Blood

Blood• Blood is a fluid connective tissue that

circulate through the cardiovascular system

• Conveying nutrients and oxygen to cells

• Carrying wastes and carbon dioxide away from cells

• Carrying hormones and other regulatory agents to and from the cells

• Having a major homeostatic role

BLOOD CONSISTS OF:FORMED PLASMA, 55%

ELEMENTS, 45%

which include: which include:

Red blood cells Water

White blood cells Proteins

Blood plateles albumin globulins

fibrinogen

Other solutes

Cells and platelets in circulating blood

Red blood cells (erythrocytes)

• Red blood cells constitute the largest number of cells in the blood

(4,5-5,5 mln/mm cub)

• Red blood cells do not have a nucleus

• Red blood cells are specialized for the transport of oxygen and carbon dioxide by means of hemoglobin

White blood cells

White blood cells are motile cells: they leave the circulation and migrate to their site of activity in the connective tissue

Include:

GRANULOCYTES AGRANULOCYTES

Neutrophils Lymphocytes

Eosinophils Monocytes

Basophils

Blood platelets

• Plateles are membrane-bounded, enucleate cytoplasmic fragments of the resident cells of the red bone marrow - megacaryocytes

• Plateles function is blood clotting, clot retraction, and clot dissolution

Hemopoiesis

Origin of connective tissue & blood cells

Prenatal hemopoiesis

• Mesoblastic phase (2-6 weeks of gestation) – within the wall of the yolk sack (umbilical vesicle)

• Hepatic phase (6-38 weeks of gestation) – within the liver of embryo & fetus)

• Splenic phase (12-38 weeks of gestation) – within the spleen of embryo and fetus

• Myeloid phase (from 24 week of gestation through the rest of lifespan) – in the red bone marrow

Postnatal hemopoiesis (myeloid & lymphoid cell lines)

• Stem cells– Pluripotential hemopoietic stem cells (PHSC)– Multipotential hemopoietic stem cells (MHSC)

(colony-forming units: CFU-GEMM + CFU-Ly)

• Progenitor cells – Unipotential cell lines

(colony-forming units: CFU-E, CFU-Meg, CFU-Eo, CFU-Ba, CFU-GMo, CFU-LyT, CFU-LyB)

• Precursor cells

Precursor cells in the formation of erythrocytes and granulocytes