3A - Exchange And Transport Systems Flashcards
what’s inspiration?
External intercostal muscles
contract; ribs move up and out.
- Diaphragm muscle contracts - diaphragm flattens.
Volume of thorax increases, so pressure decreases in thorax) air drawn in (as atmospheric pressure bigger than pulmonary pressure)
whats expiration?
Internal intercostal muscles
contract; ribs move down and in.
- Diaphragm muscles relax- diaphragm moves up.
Vol of thorax decreases so pressure increases.
(Pulmonary pressure is more than the atmosphere so air is
forced out)
whats pulmonary ventilation and the equation
Pulmonary ventilation -
Total volume of air moved into the lungs in one minute
Pulmonary ventilation = tidal vol x ventilation rate
Reduced Tidal volume means-
1.Less carbon dioxide exhaled/moves out (of lung)
2. (So) reduced diffusion/concentration gradient (between
blood and alveoli)
3. Less/slower movement of carbon dioxide out of blood
why do multicellular organisms need exchange organs and a mass transport system
an organism needs to supply each cell with substances like glucose and oxygen (respiration)
And must remove waste product from every cell to avoid damaging itself
- in single celled organisms, these substances can diffuse directly
in and out of cell across cell surface membrane
» diffusion rate is quick due to small distances substances travel (small SA)
in multicellular organisms, diffusion across membrane is slow bc..
- some cells are deep in the body (big distance to environment)
- large animals have low SA:V; difficult to exchange enough substances to supply a large volume of animal through a small surface
–
–> so need specialised exchange organs like lungs
–> need efficient system to carry to and from cells (mass transport)
like circulatory and
water and solutes in xylem and phloem in plants
how do body and shape affect heat exchange
metabolic activity inside cells creates heat. staying at the right constant temperature is hard..
- size
rate of heat loss from an organism depends on its surface area - if an organism has a large volume, its SA is relatively small, so harder to lose heat (and vice versa)
- so small organisms need a high metabolic rate, to generate a sufficient amt of heat to stay warm
- shape
compact shaped animals have a small SA relative to volume (minimise heat loss)
and with a less compact shape (gangly limbs, stick out) have a large SA relative to volume, increasing heat loss from surface
–> depends on environments temp
how do some organisms have behavioural and physiological adaptations to aid exchange
- animals with high SA:V lose more water wch evaporates from surface
- some small desert animals have kidney structure adaptations so produce less urine to compensate
- so support high metabolic rates, small arctic animals need to eat large amounts of high energy foods
- and have thick layers of fur or hibernate when weather gets cold
- large desert organisms find it hard to cool as heat loss is relatively slow
» elephants developed large flat ears to increase SA allowing to lose more heat
» a behavioural adaptation is that they spend much of the day in water
what two major adaptations do gas exchange surfaces have
have a large SA
and are thin (one layer of epithelial cells), providing short diffusion pathway
> organism also maintains a steep concentration gradient of gases across exchange surface
These are factors that increase diffusion rate ; single celled organism has gases diffusing in and out cell membrane
across body surface
whats a countercurrent system used for gas exchange in fish
- water containing oxygen enters fish via mouth and out through gills
- each gill is made of lots of thin plates called gill filaments
wch give large SA for gas exchange - gill filaments are covered in lots of tiny lamellae wch increase SA even more
- lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
- blood flows through lamellae in one direction and water flows in opposite direction
- called a counter current system
-
-maintains a large conc gradient between water and blood.
- conc of oxygen in water is always higher compared to blood
- so as much oxygen diffuses into blood as possible
how do insects exchange gases using trachae
insects have tiny air filled pipes called trachae wch are used for gas exchange
1. air moves into trachae through pores on surface called spiracles
- oxygen travels down conc gradient to cells
- trachae branch off into smaller trachioles wch have thin permeable walls and go to individual cells
–> meaning oxygen diffuses directly into the respiring cells ; insect circulatory systems dont transport O2 - CO2 from cells move down its own conc gradient to the spiracles to be released into atmosphere
- inects use rhythmic abdominal movements to move air in and out spiracles
how do dicotyledonous plants exchange gases at surface of mesophyll cells
- plants need CO2 for photosynthesis, wch produces O2 (waste gas) for respiration, wch also produces CO2 as a waste gas.
- main gas exchange surface is surface of mesophyll cells in the leaf ; well adapted for their function with large SA
- mesophyll cells are inside the leaf; gases move in and out through pores in epidermis called stomata
- stomata can open to allow exchange of gases , and close if plant is losing too much water
» guard cells control opening and closing of stoma
how do insects and plants control water loss
exchanging gases causes water loss
- plants and insects have evolved adaptations to minimise water loss without reducing gas exchange by lots
- when insects lose too much water , they close their spiracles with muscles
- also have waterproof waxy cuticle all over body and tiny hairs round spiracles both of which reduce evaporation - plant stomata are open in day for gas exchange - water enters guard cells to make them turgid opening stomatal pore
- if plant gets dehydrated guard cells lose water to be flaccid, closing pore
what are xerophytes and their adaptations
xerophytes are adated to dry warm and windy habitats where water loss is a problem
- stomata sunk in pits to trap moist air, reducing conc gradient of water between leaf and air
- reducing amount diffusing out leaf
- layer of hairs on epidermis to trap moist air round stomata
- curled leaves with stomata inside protecting from wind.
- windy conditions increase diffusion rate
- reduced number of stomata so fewer places for water to escape
- waxy waterproof cuticles on leaves and stems to reduce evaporation
whats the structure of the lungs
when breathing in, air enters via the trachea
wch splits into two bronchi (one bronchus)
- each bronchus branches of into smaller bronchioles
- end in air sacs called alveoli where gases are exchanged
- the ribcage, internal and external intercostal muscles and diaphragm help move air in/out
how does gas exchange happen in alveoli
each alveolus is made from a layer of thin flat cells called alveolar epithelium
- theres lots of alveoli, suggests large SA for exchanging gases
- alveoli are surrounded by a network of capillaries
-O2 diffuses out the alveoli and across alveolar epithelium and capillary endothelium (single celled linings)
- and into haemoglobin in the blood
- CO2 diffuses into alveoli from blood and is breathed out
..
oxygen moves down trachea, bronchi, etc down a pressure gradient
» once in alveoli, diffuses across alveolar then capillary epithelium
ending up in capillary itself
movement happens down a diffusion conc gradient
how are alveoli adapted for gas exchange
- a thin exchange surface (alveolar epithelium thats one cell thick means short diffusion pathway
- a large SA as large number of alveoli
- also steep conc gradient for oxygen and CO2 between alveoli and capillaries ,
increasing diffusion rate.
» constantly maintained by blood flow and ventilation
what are lung diseases affecting
they affect ventilation, breathing, and gas exchange in lungs ; how well the lungs function
-doctors carry out tests to investigate lung function
- might have to interpret results from these tests (use the four terms)
TB, fibrosis, asthma, and emphysema reduce gas exchange rate
» less oxygen reaches cells and rate of
aerobic respiration decreases
»_space; so less energy released; feel tired and weak
what are the four terms used in results for tests that investigate lung function
- tidal volume
- the volume of air in each breath (0.4-0.5dm3) - ventilation rate
- number of breaths per minute (15) - forced expiratory volume (FEV)
- max volume of air that can be breathed out in a second - forced vital capacity (FVC)
- max vol of air its possible to breathe out forcefully after deep breath in
..
can figure out tidal vol, ventilation rate, etc with a spirometer (measures vol of air breathed in and out)
how does pulmonary TB affect breathing
- when one’s infected with tuberculosis bacteria
immune cells build a wall round bacteria in lungs
» forms small hard lumps = tubercles - infected tissue in tubercles dies and gaseous exchange surface is damaged(tidal vol decreased)
> can cause fibrosis wch decreases tidal vol further
3.reduced tidal vol mean less air inhaled in each breath; must breathe faster to get more air
» ventilation rate increases
symptoms are persistent cough, cough up blood/mucus, chest pains, shortness of breath, fatigue
whats fibrosis? how does it affect lung function
- fibrosis is the formation of scar tissue in lungs (result of infection/exposure to asbestos, dust)
- scar tissue is thicker and more elastic than regular - so lungs are less able to expand/cant hold as much air, reducing tidal vol and FVC
> so faster ventilation rate to get enough air to oxygenate blood enough - reduction in gaseous exchange rate; diffusion slower across thicker membrane
symptoms are shortness of breath, dry cough, chest pain, fatigue weakness
whats asthma and how can it affect breathing
- respiratory condition where airways are inflamed and irritated
- causes vary from allergy to pollen or dust - in asthma attacks, smooth muscle lining bronchioles contracts
and a large amount of mucus is produced - causes constriction of the airways , hard to breathe.
air flow in and out is severely reduced so less oxygen enters alveoli then into blood
» FEV is reduced due to reduced air flow
symptoms include wheezing, tight chest and shortness of breath,
- in attack, symptoms come in suddenly(relieved) by drugs, inhalers, wch cause bronchioles muscles to relax
emphysema
- caused by smoking or long term exposure to air pollution (foreign particles from smoke or air get trapped in alveoli)
- causing inflammation, attracting phagocytes, wch produce enzymes that break down elastin (protein in wall of alveloli)
- elastin is elastic , helps alveoli return to normal shape after inhaling/exhaling air
> no elastin means alveoli cant recoil to expel air (traps) - leading to alveoli wall destruction, reducing SA
» gaseous exchange rate decreases, so ventilation rate increases to make up
symptoms are shortness of breath and wheezing
how are lungs dissected to show main structure
wear lab coat, enusre dissecting tools (scalpel, scissors) are clean and sharp and free of rust
- lay lungs on cutting board - can see trachea and two bronchi
- attach rubber tubing to trachea and pump air into lungs using a foot pump
- will deflate by themselves due to elastin in alveoli - trachea is supported by c shaped rings of cartilage
cartilage is tough; cut lengthways to open it up - continue down one bronchi
- cut off a piece of lung (spongy due to air trapped inside alveoli
wash hands and clean table after as can cause food poisoning
how to dissect gills in bony fish
wear lab coat
1.put fish on cutting board or dissection tray
2. gills are on either side of fish head - protected on each side by bony flap called operculum , supported by gill arches
- to remove gills push back onto operculum ; use scissors to remove gills
- cut each gill arch through bone on top and bottom
can see gill filaments if look closely
how to dissect gaseous exchange system in insects
- fix insect to board with pins
- cut and remove piece of exoskeleton from along abdomen
to examine trachae - use syringe to fill abdomen with saline solution; shd be able to see network of thin, silvery tubes (trachae)
silver as filled with air - can examine trachae with optical microscope (rings of chitin on trachae walls to support)
