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Cardiovascular > Histology 1 > Flashcards

Histology 1 Flashcards

1
Q

What is the circulatory system composed of? (2)

A
  • Cardiovascular system

* Lymphatic system

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2
Q

What are the roles of the cardiovascular system? (5)

A
  • Transport of oxygen and nutrients to tissues
  • Transport of CO2 and other metabolic waste from the tissues
  • Temperature regulation
  • Distribution of hormones and immune cells
  • Reproductive function in males - penile erection (lol)
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3
Q

Where is the majority of blood at rest?

A

Peripheral veins (~60%)

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4
Q

What are the blood vessel layers? (3)

A
  • Inner layer - tunica intima
  • Middle layer - tunica media
  • Outer layer - tunica adventitia
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5
Q

What is the tunica intima? What is it supported by?

A
  • Single layer of squamous epithelial cells termed endothelial cells
  • supported by a basal lamina and a thin layer of connective tissue
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6
Q

What is tunica media?

A

Predominately smooth muscle - thickness of this layer varies tremendously

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7
Q

What is tunica adventitia?

A

Made up of supporting connective tissue

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8
Q

What is all vasculature lined by?

A

Endothelial cells

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9
Q

In which vessels is tunica media lost?

A

Capillaries

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10
Q

What does tunica adventitia blend with?

A

Surrounding connective tissue

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11
Q

What separates the tunica intima and tunica media layers? Tunica media and tunica adventitia?

A
  • Internal elastic membrane

* External elastic membrane

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12
Q

How are elastic fibres visualised in microscopy?

A
  • Not stained using most common stains (including H&E) but can be visualized with special stains e.g. black
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13
Q

Why are the largest arteries (e.g. aorta) termed elastic arteries?

A

Have many sheets of elastic fibres in tunica media to provide elastic recoil (smooth muscle replaced with elastic tissue)

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14
Q

What is the purpose of elastic arteries?

A
  • Stops blood pressure skyrocketing during systole

* Maintains blood pressure in diastole

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15
Q

In large vessels, which areas can obtain nutrients from the lumen? Therefore, how do other parts obtain nutrients?

A
  • Only inner part of wall

* Will have own vascular supply (Vasa vasorum)

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16
Q

What is vascular supply to large vessels called?

A

Vaso vasorum

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17
Q

Describe the layers of arterioles? Diameter? Function?

A
  • Only 1-2 layers of smooth muscle in their tunica media and almost no adventitia
  • 30-200 um
  • Important in controlling blood flow to a tissue
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18
Q

Describe the layers of capillaries? Diameter?

A
  • Only composed of endothelial cells and a basal lamina

* 4-8 um

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19
Q

What do capillaries often contain just outside the basal lamina? What are these?

A
  • Pericytes

* Connective tissue cells that have contractile (and stem cell) properties

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20
Q

What are the 3 types of capillary? What are they?

A
  • Continuous - endothelial cells form continuous wall
  • Fenestrated - have 50mm pores in wall
  • Discontinuous (sinusoidal) - lack basal lamina and have gaps which macromolecules and cells can pass
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21
Q

Where are the 3 types of capillary found?

A
  • Continuous - muscle, connective tissue, lung, skin, nerve
  • Fenestrated - gut mucosa, endocrine glands, glomeruli of the kidney
  • Discontinuous (sinusoidal) - liver, spleen and bone marrow
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22
Q

Explain the composition of microvascular networks?

A
  • Small arterioles connect to a postcapillary venule through a network of metarterioles (smallest arteriole before reaching capillaries), thoroughfare channels and capillaries
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23
Q

What is the purpose of pre-capillary sphincters? What are they composed of?

A
  • Control flow of blood through the network

* Smooth muscle

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24
Q

Explain the layers of post-capillary venules? Diameter? Function?

A
  • Endothelial cell-lined and contain a thin layer of connective tissue and occasional pericytes
  • 10-30 um
  • Important sites for exchange, e.g. cells moving into the tissue in inflammation
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25
Q

When are post-capillary venules called venules? When are venules called veins?

A
  • Once vessel begins to acquire intermittent smooth muscle cells in tunica media layer
  • Called veins once have a few layers of smooth muscle cells
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26
Q

What are the layers of veins? What is the difference between layers of vein and artery?

A
  • Tunica intima and relatively thin tunica media with only a few layers of SM
  • Tunica media way thinner than would be found in a muscular artery
27
Q

What layers do the largest veins have?

A
  • Thick tunica adventitia which incorporates bundles of longitudinally oriented smooth muscle
28
Q

Why do veins contain most of the blood in the body?

A

Veins are flexible and can accommodate expansion

29
Q

What do most small to medium veins have?

A

Valves that are inward extensions of the tunica intima

30
Q

What are the layers of the heart? (3)

A
  • Endocardium - inner layer
  • Myocardium - middle layer
  • Epicardium - outer layer
31
Q

Name labelled structures of heart (pic)

A 
A - Endocardium 
B - Myocardium 
C - epicardium 
D - pericardium 
E - adipose 
F - visceral serous pericardium 
G - parietal serous pericardium 
H - fibrous pericardium 
I - pericardial cavity
32
Q

What does endocardium line?

A

Entire inner surface of the heart including valves

33
Q

What is the structure of the endocardium?

A
  • Endothelium
  • Basal lamina
  • Thin layer of collagen fibres
  • Layer of denser connective tissue
  • Subendocardium (only in some areas) of loose connective tissue containing small blood vessels and nerves and branches of the impulse conducting system
34
Q

Where is subendocardium particularly present?

A

Interventricular septum

35
Q

What are found in subendocardium?

A

Purkinje fibres contained within conducting cells

36
Q

What is the structure of the myocardium? (2)

A
  • Bundles and layers of contractile cardiac muscle fibres

* Individual muscle fibres surrounded by connective tissue with a rich network of capillaries

37
Q

What are features of cardiac muscle cells? (3)

A
  • Striated
  • Single central nucleus
  • Intercalated discs
38
Q

What are the functions of intercalated discs? (2)

A
  • Join cells end-to-end to prevent separation during contraction
  • Spread of electrical activity
39
Q

What is the structure of the epicardium? (3)

A
  • On surface of heart: single layer of flattened epithelium called mesothelium (also on lung surface)
  • Basal lamina
  • Fibroelastic connective tissue - also adipose tissue in some places
40
Q

What is the purpose of adipose tissue present in epicardium?

A

Coronary vessels typically embedded in this

41
Q

What are the 2 parts of the pericardium? What are they made up of?

A
  • Fibrous pericardium - tough fibrocollagenous connective tissue
  • Serous pericardium - layer of simple squamous epithelium (mesothelium) backed by basal lamina and connective tissue
42
Q

What is the serous pericardium further split into? (2)

A
  • Parietal serous pericardium (in contact with fibrous pericardium)
  • Visceral serous pericardium (in contact with heart)
43
Q

What are the 2 mesothelial (SEROUS) layers seperated by? What is the function of pericardial fluid?

A
  • Pericardial cavity which contains small volume (15-50ml) of pericardial fluid
  • Provides lubrication for heart movement
44
Q

What is the fibrous skeleton of the heart formed by? What is the purpose of the fibrous skeleton? (3)

A
  • Thick bands of fibrous connective tissue around the heart valves, between the atria, and between the ventricles
  • Supports valves
  • Provides attachment for cardiac muscle fibres
  • Prevents ectopic spread of electricity from atria to ventricles
45
Q

What is the structure of the heart valves?

A
  • Outer endothelial layer with basal lamina
  • Layer of collagen and elastin fibres
  • Core of dense connective tissue called the lamina fibrosa in continuity with the fibrous skeleton
46
Q

How are leaflets of mitral and tricuspid valves prevented from refluxing into atrium during ventricular contraction?

A

Anchored to papillary muscles in wall of the ventricle by chordae tendineae which merge with the lamina fibrosa to form touch anchor

47
Q

Do the heart valves contain blood vessels?

A

No

48
Q

What is the lamina fibrosa?

A

The core of a heart valve and is dense irregular connective tissue that is continuous with the fibrous skeleton of the heart

49
Q

What is the valve covered on bot sides by?

A

Endothelium

50
Q

What are the 3 types of cardiac muscle cells (myocytes)?

A
  • Contractile cells (99%)
  • Pacemaker cells
  • Conducting cells
51
Q

What are pacemaker and conducting cells?

A

Modified cardiac muscle cells

52
Q

How do pacemaker cells differ from contractile cardiac myocytes? (4)

A
  • Considerably smaller (4-8um)
  • Embedded in more extensive matrix of connective tissue
  • Very few irregularly-arranged myofibrils
  • Little glycogen and no proper T-tubule system
53
Q

Why do pacemaker cells appear pale histologically?

A

Due to scarceness of organelles within them

54
Q

What is the purpose of the AV tunnel of the fibrous cardiac skeleton?

A

Electrical activity passes through tunnel just below AV valve into interventricular conduction

55
Q

How does fibrous cardiac skeleton electrically isolate atria from the ventricles?

A

No excitation passes through the non-conducting tissue of skeleton

56
Q

What is the difference between conducting cells (purkinje fibres) and normal cardiac muscle cells? (6)

A
  • Much larger
  • Found in subendocardial layer deep to endocardium
  • Have abundant glycogen
  • No T-tubules
  • No intercalated discs
  • Sparse actin and myosin filaments
57
Q

What do purkinje fibres/conducting cells appear like histologically? Why?

A
  • Very pale

* Sparse actin and myosin filaments only found at the periphery of the cell

58
Q

How do purkinje fibres distribute excitatory activity?

A

Such that ventricular contraction occurs form inferior to superior

59
Q

What does lymphatic system consist of? What tissues do not have lymphatic drainage?

A
  • Lymphatic vessels that drain tissue fluid, eventually returning it to veins in the base of the neck
  • Bone and brain
60
Q

What is a significant difference between lymphatic circulation and systemic circulation? What is tissue fluid (interstitial fluid) composed of? (4)

A
  • Lymphatic circulation is not a complete circuit - lymphatics are blind-ending
  • Ions, lipids, proteins and cells
61
Q

Where does excess interstitial fluid drain?

A

Most excess interstitial fluid returns to capillaries and venous vessels, but a portion returns to the circulatory system by entering lymphatic vessels

62
Q

What does lymph pass through on the way to the root of the neck? What is the purpose of this?

A
  • Lymph nodes

* Immunological surveillance

63
Q

How is flow produced in lymphatic vessels? (3)

A

No central pump so..

  • Hydrostatic pressure in tissue
  • Compression of vessels by voluntary muscle
  • Valves in the vessels

Cardiovascular (28 decks)

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