3 - Substance Exchange Flashcards
1
Q
When does the need for a specialized exchange surface arise?
A
As the size of an organism, and its SA:V ratio increases
2
Q
What is required for an efficient exchange surface?
A
Large SA
Thin
Good blood supply / Ventilation
3
Q
Fish membrane
A
Impermeable - gases can’t diffuse through skin
4
Q
How many pairs of gills do bony fish have?
A
4 Pairs
5
Q
What supports each fish gill?
A
An arch
6
Q
What is located across each arc supporting fish gills?
A
Multiple projections called gill filaments, with lamallae on them which participate in gas exchange
7
Q
How do blood and water flow across the lamellae?
A
In a counter-current
8
Q
Benefit of counter-current exchange system in fish
A
Maintains a steep concentration gradient so the maximum amount of oxygen is diffusing into the deoxygenated blood from the water
9
Q
How are projections held apart?
A
By water flow
This means they stick together in the absence of water and the fish cannot survive
10
Q
What is required to maintain a continuous unidirectional flow in fish?
A
Ventilation
11
Q
How does ventilation begin in fish?
A
Fish opens its mouth, followed by lowering the floor of buccal cavity
12
Q
Effect of lowering the floor of buccal cavity
A
Enable water to flow in
13
Q
What happens after water flows in, in fish ventilation?
A
The fish closes its mouth, causing the buccal cavity floor to raise, increasing the pressure
14
Q
What causes the water to be forced over the gill filaments in fish ventilation?
A
The difference in pressure between the mouth cavity and opercular cavity
15
Q
Role of operculum in fish ventilation
A
Acts as a valveand pump and lets water out and pumps it in
16
Q
How is oxygen obtained in insects?
A
Oxygen needs to be transported directly to tissues undergoing respiration
17
Q
Spiracles
A
Small openings of tubes along the thorax and abdomen
18
Q
Trachea / tracheoles
A
Network of small tubes that carry oxygen around the insect body
19
Q
How is oxygen transported directly into respiring tissues in insects?
A
With the help of spiracles and either bigger trachea or smaller tracheoles
Gases move in and out through diffusion
20
Q
What is mass transport in insects a result of?
A
Muscle contraction and volume changes in the tracheoles
21
Q
Stomata
A
Small holes in leaves which allow gases to enter and leave
22
Q
Purpose of air spaces in leaves
A
Allows gases to move around the leaf and easily come into contact with photosynthesising mesophyll cells
23
Q
The Lungs
A
A pair of lobed structures with a large surface area located in the chest cavity that are able to inflate
24
Q
Rib Cage
A
Surrounds the lungs to protect them
25
How is friction between the lungs and ribs prevented?
Secretion of a lubricating substance
26
Diaphragm
Separates the lungs from the abdomen area
27
What contracts to raise and lower the ribcage respectively?
External and internal intercostal muscles
28
How does air enter humans?
Through the nose, along the trachea, bronchi and bronchioles
29
Where does gaseous exchange take place in humans?
Alveoli - tiny sacs filled with air
30
What structures allow the flow of air into and out of the lungs?
Trachea, bronchi and bronchioles
31
How are human airways held open?
Rings of cartilage, which are incomplete in the trachea to allow the passage of food down the oesophagus behind the trachea
32
Wall of trachea and bronchi
Composed of several layers which together make a thick wall
The wall is mostly composed of cartilage, in the form of incomplete C rings
33
Inside surface of Cartilage of trachea and bronchi
Layer of loose tissue
34
Inner lining of Cartilage of trachea and bronchi
Epithelial layer composed of ciliated epithelium and goblet cells
35
What are bronchiole walls made of?
Smooth muscle and elastic fibre
36
How are the alveoli adapted for transport?
1 cell thick - surrounded by capillaries which are also 1 cell thick - reduces diffusion distance
Constant blood supply by capillaries maintains a steep concentration gradient
Large number of alveoli - Increase SA
37
Role of Cartilage in gas exchange
Supporting the trachea and bronchi
Plays an important role in preventing the lungs from collapsing in the event of pressure drop during excitation
38
Ciliated Epithelium in gas exchange
Present in bronchi, bronchioles and trachea
Moving mucus along to prevent lung infection by moving it towards the throat where it can be swallowed
39
Goblet cells in gas exchange
Present in trachea, bronchi and bronchioles
Involved in mucus production to trap bacteria and dust to reduce the risk of infection with the help of lysozymes which digest bacteria
40
Smooth Muscle in gas exchange
Their ability to contract enables them to play a role in constricting the airway
Controlling diameter which controls the flow of air from the alveoli
41
Elastic fibres in gas exchange
Stretch when we exhale and recoil when we inhale, thus controlling flow of air
42
2 stages of ventilation
Inspiration
Expiration
43
Inspiration
External intercostal muscles contract
Internal muscles relax
Ribs raise upwards
Diaphragm contracts and flattens
44
Effect of intercostal muscles and diaphragm in inspiration
Cause the volume inside the thorax to increase, lowering the pressure
The difference between the pressure inside the lungs and atmospheric pressure creates a gradient, causing air to be forced into the lungs
45
Expiration
Internal intercostal muscles contract
External muscles relax, lowering rib cage
Diaphragm relaxes and raises upwards
Decreases the volume in the thorax, forcing air out of the lungs
46
Spirometer
Used to measure lung volume
47
Vital Capacity
The max volume of air that can be inhaled or exhaled in a single breath
48
Tidal Volume
The volume of air we breathe in and out at each breath at rest
49
How can breathing rate be calculated from the spirometer?
Counting the number of peaks in a minute
50
Residual Volume
Volume of air always present in lungs
51
Expiratory reserve volume
Additional volume of air that can be exhaled on top of the tidal volume
52
Digestion
The hydrolysis of large biological molecules into smaller molecules which can be absorbed across cell membranes
53
Amylase
In the mouth, digests larger Carbohydrate polymers
54
Maltase
In the ileum, break down monosaccharides
55
Sucrase and lactases
Break down the disaccharides sucrose and lactose respectively
56
How are lipids digested?
Lipases hydrolyses the ester bond between the monoglyceride and fatty acid
57
What happens before lipids are broken down in the ileum?
Lipids are emulsified into micelles by bile salts released from the liver
58
Where are lipids broken down?
Ileum
59
How are lipids emulsified into micelles?
By bile salts released by the liver
60
Effect of emulsification of lipids
Increases the SA and speeds up the chemical reaction
61
Endopeptidases
Hydrolyses peptide bonds between specific amino acids in the middle of the polypeptide
62
Exopeptidases
Hydrolyses bonds at the ends of a polypeptide
63
Dipeptidase
Hydrolyses dipeptides into individual amino acids
64
What happens to products of digestion?
Absorbed by cells lining the ileum of mammals
65
How are amino acids absorbed?
Facilitated diffusion through specific carrier molecules in the surface membrane of epithelial cells
66
Why can monoglyceride and fatty acids easily diffuse across the cell membrane?
They are polar
67
Advantage of monoglyceride and fatty acids being polar
Easily diffuse across the cell membrane into the eithelial cells lining the epithelium
68
What happens once monoglyceride and fatty acids are inside the cell?
They are transported to the endoplasmic reticulum where they are reformed into triglycerides.
69
What happens once monoglycerides and fatty acids have been reformed into triglycerides by the endoplasmic reticulum?
They move out of the cells by vesicles in the lymph system
70
Haemoglobin
Water soluble globular protein, Consisting of 2 beta polypeptide chains and 2 alpha helices
71
What does each molecule in haemoglobin molecule form?
A complex containing a haem group
72
How does haemoglobin carry oxygen in the blood?
Oxygen can bind to the haem group
Each molecule can carry 4 oxygen molecules
73
What does the affinity of oxygen for haemoglobin depend on?
Partial pressure of oxygen
74
What happens as partial pressure of oxygen increases?
The affinity of haemoglobin for oxygen increases
75
Effect of respiration on affinity of oxygen for haemoglobin
During respiration, oxygen is used up and therefore the partial pressure decreases, decreasing the affinity of oxygen for haemoglobin
76
Loading
Oxygen binds tightly to haemoglobin
77
Result of decreased affinity of oxygen for haemoglobin
Oxygen is released in respiring tissues where it is needed
78
What happens after the unloading process of oxygen>
Haemoglobin returns to the lungs where it binds to oxygen again
79
Why does fetal haemoglobin have a greater affinity for oxygen?
It needs to be better as absorbing oxygen as by the time oxygen reaches the placenta, the oxygen saturation of the blood has decreased
80
How is fetal haemoglobin different from adult haemoglobin?
It has a higher affinity for oxygen in order for the foetus to survive at low partial pressure
81
Effect of CO2 on haemoglobin affinity for oxygen
Presence of CO2 decreases the haemoglobin affinity for oxygen, causing it to be released
82
Bohr effect
Presence of CO2 decreasing the affinity of haemoglobin for oxygen, causing it to be released
83
How does CO2 cause oxygen to be released from haemoglobin?
CO2 creates slightly acidic conditions which change the shape of the haemoglobin protein, making it easier for the oxygen to be released
84
Why is a circulatory system needed in large organisms?
The SA:V is not large enough to for difussion alone to supply substances like oxygen, glucose and other molecules to cells where they are needed
85
Common Features of a circulatory system
Suitable medium
Means of moving medium
Mechanism to control flow around the body
Close system of vessels
86
Suitable transport medium in mammals
In mammals the transport medium is the blood
It is water based so substances can easily dissolve into it
87
Means of moving the medium (blood) in mammals
Animals often have a pump known as the heart to maintain pressure differences around the body
88
Mechanism to control flow around the body
Valves are used in veins to prevent any backflow
89
Close system of vessels
The circulatory system in most animals and plants is closed and is branched to deliver substances to all parts of the body
90
Circulatory system in mammals
Closed double circulatory system
91
2 Pumps of the heart
One pumps blood to the lungs to be oxygenates
The other is larger and stronger and pumps the oxygenated blood around the body to supply vital organs and tissues
92
Atrium - Features
Thin walled and elastic
Can stretch when filed with blood
93
Ventricle
Thick muscular wall to pump blood around the body or to the lungs
94
Why are 2 Pumps required in the heart?
Maintain blood pressure around the whole body
95
Why would just 1 pump in the heart not be able to maintain blood pressure around the whole body?
The slow down of blood as it passes the lungs would cause it to lose all pressure
96
4 main vessels connecting the heart
Aorta
Pulmonary artery
Pulmonary vein
Vena cava
97
Aorta - role
Connected to the left ventricle and carries oxygenated blood to all parts of the body, except the lungs
98
Pulmonary artery
Connected to the right ventricle and carries deoxygenated blood to the lungs where it is oxygenated and the CO2 is removed
99
Pulmonary vein
Connected to the left atrium and brings oxygenated blood back from the lungs
100
Vena cava
Connected to the right atrium and brings deoxygenated blood back from the tissues except the lungs
101
Why is the heart myogenic
Due to its ability to initiate its own contractions
102
Sinoatrial node
Located in the wall of the right atrium
Region of specialisedfibres which is the pacemaker of the heart
103
Role of sinoatrial node as pacemaker
Initiates a wave of electrical stimulation which causes the atria to contract at roughly the same time
104
Why do the ventricles not start contractin until the atria have finished?
Due to the presence of tissue at the base of the atria which is unable to conduct the wave excitation
105
Where is the atrioventricular valve located?
Between the 2 atria
106
Role of AV valve in ventricle contraction
Once the electrical wave reaches the AV valve, it passes on the excitation to ventricles, down the bundle of His to the apex of the heart
107
Bundle of His in ventricle contraction
Branches into purkyne fibres which carry the wave upwards, causing the ventricles to contract, thus emptying them
108
Why do the ventricles contract upwards?
In order to force the most blood possible upwards out of the aorta and pulmonary artery
109
3 stages of the cardiac cycle
1. Cardiac diastole
2. Atriole systole
3. Ventricular systole
110
Adaptations of the arteries
Thick wall to withstand high pressure
Elastic tissue to allow them to stretch and recoil
Smooth muscle - vary flow of blood
Smooth endothelium - reduce friction and ease flow of blood
111
Role of arteries
Carry blood away from the heart towards the rest of the body
112
Role of arterioles
Feed blood into capillaries
113
Adaptations of Arterioles
Thinner
Less muscular walls
114
Where are arterioles located?
Branch off arteries
115
Smallest blood vessel
Capillaries
116
Role of Capillaries
Site of metabolic exchange
117
Adaptation of arterioles
1 cell thick for fast substance exchange
118
Venules
Larger than capillaries but smaller than veins
119
Role of Veins
Carry blood from the body to the heart
120
Adaptation of Veins
Wide lumen - maximise volume of blood carried to heart
Thin walled - blood under low pressure
Valves - prevent backflow of blood
121
Tissue fluid
A liquid containing dissolved oxygen and nutrients which serves as a means of supplying the tissues with essential solutes in exchange for waste products such as CO2
122
When is hydrostatic pressure created?
When blood is pumped along the arteries, into arterioles and then capillaries
123
Effect on hydrostatic pressure on the capillaries
Forced blood fluid out of the capillaries
124
Effect of hydrostatic pressure on tissue fluid
Pushes some of the fluid back into the capillaries
125
Why do the tissue fluid and blood have a negative water potential?
They both contain solutes
126
Why is the water potential of the blood more negative than the water potential of tissue fluid?
The blood contains more solutes
127
Effect of tissue fluid having a more positive water potential than the blood
Causes water to move down the water potential gradient from the tissue fluid to the blood by osmosis
128
What happens to remaining tissue fluid which is not pushed back into the capillaries?
Carried back via the lymphatic system
129
What does the lymphatic system contain?
Lymph fluid
Less oxygen and nutrients than tissue fluid
130
Main purpose of the lymph fluid
Carry waste products
131
Role of lymph nodes in the lymph system
Filter out bacteria and foreign material from the fluid with the help of lymphocytes
132
Role of lymphocytes
Destroy pathogens as part of the immune system
133
Why do plants require a transport system?
Ensure that all the cells of a plant receive a sufficient amount of nutrients
134
Role of Xylem tissue
Enables water as well as dissolved minerals to travel up the plant in the passive process of transpiration
135
Role of phloem tissue
Enables sugars to reach all parts of the plant in the active process of translocation
136
What are xylem and phloem components of?
Vascular bundle
137
Role of vascular bundle
Enables the transport of substances as well as provide structural support
138
How are the xylem vessels arranges?
Benefit?
In an X shape in the centre of the vascular bundle
Enables the plant to withstand various mechanical forces such as pulling
139
What is the X shape arrangement of the xylem vessels surrounded by?
Endodermis
140
Endodermis
Outer layer of cells which supply xylem vessels with water
141
Where is the xylem located?
On the inside in non-wooded plants to provide support and flexibility in the stem
142
Where is the phloem found?
On the outside of the vascular bundle
143
Cambium
Between the xylem and phloem
Meristem cells involved in the production of new xylem and phloem tissue
144
What does the vascular bundle in leaves form?
The midrib and veins of a leaf
145
Transpiration
The process by which water moves through xylem vessels in plants
146
Structure of Xylem vessels
Long cylinders made of dead tissue with open ends, therefore they can form an open column
147
Role of pits in xylem vessels
Enables water to move sideways between vessels
148
Lignin in xylem vessels
Thickens xylem vessels
Deposited in spiral patterns to enable the plant to remain flexible
149
The process of transpiration
Plants absorb water through the roots, which then move through the plant and is released into the atmosphere as water vapour through pores in the leaves
150
transpiration stream
The movement of water up the stem, enabling processes such as photosynthesis, growth and elongation as it supplies the plant with water
151
Roles of transpiration stream
Supplies plant with water and required minerals
Enables plant to control its temperature via evaporation of water
152
How does transpiration involve osmosis?
Water moves from the xylem to mesophyll cells
153
Evaporation in transpiration
Evaporation from the surface of mesophyll cells into intercellular spaces
154
Diffusion in Transpiration
Diffusion of water down a water potential gradient and out of the stomata
155
Xerophytes
Plants adapted to living in dry conditions
156
Adaptations of xerophytes
Smaller leaves - reduce SA for water loss
Densely packs mesophyll and thick waxy cuticle to prevent water loss via evaporation
157
How do xerophytes respond to low water availability?
Closing stomata to prevent water loss
158
Role of hairs and pits in xerophyes
Serve as a mean for trapping moist air, reducing the water vapour potential gradient
159
Why do xerophytes roll their leaves?
Reduce the exposure of the lower epidermis to the atmosphere, trapping air that is moist
160
What happens once water enters through root hair cells?
Moves into the xylem tissue located in the centre of the root
161
What causes water to move into the xylem tissue from the root hair cells?
Water potential gradient
162
Why is the water potential higher inside the soil than inside the root hair cells?
Dissolved substances in cell sap
163
Purpose of root hair cells
Provide a large SA for the movement of water to occur
164
How are minerals absorbed through the root hair cells?
Active transport
165
What is the push of water upwards aided by?
Root pressure
166
Root pressure
The action of the endodermis moving minerals into the xylem by active transport drives water into the xylem by osmosis, pushing it upwards
167
Cohesion-tension theory
Combination of surface tension of water and cohesion helps maintain the flow of water in the xylem up the stem
168
What is cohesion-tension theory supported by?
Capillary action where the forces involved in cohesion cause the water molecule to adhere to the walls of the xylem
169
Where do translocation primary occur?
Phloem vessels
170
Structure of phloem vessels
Tubes made of living cells involved in translocation of nutrients to storage organs and growing parts of the plant
171
What do phloem vessels consist of?
Sieve tibe elements and companion cells
172
Role of sieve tube elements
Form a tube to transport sugars such a as sucrose, in the dissolved form of sap
173
Role of companion cells
Involved in ATP production for active processes such a as loading sucrose into sieve tubes
174
How is the cytoplasm of the sieve tube elements and companion cells linked?
Plasmodesmata
175
Plasmodesmata
Gaps between cell walls which allow communication and flow of substances such as minerals between the cells
176
How does sucrose enter the phloem?
Active transport
Companion cells use ATP to transport hydrogen ions into the surrounding tissue, creating a diffusion gradient, which causes H+ to diffuse back into the companion cells
177
What allows Sucrose molecules to return to the companion cells?
Facilitated diffusion involving co-transporter proteins
Allows the returning H+ ions to bring sucrose molecules into the companion cell
178
Result of increased sucrose concentration in companion cells
Sucrose diffuses out of the companion cells down the concentration gradient into the sieve tube elements, via the plasmodesmata
179
Effect of sucrose entering sieve tube elements
Water potential inside tube is reduced. Causing water to enter from the xylem via osmosis, increasing the hydrostatic pressure of the sieve tube element
180
Result of high hydrostatic pressure of the sieve tube element
Water moved down the sieve tube from an area of high hydrostatic pressure to an area of low hydrostatic pressure
181
Effect of removing sucrose from sieve tube element
Increases water potential in sieve tube, meaning water leaves sieve tube by osmosis back into the xylem
Reduces the pressure in the phloem at the sink
182
Evidence for mass transport
Pressure in sieve tube elements - shown by sap being released when the stem of a plant is cit
Sucrose concentration is higher in leaves than roots
Increase in sucrose levels in the leaves are followed by a similar increase in sucrose concentration in the phloem
Metaboloc poisons inhibit translocation of sucrose in the phloem
183
Evidence against mass transport
Function of sieve plate is unclear as they would appear to hinder mass flow
Not all solutes move at the same speed, as they should if it is mass flow
Sucrose is delivered at similar rates to all regions, rather than going more quickly to those with the lowest concentration
184
Ringing Experiment
Bark and phloem of tree removed, leaving only xylem
Tissues above missing ring swell with sucrose and tissue below dies
shows sucrose is transported in the phloem
185
Tracer experiments
Plants are grown in an environment containing radioactivity labelled CO2.
Incorporated into the sugar production in photosynthesis
Movement of these sugars can be traced using autoradiograohy
Exposed areas appear black
These regions correspond to the areas where the phloem is and therefore suggest that this is where the sugars are transported
186
Gills
Filaments of thin tissue that are highly branched and folded
187
What happens as water flows through the gills?
Oxygen in the water diffuses quickly into the bloodstream
188
Counter-current system in fish
Blood flows through the lamellae in the opposite direction of the flow of water through the gills
189
Mesophyll cells
Site of photosynthesis and are lpcated in the middle layer of plant leaves
Large SA for rapid gas exchange
190
Epidermis
Underside of the leaf
191
Guarg cells
Swell to open stomata
192
Where does plant gas exchange take place?
Mesophyll cells
193
Role of waxy cuticle in terrestrial insects
Prevents water loss
194
Role of hairs on spiracles
Decrease the water potential gradient between inside the trachea and the environment
195
Adaptations to reduce water loss in insects
Closing of spiracles
Hairs around the spiracles
Waxy cuticle on body
196
Features of xerophytic plants
Waxy cuticle
Stomata in sunken pit
Fewer stomata
Hairs on epidermis
Curled leaves
197
Trachea
Entrance to the human gas exchange system
198
What provides protection and structure to the trachea?
Ridges of cartilage surrounding the front of the trachea
199
Why is there no cartilage at the back of the trachea?
So that the oesophagus is not restricted
200
Bronchi
The trachea divides into 2 bronchi
Air flows along each bronchus to a lung
201
What are bronchi made from?
Cartilage and smooth muscle
202
Bronchioles
Each bronchus divides into many smaller bronchioles
The many bronchioles branch throughout the lungs into small air-sacs called alveoli
203
What is ventilation controlled by?
Ribcage
Intercostal muscles
Diaphragm
204
What surrounds each alveolus?
A network of capillaries
205
What makes up the epithelium?
A single layer of epithelium cells that line the walls of the alveoli
206
Muscle contraction in inspiration
External intercostal muscles contract
Diaphragm contracts and moves down
Energy required to power muscle contraction
207
Thoracic cavity in inspiration
External intercostal muscles move the ribcage up and out
Diaphragm moves down
Volume of thoracic cavity increases
208
Lung pressure decrease in inspiration
Increasing volume in thoracic cavity causes pressure in the lungs to decrease
Pressure gradient established between outside and inside lungs
209
Air flow in inspiration
Air flows inside the lungs down the pressure gradient
Air flows down the trachea and into the alveoli
210
Hydrolysis of protein
Amino acids
211
Hydrolyses of carbobhydrates
Disaccharides and monosaccharides
212
Hydrolysis of lipids
Farry acids and monoglycerides
213
Where is amylase produced?
Salivary glands and pancreas
214
Role of amylase
Catalyses hydrolysis of starch into maltose by breaking a glycosidic bond
215
Membrane-bound disaccharidases
Enzymes in the cell membranes of epithelial cells in the ileum
Catalyse hydrolysis of disaccharides
216
How are monosaccharides transported into the epithelial cells in the ileum?
Transporter proteins
217
What monosaccharides use co-transporter proteins?
Glucose and galactose
218
Which monosaccharide uses facilitated diffusion?
Fructose
219
Where is lipase produced
Produced by the pancreas and released by the small intestine
220
Where are bile salts produced?
Liver
221
Role of bile salts
Help digest lipids by forming small lipid droplets called micelles
222
Emulsification
Process of forming micelles
223
Role of micelles
Allow the monoglycerides and fatty acids to be absorbed by the epithelial cells in the ileum
224
Where are sodium-dependent co-transporter proteins located?
Epithelial cells membrane
225
Role of co-transporter proteins
Actively transport sodium ions into the blood, causing the concentration of sodium ions in the epithelial cells to decrease
226
What happens when sodium ions bind to a co-transporter proteins?
Amino acids or monosaccharides also bind to the protein
227
What is the effect of amino acids or monosaccharides binding to the transporter protein
Transporter proteins undergoes a conformation change, allowing it to cross the epithelial cells membrane
228
Quaternary structure of haemoglobin
Haemoglobin is a protein made from 4 different polypeptide chains
The 4 chains give haemoglobin a quaternary structure
229
Haem groups
Each polypeptide chain of haemoglobin has a haem group
A haem groups is a prosthetic group attached to a protein
Contains an iron ion
230
What makes haemoglobin red?
Iron ion
231
Dissociation
When RBCs reach tissues, oxygen is released from oxyhaemoglobin
232
Shape of oxygen dissociation curve
S-Shaped
233
Coronary artery
Supplies blood to the heart
234
Movement of deoxygenated blood from the heart
Pumped out of the heart to the lungs via the pulmonary artery in the right ventricle
235
Movement of oxygenated blood from the lungs
Flows into the heart via the pulmonary vein in the left atrium
236
Movement of oxygenated blood from the heart
Pumped out of the heart and around the body via the aorta in the left ventricle
237
Blood pressure in aorta
Very high
238
What happens as oxygenated blood is pumped around the body?
Oxygen dissociates from the blood at respiring cells in the body and the blood becomes deoxygenated
239
Movement of deoxygenated blood from the body
Flows into the heart from the body via the vena cava in the right atria
240
How does oxygenated blood enter the kidney?
Through the renal artery
241
How does deoxygenated blood leave the kidney?
Renal vein
242
Role of AV valves
Prevent backflow of blood into the atria
243
Role of Semi-lunar valves
Prevent backflow of blood into the ventricles
244
Pulmonary vein
Pumps oxygenated blood into the atria
245
Atria contraction
Blood from the lungs flow into the left atrium and blood from the body flows into the right atrium simultaneously
The atria contract, increasing pressure
Blood in atria forced into ventricles
Ventricles relaxed and filled with blood
246
Ventricular Contraction
Contraction of ventricles increases pressure
Pressure shuts AV valves to prevent backflow of blood
Blood in ventricles is forced out of the heart through the pulmonary artery or aorta
247
What happens as the ventricles relax and the AV valves reopen reopen?
Blood flows into the ventricles and the atria from the pulmonary vein and vena cava
248
Role of arterioles
Control direction of blood flow by constricting and contracting
249
Vein wall
Thin muscle and elastic tissue
250
Artery wall
Elastic fibre to allow them to stretch
251
Role of capillaries
Creates a large surface area for exchange of substances between bloodstream and tissues
252
Steps in the Formation of Tissue Fluid
Fluid is forced out of the capillaries by pressure filtration
Substances in the tissue fluid diffuse into cells
Water ppotential insidecapillaries decreases
Water moves by osmosis back into capillaries from tissue fluid
Excess tissue fluid flows into the lymphatic system
253
How might the endothelium of arteries become damaged?
Deposition of WBCs and lipids
254
What happens in WBCs and fatty materials continue to be deposited in the artery walls?
The materials will begin to form hard, fibrous plaque
255
Atheroma
Presence of fibrous plaque
256
Effects of the narrowing lumen due to plaque build up
Blood flow through arteries is restricted
The narrower lumen also increases blood pressure
257
Effect of arethomas
Cause heart disease
258
Risk factors for cardiovascular disease
Smoking
Diet
High blood pressure
259
What are the walls of Xylem lined with?
Lignin - waterproof polymer which reinforces the walls of the vessel elements to provide structural support
260
Sieve tube elements
Cells that make up the phloem vessel
Living - contain cytoplasm but no nucleus
Walls made of cellulose
261
Role of sieve plates
Lare pores allow sap to move through the sieve tube element
Allow sugars to be transported through the phloem
262
Translocation
The process by which sucrose produced in photosynthesis is transported from the leaves to the sink cells
