Units in Biology

Biologic Units

The Common Vein Copyright 2007

The Cell

The cell

The cell is the building block of all biological structure.  In this image a few polygonal cells of the liver are attached together.  Each cell has a central dark nucleus which is embedded in a pinkish cytoplasm. The nucleus takes up approximately 1/5 to 1/6 of the volume of the cell.  (Image courtesy of Barbara Banner M.D.) 13440

The Tissue

Cells Align and Combine – Sinusoids – Shapes – New Unit – Tissue

The cells of the liver are organized in cords and plates and are organized like spokes of a wheel  around the central vein. The plates and cords are lined by the sinusoids which are the channels which carry blood to the liver.  Just below the sinusoids, between the wall of the sinusoid and the capsule of the liver there is a space called the space of Disse which carries the lymphatic fluid of the liver.   (Image courtesy

Tissue Units

Tissue Aligns and Combines – Shapes – New Unit – Lobule

The sinusoids and hepatic cords combine to form a liver lobule which is a functional and structural unit of the liver.  At the center of the lobule is the central vein from which emanate many cords of liver tissue.  At the periphery of the lobule there are 4-5 groups of portal triads consisting of distal branches of the portal vein (dark blue), hepatic artery (red) and biliary radicle (green).  They create the border of the lobule.

(Image courtesy of Ashley Davidoff M.D.) 13009 W


Lobules Align and Combine – Shapes Up – New Unit – The The liver

The lobules of the liver combine to form lobes.  The liver has two lobes.  In this anatomical specimen the right lobe is seen on the left side of the image lateral to the stone containing gallbladder, while the left lobe is seen with the branching potal triad surrounded by the whitened connective tissue. on the right side of the image.   (Image courtesy of Ashley Davidoff M.D.) 13456


Liver aligns and Combines – Shapes Up – New Unit – The Abdomen
45920.800 Courtesy Ashley Davidoff MD

Body Parts

Completing the Abdomen – surrounding skin

45883.800 Courtesy Ashley Davidoff MD


The Body – Parts and the whole

I came across this man in a store window in Washington DC I think in the spring of 1983 and it brought to mind the idea of the concept of the parts making up the whole.  I show it in the context of the discussion for some light relief.  Courtesy Ashley Davidoff MD 22392 02006p03


The Young Adult – with the bigger picture in the background – part of a team



The Couple

82835p.800b01 couple nude man woman TCV oneness Davidoff art

The Family

The Wedding  – The Family

A large family wedding with 12 children. Note the complexion of the groom is completely different to bride’s and her family. Genetics goes deeper than we know, and the good and the bad surface t intermittantly. However there is no telling when this will occur or become phenotypic.

Davidoff phtography. 68494


Different Groups of People

A collage of some of the people of South Africa. In this image there is a slight male predominance. Davidoff photography. 57728c



0063.800 Peru food eating restaurant Davidoff photography Davidoff MD

 The City

The City

61855 Boston Zakim bridge government centre nucleus Davidoff photography



Map of Europe showing with Sweden in red. There is a high incidence of sarcoidosis in the Swedish population. 54454 Image from infoplease.com http://www.infoplease.com/atlas/ 54454

Mother Earth

The Earth – An apparrent independant unit – but little does it know

54954 Courtesy of NASA – National Space Science Data Center