THE BLOOD
By
Dr. Amany Abd El Fattah
Mohamed
Lecturer of Medical Histology & Cell Biology
Learning outcomes
❑At the end of the lecture, the students should be able
to:
• Enumerate components of blood.
• Describe the structure of RBCs (erythrocytes).
• Describe the structure of WBCs (leucocytes).
• Describe the structure of the platelets (thrombocytes).
• Mention types of bone marrow and differences
between
Case Scenario
• 30 years old female came with easy fatigability
and shortness of breath on doing little effort 3
months ago. She also noticed that she appears
pale and always have cold extremities. The
physician ask for CBC which reveal that RBCs
count was 2.5 million/cc .
Q: What is the most probable diagnosis of this
case?
Learning outcome 1
Enumerate components of blood.
Blood
Learning outcome 2
Describe the structure of RBCs.
Biconcave
RBC
• Def.: non-nucleated corpuscles
responsible for carrying O2 & CO2.
• Shape: rounded biconcave discs.
**Abnormal shapes:
Spherocytosis: spherical or
biconvex.
➢Color:
• Drop of blood → red.
• In stained sections → RBCs with normal
HB appear acidophilic with pale center
(normochromic).
• Hypochromic (pale)→ less HB%.
• Hyperchromic (dark) →more HB%
➢Size:
- 6-9 μm in diameter (7.5 μm)
**Abnormal size:
1- Macrocytic anemia: > 9 μm.
2- Microcytic anemia: < 6 μm.
➢Life span: 120 day.
➢Number:
• In males: 5 – 5.5 million/mm3.
• In females: 4.5 – 5 million/mm3.
• Abnormal number:
1- Anemia (decrease in num.).
2- Polycythemia (increase in num.).
❖Structure:
• Non-nucleated (corpuscles).
• No organelles, filled with HB
• Plastic cell membrane.
Learning outcome 3
Describe the structure of WBCs.
WBCs
➢Def.: true nucleated cells having cell organoids,
inclusions, but no hemoglobin.
➢Color:
Single WBC is colorless but, when
aggregated appear white.
➢Number: 4000 – 11.000/mm3.
**Abnormal number:
1- Leukocytosis -- > 11.000/mm3.
2- Leucopenia -- < 4000 /mm3.
Neutrophils Eosinophils Basophils
Percentage 60-70% 2–5% 0.5 -1 %
Size & Shape 10-12 um, rounded 12 - 15 um, rounded 10-12 um, rounded
Nucleus Single, dark stained, Bilobed, horse shoe Large irregular.
segmented (3-5 segments) shaped.
connected by fine
chromatin threads
Cytoplasm Fine neutrophilic granules Acidophilic refractile Large basophilic
granules. granules
Function Defense function as it Anti-allergic action via: Produce heparin
migrates to infected areas & 1- Phagocytosis of the and histamine
phagocytoses microorganisms antigen-antibody complex. during allergy.
(so called Microphages) 2- Secretion of histaminase
and sulphatase enzymes.
➢Percentage: 25-30%
➢Classification:
B- lymphocyte
1. Small sized lymphocyte (4-7um)
2. Medium sized lymphocyte (7-10um) T- lymphocyte
3. Large sized lymphocyte (10-15um)
➢Nucleus: Central, rounded and dark (small type).
Large, rounded pale and (large type).
➢Cytoplasm: Small lymphocyte
- Little, thin rim, pale basophilic (small type).
-Abundant, more basophilic and non granular
(large type).
➢Function:
1- Humoral immunity (by B lymphocytes).
2- Cell-mediated immunity (by T lymphocytes).
Large lymphocyte
➢Percentage: 3-8%
➢Size: 15 um.
➢Nucleus: Large, pale, kidney-shaped.
➢Cytoplasm: Abundant, pale blue.
➢Function: migrate to C.T. where they can be
transformed into macrophages.
Learning outcome 4
Describe the structure of
platelets.
Platelets
➢Def.: Fragments of cytoplasm covered
with membrane but have no nucleus (not
true cells).
➢Origin: megakaryocytes in the red
bone marrow.
➢Size: 2 - 4 m.
➢Shape: oval or rounded discs.
➢Number: 150.000 - 400.000/mm3.
➢L.M:
- Oval or rounded non nucleated discs.
- Outer part is transparent and pale blue (called hyalomere).
- Central part contains dark stained granules (called granulomere).
➢Function: Stop bleeding (hemostasis).
Learning outcome 5
Mention types of bone marrow and differences
between.
Bone marrow
• It is the site of formation of blood cells.
•Types:
Red bone marrow (active).
Yellow bone marrow (inactive).
Red bone marrow White bone marrow
Site 1. In fetus: Present in most of the bone. Shaft of long bone.
2. In adult: Flat bone (skull), Sternum, ribs,
clavicle and vertebrae.
Structure 1. Stroma: network of reticular fibers contains C.T 1. Stroma (mainly formed of
cells “fibroblast & fat cells”, bone cells & matrix. large number of fat cells).
2. No free cells.
2. Blood sinusoids: wide blood vessels lines by
fenestrated endothelial cells & surrounded by
macrophages.
3. Free cells: developing blood cells.
Function 1. Formation of blood cells. 1. Storage of fat.
2. Destruction of old RBCs by the macrophages. 2. On need (hemorrhage and
3. Storage of fat in the fat cells. hemolysis), it is changed
into active red marrow.
Case Discussion
• A case of anemia.
• It is more common in females due to
monthly blood loss.
• It is due to bone marrow failure,
nutritional deficiency, or blood loss.
• Treatment of the cause is needed.
Summary and wrap up
• Blood is formed of plasma & blood cells.
• Blood cells are RBCs, WBCs & platelets.
• RBCs are the most numerous cells, non nucleated discs, contain Hb that
carry O2 & CO2.
• WBCs are true nucleated cells of different types (granular & non granular
groups).
• Platelets are fragments that play an important role in stopping bleeding.
• Bone marrow is the factory for blood cells production.
