18. Erythrocytes - structural, ultrastructural and functional characteristics. Erythropoiesis.

RBCs are highly flexible and malleable because they can travel in __________ lumina.

narrow capillary

The average lifespan of RBCs in circulation is about __________ days.

120

In men, RBCs make up on average __________% of blood.

45

The typical diameter of RBCs is normally __________ μm.

7-8

The process of producing RBCs is called __________.

erythropoiesis

The red color of RBCs is due to the protein called __________.

hemoglobin

During the final stages of erythropoietic development, RBCs lose their __________ and almost all organelles except the cytoskeleton.

nucleus

The initial stem cell that differentiates into a proerythroblast is called __________.

hemocytoblast

The increased number of erythrocytes is called __________.

erythrocytosis

Microcytes have a diameter of __________ μm.

6

The cytoplasm of the proerythroblast appears deep blue due to the presence of __________.

ribosomal RNA

The nucleus of the orthochromatic erythroblast is described as __________ stained and pyknotic.

densely

The final maturation of erythrocytes occurs in the __________ before being released into the circulation.

bone marrow

life span of eryhtrocytes

120 days

number of RBC men and women

men - 4.1-6.1 × 10¹²

women - 3.8-5.5 × 10¹²

final stages of erythropoietic development

RBC lose nucleus adn almost all organelle except cytoskeleton enter the circulation

size of RBC

2.3-2.6um thick

7-8um diameter

microcyte - 6um

macrocyte - 9um

megalocyte - 12um

increase and decrease of erythrocytes

increase = erythrocytosis

decrease = erythropenia

describe initial stem cell hemocytoblast till end

• differentiates into a large, round proerythroblast with a diameter of 15-30um, has a deep blue cytoplasm due to rRNA

• erythroblast divides into 2 smaller 10-18um basophilic erythroblasts, which have an intensely basophilic cytoplasm with more heterochromatic nucleus

• ribosomes still synthesise more haemoglobin

• basophilic erythroblast undergo 2-3 cell divisions forming polychromatic erythroblast with a diameter of 10-12um, grey bit of cytoplasm is due to the build-up of haemoglobin and decrease in ribosomes, nucleus has condensed chromatin no nucleoli

• higher haemoglobin content the cytoplasm becomes eosinophilic and the cell is orthochromatic erythroblast whichi s 8-10um small densely stained pyknotic nucleus

• after extrusion of nucleus and loss of all organelle the cell becomes biconcave and has a diameter of 7-10um to make erythrocyte

• erythrocyte remain in the bone marrow for 2-3 days until they fully mature then released into the peripheral circulation

ribosomes for

synthesis of haemoglobin

result of erythropoiesis

synthesis and accumulation of haemoglobin, extrusion of nucleus and decrease in cell volume