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A-level Aqa Biology > (3) exchanging substances > Flashcards

(3) exchanging substances Flashcards

1
Q

what are examples of things that organisms need to exchange with the environment?
(what processes are required)

A
  • respiratory gases (O2, CO2)
  • nutrients (glucose, fatty acids, amino acids, vitamins, minerals)
  • excretory products (urea, CO2)
  • heat

except heat, these take place by active transport, diffusion or osmosis

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2
Q

as organisms become larger what happens to the diffusion rate?

A

their volume increases faster than their surface area therefore diffusion slows and becomes inefficient

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3
Q

what are the features of specialised exchange surfaces?

A
  • large SA which increases the rate of exchange
  • very thin membrane, diffusion distance is shorter and materials can cross the exchange surface rapidly
  • selectively permeable to allow selected material to cross
  • movement of exchange medium e.g blood to maintain a concentration gradient
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4
Q

what adaptations do insects have to prevent water loss in their bodies?

A
  • small SA:V to minimise the area over which water is lost
  • have a waterproof covering (rigid exoskeleton [made of chitin] with a cuticle to prevent water loss through evaporation)
  • spiracles (small holes on sides of insect’s body) to allow efficient gas exchange
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5
Q

how does the spiracle mechanism work in insects?

A

the spiracles are opened and closed by a valve
when open, water vapour can evaporate from the insects so they are mainly closed to prevent water loss
periodically they open to allow gas exchange

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6
Q

how do respiratory gases move in and out of an insects tracheal system along a diffusion gradient?

A

when cells are respiring, oxygen is used up and so its concentration towards the ends of the tracheoles falls, creating a diffusion gradient
-> causes gaseous oxygen to diffuse from atmosphere along tracheae and tracheoles to cells

CO2 is produced by cells by respiration: creating a diffusion gradient is the opposite direction
-> causes gaseous CO2 to diffusion along tracheoles and tracheae from cells to atmosphere

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7
Q

how do respiratory gases move in and out of an insects tracheal system by mass transport?

A

the contraction of muscles can squeeze the trachea enabling mass movements of air in and out which further speeds up the exchange of respiratory gases

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8
Q

how do respiratory gases move in and out of an insects tracheal system because of the ends of the tracheoles are filled with water?

A

muscles cells around tracheoles respire and carry out anaerobic respiration, producing lactate (soluble and lowers ψ of the muscle cells)
-> water moves into the cells from the tracheoles by osmosis and the water in the ends of the tracheoles decrease in volume and also draws more air into them.
meaning the final diffusion in the pathway is a gas instead of a liquid so it is more rapid (but also increases water evaporation)

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9
Q

what is the structure of the gills in fish and where are they located?
what is the structure of the lamellae?

A

located behind the head of the fish and alos possess several gills between their mouth cavity and the operculum (chamber at sides of mouth)

ecah gill made of GILL FILAMENTS which are stacked in a pile
each filament is covered in lamellae (containing blood capillaries and have thin flattened cells to shorten the diffusion pathway between water and blood

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10
Q

how does a countercurrent flow system enable a fish to gain as much a oxygen as possible from water?

A

the blood and water flow over the gill lamellae in opposite directions which means
the oxygenated blood meets water w its maximum concentration of oxygen so diffusion
the deoxygenated blood meets water with very little O2 so diffusion of oxygen from water to blood takes place

SO THE DIFFUSION GRADIENT FOR OXYGEN UPTAKE IS MAINTAINED ACROSS THE ENTIRE WIDTH OF THE GILL LAMELLAE

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11
Q

what would happen is the water and blood flowed in the same direction across the gill lamellae?

A

diffusion gradient would only be maintained across part of the gill lamellae and less gas exchange would take place
it would reach equillibrium and diffusion would not take place

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12
Q

what is the function of the leaves?

A
  • trap energy for photosynthesis
  • exchange of gases required for photosynthesis and respiration
  • producing glucose from photosynthesis
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13
Q

how does the volumes and types of gas being exchanged by a plant leaf change depending on the rates of photosynthesis and respiration?

A
  • when photosynthesis takes place, most CO2 is obtained from external air (although some comes from the respiration of cells)
    and in the same way some oxygen from photosynthesis is used in respiration but most diffuses out of the plant

-when photosynthesis is not occurring, oxygen diffuses into the leaf because it is being used by cells during respiration
in the same way CO2 produced during respiration diffuses out

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14
Q

how is gas exchange in plants similar to that of insects?

A
  • no living cell is far from external air, therefore there is a source of O2 and CO2
  • diffusion takes place in the gas phase which makes it more rapid than if it were in water
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15
Q

what are the adaptations of leaves that enable rapid diffusion?

A
  • large surface area of mesophyll cells for rapid diffusion
  • numerous interconnecting air spaces that occur throughout the mesophyll so gases can readily come into contact with mesophyll cells
  • many small pores (stomata) and no cell is far from a stoma so the diffusion pathway is short
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16
Q

what are the adaptations of the leaves for photosynthesis?

A

wide: helps catch more light energy
thin: helps get CO2 from bottom to tip f leaf for photosynthesis
stomata:opened and closed by guard cells
when open, allows gas exchange (Co2 in O2 out) and transpiration (H2O out of leaf)

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17
Q

what are xerophytes?

A

plants that have adapted to living where there is a short water supply

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18
Q

how does having a thick cuticle help a xerophyte survive?

A

the waxy cuticle forms a waterproof barrier and the thicker the cuticle the less water can escape

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19
Q

how does the rolling up of leaves help a xerophyte survive?

A

it protects the lower epidermis and helps trap a region of still air within the rolled leave which becomes saturated with water vapour and has a high ψ
(no ψ gradient between the inside and outside of the leaf therefore no water loss)

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20
Q

how does having hairy leaves help a xerophyte survive?

A

a thick layer of hairs traps still moist air next to the leaf surface
the ψ gradient between the outside and inside of the leaves is reduced so less water is lost by evaporation

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21
Q

how does having stomata in pits or grooves help a xerophyte?

A

these trap still, moist next to the leaf and reduce the ψ gradient

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22
Q

why is the volume of O2 to be absorbed and CO2 removed is large in mammals?

A
  • relatively large organisms with a large volume of living cells
  • they maintain a high body temperature meaning they have high metabolic and respiratory rates

as a result mammals evolve specialised surfaces called lungs

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23
Q

why are the lungs located inside the body?

A
  • air is not dense enough to support the delicate structures
  • the body would lose a great deal of water and dry out
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24
Q

what are the main parts in the human gas exchange system?

A

lungs
trachea
bronchi
bronchioles
alveoli

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25
Q

what are the lungs?

A

pair of lobed structures made of bronchioles and end in alveoli

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26
Q

what is the trachea?
and what are its adaptations?

A

flexible airway that is supported by rings of cartilage (prevents trachea from collapsing as the air pressure falls when breathing in)
the tracheal walls are made up of muscle lined with ciliated epithelium and goblet cells (produces mucus + protects and lubricates the surface)

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27
Q

what are the bronchi and what are its adaptations?

A

two divisions of the trachea (each leading to one lung)
have goblet cells to produce mucus and cilia to move dirt-laden mucus towards the throat
larger bronchi supported by cartilage

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28
Q

what are the bronchioles and what are their adaptations?

A

series of branching subdivisions of the bronchi
walls made of muscle lined with epithelial cells
muscle allows them to constrict so they can control the flow of air in n out of alveoli

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29
Q

what are the alveoli and what are their adaptations?

A

epithelium lined minute air-sacs at the end of the bronchioles
collagen and elastic fibres between the alveoli
elastic fibres allow alveoli to stretch as they fill with air when breathing in
spring back during breathing out of expel the CO@ rich air
alveolar membrane = gas exchange surface

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30
Q

what is ventilation?

A

(breathing) when the air is constantly moved in and out of the lungs to maintain diffusion of gases across the alveolar epithelium

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31
Q

what is inspiration?

A

(inhalation)
when the air pressure of the atmosphere is greater than air pressure in the lungs, air is forced into the lungs

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32
Q

what is expiration?

A

(exhalation)
when the air pressure of the lungs is greater than air pressure in the atmosphere, air is forced out of the lungs

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33
Q

what 3 muscles bring about the pressure changes within the lungs?

A

diaphragm (sheet of muscle that separates the thorax from the abdomen)
internal intercostal muscles (contraction leads to expiration)
external intercostal muscles (contraction leads to inspiration)

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34
Q

what happens during inspiration?

A

active process (uses energy)
- external intercostal muscles contract, while the internal IM relax
- ribs are pulled upwards and outwards, increasing the volume of the thorax
- diaphragm muscles contract, causing it to flatten (also increases volume of the thorax)
-increased volume of thorax results in reduction of pressure in the lungs
-atmospheric pressure is now greater than pulmonary pressure and air is forced into the lungs

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35
Q

what happens during expiration?

A

passive process (doesn’t require energy)
- internal intercostal muscles contact while external IM relax
- ribs move downwards and inwards, decreasing the volume of the thorax
- diaphragm muscles relax and is pushed up (volume of thorax is further decreased)
- decreased volume of thorax increases the pressure in the lungs
- pulmonary pressure is now greater than that of the atmosphere so air is forced out of the lungs

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36
Q

how does gas exchange take place in the alveoli?

A

Oxygen in the alveoli diffuses into the bloodstream and carbon dioxide in the bloodstream diffuses into the alveoli

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37
Q

what are the adaptations of the alveoli to ensure rapid diffusion?

A
  • red blood cells are slowed as they pass through pulmonary capillaries, allowing more time for diffusion
  • distance between the alveolar air and red blood cells is reduced (red blood cells are flattened against capillary walls)
  • walls of alveoli n capillaries = v thing, short diffusion distance
  • blood flow through pulmonary capillaries maintain a concentration gradient
  • breathing movements ventilate lungs and heart circulates blood around alveoli maintains steep concentration gradient
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38
Q

what factors can affect the lungs having unobstructed airways, a large surface area and short diffusion pathways?

A

pathogens
smoking
pollution
asthma

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39
Q

how does tuberculosis affect breathing?

A

caused by mycobacterium tuberculoses bacteria, causing infection in the lungs
- bacteria damages epithelium (surface tissues) of alveoli
- lesion forms, reducing SA of alveoli
- scar tissue form, reducing flexibility of bronchioles and alveoli
- passed on though coughing, sneezing which sreads to blood and into lungs

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40
Q

how does smoking affect breathing?

A

cigarette contains dangerous chemicals:
- tar coats inside of alveoli n prevents efficient gas exchange
-> in response, the epithelial mucus-secreting cells proliferate and membrane thickens, lungs become filled w mucus preventing gas exchange
- cilia in trachea stops moving (lungs filled w mucus)

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41
Q

how does asthma affect breathing?

A
  • airways narrow and swell and produce extra mucus which causes infection in lungs
  • inflammation may further reduce the diameter of airways
  • triggered by air-born pollutants or allergens
  • smooth muscle cells in bronchi and bronchioles contract to reduce the cross-sectioned area of airways
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42
Q

what is tidal volume?

A

vol of air breathed in/out during quiet breathing at rest

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43
Q

how is pulmonary ventilation rate worked out?

A

PVR (dm^3min^-1) = tidal vol (dm^3) x breathing rate (min^-1)

44
Q

what is expiratory reserve volume?

A

max vol of air which can be forcibly expired after a tidal expiration

45
Q

what is inspiratory reserve volume?

A

vol of air which can be inspired over and above tidal volume

46
Q

what is residual volume?

A

air which remains in the lungs even after forced expiration

47
Q

how is vital capacity worked out?

A

inspiratory reserve vol + tidal vol + expiratory reserve vol

48
Q

what are the 2 types of of digestion?

A

physical breakdown
chemical digestion

49
Q

what is physical breakdown?

A
  • food = too large, broken down into smaller pieces by structures such as teeth (makes it possible to ingest food + provides large SA for chemical digestion)
  • food also churned up by muscles in the stomach wall and this also physically breaks it up
50
Q

what is chemical digestion?

A
  • hydrolyses large insoluble molecules into smaller soluble ones (carried out by enzymes which function by hydrolysis)
  • one enzyme hydrolyses large molecule into smaller scetions which are hydrolysed by additional enzymes
51
Q

what are the 3 important digestive enzymes?

A

CARBOHYDRASES: hydrolyses carbs into monosaccharides
LIPASES: hydrolyses lipids into glycerol and fatty acids
PROTEASES: hydrolyses proteins into amino acids

52
Q

what organs are involved in digestion?

A

mouth
esophagus
stomach
small intestine
large intestine
rectum

53
Q

what is the role of the mouth during digestion?

A
  • macerate’s food into smaller pieces by chewing
    (increases surface area of food to speed up rate of digestion)
  • glands in the mouth secrete saliva (lubricates food + provides SALIVARY AMYLASE)
54
Q

what is the role of the oesophagus during digestion?

A
  • when food = swallowed, travels down muscular tube (helps BOLUS descend to the stomach by PERISTALSIS)
  • bolus passed through CARDIAC SPHINCTER (prevents the backflow of stomach content)
55
Q

what is the role of the stomach during digestion?

A
  • muscle contractions of stomach walls help churn food (helps breaking food up further by mechanical digestion)
56
Q

what substances are secreted by the stomach during digestion and what are their roles?

A

PEPSIN: protease enzyme
HCL: for antimicrobial effect
MUCUS: to shield stomach lining from HCL

57
Q

what is the role of the small intestine during digestion?

A
  • break down food + absorb nutrients
  • chyme (liquid food) leaves stomach though the pyloric sphincter and enters the duodenum
    (mixes chyme, bile and pancreatic juices)
58
Q

what is the role of the liver in digestion?

A
  • secretes bile into the duodenum
    (bile derived from bron red blood cells - gives faeces brown colour)
    (bile helps by
    neutralising the acidic chyme
    emulsifying fats)
59
Q

what is the role of the pancreas during digestion?

A

secretes pancreatic juice (includes enzymes e.g amylase n trypsin)

60
Q

what is the role of the large intestine in digestion?

A
  • provides the reabsorption from the digestive tract
    -absorbs all minerals/vitamins/nutrients that were previously unable to be absorbed (e.g nutrients released through the action of gut bacteria)
61
Q

what is the process of the rectum in digestion?

A

faeces stored here until periodically removed via anus by process of egestion

62
Q

how are carbohydrates digested?

A
  • saliva enters mouth by salivary glands which contains salivary amylase (hydrolyses glycosidic bonds of the starch molecule to produce disaccharide maltose)
  • food swallowed and enters the stomach, where acid denatures the amylase and prevents further hydrolysis of starch
  • food passed into small intestine and mixes w pancreatic juice ( contains pancreatic amylase, which continues the hydrolysis of remaining starch to maltose)
  • muscles in intestine push food along ileum and the epithelial lining produces disaccharides maltase (dissacharidase hydrolyses the maltose into a-glucose
63
Q

how are the disaccharides sucrose and lactose hydrolysed by disaccharidases?

A
  • sucrase hydrolyses single glycosidic bond in the sucrose molecule and produces glucose and fructose
  • lactase hydrolyses single glycosidic bond in lactose molecule which produces the two monosaccharides glucose and galactose
64
Q

how are lipids digested?

A

lipids hydrolysed by enzymes lipases (produced in pancreas that hydrolyse the ester bond in the tryglycerides to form fatty acids n monoglycerides)

emulsification: lipids split into micelles by bile salts (produced by liver)
increases surface area of lipids so action of lipases is sped up

65
Q

how are proteins digested?

A

hydrolysed by peptidases

66
Q

what are 3 peptidases and what are their roles?

A

ENDOPEPTIDASES: hydrolyse peptide bonds between amino acids in central region of a protein molecule forming series of peptide molecules

EXOPEPTIDASES: hydrolyses the peptide bonds on the terminal amino acids of peptide molecules (formed by endopeptidases)
progressively releases dipeptides and single amino acids

DIPEPTIDASES:
hydrolyse the bonds between 2 amino acids of a dipeptide
(membrane bound: part of the cell-surface membrane of the epithelial cells lining the ileum)

67
Q

what is the ileum?

A

main site of molecule absorption in digestion

68
Q

what are the adaptations of the ileum that maximise the rate of digestion?

A
  • villi
    fingerlike projections of the epithelium which increases surface area
  • microvilli
    massively increases surface area

-strong bloody supply as villi contains blood vessels maintaining a concentration gradient

-thin walls of intestinal epithelium: minimises diffusion distance

69
Q

how are triglycerides absorbed?

A

micelles associated with bile salts come into contact with epithelial cells lining the villi of the ileum
micelles break down, releasing monoglycerides and fatty acids (non-polar molecules therefore easily diffuse across cell membrane into epithelial cells)

inside epithelial cells, They are transported to the ER where they are recombined to form triglycerides
continuing in Golgi: associate with cholesterol and lipoproteins to form chylomicorns ( move out of epithelial cells by exocytosis

70
Q

what are the 2 chambers for the 2 pumps of the heart?

A

atrium: thin walled, stretches as collects blood

ventricle: thicker muscular wall, contracts strongly to pump blood

71
Q

why does the heart have 2 separate pumps?

A

blood has to pass through tiny capillaries in lungs (presents large SA for exchange of gases) where there is a large drop in pressure therefore blood flow to rest of the body would be v slow

mammals therefore have a system in which the blood is returned to the heart to increase its pressure before being distributed to the rest of the body

72
Q

where does the right ventricle pump blood to?

A

only to the lungs
(has a thinner muscular wall than the left ventricle)

73
Q

where does the left ventricle pump to?

A

the rest of the body
(has thick muscular wall to enable to create enough pressure to pump blood to the rest of the body)

74
Q

what are the 2 valves that prevent the backflow of blood into the atria when the ventricles contract?

A

bicuspid valve
tricuspid valve

75
Q

what are the pulmonary vessels connected to the 4 chambers of the heart?

A

aorta
vena cava
pulmonary artery
pulmonary vein

76
Q

what is the aorta connected to?
what type of blood does it carry, and to where?

A

connected to the left ventricle
carries OXYGENATED blood TO ALL parts of the body EXCEPT LUNGS

77
Q

what is the vena cava connected to?
what type of blood does it carry, and to where?

A

connected to right atrium
brings DEOXYGENATED blood back FROM the tissues of the body (except lungs)

78
Q

what is the pulmonary artery connected to?
what type of blood does it carry, and to where?

A

connected to the right ventricle
carried DEOXYGENATED blood TO the LUNGS (O2 is replenished CO2 is removed)

79
Q

what is the pulmonary vein connected to?
what type of blood does it carry, and to where?

A

connected to the left atrium
brings OXYGENATED blood back FROM the lungs

80
Q

how is the heart muscle supplied w oxygen?

A

supplied by its own blood vessels CORONARY ARTERIES

81
Q

what happens when there is a blockage of the coronary arteries?

A

leads to myocardial infection / heart attack
bc heart muscle is deprived of blood and therefore oxygen, muscle cells in this region are unable to respire aerobically and die

82
Q

what are the 2 phases of the cardiac cycle?

A

systole: contraction
diastole : relaxation

83
Q

what happens during the relaxation of the heart (diastole)?

A

blood returns to the atria through pulmonary vein (from lungs) n vena cava from body
atria fills, pressure rises : when pressure exceeds that in ventricles, atrioventricular valves open up allowing blood to pass into ventricles (aided by gravity + muscular walls of atria and ventricles are relaxed)

relaxation of ventricle walls causes them to RECOIL and reduces pressure within ventricle: causes pressure to be lower than that in aorta and pulmonary artery, semi-lunar valves in aorta n pulmonary artery close

84
Q

what are the 2 stages of the contraction of the heart (systole)

A

atrial systole: contraction of the atria
ventricular systole: contraction of the ventricles

85
Q

what happens during the atrial systole?

A

contraction of atrial walls + recoil of relaxed ventricle walls forces remaining blood into ventricles from the atria (muscle of the ventricle walls remain relaxed)

86
Q

what happens during the ventricular systole?

A

walls contract simultaneously (after short delay to allow ventricles to fill w blood) –> increases blood pressure within them, forcing shut the atrioventricular valves + preventing back flow of blood into atria

pressure in ventricles rises, once exceeds that in aorta and pulmonary artery, blood forced from ventricles into vessels how do

87
Q

how do valves control blood flow?

A

valves open when the diff in blood pressure either side favours the movement of blood in required direction
when bloods tends to flow in the opposite direction to that which is desirable, valves close

88
Q

what are the 3 types of valves?

A

atrioventricular vs
semi-lunar vs
pocket vs

89
Q

where are the atrioventricular valves located?
how do they prevent backflow of blood?

A

between L atrium n ventricle / R atrium n ventricle

prevents blood flow BACK TO ATRIA when contraction of ventricle pressure exceeds atrial pressure: close of valves ensures when vs contract, blood within them moves to aorta n pulmonary artery than back to ATRIA

90
Q

where are the semi-lunar valves located?
how do they prevent backflow of blood?

A

aorta n pulmonary artery

prevents backflow of blood into the VENTRICLES when pressure in vessels exceeds that in ventricles
arises when elastic walls of vessels recoil increasing pressure within them and when ventricle walls relax reducing pressure within the ventricles

91
Q

where are the pocket valves located?
how do they prevent backflow of blood?

A

in veins
ensures when veins are squeezed blood flows back TOWARDS HEART than away from it

92
Q

how do the valves open and close?

A

made up of cusp-shaped flexible fibrous tissue
when pressure is greater on the convex side of cusps, they move apart to let blood pass between the cusps

when pressure is greater on the concave side, blood collects within the bowl of the cusps: pushes them together to form a tight fit and prevents the passage of blood

93
Q

how to work out cardiac output?

A

cardiac output = heart rate x stroke volume

94
Q

what are the different type of blood vessels and where do they carry blood?

A

arteries: carry blood AWAY from HEART AND INTO ARTERIOLES

arterioles: (smaller arteries) control blood flow from ARTERIES to CAPILLARIES

capillaries: (tiny vessels) link ARTERIOLES to VEINS

veins: carry blood FROM CAPILLARIES back to the HEART

95
Q

what are the basic layered structure for arteries, arterioles and veins from the OUTWARDS INWARDS and their roles?

A

TOUGH FIBROUS OUTER LAYER: resists pressure changes from within n outside

MUSCLE LAYER : contracts and controls flow of blood

ELASTIC LAYER: helps to maintain blood pressure by stretching and springing back (recoiling)

ENDOTHELIUM: (thin inner lining) smooth to reduce friction and thin to allow diffusion

LUMEN: central cavity of the blood vessel through which the blood flows

96
Q

what is function of the arteries?

A

to transport blood rapidly under HIGH PRESSURE from the HEART to the TISSUES

97
Q

artery structure: why is the muscle layer thick compared to veins?

A

means smaller arteries can be constricted and dilated in order to control the volume of blood passing though them

98
Q

artery structure: why is the elastic layer thick compared to veins?

A

important that blood pressure is kept high in arteries to reach the extremities of body
elastic wall stretched at systole and springs back at diastole
stretching and recoil helps to maintain high pressure and smooth pressure surges creating by the beating of the heart

99
Q

artery structure: why is the overall thickness great?

A

resists vessel bursting under pressure

100
Q

artery structure: why are there no valves?

A

blood is under high pressure due to heart pumping blood into arteries therefore blood does not tend to flow backwards

101
Q

what is the function of the arteriole?

A

carry blood under low pressure than arteries from ARTERIES to CAPILLARIES
control flow of blood between the 2

102
Q

arteriole structure: why is the muscle layer thicker than arteries?

A

the contraction of muscle layer allows constriction of the lumen of the arteriole -> restricts flow of blood and controls its movement into the capillaries that supply tissues w blood

103
Q

artery structure: why is the elastic layer thinner than arteries?

A

bc blood pressure is lower

104
Q

what is the function of the veins?

A

0transports blood slowly under low pressure

105
Q
A

A-level Aqa Biology (7 decks)

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