1 of 28 Boardworks Ltd 2008 Specification reference

1 of 28 © Boardworks Ltd 2008

Specification reference • (a) explain, in terms of surface area: volume ratio, why multicellular organisms need specialised exchange surfaces and single-celled organisms do not (HSW 1); • (b) describe the features of an efficient exchange surface, with reference to diffusion of oxygen and carbon dioxide across an alveolus; • 2 of 28 © Boardworks Ltd 2008

Little george and mum 3 of 28 © Boardworks Ltd 2008

Little george Loss of appetite 4 of 28 © Boardworks Ltd 2008

Change in colour of the skin 5 of 28 © Boardworks Ltd 2008

Wheezy chest 6 of 28 © Boardworks Ltd 2008

Is it efficient? • Is the mammalian lung the most efficient design? • Discuss!! Firstly discuss what you already know about the mammalian lung. Can you come up with any flaws? 7 of 28 © Boardworks Ltd 2008

Classifying and analysing • Cut out these pictures and classify them in terms into groups of organisms that you think have similar respiratory functions. • Write a list. What features do they all have in common? 8 of 28 © Boardworks Ltd 2008

Strange thick green faeces 9 of 28 © Boardworks Ltd 2008

flatworm 10 of 28 © Boardworks Ltd 2008

earthworm 11 of 28 © Boardworks Ltd 2008

frog Carbon dioxide 2. 5 times as fast!! 12 of 28 © Boardworks Ltd 2008

eel 13 of 28 © Boardworks Ltd 2008

External gill amphibian 14 of 28 © Boardworks Ltd 2008

Internal gills 15 of 28 © Boardworks Ltd 2008

Fish gills 16 of 28 © Boardworks Ltd 2008

Counterflow system 17 of 28 © Boardworks Ltd 2008

Insects- arthropods 18 of 28 © Boardworks Ltd 2008

Bird lung system 19 of 28 © Boardworks Ltd 2008

Features of an efficient gaseous exchange system • Large surface area Exchange surface should be thin Diffusion gradient Surfaces should be wet 20 of 28 © Boardworks Ltd 2008

Unicellular v multicellular • • 1) Draw: - a 1 cm cube - a 2 cm cube - a 3 cm cube • 2) Calculate the surface area of each cube • 3) Calculate the volume of each cube • 4) Calculate the SA: V ratio • SA: V = SA • V 21 of 28 © Boardworks Ltd 2008

22 of 28 © Boardworks Ltd 2008

Which has more fat? 23 of 28 © Boardworks Ltd 2008

Exchange surfaces All organisms require nutrients and the ability to excrete waste. Many simple organisms, such as bacteria and sea anemones, can exchange substances directly across their external surfaces. Larger organisms require specialized gas exchange and transport systems to transport substances such as oxygen and nutrients to their cells efficiently. Fish exchange these substances across gills, while insects have openings called spiracles on their surfaces. In mammals, gas exchange occurs in the lungs, and in particular the alveoli. 24 of 28 Crop photo © Boardworks Ltd 2008

25 of 28 © Boardworks Ltd 2008

Exam specification • (c) describe the features of the mammalian lung that adapt it to efficient gaseous exchange; • (d) describe, with the aid of diagrams and photographs, the distribution of cartilage, ciliated epithelium, goblet cells, smooth muscle and elastic fibres in the trachea, bronchioles and alveoli of the mammalian gaseous exchange system; • (e) describe the functions of cartilage, cilia, goblet cells, smooth muscle and elastic fibres in the mammalian gaseous exchange system; • 26 of 28 © Boardworks Ltd 2008

Elephant respiratory system 27 of 28 © Boardworks Ltd 2008

ISA skills • AIM: • Effect of surface area: volume ratio on diffusion rate • Procedure: • Work through the instructions with your learning buddies. • Follow through the practical writeup 28 of 28 © Boardworks Ltd 2008

ASBESTOS POISONING WHITE BOARDS RECAP 29 of 28 © Boardworks Ltd 2008

RESPIRATORY SYSTEM VIDEO Pluck dissection 30 of 28 © Boardworks Ltd 2008

Structure of the lungs 31 of 28 © Boardworks Ltd 2008

Gas exchange in the alveoli 32 of 28 © Boardworks Ltd 2008

• Inhalation and exhalation 33 of 28 © Boardworks Ltd 2008

The mechanism of ventilation 34 of 28 © Boardworks Ltd 2008

Summary of ventilation Part of respiratory system inhalation exhalation diaphragm Rib cage External intercostal muscles Internal intercostal muscles 35 of 28 © Boardworks Ltd 2008

HISTOLOGY OF CELLS 36 of 28 © Boardworks Ltd 2008

trachea 37 of 28 © Boardworks Ltd 2008

Trachea cross section Trachea Cross Section One of the special features of the Trachea is the PCC (pseudostratified ciliated columnar) on the internal surface which keeps the air passage clear of debris. Another is the hyaline cartilage C -rings that keep the trachea open. 38 of 28 Note also the mucous glands emptying mucous into a duct which carries it to the surface. This also aids in trapping debris that enters the trachea. © Boardworks Ltd 2008

Trachea cross section-epithelial cells The ciliaon the surface along with mucus cause the debris that enters the trachea to move back up to the epiglottis --> esophagus --> to the GI tract. The lamina propriaunder the PCC is made of strong flexible fibroelastic tissue 39 of 28 © Boardworks Ltd 2008

40 of 28 © Boardworks Ltd 2008

Trachea cross section-cartilage The dark violet hyaline cartilage C-ringswill not allow the tracheal air passage to collapse. The rings are open on the posterior side of the trachea which is adjacent to the esophagus. This open surface allows for more flexibility when functioning with the esophagus which is collapsed except when food is moving through 41 of 28 © Boardworks Ltd 2008

Trachea cross section – goblet cells Mucus is a thick sticky substance that acts in collecting debris for swallowing. Serous fluidis a thinner runny substance that is mainly for keeping the epithelial tissue moist and lubricated. 42 of 28 © Boardworks Ltd 2008

Comparing the physiology of respiratory system Part of the lung 43 of 28 Cross sectin drawing Cartilage Smooth Present muscle shape present Elaatic fibre Goblet fibre epithliu m © Boardworks Ltd 2008

Comparing the physiology of respiratory system Part of the lung Cartilage Smooth Present muscle shape present Elaatic fibre Goblet fibre epithliu m trachea C shaped yes yes Ciliated cells bronchi Yes irregular pattern yes yes Ciliated cells bronchiol e no yes yes alveoli no yes no Flattened epitheliu m 44 of 28 Cross sectin drawing © Boardworks Ltd 2008

Maintaining the structure of the alveoli During inhalation, the chest cavity increases in volume, lowering the pressure in the lungs to draw in fresh air. This decrease in pressure leads to a tendency for the lungs to collapse. Cartilage keeps the trachea and bronchi open, but the alveoli lack this structural support. Lung surfactant is a phospholipid that coats the surfaces of the lungs. Without it, the watery lining of the alveoli would create a surface tension, which would cause them to collapse. 45 of 28 alveoli surfactant © Boardworks Ltd 2008

Keeping the airways clear The walls of the trachea and bronchus contain goblet cells, which secrete mucus made of mucin. This traps microorganisms and debris, helping to keep the airways clear. The walls also contain ciliated epithelial cells, which are covered on one surface with cilia. These beat regularly to move micro-organisms and dust particles along with the mucus. They contain many mitochondria to provide energy for the beating cilia. 46 of 28 © Boardworks Ltd 2008

Structures of the human lung 47 of 28 © Boardworks Ltd 2008

Why do we breathe? Animals need to maintain a concentration gradient across their exchange surfaces so that oxygen will diffuse into the blood and carbon dioxide will diffuse out. Fish manage this by keeping a continuous stream of oxygenated water moving over their gills. In animals such as mammals and birds, a concentration gradient is maintained in the alveoli by the mechanism of ventilation. 49 of 28 © Boardworks Ltd 2008

The pleural cavity Each of the lungs is enclosed in a double membrane known as the pleural membrane. The space between the two membranes is called the pleural cavity, and is filled with a small amount of pleural fluid. lung This fluid lubricates the lungs. It also adheres to the outer walls of the lungs to the thoracic (chest) cavity by water cohesion, so that the lungs expand with the chest while breathing. pleural membranes 50 of 28 © Boardworks Ltd 2008

Composition of inhaled/exhaled air composition (%) In one breathing cycle, the air in the lungs loses only some of its oxygen content. This is why mouth-to-mouth resuscitation can be effective. 90 78% 80 70 60 50 40 30 20 10 0 N 2 51 of 28 inhaled air exhaled air 21% 15% 0. 04% 4% O 2 CO 2 <1% 3% <1% H 2 O other © Boardworks Ltd 2008

Spirometry 52 of 28 © Boardworks Ltd 2008

Spirometric terms 53 of 28 © Boardworks Ltd 2008

Haemoglobin is a protein making up 95% of the dry mass of a red blood cell. It is the means of transport of oxygen around the body. Haemoglobin is made up of four polypeptide chains, each bound to one haem group. Each haem group can combine with one oxygen molecule, so that one molecule of haemoglobin can combine with a maximum of four oxygen molecules. This forms oxyhaemoglobin. polypeptide chain 55 of 28 © Boardworks Ltd 2008

How is oxygen concentration measured? Oxygen binds to haemoglobin when oxygen is at a high concentration, and dissociates from haemoglobin when oxygen is at a low concentration. The concentration of a gas in a mixture of gases can be quantified in terms of its partial pressure. This is the amount of pressure exerted by the gas relative to the total pressure exerted by all the gases in the mixture. Partial pressure is measured in kilopascals (k. Pa) and is written as P(O 2), P(CO 2), etc. 56 of 28 © Boardworks Ltd 2008

The oxygen dissociation curve 57 of 28 © Boardworks Ltd 2008

Factors affecting oxygen dissociation 58 of 28 © Boardworks Ltd 2008

Foetal haemoglobin The red blood cells in the foetal bloodstream contain a special form of haemoglobin known as foetal haemoglobin. This helps maximize oxygen uptake from the mother’s blood stream, which has already lost some of its oxygen by the time it reaches the placenta. 59 of 28 100 90 80 70 60 50 40 30 20 10 0 foetal haemoglobin oxyhaemoglobin (% saturation) Foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin 0 2 4 6 8 10 12 14 oxygen partial pressure (k. Pa) © Boardworks Ltd 2008

What is myoglobin? Myoglobin is a molecule with a similar structure to haemoglobin, but with only one haem group. This means oxymyoglobin will only dissociate when oxygen levels are low. It is found in muscle cells, where it acts as an oxygen reserve. 60 of 28 100 90 80 70 60 50 40 30 20 10 0 myoglobin oxyhaemoglobin (% saturation) Myoglobin has a very high affinity for oxygen, even at very low partial pressures. haemoglobin 0 2 4 6 8 10 12 14 oxygen partial pressure (k. Pa) © Boardworks Ltd 2008