Chapter 7 - Exchange Surfaces Flashcards
why don’t elephant sized insects exist?
- insects have exoskeletons
- carrying a thick & tough exoskeleton requires a lot of energy - high energy demand
- if insects were bigger, the Vol of O2 required would be very large to meet the demands
insects DO NOT exchange gases via _____?
BLOOD
- contain a liquid called hemolymph that transports the products of digestion to their cells NOT O2
-
what do insects have that delivers O2 and removes CO2?
a tracheal system
why do large, multicellular active organisms need specialised exchange surfaces, and small unicellular organisms don’t?
they have different SA:V
small organisms have a ___ SA:V
small organisms have a large SA:V e.g. amoeba, paramecium
large organisms have a ___ SA:V
small ,e.g. elephants, humans, ect
all cells?
- have a demand for e.g. O2, glucose, AAs ect..
- these molecules come from outside the organism - their environment
{diffusion} organisms w a large SA:V
- Organisms w a large SA:V e.g. amoeba obtain these molecules by diffusion directly from the environment - DIFFUSION IS SUFFICIENT TO SUPPLY THE DEMANDS
{diffusion} organisms w a small SA:V?
- organisms w a small SA:V e.g. humans, elephants, ect. need specialised exchange surfaces to supply demand for these molecules. DIFFUSION IS NOT SUFFICIENT TO SUPPLY DEMAND
Exchange surfaces are adapted to?
- exchange surfaces are adapted to maximise the rate of diffusion across them
- this is summarised by Fick’s law
Fick’s law:?
Rate of diffusion = (SA x Conc gradient) / Diffusion distance
the SA and conc gradient need to be as ____ as possible?
BIG
the diffusion distance needs to be as ___ as possible?
SMALL
Why must exchange surfaces be moist?
Substances diffuse IN SOLUTION
How is SA maximised ?
a very large no. of alveoli
how is the conc gradient of CO2 + H2O maximised:?
by ventilation + circulation
what is the diffusion distance minimised by:?
walls of alveoli are 1 cell thick - squamous epithelial cells
what does the nasal cavity do?
warms and moistens inhaled air
what does the epigolttis do?
prevents food from entering trachea during swallowing
What does the pleural fluid do?
cause exterior of lungs and interior of ribcage to stay in contact during ventilation
what does the bronchus do?
smaller branches of the airways
what does the alveolus do?
the site of gas exchange
what does the diaphragm do?
contracts, moving down. Increases lung volume of thoracic cavity causing inhalation
what does the larynx do?
contains vocal cords - allows production of sound when exhaling
trachea?
largest airway into lungs. Cartilage prevents collapse of trachea. Lined with ciliated epithelial tissue
what does the rib do?
protection for lungs n heart, and forms rigid thoracic cavity. Also, attachment points for intercostal muscles
external intercostal muscle?
contract to move ribs up and out - causing inhalation
internal intercostal muscles?
contract pulling ribs down and in - forced exhalation
what does pulmonary surfactant do?
stops alveoli from collapsing
what is ventilation?
breathing in and out
macrophages?
‘patrol’ inner surface of alveoli, destroying pathogens
what is the capillary that runs alongside the alveloli called?
alveolar capillary
deoxygenated blood comes from ? to the alveolar capillary/
pulmonary artery
blood goes from the alveolar capillary to ?
oxygenated blood to pulmonary vein
How the O2 & CO2 conc gradient is maintained?
- O2 conc is always high in the alveoli as ventilation continuously occurs, and it is low in the blood as as the blood circulates in the capillary, the O2 is immediately removed
- CO2 conc is low in the alveoli as CO2 is being constantly breathed out, and is high in the blood as it is constantly added while the blood circulates from the heart
⭐what is ventilation ?
the physical process of moving air into the lungs - inhalation + out of the lungs - exhalation
what does ventilation rely on?
pressure gradients - between the atmosphere and thoracic cavity - space where lungs are
⭐O2 consumption ?
DRAW TRIANGLE
What can we calculate from a spirometer trace??
1 - Tidal volume (dm3) 2 - Expiratory reserve volume (dm3) 3 - Inspiratory reserve volume 4 - Vital capacity 5 - breathing rate 6 - ventilation rate 7 - rate of oxygen consumption
ventilation rate = ?
breathing rate x tidal volume
- (dm 3 min -1)
breathing rate = ?
(breaths min -1)
rate of oxygen consumption =?
(Vol of O2 consumed)/ time taken
- in (dm 3 min -1)
what is the residual volume?
- bar on top of the highest crest
- when we breathe out as much O2 as possible out, ther is still some O2 left - around 0.75dm3
➡ bc residual volume is the air left in the open airways (.e. trachea) - airways are kept open by the cartilage and it’s just impossible for a;; air to be breathed out
what do you always work out for a spirometer trace calculation?
no. of mm for 1 min
no. of mm for 1dm3
gas exchange in fish - what problems does obtaining O2 from H20 present?
- water is 1000x denser than air and water is 100x more viscous than air ➡ so it would require a of energy to move water into and out of e..g. lungs
- water is lower in O2 conc than air - 1% compared to 21%
how are the problems caused by getting O2 from water solved by fish?
- fish ventilate their gills by forcing water to flow past them in 1 direction
the circulatory system of fish?
- single
- a fish heart has only 2 chambers - one atrium and one ventricle
- there’s: gill capillaries, efferent branchial artery, system capillaries, heart
what does the efferent branchial artery do?
EFF off - go away
Efferent - away from the gill capillaries
what does the afferent branchial artery do?
carries blood towards gill capillaries
the counter current mechanism?
- blood flows from the back of the gill filaments to the front through capillaries in the lamellae
- this is the opposite direction to the way water flows across the filaments - a counter current mechanism
why use a counter current mechanism though?
- opposite direction of flow
- constant conc gradient is maintained - there is always a diff of 1
- diffusion doesn’t stop - more effective
describe the process of inspiration?
1 - external intercostal muscles contract
2 - contraction of the muscle in the diaphragm pulls the diaphragm lower - increasing the volume of the thorax
3 - increased volume causes pressure to fall in the thorax. Air flows in down a pressure gradient
relaxed expiration?
1 - elastic fibres in the spaces between alveoli are stretched
2 - diaphragm and intercostal muscles relax, elastic fibres recoil
3 - causing the volume to decrease and the pressure to increase in the thorax
4 - air flows out of the lungs
forced expiration ?
1 - contraction of the internal intercostal muscles causes the rib cage to move downwards and inwards
2 - this decreases the V of the thorax and Increases P
3 - Diaphragm relaxes
4 - contraction of the abdominal wall muscle increases pressure and raises the diaphragm
5 - decreased pressure in the thorax, air flows out of the lungs
air flows…
down pressure gradient, between atmospheric pressure and thoracic cavity
lungs - cartilage function?
- forms incomplete rings which stops the trachea from collapsing. The rings are incomplete so that the food can move easily down the oesophagus behind the trachea
lungs - ciliated epithelium function?
- the trachea and its branches are lined w a ciliated epithelium w goblet cells between and below the epithelial cells. The cilia beat and move the mucus along w any trapped dirt and microorganisms away from the lungs
lungs - goblet cells function?
- goblet cells secrete mucus onto the lining of the trachea, to trap dust and microorganisms that have escaped the nose lining
smooth muscle function?
- relaxes - dilates bronchioles
- contracts - constricts bronchioles
- the walls of bronchioles contain smooth muscle
lungs - elastic fibres function?
- in the alveoli
- made of elastin
- allow the alveoli to stretch as air is drawn in
- when they return to their resting size, they help squeeze the air out - this is known as the elastic recoil of the lungs
what is cartilage present in?
Trachea and Bronchi
NOT bronchioles and alveoli
What is ciliated epithelium present in?
trachea and bronchi
NOT bronchioles and alveoli
what are goblet cells present in?
trachea and bronchi
NOT bronchioles and alveoli
what is smooth muscle present in?
trachea, bronchi, bronchioles
NOT alveoli
what are elastic fibres present in?
Trachea, Bronchi, Bronchioles, Alveoli
explain how a spirometer works?
- person breaths in and out of the tube
- soda lime removes the CO2 (as the person will breathe the air back in again, don’t want to have a high level of CO2 back in )
- pure O2 under float
- when person breathes out, float goes up, graph is drawn
- when person breathes in, float goes down, graph is drawn
afferent bronchiole artery ?
from heart
efferent bronchiole artery?
to the body
what happens when the mouth of a fish is open?
- mouth open, operculum closed
- floor of the buckle cavity lowers
- volume increases, pressure decreases lower than the external water pressure
- water flows down pressure gradient into the mouth and fills the buckle cavity
what happens when the mouth is closed?
- mouth closes, operculum opens
- buckle cavity constricts
- volume decreases, pressure increases higher than the external water pressure
- water flows down pressure gradient out of the operculum
insects - spiracles?
- small openings that allow air to enter & leave system
- loses H2O
- can be opened and closed via spiracle sphincters
insects - tracheae?
- tubes that carry air from spiracles to the body
- lined w chitin to keep open
- impermeable to hases
insects - tracheoles ?
- branch out from the trachea - much narrower tubes
- no chitin so permeable to gases
- runs throughout tissue - gas exchange occurs here
insects - air sacs?
- sacs of extra air - can be inflated or deflated by movement of THORAX AND ABDOMEN
insects - haemolyph?
liquid inside the insects
- DOES NOT DELIVER O2
- DELIVERS PRODUCTS OF DIGESTION
How do gases move in an insect?
via diffusion - not efficient
the volume of what varies in an insect?
- tracheal fluid - vol varies according to O2 demand
tracheole function when insect is resting?
- low activity
- so low O2 demand
- smaller SA of tracheole exposed (due to higher tracheal fluid level)
- low O2 delivery to cells
tracheole function when insect is active?
- higher activity
- higher O2 demand
- lactic acid ⬆ (produced by anerobic respiration)
- water potential of cell ⬇
- fluid moves into cytoplasm via osmosis
- larger SA exposed to cell
- high O2 delivery to cell
how do large and flying insects cope w their extra demand for O2?
1 - mechanical ventilation
2 - collapsible air sacs
mechanical ventilation?
- pumps air in & out of tracheal system by abdomen contracting
- body vol & blood pressure change forcing air in and out
collapsible air sacs?
- can store extra air just inside spiracles
- inflated and deflated by movement of abdomen and thorax
what helps achieve a large SA in an insect & fish and how structures function to achieve this?
insect: tracheoles and tracheal fluid (lots of tracheoles) ➡ when O2 demand is high, fluid decreases (due to lactic acid ⬆) so SA of exchange ⬆
fish: lamella ➡ many lamellae allow lots of oxygenation of blood
what helps to achieve a short diffusion distance in an insect and fish?
insect: tracheoles ➡ thinner branches of tracheae - reduced diff dis
fish: capillaries ➡ single cell thick ➡ short diffusion distance
what helps to maintain a steep conc gradient in insect and fish?
insect: spiracles (no O2 in trachea when taking in O2) ➡ take in O2 from air so airways going from high conc to low conc
fish: capillaries that carry blood to be oxygenated, counter current system ➡ water flows opposite to the blood flow in capillaries (CCS)
(airway) increasing order?
pharnyx ➡ larynx ➡ trachea ➡ bronchus
how does surfactant prevent the alveoli from collapsing?
reducing surface tension
features of efficient exchange surfaces?
- incr SA
- thin layers = short diffusion distances
- good blood supply - maintains a steep conc gradient for diffusion
- ventilation to maintain diffusion gradient
important features of the nasal cavity?
- a large SA w a good blood supply, which warms the air to body temp
- a hairy lining - secretes mucus to trap dust and bacteria , protecting delicate lung tissue from irritation and infection
- moist surfaces - which increases the humidity of the incoming air, reducing evaporation from exchange surfaces
after passing thru the nasal cavity, the air entering the lungs is a similar temp and humidity to the air already there
lung surfactant imp?
- the inner surface of the alevoli is covered in a thin layer of solution of water, salts and lung surfactant. It is this surfactant that makes it possible for the alveoli to remain inflated. O2 dissolves in the water b4 diffusing into the blood, but water can also evaporate into the air of the alveoli
forced exhalation?
you can exhale forcible using energy. The internal inter coastal muscles contract, pulling the ribs down hard and fast, and the abdominal muscles contract forcing the diaphragm up to increase the pressure in the lungs rapidly
what is tidal volume?
the volume of air in and out of the lungs w each resting breath. It is around 500cm3 in most adults at rest, which uses about 15% of the vital capacity of the lungs
what is vital capacity?
the volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath
what is inspiratory reserve volume?
teh max volume of air you can breathe in over and above a normal inhalation
what is expiratory reserve V?
the extra amount of air you can force out of your lungs over and above the normal tidal V of air you breath out
what is residual V?
the V of air that is left in ur lungs when u have exhaled as hard as possible. This cannot be measured directly
what is total lung capacity?
the sum of the vital capacity and the residual V
the V of air drawn in and out of the lungs can be measured in a variety of diff ways:
- a peak flow meter
- a vitalograph
- spirometer
peak flow meter?
a simple device that measures the rate at which air can be expelled from he lungs. Ppl who have asthma often use these to monitor how well their lungs r working
vitalograph?
are more sophisticated versions of the peak flow meter. The patient being tested breathes out as quickly as they can thru a mouthpiece, and the instrument produced a graph of the amount of air they breathe out and how quickly it is breathed out . The V of air is called the forced expiratory V in 1 second.
Spirometer?
is commonly used to measure diff aspects of the lung V, or to investigate breathing patterns. there are many diff forms
challenges of gills (fish(?
- to allow efficient gas exchange at all times, fish need to maintain a continuous flow of water over gills, even when they r not moving
- need to carry out gas exchange as effec as possible in water, a medium where diffusion is slower than in air
extra adaptation of gills for effective gas exchange?
the tips of gill filaments overlap, this inc the resistance to the flow of water over the gill surfaces and slows down the movement of the water. As a result, there is more time for gas exchange to take place
Structure of the lungs?
Trachea -> bronchi -> bronchioles -> alveoli
Why did mammals evolve lungs ?
- Require a large amount of O2 + produce a large amount of CO2
- They are large organisms
- High metabolic rate + level of activity
- to deal w demands
The larger ________ may have cartilage but most do not?
Bronchioles
Why ciliated epithelium does not line alveoli?
Would ↑ DD
Why does not line alveoli?
Would not be cleared as no cilia on squamous epithelial cells
Why do the lungs need ventilation?
In order to maintain gas exchange in the alveoli
Intercostal muscles are types of ______ muscle?
Skeletal
Where do intercostal muscles lie?
Between the ribs
The diaphragm is a ?
Sheet of muscle that separates the thorax from the abdomen
Is dome shaped when relaxed
Inhaling is an _____ process but exhalaing is a _____ process?
Inhaling = active, requires ATP Exhaling = passive
What can we do by measuring lung function?
Assessing physical fitness + presence of certain diseases
Spirometer - lid?
- Inhaling causes the lid to drop down
- Exhaling causes lid to rise
Spirometer trace - axis?
X axis = time (s)
Y = volume of air (dm^3)
Tidal volume definition?
The volume of air moved in and out of the lungs with a normal breath
Vital Capacity definition?
The max amount of air that can be moved by the lungs in 1 breath
Residual volume definition?
The volume of air left in the lungs after a forced expiration
The downwards slope on a spirometer trace wouldn’t happen if?
CO2 wasn’t absorbed by the soda lime as it would just replace the oxygen used (6 mol: 6 mol in respiration)
O2 uptake definition?
How much O2 is taken up per unit time
Breathing rate definition?
How many breaths taken in a minute - breaths min(^-1)
Gills are only found in?
Bony fish
The gill is made up of?
A series of bony gill arches each with 2 stacks of gill filaments
Lamellae?
- Gill filaments have protruding rows of very thin lamellae
- Each lamellae consists of network of capillaries covered by a single layer of epithelial cells - thin diffusion pathway
Because gill structures are delicate?
They are protected by a nony plate called an operculum
The buccal cavity is?
The tech term for a fish’s mouth
Some insects have developed a specialised breathing mechanism e.g. grasshopper?
- As they expand their abdomen they close spiracles at the back end of their body whilst opening those at the front
- when they contract their abdomen, they open up the spiracles at their rear and close those at the front - to let CO2 out
Ventilating the tracheal system: Flight muscles?
Can alter the volume of the insect thorax to ventilate the tracheal system
Ventilating the tracheal system: air sacs?
Can be squeezed by flight muscles to push air in and out
Waxy exoskeletons don’t allow for …
Effective gas exchange
What does the tracheal system do?
Delivers O2 directly to every tissue in their body
What does the exoskeleton in an insect do?
(instead of skeleton) helps with protection and water retention
Sharks?
Some sharks don’t use the buccal pumping mechanism and so have to swim constantly to keep a fresh supply of H2O flowing over their gills
If buccal cavity and opercular vents opened at the same time?
Water could go either way, direction is imp
