Transcript File - Thomas Tallis Science

Starter- Structure of the thorax
Put them in the correct order
Nose
Terminal bronchioles
Secondary bronchi
Alveoli, alveolar ducts and alveolar air sacs.
Right and left primary bronchi
Tertiary bronchi
Trachea
The structure of the thorax
Nose
Trachea / Windpipe,
Right and left primary bronchi
Secondary bronchi,
Tertiary bronchi
Terminal bronchioles
Alveoli, alveolar ducts and alveolar air sacs.
AS Biology- Module 2
The mammalian lung
This lesson you should be able to…
Grade C- Describe the features of the
mammalian lung that adapt it to efficient gas
exchange.
Grade B – Outline the mechanism of ventilation.
Grade A/A* - Describe and explain the
distribution and functions of the different
tissues found in the lungs.
O2 from the atmospheric air entering the alveoli enters
the blood by diffusion across the alveolar wall down its
concentration gradient
Total barrier to diffusion is less than 1
um
CO2 from the blood enters the alveoli by diffusion across the
alveolar wall down its concentration gradient
Oxygenated blood to
heart via pulmonary vein
Low CO2 concentration
Surfactant produced by alveoli –
reduces cohesive surface tension forces
between H2O molecules in film of H2O
ST forces may cause collapse of alveoli
during exhalation – prevented by
surfactant
Diffusion gradient maintained by
rhythmic ventilation (replaces air in
alveoli) and a rich blood supply - high
[O2] on supply side (alveoli); low [O2]
on demand side (capillaries) – vice
versa for CO2
Squamous (flattened)
epithelium
O2
CO2
Deoxygenated blood from
heart via pulmonary artery
High CO2 concentration
Capillaries
Close contact with alveolar wall
1 cell thick – short diffusion distance
Narrow – space enough for passage of single
RBC – allows close contact with capillary wall
Large surface area – numerous and tubular
Alveoli – spherical and numerous (600
million); large surface area (c.70 m2)
Film of H2O
– dissolves gases
- evaporates
Alveolus wall
Capillary wall
Plasma – carries 85% of CO2 as
hydrogen carbonate ions, 5%
dissolved in plasma, and 10% in
combination with haemoglobin
Each 1 cell
thick
RBC’s – contain haemoglobin carries O2 as oxyhaemoglobin
The structure of the thorax
1.
6.
3.
7.
8.
4.
5.
9.
10.
The structure of the thorax
C-shaped
cartilage
Trachea
Right lung
Left
lung
Intercostal
muscle
Rib
Bronchus
Bronchiolus
Diaphragm
Adaptations of Respiratory System
for Gas Exchange
• Cleans, warms, and moistens the air entering the respiratory tract during
inhalation – achieved by hairs, mucus, and blood capillaries (warm blood)
in the nasal cavity and cilia in the trachea
• A large number of spherical alveoli (600 million) 100-300 um across –
giving a large surface area of approx.80-100 m2 for rapid gas exchange
between the blood and atmosphere; alveolar wall is one cell thick
(squamous epithelium) – short diffusion path between alveoli and blood
in the pulmonary capillaries
• Numerous and tubular capillaries in close contact with alveoli - wall also
made of squamous epithelium and one cell thick; total diffusion distance
is less than 1 um
• Capillaries are narrow – red blood cells are squeezed against the capillary
wall – making contact with the wall to reduce diffusion distance. The
blood cells are also slowed down – increasing the time for exchange
Adaptations of Respiratory System
for Gas Exchange
• Constant ventilation - replacing the air in the alveoli to maintain
a concentration gradient between the alveolar air and the blood
• Alveoli are surrounded by a large number of capillaries – a rich
blood supply, replaces the blood constantly, to maintain a
concentration gradient between the blood and alveolar air.
• Haemoglobin (Hb) in red blood cells carries oxygen and has a
high affinity for oxygen – helps in maintaining a steep
concentration gradient for oxygen
• Moist exchange surface – allows gases to dissolve
• Water in the alveoli contains a surfactant (phospholipid) –
reduces surface tension – prevents collapse of alveoli
• Alveoli contain phagocytic cells - for defence
Respiratory Tree
Atmospheric air
Direction of air flow
during inhalation
Larynx (“voice box”)
Trachea
Bronchus (2)
Bronchioles
Direction of air flow
during exhalation
Alveoli (“air sacs”)
Site of gas exchange
Gases exchanged by diffusion down their concentration gradients
O2 from alveoli to blood in alveolar capillaries
CO2 from blood into alveoli (for excretion)
Capillaries (blood)
Red blood cells transport absorbed O 2 from lungs to body tissues
CO2 transported from tissues to lungs for excretion
10
GAS EXCHANGE
...describe with the aid of diagrams and photographs, the distribution
of cartilage, ciliated epithelium, goblet cells, smooth muscle and
elastic fibres in the trachea, bronchi, bronchioles and alveoli of the
mammalian gaseous exchange system
Rings of cartilage in
the walls of the
trachea and bronchi
provide support
It is strong but
flexible
It stops the trachea
and bronchi
collapsing when
pressure drops
Structural components of the
respiratory system
Trachea
Smooth muscle
Elastic fibres
C-shaped rings
of cartilage
Fill in the functions
Smooth muscle and elastic
fibres in the trachea
Smooth muscle is found in
the walls of the trachea,
bronchi and bronchioles
Smooth muscle relaxes
during exercise, widening
the lumen
Results in less resistance
to airflow
Elastic fibres stretch on
inspiration and recoil to
help push air out when
exhaling
Describe and explain the distribution and functions of the different
tissues found in the lungs.
Structure
Cartilage
Function/Characteristics
Structural components of the
respiratory system
Inside surface
of trachea –
epithelial lining
Goblet (mucus)
cells
Ciliated
epithelium
Loose tissue
Fill in function
Ciliated epithelium
Simple columnar epithelial cells
Fine hair-like outgrowths
Rapid, rhythmic, wavelike beatings
Movement of mucus
Usually found in the air passages like the nose, uterus
and fallopian tubes
Ciliated epithelium
Cilia beat the mucus
Helps to prevent lung
infections
Goblet cells
Specialised as gland cells
Synthesising and secreting mucus
Goblet cells
Secrete mucus
Mucus traps
microorganisms and dust
particles in inhaled air
Small intestine
(absorption of nutrients)
Liver
(Sugar levels adjusted)
Examples of specialised
exchange surfaces
Root hair of plants
(water and minerals absorbed)
Hyphae of fungi
(nutrients absorbed)
TASK -Look at the diagrams below.
Draw a table to describe the function and
characteristics for each part.
(a) Bronchiole and (b) trachea in transverse section
Cross section of bronchiole
Alveolus wall
 Thin - single cell thick
 Squamous epithelium
 Reduces diffusion
distance
Bronchiole wall
 Ciliated epithelium
(cilia
move mucus upwards)
 Goblet cells (secrete
mucus)
Blood capillary
 Close to alveoli
 Thin - single cell thick
 Squamous epithelium
 Reduces diffusion distance
Pulmonary vein
 Carries oxygenated blood to heart
(a) Bronchiole and (b) trachea in transverse section
(a) Bronchiole and (b) trachea in transverse section
Structure
Function/Characteristics
Cartilage
Smooth
muscle
Elastic fibres
Goblet cells
and glandular
tissue
Ciliated
epithelium
Bronchi
Bronchioles
.
Exam Question
4.
The diagram below shows the detailed structure of a small part of the
mammalian lung.
D
E
(i)
State the name of the structure shown between lines D and E.
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[1]
Exam Question
List three features of the structure which you have identified in (i) which make it suitable
for gas exchange.
1 ......................................................................................................................
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2 ......................................................................................................................
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3 ......................................................................................................................
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[3]
[Total 4 marks]
Exam Question
5. The different parts of the gaseous exchange system, such as the bronchi, show
structural adaptations to their functions. The diagram below shows a section through
the wall of a bronchus as seen with a light microscope.
cilia
g lo b le t ce lls
ca rtila g e
sm o o th m u s cle
Exam Question
(a)(i)State one function for each of the following components of the bronchus wall.
goblet cell ...............................................................................................
................................................................................................................
cartilage .................................................................................................
................................................................................................................
[2]
(ii)State two ways in which the structure of the wall of the bronchus would be different in a
long-term smoker.
1 .............................................................................................................
................................................................................................................
2 .............................................................................................................
................................................................................................................
[2]
Exam Question
(b)
Gaseous exchange occurs across the walls of the alveoli.
Explain why the walls of the alveoli contain elastic fibres.
.........................................................................................................................
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.........................................................................................................................
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[2]
Exam Question
(c)
One feature of the disease emphysema is that the alveoli lose their elasticity.
Explain the effects of this loss of elasticity on the gaseous exchange system of a
person with emphysema.
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[4]
[Total 10 marks]
The lungs and associated structures
© Pearson Education Ltd 2008
This document may have been altered from the original
The lungs and associated structures
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3.
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© Pearson Education Ltd 2008
This document may have been altered from the original
Ventilation
The ribcage, intercostal muscles and diaphragm all work together to move air into and
out of the lungs, where gas exchange occurs across the thin (single-celled) walls of the
alveoli
Ventilation is a physical process, relying on the principle of Boyle’s Law – which state
“Pressure is inversely proportional to volume”
The mechanism can be illustrated using a bell jar model of the respiratory system –
however, the model does not illustrate involvement of the rib cage and the intercostal
muscles in ventilation
Breathing out
(expiration /
exhalation)
Internal intecostals contract
in forced expiration
Breathing in
(inspiration
/ inhalation)
INSPIRATION
EXPIRATION
Atmospheric pressure = 760 mmHg
Diaphragm & external intercostals
contract
Rib cage raised (upwards and outwards)
Diaphragm lowered (becomes flatter)
Volume of chest cavity increases
Pressure in chest cavity drops to below
atmospheric pressure to 758 mmHg
Diaphragm & external intercostals relax
Rib cage lowered
Diaphragm raised (dome shape) due to push
from abdominal organs
Volume of chest cavity decreases
Pressure in chest cavity increases to
above atmospheric pressure to763 mmHg
Air moves into lungs from atmosphere
Active process
Air forced out of lungs into atmosphere
Aided by elastic recoil and abdominal organs
Passive process
Inhaling (Inspiration)
Exhaling (Expiration)
Volume of thorax
Diaphragm muscle
Diaphragm
Relaxes and resumes
to dome shape
External
intercostal
muscles
Rib cage
Pressure in chest
cavity
Movement of air
Decreases below
atmospheric pressure
Inhaling (Inspiration)
Exhaling (Expiration)
Volume of thorax
Increases
Decreases
Diaphragm muscle
Contracts
Relaxes
Diaphragm
Flattens and pushes
digestive organs down
Relaxes and resumes
to dome shape
External
intercostal
muscles
Contracts/expands
Relaxes
Rib cage
Upward and outward
Inward and downward
Pressure in chest
cavity
Decreases below
atmospheric pressure
Increases below
atmospheric pressure
Movement of air
Into the lungs down
pressure gradient
Air forced out of lungs
Exam question (5 marks)
Exam Questions - OCR
Name five tissues, cells or cell structures
found in the mammalian gas exchange
system and explain the function of each
[5 marks]
Name five tissues, cells or cell structures found in the mammalian
gas exchange system and explain the function of each
[5 marks]
-Goblet cells secrete mucus, the mucus traps bacteria and dust particles
-Some cells are ciliated, cilia move mucus towards the throat to be
removed
-Elastic fibres stretch on inspiration and recoil at expiration
-Smooth muscle relaxes to make air passages wider when exercising
-Cartilage provides support and keeps trachea open