Thymus  is  the  organ  of  lymphopoiesis  of  humans  and  many  species  of 
animals, in which maturation occurs. This article presents the results of morphometric studies of 
red bone marrow in different regions of Kyrgyzstan. The structure (macroscopic picture) of the 
thymus was studied on 21 corpses of children of the first period, childhood of the second period 
of  adulthood.  Used  anatomical  methods  (preparation,  measurement)  and  histological  methods 
(stained  with  hematoxylin-eosin,  according  to  Van  Gieson).  Using  histological,  morphometric 
methods, it was found that age-related transformations of the tissue structure of the thymus are 
characterized by the development of fibrous connective and adipose tissue in the cortical septa, 
which leads to fragmentation of the cortical substance, and then to the separation of fragments of 
the cortical and brain substance. The greatest progression of the processes of involution in the 
thymus  is  noted  during  the  second  mature  age  period  from  36  to  60  years.  The  problems  of 
changing the functions of the immune system during aging are analyzed. Age-related changes in 
the  relative  areas  of  the  structural  elements  of  the  parenchyma  and  thymus  stroma  are 
established. The thymus consists of lobules, in which there are zones: the inner, lighter brain and 
the outer darker cortical. Located in the center of the light zones and on their periphery  - dark 
zones. In the darker, cortical zone, the cells are very densely located, their number is much larger 
than  in  the  center  of  the  medulla  zone.  
  In the thickness of the cerebral layer there are single Gassal bodies, blood capillaries, 
lymph gaps. The cortical layer consists of lymphoid elements, very densely located, with mitoses 
in individual cells. In the second mature age, iron acquires an inhomogeneous structure due to 
age-related  involution.  The  problems  of  changing  the  functions  of  the  immune  system  during 
aging are analyzed.  
  In  the  second  mature  age  d,  in  contrast  to  the  first  period  of  childhood  thymus,  the 
number  of  connective  tissue  fibers  decreases.  In  the  second  mature  age,  the  number  of 
lymphocytes  in  the  thymus  decreases.  Adipose  tissue  predominates  in  the  parenchyma  along 
with connective tissue. During this period, the lobules are reduced to narrow bands and bands. In 
the  second  mature  age,  iron  is  represented  by  adipose  tissue  and  thin,  randomly  scattered 
parenchyma cords. structural changes in the capsule of the gland; the structure of the cortical and 
medulla; violation of loose fibrous connective tissue and blood vessels of an organ. 
  The histophysiological characteristic of the thymus was studied, which showed that 
those living in the city of Kara-Balta, located near the uranium tailing dump, lead to an increase 
in involutive organ changes due to increased death of thymocytes and a decrease in their 
proliferative activity.