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ESA 2 > CVS Session 1: anatomy and histology > Flashcards

CVS Session 1: anatomy and histology Flashcards

1
Q

What are the factors that affect diffusion?

A
  1. Area for exchange: determined by capillary density and generally not limiting as area usually very large
  2. Diffusion resistance: affected by nature of molecule, nature of the barrier and the diffusion distance. For small molecules this is usually not limiting
  3. Concentration gradient: between capillary blood and tissues. Must be maintained at a high concentration to have high diffusion rate, by rate of flow
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2
Q

How does rate of blood flow (perfusion rate) vary between tissues?

A

Increased metabolism must be met by increased blood flow to ensure adequate oxygen and nutrients
Brain-high constant flow
Heart-flow increases during exercise
Kidneys-high constant flow
Skeletal muscle-very high during exercise
Gut-high after a meal
Skin-increases to control temperature

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3
Q

What is normal cardiac output at rest and how high can it rise during exercise?

A

5L per minute, can increased to a maximum of 25L per minute (for athletes this could be a few litres higher)

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4
Q

What is the distribution of blood in the vascular system?

A

67% veins
17% heart and lungs
11% arteries and arterioles
5% capillaries

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5
Q

Describe the main components of the cardiovascular system

A

Pump-heart
Distribution system-arteries and blood
Exchange mechanism-capillaries
Flow control-arterioles and pre-capillary sphincters

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6
Q

What is resistance?

A

Reduces the ease with which some regions are perfused in order to direct flow elsewhere (e.g. brain is harder to perfuse because of gravity)
Arterioles and pre-capillary sphincters add it to the CVS

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7
Q

What is capacitance?

A

A temporary blood store that can be returned to the heart at a different rate in order to control the total flow in a system.
Veins provide it as thin walls with smooth muscle can easily distend or collapse

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8
Q

Why is the heart 2 pumps in series?

A

Left pumps blood around systemic circulation, right pumps blood around pulmonary circulation. Circulation is from high to low pressure then back to heart.

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9
Q

The heart lies in the middle mediastinum. What is this?

A

The region in the thoracic cavity between the right and left pleural cavities. Contains the pericardial sac

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10
Q

What does the pericardium contain?

A

The heart and the beginning of the great vessels

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11
Q

Describe the fibrous pericardium

A

Tough external layer. Continuous with the central tendon of diaphragm, relatively non-distensible, prevents overfilling

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12
Q

What is cardiac tamponade caused by?

A

Pericardial effusion or haemopericardium (due to perforation of a weakened area of heart from MI, surgery or stab wound) causes an accumulation of fluid, compressing the heart because of the non-distensibility of the fibrous pericardial sac.
Quickly becomes lethal as circulation fails due to the backup of blood, beginning where the SVC enters the pericardium

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13
Q

Describe the serous pericardium

A

Inner layer split itself into two layers, separated by the pericardial cavity which contains a small amount of lubricating fluid to minimise friction.
Outer parietal layer: lines internal surface of fibrous pericardium
Inner visceral layer: forms epicardium (shiny outer layer of the heart)

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14
Q

Functions of the pericardium?

A
  1. Holds heart in place as is attached to diaphragm, sternum and tunica adventitia of great vessels
  2. Prevents overfilling
  3. Lubrication-reduces friction as heart beats
  4. Protection from infection (e.g. from lungs)
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15
Q

What is the innervation of the pericardium?

A

Phrenic nerve-C3,4,5
Also provides motor and sensory innervation to diaphragm
Source of referred pain e.g. shoulder pain in pericarditis

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16
Q

Describe the main features of the transverse pericardial sinus

A

Location: posterior to ascending aorta and pulmonary trunk, anterior to SVC, superior to left atrium
Formed during embryonic folding
Function: separates arterial and venous vessels
Clinical use: to identify and ligate arteries during coronary artery bypass grafting

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17
Q

What is pericarditis?

A

Inflammation of the pericardium, may make serous pericardium causing friction audible on auscultation.
Symptoms/signs: chest pain, pericardial friction rub on auscultation
Chronic cases may calcify, reducing cardiac efficiency

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18
Q

What is pericardial effusion?

A

Fluid from pericardial capillaries enters pericardial cavity, or pus.
Heart compressed and ineffective
Due to inflammation or congestive heart failure (where venous return is greater than cardiac output due to right heart hypertension)

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19
Q

Describe the main features of the oblique pericardial sinus

A

A pericardial reflection surrounding the veins of the heart. A pocket-like space posterior to the base of the heart (at top), formed by the left atrium.
Bounded laterally by reflection surrounding pulmonary veins and IVC, and posteriorly by the pericardium overlying the anterior oesophagus
Can be felt inferiorly but is a blind sac

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20
Q

What makes up the endocardium?

A

Thin endothelium and connective tissue, covers valves

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21
Q

What makes up the myocardium?

A

Thick, helical cardiac muscle forming the main walls

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22
Q

What makes up the epicardium?

A

Thin mesothelium formed by the visceral layer of the serous pericardium

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23
Q

Describe the orientation of the heart, a ‘pyramid that’s fallen over’

A

Apex-pounts in an anterior-inferior direction
Anterior/sternocostal: right ventricle
Posterior/base: left atrium
Inferior/diaphragmatic: left and right ventricles
Right pulmonary: right atrium
Left pulmonary: left atrium

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24
Q

What are the borders of the heart?

A

Right-right atrium
Left-left ventricle and part of left atrium
Inferior-right ventricle (v. small contribution from left)
Superior: right and left atria and the great vessels

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25
What are cardiac sulci?
Grooves on the surface created by the chambers.
26
What is the coronary sulcus?
AKA atrioventricular groove. Runs transversely around the heart
27
What is the name of the sulci which run vertically to separate the ventricles?
Anterior and posteriro interventricular
28
Through which structures does blood pass to enter the right atrium?
IVC, SVC and coronary sinus
29
Describe the passage of blood around the heart and great vessels
1. Enters RA through IVC, SVC and coronary sinus (from right and left brachiocephalic veins) 2. Goes through tricuspid valve into right ventricle 3. Through pulmonary semilunar valve to pulmonary trunk 4. Moves into right (sup and inferior) and left pulmonary arteries to travel to lungs 5. Oxygenated blood returned to heart through pulmonary veins 6. Into left atrium 7. Through mitral valve into left ventricle 8. Through aortic semilunar valve into aorta, distributed to systemic circulation through its branches
30
What do the right and left aortic sinuses give rise to, respectively?
Right and left coronary arteries
31
What are the branches of the left coronary artery?
Anterior interventricular, left marginal and left circumflex
32
What are the branches of the right coronary artery?
Right marginal anteriorly, posterior interventricular posteriorly
33
What is the role of the coronary sinus?
Cardiac veins which drain into a coronary sinus (the main cardiac vein, located on the posterior surface *identify on prosection* Sinus drains into right atrium (opening is between the right AV orifice and the IVC orifice)
34
Which tributaries drain into the coronary sinus?
Great cardiac vein: from apex, follows anterior IV groove into coronary sulcus, around left heart to joint coronary sinus *identify on prosection* Small cardiac vein: anterior surface, passes around right heart to join coronary sinus Middle cardiac vein: posterior heart, drains into right heart Left marginal vein: left posterior side Left posterior ventricular vein: centre posterior, runs along posteriror IV sulcus to join coronary sinus
35
Right coronary artery?
Supplies: Right atrium, SAN, AVN, posterior IVS Vein: small and middle cardiac veins
36
Right marginal artery?
Supplies: right ventricle, apex Vein: small and middle cardiac veins
37
Posterior interventricular artery?
Supplies: RV, LV, posterior 1/3 of IVS Vein: left posterior ventricular vein
38
Left coronary artery?
Supplies: left atrium, right atrium, IVS, AV bundles Vein: great cardiac vein
39
Anterior interventricular artery? (=LAD: left anterior descending)
Supplies: RV, LV, anterior 2/3 of IVS Vein: great cardiac vein
40
Left marginal artery?
Supplies: left ventricle Vein: left marginal and great cardiac veins
41
Circumflex artery?
Suplies: LA, LV Vein: great cardiac vein
42
Describe the structure of cardiac muscle
Striated Intercalated discs: strong horizontal components at Z band level. Between cells mechanical coupling. Gap junctions: weaker vertical components. Allow electrical coupling Central nucleus: one or two per cell T tubules at Z band (not A-I band as in skeletal) Myofibrils: not distinct, cross-striations less obvious, less enclosed in SR, actin and myosin continuous masses in cytoplasm, adherens-type junctions to anchor cells to actin Diads (not triads) of T tubule system
43
What are purkinje fibres?
Modified monocytes. Have abundant glycogen, sparse myofilaments, extensive gap junctions, few intercalated discs. Located between the endocardium and myocardium Carry impulses from SAN to ventricular muscle very quickly to allow synchronous ventricular contraction
44
How does blood get from the right ventricle to the lungs?
RV-->pulmonary trunk-->R/L pulmonary artery-->lung | Pulmonary arteries are major elastic arteries
45
What are the major elastic arteries that transport blood from the left ventricle?
Into aortic arch then into brachiocephalic, left common carotid or left subclavian arteries Branches throughout abdomen, terminate by bifurcating into the left and right common iliac arteries in the pelvis
46
State the main features of elastic conducting arteries
Conduct blood away from the heart and act as pressure reservoirs. E.g. aorta, subclavian In systole, pressure rises so walls stretch and in diastole walls recoil to maintain pressure. Walls may be yellow when fresh due to the high elastin content
47
Describe the structure of elastic conducting arteries
Tunica intima: endothelial cells with long axes orientated parallel to the long axis of the artery. Narrow, discontinuous elastc lamina. Next to lumen Tunica media: fenestrated elastic membranes with smooth muscle and collagen between. May have thin external elastic lamina. Thick Tunica adventitia: thin fibroelastic connective tissue with vaso vasorum (vessels of vessles), lymph vessels and nerve fibres
48
What is an aortic dissection?
A break in the tumour intima causing blood to enter the tunica media between the elastin. Painful and serious, happens in Marfan's syndrome due to the defective elastin
49
What are the main features of muscular (distributing) arteries?
Intermediate diameter. Most of the 'named' arteries. | Branch into arterioles whose function is to regulate amount of blood reaching a tissue or regulate blood pressure
50
Describe the structure of muscular (distributing) arteries
Tunica intima: endothelium, thick internal elastic lamina Tunica media: layers of circular smooth muscle cells connected by gap junctions for coordinate contraction. Thick external elastic lamina Tunica adventitia: thin fibroelastic connective tissue with thin vaso vasorum, lymphatic vessels and nerve fibres
51
How does vasoconstriction occur?
Sympathetic nerve fibres stimulate release of noradrenaline. This diffuses through fenestrations in the external elastic into the TM to depolarise superficial smooth muscle cells, and gap junctions propagate this to all cells of the TM
52
What are end arteries?
Terminal arteries supplying all/most of blood to a particular area without significant collateral circulation. E.g. coronary artery, splenic and renal arteries If occluded blood supply to that area is cut off Absolute end arteries are the central artery to the retina and labyrynthine artery of the internal ear
53
What is bridging?
Compression of a segment of a coronary artery during systole, causing narrowing that reverses during diastole
54
What are the main features of arterioles?
Arteries with a diameter less than 0.1mm 1-3 layers of smooth muscle in TM thin external elastic lamina only in large arterioles in small arterioles TM is a single smooth muscle layer around endothelium with no elastic lamina very thin adventitia
55
What are metarterioles?
Arteries that supply blood to capillary beds Smooth muscle layer is discontinuous Individual muscle cells are spaced apart
56
What is a pre-capillary sphincter?
Each smooth muscle cell of metarterioles acts as a sphincter by controlling blood flow into capillaries during contraction
57
General features of capillaries
Lowest blood velocity so gas and nutrient exchange can occur About 10 um diabeter and less than 1mm long Single layer of endothelium plus a basement membrane
58
What are continuous capillaries?
Most common type. In neurones, muscle, connective tissue, exocrine glands and lungs Continuous endothelial layer with tight junctions
59
What are fenestrated capillaries?
Found in the gut, endocrine glands and renal glomerulus. Interruptions in endothelium bridged by a thin diaphragm
60
What are sinusoids?
Discontinuous capillaries of about 40um diameter. Found in liver, spleen and bone marrow. Gaps in the wall allow whole cells to move between blood and tissue
61
What are pericytes?
Branching network on the outside of capillary endothelium. Can divide into muscle cells or fibroblasts during angiogenesis, tumour growth and wound healing
62
General features post-capillary venules
Endothelial lining with pericytes. Receive blood from capillaries and are even more permeable. Diameter ~20um Lower pressure than capillaries and surrounding tissue so fluid drains into them In inflammation however fluid and leukocytes move to venules
63
General features-venules
Diameter about 1mm Smooth muscle and TM appear Can have valves-thin extensions that press together to restrict retrograde blood transport
64
General features-veins
Usually larger diameter than accompanying artery and thinner wall with more CT, less elastic and muscle fibres. Valves act with muscle contraction to propel blood to the heart Small veins: developed TA, thin TI and TM Large veins: >10mm. Thicker TI, developed TA, not prominent TA except legs which have thick. E.g. vena cavae, pulmonary vein, portal vein renal vein, internal jugular vein, iliac vein, azygous vein
65
What are venae comitantes?
Deep paired veins. In some positions accompany smaller artery on each side, 3 vessels wrapped in one sheath. The artery pulsing promotes venous return in the adjacent parallel paired veins. E.g. brachial, ulnar and tibial venae cominantes

ESA 2 (58 decks)

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