exchange and transport/in animals

why do multicellular organisms require specialised exchange surfaces?

they have a smaller surface area to volume ratio, meaning there is a larger distance that substances need to cross to enter the cells in an organism.

name three features of an efficient gas exchange surface?

• large surface area

• short diffusion distance

• steep concentration gradient/good blood supply

describe the trachea and its role in gaseous exchange system?

• wide tube supported by C-shaped cartilage to keep air passage open during pressure changes.

• lined by ciliated epithelium cells (containing goblet cells) which move mucus towards the throat to be swallowed, preventing lunch infections.

• carries air to the bronchi

describe the bronchi and their role in the gaseous exchange system?

• supported by rings of cartilage and are lined by ciliated epithelium cells and goblet cells.

• they are narrower and their are two of them (one for each lung).

• allows passage of air into the bronchioles.

describe the bronchioles and their function in the gaseous exchange system?

• narrower than bronchi.

• do not need keeping open by cartilage therefore have smooth muscle and elastic fibres.

• allows passage of air into the alveoli.

describe the alveoli and their function in the gaseous exchange system?

• mini air sacs, lined with epithelium cells, site of gas exchange.

• walls are only one cell thick, covered with a network of capillaries which facilitates gaseous exchange.

explain the process of inspiration and the changes that occur throughout the thorax?

• external intercostal and diaphragm muscles contract.

• this causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thorax.

• lung pressure decreases.

• this causes air flow into the lungs.

• inspiration is an active process - requires energy.

explain the process of expiration and the changes that occur throughout the thorax?

• external intercostal muscles relax.

• ribcage moves downwards and inwards and the diaphragm becomes curved again.

• volume of thorax decreases, causing air pressure to increase.

• air is forced out of the lungs.

• normal expiration is a passive process - doesn’t require energy.

• during forced expiration the internal intercostal muscles contract, the pull the ribcage down and in.

explain how a spirometer works?

used to measure lung volume. a person breathes into an airtight chamber which leaves a trace on a graph which shows the volume of breaths.

define vital capacity?

the maximum volume of air that can be breathed in or out.

define tidal volume?

the volume of air we breathe in and out in each breath at rest.

define breathing rate?

the number of breaths we take per minute.

explain the process of gas exchange in fish?

• when a fish opens it’s mouth, floor of buccal cavity is lowered so volume is increased to enable water to flow in, pressure inside cavity is decreased.

• when the fish closes it’s mouth, floor of buccal cavity is raised and the volume inside the cavity is decreased, and the pressure is raised again.

• water is pumped over the lamellae and oxygen diffuses into the bloodstream.

• waste carbon dioxide diffuses into the water and flows back out of the operculum and the gills.

how does the counter current exchange system maximise oxygen absorbed by the fish?

maintains a steep concentration gradient, as water with a high oxygen conc, is always next to blood with a low oxygen conc.

describe the structure of gills?

• each gill is made up of lot’s of thin plates called gill filaments or primary lamellae which give a big surface area for exchange of gases.

• the gill filaments are covered in lot’s of tiny structures called gill plates or secondary lamellae.

• the gill plates have lot’s of blood capillaries and a thin surface layer of cells to speed up diffusion.

• each gill is supported by a gill arch.

name and describe the three main features of an insects gas transport system

spiracles - holes on the body’s surface which may be opened or closed by a valve for gas or water exchange.

tracheae - large tubes extending through all body tissues, supported by rings to prevent collapse.

tracheoles - smaller branches dividing of the tracheae.

explain the process of gas exchange in insects?

• gases move in and out of the tracheae through the spiracles.

• oxygen travels down the concentration gradient to diffuse into the body tissue whilst waste CO2 diffuses out.

• tracheae divide into smaller branches called tracheoles which have thin permeable walls that go to individual cells.

what is an open and closed circulatory system?

open - blood can diffuse out of vessel e.g. insects

closed - blood is confined to vessels e.g. fish, mammals

what is a single and double circulatory system?

single - blood passes through the heart once for one complete circuit of the body.

double - blood passes through the heart twice for one complete circuit of the body.

relate the structure of arteries to their function?

• thick muscular walls, to handle high pressure without tearing.

• elastic tissue, allows recoil to prevent pressure surges.

• narrow lumen to maintain pressure.

relate the structure of veins to their function?

• thin walls due to lower pressure.

• require valves to ensure that blood doesn’t flow backwards.

• have less muscular and elastic tissue as they don’t have to control blood flow.

relate the structure of capillaries to their function?

• walls only one cell thick; short diffusion pathway.

• very narrow, so can permeate tissues and effective for delivering O2 to tissues.

• numerous and highly branched, providing a large surface area.

relate the structure of arterioles and venules to their function?

• branch off arteries and veins in order to feed blood into the capillaries.

• smaller than arteries and veins so that the change in pressure is more gradual as blood passes through increasingly small vessels.

what is tissue fluid?

a watery substance containing oxygen, glucose, amino acids and other nutrients. it supplies these to the cells whilst also removing any waste materials.

what types of pressure influences formation of tissue fluid?

hydrostatic pressure - higher at arterial end of capillary than venous end.

oncotic pressure - changing water potential of the capillaries as water moves out, induced by proteins in the plasma.

how is tissue fluid formed?

as blood is pumped through increasingly small vessels, hydrostatic pressure is greater than oncotic pressure, so fluid moves out of the capillaries. it then exchanges substances with the cells.

describe what happens during cardiac diastole?

atrial diastole - the atria relax and fill with blood.

ventricular diastole - the ventricles relax and blood flows through the atria-ventricular valves into the ventricles.

describe the role of the pulmonary artery and vein?

• deoxygenated blood flows from the heart to the lungs, via the pulmonary artery.

• oxygenated blood flows from the lungs to the heart via the pulmonary vein.

describe the role of the aorta and vena cava?

• oxygenated blood flows from the heart and around the body via the aorta.

• oxygen dissociates from the blood at respiring cells in the body and the blood becomes deoxygenated.

• deoxygenated blood flows from the body and back to the heart via the vena cava.

describe the role of the renal artery an vein?

• oxygenated blood flows out of the aorta, to the kidneys

• oxygenated blood enters the kidneys through the renal artery

• oxygen diffuses out of the blood to be used in the kidney cells and the blood become deoxygenated

• deoxygenated blood flows out of the kidneys via the renal vein.

how can you calculate cardiac output?

cardiac output = heart rate x stroke volume

what does myogenic mean?

the hearts contraction is initiated from within the muscle itself rather than a nerve impulse.

explain how the heart contracts?

• the sino-atrial node initiates and transmits the impulse across the atria walls, causing them to contract

• the atrioventricular node, delays and then transmits the impulse down the bundle of his

• the impulse travels into the purkinje fibres which branch across the ventricles, causing them to contract

what is an electrocardiogram (ECG)

a graph showing the amount of electrical activity in the heart during the cardiac cycle.

describe types of abnormality which may be seen in an ECG?

• tachycardia - fast heartbeat (over 160bpm)

• bradycardia - slow heartbeat (below 60bpm)

• fibrillation - irregular, fast heartbeat

• ectopic - early or extra heartbeats

describe the role of haemoglobin?

• present in RBC’s.

• oxygen molecules bind to the haem groups and are carried around the body, then released where they are needed in respiring tissues.

how does partial pressure of oxygen affect oxygen-haemoglobin binding?

as partial pressure of oxygen increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. when partial pressure is low, oxygen is released from haemoglobin.

what do oxyhemoglobin dissociation curves show?

saturation of haemoglobin with oxygen, plotted against partial pressure of oxygen. curves further to the left show that haemoglobin has a higher affinity for oxygen.

describe the bohr effect

as the pp of CO2 increases, the conditions become acidic causing haemoglobin to change shape. the affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin.

explain the role of carbonic anhydrase in the bohr effect

• present in RBC’s

• coverts CO2 to carbonic acid, which dissociates to produce H+ ions

• these combine with the haemoglobin for form haemoglobinic acid

• encourages oxygen to dissociate from haemoglobin

explain the role of bicarbonate ions in gas exchange

• produced alongside carbonic acid

• 70% of CO2 is carried in this form

• in the lungs, bicarbonate ions are converted back into CO2 which we breathe out

describe the chloride shift

the intake of chloride ions across a red blood cell membrane. this re polarises the cell after bicarbonate ions have diffused out.

how does foetal haemoglobin differ from adult haemoglobin?

• the pp of oxygen is low by the time it reaches the foetus, therefore foetal haemoglobin has a higher affinity for oxygen than adult.

• allows both mothers and child’s oxygen needs to be met.