Regents Prep: Living Environment: Laboratory:
Dissection

Anatomical Direction

Before beginning a dissection, it is important to have an understanding of some of the basic directional terminology associated with the dissection of specimens.   Some of these terms include proximal, which means toward the body, and distal, which means to move away from the body.  Other important anatomical directions are indicated below.

Key Anatomical Directions

Dissection Safety
Proper safety procedures when working with dissection tools and specimens is of greatest importance.     Some safety rules to engage in when dissecting specimens are as follows.

Dissection Safety Rules

  • Follow all instructions given by your teacher.
  • Inform your teacher of any illness as a result of exposure to chemicals used in specimen preparation.
  • Avoid contact with preservative chemicals. Rinse the specimens completely before dissection.
  • Know where the eye-wash fountain is if needed.
  • Wear safety goggles to prevent the splashing of any chemicals into the eyes.
  • Properly mount dissection specimens to dissecting pan. Do not dissect a specimen while holding it.
  • Handle scalpel or razor blade (safety edged) with extreme care.
  • Always cut away from your body and away from others.
  • Never ingest specimen parts.
  • Never remove specimens or specimen parts from the classroom -- until the dissection is completed all parts of the dissection must remain within the dissecting pan.
  • Properly dispose of dissected materials.
  • Store specimens in as directed by your teacher.
  • Clean up the work area and return all equipment to the proper place when the dissection is completed.
  • Wash hands after each dissection.

Dissection Equipment

Dissection Equipment

The pictured dissection equipment from left to right is (1.) a teasing or dissection needle which used to pull apart muscle tissue, (2) dissecting scissors which are used to cut through tissue, and (3) a scalpel, which is a knife used to slice through and cut tissue.

Plant Dissection
Many kinds of flowering plants, such as lilies, daffodils, or tulips are commonly subjects for dissection in biology.    The flower is the plant structure specialized for reproduction in advanced plants.   The processes of meiosis and fertilization occur in the flower.   

Some Key Flower structures

petals: colored parts inside the sepals which attract insects

sepals:
structures which are usually green outside the petals which help to protect the flower

stamen
:  forms the male reproductive organ and consists of an anther and a filament

anther
: pollen box in which pollen grains are formed containing the genetic material which produces sperm

filament
: supports the anther

pistil or carpel
: female reproductive organ which consists of three parts

stigma
: found at the top of the pistil, is often sticky and hairy adapting it to catch and hold pollen

style
: tube-like connection between the stigma and the ovary

ovary: enlarged part of the pistil attached to the receptacle (stem tip on which the flower rests) and contains the ovules

ovules: small white structures within the walls of the ovary which produces the plant egg cells

Animal Dissection
The dissection of animals is important for many reasons.   It helps in the learning about the internal structures of animals.   It also allows students to learn how organs and tissues are interrelated.    Another purpose of dissection is to allow the comparison of organisms in terms of their organs and relative complexities.
   While many good simulations of dissections may be observed, it seldom can replace the benefits of the actual participation in an actual dissection.

Some common vertebrate organisms dissected in the living environment lab include the frog and the fetal pig.     Usually the dissection procedure involves tying the organism down firmly on the dissection pan, cutting the organism open on its ventral side (as pictured below), and pinning its tissues and muscles back to observe its internal organs.    Different teachers may have their own preferences in terms of their emphasis on the tissues and organs to be observed in a dissection.  

Key Internal Organs of the Frog

Organ Body System

Major Function

brain nervous  thinking and coordination of body activities
heart circulatory pumps blood through the body
stomach digestive stores and begins the chemical digestion of food
small intestine digestive finishes chemical digestion and absorbs digested nutrients into the blood
liver digestive (and other systems) makes bile, detoxifies poisons, many other functions
gall bladder digestive stores bile from liver for release into small intestine to aid in fat digestion
lungs respiratory exchanges gases with the external environment (aided by the skin in the frog)
kidneys excretory filter wastes from the blood
ureter excretory carries wastes to the urinary bladder
urinary bladder excretory stores urine before its release from the body
pancreas endocrine/digestive produces hormones like insulin which regulate blood sugar, produces pancreatic juice which aids in digestion in the small intestine
ovaries reproductive makes eggs in female frog
testes reproductive makes eggs in male frog

 

Frog Internal Anatomy

Web Resources
Interactive Frog Dissection (Dr. Mable B. Kinzie, University of Virginia)
Virtual Pig Dissection
(Earl W. Fleck, Ph.D. Whitman College)

 

Created by James M. Buckley, Jr.
Copyright 1999-2003 Oswego City School District Regents Exam Prep Center
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