the incision point where the latex was injected and continue toward the tail. Use the lines on the diagram to cut a similar pattern, avoiding the genital area. Gently peel the skin from the muscles, using scissors and a probe to tease away muscles that stick to the skin. Remove the skin of the rat to expose the muscles on both sides of the rat (belly and back).

5 Draw: Draw (or you can take a picture, print it out and glue it onto this page) a side overview diagram of the rat with the muscles exposed. Label the following: biceps brachii, triceps brachii, external oblique (stomach muscle), latissimus dorsi (back muscles).

3 rd stage: Exposing the head and neck region 1. Make small incision along the neck region and cut through the muscles up the neck while carefully not damaging the glands below.

6 3 rd stage: Exposing the head and neck region 1. Make small incision along the neck region and cut through the muscles up the neck while carefully not damaging the glands below. Locate the salivary glands, which on the sides of the neck, between muscles and the external layer of skin. They are soft spongy tissue that secrete saliva and amylase (an enzyme that helps break down food). The texture of these glands resembles chewing gum. There are three salivary glands - the sublingual (left pin), submaxillary (right pin), and parotid (middle pin). The parotid is easiest to find, it lies just beneath the ear and extends to the neck. See if you can find the others also. Tear away the muscles of the neck to reveal the trachea. The trachea is identifiable by its ringed cartilage which provides support. The esophagus lies behind the trachea, but can be difficult to locate in this area. Locate the larynx, which is just anterior (closer to the head) to the trachea. The larynx is the voice box, and allows rats to make squeaking noises.

7 Questions about the digestive system: 1. What is the enzyme that is responsible for breaking down starch into sugar in the mouth? 2. What is the difference in function between trachea and the esophagus? 3. What type of muscles and cells line the digestive tract? 4. What enzymes are found in the stomach? What do they digest? 5. What does the stomach absorb?

8 6. What is the primary function of pancreatic juices? 7. Identify the basic structures for proteins, carbohydrates, and lipids. What functions do they each have?

9 4 th stage: Exposing the internal organs Procedure: Cut through the abdominal wall of the rat to expose the internal organs. Be careful not to cut too deeply and keep the tip of your scissors pointed upwards. Do not damage the underlying structures. Once you have opened the body cavity, you will need to rinse it in the sink. 1. Locate the diaphragm and the heart is centrally located in the thoracic cavity. The thymus gland, may be visible at the upper part of the heart. 2. The lungs are spongy organs that lie on either side of the heart and should take up most of the thoracic cavity. They lie closer to the back of the rat, you will need to push the ribs to the side to find them. 3. A sheet of muscle can be found just under the heart (and above the liver) - this is the diaphragm. This muscle is only found in mammals. (The diaphragm may have been cut when you opened the thoracic cavity.) Your task Cardiovascular system Locate the heart and cut away any fat that is outside of the heart. Locate the aorta and identify any major arteries and veins that are coming in and out of the heart such as: Aorta, vena cava, carotid artery, and jugular vein (close to the neck).

10 Draw: Draw (or you can take a picture, print it out and glue it onto this page) the heart region of the rat and label the following: Right atrium, right ventricle, left atrium, left ventricle, aorta, vena cava, and apex of the heart. Cut the heart with a cross cut (like opening an oyster) and label the following: You may cut the heart out for this Right atrium, right ventricle, left atrium, left ventricle, aorta, any valves

into an anterior and posterior lobule, hidden from view by the median lobe caudate lobe - small and folds around the esophagus and the stomach, seen most easily when stomach is raised 2.

11 5 th stage: Digestive system & accesory organs 1. Locate the liver, which is a dark colored organ suspended just under the diaphragm. It has four lobes: median or cystic lobe - located at the top, there is an obvious central cleft left lateral lobe - large and partially covered by the stomach right lateral lobe - partially divided into an anterior and posterior lobule, hidden from view by the median lobe caudate lobe - small and folds around the esophagus and the stomach, seen most easily when stomach is raised 2. Find the stomach, it s a curved organ lying just under the liver. At the top of the stomach you can see the esophagus where it pierces the diaphragm and joins the stomach. Lifting the stomach up may reveal a bumpy glandular organ: the pancreas. 3. The spleen is about the same color as the liver and is attached to the greater curvature of the stomach. 4. The small intestine is a slender coiled tube that receives partially digested food from the stomach (via the pyloric sphincter). It consists of three sections: duodenum, jejunum and ileum, (Listed in order from the stomach to the large

12 intestine.) The duodenum is recognizable as the first stretch of the intestine leading from the stomach, it is mostly straight. The jejunum and ileum are both curly parts of the intestine, with the ileum being the last section before the small intestine becomes the large intestine. 5. Locate the colon, which is the large greenish tube that extends from the small intestine and leads to the anus. The colon is also known as the large intestine and it consists of four sections: ü cecum - large flattened sac in the lower third of the abdominal cavity, it is a deadend pouch and is similar to the appendix in humans. ü ascending colon food travels upward. ü transverse colon a short section that is parallel to the diaphragm ü descending colon the section of the large intestine that travels back down toward the rectum. ü rectum - the short, terminal section of the colon that leads to the anus. The rectum temporarily stores feces before they are expelled from the body.

13 Draw: Draw (or you can take a picture, print it out and glue it onto this page) the digestive region of the rat: ü Liver, stomach, pancreas, small intestine, spleen, rectum, cecum, diaphragm

14 6 th stage: Urinary system 1. The primary organs of the excretory system are the kidneys. These organs are large bean shaped structures located toward the back of the abdominal cavity on either side of the spine. Renal arteries and veins supply the kidneys with blood. 2. Locate the delicate ureters that attach to the kidney and lead to the bladder. Wiggle the kidneys to help locate these tiny tubes. Procedure: Remove a single kidney (without damaging the other organs) and dissect it by cutting it longitudinally. Locate the cortex (the outer area) and the medulla (the inner area). 3. The urethra carries urine from the bladder to the urethral orifice (this orifice is found in different areas depending on whether you have a male or female rat). 4. The small yellowish glands embedded in the fat atop the kidneys are the adrenal glands.

15 Draw: Draw (or you can take a picture, print it out and glue it onto this page) the excretory pelvic region of the rat: ü Bladder, ureters, and urethra (if possible), and cross section of kidneys (on half the page), cortex, medulla, and pelvis,

Bonus last stage reproductive organs The Reproductive Organs of the Male Rat 1. The major reproductive organs of the male rat are the testes (singular: testis) which are located in the scrotal sac.

The tubular vas deferens moves sperm to the urethra, which carries it though the penis and out the body. 2.

16 Bonus last stage reproductive organs The Reproductive Organs of the Male Rat 1. The major reproductive organs of the male rat are the testes (singular: testis) which are located in the scrotal sac. Cut through the sac carefully to reveal the testis. On the surface of the testis is a coiled tube called the epididymus, which collects and stores sperm. The tubular vas deferens moves sperm to the urethra, which carries it though the penis and out the body. 2. The lumpy brown glands located to the left and right of the urinary bladder is the seminal vesicles. The gland below the bladder is the prostate gland and it is partially wrapped around the penis. The seminal vesicles and the prostate gland secrete materials that form the seminal fluid (semen). #2 = testis #5 = penis The Reproductive Organs of the Female Rat 1. The short gray tube lying dorsal to the urinary bladder is the vagina. The vagina divides into two uterine horns that extend toward the kidneys. This duplex uterus is common in some animals and will accommodate multiple embryos (a litter). In contrast, a simple uterus, like the kind found in humans has a single chamber for the development of a single embryo. 2. At the tips of the uterine horns are small lumpy glands called ovaries, which are connected to the uterine horns via oviducts

17 Reference Pages:

19 GRADING: DISSECTION DRAWINGS: 1. Cranial Region: /5 2. Overview of rat: /5 3. Muscles: /5 4. Questions about digestive system: /10 5. Heart Region: /5 6. Cross section of heart: /5 7. Digestive region: /5 8. Pelvic region: /5 Rubric for dissection drawings: Total: /45 ü They must be drawn according to YOUR dissection, and NOT an image or diagram found. ü They must be in good detail. It is not about the artistic skills but the accuracy of your drawing. ü The drawings must be properly shaded to see the various structures/organs. ü They must be properly and accurately labeled. 5/5 represents that the dissection drawing has been correctly and accurately drawn. The drawing is visible and easy to follow. 4/5 represents that the dissection drawing has been accurately drawn but with minor errors. The drawing is visible but parts are missing. 3/5 represents that the dissection drawing has some details but lacking others. The drawing is rough and not clear to see. 2/5 represents that the dissection drawing is missing a lot of info, or is incorrectly drawing. The drawing appears to have been rushed and does not show care in the work. 1/5 represents that the dissection drawing is incorrect, or drawn from another pre-made diagram. The drawing does not appear to have been carefully drawn.

Fetal Pig Dissection: External Anatomy

Name Fetal Pig Dissection: External Anatomy External Anatomy 1. Determine the sex of your pig by looking for the urogenital opening. On females, this opening is located near the anus. On males, the opening