Exchange Surfaces and Breathing Flashcards
What are the two main reasons as to why single celled organisms can rely on diffusion alone?
Metabolic demands are low
Surface area to volume ratio is high
What are the 4 key features of a good exchange surface?
Increased Surface Area
Thin Layers
Good Blood Supply
Ventilation to maintain diffusion gradient
What are the benefits of an increased surface area? Give examples of places with this.
Provides are for exchange and overcomes the limitations of SA:V ratio
Eg. Root Hair Cells and Villi
What are the benefits of thin layers? Give examples of places with this.
Distances substances have to diffuse is short, making process faster and more efficient
Eg. Alveoli and Villi
What are the benefits of a good blood supply ? Give examples of places with this.
Steeper the concentration gradient, faster diffusion takes place.
Eg. Alveoli, Gills and Villi
What are the benefits of good ventilation? Give examples of places with this.
For gases, helps maintain concentration gradients and make process more efficient
Eg. Alveoli and Gills
What has the Mammalian Gaseous Exchange system had to evolve to do?
Complex systems that allow for efficient gaseous exchange but minimise water loss
What are three key features of the nasal cavity and what do they do?
Large surface area with good blood supply- warms air to body temperature
Hairy lining- which secretes mucus to trap dust and bacteria protecting lungs from irritation
Moist surfaces- increase humidity preventing evaporation
What is the trachea?
Main airway carrying clean warm, moist air from the nose down the chest
What is the structure of the trachea?
Wide tube supported by incomplete rings of strong, flexible cartilage which stop the tube from collapsing
Why are tracheal rings incomplete?
To allow food to easily move down the oesophagus because that is behind the trachea
What is the trachea lined with?
Ciliated epithelium and goblet cells
What is the role of goblet cells?
To secrete mucus onto the lining of the trachea, to trap dust and microorganisms that have escaped the nose lining.
What prevents mucus entering the lungs? How?
Cilia beat mucus and microorganisms away from lungs, mostly into the throat where it is digested
What is the effect of cigarette smoke on the trachea?
Stops cilia beating
What are the bronchi?
Supporting rings of cartilage that are smaller than the trachea and branch into each lung
What is the structure of bronchioles?
No cartilage rings
Smooth muscle
How does smooth muscle link to role of bronchioles?
Smooth muscles contract- bronchioles constrict
Smooth muscle relaxes- bronchioles dilate
Affects how much oxygen reaches lungs
Can gaseous exchange occur in bronchioles?
Yes, as the are lined with a layer of flattened epithelium
What is the structure of alveoli?
Tiny air sacs made from thin, flattened epithelial cells
Contains some collagen and elastic fibres
What is elastic recoil?
Elastic tissues stretching to allow alveoli to draw in maximum amount of air, then returning to resting size to help squeeze air out.
How are alveoli adapted?
Large surface area
Thin layers- one epithelial cell thick cell walls
Good blood supply
Good ventilation - from breathing
What is the role of ‘lung surfactant’?
Allows alveoli to remain inflated
What causes ventilation to occur?
Pressure changes in the thorax
What is the pleural cavity filled with? Why?
Thin layer of lubricating fluid so the membranes slide easily over each other
Explain what happens during inspiration
Diaphragm contracts- flattening and lowering
External intercostal muscles contract
Ribs move upwards and outwards
Volume of thorax increase= pressure in thorax decreases
Lower than atmospheric pressure so air drawn in
Explain what happens during passive expiration
Diaphragm relaxes into resting dome shape
External intercostal muscles relax
Ribs move downwards and inwards
Alveoli elastic fibres return to normal length
Decreased volume of thorax
Pressure inside greater than outside, air forced out
What happens during forced expiration?
Requires energy
Internal intercostal muscles contract
Ribs pulled down hard and fast
Abdominal muscles contract forcing diaphragm up to increase pressure rapidly
What does a peak flow meter measure?
The rate at which air can be expelled from the lungs
What does a vitalograph measure?
Amount of air breathed out and how quickly (the forced expiratory volume in 1 second)
What does a spirometer measure?
Different aspects of long volume or breathing patterns
Define ‘tidal volume’
The volume of air that moves into and out of the lungs with each resting breath
Define ‘vital capacity’
Volume of air that can be exhaled when the deepest possible intake of breath is followed by the longest possible exhalation
Define ‘inspiratory reserve volume’
The maximum volume of air you can breath in over a normal exhalation
Define ‘expiratory reserve volume’
The maximum volume of air you can force out of your lungs above your tidal volume of air you breathe out
Define ‘residual volume’
The volume of air that is left in your lungs when you have exhaled as hard as possible
Define ‘total lung capacity’
The sum of the vital capacity and residual volume
What is the breathing rate?
The number of breaths taken per minute
What is the ventilation rate?
The total volume of air inhaled in one minute
Give the equation for ventilation rate
Ventilation Rate= breathing rate x tidal volume
Explain how a spirometer works
Nose clip
Subject breaths in and out until oxygen is used up
Trace drawn on revolving drum
Cannister of soda lime removes carbon dioxide
What are spiracles?
Small openings in the thorax of an insects body that allows for the movement in and out of oxygen and carbon dioxide
How do insects minimise water loss during gaseous exchange?
Spiracle sphincters remain shut as much as possible
What is the structure of trachea in an insect?
Tubes lined with chitin which keep them open if bent or pressed
Can gaseous exchange occur in the trachea of an insect?
Very little because chitin is impermeable
What is the structure of tracheoles?
Single, elongated cells which have no chitin lining which pass throughout the tissues of an insect
How does oxygen move through an insect normally?
Through the trachea into the tracheoles where oxygen dissolves into the moisture on the cell walls and then diffuses into cells
How is tracheal fluid adapted to help the insect?
Tracheal fluid normally limits the penetration of air
Lactic acid builds up when oxygen demands are high
This lowers water potential of tracheal fluid so water moves out via osmosis.
Exposes more surface area for gaseous exchange
What are two alternative methods that insects have to gain more oxygen?
Mechanical ventilation of the tracheal system
Collapsible enlarged tracheae or air sacs
What adaptations to gill lamellae have? What occurs there?
Main site of gaseous exchange in a fish
Rich blood supply and large surface area= efficient exchange
What is the structure of gill filaments and how does this help gaseous exchange occur?
Large stacks of gill filaments-gill plates
Flow of water keeps them apart showing large surface area for gaseous exchange
What is the role of a gill arch?
Supports structure of gills
What is the operculum?
The flap that covers gills
What is ram ventilation?
Relying on continual movement to ventilate the gills
Explain process of ventilation in a bony fish
Floor of buccal cavity drops Volume increases Pressure decreases Water enters Mouth closes Operculum squeezes inwards Buccal cavity floor moves upwards Volume decreases Pressure increases Water forced out over gills
What are the 3 major adaptations for successful gaseous exchange in bony fish?
Large Surface Area
Adjacent gill filaments overlap increasing resistance so more time for exchange to occur
Counter current blood flow system-allows steep concentration gradient to be maintained
Compare blood flow systems in cartilaginous and bony fish
Cartilaginous- parallel system, 50% oxygen extracted
Bony- counter current, 80% oxygen extracted
