Generalized Dissection Guide - Science A 2 Z



Generalized Dissection Guide

Major Organ Systems:

• Integument (the outside covering)

• Circulatory System

o Heart, arteries, veins, capillaries, and blood

• Lymphatic System – pumps plasma back to heart when it leaks out of capillaries and is home to the majority of white blood cells

o Lymph, lymph nodes and vessels, white blood cells, T- and B- cells – largest organ is the spleen

• Respiratory System

o Nose, trachea and lungs

• Digestive

o Mouth, esophagus, stomach, small and large intestines

• Excretory System

o Kidneys, ureters, bladder and urethra

• Reproductive

o Female: ovaries, oviducts, uterus, vagina and mammary glands

o Male: testes, seminal vesicles and penis

• Nervous System

o Brain, spinal cord and peripheral nerves

▪ Sensory Systems

• Skeleton – support and protection

o Bones, cartilage, tendons and ligaments

o Produce white and red blood cells in the marrow

• Muscles – movement both voluntary (swinging a bat) and involuntary (digesting your food)

o Skeletal and smooth muscles

• Endocrine – hormones to keep you functioning! Hormones control how fast you grow, maintain your body temperature, fight or run away when scared, and much, much more!

o Some of the glands of the endocrine system are hypothalamus, pituitary, thyroid, pancreas and adrenal

For our dissections, you will first examine:

• The Epidermis – outside of the organism. What is the epidermis like? Is it scaly, smooth, slimy, hairy, or feathery?

• The Sensory – eyes, ears, touch, taste, smell, electro-sensors, lateral line, etc.

• How many appendages (arms and legs), is there a tail, does it have fins? How about gill flaps or slits?

After recording this information, you will begin to examine the internal anatomy of our organism.

• Wait until you receive directions on how best to expose the internal anatomy of the weekly organism. When you make your first cuts, you want to penetrate the skin and muscles, but not puncture the internal organs. If you do, however, it is okay. After all, you are learning how to do this!

• Generally, after exposing the internal anatomy, the first organ you see is the liver. It plays a major role in metabolism and has a number of functions in the body, including glycogen storage, decomposition of red blood cells, plasma protein synthesis, and detoxification. The liver is also the largest gland in the human body. It lies below the diaphragm in the thoracic region of the abdomen. It produces bile, an alkaline compound that aids digestion, via the emulsification of lipids. It also performs and regulates a wide variety of high-volume biochemical reactions requiring very specialized tissues. The liver breaks down toxic substances and most medicinal products in a process called drug metabolism. The liver belongs to several different organ systems, digestive, excretory, and circulatory to name just three. Remove the liver.

• Under the liver, you will be able to see part of the esophagus, stomach, small and large intestines. A simple snip at the esophagus (as high as possible) and a simple snip at the anus should allow you to remove these organs. You will have to cut or tear the think membrane that holds all of these parts in place inside this animal. Remove the digestive tract. How long are the short intestines? Measure the length of the short intestines. Record the length on your trait chart.

• Under the digestive tract, you will see the kidneys and reproductive system. Is your organism a male or female?

• To see the heart and gills/swim bladder/lungs, you will need to cut between the ribs. Depending on the organism, it may take a bit of strength to do this. Remove the heart. Cut the heart into 2 halves and count the number of chambers. Record this on your trait chart.

• The swim bladder is found only in bony fish. Our lungs are from the same cells as the swim bladder. You will find the cavity for the swim bladder in the perch just underneath the spine. It may be hard to see.

• Gills or Lungs? If your animal has gills, you can view them by cutting into them from the outside. Locate the gill flap or gill slits, and cut deeply into the animal. They are supported by cartilage, so they will be hard to cut. If you are working on a terrestrial animal, the lungs will be located to the left and right of the heart. Remove the lungs, and squeeze to verify that they are spongy, then cut in half.

• Sensory System: If there is time, you may remove the eye, and dissect to locate the different parts of the eye – the lens and retina. Depending on the animal, Barb will describe how best to view the other sensory organs.

• Brain: The brain is encased in cartilage or bone, and is very difficult to dissect. Depending on the organism and our remaining time, you may only get to look at one brain exposed by Barb.

To clean up your equipment:

• Do not remove your goggles or gloves until everyone has finished cleaning up.

• Scrape all biological material into the Biohazard bag. Do not dispose of any tools, the pad or the dissection tray in this bag.

• Wash all tools (tray, pad, scissors, probes, tweezers, and hand lenses) with soap and water. Rinse thoroughly. Completely dry all equipment (tray, pad, scissors, probes, tweezers, and hand lenses).

• Barb will have a place for you to put each of your tools. Be sure to stack them neatly.

• Using the sponge and Lysol, clean your dissection table/desk. Make an “S” with the Lysol, and wipe completely.

• When everyone has finished cleaning their equipment and tables/desks, you may remove your gloves (please follow Barb’s directions on how to properly remove gloves) and they may be tossed into the regular garbage (remember, you washed all your equipment with soap and water, so your gloves are clean).

• Remove your goggles and return them to the goggle stack.

Complete your traits for this organism.

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