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.
• 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.
• The main function of the respiratory system 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.
• 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
• Air enters into the Alveoli via the Alveoli duct.
• 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 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 on the image below to watch a molecule of oxygen as it passes through the structures of the respiratory system.
• Part of respiration involves breathing. Breathing is the moving of air into and out of the lungs.
• The breath rate is the number of breaths an individual takes in one minute.
• For example, if a person takes 20 breaths in one minute, then the person’s breath rate is expressed as 20 breaths per minute or 20 breaths/minute or 20 BPM, where BPM means Breaths per Minute.
• Note: The normal breath rate at rest for a typical human adult is 12 – 20 BPM.
• Question: If a person takes 60 breaths in 3 minutes, what is the breath rate?
• Solution: The breath rate is the number of breaths taken in one minute. Using the information provided, we can write: 60 breaths/3 minutes = 20 breaths/ 1 minute = 20 BPM. Therefore, the breath rate is 20 BPM.
• To measure your breath rate, breathe normally. Gently place your hand on your chest and count the number of inhalations or exhalations you take in one minute.
• You may use a watch or cellphone timer to count the 60 second interval.
• Breath rate is used to evaluate a person's medical condition.
• If the breath rate is too fast or too slow, the individual is not getting enough air into the lungs with each breath to adequately oxygenate the cells of the body.
• If the breath rate is irregular, it can indicate a problem with the nervous 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.
• 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.
• Blood always enters into 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.
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.
• Each time your heart beats it pumps blood into your arteries and to the rest of your body.
• The number of times your heart beats in one minute is called your heart rate, abbreviated HR. This is also called the pulse.
• Heart rate is expressed as Beats per Minute or BPM.
• For example, if your heart beats 72 times in one minute, then your heart rate is 72 BPM. If an individual’s heart beats 100 times in one minute, the HR (or pulse) is expressed as 100 beats per minute or 100beats/minute or 100 BPM.
• Note: The normal heart rate at rest for a typical human adult is 60 – 80 BPM.
• Question: What is the HR for a person whose heart beats 120 times in one minute?
• Solution: Recall, HR is expressed in BPM. Therefore, if the heartbeats 120 times in one minute, the heart rate (pulse) is 120 BPM.
• If you engage in physical activity or get excited, your pulse will increase.
• Certain medications will slow the heart rate. Others will cause it to increase.
• The pulse is an important indicator of your body’s condition.
• If the pulse is weak and/or irregular, it can be a sign of a serious health issue.
• If the pulse is too fast (tachycardia) or too slow (bradycardia), this, too, can be a sign of a serious health problem.
• One of the first things an Emergency MedicalTechnician (EMT) measures on a patient is the pulse. The pulse is always taken when you visit a doctor’s office or go for blood tests.
• Heart rate can be measured indirectly by taking the pulse.
• In adult humans, the pulse can be felt near the surface of the body at several locations, such as at the wrist or the neck.
• The pulse can be felt or palpated at the wrist by using two fingers (not the thumb) and gently pressing them against the thumb-side of the wrist on the palm side.
• The pulse can also be palpated on either side of the neck with two fingers on the carotid artery. Note: When the pulse is taken at the neck, be careful not to take it on both sides at the same time to avoid impeding blood flow to the brain.
• To take the pulse, first locate it with two fingers at the wrist or on the side of the neck. Using a timing device (second hand or cell phone timer), count the number of beats for 60 seconds (1 minute).
• Report the pulse in BPM (beats per minute).
• If an individual has a regular pulse, the heart rate can be calculated by counting the number of beats in 15 seconds and then multiplying the number of beats by four to obtain the heart rate in BPM.
• This works because there are four sets of 15 seconds in one minute (or 60 seconds divided by 4 is 15 seconds).
• For example, if a heart beats 5 times in 15 seconds, the heart rate is 20 BPM since4 x 5 = 20.
• Question: What would the heart rate be for an individual whose heart beats 6times in 15 seconds?
• Solution: If a persons’ heart beats 6 times in 15 seconds, that individuals’ heart would beat 6 x 4 = 24 times in one minute.
• His or her heart rate would be 24 BPM. Therefore, the heart rate or pulse would be 24 BPM.
Non-majors College Biology Lab Manual © 2021 by Marie McGovern Ph.D. is licensed under CC BY-NC 4.0