Respiration Flashcards
(243 cards)
1
Q
What do animals need to take in from the external environment?
A
food and oxygen
2
Q
What do plants need to take in from the external environment?
A
the raw materials necessary to carry out photosynthesis mineral nutrients and oxygen
3
Q
What do both animals and plants have to do?
A
get rid of waste products from their bodies to the exterior
4
Q
How does a simple unicellular organism like Amoeba carry out material exchanges?
A
through its external body surface by diffusion
5
Q
Up to what size can Amoeba effectively exchange materials by diffusion?
A
a certain limit
6
Q
What happens as the Amoeba increases in size?
A
it stops growing and divides into two
7
Q
What happens to the surface area to volume ratio as the Amoeba increases in size?
A
it decreases
8
Q
What is the ability of the Amoeba to exchange materials in a given time related to?
A
its surface area ie the larger the surface area the greater the ability to exchange materials
9
Q
How are the needs of the Amoeba like oxygen intake and carbon dioxide excretion related to its size?
A
the larger the volume the greater the needs of the Amoeba
10
Q
What happens to the Amoeba’s ability to exchange materials as it increases in size?
A
its ability to carry out material exchange cannot cope with its needs
11
Q
What becomes a limiting factor as an organism increases in size?
A
the S.A./V ratio
12
Q
What multicellular organisms increased their S.A./V ratio by developing structures such as the gut?
A
Hydra and flatworm
13
Q
Beyond what size could Hydra and flatworm not grow?
A
a certain size
14
Q
What becomes a limiting factor preventing the development of larger and more complex bodies?
A
the process of diffusion
15
Q
How close are all the body cells to the material exchange surfaces in Hydra and flatworm?
A
very near
16
Q
What is sufficient to transport materials between the exchange surfaces and the cells in Hydra and flatworm?
A
Diffusion
17
Q
Over what distance is diffusion efficient?
A
1 mm or less
18
Q
What happens to diffusion as distances between the body cells and the exchange surface increase?
A
it becomes slow and inefficient
19
Q
What does an increase in body size mean?
A
an increase in the distances between the body cells and the exchange surfaces [cite: 244 247]
20
Q
What arose due to the inability of diffusion to transport materials beyond a short distance?
A
a need for a transport system to carry materials rapidly between the material exchange surfaces and the body cells
21
Q
How did large multicellular organisms overcome the limiting factors due to increase in size and complexity?
A
by the development of structures such as gills lungs intestines and leaves (in plants) with large external and internal surfaces for material exchange and a transport system where a fluid carries materials throughout the organism [cite: 249 250]
22
Q
What provides the necessary driving force to keep the fluid moving continuously?
A
Certain mechanisms
23
Q
How do the suspensions and solutes in the fluid flow?
A
at the same speed
24
Q
What is this type of transport system called?
A
a mass flow system
25
What organisms have a mass flow system?
all higher plants and animals
26
Do simple multicellular animals have transport systems?
No
27
Why don't simple multicellular animals have transport systems?
Such animals are small and have a large S.A./V ratio so diffusion is sufficient to meet their needs
28
What do other animals have to bring about transport and distribution of materials?
a mass flow system
29
What are the main materials that are transported in animals?
digested food water and other nutrients oxygen excretory products such as carbon dioxide urea and water and hormones [cite: 256 257 258]
30
In what form are all materials transported within an animal?
an aqueous solution
31
What are transport media?
fluids
32
What acts as transport media in simple animals?
cytoplasm and water
33
What is the main medium of transport in most animals?
blood
34
What are part of blood and play an important role in the transport of materials to the individual body cells?
Intercellular fluid and lymph
35
What is the basic function of a transport system?
to bring about rapid mass flow of materials such as soluble food excretory products and oxygen throughout the body
36
Where must these materials be able to leave the transport system?
At appropriate sites and enter the cells and tissues that either use them or excrete them
37
What must be able to enter the transport system?
materials from various cells and tissues to be carried to their destinations
38
What features does a transport system (also called a circulatory system in most animals) usually have?
a circulating fluid which is usually blood a pumping device or heart to drive the fluid around the body and a system of branched tubes or vessels connected to the heart through which the fluid can circulate [cite: 264 265 266]
39
What are the two types of circulatory systems in animals?
open and closed circulatory systems
40
Where is the open circulatory system found?
in some animals like insects and molluscs
41
What happens in an open circulatory system?
the heart pumps blood out into a blood vessel which branches and opens into spaces in the body cavity called haemocoels The organs and tissues are bathed in blood and exchange of materials occurs between the body cells and the blood Blood in spaces eventually flow into vessels leading to the heart [cite: 268 273 274 275 276]
42
What does the Paramecium use for the distribution of materials within its body?
continuous streaming movements of the cytoplasm [cite: 273 274]
43
What does the Hydra's two-layered body enclose?
a huge gut cavity [cite: 277 278]
44
What circulates materials within the Hydra's gut?
Movements of the gut wall draw water into the gut and cause the digested food and oxygen within it to circulate [cite: 279 280]
45
What does the circulation of materials enable the cells lining the gut to do?
absorb the materials
46
What do some cells in the gut have to circulate the materials?
flagella [cite: 281 282]
47
What are arteries?
Blood vessels leading away from the heart [cite: 283 284]
48
What do arteries branch into?
smaller vessels called arterioles
49
What do arterioles branch into?
fine vessels called capillaries
50
Where are capillaries found?
in between all body cells
51
How does exchange of materials occur between cells and capillaries?
through the walls of the vessels and cell membranes by diffusion
52
What do capillaries unite to form?
venules
53
What do venules join together to form?
veins
54
What are veins?
the blood vessels that transport blood back to the heart
55
How is blood distribution controlled in a closed circulatory system?
well controlled
56
How does blood leave the heart in a closed circulatory system?
at high pressure
57
How does blood return to the heart in a closed circulatory system?
at low pressure
58
What is the body cavity of an insect like the grasshopper called?
haemocoel [cite: 293 294]
59
What does the haemocoel consist of?
a network of blood-filled spaces where the internal organs are immersed in blood
60
Describe the insect heart
a dorsal tubular heart with several chambers which stretch from the thorax into the abdomen and extend towards the head as a single blood vessel the aorta which opens into the haemocoel [cite: 295 296]
61
What does each chamber of the insect heart have?
a pair of slit-like openings at its side with valves that only allow blood to enter the heart [cite: 297 298]
62
What makes the insect heart contract and relax rhythmically?
Muscles attached to the heart chambers [cite: 299 300]
63
What happens when the insect heart contracts?
the slits close and blood is pushed forward into the aorta and out into the haemocoel [cite: 300 301]
64
What happens when the insect heart relaxes?
the slits open and blood that has passed through various parts of the body enters the heart [cite: 301 302]
65
What ensures that blood flows forward towards the head in insects?
Valves between the heart chambers [cite: 302 303]
66
What ensures that blood flows in a definite backward direction in the spaces in the thorax and abdomen of insects?
thin walls partitioning the haemocoel
67
What helps to make the blood flow into the heart in insects?
the movements of the abdominal walls
68
Describe blood movement in an open circulatory system
slow [cite: 304 305]
69
What is the main function of blood in an open circulatory system?
to transport digested food from the gut to body cells and collect wastes from cells to the Malpighian tubules for excretion
70
How is oxygen transported in insects?
by a network of air tubes
71
Why is insect blood colorless?
because it does not contain haemoglobin
72
Is the open circulatory system efficient?
No
73
Why is the open circulatory system adequate for insects?
because they have a well-developed system of air tubes for transporting oxygen to all parts of their body
74
What type of circulatory system do vertebrates have?
closed circulatory systems
75
Describe the vertebrate heart
a well-defined muscular heart lying ventrally in the body
76
What do arteries and veins do in vertebrates?
Arteries carry blood away from the heart and veins bring blood back to the heart
77
What does the closed circulatory system show?
distinct modifications as the vertebrates evolved from fishes to mammals
78
How is the fish heart divided?
into two main chambers an atrium and a ventricle [cite: 311 312]
79
Where does blood from the general body circulation enter in a fish?
the atrium
80
Where does blood go after the atrium in a fish?
the ventricle
81
How does the ventricle compare to the atrium in a fish?
it is more muscular [cite: 312 313]
82
What happens when the ventricle contracts in a fish?
it forces blood out into the aorta at high pressure [cite: 313 314]
83
What prevents backflow of blood in a fish?
Valves guard the opening between the atrium and the ventricle and the ventricle and the aorta
84
What propels blood towards the gills in a fish?
the elastic walls of the aorta [cite: 315 316]
85
What do the aorta branch into at the gills?
arterioles and capillaries
86
What occurs at the gills?
Gaseous exchange oxygen enters the blood from the surroundings while carbon dioxide leaves the blood and diffuses into the surroundings [cite: 316 317]
87
Where does oxygenated blood go after leaving the gills in a fish?
in arteries which branch out to all parts of the body [cite: 317 318]
88
What do arteries form at organs and tissues in a fish?
a network of capillaries [cite: 318 319]
89
What diffuses into and out of body cells at the capillaries in a fish?
Oxygen and digested food diffuse into the body cells while waste materials diffuse out of them [cite: 319 320]
90
What do capillaries rejoin to form in a fish?
veins
91
Where do veins return blood in a fish?
back to the heart [cite: 320 321]
92
How many times does blood pass through the heart in one complete circuit in a fish?
once [cite: 321 322]
93
What is this type of circulation in a fish known as?
single circulation
94
Is single circulation efficient?
No
95
Where do arteries form capillary networks in a fish?
at the gills and again at the various organs and tissues [cite: 323 324]
96
What happens to blood pressure each time blood passes through capillary networks?
it decreases
97
How does blood move in veins in a fish?
sluggishly at low pressure [cite: 324 325]
98
What helps blood flow in veins leading to the heart in a fish?
valves are present in veins and some veins are replaced by blood spaces [cite: 325 326]
99
What does sluggish blood movement tend to do to fish?
slow down their activities [cite: 326 327]
100
What circulatory system do higher land vertebrates have?
double circulation
101
What changes occurred in the vertebrate circulatory system during the evolution of higher land vertebrates?
changes in the structure of the heart related to the change from gills to lungs [cite: 327 328]
102
How is the atrium of the heart divided in an amphibian like a frog?
completely into a left chamber and a right chamber with no opening connecting the two sides [cite: 329 330]
103
How is the ventricle divided in a reptile?
partially divided
104
How is the ventricle divided in mammals and birds?
completely partitioned into a left chamber and a right chamber just like the atrium [cite: 331 332]
105
How many chambers does the heart have in mammals and birds?
four-chambered
106
Where is deoxygenated blood pumped from the heart in land vertebrates?
to the lungs where gaseous exchange occurs [cite: 332 333]
107
Where is oxygenated blood from the lungs returned in land vertebrates?
to the heart from where it is pumped to the other organs and tissues of the body [cite: 333 334]
108
What happens to oxygen in the body of land vertebrates?
it is used up and the deoxygenated blood is then returned to the heart before it is sent to the lungs [cite: 335 336]
109
How many times does blood pass through the heart in one complete circuit through the body of land vertebrates?
twice [cite: 337 338]
110
What is this circulation known as in land vertebrates?
double circulation [cite: 338 339]
111
What is the blood circulation from the heart to the lungs and back to the heart known as?
the pulmonary circulation [cite: 339 340 341 342]
112
What is the circulation from the heart to all other parts of the body and back to the heart known as?
the systemic circulation [cite: 341 342 343]
113
How many capillary networks does blood go through in each circulation?
only one [cite: 343 344]
114
How is blood pressure maintained in double circulation?
at a high pressure
115
What is the result of high blood pressure in double circulation?
efficient and rapid transport [cite: 344 345]
116
Where does oxygenated blood flow in mammals?
always through the left side of the heart [cite: 386 387]
117
Where does deoxygenated blood flow in mammals?
always through the right side of the heart [cite: 387 388]
118
Is blood completely separated in the frog’s ventricle?
No [cite: 588 589]
119
What is the result of the incomplete separation of oxygenated and deoxygenated blood in the frog's ventricle?
there is a tendency for them to mix [cite: 389 390]
120
What structures help to keep oxygenated and deoxygenated blood separate and channel them to the correct circulations in the frog?
ridges and valves [cite: 390 391]
121
What kind of circulation does the frog exhibit?
a partial double circulation [cite: 345 346]
122
Why is the frog’s circulation called partial double circulation?
because the oxygenated and deoxygenated blood are not completely separated as in mammals [cite: 346 347]
123
Describe the efficiency of the mammalian transport system
rapid and efficient [cite: 348 349]
124
What are the main features of the mammalian transport system?
blood lymph and intercellular fluid a muscular four-chambered heart arteries veins and capillaries and a double circulation [cite: 348 349]
125
What does blood consist of?
liquid plasma in which float a mixture of blood cells [cite: 350 351]
126
Describe plasma
a pale yellow liquid made up mainly of water with many dissolved substances including plasma proteins antibodies hormones enzymes gases salts digested food materials and waste materials [cite: 351 352 353]
127
What is the main function of plasma?
to transport the substances that are dissolved in it as well as the cells that float in it [cite: 353 354]
128
What are the blood cells made up of?
red blood cells or erythrocytes white blood cells or leucocytes and platelets
129
How many red blood cells are in one cubic millimeter of blood?
about five million [cite: 355 356]
130
Describe red blood cells
flat and circular with a depression on each side and no nucleus in a mature cell surrounded by an elastic membrane [cite: 356 357]
131
What does the elastic membrane of a red blood cell enable it to do?
squeeze through narrow capillaries whose internal diameters are smaller than its own [cite: 357 358]
132
What is the inside of a red blood cell completely filled with?
the oxygen-carrying pigment haemoglobin [cite: 358 359]
133
What does haemoglobin give to a clump of red blood cells?
its characteristic red colour although each cell looks yellow when viewed singly
134
What is the lifespan of red blood cells?
about three months [cite: 360 361]
135
Where are new red blood cells formed?
in the red marrow of most bones in adults [cite: 361 362]
136
What happens to worn-out red blood cells?
they are ingested by phagocytes in the spleen and broken down to bilirubin and ferritin [cite: 362 363]
137
What does the liver do with ferritin and bilirubin?
stores the iron in ferritin for new red blood cell production and gets rid of the bilirubin via the bile [cite: 363 364]
138
What is the main function of red blood cells?
to transport oxygen from the lungs to the body cells
139
What adaptations do red blood cells have for their function?
their shape gives them a high S.A./V ratio for absorbing large amounts of oxygen and they contain haemoglobin which has a high affinity for oxygen [cite: 365 366]
140
How many white blood cells are in one cubic millimeter of blood?
about 7000 [cite: 367 368]
141
How do white blood cells compare to red blood cells?
they are much larger and are nucleated
142
Where are white blood cells formed?
in some lymph nodes and in bone marrow [cite: 368 369]
143
What is the lifespan of most white blood cells in the bloodstream?
only a few days [cite: 369 370]
144
What are the two main groups of white blood cells?
granulocytes and agranulocytes [cite: 370 371]
145
Describe granulocytes
white blood cells with a granular cytoplasm and a lobed nucleus [cite: 370 371]
146
Describe agranulocytes
white blood cells with a clear cytoplasm and an oval or bean-shaped nucleus [cite: 371 372]
147
What movement do most white blood cells exhibit?
amoeboid movement allowing them to squeeze between cells in capillary walls and enter intercellular spaces [cite: 372 373]
148
What is the function of white blood cells?
to help defend the body against diseases
149
Describe platelets
tiny irregular cell fragments which are non-nucleated [cite: 373 374]
150
How many platelets are in one cubic millimeter of blood?
about 250 000
151
Where are platelets formed?
in large bone marrow cells [cite: 374 375]
152
What do platelets produce?
an important factor which initiates the blood clotting process
153
What are the two important functions of blood in mammals?
It is the transport medium carrying various substances and it protects the body against disease-causing micro-organisms [cite: 376 377 378]
154
What do red blood cells transport?
oxygen from the lungs to all the cells in the body [cite: 378 379]
155
What does haemoglobin do?
It has a high affinity for oxygen and combines with it to form oxyhaemoglobin [cite: 379 380]
156
Describe oxyhaemoglobin
an unstable compound which gives blood a bright red colour [cite: 380 381]
157
When does the reaction between haemoglobin and oxygen occur readily?
when blood flows through regions where the oxygen concentration is high as in the capillaries of the lungs [cite: 381 382]
158
How is oxygen transported to body cells?
in the form of oxyhaemoglobin [cite: 382 383]
159
When does oxyhaemoglobin break down to liberate oxygen?
when blood flows through capillaries surrounding the body cells where the oxygen concentration is low [cite: 383 384]
160
What color is deoxygenated blood?
dark red
161
What does the oxygen-dissociation curve show?
the behavior of haemoglobin at varying oxygen concentrations [cite: 384 385]
162
What is carbon dioxide?
a metabolic waste constantly produced by all the body cells as they respire [cite: 385 386]
163
How is carbon dioxide transported?
It diffuses out of the cells into blood which transports it to the lungs for excretion [cite: 386 387]
164
What happens to most of the carbon dioxide?
it enters the red blood cells reacts with water and is rapidly converted to carbonic acid which dissociates to form hydrogen ions and hydrogencarbonate ions [cite: 387 388]
165
What do hydrogen ions combine with?
haemoglobin
166
What does haemoglobin act as?
a buffer to maintain the acid-base balance in the cell [cite: 388 389]
167
Where do hydrogencarbonate ions diffuse?
out of the red blood cells into the plasma
168
How are hydrogencarbonate ions transported?
in the plasma to the lungs [cite: 389 390]
169
What ions move from the plasma into the red blood cells?
chloride ions [cite: 390 391]
170
Why do chloride ions move into red blood cells?
to maintain ionic concentrations and replace the hydrogencarbonate ions that diffused out [cite: 390 391]
171
What does some carbon dioxide combine with to form carbamino-haemoglobin?
haemoglobin
172
How is carbamino-haemoglobin transported?
to the lungs [cite: 391 392]
173
What happens to a very small amount of carbon dioxide?
it does not enter the red blood cells and forms hydrogen ions and hydrogencarbonate ions [cite: 392 393]
174
What buffers the hydrogen ions formed in the plasma?
the plasma proteins
175
What happens to hydrogencarbonate ions and carbamino-haemoglobin in the lungs?
they break down to release carbon dioxide [cite: 393 394]
176
What speeds up the release of carbon dioxide in the lungs?
the high oxygen concentration in the lungs and the formation of oxyhaemoglobin [cite: 394 395]
177
How is urea transported?
as a solution in the plasma from the liver to the kidneys where it is excreted [cite: 395 396]
178
How are digested soluble foods transported?
from the small intestine to the liver in the plasma [cite: 396 397]
179
What does the liver do with the digested food?
releases the required amount into the blood for distribution to all parts of the body [cite: 397 398]
180
How are hormones transported?
by the plasma from the glands that produce them to the target organs where they bring about their effects [cite: 398 399]
181
How does blood help with temperature control?
it distributes heat uniformly and regulates body temperature by getting rid of excess heat through the skin or reducing heat loss [cite: 399 400 401]
182
How does blood protect the body?
from foreign agents and proteins such as disease-causing micro-organisms in three ways
183
What do phagocytes do?
ingest and destroy harmful micro-organisms and remove broken-down dead tissues [cite: 402 403 404]
184
What happens to some white blood cells during phagocytosis?
they are killed forming pus around wounds [cite: 405 406]
185
What do lymphocytes produce?
antibodies [cite: 406 407]
186
How do antibodies destroy micro-organisms?
by causing them to clump together or dissolving their outer coats [cite: 407 408]
187
What do some micro-organisms produce and what neutralizes them?
toxins which are neutralized by anti-toxins [cite: 408 409]
188
What do antibodies and anti-toxins provide?
immunity against diseases [cite: 409 410]
189
What constitutes the body's immune system?
white blood cells that produce protective substances [cite: 410 411]
190
What does the AIDS virus do?
attacks and destroys certain white blood cells in the immune system [cite: 411 412]
191
What is the result of AIDS?
the infected person is left without a defence when disease-causing microorganisms invade his body and suffers from all kinds of microbial infections which cause death [cite: 412 413]
192
What do arterioles branching from arteries divide into?
capillaries with one-cell thick walls [cite: 414 415]
193
What is the blood pressure like in capillaries at the arteriole end?
high [cite: 415 416]
194
What does high capillary blood pressure cause?
plasma most dissolved substances and some white blood cells to filter out into intercellular spaces [cite: 416 417]
195
What cannot filter through capillary walls?
plasma proteins and erythrocytes [cite: 417 418]
196
What is intercellular or tissue fluid?
plasma that filters out and occupies the spaces between the cells [cite: 418 419]
197
What does intercellular fluid contain?
water dissolved oxygen dissolved food and hormones [cite: 419 420]
198
How are materials transported between blood and cells?
via the intercellular fluid [cite: 419 420 421]
199
What role does intercellular fluid play?
a middleman in the transport and exchange of materials between the blood and the cells
200
How is intercellular fluid returned to the blood?
in two ways [cite: 421 422]
201
Describe the first way intercellular fluid is returned to the blood
blood in capillaries at the venule end is highly concentrated with mainly plasma proteins and little water while intercellular fluid near venules is a weak solution so some intercellular fluid is absorbed into the blood in the capillaries [cite: 422 423]
202
Describe the second way intercellular fluid is returned to the blood
unabsorbed intercellular fluid passes into blindly ending lymphatic vessels near the capillaries becoming lymph which flows through fine lymphatic vessels joining to form large vessels that empty into veins in the neck region [cite: 423 424]
203
What fluids are in continuous circulation in the body?
intercellular fluid lymph and blood [cite: 425 426]
204
What makes lymph flow along lymphatic vessels?
movements of the body muscles [cite: 426 427]
205
What prevents backflow of lymph?
valves in the lymphatic vessels
206
What are lymph nodes?
bean-shaped structures along the lymphatic vessels that produce white blood cells filter out micro-organisms foreign particles and cell fragments and engulf them with phagocytes [cite: 427 428]
207
Describe the human heart
a conical hollow muscular organ that works continuously throughout the life of a person is about the size of a clenched fist and weighs about 300 grams [cite: 429 430]
208
Where is the heart located?
in the chest just behind the breastbone and between the two lungs [cite: 431 432]
209
What is the heart enveloped in?
a two-layered tough membranous bag the pericardium
210
What is between the two layers of the pericardium?
fluid [cite: 432 433]
211
What does the fluid between the pericardium layers do?
reduces the friction caused by the pumping movements of the heart between the heart wall and the surrounding tissues [cite: 433 434]
212
How often does the average human heart contract and relax at rest?
about 70 times per minute
213
How much blood does the average human heart pump per day at rest?
about 14 000 litres
214
What happens to the heart rate during exercise?
it goes up to over 100
215
What does increased heart rate during exercise do?
increases the supply of oxygen and food to the body cells [cite: 435 436]
216
What is the heart wall made of?
a special muscle the cardiac muscle found only in the heart [cite: 436 437]
217
Describe cardiac muscle
contracts and relaxes rhythmically and can work continuously without becoming tired like the skeletal muscles [cite: 437 438]
218
What does cardiac muscle need to work hard and continuously?
a good supply of blood to provide oxygen and nutrients and remove its wastes [cite: 438 439]
219
What supplies the heart muscle with blood?
coronary arteries and veins which spread all over the heart wall [cite: 439 440]
220
What are the chambers of the heart?
two upper thin-walled atria or auricles and two lower thick-walled ventricles [cite: 440 441]
221
What separates the right and left sides of the heart?
a wall called the septum [cite: 441 442]
222
What veins open into the right auricle?
two large veins the superior (anterior) and inferior (posterior) venae cavae bringing dark red deoxygenated blood from the various parts of the body (except the lungs) [cite: 442 443]
223
What veins open into the left auricle?
pulmonary veins bringing bright red oxygenated blood from the lungs [cite: 443 444]
224
What controls the openings of the veins into the auricles?
rings of muscles found in the vein [cite: 444 445]
225
What do the muscles controlling the openings of the veins into the auricles do when they contract and relax?
contraction closes the openings while relaxation opens them [cite: 445 446]
226
What guards the opening between the right auricle and the right ventricle?
the tricuspid valve [cite: 446 447]
227
Describe the tricuspid valve
has three flaps attached by cord-like tendons (chordae tendinae) to the walls of the right ventricle [cite: 446 447]
228
What do the chordae tendinae do?
only allow the flaps to open outwards into the ventricle allowing unidirectional blood flow from the auricle into the ventricle [cite: 447 448]
229
What guards the opening of the left auricle into the left ventricle?
the bicuspid or mitral valve [cite: 448 449]
230
How is the bicuspid or mitral valve similar to the tricuspid valve?
structurally and functionally except that it has two flaps instead of three [cite: 449 450]
231
What does the right ventricle open out into?
the pulmonary artery which branches into two one leading to the right lung and the other to the left lung [cite: 450 451]
232
What do the branches of the pulmonary artery carry?
deoxygenated blood to the lungs [cite: 451 452]
233
What does the left ventricle open into?
the large aorta which branches to distribute oxygenated blood to all parts of the body except the lungs [cite: 451 452]
234
What prevents backflow of blood from the arteries into the ventricles?
Semi-lunar valves in these arteries [cite: 453 454]
235
How does the thickness of the left ventricle wall compare to that of the right ventricle?
it is at least three times thicker [cite: 454 455]
236
Why is the left ventricle wall thicker?
because its contraction must send blood round the much longer systemic circulation while the right ventricle only needs to send blood round the shorter pulmonary circulation [cite: 455 456]
237
What is the blood pressure of blood entering the aorta and pulmonary artery?
about 105 mmHg in the aorta and about 16 mmHg in the pulmonary artery [cite: 456 457]
238
What happens during diastole?
Veins and auricles contract forcing blood into relaxed ventricles semi-lunar valves close and cuspid valves open [cite: 457 458]
239
What happens during systole?
Ventricles contract forcing blood into aorta and pulmonary artery Backflow of blood into the auricles is prevented by the closing of the cuspid valves which we hear as a loud lub sound Blood from the ventricles enters the arteries After fully contracting the ventricles start to relax The blood in the arteries tend to flow back into the ventricles This is prevented by the closing of the semi-lunar valves which we hear as a soft dub sound [cite: 458 459 460 461]
240
What is one heartbeat?
one contraction (systole) and one relaxation (diastole) of the ventricles and lasts for about 0.8 second [cite: 461 462 463]
241
What happens to the heart chambers during diastole?
they especially the ventricles relax or rest [cite: 462 463]
242
What happens to the heart chambers during systole?
they especially the ventricles contract [cite: 463 464]
243
What happens when the ventricles contract?
they force blood into the arteries at high pressure causing the elastic walls of the arteries to dilate suddenly [cite: 464 465 466]
