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Microanatomy > Cardiovascular System > Flashcards

Cardiovascular System Flashcards

1
Q

3 Layers of Vessels (Tunics)

A
  • Tunica intima
  • Tunica media
  • Tunica adventitia
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2
Q

Tunica Intima

A
  • Endothelial cells
  • Basal lamina
  • Subendothelial connective tissue

-Internal elastic lamina composed of elastin (most prominent in muscular arteries)

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3
Q

Tunica Media

A
  • Circularly arranged smooth muscle
  • Contraction narrows the lumen
  • Elastic fibers, reticular fibers, proteoglycans produced by smooth muscle cells (not fibroblasts)
  • Replaced by pericytes in capillaries and postcapillary venules

-External elastic lamina seperates media from adventitia (most prominent in muscular arteries)

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4
Q

Pericytes

A
  • Contractile cells that wrap around endothelial cells

- Undifferentiated mesenchymal cells that can become smooth muscle or endothelium

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5
Q

Tunica Adventitia

A
  • Longitudinally oriented collagen (Type I) and elastic fibers
  • Blends into surrounding connective tissue
  • Contains automatic nerves that enter tunica media

-Thick vessels: contains vasa vasorum

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6
Q

Vasa Vasorum

A
  • Found in adventitia
  • Nourishes the adventitia and media of vessels with walls too thick for diffusion of nutrients
  • Found in veins because of low nutrient content of blood passing through
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7
Q

Innervation

A
  • Smooth muscle in tunica media by parasympathetic/sympathetic fibers
  • SNS Norepinephrine (vasculature) causes vasoconstriction
  • SNS Acetylcholine causes (skeletal muscle) causes vasodilation
  • PNS causes vasodilation
  • More prevalent in arteries (more muscle)
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8
Q

Endothelial Cells

A
  • Permeability barrier

- Secretes collagen Type IV/laminin into basement membrane

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9
Q

Endothelial Cell Secretions

A
  • Thrombus Formation: VWF for platelet adhesion
  • Vasoactive factors to regulate blood flow (vasodilate/constrict) (endothelin, NO)
  • Minimize thrombus formation: PIG2
  • Growth factors (FGF, PDGF)
  • Cell adhesion molecules (selectins/integrins)
  • Contain membrane-bound organelles called Weibel-Palade bodies
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10
Q

Weibel-Palade bodies

A
  • Stores products of endothelial cells such as VWF

- Derived from Golgi

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11
Q

Arteries

A
  • Tunica media is dominant layer
  • Narrower lumen than vein
  • Thick wall relative to lumen
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12
Q

Elastic Arteries

Aorta, Pulmonary trunk

A

-Elastic recoil helps with steadier flow

Intima:
-internal elastic lamina
Media: 
-reticular fibers + ground substance
-no external elastic lamina
Adventitia
-Loose network of collagen/elastic fibers
-Vasa vasorum
-Fibroblasts+macrophages
-Loosely defined outer boundary
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13
Q

Muscular Arteries

Most of body

A

-Distribute blood to specific organs as needed

Intima:
-Internal elastic lamina prominent and wavy during contraction
Media:
-Many layers (up to 40) of smooth muscle
-Few elastic fibers
-Fragmented external elastic lamina that extend into adventitia
Adventitia:
-Collagen and adipose
-Larger vessels have vasa vasorum
-Blends into surrounding connective tissue

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14
Q

Arterioles

A

-Regulates blood pressure and distribution of blood to capillary beds

Intima:
-May or may not have internal elastic lamina
Media:
-5 layers of smooth muscle or less
-External elastic lamina absent
Adventitia:
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15
Q

Metarterioles

A
  • Smallest arterioles
  • Discontinuous layer of smooth muscle
  • Preferential channels through capillary beds (bypasses)
  • Precapillary sphincters control flow into capillaries
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16
Q

Capillaries

A
  • Single endothelium layer + basal lamina
  • Discontinuous layer of pericytes surround
  • No media, adventitia, internal/external laminae
17
Q

Continuous capillaries

A
  • Found in most tissues
  • Tight junctions between endothelial cells forms barrier
  • No fenestrations
18
Q

Fenestrated Capillaries

A
  • Found in GI, kidney, endocrine
  • Fenestrations/pores allow for greater permeability
  • Diaphragms in most organs (except glomerular capillaries)
19
Q

Discontinuous Capillaries (sinusoids)

A
  • Found in liver, bone marrow, spleen, adrenal cortex
  • Leakiest type of capillary
  • Wide diameter and irregular shape
  • Large gaps between endothelial cells
  • Discontinuous or absent basal lamina
20
Q

Veins

A
  • Large lumens, thin walls, low hydrostatic pressure
  • Valves to prevent backflow of blood (folds of tunica intima)
  • Valves most common in large veins below heart
  • Classified on basis of size (venules, small, medium, large)
21
Q

Postcapillary Venules

A
  • Wide diameter distinguishes from capillaries
  • Mainly endothelium, basal lamina, discontinuous layer of pericytes
  • Main site of diapedesis of leukocytes
22
Q

Muscular venules

A

Media:
-1-2 layers smooth muscle
Adventitia
-Very thin

23
Q

Medium/Large Veins

A

Intima:
-Thin subendothelial connective tissue layer
-Some smooth muscle cells
-Thin internal elastic lamina
-Valves are paired folds of intima
Media:
-Thinner than media of a similar sized artery
Adventitia
-Thickest layer of the vessel wall
-Collagen, elastic fibers, fibroblasts
-Large veins also have bundles of longitudinal smooth muscle

In artery-vein companion pairs, vein is usually larger and appears collapsed or irregular in shape

24
Q

Lymphatic Capillaries

A
  • Single layer of endothelial cells
  • Discontinuous/absent basal lamina
  • More irregular shape than regular capillaries
25
Q

Large Lymphatic Vessels

A
  • Similar to small veins
  • Larger lumens, thinner walls, have valves
  • Large lymphatic vessels with up to three layers of media
26
Q

Cardiac Wall

A
  • Endocardium continuous with tunica intima and contains impulse conduction system
  • Myocardium continuous with tunica media
  • Epicardium continuous with tunica adventitia
27
Q

Endocardium

A
  • Endothelium

- Subendothelial connective tissues (Collagen, Elastic fibers)

28
Q

Ventricular Endocardium

A
  • Contains Purkinje fibers
  • Middle layer of connective tissue
  • Smooth muscle cells
  • Subendocardial layer of collagenous/elastic fibers
29
Q

Myocardium

A
  • Mostly cardiac muscle (involuntary striated)
  • Ventricular myocytes are larger
  • Thicker in ventricle than atria and left than right
30
Q

Epicardium

A
  • Outermost layer is visceral pericardium

- Subserosal connective tissue contains abundant adipocytes, large blood vessels, large nerve bundles

31
Q

Visceral Pericardium

A

-Mesothelium plus fibrous connective tissue

32
Q

Atrioventricular Valves

A
  • Folds of endocardium covering fibrous core
  • Do not include myocardium
  • Base of each leaflet attached to annulus fibrosus of cardiac skeleton
  • Free edges of leaflets anchored to papillary muscles via chordae tendineae
  • Chordae Tendineae have connective tissue cores re-covered by endocardium
33
Q

Semilunar Valves

A
  • Pulmonary and atrial/aortic

- Not associated with chordae tendineae or papillary muscles

34
Q

Cardiac Skeleton

A
  • Dense collagenous tissue (not cartilage or bone)
  • Anchoring point of myocytes
  • Annuli FIbrosi, 2 Fibrous Trigones (left/right), Septum Membranaceum
35
Q

Annuli Fibrosi

A
  • Surround openings of aorta, pulmonary artery, atrioventricular orifices
  • Attachment sites for leaflets of heart valves
36
Q

Fibrous Trigones

A
  • Unite annuli fibrosi together

- AV bundle pierces right fibrous trigone to reach interventricular septum

37
Q

Septum membranaceum

A
  • Extend downward from right fibrous trigone

- Upper non-muscular part of interventricular septum

Microanatomy (4 decks)

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