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Arterioles

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Arterioles, because they are so numerous, are the main control of blood pressure.

Tunica Externa

Present and unremarkable.

Tunica Media

Largest tunic present

Tunica Interna (Intimia)

Simple squamous epithelium

Lumen

The lumen of an arteriole is usually round.  These usually don’t become distorted into an oval shape due to the processes used to make the slide.  Few erythrocytes (red blood cells) are in the lumen.

Microscopic image of arteriole stained using Verhoeff's technique. The arteriole is centrally positioned, exhibiting a concentric, dark-red wall and a clear lumen densely packed with small, red erythrocytes. The background consists of lighter-stained connective tissue elements, with unstained areas surrounding the arteriole. The staining accentuates the elastic laminae within the arteriole wall, revealing structural details. The resolution is high, and depth of field is shallow.
Figure 1: Cross-section of an arteriole with Verhoeff stain, showing red blood cells within its lumen.
Histological slide of adrenal gland tissue stained with H&E. Prominent arteriole with dark purple nuclei lining the vessel wall, surrounded by concentric layers of pink-stained smooth muscle. Several capillaries are visible amidst a background of adipocytes and collagenous tissue. Overall color palette is dominated by pinks and purples indicative of the H&E staining procedure.
Figure 2: Arteriole and capillary in adrenal gland tissue.
Light micrograph image of adipose tissue stained with H&E, highlighting an arteriole and adjacent venule. The arteriole appears as a small, circular structure with multiple layers stained intensely eosinophilic. The venule, situated nearby, exhibits a larger lumen and less defined wall. The background consists of adipocytes with clear cytoplasm and peripherally located nuclei; all are arranged in a non-uniform pattern against a white background.
Figure 3: Microscopic view of an arteriole and venule in adipose tissue, stained pink. Shows circular vessels surrounded by fat cells.

Figure 1: Slide 303 Artery & vein, Verhoeff stain,
Figure 2: Adrenal gland, human, H&E, 40X Slide 230
Figure 3: Slide 95 Small arteries and veins, H&E, 20X.
All by University of Michigan Histology, licensed under CC BY-NC-SA 3.0.

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Elastic Arteries
Muscular Arteries
Arterioles
Sinusoidal Capillaries
Fenestrated Capillaries
Continuous Capillaries
Venules
Veins

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