Histology of the Blood

Question 1

Constituents of Blood

Answer 1

Plasma

Serum

Question 2

Plasma (makes up 56%- other44% is blood))

Answer 2

Plasma is blood minus the cells and comrpisises of

Water
Salts and minerals
Plasma proteins (albumins, globulins, fibrinogen)
Hormones
Signal molecules
Clotting factors dissolved in water

Question 3

Serum

Answer 3

Serum is plasma minus the clotting factors

Question 4

Erythrocytes

Answer 4

4-6 million per mL blood

Lifespan of 4 months

Produced in the liver (fetus) and bone marrow

Enucleate, boconcave discs aprrox 6.5-8.5 micrometres in diamtere (180 km end to end). Slightly larger in diameter than very smallest of capillaries

Major protein is haemoglobin

Destroyed in the liver and spleen after 120 days

Cell membrane has important endoskeleton attached (major protein- spectrin) to maintain cell shape

Question 5

3 categories that white cell series (Leucocytes) are divided into

Answer 5

Granulocytes (contain visible granules)

Agranulocytes (no visible granules)

Platelets (cell fragments)

Question 6

Which are most common types of Leucocytes?

Answer 6

Granulocytes are more common than arganulocytes

Question 7

Neutrophils (polymorphonuclear leucocytes)

Answer 7

Commonest white blood cell and commonest granulocyte

Question 8

Structure of neutrophils

Answer 8

Multi lobed nucleus

Granular cytoplasm

12-14 micrometres in diamtere (larger than red blood cells)

Question 9

Role of neutrophils

Answer 9

Primary phagocytes- engulf and destroy bacteria and other foreign macromolecules. They do this by using the respiratory burst

Due to this function the cytoplasm contains the enzyme myeloperoxidase in order to conduct respiratory burst

Question 10

What tye of cells are neutrophils?

Answer 10

Mobile and motile cells- they can circulate in blood and also invade through the walls of the blood vessels and through the glycosaminoglycan matrix of the tissues

Question 11

What 3 types of cytoplasmic granules do neutrophils contain when seen using the nked eye/light microscope?

Answer 11

Primary granules

Secondary granules

Tertiary granules

Question 12

Primary granules

Answer 12

Are lyzosomes

These contain the enzymes myeloperoxidase and acid hydrolases

Question 13

Secondary granules

Answer 13

Contain specific granules that are secreted to mobilise inflammatory mediators

Question 14

Tertiary granules

Answer 14

Contain gelatinases which break down proteins and adhesion molecules which break down proteins and adhesion molecules

These substamces are necessary to aid the neutrophil in its passage out of blood vessels and through tissue.

Question 15

Eosinophils numbers/commoness

Answer 15

Makes up 1% of total number of white cells

Numbers increase in parasatic infections

Question 16

Structure and size of eosinophils

Answer 16

12-17 micrometres in diameter

Bi-lobed nucleus

Distinctive large red cytoplasmic granules with crystaline inclusions

Question 17

Role of eosinophils

Answer 17

-Play a role in phasgocytosis and in our response to parasites and in our response to other allergens

As they are phagocytic with partciular affinity for antigen/ antibody complexes

-They have an antagonistic action to basophils and mast cells
They inhibit mass cell secretion
They neutralise histamine- therefore restricting inflammatory responses

Question 18

Structure of eosinophils in electron microscopy

Answer 18

Contain characteristic lozenge-shaped granules with crystalline cores

Bare recpetors for immunoglobulin E on their surface.

Question 19

Basophils structure and size

Answer 19

Rare as they make up 0.5% of white cell series

14-16 micrometres in diameter

Bi lobed nucleus and prominent dark blue-staining cytoplasmic granules

Granules contain histamine

Basophils are another from, circukating form, of the tissue mast cell.

They have receptors for IgE

Question 20

Role of basophils

Answer 20

Involved in inflammatory reactions and act to prevent coagulation and agglutination

Release histamine and vaso-active agents in response to allergens
This results in immediate hypersensitivty reactions, also known as anaphylaxis

Question 21

Two types of lymphocytes

Answer 21

B cells

T cells

Question 22

B cells

Answer 22

Become plasma cells and secrete antibodies

Question 23

T cells

Answer 23

Are involved in cell-mediated immunity

Question 24

Structure of lymphocytes

Answer 24

Very small cells- approx 10 microns in diameter

They appear on light microspcopy with almost all nucleus

The central haemotoxyphilic nucleus is surrounded by a very thin rim of cytoplasm, almost clear (greyish blue colour) with very few organelles wuthin it

Question 25

B cells and T cells can be split further

Answer 25

B cells- produce antibodies

T Helper (TH) cells- help B cells and activate macrophages

T Cytotoxic (TC) cells- kill previously marked target cells

T Suppressor (TS) cells- supress TH cells and hence suppress the immune response

Natural Killer (NK) cells- mainly kill virus infected cells

Question 26

Monocytes- strcuture and size

Answer 26

Immature cells, circulate briefly in blood

Characteristic reniform/kidney bean shaped nucleus

15-20 micrometres in diameter

Differenciate into one of several cell types within tissue

Although monocytes are classified as non- granulated, they do contain small cytoplasmic granules, mostly lysosomes

Question 27

Role of monocytes

Answer 27

Major phagocytic and defensive role

Some become antigen presenting cells, passing antigen fragments to lmphocytes

Question 28

Monocytes can differenciate into:

Answer 28

Tissue macrophage- everywhere

Kupffer cells- liver

Osteoclasts- bone, play a role in absorbing bone

Antigen presenting cells- everywhere

Alveolar mecrophages- lung

Question 29

Platelets- what are they and structure?

Answer 29

Fragments of cells derived from large multi-nucleated Megakaryocytes in the bone marrow

1-3 micrometres in diameter, surrounded by cell membrane and containing vesicles with coagulation factors.

Question 30

Role of platelets

Answer 30

Responsible for clotting of blood, particularly when the endothelium lining all blood vessels is breached

Question 31

Hematopoiesis in humans

Answer 31

Blood cells derive from a single common stem cell that gives rise to 2 broad lineages/ 2 daughter cells

Question 32

Haematopoiesis in adults

Answer 32

In adults, all blood cells form in the haematopoeitic bone marrow

However, in children this process begins in fetal life in the liver

Question 33

Erythropoeisis

Answer 33

Erythropoeisis is characterised by a gradual reduction in cell size from the proerythroblast to the reticulocyte (these are the cells just before the production of red blood cells)

1-As the cell matures theres an increase in the prodcution of haemoglobin in the cytoplasm

2-Theres a gradual loss of organelles from the cytoplasm

3-In the early precursors of erythrocytes they are basophilic and this then changes to eosinophilia in late precursors as the amount haemoglobin in the cytoplasm increases

4-Loss of nucleus

5-Mediated by the hormone erythropoeitin (EPO) produced in kidney

Question 34

Granulopoeisis

Answer 34

Morphology similar for neutrophils, eosinophils and basophils

Bone marrow holds a large pool of stored mature neutrophils that can be released into the circulation during times of infection

There is no stored pool of monocytes and lymphocytes precursors complete their maturation at other sites, either in lymph nodes or in the thymus

Question 35

This process of Granulopoeisis is characterised by

Answer 35

-an increasing number of granules

-incrwasingly complex shape of nucleus

Question 36

Which is the only type of mature blood cell is capable of cell division?

Answer 36

lymphocytes