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Biology A Level > Topic 3 > Flashcards

Topic 3 Flashcards

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1
Q

Surface area to volume ratio

A

The surface area of an organism divided by its volume
the larger the organism, the smaller the ratio

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2
Q

Factors affecting gas exchange

A

diffusion distance
surface area
concentration gradient
temperature

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3
Q

Ventilation

A

Inhaling and exhaling in humans
controlled by diaphragm and antagonistic interaction of internal and external intercostal muscles

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4
Q

Inspiration

A

External intercostal muscles contract and internal relax
Pushing ribs up and out
Diaphragm contracts and flattens
Air pressure in lungs drops below atmospheric pressure as lung volume increases
Air moves in down pressure gradient

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5
Q

Expiration

A

External intercostal muscles relax and internal contract
Pulling ribs down and in
Diaphragm relaxes and domes
Air pressure in lungs increases above atmospheric pressure as lung volume decreases
Air forced out down pressure gradient

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6
Q

Passage of gas exchange

A

Mouth / nose -> trachea -> bronchi -> bronchioles -> alveoli
crosses alveolar epithelium into capillary endothelium

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7
Q

Alveoli structure

A

Tiny air sacs
highly abundant in each lung - 300 million
surrounded by the capillary network
epithelium 1 cell thick

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8
Q

Why large organisms need specialised exchange surface

A

They have a small surface area to volume ratio
higher metabolic rate - demands efficient gas exchange
specialised organs e.g. lungs / gills designed for exchange

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9
Q

Fish gill anatomy

A

Fish gills are stacks of gill filaments
Each filament is covered with gill lamellae at right angles

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10
Q

How fish gas exchange surface provides large surface area

A

Many gill filaments covered in many gill lamellae are positioned at right angles creates a large surface area for efficient diffusion

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11
Q

Countercurrent flow

A

When water flows over gills in opposite direction to flow of blood in capillaries
equilibrium not reached
diffusion gradient maintained across entire length of gill lamellae

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12
Q

Name three structures in tracheal system

A

Involves trachea, tracheoles, spiracles

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13
Q

How tracheal system provides large surface area

A

Highly branched tracheoles
large number of tracheoles
filled in ends of tracheoles moves into tissues during high metabolic activity
so larger surface area for gas exchange

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14
Q

Fluid-filled tracheole ends

A

Adaptation to increase movement of gases
When insect flies and muscles respire anaerobically - lactate produced
Water potential of cells lowered, so water moves from tracheoles to cells by osmosis
Gases diffuse faster in air

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15
Q

How do insects limit water loss(4)

A

Small surface area to volume ratio
Waterproof exoskeleton
Spiracles can open and close to reduce water loss
Thick waxy cuticle - increases diffusion distance so less evaporation

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16
Q

Dicotyledonous plants leaf tissues

A

Key structures involved are
mesophyll layers with many interconnecting air spaces
Palisade and spongy mesophyll - lots of air spaces and chlorophyll.
Stomata created by guard cells

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17
Q

Gas exchange in plants

A

Palisade mesophyll is site of photosynthesis
Oxygen produced and carbon dioxide used creates a concentration gradient
Oxygen diffuses through air space in spongy mesophyll and diffuse out stomata

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18
Q

Role of guard cells

A

Swell - open stomata
Shrink - closed stomata
At night they shrink, reducing water loss by evaporation

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19
Q

Xerophytic plants

A

Plants adapted to survive in dry environments with limited water (e.g. marram grass/cacti)
Structural features for efficient gas exchange but limiting water loss like:
Stomata in sunken pits and small hairs reduce conc extraction gradient as water vapour is trapped
Thick waxy cuticle
Leaves modified to spines which reduces surface area
Roots seep deep down to reach water
Rolling up of leaves as majority of stomata in lower epidermis this traps layer of still air reducing concentration gradient

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20
Q

Adaptations of xerophyte

A

Adaptations to trap moisture to increase humidity -> lowers water potential inside plant so less water lost via osmosis
-sunken stomata
-curled leaves
-hairs
Thick cuticle reduces loss by evaporation
longer root network

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21
Q

Digestion

A

Process where large insoluble biological molecules are hydrolysed into smaller soluble molecules
So they can be absorbed across cell membranes

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22
Q

Locations of carbohydrate
digestion

A

Mouth -> duodenum -> ileum

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23
Q

Locations of protein digestion

A

Stomach -> duodenum -> ileum

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24
Q

Endopeptidases

A

Break peptide bonds between amino acids in the middle of the chain
Creates more ends for exopeptidases for efficient hydrolysis

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25
Q

Exopeptidases

A

Break peptide bonds between amino acids at the ends of polymer chain

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26
Q

Membrane- bound dipeptidases

A

Break peptide bond between two amino acids

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27
Q

Digestion of lipids

A

Bile salts combine with lipids which causes them two split and form tiny droplets called micelles and this increases the S.A for the action of lipase - this is called emulsification
Lipase hydrolyses the ester bonds and forms monoglycerides and fatty acids (non polar and lipid soluble)
Lipase produced in pancreas
Bile salts produced in liver and stored in gall bladder

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28
Q

Lipase

A

Produced in pancreas
Breaks ester bonds in triglycerides to form :
monoglycerides
glycerol
fatty acids

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29
Q

Role of bile salts

A

Emulsify lipids to form tiny droplets called micelles
Increases surface area for lipase action - faster hydrolysis

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30
Q

Micelles

A

Water soluble vesicles formed from fatty acids, glycerol, monoglycerides and bile salts

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31
Q

Lipid absorption

A

Micelles after emulsification and digestion delivers fatty acids, glycerol and monoglycerides to epithelial cells of ileum for absorption
Cross via simple diffusion as these are lipid-soluble and non-polar

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32
Q

Lipid modification

A

Smooth ER reforms monoglycerides / fatty acids into tryglycerides
Golgi apparatus combines tryglycerides with proteins to form vesicles called chylomicrons

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33
Q

How lipids enter blood after modification

A

Chylomicrons move out of cell via exocytosis and enter lacteal
lymphatic vessels carry chylomicrons and deposit them in bloodstream

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34
Q

How are glucose and amino acids absorbed

A

Via co-transport in the ileum
1-Na+ actively transported out of epithelial cells by sodium potassium pump. Takes place in a different type of carrier protein.
2-Thus maintains concentration gradient between lumen and epithelial cells as there is high concentration of Na+ in the ileum compared to epithelial cells
3-So Na+ moves down the concentration gradient into epithelial cells using co transport protein as it carries either amino acids or glucose into the epithelial cells.
4- the glucose or amino acid moves into blood plasma by facilitated diffusion using different type of carrier protein
5-Na+ is down the concentration gradient while glucose/amino acid is against. It’s the movement of Na+ down the concentration gradient rather than ATP which drives this process

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35
Q

Haemoglobin (Hb)

A

Quaternary structure protein - globular protein
2 alpha chains
2 beta chains
4 associated haem groups in each chain containing Fe2+
transports oxygen
Primary structure, secondary structure and
tertiary structure decides the further folding which is an important factor in its ability to carry oxygen

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36
Q

Affinity of haemoglobin

A

The ability of haemoglobin to attract / bind to oxygen

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37
Q

Saturation of haemoglobin

A

When haemoglobin is holding the maximum amount of oxygen it can hold

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38
Q

Loading / unloading of haemoglobin

A

Binding/detachment of oxygen to haemoglobin
also known as association and disassociation

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39
Q

Oxyhaemoglobin dissociation curve

A

Oxygen is loaded in regions with high partial pressures (alveoli)
Unloaded in regions of low partial pressure (respiring tissue)
S shaped

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40
Q

Oxyhaemoglobin dissociation curve shifting left

A

Hb would have a higher affinity for oxygen
Load more at the same partial pressure
Becomes more saturated
Adaptation in low-oxygen environments
e.g. llamas/ in foetuses

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41
Q

Cooperative binding

A

Hb’s affinity for oxygen increases as more oxygen molecules are associated with it
When one binds, Hb’s quaternary structure changes meaning others bind more easily
explaining S shape of curve
Positive cooperativity

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42
Q

How carbon dioxide affects haemoglobin

A

When carbon dioxide dissolves in liquid, carbonic acid forms
decreases pH causing Hb to change shape into one that has lower affinity for O2
at respiring tissues
more oxygen is unloaded
Bohr shift

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43
Q

Bohr effect

A

High carbon dioxide partial pressure- respiring tissues -pH decreases
causes oxyhaemoglobin curve to shift to the right
Low CO2 partial pressure - pH is high eg lungs-alveoli
Causes oxyhemoglobin curve to shift to the left

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44
Q

Oxyhaemoglobin dissociation curve shifting right

A

Hb has lower affinity for oxygen
unloads more at the same partial pressures
less saturated
present in animals with faster metabolisms that need more oxygen for respiration
e.g. birds/rodents

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45
Q

Closed circulatory system

A

Blood remains within blood vessels

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46
Q

Name different types of blood vessels

A

Arteries, arterioles, capillaries, venules and veins

47
Q

Structure of arteries

A

Thick muscular layer compared to veins- smaller arteries control the flow of blood by constricting and dilating
thick elastic layer compared to veins - important to maintain high pressure of blood by stretching and recoiling
thick outer layer - resists the vessel bursting under pressure
small lumen
no valves except in the ones leaving the heart, due to constant high pressure

48
Q

Capillary endothelium

A

Extremely thin
one cell thick
contains small gaps for small molecules to pass through (e.g. glucose, oxygen)
Numerous as they’re highly branched providing larger SA for exchange
Very narrow diameter and can permeate tissues and therefore no cell which is far from capillary

49
Q

Capillaries

A

Form capillary beds
narrow diameter (1 cell thick) to slow blood flow
red blood cells squashed against walls shortens diffusion pathway
small gaps for liquid / small molecules to be forced out

50
Q

Arterioles

A

Branch off arteries
Relatively thicker muscle layer(smooth endothelium) compared to arteries - contraction of this layer constricts the lumen and this restricts blood flow
Helps control movement of blood into capillaries
Thinner elastic layer and outer layer than arteries as pressure lower

51
Q

Tissue fluid

A

Liquid bathing all cells
contains water, glucose, amino acids, fatty acids, ions and oxygen
enables delivery of useful molecules to cells and removal of waste

52
Q

Tissue fluid formation

A

-At arterial end of capillary, high hydrostatic pressure due to pumping of heart and also the smaller diameter
-Hydrostatic pressure is high inside capillaries than outside which causes small molecules forced out (ultrafiltration) through the small gaps in the capillary endothelium, red blood cells / large proteins too big to fit through capillary gaps so remain inside.
-However the osmotic pressure or the water potential is lower inside capillary than outside causing fluid to move back in
-But HP is stronger than osmotic pressure which means the combined effect causes the fluid to move out of capillary

53
Q

Reabsorption of tissue fluid

A

Large molecules remaining in capillary lower its water potential
towards venule end of capillary bed there is lower hydrostatic pressure due to loss of liquid
water reabsorbed back into capillaries by osmosis down the water potential gradient
Not all tissue fluid is reabsorbed by capillaries, the remaining unabsorbed ones are carried back via the lymphatic system which drains their contents back into bloodstream via ducts that joins veins to the heart.

54
Q

Role of the lymph in tissue fluid reabsorption

A

Not all liquid will be reabsorbed by osmosis as equilibrium will be reached
Excess tissue fluid (lymph) is absorbed into lymphatic system and drains back into bloodstream and deposited near heart

55
Q

Cardiac muscle

A

Walls of heart having thick muscular layer
unique because it is:
myogenic - can contract and relax without nervous or hormonal stimulation
never fatigues so long as adequate oxygen supply
Coronary arteries present all through the cardiac muscle which provides oxygenated blood

56
Q

Coronary arteries

A

Blood vessels supplying cardiac muscle with oxygenated blood
branch off from aorta
if blocked, cardiac muscle will not be able to respire, leading to myocardial infarction (heart attack)

57
Q

Structure of heart

A

Labels:
Aorta
Right atrium and ventricle
Left atrium and ventricle
Superior vena cava
Pulmonary artery and vein
Tricuspid valve and mitral or bicuspid
Aortic valve
Inferior vena cava
Pericardium
Semilunar valve

58
Q

Adaptation of left ventricle

A

Has a thick muscular wall in comparison to right ventricle
enables larger contractions of muscle to create higher pressure
ensures blood reaches all body cells

59
Q

Veins connected to the heart(2)

A

Vena cava - carries deoxygenated blood from body to right atrium
Pulmonary vein - carries oxygenated blood from lungs to left atrium

60
Q

Arteries connected to the heart

A

Pulmonary artery - carries deoxygenated blood from right ventricle to lungs
Aorta - carries oxygenated blood from left ventricle to rest of the body

61
Q

Valves within the heart

A

Ensure unidirectional blood flow
Semilunar valves are located in aorta and pulmonary artery near the ventricles
Atrioventricular valves between atria and ventricles

62
Q

Opening and closing of valves

A

Flaps made of fibrous, elastic but strong fibre which forms a cusp like shape
If blood builds in the convex side it is allowed to pass across
If blood collects in the concave side it’s collected and not let through and it passes in one direction
Valves open if the pressure is higher behind them compared to in front of them.
AV valves open when pressure in atria > pressure in ventricles
SL valves open when pressure in ventricles > pressure in arteries

63
Q

The Septum

A

Muscle that runs down the middle of the heart
Separates oxygenated and deoxygenated blood
Maintains high concentration of oxygen in oxygenated blood
Maintaining concentration gradient to enable diffusion to respiring cells

64
Q

Cardiac output

A

Volume of blood which leaves one ventricle in one minute.
Cardiac output = heart rate * stroke volume
heart rate = beats per minute
Stroke volume - amount of blood in one contraction that is pumped from left ventricle of the heart

65
Q

Stroke volume

A

Volume of blood that leaves the heart each beat
measured in dm^3

66
Q

Cardiac cycle

A

Consists of diastole, atrial systole and ventricular systole

67
Q

Diastole

A

Atria and ventricular muscles are relaxed
When blood enters atria via vena cava and pulmonary vein
Increasing pressure in atria
Atrioventricular valves open
Blood flows into the ventricles and this is aided by gravity, relaxation of the ventricle walls causes them to recoil which reduces the pressure of ventricles below that of aorta and pulmonary artery causing semilunar valves to close
This is accompanied by the characteristic dub sound of heart beat

68
Q

Atrial systole

A

Contraction of the atrial walls along with the recoiling of the relaxed ventricle’s walls forces the remaining blood into ventricles from atria
Throughout this stage ventricle relaxed.

69
Q

Ventricular systole

A

After a short delay (so ventricles fill), ventricle walls contract simultaneously which increases the pressure in ventricle
Pressure ventricle > atria causes atrioventricular valve to shut
This increases the pressure further in ventricles
When pressure in ventricles > pressure in pulmonary artery and aorta semilunar valves open and blood moves to those
Left ventricle more thicker than right as left has to pump blood to the whole body including extremities so contraction of LV has higher pressure
Right ventricle pumps blood to lungs

70
Q

Transpiration

A

Loss of water vapour from stomata by evaporation affected by:
light intensity
temperature
humidity
wind
can be measured in a lab using a potometer

71
Q

How light intensity affects transpiration

A

As light intensity increases, rate of transpiration increases
more light means more stomata open
larger surface area for evaporation

72
Q

How temperature affects transpiration

A

As temperature increases, rate of transpiration increases
the more heat there is, the more kinetic energy molecules have
faster moving molecules increases evaporation

73
Q

How humidity affects transpiration

A

As humidity increases, transpiration decreases
the more water vapour in the air, the greater the water potential outside the leaf
reduces water potential gradient and evaporation

74
Q

How wind affects transpiration

A

As wind increases, rate of transpiration increases
the more air movement, the more humid areas are blown away
maintains water potential gradient, increasing evaporation

75
Q

Cohesion in plant transport

A

Because of the dipolar nature of water, hydrogen bonds can form - cohesion
water can travel up xylem as a continuous column

76
Q

Adhesion in plant transport

A

Water can stick to other molecules (xylem walls) by forming H-bonds
helps hold water column up against gravity

77
Q

Root pressure in plant transport

A

As water moves into roots by osmosis, the volume of liquid inside the root increases therefore the pressure inside the root increases
this forces water upwards down the water potential gradient

78
Q

Cohesion- tension theory

A

Water forms continuous, unbroken column across the mesophyll cells and xylem
As water evaporates out the stomata or mesophyll cells due to heat from sun, this lowers water potential
Causes water molecules to be pulled from behind i.e xylem due to this cohesion.
Column of water is therefore pulled up xylem due to transpiration- transpirational pull
Along with cohesion, water molecules also adhere to walls of xylem
The transpirational pull creates tension in xylem pulling xylem inwards
Negative pressure in xylem

79
Q

Translocation

A

Occurs in phloem
explained by mass flow hypothesis
transport of organic substances through plant

80
Q

Sieve tube elements

A

Living cells
contain no nucleus
few organelles
this makes cell hollow
allowing reduced resistance to flow of sugars

81
Q

Companion cell

A

Provide ATP required for active transport of organic substances
contains many mitochondria

82
Q

Mass flow hypothesis

A

Organic substances, sucrose, move in solution from leaves (after photosynthesis) to respiring cells
source -> sink direction

83
Q

How is pressure generated for translocation

A

Photosynthesising cells produce glucose which diffuses into companion cell by facilitated diffusion
Companion cells actively transports H+ ions into spaces within cell wall of companion cells
The H+ ions move down the concentration gradient via co transport protein into seive tube elements as it also transports sucrose molecules along with it.
This lowers water potential of phloem so water moves in from xylem via osmosis as xylem has higher water potential
Hydrostatic pressure gradient generated

84
Q

What happens to sucrose after translocation?

A

Used in respiration at the sink
stored as insoluble starch

85
Q

Investigating translocation

A

Can be investigated using tracer and ringing experiments
proves phloem transports sugars not xylem

86
Q

Tracing

A

Involves radioactively labelling carbon - used in photosynthesis
create sugars with this carbon
thin slices from stems are cut and placed on X-ray film which turns black when exposed to radioactive material
stems will turn black as that is where phloem are

87
Q

Ringing experiments

A

Ring of bark (and phloem) is peeled and removed off a trunk
consequently, the trunk swells above the removed section
analysis will show it contains sugar
when phloem removed, sugar cannot be transported

88
Q

How do small organisms exchange gases

A

Simple diffusion
across their surface

89
Q

Why don’t small organisms need breathing systems

A

They have a large surface area to volume ratio
no cells far from the surface

90
Q

How alveoli structure relates to its function

A

Round shape & large number in - large surface area for gas exchange (diffusion)
Lined with epithelium and epithelial cells are flat and very thin to minimise diffusion distance
Capillary network maintains concentration gradient
Contains collagen and elastic fibres between alveoli allows it to stretch and recoil during inspiration and exhalation

91
Q

How fish gas exchange surface provides a short diffusion distance

A

Thin lamellae epithelium means short distance between water and blood
capillary network in every lamella

92
Q

How fish gas exchange surface maintains diffusion gradient

A

Counter-current flow mechanism - water and blood flows in opposite direction which means equilibrium is never reached
Circulation replaces blood saturated with oxygen
Ventilation replaces water with oxygen removed

93
Q

Name of gas exchange system in terrestrial insects

A

Tracheal system

94
Q

Describe structure of spiracles

A

Round, valve-like openings
running along the length of the abdomen

95
Q

Describe trachea & tracheoles structure

A

Network of internal tubes
Have rings of cartilage adding strength and keeping them open
Trachea branch into smaller tubes - tracheoles
Tracheoles extend through all tissues delivering oxygen to insects

96
Q

How tracheal system provides short diffusion distance

A

Tracheoles have thin walls so short diffusion distance to cells

97
Q

How tracheal system maintains concentration gradient

A

Mass transport - muscle contraction squeezes trachea which enables mass movement of air in and out and this speeds up exchange.
Use of oxygen in respiration and production of CO2 sets up steep concentration gradients

98
Q

Amylase

A

Produced in pancreas & salivary gland
hydrolyses starch into maltose

99
Q

Membrane-bound disaccharidases

A

Maltase / sucrase / lactase
hydrolyse disaccharides into monosaccharides

100
Q

Enzymes involved in protein digestion

A

endopeptidases
exopeptidases
membrane-bound dipeptidases

101
Q

Products of protein digestion

A

Large polymer proteins are hydrolysed to amino acids

102
Q

Double circulatory system

A

Blood passes through heart twice
pulmonary circuit delivers blood to/from lungs
systemic circuit delivers blood to the rest of the body

103
Q

Coronary arteries

A

Supply cardiac muscle with oxygenated blood
for continued respiration and energy production for contraction

104
Q

Blood vessels entering / exiting the kidney

A

Renal artery carries oxygenated blood to kidney
Renal vein carries deoxygenated blood to heart

105
Q

Blood vessels entering / exiting the lung

A

Pulmonary artery carries deoxygenated blood to lung
pulmonary vein carries oxygenated blood to heart

106
Q

Blood vessels entering / exiting the heart

A

Vena cava carries deoxygenated blood to heart (right atrium)
aorta carries oxygenated blood to body
pulmonary artery - carries blood from the heart to the lungs
pulmonary vein - carries blood from the lungs into the heart

107
Q

Describe then structure of veins

A

Thin muscular layer compared to arteries as they carry blood away from the body so constriction and dilation cannot control the flow of blood
thin elastic layer - as low pressure it’s too low to create a recoil action
thin walls- very low pressure so no risk of bursting
valves - due to low pressure makes sure blood flows in one direction, prevents back flow.

108
Q

Explain role of elastic layer in arteries

A

Thick elastic layer
to help maintain blood pressure
by stretching and recoiling

109
Q

Describe the elastic layer in veins

A

Thin elastic layer as pressure lower
cannot control the flow of blood

110
Q

Explain the role of valves in veins

A

Due to low pressure in veins
skeletal muscle usually used to flatten walls of veins for blood flow
valves prevent the backflow of blood
unidirectional flow

111
Q

What causes the AV valves to open

A

Higher pressure in the atria than in the ventricles

112
Q

What causes the semi-lunar valves to open

A

Higher pressure in the ventricles than in the arteries

113
Q

Tell me about the lymphatic system

A

System of vessels that begin in the tissues
Carry lymph which are the excess fluid which wasn’t reabsorbed by capillaries as equilibrium reached
Initially they resemble capillaries except they have a dead ends
Gradually merges into lager vessels that forms a network around the body
These vessels drain their content back into the bloodstream via ducts that joins veins to the heart

Biology A Level (9 decks)

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