19. Granulocytes - types, structural, ultrastructural and functional characteristics. Granulocytopoiesis

Granulocytes are a form of leukocytes which contain __________ in their cytoplasm.

specific granules

Neutrophils are __________ in shape and __________ in size.

spherical; 10-12μm

Neutrophils constitute __________ of the leukocyte count.

55%-65%

The nucleus of neutrophils has a __________-like pattern and has __________ lobes connected by fine chromatin strands.

clump; 3-5

In females, neutrophils often have a small __________-shaped lobe called the Barr body, which is __________ in males.

drumstick; absent

The cytoplasm of neutrophils contains __________ granules that stain reddish/purple.

Azurophilic

Neutrophils have a lifetime in the blood of __________ and in connective tissue it is __________.

12 hours; 1-4 days

The main function of neutrophils is __________, where they engulf bacteria, cell debris, and foreign matter.

phagocytosis

Eosinophilic granulocytes have a size of __________ and their nucleus has __________ lobes shaped like a telephone handle.

12-17μm; 2

Eosinophils make up __________ of the leukocyte count.

2%-4%

Eosinophils stain __________ and contain granules that secrete __________, which inactivates histamine.

red; histaminase

Basophils account for __________ of the leukocyte count.

0.1-1%

Basophils have an irregularly shaped nucleus with __________ lobes.

no

Basophils contain large basophilic granules that contain __________, __________, and __________.

histamine; serotonin; heparin

Granulocytopoiesis occurs in the __________ and takes __________ days.

bone marrow; 14-18

WBCs originate from __________, and the process starts with the nucleus becoming flat and indented, and then smaller and lobulated.

hemocytoblasts

Myeloblasts give rise to __________ and have a __________ nucleus and basophilic cytoplasm.

promyelocytes; large, round

Myelocytes have pale, lightly basophilic cytoplasm; their nucleus is pushed off to the __________ of the cell.

side

Myelocytes mature into __________, which then develop into __________ and finally into their specific granulocytes.

metamyelocytes; band cells

what are granulocytes?

form of leukocytes which contain specific granules in their cytoplasm and a lobed nucleus : neutrophils, eosinophils and basophils

neutrophils

spherical in shape and 10-12um in size

55-65% leukocyte count

nuclus has a clump-like pattern with 3-5 lobes connected by fine chromatin strands

older cells have darker-stained lobes

Barr body

an inactivated X chromosome found in female cells, visible as a small, dense mass in the nucleus drumstick-shped lobe

neutrophil granules types

have 2 types of granules : azurophilic that stain red/purple and are primary lysosomes containing peroxidase and hydrolytic enzymes, and specific granules that stain light pink and contain enzymes like alkaline phosphatase.

neutrophil description

• azurophilic and specific granules

• contain golgi complex, ER, mitochondria nad glycogen deposits

• actively motile and function outside the circulation

• lifetime in blood is 12 hours, in connective tissue 1-4 days

• main function is phagocytosis, and numbers increase in bacterial infections

eosinophils description

• spherical with 12-17um

• nucleus has 2 lobes

• make up only 2-4% of leukocyte count

• stain red and granules have hydrolytic enzymes

• secrete histaminase which inactivates histamine produced by basophils and mast cells

• contain golgi, mitochondria, ER, ribosomes

• lifetime in blood 6-10 hours, lifetime in connective tissue 6-10 days

• main function is to destroy parasite via phagocytosis and neutralise

• histamines, number increase in allergic reactions, decrease when patient takes a drug

basophils description

• least in number only 0.1-1% of leukocyte count

• 10-12um in diameter

• nucleus is irregular and no lobes

• have large basophilic granules with histamine, serotonin and heparin

• participate in allergic reactions

granulocytopoiesis

hematopoiesis of granulocytes, occurs in the bone marrow and takes 14-18 days

WBC from hemocytoblasts and the process starts with the nucleus becoming flat and indented, then small and lobulated, cytoplasm accumulates specific and non-specific

3 populations arise : myeloblasts, promyelocytes, myelocytes with either proliferative or mitotic potential

myeloblasts

large, spherical 12-18um

basophilic cytoplasm lacks specific granules but contains lots of ribosomes, large round nucleus containing chromatin and several nucleoli and is the earliest recognizable precursor in granulocytopoiesis. They give rise to promyelocytes.

promyelocytes

divide and give rise to myelocytes, which are smaller so myeloblasts → promyelocytes → myelocytes

myelocytes

pale, light basophilic cytoplasm, nucleus is to the side

neutrophilic, basophilic and eosinophilic myelocytes appear

myelocytes of the 3 cells develop into band cells and into their specific granulocytes