how dowhite blood cells originate from yellow and red marrow?

Answer 1

In the bone marrow there is a kind of connective tissue of the type reticular connective tissue.
This tissue can be divided into two types: Erythropoietic tissue( forming red bone marrow) and leucopoietic tissue(forming white bone marrow). The cells of the former divide mitotically to give rise to erythroblasts which differentiate finally into erythrocytes.This process is called hemopoiesis.
Leucopoietic tissue on the other hand divide mitotically to finally give rise to white blood cells and they in turn differentiate into various types of white blood cells.
In the lymph glands there is also a reticular connective tissue whose cells divide mitotically to give rise to lymphocytes.
Formation of white blood cells is called leucopoiesis

Answer 2

Leukocytes (white blood cells) originate in the bone marrow and lymph tissue. White blood cells are actively engaged in the destruction or neutralization of invading micro-organisms and are then transported to sites of infection and inflammation. For this reason, their life span in the blood in usually very short (a life span of up to 14 days). When infection is present their number are greatly increased and they also become more mobile and move back and forth between the blood, lymph, and tissues.

White blood cells come in various shapes and sizes:

Granular appearing white cells are known as Neutrophils, which make up about two thirds of all white blood cells; Eosinophils which make up about 2 to 4 percent of the white cell count; and Basophils - which make up less than 0.5 per cent of the white cell count.

Non-granular appearing white cells are known as Lymphocytes. These are the natural killer cells and make up about 25-30% of all white blood cells. Two types of lymphocytes T's and B's are involved in immunity.
Red blood cells, most white blood cells, and platelets are produced in the bone marrow, the soft fatty tissue inside bone cavities. Two types of white blood cells, T and B lymphocytes, are also produced in the lymph nodes and spleen, and T lymphocytes are produced and mature in the thymus gland.

Within the bone marrow, all blood cells originate from a single type of unspecialized cell called a stem cell. When a stem cell divides, it first becomes an immature red blood cell, white blood cell, or platelet-producing cell. The immature cell then divides, matures further, and ultimately becomes a mature red blood cell, white blood cell, or platelet.

The rate of blood cell production is controlled by the body's needs. Normal blood cells last for a limited time (ranging from a few hours to a few days for white blood cells ) and must be replaced constantly. Certain conditions may trigger additional production of blood cells.
The bone marrow produces and releases more white blood cells in response to infections.

Answer 3

White blood cells or leukocytes are cells of the immune system which defend the body against both infectious disease and foreign materials. Several different and diverse types of leukocytes exist, however they are all produced and derived from a pluripotent cell in the bone marrow known as a hematopoietic stem cell. Leukocytes are found throughout the body, including the blood and lymphatic system.

There are two types of bone marrow: red marrow (also known as myeloid tissue) and yellow marrow. Red blood cells, platelets and most white blood cells arise in red marrow; some white blood cells develop in yellow marrow. The color of yellow marrow is due to the much higher number of fat cells. Both types of bone marrow contain numerous blood vessels and capillaries.

At birth, all bone marrow is red. With age, more and more of it is converted to the yellow type. Adults have on average about 2.6 kg of bone marrow, with about half of it being red. Red marrow is found mainly in the flat bones such as hip bone, breast bone, skull, ribs, vertebrae and shoulder blades, and in the cancellous ("spongy") material at the proximal ends of the long bones femur and humerus. Yellow marrow is found in the hollow interior of the middle portion of long bones.

In cases of severe blood loss, the body can convert yellow marrow back to red marrow in order to increase blood cell production.
Bone marrow contains two types of stem cells:

Hematopoietic stem cells give rise to the three classes of blood cell that are found in the circulation: white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes).
Mesenchymal stem cells are found arrayed around the central sinus in the bone marrow. They have the capability to differentiate into osteoblasts, chondrocytes, myocytes, and many other types of cells. They also function as "gatekeeper" cells of the bone marrow.