Cardiovascular System: Blood Vessels -nsu

Histology 7a Gregory Rodocker NSU Class Taken: Spring 2009

The Circulatory System 

Blood vascular components    

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Heart Arteries Capillaries veins

lymphatic vascular components 

later

Vessels 

Macrovasculature (>0.1 mm)   

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Large arterioles Muscular and elastic arteries Muscular veins

Microvasculature   

Arterioles Capillaries Post-capillary venules

Capillaries 

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A single layer of endothelial cells and the basal lamina: (no smooth muscles) 7-9 µm in diameter and 50 µm in length Walls consist of 1-3 cells with a continuous basal lamina of endothelial origin

Types of Capillaries    

Continuous, complete or somatic Fenestrated, or visceral Fenestrated in Kidney Discontinuous sinusoidal 

Listed from tightest to leakiest

Fenestrated Capillary in Kidney

Continuous Capillaries   

Absence of fenestrae Basal lamina continuous Muscle tissue, CT, exocrine glands and NT

Fenestrated Capillaries 

Large fenestrae covered by diaphragm 

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Thinner than the trilaminar appearing unit membrane

Basal lamina continuous Kidney, intestines and endocrine glands

Fenestrated Caps. in Kidney  

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Fenestrated w/o diaphragm Basal lamina continuous and only barrier for filtration Kidney glomeruli

Discontinuous Sinusoidal Capillaries (sinusoidal so think liver)  

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Wall and basal lamina discontinuous Tortuous in their path and greatly enlarged (30-40 µm in diameter) Liver and hematopoietic tissue such as bone marrow and spleen

1- typical path 2- arteriovenous anastomosis 3- arterial portal system 4- venous portal system

Larger vessels 

Tunica intima  

Endothelium Internal elastic lamina (arteries) 

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Tunica media  

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Wrinkled postmortem

Smooth muscle External elastic lamina (larger arteries)

Tunica externa 

CT which is continuous with surrounding tissues

Larger vessels 

Vasa vasorum 

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Vessels supplying blood to walls of larger blood vessels. Walls too thick to obtain nutrition from large vessel lumen. “vessels of the vessels”

Muscular vs. elastic artery

Muscular vs. elastic arteries   

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Media of muscular with up to 40 layers of smooth muscle cells Elastic arteries include the aorta and its large branches Elastic arteries have a large lumen and thin walls vs. muscular arteries which have small lumens and thick walls Elastic vessels recoil with beat of the heart while muscular arteries control

Veins 

Small to medium sized veins (1-9 mm in diameter) 

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Thin intima, thin media and well developed adventitia

Large veins have an obvious intima, thin media and a prominent adventitia 

Contain valves to prevent blood back flow

Muscular artery vs. comparable vein