9 Difference between Sinusoids and Capillaries (With Table)

Blood circulation in living organisms plays a vital role to enhance their survival. The blood circulatory system comprises blood, the heart, and circulatory mediums. 

The main circulatory mediums in living organisms are veins, arteries, capillaries, and more. Blood circulation helps in the nourishment of tissues and the removal of waste products. 

Sinusoids and capillaries help in the transport of oxygen and nutrients in organisms. They also help in the removal of metabolic wastes in the tissues. 

So, what is the main difference between sinusoids and capillaries? The former has a discontinuous incomplete basal membrane while the latter has a continuous and complete basal membrane. 

This article provides further differences between sinusoids and capillaries in a tabular form. Take time to read through and get to know the sinusoid anatomy. 

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Comparison Table (Sinusoids vs Capillaries)

Basic Terms  Sinusoids  Capillaries 
Description  Refers to small and irregular-shaped blood vessels found in certain organs. Refers to fine branching blood vessels in the body. 
Correspondence  Discontinuous capillaries Continuous capillaries 
Occurrence  Liver, adrenal gland, spleen, and bone marrow Skin, skeletal muscles, gonads, and renal glomerulus. 
Lumen  Larger and wider  Relatively smaller and narrower. 
Basal Membrane  Incomplete basal membrane  Complete basal membrane 
Pores Open pores  Covered posters 
Structure  Special fenestrated capillaries with larger openings on the endothelium cell. Single-layer of endothelial cells supported by a basal membrane. 
Diameter  30–40 µm 5-10 µm
Function  Allow passage of serum, red and white blood cells. Allow passage of small molecules but not blood cells and serum.

What Are Sinusoids?

Sinusoids are larger types of capillaries with large gaps between endothelial cells and incomplete basal lamina. Sinusoids are completely permeable to allow the passage of nutrients and blood cells. 

Sinusoids occur in the adrenal glands, liver, spleen, and bone marrow. These sinusoids have a lumen diameter of 30–40 µm with open-pore capillaries. 

Sinusoids are also known as discontinuous capillaries due to incomplete basal lamina. Sinusoids in the liver serve as a place of mixing oxygen with nutrients. 

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What Are Capillaries?

Capillaries are the smallest blood vessels in the body with one thick cell supported by a basal lamina. They are responsible for transporting blood between arterioles and venules. 

The main role of capillaries is to exchange numerous substances with the intestinal fluid environment. 

Capillaries are divided into fenestrated capillaries, continuous capillaries, and discontinuous capillaries or sinusoids. 

Continuous capillary has a lumen diameter of 5-10 µm. It mainly occurs in the skeletal muscles, skin, fingers, gonads, and other organs. 

The main role of the capillary is to transport oxygen and glucose. It also helps in the removal of carbon dioxide, uric acid, urea, lactic acid, and creatinine. 

Fenestrated capillaries occur in endocrine glands, pancreas, intestines, and glomeruli of the kidney. The opening pore on the endothelial cells is the main feature of capillaries. 

These open pores on capillaries are covered with diaphragms to limit the size of molecules from passage via the capillary wall. 

Fenestrated capillaries in the renal glomerulus are not covered with the diaphragm. But these capillaries are covered by podocyte cells to act as diaphragms. 

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Main Difference between Sinusoids and Capillaries

  1. Sinusoids occur in the organs while capillaries in the skin and skeletal muscles. 
  2. Sinusoids are discontinuous capillaries while capillaries are continuous, fenestrated, and discontinuous.  
  3. Sinusoids have larger and wider lumen while capillaris have smaller and narrower lumen.
  4. Sinusoids have discontinuous basal lamina while capillaries have continuous basal lamina. 
  5. Sinusoids have open pores while capillaries have pores covered by the diaphragm.

Similarities between Sinusoids and Capillaries

  1. Both are types of blood vessels. 
  2. Both occur inside organs and tissues. 
  3. Both have endothelial cells supported by a basal lamina. 
  4. Both are classified based on the structure of endothelial cells. 
  5. Both facilitate the exchange of nutrients and wastes between blood and organs. 

In Conclusion

Sinusoids are special types of capillaries marked by large open pores between endothelial cells and discontinuous basal membranes. They occur in the liver, spleen, and bone marrow. 

Capillaries are blood vessels that transport oxygen and nutrients. They also help in the removal of metabolic wastes such as lactic acid, uric acid, urea, and carbon dioxide. 

The main difference between capillaries and sinusoids is based on structure, occurrence, and function. Capillaries occur in the skeletal muscles, skin, and gonads. 

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