Lab 11
Anatomy & Physiology Part 2: Respiratory & Circulatory Systems

Learning Objectives
In this lab students will:
- Continue to learn about anatomy and physiology.
- Be able to list and label the organs and their functions of the respiratory system.
- Be able to list and label the major parts of the heart and the blood vessels associated with the heart.
- Be able to identify the thyroid gland, thymus gland, spleen, umbilical cord, and associated blood vessels.
- Apply anatomical knowledge to human physiology.

Respiratory & Circulatory Systems

• The Respiratory and Circulatory systems work together to transport oxygen and carbon dioxide to and from individual cells.
• The Respiratory system – provides an area for gas exchange to occur between body and external environment.
• The Circulatory system - provides a pathway for transport of gases and nutrients cells need and metabolic waste that cells must rid themselves of.

Respiratory System

Figure 11.1 Image of the major organs of the respiratory system. Highlighted are the Nasal cavity plus paranasal sinuses, the nose, tongue, the large larynx at the top of the trachea, the trachea surrounded by rings of cartilage. The right lung with its three lobes and the left lung with its two lobes. Branching off the trachea are the left and right bronchi which branch inside the lungs into smaller bronchioles. Enlarged is a set of three grape-like clusters called alveoli.

• Main function is exchange of gases (oxygen and carbon dioxide).
• It also functions to regulate pH of the body and is used for vocalization.
• In Mammals the respiratory system consists of a passage system (the conduction zone) and a gas-exchange system (the respiratory zone).
The Conduction Zone
• Oxygen-rich air enters through the nose or mouth and passes into the pharynx, larynx and then the trachea.
• In the chest (aka the thoracic cavity) the trachea splits into two large branches, one leading to each lung called the primary bronchi.

Figure 11.2 depicts the structures of the conducting zone and the respiratory zone. The conduction zone image includes the trachea, primary bronchus, and bronchioles. The respiratory zone image includes the alveolar ducts and the alveoli surrounded by a bed of capillaries.


• Inside the lungs, each primary bronchus is further divided into smaller and smaller secondary and tertiary bronchi and eventually into even smaller branches called bronchioles.
The Respiratory Zone
• Gas-exchange occurs within microscopic structures called alveoli which cluster at the end of each  bronchiole.
Alveoli are surrounded by a bed of capillaries, the smallest blood vessels.
• At this interface, between the alveoli and capillaries, oxygen and carbon dioxide are exchanged.
Figure 11.1 & 11.2 shows the components of the respiratory system and the conducting and respiratory zones.

Ventilation & Breathing

• Ventilation is the movement of air between the alveoli and the environment.
• When the diaphragm contracts, it allows air to enter the lungs.
• When the diaphragm relaxes, the air leaves the lungs.
• Oxygen moves by diffusion into the oxygen-poor blood.
Carbon dioxide diffuses from the blood into the air spaces of the lung and is expelled.
Breathing involves two steps: actively drawing air into the lungs (inhalation) and expelling air out of the lungs (exhalation).
• Both steps rely on rib muscles and the diaphragm (the main breathing muscle) to expand and collapse the chest cavity.
Inhalation involves the contraction of the dome-shaped diaphragm which expands the chest cavity, increasing the volume of the lungs.
• The increased volume creates a partial vacuum that sucks air into the lungs.
• This is called negative pressure inhalation.
Exhalation occurs when the diaphragm relaxes and resumes into dome-shape. This decreases the volume of the lungs and forces the air out.
• The lungs are never entirely without air; a small amount remains in the lungs to prevent collapse.
• The rib muscles can contact to allow more air to be inhaled or exhaled.
• In the fetal pig the lungs appear collapsed. Remember these pigs were never born and never relied on their lungs; instead they received all necessary oxygen from their mother via the placenta and umbilical arteries.
• Watch the Bell Jar demonstration to see how inhalation and exhalation occur.

Click here to watch Bell Jar Demo

Click on the image below to watch a molecule of oxygen as it passes through the structures of the respiratory system.

Image show the respiratory system. Animation shows a molecule of oxygen appearing from the right and entering the nose as the word nose enlarges and shrinks. The oxygen then enters the pharynx as the word pharynx enlarges and shrinks. The oxygen then enters into the larynx a as the word larynx enlarges and shrinks. The oxygen then enters the trachea as the word trachea enlarges and shrinks. The oxygen then enters the trachea as the word trachea enlarges and shrinks. The oxygen then enters the bronchus as the word bronchus enlarges and shrinks. The oxygen then enters the bronchioles as the word bronchioles enlarges and shrinks. The oxygen then enters the alveolar ducts as the word alveolar ducts enlarges and shrinks. Finally, the oxygen then enters the alveoli as the word alveoli enlarges and shrinks.

The Circulatory System

• Provides a pathway for transport of gases and nutrients that cells need as well as transporting metabolic waste that cells must rid themselves of.
• Its primary role is to transport substances to and from all parts of the body.
• The circulatory system moves nutrients, wastes, chemical messengers (hormones) and gases.
• Consists of: The heart, arteries, arterioles, capillaries, venules and veins.

The Heart

Figure 11.3 is an anterior view of a diagram of a human heart. Image states that “Note- left and right refer to the hearts left and right. Looking straight on this is reversed from your left and right. The apex of the heart serves as a good landmark for the left side of the heart. Areas of the heart and blood vessels carrying oxygen poor blood are shown in blue, those carrying oxygen rich blood are shown in red. The following blood vessels and parts of the heart are shown in blue; Superior vena cava, Inferior vena cava, right atria, right ventricle, pulmonary trunk. Pulmonary artery. Shown in red are the pulmonary veins, left atria, left ventricle, and the aorta. The following valves are also highlighted. The tricuspid valve (between the right atria and right ventricle) the pulmonary semilunar valve (between the right ventricle and pulmonary trunk) the mitral (bicuspid) valve (between the left atria and left ventricle) and the aortic semilunar valve (between the left ventricle and the aorta).

• In mammals the heart consists of four chambers; 2 atria (atrium) on the top of the heart and 2 ventricles on the bottom of the heart.
• The heart has four valves that prevent blood from flowing backwards; the bicuspid valve (lies between the left atria and left ventricle), the tricuspid valve (lies between the right atria and right ventricle), pulmonary semilunar valve (lies between the right ventricle and the pulmonary trunk) and the aortic semilunar valve (lies between the left ventricle and the aorta).
Figure 11.3 shows the four chambers, the four valves and the direction of  blood flow through the heart.
• The sinoatrial  (SA) node is a region in the right atrium that initiates an electrical impulse that passes to all the other cells of the heart.
• The SA node is responsible for initiating contraction of the heart muscles.
• This is the hearts natural pacemaker.
• The brain is not required to tell the heart to beat. However, the brain and hormones can tell the heart to beat faster or slower.

Flow of Blood

Figure 11.4 highlights the two side by side pumps within the heart. We are looking at a ventral view of the heart. On the left side of the image, which is the right side of the heart, we see the blue Superior vena cava connected to the blue right atrium which leads to the blue right ventricle. Between the right atria and right ventricle, we see the tricuspid valve. On this side we also see the blue inferior vena cava attached to the right atria. Located in the top and middle of the heart we see the blue pulmonary trunk which is attached to the right ventricle below and splits to form the two blue left and right pulmonary arteries above. Between the right ventricle and the pulmonary trunk is the pulmonary semilunar valve. The blue pulmonary arteries lead on either side to the left and right lungs. Within the lungs are capillary beds where oxygen enters the blood and carbon dioxide leaves the blood. From the lings we see red left and right pulmonary veins leading inti the red left atria which leads to the red left ventricle. Between the left atria and ventricle is the bicuspid valve. Located in the top and middle of the heart we see the large red aorta which is attached below to the left ventricle and above it splits and is shown carrying blood above and below to capillary beds of the body. Between the left ventricle and the aorta is the aortic semilunar valve. Within the capillary beds of the body oxygen leaves the blood and carbon dioxide enters the blood. The blood, now blue in color again is returned to the right atria via the superior or inferior vena cava.

• Blood always enter in to the heart through a vein (easy to remember, the word vein has IN right in it vein).
• That is what all veins have in common, they all carry blood, whether it is oxygenated or deoxygenated, into the heart.
• From veins blood flows into an upper atria (either the right or left atria.)  
Deoxygenated blood enters the right atria via the largest vein in the body, the vena cava. The superior vena cava carries blood returning from the head and neck. The inferior vena cava carries blood returning from the rest of the body.
Oxygenated blood enters the left atria via 4 small pulmonary veins.
• As the heart beats the blood moves from the upper atria into the larger lower ventricles (left or right ventricle).
• The blood is then pushed out of the ventricles into large arteries (either the aorta or the pulmonary trunk).
• All arteries carry blood away from the heart (arteries - away).
• That is one thing that all arteries have in common, they all carry blood, whether it is oxygenated or deoxygenated, away from the heart.
• The largest artery of the body, the aorta, carries oxygen rich blood out from the left ventricle to the body.
• The second largest artery, the pulmonary trunk, carries deoxygenated blood from the right ventricle to the lungs.
• Notice that there is no relationship between deoxygenated/oxygenated and being an artery or a vein!
• The heart is really  2 side by side pumps.
• The right side of the heart receives deoxygenated blood via the vena cava and pumps it to the lungs via the pulmonary trunk and then the left or right pulmonary arteries.
This blood is rich in carbon dioxide (a waste product of cellular respiration) and low in oxygen.
• In the capillary bed of the lungs the carbon dioxide is removed from the blood and oxygen is added. This is called the pulmonary (which means lung) circuit.
The now oxygenated blood returns to the left side of the heart via the pulmonary veins.
• The left side pumps the blood out via the aorta to the entire system (from head to toes).
• This is called the systemic circuit.
•  As blood travels through the systemic circuit it drops off oxygen to cells that need it (so they can carry out cellular respiration) and picks up the carbon dioxide (a waste product of cellular respiration).
• The deoxygenated, carbon dioxide rich, blood then again returns to the pulmonary circuit via the vena cava.
Figure 11.4 shows the two side by side circuits and the flow of blood through them.

Click on the image below to trace the path of a red blood cell through the Cardiovascular system.

Image shows a ventral view of a human heart. The animation starts with a single red blood cell appearing in the blue right atria as the words right atria enlarge and shrink. The red blood cell moves into the blue right ventricle as the words right ventricle enlarge and shrink. The red blood cell then enters the blue pulmonary trunk as the words pulmonary trunk enlarge and shrink. The red blood cell then enters the left pulmonary artery as the words left pulmonary artery enlarge and shrink. The red blood cell then enters a box that reads capillary bed of the lungs as the words capillary bed of the lungs enlarge and shrink. The red blood cell then enters the red pulmonary veins as the words pulmonary vein enlarge and shrink. The red blood cell then enters the red left ventricle as the words left ventricle enlarge and shrink. The red blood cell then enters the red aorta as the word aorta enlarges and shrinks. The red blood cell then enters the red Systemic arteries and arterioles as the words systemic arteries and arterioles enlarge and shrink. The red blood cell then enters a box that reads capillary bed of the body as the words capillary bed of the body enlarge and shrink. The red blood cell then enters the blue Systemic venules and veins as the words systemic venules and veins enlarge and shrink. The red blood cell then enters the blue inferior vena cava as the words inferior vena cava enlarge and shrink. Finally the red blood cell returns to the blue right atria where it started.

Major organs of the neck and Thoracic cavity in the Fetal Pig

Figure 11.5 shows some of the major organs found in the neck including the larynx which is a hollow muscular enlarged organ in the upper part of the throat, the thyroid which is usually a butterfly-shaped organ that surrounds part of the trachea. In this image the thyroid has been cut and is off to one side to reveal the trachea, which is a hollow pipe surrounded by rings of cartilage that carries air into the lungs. The thymus, which is a granular organ extending from above the heart into the neck is part of the immune system. In this image it has been partially teased away to reveal the heart in the thoracic cavity.  Also highlighted in the image are three major blood vessels in the thoracic cavity: the brachiocephalic artery, the aortic arch and the pulmonary trunk. Figure 11.6 shows the major organs of the thoracic cavity including the some of the major parts of the heart; the right auricle which looks like a dark red dog ear. The right auricle covers the right atria; the right ventricle and the left ventricle which are separated by red and blue blood vessels (coronary arteries and veins); the apex of the heart which is found in the lower left side of the heart. The heart side between two lungs which occupy much of the thoracic cavity. Also highlighted are the thyroid and trachea discussed in figure 11.5 and the liver and gallbladder which are in the abdominal cavity and were discussed in lab 10.

Figures 11.5 and 11.6 highlight the major organs found in the neck and thoracic cavity of the fetal pig.
Figure 11.5 shows some of the major organs found in the neck including the following;
• The larynx which is a hollow muscular enlarged organ in the upper part of the throat.
• The thyroid gland which is usually a butterfly-shaped organ that surrounds part of the trachea. This organ is part of the endocrine system. In this image the thyroid has been cut and is off to one side to reveal the trachea.
• The trachea which is a hollow pipe surrounded by rings of cartilage that carries air into the lungs.
• The thymus, which is a granular organ extending from above the heart into the neck is part of the immune system. In this image it has been partially teased away to reveal the heart in the thoracic cavity.  Also highlighted in the image are three major blood vessels in the thoracic cavity: the brachiocephalic artery, the aortic arch and the pulmonary trunk.
Figure 11.6 shows the major organs of the thoracic cavity including the some of the major parts of the heart;
• The right auricle which looks like a dark-red dog ear. The right auricle covers the right atria.
• The right ventricle and the left ventricle which are separated by red and blue blood vessels (coronary arteries and veins);.
• The apex of the heart which is found in the lower left side of the heart. The heart sits between two lungs which occupy much of the thoracic cavity.
• Also highlighted are the thyroid and trachea discussed in figure 11.5 and the liver and gallbladder which are in the abdominal cavity and were discussed in lab 10.

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Non-majors College Biology Lab Manual © 2021 by Marie McGovern Ph.D. is licensed under CC BY-NC 4.0