Heart Histology Flashcards

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
Q
What do each of the following represent:
Tall P wave 
Wide P wave
Tall R wave
Wide R wave
A

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

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25
Q

Somatic nervous system:

A

Conscious control of actions

Skeletal muscle

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26
Q

Autonomic nervous system:

A

Maintains homeostasis
Cardiac muscle
Smooth muscle
Splits into parasympathetic (rest and digest) and sympathetic (fight or flight) nervous system

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27
Q

Somatic nervous system-which fibres are present here?

A

Efferent motor nerves

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28
Q

Digestibility equation:

A

Digestibility = amount ingested-amount in faeces X100
(%) of a nutrient Amount ingested
or energy

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29
Q

What are heart sounds caused by?

A

Movement of blood within the heart

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30
Q

Of the 4 heart sounds (S1, S2, S3, S4), which are audible in the healthy animal?

A

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

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31
Q

What can be heard during S1?

A

Blood rebounding off ventricular walls and being squeezed into aorta

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32
Q

What can be heard during S2?

A

Blood reverberating in great vessels (after pulmonary and aortic valves have closed)

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33
Q

What can be heard in S3?

A

Blood turbulence in left ventricle as blood flows in from atria under pressure
Reduced compliance of left ventricle

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34
Q

What can be heard in S4?

A

Impaired relaxation of ventricular wall

Caused by increased force of atrial contraction to overcome the slow relaxation of the ventricles

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35
Q

If S3 and S4 are audible in cats or dogs, what is it referred to?

A

A ‘gallop rhythm’

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36
Q

What is a murmur?

A

Abnormal turbulence within the heart or great vessels

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37
Q

Where would you hear the tricuspid valve?

A

Right axilla, rib space 5

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38
Q

Where would you hear the:
Pulmonary valve
Aortic valve
Mitral valve

A

Left axilla for all
Pulmonary valve=rib space 3
Aortic valve=rib space 4
Mitral valve=rib space 5

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39
Q

Which vessel is the venous blood of the heart drained by?

A

Great cardiac vein, opens into the right atrium via the coronary sinus
Small Thebesian veins drain directly into all 4 heart chambers

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40
Q

Where does the pulmonary trunk arise from?

A

Right ventricle

41
Q

How are blood vessels formed in the embryo?

A

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
Q

In the embryological heart, what are the 5 portions called, from cranial to caudal?

A
Truncus arteriosus 
Bulbus cordis
Ventricle
Atrium
Sinus venosus
43
Q

In the developing heart, how many pairs of aortic arches form between the truncus arteriosus and the dorsal aortae?

A

6

44
Q

In the developing heart, what do the vitelline veins and umbilical arteries veins originate to supply the heart?

A

Vitelline veins-yolk sac

Umbilical veins-allantois

45
Q

Which veins drain the embryological heart?

A

Cranial and caudal cardinal veins, which fuse to form the common cardinal vein
This drains into the sinus venosus

46
Q

What forms the septum intermedium?

A

The fusion of endocardial cushions which have developed from mesenchymal cells

47
Q

What does the right atrium form from?

A

Sinus venosus

48
Q

What does the right ventricle form from?

A

Bulbus cordis

49
Q

What does the left ventricle form from?

A

Foetal ventricle

50
Q

Of the aortic arch arteries, which are the aorta and pulmonary trunk continuous with?

A

Aorta: 4th aortic arch arteries

Pulmonary trunk: 6th aortic arch arteries

51
Q

How many cusps do the pulmonary and aortic valves have?

A

3

52
Q

What is the ductus arteriosus?

A

Vessel connecting the descending aorta to the pulmonary artery in the developing foetus
Upon closure at birth it becomes the ligamentum arteriosum

53
Q

What is the ductus venosus?

A

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
Q

What is the function of the ductus arteriosus?

A

Diverts pulmonary artery blood away from the lungs to enter the aorta
Lungs are collapsed

55
Q

The foetus receives cleansed and oxygenated blood from which veins?

A

Umbilical veins

56
Q

The foetus receives nutrition via which veins?

A

Vitelline veins

57
Q

What does the remnant of the umbilical vein become?

What does the remnant of the umbilical artery become?

A

Umbilical vein-round ligament of liver

Umbilical artery-round ligament of bladder

58
Q

What is aortic stenosis and in which dog breeds is it most common?

A

Narrowing of the region of the aortic valve

Boxers, New Foundlands, Rottweilers

59
Q

What type of heart murmur may be heard with aortic and pulmonary stenosis?

A

Systolic

60
Q

What is pulmonic stenosis?

In which dog breeds is it most common?

A

Stenosis of pulmonic valve

Bulldogs, fox terriers

61
Q

What is patent ductus arteriosus?

What kind of heart murmur is heard with it?

A

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
Q

What 4 heart defects make up the Tetralogy of Fallot?

A

Ventricular septal defect
Dextraposed aorta (aorta positioned directly over VSD)
Pulmonic stenosis
Right ventricular hypertrophy

63
Q

What causes vascular ring anomalies?

A

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
Q

What is a congenital portosystemic shunt?

A

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
Q

What are the 3 layers of the heart wall?

A

Endocardium (inner)
Myocardium (mid)
Epicardium (outer)

66
Q

How does the cardiac muscle form a functional syncytium?

A

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
Q

Why are the heart valves in close contact with fibroblast cells? (between connective tissue plate and atrial/ventricular wall)

A

Fibroblasts enable active repair of valves, as they are subject to wear and tear

68
Q

Tunica adventitia is absent in which vessel?

A

Capillary

69
Q

What term is given to nerves of vessels?

A

Vasa nervosum

70
Q

In which layer of large vessels are the vasa vasorum and vasa nervosum present?

A

Tunica adventitia

71
Q

In which vessels does the greatest drop in blood pressure occur?

A

Small arteries and arterioles

72
Q

What is the negative resting membrane potential of cardiac muscle cells?

A

Between -70 and -80mv

73
Q

How do pacemaker cells generate action potentials?

A

By spontaneously deolarising

74
Q

What are ectopic pacemakers?

A

Cells which can develop automaticity after injury (responsible for arrythmias)

75
Q

Is the action potential longer in cardiac or skeletal muscle cells?

A

Cardiac

76
Q

What is the refractory period?

A

Ensures that a new action potential can’t be initiated before the previous one is almost completed

77
Q

What is the source of calcium ions in:
Cardiac muscle
Skeletal muscle

A

Cardiac: Extrcellular Ca2+ which enters through voltage-gated Ca2+ channels
Skeletal: Sarcoplasmic reticulum

78
Q

Which channels open at the start of an action potential in a cardiomyocyte?

A

Fast sodium channels

79
Q

Which channels open between action potentials to create the pacemaker potential?

A

‘Funny’ sodium channels

80
Q

What 2 pieces of information can we obtain from an ECG?

A

Heart rate

Assessment of rhythm

81
Q

What is the normal heart rate for a dog?

What is it for a cat?

A

Dog=70-160bpm

Cat=120-220bpm

82
Q

When conducting an ECG, what do each 3 leads compare?

A

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
Q

What do the 3 augmented unipolar leads compare?

A

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
Q

What is an arrythmia?

A

Abnormal rhythm of the heart

85
Q

What is tachycardia?

A

Abnormally fast heart rate

86
Q

What is bradycardia?

A

Abnormally slow heart rate

87
Q

What are the 3 premature complexes?

A

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
Q

How would you identify a supraventricular or junctional premature complex on an ECG?

A

There’ll be a normal QRS complex in the wrong place

89
Q

How would you identify a ventricular premature complex?

A

Wider than normal QRS complex

T wave is in opposite direction to the normal QRS complexes

90
Q

What is an atrioventricular block?

A

Conduction of the action potential is slowed or obstructed in the AV node/bundle

91
Q

What are the roles of the lymphatic system?

A

Removal of excess water from the ISF
Removal of protein and dead cells
Taking antigenic material to lymph nodes
Movement of lymphatic cells

92
Q

Which vessel does the lymphatic system drain into?

Via which duct?

A

Drain into the cranial vena cava via the thoracic duct

93
Q

What happens to protein uptake with increased lymph flow?
How does it affect colloid osmotic (oncotic) pressure?
How does it affect filtration of water?

A

Increases protein uptake
Decreases colloid osmotic pressure
Reduces filtration of water

94
Q

What does the adult lymphatic system consist of?

A

Spleen, thymus, tonsils, lymph nodes, mucous membrane lymphatic nodules, lymphocytes, plasma cells

95
Q

Name 3 palpable lymph nodes in the dog?

A

Axillary, popliteal, parotid, retropharyngeal, mandibular, femoral, accessory axillary, superficial cervical, superficial inguinal

96
Q

What is the only palpable lymph node in the horse?

A

Submandibular

97
Q

What are the only 2 palpable lymph nodes in cattle?

A

Prefemoral, superficial cervical

98
Q

How does increased metabolic rate cause increased blood flow to an area?

A

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
Q

Where is blood pressure detected in the heart?

A

Baroreceptors in the aortic arch and carotid sinuses

100
Q

What is the vasovagal syncope response?

A

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