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BIOL10008/9 Sum2023 Prac 4 Online Student

PRACTICAL 4: HEART AND LUNGS

Before 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

Activity

0:00 – 0:10

Welcome and introduction to Practical 4

0:10 – 1:25

Activity 1: Lungs  Gas Exchange Surfaces

Practical task 1.1: Exchange surfaces

Practical task 1.2: Density of Tissues

Practical task 1.3: Cellular Structure of Lung Tissue Practical task 1.4: Abnormal Lung Tissue

(60 mins + debrief)

1:25 – 2:45

Activity 2: The heart

Practical task 2 .1: Cardiac anatomy

Practical task 2.2: Heart rate data heart function               Practical task 2.3: Exercise and heart rate heart function

(20 mins) (25 mins + debrief) (20 mins + debrief)

After prac

Online Practical 4 Assessment

Timed MCQ quiz: 15 minutes, 10 marks, 5% of subject grade

ASSESSMENT

10 marks: Online assessment based on material covered during the practical class. 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%.

CONTENT

All animals use oxygen 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.

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.

•  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.

At the end of this practical you will be able to:

•   Identify structures of the mammalian heart and understand some of their function and control.

•   Recognise the features of an efficient gas exchange surface.

 

ACTIVITY 1: LUNGS  GAS EXCHANGE SURFACES                                                              45 MINS

Practical task 1.1: Exchange surfaces

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

In Canvas, view the video of the pluck overview 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).

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 the lung be different on the two sides?

In Canvas, look at the histological sections of the sheep and human tracheae observing the U shaped- arrangement of cartilage around the front 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?

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 this might affect the density of the tissue.

Task

Bearing in mind the different functions of the liver and the lung, use the interactive video in Canvas to examine the density of the two organs and complete the following:

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?

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. 

In Canvas, have been given access to a virtual microscopy slide (“Lung

Human”) to examine the cellular structure of hematoxylin and eosin

(H and E) stained lung tissue under low power and learn to identify

features   such   as   alveoli   (singular   is   alveolus),   alveolar   ducts,

capillaries and (if possible) bronchioles. H and E stain is a mixture of

two stains that are 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, 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. Post your drawing on the class Padlet.

Checklist for drawings & diagrams

 

detailed heading

 

realistic scale, scale bar ruled

 

magnification

 

all required labels

 

ruled label lines

 

label lines to the centre of the structure

 

label lines not

crossed, without

arrowheads

 

structures not shaded etc.

 

large  drawing

Mini-lung quiz

Identify the following structures depicted in the images below: arteriole (Art), vein (V), capillary (C), bronchiole (B), alveolar duct (AD), and alveoli (A).

 

 

 

 

 

 

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?

Q1.3c   Bronchi and larger conducting bronchioles are lined with cilia. Suggest a reason for this.

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. Ficks Law describes the relationship between diffusion rate and these factors and states:

Rate of diffusion 

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.

Practical task 1.4: Abnormal lung tissue

On Canvas, examine the virtual microscopy image of abnormal pulmonary (lung) tissue slide                       (“ Lung_Adeno_CA”). Identify the major differences between the abnormal and the normal lung tissue in the space below.

Q1.4a  Observe the Covid19 lung slide image on Canvas. Describe the differences compared to normal lung tissue and with reference to Fick’s Law, suggest how this disease might affect gas exchange rates.

Q1.4b  Observe the emphysemic lung slide image on Canvas. Describe the differences compared to normal lung tissue and with reference to Fick’s Law, suggest how this disease might affect gas exchange rates.

ACTIVITY 2: THE HEART

65 MINS

Practical task 2.1: Cardiac anatomy

The mammalian heart is a complex organ that comprises four chambers: two atria (singular: atrium) and two ventricles. When heart chambers contract, they squeeze the blood, putting it under pressure and       causing it to flow. One-way valves prevent the backflow of blood as the heart chambers cycle between     contraction and relaxation. Blood is pumped from the heart to both the lungs (pulmonary circuit) and the rest of the body (systemic circuit).

Task

In Canvas, complete the drag-and-drop activity to match the various anatomical structures with the appropriate names.

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 muscle 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's heart continue to beat inside another person. Normally, however, the intrinsic heart rate is modified by both nerves and hormones. This                arrangement allows the heart rate to be increased or decreased in response to a variety of stimuli or            scenarios.

The heart rate data you contributed as a part of the practical 4 preparation have been collated into the       class data set. From this, we will be able to see what happens when you stand up suddenly after a period   of 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 increasing the rate of the heart.

•   Exercise requires more oxygen to be delivered to working muscles, so the heart rate increases to enhance blood flow around the body.

Task

Access the data in Canvas. You will calculate the means and standard deviations of the dataset you have  contributed to and plot this using a column graph with error bars. You will also generate a figure caption  which is a standalone statement that (briefly) tells the reader what the data shows. You can prepare your graph in Excel or on the graphing paper on the next page.

A figure caption should contain:

•     a name (e.g. Figure 1.)

•     a statement about what your figure shows;

•    a brief description of 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

 

Q2.2a  Calculate the percentage 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?

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 to consider?).

Practical task 2.3: Exercise and heart rate  heart function

As mentioned earlier, the heart rate can be affected by both neural input and circulating hormones. We can examine some of these effects experimentally. Propranolol blocks beta-adrenergic receptors in the  heart: activation of these receptors increases heart rate. Adrenalectomy removes the adrenal gland; a   source of adrenaline and noradrenaline, which both activate beta-adrenergic receptors.

In an experiment to investigate the heart rate in exercise, 25 moderately active individuals aged 20-26 had their heart rates (bpm) measured in three different scenarios:

•     Resting-state - during exercise

•     Propranolol treatment (a drug) : Resting state - during exercise

    Adrenalectomy (surgical removal of the adrenal gland) : Resting state - during exercise

Tasks

•     Access the data in Canvas, then plot the data and write a figure caption, either in Excel or hand-drawn below.

    Answer the questions associated with this activity WITHOUT looking up the treatments

 

Q2.3a  What does the control data tell you?

Q2.3b  What does the propranolol data tell you?

Q2.3c  What does the adrenalectomy data tell you?

Q2.3d  What do the resting-state heart rate values tell you?