Blood is a connective tissue with a fluid matrix called plasma. Three basic types of cells are found suspended in plasma:The Erythrocytes (red blood cells) are pink with a light center (where the cell is thinner and the light shines through).onnective tissue fibers, blood vessels, and sweat glands can be seen embedded in the adipose tissue. As the photomicrograph illustrates this tissue consists of adipocytes that contain lipid droplets. Adipose Tissue: 1  Description: Resembles a chicken-wire fence.
It is possible that hypofunctional 5-HTP cells (reflecting TPH1 dysfunction) in the periphery, leading to deficient 5-HTP, low 5-HT, and concomitant compensatory TPH2 activation in the brain, may cause endogenous depression.
In the 1960s, the catecholamine hypothesis was a popular explanation for why people developed depression. This hypothesis suggested that a deficiency of the neurotransmitter norepinephrine (also known as noradrenaline) in certain areas of the brain was responsible for creating depressed mood.