Lab 3: Trunk Wall Part II | Heart | Respiratory System
Learning Objectives:
- Identify the muscles of the thoracic cage involved in respiration and describe their functions.
- Identify the components of the respiratory system, including the trachea, bronchi, and lungs.
- Identify the great vessels transporting blood to and from the heart and outline the pattern of blood through the heart and lungs.
- Identify the internal and external anatomical features of the heart.
- Identify the valves of the heart and understand how valves regulate blood flow through the heart.
- Identify and describe the location and branches of the coronary blood vessels.
- Identify structures of the thoracic cavity using various imaging modalities, including X-Ray, CT, and Echo.
Terms to Know
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Muscles of Respiration
Trunk Wall
Respiratory System Structures
Great Vessels
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Heart Anatomy
Coronary Circulation
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Introduction
In this lab, you will examine the muscles of respiration, lungs, heart, and roots of the great vessels. The lungs function for the exchange of oxygen and carbon dioxide between the alveoli and the blood. Our muscles of respiration allow us to inhale and exhale by expanding and diminishing the space in our thoracic cavity and, in turn, our lungs. The heart pumps blood throughout our body, carrying oxygen and nutrients to our tissues, carrying waste products away from our tissues, and much more.
You will have the opportunity to examine preserved human heart and lung tissue in this lab. We have this great opportunity thanks to the Pathology Department at UW hospital. Treat these specimens with care and respect. As with all of the human specimens that we will view in this lab, we have the opportunity to examine them because the donors and their families were generous enough to allow us to learn from them. Appreciate how great this opportunity is, and give them the respect that they deserve.
Lab Activity 1: Muscles of Respiration – digital atlas
Utilize the digital atlas to explore the muscles of respiration.
- Open the Atlas app and go to Muscular System Views.
- Under the muscular system views, click on 9. Inhalation and 10. Exhalation.
- Identify the following muscles of respiration (work from superficial to deep). Highlight each muscle. The box on the upper right side of the screen shows the action of each muscle, and those actions are listed below as well. You are only responsible for the actions of these muscles (not the origin or insertion, for example). Be sure to look at the muscle from various angles and zoom levels to appreciate the architecture and orientation of the muscle fibers. This is important when considering the action of the muscle.
- External intercostals: Elevate ribs with passive inhalation
- Internal intercostals: Depress the ribs with forced exhalation
- Serratus posterior superior: Elevate the ribs with forced inhalation
- Serratus posterior inferior: Depress the ribs with forced exhalation
- Diaphragm: Expands and increases the vertical dimension of the thoracic cavity, Increases pressure in the abdominopelvic cavity
- Go back to the menu of the Atlas App and now go into the Muscle Actions tab.
- Under the muscle actions, click on Ribs elevation and Ribs depression.
- While in these views, the virtual cadaver will be moving. You can still touch each of the muscles listed above to see their role in either rib elevation or depression (inhalation or exhalation).
Lab Activity 2: Trunk Wall and Muscles of Respiration – Cadaver
In Lab 2 you viewed the posterior musculature of the trunk on the cadaver. In this lab you will view the anterior musculature of the trunk and thoracic cage.
Observe the external oblique on the lateral aspect of the abdominal region. Fibers of this muscle run anteriorly and inferiorly. Unilateral contraction of the external oblique rotates the trunk to the opposite side and assists with lateral flexion to the same side. Gently reflect the external oblique to observe the internal oblique. Fibers of this muscle run posteriorly and inferiorly. As a result, unilateral contraction rotates the trunk to the same side and assists with lateral flexion to the same side. Bilateral contraction of both the internal and external oblique contributes to trunk flexion.
Medial to the obliques, observe the rectus abdominis muscle. This muscle appears as two flat muscles running vertically parallel to each other, separated by connective tissue called the linea alba. The linea alba has been cut here to reveal the abdominal organs. Additional horizontal lines of connective tissue separate portions of the muscle, giving the “six pack” appearance. The rectus abdominis flexes the trunk.
Deep to the obliques and rectus abdominis, observe the transversus abdominis. Fibers of transversus abdominis run relatively horizontally around the trunk. Contraction of this muscle bilaterally compresses the abdominal cavity, and unilateral contraction causes trunk rotation to the same side. On the left side of the cadaver the internal oblique has been separated from the transversus abdominus. On the right the fascia connecting the two muscles remains intact, and you can observe the superior portion of the transversus abdominus emerging deep to the internal oblique.
Observe the thoracic cage. The ribs have been cut to the left of the sternum in order to view the contents of the thoracic cage. However, you can move them back into anatomical position. View the sternum in the center of the thoracic cavity. Palpate the manubrium, body, and xiphoid process. Also palpate the sternal angle and suprasternal notch.
Between the ribs, observe the external and internal intercostals. You will need to open the thoracic cage to observe the internal intercostals on the internal aspect.
Lab Activity 3: Heart and respiratory tissue – Cadaver and additional donor tissue
Full Cadaver
Observe the heart in situ in the cadaver. Observe its orientation. The right ventricle is inferior, resting on the diaphragm. The great vessels (aorta and pulmonary trunk) are visible superiorly. The right atrium is to the right, and the left ventricle is to the left. This heart is moderately enlarged compared to a typical heart.
The coronary arteries supply the heart with blood, and some are visible on the cadaver’s heart. Notice the anterior interventricular artery, which is a branch off of the the left coronary artery. The right coronary artery can be seen branching off of the ascending aorta and traveling in the coronary sulcus. A small portion of the right marginal artery can be seen traveling along the right margin, or border, of the heart. The right coronary artery travels to the posterior aspect of the heart and gives of the posterior interventricular artery, which can be seen by gently lifting the heart to view its posterior aspect.
Observe the lungs in the cadaver. They are much smaller than usual, and the reason for this is unclear. Notice that the diaphragm is quite domed in shape and extends unusually superiorly into the thoracic cavity. The abdominal organs (which will be viewed in the next lab) also extend unusually far into the thoracic cavity (e.g. liver, hepatic flexure, spleen, etc.). The donor’s cause of death was non-small cell lung cancer, but evidence if the disease is not evident by viewing the external aspect of the lungs. It is also unlikely to be the primary cause of the small lung size. The patient was a smoker, but that is also unlikely to cause the lungs to be this small and the abdominal organs and diaphragm to move this high into the thoracic cavity.
It is possible that the donor was born with smaller lungs, and the enlargement of the heart may have been compensatory to ensure the body received the oxygenated blood it needed. It is also possible that smoking or cancerous changes made the already small lungs even smaller. This likely would have been observed with imaging as part of the cancer diagnosis, but we do not have access to additional medical records for our donor.
Additional Donor Heart and Lungs
We also have heart and lung tissue (as well as abdominal and pelvic organs) from a second donor. The two coronary arteries and four primary branches arteries can be seen on this heart. Be extremely gentle when handling and turning this tissue.
- Right coronary artery – Brach off of the aorta traveling to the right in the coronary sulcus
- Right marginal artery – branching from the right coronary artery and traveling along the right margin of the heart
- Supplies the right border (margin) of the right ventricle
- Posterior interventricular artery – on the posterior aspect of the heart traveling between the right and left ventricles. This vessel is often called the posterior descending artery (PDA) in the clinical setting.
- Supplies the posterior aspect of the right and left ventricles
- Right marginal artery – branching from the right coronary artery and traveling along the right margin of the heart
- Left coronary artery – Brach off of the aorta traveling to the left in the coronary sulcus
- Anterior interventricular artery – on the anterior aspect of the heart traveling between the right and left ventricles. This artery is often called the left anterior descending artery (LAD) in the clinical setting.
- Supplies the anterior aspect of the right and left ventricles as well as the interventricular septum
- Circumflex artery – travels around the left aspect of the heart in the coronary sulcus between the left atrium and left ventricle
- Supplies portions of the left atrium and ventricle
- Anterior interventricular artery – on the anterior aspect of the heart traveling between the right and left ventricles. This artery is often called the left anterior descending artery (LAD) in the clinical setting.
- Note*** You can observe the left marginal artery along the left margin of this heart. You will not be asked to identify this artery.
The middle cardiac vein can also be seen next to the posterior interventricular artery. It drains blood from the same area supplied by the posterior interventricular artery. The great cardiac vein, which travels with the anterior interventricular artery, and small cardiac vein, which runs with the marginal artery, cannot be observed here, but you can view these veins on the laminated images or with the visible body atlas. The great cardiac vein drains blood from the area supplied by the anterior interventricular artery, and the small cardiac vein drains blood from the same area supplied by the right marginal artery. These veins drain into the coronary sinus on the posterior aspect of the heart in the coronary sulcus.
Observe the great vessels. The ascending aorta leaves the left ventricle, and then the aortic arch arches to the left. The descending aorta descends through the thoracic cavity and continues into the abdominal cavity, carrying blood to the body tissues. The pulmonary trunk leaves the right ventricle and branches into the right and left pulmonary arteries. You can follow the pulmonary arteries to the hilum of the lung.
Observe the size of the lungs from this donor compared to the full cadaver donor. They are substantially larger and more typical in size. The right lung has three lobes: Inferior, superior, and middle. The oblique and horizontal fissures separate the lobes. The left lung only has two lobes due to the space taken up on the left side of the thoracic cavity. The two lobes of the left lung are separated by an oblique fissure.
Darkened spots may be observed occasionally throughout the lung. This can be evidence of smoke inhalation in some cases, and it can also occur with frequent inhalation of polluted air.
Also observe the trachea and the bronchi branching from the trachea and traveling to the hilum of the lungs.
Lab Activity 4: Heart Tissue from Pathology at UW Hospital
The organs from pathology at UW hospital were cut at autopsy to allow the pathologists to search for disease in the tissues. Smaller cuts sequentially along the outside surface of the heart were made to investigate the condition of the coronary arteries. The coronary arteries are usually surrounded by adipose tissue.
The following provides some background on the hearts we have in our lab. Case A and Case C were both males with enlarged hearts (cardiomegaly). The heart in Case C is particularly enlarged. For reference, the typical male human heart weighs between 240-380g. (***Note: All cases tested negative for COVID-19)
- Case A: This heart is from a male patient in his mid-50s. It is enlarged, with a weight of 500 g. The chambers are somewhat dilated, meaning the atria and ventricles have more space than they typically should. The valves were dilated, meaning the opening that blood travels through to enter or exit a ventricle was enlarged, increasing the risk for regurgitation of blood backward through the valve. The coronary arteries have mild atherosclerosis with calcification, with up to 50% stenosis (narrowing) of the anterior interventricular (left anterior descending, LAD) artery. You may be able to feel the calcification along these arteries in some locations.
- Case B: This heart is from a female patient in her early 60s. It is mildly enlarged at 400 g. The patient had a clinical history of hypertension. The left ventricle walls were borderline hypertrophic (thickened) to accommodate the increased force needed to push blood out of the heart and through the vessels of the body. There is evidence of a subendocardial (below the endocardium, or inner layer of the heart) hemorrhage resulting from refractory hemorrhagic shock in the left ventricle. All four valves of the heart are dilated, and the left atrioventricular (mitral, bicuspid) valve is fibrotic (thickening and loss of flexibility that can lead to valvular dysfunction). This heart also has a patent foramen ovale. The foramen ovale never closed at birth, so instead of a fossa ovalis being present on the interatrial wall, the foramen ovale passageway remains between the atria. See below for more information on the foramen ovale and fossa ovalis.
- Case C: This heart is that of a man in his early 60s. The patient suffered a sudden cardiac arrest following cirrhotic cardiomyopathy, a cardiac condition observed in patients with cirrhosis of the liver. Cardiomegaly was severe, with the heart weighing 740 g. The ventricles are hypertrophied (thickened walls), and all four chambers are dilated. These open spaces would not be this large in a healthy heart. The aortic valve is calcified, and atherosclerosis is present in the anterior interventricular artery (left anterior descending, LAD).
As you examine the hearts, you should identify several of these structures on most or all of the specimens. Not all structures will be clearly visible on every specimen, and that is OK.
- Observe the external features of the heart. In the region of the atria, notice a pouch-like structure. This is called the auricle, and there is one present on each atrium. It is visible on both the wet tissue and the plastinated hearts.
- Look inside the right atria and view the septum between the left and right atria. Observe a small oval indent on the septum. This is the fossa ovalis. Before birth, there is no need for blood to go to the lungs because the fetus receives oxygen from the mother’s circulation. The fossa ovalis is an opening in the fetus, then called the foramen ovalis. As a result, blood can bypass pulmonary circulation and go straight from the right atrium to the left and into systemic circulation. It closes shortly after birth, but the small oval indent, the fossa ovalis, remains. Notice that the foramen ovale never closed in case B. This is called a patent foramen ovale.
- Observe the ventricles. Notice that the left ventricle is thicker than the right. The left ventricle pumps blood out to the whole body, while the right ventricle pumps blood to the lungs.
- Observe the structures of the internal features of the heart from the list of terms.
- The right (tricuspid) and left (bicuspid, mitral) atrioventricular (AV) valves prevent backflow from the ventricles into the atria. The pulmonary and aortic semilunar valves prevent backflow from the pulmonary arteries and aorta into the right and left ventricles. You should note whether or not it appears that the valve is near an artery or separating the atria and ventricles. You can also differentiate an AV valve from a semilunar valve by determining if the chordae tendineae are attached to it. The chordae tendineae prevent the AV valves from prolapsing (collapsing backward) into the atria.
- The projections from the heart wall that attach to the chordae tendineae are the papillary muscles. They provide support to prevent prolapse of the AV valves.
- The muscular ridges on the walls of the ventricles are called the trabeculae carneae. Their function is not well-understood.
- Also, observe the interventricular septum separating the right and left ventricles.
- Observe the great vessels entering and leaving the heart. The aorta leaves the left ventricle, while the pulmonary trunk leaves the right ventricle. The aorta has thicker walls than the pulmonary trunk. It may be difficult to distinguish the aorta from the other vessels in the laminated images taken from a superior view. The superior and inferior vena cava carry deoxygenated blood to the right atrium, while the pulmonary veins carry oxygenated blood to the left atrium. They will appear as holes in the right atrium.
- Some of the coronary vessels can be seen on the wet heart tissue, but note that not all of these vessels are readily identifiable. On this tissue, they have been sectioned as part of the pathological examination. Refer to the laminated images or digital atlas for a clear view of these vessels.
- Note that the left and right coronary arteries branch off the ascending aorta just after it leaves the heart. The other vessels do not have any immediate branches. This is one way to identify the aorta in the wet specimens, as this structure has been cut open. You can usually see dark “holes” near the base of the aorta on its internal aspect. These holes are the origins of the coronary arteries. This vessel also arches upwards and to the left.
Be sure to view all of the hearts. Everyone has slightly different anatomy, so it is always good to observe multiple examples. Any of them could be used on an exam.
Lab Activity 5: Plastinated Heart Tissue
The plastinated tissue is human tissue that has been preserved in a way that hardens it. While studying this tissue, you can touch it without gloves. However, please try to limit how much you are handling it. This is because the oils and dirt on your hands can degrade the plastinated tissue over time. One of the plastinates has been cut through the right ventricle and atrium. The other has been cut through the left ventricle and right atrium. *Note: The vessel coloring is indicating arteries in red and veins in blue. The colors do not necessarily indicate oxygenated or deoxygenated blood.
When examining the plastinates, use the laminated images and/or digital atlas to help you identify structures in the list of terms and described in the previous activities.
Lab Activity 6: Respiratory system tissue from Pathology at UW Hospital
The lung tissue from pathology at UW hospital has been cut to search for pathological changes. The way that the lungs are cut makes it difficult to see the fissures and lobes. The lungs in Case A have evidence of acute bronchopneumonia. In Case C, the lungs are congested and heavy and have evidence of alveolar inflammation or fibrosis.
Observe the hilum on the medial aspect of the lungs. By the end of the unit, you will observe several organs that have a hilum. This is where neurovascular structures, and sometimes other structures, enter or leave an organ. In the lungs, you can observe bronchi, arteries, and veins in this location. The bronchi will feel hard as a result of the cartilage in their walls. Arteries have thicker walls than veins, and this will be evident in the hilum as well.
The orientation of these structures as they enter/leave the hilum is consistent and can tell you if you are looking at a right or left lung. You can use the mnemonic “RALS.”
- In the Right lung, the pulmonary artery will be Anterior to the main bronchi.
- In the Left lung, the pulmonary artery is located Superior to the main bronchi.
Observe a cut internal section of a lung and examine the appearance of the alveoli. The lungs will look somewhat like a very condensed sponge, which is a result of the alveoli.
Observe the trachea and primary (main) bronchi. Feel these specimens and notice the hard cartilage. Cartilaginous rings help maintain this tube’s lumen (open portion) so that our airway does not collapse. Also, notice the point where the trachea splits into the primary bronchi. The point at which the split is called the carina. The image at the right is taken from within the trachea, looking down at the bronchi.
In Case A, the trachea is preserved with its relation to the esophagus and aortic arch. Notice how the trachealis muscle is on the posterior aspect of the trachea, just anterior to the esophagus.
Lab activity 7: Plastinated Respiratory Tissue
Observe the lobes and fissures of the lungs. Notice the orientation of the pulmonary arteries and bronchi as they enter the lungs at the hilum. You should see that the pulmonary artery is anterior to the bronchus on the right, while it is superior to the bronchus on the left.
Observe the diaphragm. This thin muscle is the primary muscle of respiration. Notice how it is dome-shaped, extending upward into the thoracic cavity, though not as far as in the full cadaver. It is innervated by the phrenic nerve, which cannot be seen on our tissue but can be seen in laminated images or in the visible body atlas. The phrenic nerve descends through the thoracic cavity and innervates the diaphragm. It originates from the C3, C4, and C5 spinal roots. Remember, C3, C4. C5 keeps the diaphragm alive. A portion of the diaphragm is also present with the trachea in Case A.
Lab Activity 8: heart and lungs – Anatomage Navigator tool
The Navigator program will be open and ready for you to use. Ask your TA if you need any help or if it is not open. Zoom in on the heart and lungs, and center them on the screen.
- Using this tool, explore the cross-sectional and internal anatomy of the heart and lungs. Hover the cursor over one of the cross-section images at the top of the screen and scroll. Compare what you see on the 3D digital model and cross-sectional images to better understand the relationship between the 3D anatomy that we typically see and how the structure appears in cross-section. For example, you will be able to see the chambers of the heart labeled as you move superiorly and inferiorly along the model. You will also see the different structures visible in the same section at different levels. The cross-sections are essentially a color version of the black and white images that you will see in radiology images. Spend some time exploring the structures in the digital model and cross-section. Be sure to view the cross sections in all three planes.
- Observe the heart, lungs, and trachea on the 3D model. Only a few structures will be visible on the 3D model, but between the digital model and the 3D model, you should identify most of the structures in the list of terms.
- You will be asked to identify structures in the cross-sectional images on the exams. A helpful method for orienting yourself to the cross-section is to identify structures that you know are surrounding a given structure. Understanding what other tissues look like around the target tissue can help you understand whether you are superior or inferior, medial or lateral, etc.
Lab Activity 9: Thoracic Radiology
View the radiology presentation in Canvas on a lab computer. You will see X-Ray imaging, Echo imaging, and CT imaging of the thoracic cavity. Identify the following structures:
X-Ray
- Lungs
- Heart
- Liver
- Ribs
- Vertebrae
Echocardiogram (echo) – Heart
- Atria
- Ventricles
- Right atrioventricular (tricuspid) valve
- Left atrioventricular (bicuspid/mitral) valve
- Pulmonary semilunar valve
- Aortic semilunar valve
- Interventricular septum
- Papillary muscles
CT
- Lungs
- Heart
- Aorta
- Liver
- Vertebrae
