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Semester 1 > Heart Histology > Flashcards

Heart Histology Flashcards

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0
Q

Which two layers make up the pericardium?

A

Visceral (inner pericardium)

Parietal (outer pericardium)

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1
Q

What is the function of the endomysium?

A

It is a wispy layer of connective tissue in the myocardium, that ensheaths each individual muscle fibre.
It contains capillaries and nerves.

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2
Q

Name the 3 layers that make up the walls of blood vessels

A

Tunica intima- inner layer
Tunica media- mid layer
Tunica adventitia- outer layer

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3
Q

In which fashion is the elastic tissue and smooth muscle arranged in the tunica media of arteries

A

Concentric fashion (lamellar)

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4
Q

What is the name given to the subsets of arterioles that allow blood flow to bypass a capillary and flow directly from pre-capillary arteriole to post-capillary venule?

A

Metarterioles (or through channels)

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5
Q

What are pericytes?

A

Cells that wrap around the endothelial cells of capillaries and venues, and are embedded in the basement membrane.
They are able to differentiate into specific cells eg fibroblasts, smooth muscle cells if the cell is damaged.

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6
Q

Which node acts as the pacemaker of the heart and generates an action potential?

A

Sinoatrial node

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7
Q

What is the name give to the small offshoot from the interventricular septum to the right ventricular wall?

A

Septomarginal band

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8
Q

Where does each ventricle deliver blood to?

A

Left-aorta

Right-pulmonary artery

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9
Q

Skeletal muscle can undergo temporal summation, what is this?

A

Multiple action potentials within the space of one muscle contraction

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10
Q

Why are atrial action potentials shorter than ventricular action potentials?

A
  1. The slow calcium ion channels stay open for less time

2. The potassium ion channels close for less time

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11
Q

“Funny” sodium ion channels are found where?

A

Pacemaker cells

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12
Q

What is the pacemaker action potential referred to as?

A

Slow action potential

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13
Q

Why is spontaneous depolarisation slower in the AV node than the SA node?
What is the purpose of it being slower?

A

Narrow fibre diameter

To allow the atria to contract

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14
Q

Why do AV node cells have a longer refractory period than normal cells?

A

To protect the ventricles from beating too quickly.

To prevent the impulse from ‘circling back’ into the atria.

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15
Q

What is the name given to the difference in pressure between two points in a blood vessel?

A

Perfusion pressure

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16
Q

Where is the source of energy for bulk flow derived from?

A

Hydrostatic pressure difference

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17
Q

What is the definition of cardiac output?

A

The amount of blood pumped by one ventricle in a minute.

Each ventricle pumps the same volume of blood in a minute.

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18
Q

What is the name given to the muscles which attach to the cusps in the heart?
How do they attach?

A

Papillary muscles

Chordae tendinae

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19
Q

What function do the Chordae tendinae have?

A

Prevent the cusps from everting into the aria during ventricular systole

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20
Q

What is the definition of diapedesis?

A

The movement of cells out of the vessel lumen

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21
Q

Which type of epithelium forms the endocardium?

A

Simple squamous

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22
Q

Where are purkinje fibres found?

A

Sub-endothelium

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23
Q

What does each wave represent on an ECG?

A

P wave- atrial depolarisation (positive)
Q wave- early ventricular depolarisation (normally negative as impulse moves left to right)
R wave- ventricular depolarisation (positive charge)
S wave- late ventricular depolarisation (charge returns to zero or negative)
T wave- ventricular repolarisation (unpredictable pattern, may be positive or negative)

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24
``` What do each of the following represent: Tall P wave Wide P wave Tall R wave Wide R wave ```
Tall P wave= P pulmonale (right atrial enlargement) Wide P wave= P mitrale (left atrial enlargement) Tall R wave= ventricular enlargement Wide R wave= left ventricular enlargement and hypertrophy
25
Somatic nervous system:
Conscious control of actions | Skeletal muscle
26
Autonomic nervous system:
Maintains homeostasis Cardiac muscle Smooth muscle Splits into parasympathetic (rest and digest) and sympathetic (fight or flight) nervous system
27
Somatic nervous system-which fibres are present here?
Efferent motor nerves
28
Digestibility equation:
Digestibility = amount ingested-amount in faeces X100 (%) of a nutrient Amount ingested or energy
29
What are heart sounds caused by?
Movement of blood within the heart
30
Of the 4 heart sounds (S1, S2, S3, S4), which are audible in the healthy animal?
S1 and S2 S3 and S4 are also heard in horses (large heart size) S3 heard in dogs and cats with heart failure S4 heard in smalls with impaired relaxation of ventricles
31
What can be heard during S1?
Blood rebounding off ventricular walls and being squeezed into aorta
32
What can be heard during S2?
Blood reverberating in great vessels (after pulmonary and aortic valves have closed)
33
What can be heard in S3?
Blood turbulence in left ventricle as blood flows in from atria under pressure Reduced compliance of left ventricle
34
What can be heard in S4?
Impaired relaxation of ventricular wall | Caused by increased force of atrial contraction to overcome the slow relaxation of the ventricles
35
If S3 and S4 are audible in cats or dogs, what is it referred to?
A 'gallop rhythm'
36
What is a murmur?
Abnormal turbulence within the heart or great vessels
37
Where would you hear the tricuspid valve?
Right axilla, rib space 5
38
Where would you hear the: Pulmonary valve Aortic valve Mitral valve
Left axilla for all Pulmonary valve=rib space 3 Aortic valve=rib space 4 Mitral valve=rib space 5
39
Which vessel is the venous blood of the heart drained by?
Great cardiac vein, opens into the right atrium via the coronary sinus Small Thebesian veins drain directly into all 4 heart chambers
40
Where does the pulmonary trunk arise from?
Right ventricle
41
How are blood vessels formed in the embryo?
Cells in the splanchnic mesoderm form 'blood islands' of heamangioblast cells. These stimulate surrounding mesenchymal cells to form endothelial and smooth muscle cells, which form walls around the blood islands. The small vessels coalesce to form larger vessels, then dorsal aortae
42
In the embryological heart, what are the 5 portions called, from cranial to caudal?
``` Truncus arteriosus Bulbus cordis Ventricle Atrium Sinus venosus ```
43
In the developing heart, how many pairs of aortic arches form between the truncus arteriosus and the dorsal aortae?
6
44
In the developing heart, what do the vitelline veins and umbilical arteries veins originate to supply the heart?
Vitelline veins-yolk sac | Umbilical veins-allantois
45
Which veins drain the embryological heart?
Cranial and caudal cardinal veins, which fuse to form the common cardinal vein This drains into the sinus venosus
46
What forms the septum intermedium?
The fusion of endocardial cushions which have developed from mesenchymal cells
47
What does the right atrium form from?
Sinus venosus
48
What does the right ventricle form from?
Bulbus cordis
49
What does the left ventricle form from?
Foetal ventricle
50
Of the aortic arch arteries, which are the aorta and pulmonary trunk continuous with?
Aorta: 4th aortic arch arteries | Pulmonary trunk: 6th aortic arch arteries
51
How many cusps do the pulmonary and aortic valves have?
3
52
What is the ductus arteriosus?
Vessel connecting the descending aorta to the pulmonary artery in the developing foetus Upon closure at birth it becomes the ligamentum arteriosum
53
What is the ductus venosus?
Allows oxygenated blood to bypass the liver in the developing foetus. It shunts most of the left umbilical vein blood flow directly to the vena cava, so that more oxygenated blood reaches the brain
54
What is the function of the ductus arteriosus?
Diverts pulmonary artery blood away from the lungs to enter the aorta Lungs are collapsed
55
The foetus receives cleansed and oxygenated blood from which veins?
Umbilical veins
56
The foetus receives nutrition via which veins?
Vitelline veins
57
What does the remnant of the umbilical vein become? | What does the remnant of the umbilical artery become?
Umbilical vein-round ligament of liver | Umbilical artery-round ligament of bladder
58
What is aortic stenosis and in which dog breeds is it most common?
Narrowing of the region of the aortic valve | Boxers, New Foundlands, Rottweilers
59
What type of heart murmur may be heard with aortic and pulmonary stenosis?
Systolic
60
What is pulmonic stenosis? | In which dog breeds is it most common?
Stenosis of pulmonic valve | Bulldogs, fox terriers
61
What is patent ductus arteriosus? | What kind of heart murmur is heard with it?
Failure of the ductus arteriosus to close Blood flows from aorta to pulmonary artery Volume overload of left side of heart Machinery heart murmer
62
What 4 heart defects make up the Tetralogy of Fallot?
Ventricular septal defect Dextraposed aorta (aorta positioned directly over VSD) Pulmonic stenosis Right ventricular hypertrophy
63
What causes vascular ring anomalies?
The aortic arch forms from the right 4th aortic arch instead of the left, resulting in the trachea and oesophagus being entrapped between the aorta (right) and ligamentum arteriosum (left)
64
What is a congenital portosystemic shunt?
Anastomosis between portal vein and caudal vena cava Intra or extra-hepatic Blood from gut can't be decontaminated by liver, toxins remain in blood Copper irises (cats), stunted growth
65
What are the 3 layers of the heart wall?
Endocardium (inner) Myocardium (mid) Epicardium (outer)
66
How does the cardiac muscle form a functional syncytium?
Myocardial cells branch and interconnect with each other via intercalated discs which consist of gap junctions and tight junctions, allowing propagation of the action potential from cell to cell. These discs allow the cardiac muscle to form a functional syncytium-the muscle fibres contract simultaneously so the entire tissue behaves like a single cell.
67
Why are the heart valves in close contact with fibroblast cells? (between connective tissue plate and atrial/ventricular wall)
Fibroblasts enable active repair of valves, as they are subject to wear and tear
68
Tunica adventitia is absent in which vessel?
Capillary
69
What term is given to nerves of vessels?
Vasa nervosum
70
In which layer of large vessels are the vasa vasorum and vasa nervosum present?
Tunica adventitia
71
In which vessels does the greatest drop in blood pressure occur?
Small arteries and arterioles
72
What is the negative resting membrane potential of cardiac muscle cells?
Between -70 and -80mv
73
How do pacemaker cells generate action potentials?
By spontaneously deolarising
74
What are ectopic pacemakers?
Cells which can develop automaticity after injury (responsible for arrythmias)
75
Is the action potential longer in cardiac or skeletal muscle cells?
Cardiac
76
What is the refractory period?
Ensures that a new action potential can't be initiated before the previous one is almost completed
77
What is the source of calcium ions in: Cardiac muscle Skeletal muscle
Cardiac: Extrcellular Ca2+ which enters through voltage-gated Ca2+ channels Skeletal: Sarcoplasmic reticulum
78
Which channels open at the start of an action potential in a cardiomyocyte?
Fast sodium channels
79
Which channels open between action potentials to create the pacemaker potential?
'Funny' sodium channels
80
What 2 pieces of information can we obtain from an ECG?
Heart rate | Assessment of rhythm
81
What is the normal heart rate for a dog? | What is it for a cat?
Dog=70-160bpm | Cat=120-220bpm
82
When conducting an ECG, what do each 3 leads compare?
Lead 1: compares voltage at left forelimb (pos) and right forelimb (neg) Lead 2: compares left hindlimb (pos) and right forelimb (neg) Lead 3: compares left hindlimb (pos) and left forelimb (neg)
83
What do the 3 augmented unipolar leads compare?
AVR compares right fore with the ave of left fore and left hind AVL compares left fore with the ave of left hind and right fore AVF compares left hind with the ave of left fore and right fore
84
What is an arrythmia?
Abnormal rhythm of the heart
85
What is tachycardia?
Abnormally fast heart rate
86
What is bradycardia?
Abnormally slow heart rate
87
What are the 3 premature complexes?
Supraventricular premature complex (atria depolarising outwith cardiac cycle) Ventricular premature complex (ventricles depolarising outwith cardiac cycle) Junctional premature complex (AV node/bundle depolarising outwith the cardiac cycle)
88
How would you identify a supraventricular or junctional premature complex on an ECG?
There'll be a normal QRS complex in the wrong place
89
How would you identify a ventricular premature complex?
Wider than normal QRS complex | T wave is in opposite direction to the normal QRS complexes
90
What is an atrioventricular block?
Conduction of the action potential is slowed or obstructed in the AV node/bundle
91
What are the roles of the lymphatic system?
Removal of excess water from the ISF Removal of protein and dead cells Taking antigenic material to lymph nodes Movement of lymphatic cells
92
Which vessel does the lymphatic system drain into? | Via which duct?
Drain into the cranial vena cava via the thoracic duct
93
What happens to protein uptake with increased lymph flow? How does it affect colloid osmotic (oncotic) pressure? How does it affect filtration of water?
Increases protein uptake Decreases colloid osmotic pressure Reduces filtration of water
94
What does the adult lymphatic system consist of?
Spleen, thymus, tonsils, lymph nodes, mucous membrane lymphatic nodules, lymphocytes, plasma cells
95
Name 3 palpable lymph nodes in the dog?
Axillary, popliteal, parotid, retropharyngeal, mandibular, femoral, accessory axillary, superficial cervical, superficial inguinal
96
What is the only palpable lymph node in the horse?
Submandibular
97
What are the only 2 palpable lymph nodes in cattle?
Prefemoral, superficial cervical
98
How does increased metabolic rate cause increased blood flow to an area?
Increased O2 consumption, increased production of CO2 and lactic acid, increased K+ outflow O2 is a vasoconstrictor, so reduced O2 due to increased consumption=vasodilation K+, CO2 and lactic acid cause vasodilation, increasing blood flow to area
99
Where is blood pressure detected in the heart?
Baroreceptors in the aortic arch and carotid sinuses
100
What is the vasovagal syncope response?
Fear overrides the baroreflex to cause decreased sympathetic activity and increased parasympathetic activity (via the vagus nerve). Drops the blood pressure enough that cerebral blood flow is compromised, causing the animal to faint

Semester 1 (8 decks)

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