Principles Histology Blood cells Flashcards
What is the distribution of blood in the body?
Capillaries: 10% Peri-arteries: ~20% Heart and lungs: ~20-25% Peri-veins: ~70-75% Adult blood: ~4.5-6L
What is the proportion of formed elements and plasma?
Formed elements: 45%
- RBC > PLT & WBC (Buffy coat)
Plasma: 55%
- Water ~90%
- Proteins (mostly Ig, albumin, clotting factors)
- Nutrients/ salts
What is the difference between plasma and serum?
Plasma has clotting factor while serum does not
What is the breakdown of WBC?
Agranulocytes:
- Lymphocytes (20-50%)
- Monocytes (1-5%)
Granulocytes:
- Neutrophils (~40-75%)
- Eosinophils (5%)
- Basophils (0.5%)
What are RBCs?
AKA erythrocytes.
Have biconcave disc
7um diameter
Deformable bags with 1/3 volume taken up by Fe-containing Hb
Network of flexible cytoskeletal elements to deform and slip through capillary network
Mature: No organelles, no nucleus
Immature: Reticulocytes (newly released into bloodstream) - remnants of ribosomes present
What is the circulation lifespan of RBC?
4 months. Removed by liver/ spleen.
Life span increases after splenectomy.
What are Neutrophils?
Most common type of WBC with many granules in the cytoplasm.
Has prominent multi-lobed nucleus and a bar-body in females. (PMNs)
It circulates in inactive state and enters the tissue as highly motile phagocytes after inflammatory stimulation.
It is short-lived.
Responsible for green pus/mucus.
What are Eosinophils?
Lives slightly longer than PMNs.
Prominent orange granules in cytoplasm with affinity for acidic eosin dye.
Granules have hydrolytic enzymes to induce & maintain inflammation (allergy/asthma).
Bi-lobed nucleus.
Released from marrow and circulate for 8-12h before moving to tissue.
Role in parasitic infection.
What are Basophils?
Rarest type of WBC.
Bi-lobed nucleus obscured by prominent intense blue-purple granules with affinity for basic methylene blue.
Granules contain histamine, heparin and other inflammatory mediators.
They are effector cells in allergic reaction, has high affinity for IgE receptors on cell surface and when stimulated, it degranulates –> hay fever, allergic asthma, dermatitis.
What are lymphocytes?
They have round nucleus surrounded by thin-moderate rim of cytoplasm.
No visible granules.
Either B or T cell - requires IHC to test for surface receptors to distinguish.
B cells mature in bone marrow while T cells mature in thymus.
What are monocytes?
Precursor of tissue macrophage.
Numerous small lysosomal granules in cytosol and largest cell circulating in blood (4-5x RBC).
Non-lobulated nucleus (kidney-bean shaped)
What are the different types of macrophages and where can they be found?
Macrophages usually in loose CT. Skin: Langerhans cells Liver: Kupffer cells Brain: Microglia Others: Wanderers
What are platelets?
They are small cell fragments without nucleus. Have cytoskeleton (microtubules) and some organelles (mitochondria).
Role in haemostasis and contains conspicuous granules including coagulation factors
What are megakaryocytes?
Found in bone marrow.
Undergoes multiple duplication of nuclear material but not nuclear/cell division thus nucleus is very large.
Produces platelets via fragmentation from extension at outer margin of cell.
What is the process of haemopoiesis?
In the yolk sac (3 weeks into gestation), RBC forms.
By 2nd trimester, liver is the principal site for blood formation after being colonised by haematopoietic stem cells.
By birth, bone marrow is the main site and all bones participate.
As bones enlarge, there is excess capacity thus haemopoiesis is shut down in many bones. (Only vertebrae, ribs, skull, pelvis, proximal femur retain)
**Marrow in other bones are yellow adipose tissue but can revert to blood formation in emergency.
