BIOL10008/9 S1 2022 Prac 4 F2F
PRACTICAL 4: HEART AND LUNGS
Regulation
Cells
Prior to attending your practical, you should have completed the Practical 4 preparation on Canvas.
In this practical, we will examine the structure and function of the heart and lungs.
Time
0:00 – 0:10
Activity
Welcome and introduction to Practical 4
0:10 – 1:10
Activity 1: Lungs – Gas Exchange Surfaces
Practical task 1.1: Sheep’s pluck
Practical task 1.2: Density of Tissues
Practical task 1.3: Cellular Structure of Lung Tissue
Practical task 1.4: Abnormal Lung Tissue
Activity 2: The heart
Practical task 2.1: Heart dissection
Practical task 2.2: Heart rate data – heart function
Online Practical 4 Assessment
Timed MCQ quiz: 15 minutes, 10 marks, 5% of subject grade
1:10 – 2:45
Afterwards
(50 mins + debrief)
(50 mins + debrief)
(25 mins + debrief)
ASSESSMENT
Each online assessment based on material covered during the practical class and is worth 5% of your final
mark. Passing the practical is a hurdle requirement to pass this subject so you need to score across the 5
practicals a minimum of 25/50 which is converted to a mark out of 25%.
SAFETY
 Wash your hands after class.
 Dissecting instruments are used in this practical.
Use blunt probes and avoid cuts.
 If you have an existing cut or abrasion on your
hands please speak to your demonstrator
 Wear safety glasses at all times.
 At all times wear a lab coat and suitable shoes
with enclosed heel and toe that cover the foot.
 Always work to ensure your safety and the
safety of those around you.
 Immediately report any injuries or spills to a
demonstrator.
CONTENT
All animals use oxygen in order to access energy at a cellular level. The gas exchange surfaces and the
circulatory systems of vertebrate animals are responsible for supplying this oxygen and removing the
waste gas carbon dioxide. In this practical you will investigate the heart and lungs of a typical mammal.
 The structure of biological exchange surfaces
increases diffusion rates.
 The double circulation of the mammalian heart
delivers blood to both gaseous exchange
surfaces (lung) and the tissues of the body,
under pressure.
Biological concepts covered in this practical:
 Complex multicellular organisms require
specialised exchange surfaces and transport
systems to meet the needs of all their cells.
 The rate of diffusion across exchange surfaces
increases as permeability, surface area, and
pressure differences increase but is inversely
proportional to diffusion distance.
 Closed circulatory systems allow blood to move
under higher pressure unlike open circulatory
systems.
At the end of this practical you will be able to:


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Identify structures of the mammalian heart and
understand some of their function and control.
Recognise the features of an efficient gas
exchange surface.
BIOL10008/9 S1 2022 Prac 4 F2F
ACTIVITY 1: LUNGS – GAS EXCHANGE SURFACES
50 MINS
Practical task 1.1: Sheep pluck
The sheep pluck includes the major organs and vessels in
the thoracic (chest) cavity, the diaphragm and the liver, and
allows us to see their arrangement in situ. As the pluck
comes from an abattoir, many of the organs have been cut
to allow rapid blood drainage and to check for parasites or
disease. This allows us to see inside some of this tissue.
Task
Your demonstrator will provide an overview of the pluck
and the lung inflation. Observe that the lobes of the lung
appear on both sides of the pluck and have a very close
association with the heart which sits just to the left of the
midline, and the major vessels (also see Fig. 1).
Figure 1: Diagram showing blood vessel
connections between a heart and lungs of a
mammal.
Q1.1a Describe the appearance and texture of the
uninflated and inflated sections of the lungs – why does it change colour?
Q1.1b Considering the arrangement of organs in the thorax (chest cavity), why might the number of lobes
of lung be different on the two sides?
Pay close attention to the tracheae – both as it is located in its context, as well as in cross section. Observe
the cartilaginous rings around the front (anterior) of the sheep trachea. Gently touch the front of your own
throat and identify the C shaped cartilaginous rings. In humans, these almost fully encircle the trachea.
Q1.1c What role(s) does the cartilage serve in the upper airway? Why does the shape differ between
sheep and humans?
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BIOL10008/9 S1 2022 Prac 4 F2F
Practical task 1.2: Density of tissues
Different organs in the body are composed of tissues in different structural arrangements related to their
function. The lungs are the site of gas exchange whereas the liver filters toxins out of the blood as well as
producing bile (a digestive secretion). Consequently, we might expect these tissues to have different
tissues arranged in different ways and that this might affect the density of the tissue.
Task
Working in a group of 3-4, design a method to investigate the difference in density between of two tissue
types using the following materials:





1 piece of lung tissue
1 piece of liver tissue
Weighing scales
Graduated measuring cylinder
Large beaker
Q1.2a What does the initial position of the tissue in the cylinders tell you about the densities of the two
types of tissues?
Q1.2b Calculate the densities of the two tissues
Q1.2c Explain the differences in the density of the two tissues.
Q1.2d If the lung tissue is held underwater it eventually will sink to the bottom of the cylinder - why?
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BIOL10008/9 S1 2022 Prac 4 F2F
Practical task 1.3: Cellular structure of lung tissue
Figure 1.3 shows the respiratory components of the lung where gas
exchange occurs - primarily the alveoli. Histological sections
(showing microscopic anatomy) through the plane indicated by the
dashed line will contain these respiratory surfaces.
Task
For this task, you will access to a compound microscope and SLIDE
M25 - Lung tissue (H & E stain). Examine the cellular structure of
hematoxylin and eosin (H and E) stained lung tissue under low power.
Figure 1.3. Functional anatomy detail
Use the diagrams to help you identify features such as alveoli of the lung.
(singular is alveolus), alveolar ducts, capillaries and (if possible)
bronchioles. H and E stain is a mixture of two stains that is commonly used in histology. Nuclei are stained
blue and the cytoplasm and extracellular matrix are stained pink.
In the space below, draw a diagram of a section of the lung tissue in the space below, at magnification
x100. Try to select a section that has an alveolus, alveolar duct (linear open spaces), bronchiole (often lined
with darker tissue) and an artery, and clearly label these structures. Indicate the position of a capillary.
Checklist for drawings & diagrams
detailed
heading
realistic scale, magnification
scale bar ruled
all required
labels
ruled label
lines
4
label lines to
centre of
structure
label lines not structures not
crossed, without shaded etc.
arrowheads
large
drawing
BIOL10008/9 S1 2022 Prac 4 F2F
Mini-lung quiz
Identify the following structures depicted in the images below: arteriole (Art), vein (V), capillary (C),
bronchiole (B), alveolar duct (AD), alveoli (A). Your demonstrators will circulate to mark your work.
Q1.3a In the lung tissue, how do you distinguish between a capillary and an alveolar sac?
Q1.3b How might you distinguish between a vein and an artery? What is the significance of these
differences?
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BIOL10008/9 S1 2022 Prac 4 F2F
Q1.3c Bronchi and larger conducting bronchioles are lined with cilia. Suggest a reason for this.
To the right is an EM (electron
microscopy) picture of a very small
section of lung tissue, which should help
you visualise the close association
between the gas exchange surface and
the cardiovascular system.
Air space in
alveolus
Red blood
cell
Air space in
alveolus
10 µm
Q1.3d Using the EM image above, and the knowledge that the diameter of a red blood cell is 6-8μm,
estimate the distance gas travels from the alveolus to the red blood cell.
The rate of movement of molecules across a membrane or exchange surface such as the lung depends on
several factors. Fick’s Law describes the relationship between diffusion rate and these factors and states:
𝑅𝑎𝑡𝑒 𝑜𝑓 𝑑𝑖𝑓𝑓𝑢𝑠𝑖𝑜𝑛 ∝
𝑝𝑒𝑟𝑚𝑒𝑎𝑏𝑖𝑙𝑖𝑡𝑦 × 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 × 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑑𝑖𝑓𝑓𝑒𝑟𝑒𝑛𝑐𝑒
𝑑𝑖𝑓𝑓𝑢𝑠𝑖𝑜𝑛 𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒
Q1.3e. Having observed the lung tissue in the pluck and the histological section of normal tissue, describe
how the structure of the lung maximises the rate of diffusion according to Fick’s Law above.
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BIOL10008/9 S1 2022 Prac 4 F2F
Practical task 1.4: Abnormal lung tissue
Cancer is an example of abnormal tissue development. Rapidly proliferating cancer cells have a different
metabolism to normal cells. Cancer cells use increased glycolysis for energy and can build up high levels of
lactic acid because of this.
Hexokinase is an enzyme in the glycolysis pathway that is overexpressed in liver cancer cells. In the future,
targeting this metabolic pathway and the inhibition of this enzyme could be one way to check the growth of
some cancers.
Most patients with suspected cancers will have a biopsy taken. This means a small amount of tissue is
removed from the patient and observed under the microscope.
In this exercise you will be working individually to compare samples of normal and abnormal tissue. You
should make detailed observations of abnormal lung tissue that could lead to a diagnosis. If you want a
further challenge compare normal and abnormal liver tissue
Method
1. The slide “M25/B (human abnormal lung)” will be visible under low power magnification over the lab
monitors.
2. Observe the arrangement of tissue and note any differences when compared to the normal tissue.
3. If you have time examine and compare SLIDE M27 (human liver) and SLIDE M27/B (human abnormal
liver) will be visible on (iPad) microscopes already set-up in the lab. Ask your demonstrator to direct
you.
As you observe your samples, use the below space to list the differences between the two with respect to
both tissue organisation and, if time permits, cell structure (you will need to use high power for this).
Q1.4a. How would the changes in structure observed in slide M25/B affect gas exchange in the lung?
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BIOL10008/9 S1 2022 Prac 4 F2F
ACTIVITY 2: THE HEART
75 MINS
Practical task 2.1: Heart dissection
The heart of a vertebrate is myogenic, meaning that it is able to beat in the absence of nerve stimulation.
Cardiac muscle cells have the intrinsic property of spontaneously contracting and can rapidly conduct
electrical signals. The heart has a pacemaker region that triggers an electrical wave to move across the
atria and then the ventricles in an orderly sequence. This ensures that the atria contract simultaneously,
filling the ventricles, and then the ventricles contract, expelling blood from the heart to either the lungs or
the rest of the body.
Task
Work in pairs to complete the dissection of the sheep’s heart. Some students may feel unwell – keep an
eye on each other and call for assistance when necessary.
Equipment:
 1 heart per pair
 wooden dissecting board
 dissecting scissors (blunt ended)
 dissecting probe (blunt ended)
EXTERNAL FEATURES
Lay the heart ventral side up as shown in the photograph (Figure
2.1a).
Note: Some of the major blood vessels normally protruding from the
base of the heart (which is at the top of Figure 2.1a) may be missing.
Use your finger or a probe to work out which vessel is connected
to each chamber of the heart. This information can be used to
identify the vessels.
Figure 2.1a: Sheep heart, ventral view
Identify the following:
 Interventricular and atrioventricular grooves - mainly filled
with fat.
 Pulmonary artery – emerges from right ventricle.
 Aorta – emerges from left ventricle.
 Venae cavae - posterior and anterior, open into right atrium.
 Pulmonary veins – open into left atrium.
 Coronary vessels - visible on the surface of the heart. These supply blood to the heart wall.
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BIOL10008/9 S1 2022 Prac 4 F2F
!
!
!
!
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PROCEDURE: OPENING THE RIGHT SIDE OF THE HEART
Step 1:
Cut off the apex of the heart at the line in the diagram to expose the
two ventricular cavities. Note that the right ventricle does not reach to
the apex. Make the first cut at an angle so that it opens both the left
ventricle and right ventricle.
1
Identify the thin-walled chamber (this is the right ventricle).
Apex of right
ventricle
Apex of left
ventricle
Step 2:
Cut through the ventral wall of the right ventricle parallel to and close
to the inter-ventricular groove.
Step 3:
Continue the cut to the left, along the atrioventricular groove as far as
the pulmonary artery, then cut through the wall of the right atrium
and anterior vena cava.
Turn back the V-shaped flap to expose the lumen of the right ventricle
and the right atrium.
Step 4:
Cut open the pulmonary artery. Note the three parts of the
pulmonary semilunar valve, which prevents back-flow of blood when
the ventricle relaxes.
Figure 2.1b. Sheep heart, dissected
ventral view
Identify the following features:
 Venae cavae (if present).
 Interatrial septum – divides the right and left atrium and contains a thin area (fossa ovalis). Before
birth blood flows from right to left atria through a hole called the foramen ovale. The fossa ovalis is
created when this hole becomes sealed.
 Coronary sinus - posterior to the fossa ovalis. This is the main vessel returning blood from the heart
wall.
 Septomarginal trabecula - between the interventricular septum and ventricle wall. It has a function in
electrical conduction.
 Tricuspid valve – three thin, transparent flaps of tissue which, when the ventricle contracts, are forced
up to close the atrioventricular opening.
 Chordae tendineae - attaches the valve flaps to papillary muscles on the ventricle walls. These are the
‘strings’ of the ‘parachute valves’
 Pulmonary artery - leaving the ventricle.
 Pulmonary semilunar valve, which prevents back-flow of blood when the ventricle relaxes.
9
"
&'
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BIOL10008/9 S1 2022 Prac 4 F2F
PROCEDURE: OPENING THE LEFT SIDE OF THE HEART
Step 5:
Open the left ventricle: make an incision in the ventral wall of the
ventricle parallel to and 1cm from the interventricular groove as
shown in the diagram.
Step 6:
Open the left atrium: make a vertical cut on the ventral surface to
expose the left atrium. Note the opening of the two pulmonary
veins (these have no valves).
Step 7:
Open the aorta. Push a probe from the left ventricle upwards until
it emerges from the aorta. Use this as a guide to cut through the
muscle and open the aorta as shown.
Figure 2.1b. Sheep heart, dissected
Identify the following features:
 Bicuspid (mitral) valve - similar in appearance and function to the tricuspid valve, but with 2 flaps
rather than 3.
 Aorta leaving the ventricle.
 Chordae tendineae, which attach the valve flaps to papillary muscles on the ventricle walls.
 The 3 ‘pockets’ of the aortic semilunar valve at its base.
 Opening of two coronary arteries just beyond the semilunar valve.
Q2.1a. How can the difference between the thickness of the right ventricle and the left ventricle wall be
explained in terms of heart function?
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BIOL10008/9 S1 2022 Prac 4 F2F
IDENTIFYING THE STRUCTURES OF THE HEART:
□ Aorta
□ Left atrium
□ Atrioventricular groove
□ Left ventricle
□ Aortic semilunar valve
□ Papillary muscles
□ Bicuspid (mitral) valve
□ Pulmonary artery
□ Chordae tendineae
□ Pulmonary semilunar valve
□ Coronary arteries (openings to)
□ Pulmonary veins
□ Coronary sinus
□ Right atrium
□ Coronary vessels
□ Right ventricle
□ Interatrial septum (AND fossa ovalis)
□ Septomarginal trabecula
□ Interventricular grooves
□ Tricuspid valve
□ Interventricular septum
□ Venae cavae
IMPORTANT: You will also be expected to be familiar with the function of each structure for
your assessment
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BIOL10008/9 Summer 2022 Prac 4
Practical task 2.2: Heart rate data – heart function
The rate of the heart (bpm: beats per minute) is set by a group of modified muscles cells (myocytes) found
in the right atria – the sinoatrial node (SA node) or pacemaker. These cells produce an automatic, rhythmic
beat which can occur in the absence of any external input - the intrinsic rate of the heart. This is what
allows us to be able to perform heart transplants and have a donor heart continue to beat inside another
person. Normally however, the intrinsic heart rate is modified by both nerves and hormones. This
arrangement allows the heartrate to be increased or decreased in response to a variety of stimuli or
scenarios.
You have contributed heart rate data to the class data set. From this we will be able to see what happens
when you stand up suddenly after a period lying down, and how the heart rate changes with exercise.
These two interventions stimulate changes in heart rate due to different reasons:


Standing up from lying down causes a transitory pooling of blood in the lower extremities –
postural hypotension. The body detects this as a decrease in blood pressure (and hence flow) to
the brain and responds by increase the rate of the heart.
Exercise requires more oxygen to be delivered to working muscles, so the heart rate increases to
enhance blood flow round the body.
Means and standard deviations for the class dataset will be displayed in class. Copy these below:
Lying down
Stood up
At rest
Exercise
Mean
Standard deviation
Task
Plot these data using a column graph with error bars. Instead of adding a title, include a figure caption
below the figure. This is a standalone statement which (briefly) tells the reader what the data shows.
A figure caption should contain:
 a name (e.g. Figure 1.)
 a statement about what your figure shows;
 a brief description about how the data was obtained - the minimum to understand what the figure
is showing;
 any relevant statistical information e.g. n numbers, any tests performed etc
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BIOL10008/9 Summer 2022 Prac 4
Q2.2a Calculate the percent change in heart rate in the two interventions
Q2.2b Based on these data, which of the two interventions is the stronger stimulus to change heart rate?
Q2.2c In each case, what is the change in heart rate responding to?
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BIOL10008/9 Summer 2022 Prac 4
Q2.2d What other factors might affect the change in heart rate in these interventions? (Hint: if you were
doing this as a controlled experiment, what might you want consider?).
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