Question

CHECKPOINT 3-1 Describe the bone marrow stromal location of erythrocyte, granulocyte, platelet, and lymphocyte differentiation.

Answer 1

BONE MARROW:

spongy tissue inside some of the bones such as hip and thigh bones is called bone marrow. It contains stem cells. Stem cells can develop into red blood cells, white blood cells and platelets

FUNCTIONS:

--generate bone cells

2types of stem cells are present

1-HAEMATOPOIETIC CELLS --production of rbc

2-MESENCHYMAL CELLS--produce blood cell components like fat, cartilage, fibrous connective tissue, stromal cells that support blood formation

  ERYHTROCYTIC DIFFERENTIATION

It is a process in which myeloid precursor cell acquires specialized features of erythrocytes

It's a process in which erythrocytes matures from a haemocytoblast into full blown erythrocytes

8 stages are involved out-of which 7stages occur in bone marrow. After 7th stage cell is then released in to blood stream as reticulocyte where it matures 1-2days later into erythrocyte

1.Haemocytoblast --pluripotent haematopoietic stem cell

2.Myeloid progenitor--multipotent haematopoietic stem cell

3.Unipotent stem cell

4.pronormoblast

5.Basophilic normoblast

6.polychromatophilic normoblast

7.ortho chromatic normoblast

8.reticulocye

GRANULOCYTIC DIFFERENTIATION

Stem cell Committed cell Developmental pathway- Phase 1 Phase 2 Ribosome synthesis Hemoglobin accumulation Phase 3 Ejection of nucleus Early Late Hemocytoblast Proerythroblast erythroblast erythroblast Copyright © 2001 Benjamin Cummings, an imprint of Addison Wesley Longman, Inc. Normoblast Reticulocyte Erythrocyte

Granulocytes are a category of leukocytes characterised by presence of granules in their cytoplasm

Granulocytes originate from stem cells in bone marrow

3types of Granulocytes are present

1.Neutrophils

2.eosinophil

3.Basophils

NEUTROPHILS::

found in blood and their function is to help in innate immunity

BASOPHILS:

large granules containing histamine, proteoglycans, proteolytic enzymes, lipid mediators, and cytokines

They help in defending against parasites and play an active role in allergic reactions

ESINOPHILS::

Located in tissues and not in peripheral blood

Differentiate from myeloid precursor cells

Function is to help in innate immunity and to fight against parasites and viruses

   PLATELET DIFFERENTIATION.

Produced in bone marrow same as RBC and WBC

Thrombopoitein-----a hormone produced by liver or kidneys stimulates megakariocyte (very large cells of bone marrow) differentiation and platelet release

Platelets are formed when cytoplasmic fragments of megakariocytes pinch off into circulation as they age

They are stored in spleen

Some evidences show that platelets may also be produced in lungs where megakariocytes are frequently found

Platelets destruction begins when antibodies coat platelets. These sensitised platelets are then destroyed by macrophages Mostly from spleen but also from liver

Platelets are also called thrombocytes

FUNCTION ::

PLATELETS along with coagulation factors help in hemostasis

LYMPHOCYTIC DIFFERENTIATION.   

Formation of lymphocyte is called lymphopoiesis

Lymphocytes are mature, infection fighting cells that develop from lymphoblasts a type of blood stem cell in bone marrow (sub type of WBC)

3types of lymphocytes are there

1.NATURAL KILLER CELLS---CELL MEDIATED CYTOTOXIC INNATE IMMUNITY

2.T-CELLS--CELL MEDIATED CYTOTOXIC ADAPTIVE IMMUNITY

3.B CELLS--HUMORAL, ANTIBODY DRIVEN ADAPTIVE IMMUNITY

ALL lymphocytes originate from a common lymphoid progenitor and then differentiate into their lymphocyte type

B cells mature into B Lymphocytes in Busaequivalent which is thought to be in Peyerspathes of intestines

T cells migrate to and mature in a distinct organ called thymus

Following maturation lymphocytes enter the circulation and peripheral lymphoid organs (eg:spleen and lymph nodes) where they wait for invading pathogens and or or tumour cells

Lymphocyte involved in adaptive immunity differentiate further after exposure to an antigen they form effectorand memory lymphocytes