Circulatory System Dissection of the Heart


Objectives: Upon completion of this lab you need to:

  1. Be able to identify, and know the names and functions of the major structures of the heart external anatomy (see bold terms).
  2. Be able to identify, know, and understand the names and functions of the major structures of the heart internal gross anatomy (see bold terms).

 

 

Background:

Because mammals are worm blooded (endothermic) and generally very active animals, they have high metabolic rates. One major requirement of a rapid metabolism is the need for oxygen and nutrients to reach body cells in sufficient quantities to satisfy their needs. Metabolic wastes need to be carried away quickly for disposal so that they do not interfere with cell operations. These functions are carried out by the animal`s circulatory system that is driven by the heart.

REVIEW THE BASIC ANATOMICAL TERMS LISTED BELOW BEFORE YOU BEGIN THE DISSECTION

  • Anterior - near or toward the head
  • Posterior - near or toward the tail
  • Dorsal - referring to the back
  • Ventral - referring to the belly
  • Lateral - referring to the side
  • Median - referring to the midline
  • Cranial - referring to the head
  • Caudal - referring to the tail
  • Proximal - toward the attached end of a structure
  • Distal - toward the free end of a structure
  • Longitudinal - in the axis from head to tail
  • Transverse - across the longitudinal axis
  • Pectoral - chest or shoulder area
  • Pelvic - hip region
  • Inferior- toward or closer to the tail (caudal region)
  • Superior- toward or closer to the head region

 

 

Procedure: Read and Understand the Following Paragraphs and Steps Explicitly

 

External Anatomy

See the diagrams and/or picture file(s) to help locate the following

For the dissection of the heart you will need a scalpel, scissors, blunt probe and diagrams. The definition of dissecting is to separate the body into parts for the purpose of study. This means that your sharp instruments should be used sparingly and with care. The most useful dissecting instrument is a blunt probe, which can be used to separate membranes easily.

  1. Preserved hearts come in two ways: with the pericardium, and without the pericardium. The pericardium is a membranous sac that envelopes the heart. It protects the heart and separates it from the rest of the thoracic cavity. The pericardium is a tough sac that is attached to the heart where large vessels emerge.
  2. Remove the pericardium by cutting it away from the heart. The whitish lumpy tissue on the outer surface of the heart is fat tissue The bulk of heart is the reddish brown heart muscle or myocardium. The chambers of the heart are lined with tissue called endocardium. The endocardium is continuous with the endothelium which lines the blood vessels of the body.

 

 

Ventral View

  1. Place your heart in position as shown in Figure 1. This the ventral side of the heart.
  2. The line running diagonally down the right side (facing you) of the heart is the bottom left side is the coronary artery.
  3. The pointed bottom of the heart is called the apex. Locate and familiarize yourself with as many of the following features pointed out in Figure 1:

Superior (Cranial) Vena Cava = Deoxygenated blood is returned to the heart from the head and shoulder regions through this large vein.

Inferior (Caudal) Vena Cava = Deoxygenated blood is returned to the heart from the regions of body below the shoulders via this large vein.

Right Auricle (Atrium) = Blood is pushed from the superior and inferior vena cava veins into the this walled chamber and is the pumped into the right ventricle.

Right Ventricle = Blood pumped from the auricle enters this thick walled chamber and is pumped under higher pressure to the lungs via the aorta pulmonary artery.

Right and Left Pulmonary Veins = Oxygenated blood is returned to the heart from the lungs by these vessels.

Left Auricle (Atrium) = Oxygenated blood from the pulmonary veins is pumped from this thin walled chamber into the left ventricle.

Left Ventricle = Blood is pumped from this chamber out through a large vessel, the aorta, to the body.

Brachiocephalic Artery = The first major branch off of the aorta and the major artery to the forelimbs and head.

Coronary Artery = This artery supplies blood to the myocardium directly.

 

Dorsal View

  1. Compare your heart with Figure 2 and try to identify some of the features that were previously mentioned. Often it is helpful to place dowels, blunt probe, or needles into the vessel apertures as you identify them.. This helps in keeping track of the vessels already identified.

 

 

Internal Anatomy

See the diagrams and/or picture file(s) to help locate the following

  1. Read and review Step 8 very carefully before doing the actual procedure.
  2. With a sharp scalpel, slice the heart almost in half as shown in Figure 3. The cut must go through the middle of the left auricle through the aorta and the right auricle. Cut straight down completely through the left and middle of the heart and almost completely through the right side. Leave a small flap of tissue between the left and right ventricle connecting the two halves together.
  3. Locate and familiarize yourself with as many of the following features pointed out in Figure 3:

Right Auricle (Atrium) = Blood is pushed from the superior and inferior vena cava veins into the this walled chamber and is the pumped into the right ventricle.

Right Ventricle = Blood pumped from the auricle enters this thick walled chamber and is pumped under higher pressure to the lungs via the aorta pulmonary artery.

Left Auricle (Atrium) = Oxygenated blood from the pulmonary veins is pumped from this thin walled chamber into the left ventricle.

Left Ventricle = Blood is pumped from this chamber out through a large vessel, the aorta, to the body.

Interventricular Septum = This is a thick wall of myocardium that divides the two ventricles.

Chordae Tendineae = The heart strings or ligaments that support the atrioventricular valves.

Tricuspid Valve = This valve is made up of three (3) flaps of rounded tissue suspended by chordae tendineae that extend into the ventricle. This valve allows the flow of blood from the right auricle into the right ventricle. It prevents blood from flowing back into the right auricle when the right ventricle contracts.

Pulmonary Semilunar Valve = This valve prevents blood from the pulmonary artery back flowing into the right ventricle after the ventricle contracts.

Mitral Bicuspid Valve = This valve prevents blood from back flowing from the left ventricle back into the left auricle during its contraction.

Aortic Semilunar Valve = Prevents back flow from the aorta into the left ventricle after contraction.

Papillary Muscle = Areas of the ventricle where the chordae tendineae come from and are attached to the myocardium.