Cardiovascular System

Ross & Pawlina (6th ed.), Plates 32-35, pgs. 432-439
Ross & Pawlina (6th ed.), Ch 13, pgs. 400-430, CardiovascularSystem


The goal of this lab is to examine and describe the structural organization of the heart and the major classes of blood vessels.

Below is a schematic drawing showing the key structural features and relative sizes of skeletal, smooth, and cardiac muscle as you would observe them with high power. 


Slide Descriptions


Part I: Heart

Webslide 0026_B: Cardiac Muscle, monkey, H&E
[Aperio ImageScope] [Aperio WebScope]

Cardiac muscle fibers can be seen in both cross and longitudinal sections.  Measure fiber diameters and note blood vessels filled with RBCs between the fibers.  Fine details of the myocardiocytes can be seen, especially myofibrils, cross striations, intercalated disks, and mitochondria next to the nuclei.
Note also the simple squamous epithelium covering both free surfaces of the heart in this section.  How can you tell whether each surface is endocardium or epicardium?  Based on a low-power view, can you tell whether this section was taken from an atrium or a ventricle?



Webslide 0024_B: AV valve & suclus, Cat, GMA, 1.5um AF&TB
[Aperio ImageScope] [Aperio WebScope]

Note the simple squamous epithelium on the free surfaces of the heart. Are these endocardium or epicardium? How can you tell?



Webslide 0033_100x_B: Heart, Purkinje fibers
[Aperio ImageScope] [Aperio WebScope]

The lumen of the ventricle is covered by a simple squamous epithelium and an underlying layer of connective tissue. Deep to this connective tissue is a thick layer containing Purkinje fibers. Measure the diameter of the Purkinje fibers and their nuclei. Are intercalated discs present in these fibers? Note the paucity of fibrils within these cells. What pale staining material fills the central portion of these fibers?



Part II: Blood Vessels

Webslide 0022_B: Aorta, monkey, H&E
[Aperio ImageScope] [Aperio WebScope]

This is an example of an elastic artery. Note:

  • Tunica intima with endothelial nuclei, longitudinal subendothelial fibers of reticulin and smooth muscle.
  • Tunica media with multiple wavy light pink elastic membranes (up to 70 such laminae may be counted in a human aorta) and interleaving circular smooth muscle fibers.
  • Tunica adventitia with some loose fatty areolar connective tissue and inner dense irregular collagen containing vasa vasorum.

Think about possible effects of normal blood pressure distension on endothelial cell plumpness and intimal corrugation. You might expect more penetration by vasa vasorum in thicker vessels of larger animals. Notice that elastic laminae stain pink here, but don’t stain at all with AF & TB (Slide 4, below).




Webslide 0174_B: Muscular Artery
[Aperio ImageScope] [Aperio WebScope]

In the upper right hand quadrant of this slide is a muscular artery. Note the prominent internal and external elastic lamina, which are stained pink in this slide. The tunica media contains several layers of circumferential smooth muscle mixed with collagen. The tunica adventitia which is slightly thinner than the tunica media grades into surrounding fatty connective tissue.




Webslide 0023A_B: vena cava, monkey, plastic, c.s., H&E
[Aperio ImageScope] [Aperio WebScope]

Compare this cross section of a vessel with Slide 22 from same animal. The original circumference of 10-15 mm is only partly sampled in your slide. Note:

  • Variable intima with some longitudinal fibers, including smooth muscle.
  • Skimpy media (1-3 layers of circular smooth muscle).
  • Thick adventitia with plentiful longitudinal smooth muscle bundles like islands in a sea of collagen, with vasa vasorum, fat cells and extravasated (escaped) blood.




Webslide 0004_B: Femoral artery and vein, monkey, glutaraldehyde perfusion, 1.5 µm GMA section, AF & TB
[Aperio ImageScope] [Aperio WebScope]

            This section of a femoral artery and vein was obtained from a rhesus monkey fixed by intravascular perfusion. The tunica intima, tunica media, internal elastic membrane, and external elastic membrane are well preserved although these laminae are poorly stained. Please ignore the folds that appear in the tunica adventitia that are purely artifactual. Compare the relative size and structure of the two vessels. Compare the appearance of elastic fibers with those in H & E stained 1.5 µm slides 22 and 23.




Webslide 0013_B: Femoral vessels & Nerves, Cat
[Aperio ImageScope] [Aperio WebScope]

This slide contains two muscular arteries and two large veins which have been perfused. One of the muscular arteries is annotated to show key features. In addition, there are several examples of lymphatic vessels on this slide which can look similar to veins. They have thin walls covered in simple squamous epithelium but are more likely to have valves than veins. In this perfused slide, the veins are empty while the lymphatic vessels contain lightly-staining lymph and some cells which are predominantly white blood cells.




Webslide 0098_B:  Urinary Bladder, monkey, H & E

[Aperio ImageScope] [Aperio WebScope]

          Use this section to locate many small and medium sized blood vessels.  Several good examples of arteries, veins, and capillaries can be observed within the dense connective tissue in the upper left region of the slide.   In particular, examine carefully the series of arteries and veins about 50 to 100 mm in diameter that are located about one-third of the way across the slide from the left edge of the section.   Identify as specifically as possible each of these vessels based on the amount of smooth muscle in relation to the vessel diameter.  Also note the valves in one of the veins.



Extra Slides

UMich Slide 42 (mesentery, H&E) WebScope ImageScope
UMich Slide 95M (mesentery, trichrome-elastin) WebScope ImageScope

These mesentery spreads contain numerous excellent examples small muscular arteries and their companion veins. Study the arteries first in slide #42 [example] , and/or #95 (trichrome) [example] . Note the thin intima, the distinct internal elastic lamina (IEL) and the media composed of circularly oriented smooth muscle cells. The media also contains some elastin and abundant “reticular” collagen, as well as specific proteoglycans. There is sometimes a condensation of elastic fibers in the outer portion of the media that may be an “external elastic lamina”, which varies from artery to artery. The adventitia is the dense, irregular connective tissue surrounding the media that varies in thickness. Remember that in blood vessels the components of the media are arranged circularly, while those of the adventitia are oriented longitudinally. In vessels where the media is too thick to be supported by simple diffusion, vasa vasorum (e.g. shown here in slide 95M) may also be observed in the adventitia.

The structure of the companion veins in slide #42 [example] and/or #95 (trichrome) [example] is less regular and may be difficult to understand at first, but still consists of the same basic layers as arteries with a tunica intima, media, and an adventitia, although the media is usually much less muscular and less organized compared to the companion artery. Conversely, the adventitia is usually thicker in veins and may often have some bundles of longitudinal smooth muscle [example] as well as vasa vasorum [example] . In some sections, you may be able to see a thin internal elastic lamina beneath the venular endothelium (particularly in slide #95M).



The following additional Webslides may be used to review this material:

Webslide 0001_B: Mammal artery
[Aperio ImageScope] [Aperio WebScope]

Webslide 0002_B: Human artery and vein
[Aperio ImageScope] [Aperio WebScope]

Webslide 0025_B: Papillary muscle & valve
[Aperio ImageScope] [Aperio WebScope]

Webslide 0150_B: Aorta
[Aperio ImageScope] [Aperio WebScope]

Webslide 0175_B: Abdominal vein
[Aperio ImageScope] [Aperio WebScope]

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Updated 5/14/18 - Carbrey