Cardio Flashcards
(220 cards)
1
Q
Describe the composition of blood.
A
Plasma - 55%.
Cellular - 45% - RBC: 44%, WBC: 1%.
2
Q
What is Haematocrit?
A
the volume of red blood cells i.e haemoglobin in the blood, normal
haematocrit is 0.45
3
Q
What is Haemopoeisis?
A
the process of the production of blood cells and platelets which
continues throughout life
4
Q
What is the lifespan of an erythrocyte?
A
120 days
5
Q
What is the lifespan of a platelet
A
7-10 days
6
Q
What is the lifespan of a white blood cell
A
6 hours
7
Q
Where are the precursor cells of erythrocytes located?
A
Bone marrow
8
Q
Where can haemopoiesis occur in
a) Adults
b) Children
c) in Utero
A
a) axial skeleton - skull, ribs, spine, pelvis and long bones
b) all bones
c) yolk sac, then liver and spleen
9
Q
What hormone is required for erythropoiesis and where is it produced?
A
Erythropoietin - produced in the kidney
10
Q
What hormone is required for white blood cell production?
A
G-CSF - (granulocyte colony-stimulating factor)
Thrombopoietin
11
Q
What hormone is required for platelet formation?
A
Thrombopoietin
12
Q
What causes the oxygen dissociation curve to shift to the left
A
Decreased temp
increased pH
13
Q
What causes the oxygen dissociation curve to shift to the right
A
Increased temp
decreased pH
14
Q
What happens when the oxygen dissociation curve shifts to the left
A
Hb has a higher affinity for oxygen - (left locks oxygen)
at lower partial pressures of oxygen
decreased unloading
15
Q
What happens when the oxygen dissociation curve shifts to the right
A
Hb has a lower affinity for oxygen
Increased unloading to tissues
16
Q
What are reticulocytes
A
Young (immature) red blood cells
17
Q
Briefly describe the structure of Hb
A
2 alpha and 2 beta chains
4 haem groups
has a quaternary structure
18
Q
Which of the ABO blood groups is recessive?
A
O, A and B are co-dominant.
19
Q
Which blood group do people have that make them universal recipients?
A
AB - have neither anti-A or anti-B antibodies
20
Q
Which blood groups do people have to make them universal donors?
A
Type O - have both anti-A and anti-B antibodies, but don’t have any ANTIGENS on the surface of RBC
21
Q
What are the two ways of determining someone’s ABO blood group?
A
- Test using antibodies.
2. Test for the presence of antibodies against A or B antigens.
22
Q
Describe how testing for the presence of antibodies against A or B antigens will determine someone’s blood group?
A
The presence of antibodies in the blood will indicate that this person does not have these antigens on their RBC’s. For example, if a persons blood is found to contain antibodies against the B antigen then they can’t be of the AB or B blood groups.
23
Q
What antigens are part of the Rhesus blood group system?
A
C, D and E.
D is the most important
24
Q
What problems can arise if a pregnant lady is found to be rhesus D negative?
A
- Mother RhD negative/ baby RhD positive
- mothers blood exposed to babies blood
- mother sensitised / production of anti-D antibodies
- First baby unaffected
- second baby has RhD positive blood
- antibodies cross placenta and destroys RBC of baby
- can lead to Rh disease and anaemia/jaundice
25
What can be given to rhesus D negative mothers to prevent sensitisation?
Anti-D.
26
Define anaemia
reduction in haemoglobin in the blood
27
What do you call an increased level of Hb and causes?
polycythaemia (caused by smoking, lung diseases, inefficient lungs
meaning less O2 is exchanged so more haemoglobin is required etc.)
28
Why might iron deficiency cause iron-deficiency anaemia?
Iron is needed for haemoglobin production, lack of
| iron results in the reduced production of small red cells
29
Why might vitamin B12 and folate deficiency lead to anaemia?
- required for DNA synthesis
| - RBC cannot be made in bone marrow
30
Where is folate found?
Vegetables and fruit
31
what is Haemolysis?
Normal or increased cell production but DECREASED LIFE SPAN < 30 DAYS, red
blood cells are destroyed before their 120 day lifespan
32
What is the lifespan of neutrophils?
10 hours
33
What is the most numerous WBC in the body?
Neutrophils
34
What is the role of neutrophils?
- Phagocytose and kill bacteria
| - release cytokines (important in inflammatory response)
35
Where are platelets made and what are they derived from?
Made in the bone marrow and derived from the megakaryocytes
36
What is the lifespan of platelets?
5-10 days
37
What term is used to describe reduced platelet count?
thrombocytopenia (main risk is cerebral bleeding) > 80 =
| increased bleeding, > 20 = spontaneous bleeding
38
What term is used to describe elevated platelet count?
thrombocytosis, can lead to arterial & venous thrombosis, leading
to an increased risk of heart attack + stroke
39
Where are coagulation proteins/enzymes made from and what is needed to make them?
- Produced in the liver
- The key enzyme is thrombin
- Vitamin K is needed for coagulation factors 2,7,9 and 10
- circulate in an inactive form
40
Why might someone with liver injury experience prolonged bleeding time?
Because the liver produces clotting factors.
41
Give 3 functions of Thrombin.
1. Converts fibrinogen into fibrin.
2. Activates factor XIII into XIIIa.
3. Has a positive feedback effect resulting in further thrombin production.
42
In haemostasis what is prothrombin converted into?
Thrombin.
43
why is blood stay as a fluid in blood vessels?
-The proteins of the coagulation cascade and the platelets circulate in an inactive
state
-Proteins and platelets are only activated by tissue factor, which is present on every
single-cell APART from endothelial cells thus when the endothelium is punctured etc.
blood comes into contact with tissue factor and thus starts clotting
44
What is the coagualtion cascade?
Results in the beginning of the coagulation cascade - series of proteolytic enzymes
that circulate in an inactive state being activated (usually by exposure to tissue
factor) in a cascade or waterfall sequence - in order to generate the key enzyme
THROMBIN which cleaves fibrinogen creating fibrin polymerisation i.e a blood
clot
45
Why might obstructive jaundice cause a prolonged bleeding time?
Malabsorption of vitamin K as it is a fat soluble vitamin
| Vitamin K is needed to produce clotting factors
46
When a blood vessels is damaged what is the first response?
- Vasoconstriction due to neural control and release of endothelin-1
- slows the blood flow in the area
47
What is exposed when the endothelium is injured
Collagen fibres and the attached VWF.
48
Which receptor do the platelets use to bind to the VWF on the collagen fibres?
glycoprotein 1b receptor
49
What do the platelets release when they bind to the collagen fibres via the VWF?
Platelet dense granules via exocytosis
50
What is released from the platelet dense granules and what do they act on?
- ADP released
- act on P2Y1 and P2Y12
- causes platelet activation
51
Which receptors does thrombin bind to and what does this cause?
- Binds to PAR1 and Par2 receptors
- Platelet activation
- further thrombin release (positive feedback)
52
What happens in platelet activation?
- Increased expression of GP2b/3a receptors
- they bind to fibrinogen from alpha granules enabling new platelets to adhere to old ones
- from smooth to spiculated with pseudopodia which increases SA
53
What do activated platelets synthesise and what does this lead to ?
- Thromboxane A2
- vasoconstriction
- platelet activation
further stimulate release of vesicle contents of other platelets
- platelet aggregation
54
What is present in high concentration in platelets which aim to strengthen and compress the platelet plug?
actin and myosin
55
What does an undamaged endothelium release in order to prevent platelet activation in undamaged areas?
- Prostacyclin (inhibits platelet aggregation) and - - - NO (inhibits platelet adhesion).
- both vasodilators
56
What is the role of vWF?
vWF binds to collagen and platelets bind to vWF via GP 1b receptor
57
What is the essential component of a blood clot?
fibrin
58
Briefly describe the Fibrinolytic system.
Plasminogen is converted into plasmin. Plasmin cuts the fibrin at various places leading to the formation of fragments.
59
What is the purpose of the fibrinolytic system?
It acts to prevent blood clots from growing and becoming problematic.
60
What is contained within alpha granules of the platelets?
- VWF
- Thromboxane A2
- Fibrinogen
- fibrin stabilising factor
61
What is contained within dense granules of the platelets?
- ADP
- Ca2+
- Serotonin
62
What is found within the intercalated disks of cardiac muscle?
- Desmosomes
| - Gap junctions
63
Describe myosin (thick filament).
2 heavy polypeptide chains and 4 light chains. The myosin heads have 2 binding sites; one for actin and one for ATP.
64
Describe actin (thin filament).
A globular protein, single polypeptide. It polymerises with other actin monomers to form a double stranded helix. Together they form F actin.
65
Describe tropomyosin and its position
elongated molecule that occupies the grooves between the two actin
strands, overlies MYOSIN binding sites on actin
66
What is the function of troponin I?
Troponin I, together with tropomyosin, inhibits actin and myosin binding.
67
What is the function of troponin T?
Troponin T binds to tropomyosin.
68
What is the function of troponin C?
Troponin C has a high affinity for Ca2+. TnC drives away TnI and so allows cross bridge formation.
69
What effect does myocardial contraction have on the I-band and H-zone of a sarcomere?
They get shorter.
70
What effect does myocardial contraction have on the A-band of a sarcomere?
No effect, it stays the same length
71
What is in the A-band?
occupied by thick filaments and a few thin filaments
72
What is in the I - band?
- only thin filaments
| - extends from the z-lines
73
What is in the H-zone?
only thick filaments (myosin)
74
What is titin and what is its function in a sarcomere?
- elastic protein filaments
- extends from Z-line to M-line
- titin linked to M-line though myosin
- maintains alignment of the thick filaments of each sarcomere
75
What is the sarcoplasmic reticulum?
membrane network that surrounds the contractile
| proteins. Releases Ca2+ when Ca2+ binds to it ryanodine receptor
76
Describe excitation-contraction coupling.
1. Na+ depolarises membrane.
2. A small amount of Ca2+ is released from T tubules.
3. Ca2+ channels in sarcoplasmic reticulum open.
4. Ca2+ flows into cytosol. Cytosolic Ca2+ conc raised.
5. Ca2+ binds to troponin C, this pulls tropomyosin and exposes the myosin binding site on actin.
6. Cross bridge cycling begins.
7. After depolarisation, Ca2+ is returned to SR. K+ outflow = repolarisation.
77
When an action potential arrives sodium channels open, which other channel starts to open slowly at this stage?
L-type Ca2+ channels
78
What occurs at phase 0 of an action potential?
- rapid depolarisation
- Na+ channels open and L-type Ca2+ channels start to open
- Rapid Na+ inflow
79
What occurs at phase 1 of an action potential?
- Partial repolarisation
- Na+ channels close
- voltage gated K+ channels open
- outflow of K+
80
What occurs at phase 2 of an action potential?
- Plateau
- Calcium slow inflow
- matched by potassium outflow
81
What occurs at phase 3 of an action potential?
- repolarisation
L-type calcium channels close
- Ca2+ inflow stops
- K+ outflow remains
82
What occurs at phase 4 of an action potential?
- Pacemaker potential
- Na+ inflow
- Slowing of potassium outflow
- Na+/K+ ATPase
3Na+ out and 2K+ in
83
What is the function of the refractory period?
1. It prevents excessively frequent contractions.
| 2. It allows time for the atria to fill.
84
What 2 channels are closed during the refractory period in a cardiac action potential?
Fast Na+ and Ca2+ channels.
85
Which group of arteries supplies the myocardial cells?
Coronary arteries
86
Which vein do the coronary arteries drain into and where does the vein empty?
- Coronary sinus
| - Drains in the right atrium
87
Why is the O2 saturation in coronary venous blood very low?
O2 extraction by the heart muscle is very high.
88
Where is the coronary sinus found?
Between the LA and LV - left atrio-ventricular sulcus.
89
Where is the SAN located?
In the RA under the crista terminalis.
90
What is the resting potential of the SA node?
- 55 to -66mv
- closer to threshold of depolarisation
- hence depolarises first
91
Name the three ion channels that contribute to the pacemaker potential and briefly explain their role
- K+ channel - Channels that opened during the repolarisation phase of previous action potential gradually close due to return of negative potential
- F-type Na+ channels - funny as they open at negative potentials
- T- type Ca2+ channels - open briefly important in final depolarisation push
92
Where is the AV node located?
at the base of the right atrium
93
Briefly describe the electrical conduction pathway in the heart.
1. The SAN generates an electrical impulse.
2. This generates a wave of contraction in the atria.
3. Impulse reaches AVN.
4. There is a brief delay to ensure the atria have fully emptied.
5. The impulse then rapidly spreads down the Bundle of His and Purkinje fibres.
6. The purkinje fibres then trigger coordinated ventricular contraction.
94
Briefly describe the cardiac action potential in 5 steps.
1. Na+ channels open; influx of Na+ into cell; depolarisation.
2. When the Na+ channels close, a small number of K+ leave the cell resulting in partial repolarisation.
3. Ca2+ channels open and there is Ca2+ inflow. K+ channels are also open and there is K+ outflow. This results in the plateau period.
4. Ca2+ channels close and K+ channels remain open. K+ leaves the cell resulting in repolarisation.
5. Maintaining the resting potential (approx -90mV). Na+ inflow, K+ outflow.
95
Which nerve supplies parasympathetic innervation to the heart?
Vagus nerve ( CN10)
96
Which neurotransmitter is released from the vagus nerve and what type of receptor does it bind to?
- Ach
| - Muscarinic receptor
97
What affect does parasympathetic innervation have on the heart?
- Decreases heart rate (negatively chronotropic)
• Decreases force of contraction (negatively inotropic)
• Decreases cardiac output (by up to 50%)
• Decreased parasympathetic stimulation will result in an increased heart rate
98
Which nerves provide sympathetic innervation to the heart and which neurotransmitter is used?
- Sympathetic postganglionic fibres
| - adrenaline & noradrenaline
99
What affect does sympathetic innervation have on the heart?
• Increases heart rate (positively chronotropic)
• Increases force of contraction (positively inotropic)
• Increases cardiac output (by up to 200%)
• Decreased sympathetic stimulation will result in decreased heart rate & force of
contraction and a decrease in cardiac output by up to 30%
100
What does the P wave on an ECG represent and duration?
- Atrial depolarisation
| - duration lasts between 0.08- 0.01s
101
What does the QRS complex show on an ECG and duration?
- Ventricular depolarisation
| - 0.06-0.1 s
102
What does the T wave on an ECG represent?
Ventricular repolarisation.
103
ECG: where would you place lead 1?
Right arm (-ve) to left arm (+ve).
104
ECG: where would you place lead 2?
Right arm (-ve) to left leg (+ve).
105
ECG: where would you place lead 3?
Left arm (-ve) to left leg (+ve).
106
ECG: where would you place lead aVR?
Left arm and left leg (-ve) to right arm (+ve).
107
ECG: where would you place lead aVF?
Right arm and left arm (-ve) to left leg (+ve).
108
ECG: where would you place lead aVL?
Right arm and left leg (-ve) to left arm (+ve).
109
ECG chest leads: In which intercostal space would you place V1 and V2?
The 4th intercostal space. V1 is right of the sternum and V2 in left.
110
ECG chest leads: In which intercostal space would you place V3-V6.
The 5th intercostal space. V3 is left of the sternum, V4 is in the mid-clavicular line, V5 is left of V4 and V6 is under the left arm.
111
ECG: Name the leads that correspond to the lateral surface of the heart
- Lead 1
- aVL
- V5
- V6
112
ECG: Name the leads that correspond to the septum on the heart
- V1
113
ECG: Name the leads that correspond to the anterior surface of the heart
- V2
- V3
- V4
114
ECG: Name the leads that correspond to the inferior surface of the heart
- Lead 2
- Lead 3
- aVF
115
atrial depolarisation is seen in every lead apart from one, which one?
- aVR
116
describe the PR interval
Time taken for atria to depolarise and electrical activation to get
through AV node
117
Describe the ST segment
- interval between depolarisation & repolarisation
118
Is there a point in the cardiac cycle when both atrial and ventricular diastole occur together?
Yes: when the ventricles are relaxing and the atria are filling (before atrial contraction).
119
What ECG lead yields complexes that are normally inverted compared to the anterior and inferior leads?
Lead aVR.
120
How long is the AV node delay?
0.12-0.2 seconds
121
State how long diastole and systole last for
Systole: 0.3 seconds
Diastole: 0.5 seconds
122
Describe the events that occur in systole
- Wave of depolarisation arrives, Ca2+ channels open
- LVp>LAp and the mitral valve closes.
- isovolumic contraction
- all valves are closed at this point
- LVp > aortic/pulmonary pressure
- valves open, maximal ejection
- Ventricles do not completely empty
123
Describe the events of diastole
- LVp decreases and there is a phase of reduced ejection
- LVp is less than aortic pressure and the aortic valve closes
- isovolumetric ventricular relaxation
- LAp >LVp due to venous return
- Mitral valve opens
- 80% ventricular filling ( passive)
- atrial booster/ atria contract and ventricles filled
- LVp > LAp and mitral valve closes.
124
What causes the mitral valve to close?
When LVp exceeds LAp. Just before ventricular isovolumetric contraction.
125
What is isovolumetric contraction?
Ventricular contraction when all valves are closed. This increases ventricular pressure but as the valves are closed the volume remains unchanged.
126
What produces the first heart sound?
Closing of the mitral valve.
127
What produces the second heart sound?
Closing of the aortic valve.
128
What is end-systolic volume?
The volume of blood remaining in the LV following systole.
129
Define preload.
- The volume of blood in the ventricles just before contraction (EDV).
- stretches myocytes
- dilating veins increases preload
130
Define afterload.
- The pressure against which the heart must work to eject blood in systole.
- dilate arteries = decreased afterload
131
Define contractility.
The inherent strength and vigour of the heart's contraction during systole.
132
Define elasticity.
Myocardial ability to recover its original shape after systolic stress.
133
Define compliance.
how easily the heart chamber expands when filled with blood volume
134
Define diastolic distensibility.
The pressure required to fill the ventricle to the same diastolic volume.
135
Define resistance.
A force that must be overcome to push blood through the circulatory system.
136
Describe starlings law
Force of contrition is proportional to the end-diastolic length of
cardiac muscle fibre - the more ventricle fills the harder it contracts
137
What is the basic principle of Starling's law of the heart?
Increased EDV = increased SV.
138
With relation to Starling's law, what is the effect of an increased venous return?
- increased EDV
- increased preload
- increased sarcomere stretch
- increased force of contraction
- increased stroke volume and force of contractions
- increased CO (CO= SVxHR)
139
What is myogenic auto-regulation of blood flow?
- An intrinsic mechanism in smooth muscle blood vessels.
- If BP increases the vessel (arteriole) constricts.
- If smooth muscle into getting stretched as low BP the muscles relax in the arteriole
- This is important in
regulating blood flow.
140
Myogenic auto-regulation of blood flow: What is the response to an increase in BP?
Increased BP will result in vasoconstriction and so blood flow decreases.
141
Myogenic auto-regulation of blood flow: What is the response to a decrease in BP?
Decreased BP will result in vasodilation and so blood flow increases.
142
What is hyperaemia?
An increased blood flow to tissues.
143
Give the equation for mean arterial pressure.
MAP = DP + 1/3(SP-DP).
| SP - systolic pressure, DP - diastolic pressure
144
Name 3 effectors in circulation control.
1. Blood vessels - vasoconstrict/dilate and affect TPR.
2. The heart - can affect rate or contractility.
3. Kidneys - regulates blood volume and fluid balance.
145
Which region in the brain is responsible for raising blood pressure?
- Pressor region in medulla
| - sympathetic
146
How does the pressor region in the medulla increase BP?
- increased vasoconstriction
- increased heart rate
- increased stroke volume due to more forceful contractions
- hence increased CO ( CO= SVxHR)
- increased contractility
147
Which region in the brain is responsible for lowering blood pressure?
- Depressor region in the medulla
| - parasympathetic via the vagus nerve
148
How does the depressor region in the medulla lower BP?
- inhibits the pressor region
149
Where are central chemoreceptors located?
In the medulla oblangata.
150
What do central chemoreceptors respond to?
Changes in pH/(H+).
Increased PaCO2 increases H+ and so decreases pH.
Increased PaCO2 results in vasodilation.
151
Where are the cardiopulmonary baroreceptors found?
- Atria
- ventricles
- pulmonary artery
152
What happens when the cardiopulmonary baroreceptors are stimulated
- high blood pressure leads to the inhibition of the pressor region/ vasoconstrictor centre in the medulla - leading to a fall in blood pressure
- decrease in
blood pressure by promoting vasodilation & fluid loss
- Also inhibits the Renin-angiotensin & aldosterone system
- inhibits vasopressin/ADH
153
What are the principal vessels of resistance?
Arterioles.
154
What do arterioles respond to?
Blood pressure changes. Local, neural and hormonal factors.
155
Name 2 local factors that result in vasoconstriction.
- Endothelin
| - internal BP - increase internal BP results in myogenic contraction, diameter normalised
156
Name 5 local factors that result in vasodilation.
Hypoxia, NO, K+ (accumulate from AP), CO2, H+, adenosine.
157
What neural factors result in vasoconstriction?
Sympathetic nerves release noradrenaline.
158
What neural factors result in vasodilation?
Parasympathetic innervation.
159
Name 3 hormonal factors that result in vasoconstriction.
Angiotensin 2, ADH, Adrenaline (binds to alpha-adrenergic receptors in smooth muscle).
160
Name 2 hormonal factors that result in vasodilation.
Atrial natriuretic peptide, Adrenaline (binds to beta2 receptors).
161
What activates baroreceptors?
Baroreceptors contain stretch receptors that respond to pressure.
162
Where are peripheral chemoreceptors found?
- aortic arch & carotid sinus
163
What stimulates the peripheral chemoreceptors
a fall in PaO2 & a rise in
| PaCO2 & a fall in pH causing blood pressure to increase
164
Describe how the aortic arch can work to decrease BP?
- afferent signals sent via the vagus nerve to the medulla
- Decreased sympathetic (pressor) and increased parasympathetic (depressor)
- decrease in blood pressure
165
Describe how the carotid sinus work to decrease BP
- Carotid sinus
- to glossopharyngeal afferent
- to the medulla
- Decreased sympathetic (pressor) and increased parasympathetic (depressor)
- decrease in blood pressure
166
Give the equation for stroke volume.
SV=EDV-ESV.
167
Give the equation for cardiac output.
CO=SVxHR.
168
Define cardiac output.
The volume of blood each ventricle pumps per unit time.
169
Give the equation for pulse pressure.
PP=SP-DP.
170
Give the equation for blood pressure.
BP=COxTPR.
171
What is Poiseuille's equation?
Flow = radius to the power of 4
172
What is Ohm's law?
Flow = Pressure gradient/Resistance
173
Why does an increase in LVEDV signify heart failure?
Heart failure is the inability to pump blood out of the heart. There is blood remaining at the end of systole. The blood therefore accumulates and so LVEDV increases.
174
Which pressure is most likely to increase in left sided heart failure?
LV EDP.
175
Which pressure is most likely to decrease in left sided heart failure?
Mean aortic pressure.
| Less blood is being pumped into the aorta
176
What is stenosis?
Narrowing.
177
Which pressure is most likely to increase in mitral valve stenosis?
Left atrial end-systolic pressure.
178
What does it mean if a heart valve is incompetent?
It is regurgitant.
179
Which pressure is most likely to increase when the aortic valve is incompetent?
Left ventricular end-diastolic pressure.
180
Pulmonary oedema is a sign of what?
Left heart failure.
181
What can severe pulmonary hypertension cause?
Right heart failure.
| The heart has to pump harder to get blood into the pulmonary circulation due to an increased afterload.
182
Shortness of breath, severe peripheral oedema and ascites after a heart attack can indicate what?
Biventricular failure.
183
Diastole: what is diastasis?
When LVp = LAp. Net movement of blood is zero. This is the time between ventricular suction and atrial contraction.
184
Describe the arterial baroreceptor reflex in response to an increase in blood pressure.
- Increased parasympathetic outflow to the heart means contractility and heart rate are reduced and so cardiac output is reduced: CO=HRxSV.
- Decreased sympathetic outflow to the arterioles results in vasodilation and so TPR is reduced.
- BP=COxTPR and so blood pressure is lowered.
185
Describe the arterial baroreceptor reflex in response to a decrease in blood pressure.
- Increased sympathetic outflow to the heart means contractility and heart rate are increased and so cardiac output is increased: CO=HRxSV.
- Increased sympathetic outflow to the arterioles results in vasoconstriction and so TPR is increased.
- BP=COxTPR and so blood pressure is increased.
186
What phase of the cardiac action potential coincides with diastole?
Phase 4.
187
Define ischaemia.
A decrease in blood flow to a tissue.
188
Define infarction.
No blood flow to a tissue - tissue death.
189
Explain the formation of fluid exudate in inflammation.
Chemical mediators cause vasodilation of vessels and an increase in permeability.
190
What are the roles of lymphatics in acute inflammation?
Lymphatics drain exudate and carry antigens.
191
What occurs in gastrulation?
- mass movement of cells to form a trilaminar disk
192
when does gastrulation occur
in the third-week post fertilisation
193
What does the ecotderm devlop into?
- PNS
- CNS
- Sweat glands
- Posterior pituitary
- Skin
- Hair
- Nails
- enamel of teeth
- lens of eyes
- sensory epithelium of nose, ear and eye
194
What does the endoderm form?
- Epithelial lining of the GI tract, respiratory tract and urinary bladder
- parenchyma of the thyroid gland parathyroid and liver and pancreas
- epithelial lining of the tympanic cavity and auditory tube
195
Name the three different components of the mesoderm?
- Paraxial plate mesoderm
- intermediate plate mesoderm
- lateral plate mesoderm
196
What does the paraxial plate mesoderm form?
- Somites which give rise to:
A. Myotome (muscle tissue)
B. Sclerotome (cartilage and bone)
C. Dermatome (dermis of the skin)
197
What does the intermediate plate mesoderm form?
Urogenital system
- gonads and respective duct systems
- kidneys
198
What does the lateral plate mesoderm form?
Two layers
1. Somatic (parietal) layer: forms the future body wall
2. Splanchnic (visceral) layer forms:
- Circulatory system
- Connective tissue for the glands
- Muscle, connective tissue and peritoneal components of the
way of the gut
199
What are the 3 stages of heart formation?
1. Formation of primitive heart tube.
2. Cardiac looping.
3. Cardiac septation.
200
Describe what happens in the formation of the primitive heart tube.
- By day 19 (third week), two endocardial tubes form. These tubes will fuse
to form a single, primitive heart tube
- Day 21: As the embryo undergoes lateral folding, the two endocardial
tubes have fused to form a single heart tube
201
What is formed from the first Heartfield in the cardiogenic region?
Left ventricle
202
What is formed from the second Heartfield in the cardiogenic region?
- Atria
- Smooth outflow tracts
- Right ventricle
203
From which germ layer(s) is the cardiovascular system formed?
- Mesoderm
| - some contribution from cardiac neural crest cells in the ectoderm
204
Name the five bulges that form in the heart tube
- Truncus arteriosus
- bulbus cordis
- primitive ventricle
- primitive atrium
- sinus venosus
205
What forms from the truncus arteriosus?
- ascending aorta
| - pulmonary trunk
206
What forms from the bulbus cordis?
- Smooth outflow tracts of the left and right ventricles
207
What forms from the primitive ventricle?
majority of ventricles
208
What forms from the primitive atrium?
- Both auricular appendages
- Entire L atrium
- anterior part of R atrium
209
What forms from the sinus venosus?
- Smooth part of R atrium
- Coronary sinus
- Vena Cavae
210
from which day does the heart begin to beat
day 22
211
Describe what happens in cardiac looping.
Nodes secrete nodal, this circulates to the left due to ciliary movement. Nodal causes a cascade of transcription factors that transduce looping.
212
Describe what happens in cardiac septation.
Endocardial cushions form. Fuse at mid-line to form atrio-ventricular septum. Muscular ridge in the floor of the primitive ventricle migrates to endocardial cushions forming interventricular septum.
213
What does the 1st aortic arch form?
Maxillary artery
214
What does the 2nd aortic arch form?
Stapedial artery
215
What does the 3rd aortic arch form?
Common carotid arteries/ part of internal carotid
216
What does the 4th aortic arch form
Left - arch of aorta
| right - subclavian
217
What does the 5th aortic arch form?
there is no fifth aortic arch
218
What does the 6th aortic arch form?
Right - pulomonary trunk
| left - ducts arteriosus
219
Briefly describe foetal circulation.
- oxygenated blood from placenta to foetus through umbilical vein
- bypasses the liver - ductus venosus and into IVC
- RAp>LAp blood is shunted through foramen ovale
- most blood moves directly to the aorta via ductus arteriosus
- deoxygenated blood return to placenta via umbilical arteries near the bladder
220
Describe what occurs in postnatal circulation
- first breath vasodialtion of pulmonary vessels
- umbilical vein constricts into ligamentum trees
- umbilical arteries constrict to form medial umbilical ligaments
- 10-15 hours after birth ductus arteriosus constricts to become the ligamentum arteriosum
- foramen ovale closes- fossa ovalis
- ductus venosum constrcits - ligamentum venosum
