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Blood Module > Histology > Flashcards

Histology Flashcards

1
Q

Describe blood staining

A

Leishman Stain is a neutral stain for blood smears. It
consists of a mixture of eosin (an acidic stain), and Methylene
blue (a basic stain) in Methyl alcohol.
1. Basophilic :Violet
2. Eosinophilic: Red
3. Azurophilic: reddish purple

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2
Q

Describe blood count

A

Blood count: It is the average number of the blood element per
cubic ml
A. RBCs count
B. Leukocytic count (Total and differential)
C. Platelet count
N.B Differential Leukocytic count: it is the percentage of each type of WBC relative to the total number

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3
Q

What colour are RBCs?

A

by Leishman stain
RBCs appear acidophilic with pale center
(normochromic)

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4
Q

color of a single rbc vs. cluster of rbcs

A

Single fresh erythrocyte:
pale greenish yellow

Crowded: red

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5
Q

what is the rouleaux appearance?

A

In slow circulation, RBCs adhere to each other like piles of coins. This is not permanent. This rouleaux appearance occurs due to high surface tension

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6
Q

Describe RBC shape

A

❖Biconcave disc.
❖Thick periphery of 2.6 μm
and thin center of 0.8 μm

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7
Q

Why are RBCs biconcave?

A
  1. Molecular structure of the cell membrane.
  2. Colloidal Hb complex inside cells: a change in the chemical composition of Hb filling the RBCs can change their shape
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8
Q

What are the abnormal shapes of RBCs?

A
  1. Crenation: if RBCs are put in hypertonic solution as 2% NaCl, they become shrunken (smaller with notched outline) due to loss of water.
  2. Spherocytosis: if RBCs are put in hypotonic solution such as distilled water, they first swell, become spherical and then rupture leaving remnants of cell membrane called ghosts.
  3. Poikilocytosis: abnormal shape of RBCs occurring in certain diseases as in
    sickle cell anemia, in which cells appear like a sickle or crescent.
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9
Q

Describe the typical size of RBCs

A

❖The normal diameter is 6-9 with an average diameter 7.5 µm.
< 6 µm –> Microcyte
> 9 µm –> Macrocyte

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10
Q

what is anisocytosis?

A

Great variation in RBC diameter

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11
Q

How are RBCs a ‘histological ruler’?

A

Can be used as an internal standard to estimate the size of other nearby cells or structures because of their uniform dimensions and presence in most tissues

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12
Q

What is the typical lifespan of a red blood cell?

A

 About 120 days
 Aged cells are destroyed in liver, spleen and bone marrow by macrophages.

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13
Q

Describe the structure and composition of RBCs

A

Normal RBCs are non-nucleated cells filled with
hemoglobin (Hb), and lacking organelles.

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14
Q

How are RBC energy requirements met?

A
  1. Soluble enzymes for glycolysis.
  2. Hexose monophosphatase shunt which produce ATP
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15
Q

Describe the RBC glycocalyx

A

❖ Outer surface of RBC membrane is covered by carbohydrate-rich glycocalyx containing the glycosylated extracellular domains of integral proteins, which include antigenic sites that form the basis for
1. the ABO blood typing system and
2. Rh group

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16
Q

Describe RBC membrane proteins

A

Most of the membrane proteins are integral membrane proteins.
❖They include ion channels called band 3 protein and glycophorin A

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17
Q

Describe the cell membrane of RBCs

A

 RBCs are surrounded by a selectively permeable & lipoprotein cell membrane.
 Inner surface associated with cytoskeletal protein which maintains the biconcave shape
❖This structure stabilizes the membrane, maintains the
biconcave shape of RBCs and provides the flexibility required for passage through capillaries

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18
Q

Brief descriptive summary of RBCs

A

Count: Females: 4.5-5 Males: 5-5.5 million/mm3
Size: 7-8 um
Structure:
✓Rounded, non-nucleated biconcave discs
✓RBCs are filled with hemoglobin
✓Spectrin is responsible for biconcave shape
✓They are flexible and can squeeze to pass through
narrow blood capillaries (plasticity).
✓in blood film and some diseases can form rouleaux
appearance
Lifespan ~ 120 days

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19
Q

How are RBCs adapted to their functions?

A

1.Absence of nuclei & organelles allows more space for Hb

2.Biconcavity of cells increases surface area for gas exchange & gives more space for Hb.

  1. cytoskeleton proteins contribute to Plasticity of the cell membrane to squeeze inside capillaries without cell injury.
  2. Highly selective cell membrane allows exchange of gases & prevents escape of Hb.
  3. RBCs have no mitochondria; hence they contain enzymes for glycolysis.
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20
Q

what is the cause of hereditary spherocytosis?

A

Hereditary spherocytosis: Abnormal shape
It is caused by an abnormal arrangement of the cytoskeleton of the RBCs (spectrin & ankyrin). The RBCs become sphere shaped, fragile and easily destroyed leading to hemolytic anemia.

Polycythemia: Abnormal count

Sickle cell anemia: abnormal Hb

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21
Q

Define Hemopoieses

A

It is the formation, proliferation and development of the blood elements

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22
Q

Types of hemopoiesis

A
  1. Prenatal hemopoiesis
  2. Postnatal hemopoiesis
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23
Q

Describe prenatal hemopoiesis

A

Mesoblastic (yolk phase) - begins in 3rd week of gestation.
hepato-splenic phase - during second trimester
myeloid phase (bone marrow) - begins in 3rd trimester

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24
Q

Describe postnatal hemopoiesis

A

occurs in:
- Myeloid tissue or bone marrow
- Lymphatic organs

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25
Q

Types of bone marrow

A

A-Inactive Yellow bone marrow
B-Active red bone marrow
Most of the bone marrow in adults is inactive yellow bone
marrow, present in the diaphysis of long bones.

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26
Q

Location of active red bone marrow in the body

A

In the fetus, newborn:
In most of bones.

In adults:
* Epiphysis of the long bones
* Ribs
* Body of vertebrae

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27
Q

Differentiate between red and yellow bone marrow (color, site, function)

A

Red active type
- Is red in color due to its high
content of Hb (in RBCs)
Site :-
In fetus: most of the marrow is
of the red type.
- In adults, it is present in:
epiphyses of long bones, diploes
of flat bones and vertebrae
Functions:
- Production of blood cells.
- Destruction of old RBCs.
- Storage of iron in macrophages

Yellow inactive type
- Is yellow in color due to its
high content of fat cells
- Forms most of marrow in
adults & is present in diaphysis of long bones
Functions:
- Storage of fats.
- In time of need as in hemorrhage or hypoxia, it
can change into active red
type

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28
Q

Describe the histological structure of bone marrow stroma

A

The bone marrow stroma is a meshwork of :

-Reticular fibers and reticular cells:
support the myeloid cells
& blood sinusoids

-Collagen type 1
- Macrophages
- Fat Cells

Stromal cells:
the fixed cell population of the bone marrow

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29
Q

Describe stromal cells

A

1-Reticular cells:
*They produce the reticular fibers.
* They secrete growth factors, which have a role in stimulation the PHSC.

2-Macrophages:
having pseudopodia which extend between endothelial cells into the lumen of
sinusoids to phagocytose foreign bodies and phagocytose the aged RBCs and the
malformed blood elements .
The stored iron will be utilized in the synthesis of the heme portion of hemoglobin

3-Fat cells: One of the largest cells.

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30
Q

what are the main bone marrow components?

A

Structure of BM section:
1) Connective tissue stroma
2) Blood sinusoids
3) Hematopoietic cells

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31
Q

Describe blood sinusoids

A
  • Irregular wide dilated blood channels.
  • Lined by fenestrated endothelial cells surrounded by a discontinuous basement membrane.
  • Allow passage of newly formed cells.
  • Surrounded by macrophages
32
Q

Pluripotent hemopoietic stem cells proliferate and form:

A

A- Multipotent myeloid stem cells: produce RBCs, granulocytes, monocytes and
megakaryocytes.
B- Multipotent lymphoid stem cells: produce lymphocytes.

Some of their daughter cells form specific, irreversibly differentiated cell types. Other daughter cells remain stem cells

33
Q

Multipotent lymphoid stem cells are characterized by:

A

Not morphologically distinguishable, Have general aspect of lymphocytes, low mitotic activity and self renewal.

34
Q

explain the difference between pluripotent, progenitor, precursor and mature cells

A

Pluripotential hemopoietic stem cells :capable of self-renewal

Progenitor cell
reduced potentiality
(less self renewal capacity)

Precursor cells (blasts)
have their own morphological characteristics

Mature cell
Clear morphology
No mitotic activity

35
Q

Describe progenitor cells

A

They are called colony forming cells or units and committed to a single cell line.
Characterized by: Not morphologically distinguishable, Have general aspect of lymphocytes, High mitotic activity and less self-renewal capacity.
There are four types of progenitor cells (colony forming unite; CFUs):
1. CFU- Erythrocytes (CFU-E).
2. CFU – Megakaryocytes (CFU- Meg).
3. CFU- Granulocyte- monocyte (CFU- GM).
4. CFU – Lymphocytes (CFU-L).

36
Q

Describe precursor cells

A

Characterized by:
Begin morphologic Differentiation, High mitotic activity and No
self renewal

37
Q

Describe Mature cells

A

Characterized by:
Clear morphologic differentiation and no mitotic activity

38
Q

what are the precursor cells of Erythropoiesis

A

1-Proerythroblasts
large (17 μm) Basophilic (due to polyribosomes). Large nucleus with prominent nucleolus.

2-Basophil erythroblasts
smaller (14 μm) deeply basophilic cytoplasm. Small and condensed nucleus.

3-Polychromatophil erythroblasts
smaller (11 μm) it has many colors, because it has areas of basophilia due to the polyribosomes and areas of acidophilia because Hb begins to fill the cytoplasm. small and deeply stained nucleus

4-Orthochromatophil erythroblasts (normoblasts)
smaller (8 μm) acidophilic (rich in Hb). small and condensed (pyknotic) and eccentric, ready to come out and engulfed by macrophages.

5-Reticulocytes (Immature RBCs):
Slightly larger than normal RBCs, still retains some polyribosomes which appear as network with the supravital dye Brilliant cresyl blue.
Soon (within 24-28 hrs) the cell loses its polyribosomes to become mature erythrocytes. 0.5% - 2.5% can be seen in peripheral blood normally in adults.

39
Q

How many thrombocytes are present in the body?

A

 Number: 150,000- 410,000/mm³.
 Increase in number: Thrombocytosis
 Decrease in number: Thrombocytopenia

40
Q

what is the lifespan of thrombocytes?

A

10 days. Senescent platelets are phagocytosed by macrophages primarily in the spleen.

41
Q

what is the origin of platelets?

A

The platelets are cell fragments derived from the megakaryocytes in the bone marrow

42
Q

Describe the morphology of platelets by LM

A

 Size: 2 - 4 µm in diameter.
 Shape: oval disk shaped (cell fragments).
Nucleus: They lack nuclei.

43
Q

Describe the morphology of platelets by EM

A

 The cell membrane coated by glycocalyx (glycoproteins and glycolipids) to be involvedin platelets adhesion.

44
Q

Describe the cytoplasm of platelets

A

Hyalomere - peripheral clear region
Granulomere - central granular region

45
Q

Describe the hyalomere

A

It is the peripheral part. It shows:
a) Marginal bundle consisting of:
 10 -15 microtubules arranged parallel to each other forming a ring within the hyalomere. They assist in maintaining the discoid
form of the platelets.

 Actin and myosin microfilaments helping contraction of the
platelets during retraction of blood clot.
b) Two tubular systems:
 Open canalicular system: which is invagination from the cell membrane, facilitating platelets’ uptake of factors from plasma.
Also, this system facilitates rapid degranulation upon activation and Ca release.

 Dense tubular system: which may be remnants of endoplasmic reticulum of megakaryocytes (stores Ca ions).

46
Q

Describe the granules in the granulomere

A

Alpha granules:
- Fibrinogen
- PDGF
- coagulation factors.
- Platelet factor 4.

Delta granules:
-ADP
- ATP
- Ca
- Serotonin

Lambda granules:
Lysosomes

47
Q

How do platelets develop?

A

1- Stem cells:
Pleuripotent hemopoietic stem cell (PHSCs)
multipotential myeloid stem cell

2- Progenitor cells:
colony forming unit megakaryocyte (CFUMeg)

  1. Megakaryoblast (Immature
    megakaryocyte)

4.Megakaryocyte (mature cell)

48
Q

Describe the megakaryoblast

A

Megakaryoblast (Immature
megakaryocyte)

  • Size: large cell 25-50μm.
  • Nucleus: large with numerous nucleoli.
  • Cytoplasm: highly basophilic
    homogenous non-granular.
  • Before differentiation, they
    undergo endomitosis,
    with repeated rounds of
    DNA replication not
    separated by cell divisions,
    resulting in a nucleus that is
    highly polyploid.
49
Q

Describe the megakaryocyte

A
  • Size: a giant cell up to 150 μm
  • Nucleus: large lobulated and polyploid.
    -Cytoplasm: basophilic - granular.
    -It contains numerous mitochondria, well developed rER, extensive Golgi complex, α granules, lysosomes (lambda granules) and dense bodies.

Megakaryocytes are located near sinusoids, where they extend their long processes through fenestrae of endothelial cells into the sinusoidal lumen. Platelets are separated from the top of these processes and washed out with circulation.
Invagination from cell membrane forming the demarcation membranes
that represent reservoirs for rapid elongation of the processes.

50
Q

Lifespan and normal count of leucocytes

A
  • hours to days
  • 4000 - 11,000
    Above 11,000 - leucocytosis
    Below 4,000 - leucopenia
51
Q

Classification of leucocytes

A

Granular leucocytes - neutrophils, eosinophils, basophils
A granular leucocytes- lymphocytes and monocytes

52
Q

Life span of neutrophils

A

6-8 hours in blood
1-4 days in connective tissue
Before dying by apoptosis

53
Q

LM structure of neutrophils (shape and size, nucleus, cytoplasm)

A

1) rounded cells, 12-15 um diameter

2) multilobed deeply stained
- mature neutrophils contain 3-5 lines interconnected by delicate chromatin strands
- immature cells contain one bent rod/ horse shoe nucleus

3) cytoplasm contains fine neutrophilic granules and azurophilic granules

54
Q

TEM structure of neutrophils

A

BY TEM: the cytoplasm contains:
1. Few mitochondria, small Golgi complex and rER.

  1. Granules include:
    • Neutrophilic granules:
    -constitute 80% of granules.
    -They are small numerous membrane-bounded and contain alkaline phosphatase, collagenase and lactoferrin (bacteriostatic).

• Azurophilic granules:
-constitute 20% of granules) They are large and less numerous. They are lysosomes which contain hydrolytic enzymes, proteolytic and lipolytic enzymes, peroxidase and bactericidal basic protein.

55
Q

Pus formation

A

• Apoptotic neutrophils, bacteria, semi-digested material, and tissue fluid form a viscous, usually yellow collection of fluid called pus.

56
Q

Percentage of band neutrophils

A

1-2 % under normal conditions

57
Q

Life span of eosinophils

A

Life span: Few hours in blood and 1-2 weeks in connective tissue.

58
Q

LM structure of eosinophils (shape and size, nucleus, cytoplasm)

A

1) rounded cells, 12-15 um in diameter

2) Nucleus: is bilobed or horse-shoe shape (formed of 2 lobes connected by chromatin thread)

3) Cytoplasm: It is packed with numerous large, refractile and eosinophilic specific granules (about 200/cell).

59
Q

TEM structure of eosinophils

A

The cytoplasm contains a small Golgi apparatus, few mitochondria, rER, moderate amount of glycogen and highly characteristic granules.

60
Q

Describe membrane bound specific granules of eosinophils

A

Membrane bounded specific granules: -They are large elongated or ovoid with:
-flattened crystalline electron dense core called the internum
-surrounded by less dense zone called the externum.

The internum contains mainly:
-major basic proteins (MBP) and -eosinophilic peroxidase (both have anti-parasitic worms & helminths)

The specific granules also contain histaminases and arylsulphatase (anti-allergic action) which degrade histamine and slow reacting substance of anaphylaxis (SRS-A) released by mast cells and basophils during hypersensitivity reaction
complex that are internalized by the eosinophil).

61
Q

Describe Azurophilic granules of eosinophils

A

Azurophilic granules: smaller and less in number.
They are lysosomes containing hydrolytic enzymes (anti-parasitic and also hydrolyze the Ag-Ab complex that are internalized by the eosinophil).

62
Q

Life span of basophils

A

Life span: Few hours in blood and several months in connective tissue.

63
Q

LM structure of basophils (shape and size, nucleus, cytoplasm)

A
  • Shape & size: rounded cells, 12-15 um in diameter.

-Nucleus: S- shaped divided into 2 or more irregular lobes.

Cytoplasm: It is light basophilic packed with large, dark and basophilic specific granules (they could be metachromatically stained by toluidine blue). They may mask the nucleus.

64
Q

TEM structure of basophils

A

Sparse number, of mitochondria, small Golgi complex, rER, moderate amount of glycogen and granules which are:
- membrane bound specific granules
- few azurophilic granules

65
Q

Describe membrane bound specific granules and azurophilic granules of basophils

A

• Membrane bounded Specific granules:
-are few, irregular in size and shape and homogenous electron dense granules.
- They contain heparin, histamine and eosinophil & neutrophil chemotactic factors.
-They are similar to mast cells.

Few azurophilic granules (lysosomes) are present. They contain hydrolytic enzymes.

66
Q

Life span of lymphocytes

A

Lymphocytes vary in life span according to their specific functions; some live only a few hours and others survive in the circulating blood or other tissues for many years.

67
Q

Size of lymphocytes

A
  1. Small lymphocytes: 6-8 um in diameter representing majority of lymphocytes in circulating blood.
  2. Medium-sized lymphocytes: 10-15 um in diameter representing few blood lymphocytes

3) Large lymphocytes: 15-18 um in diameter.
-They are present mainly in lymphatic tissue.
The majority of large lymphocytes seen in blood represent activated B lymphocytes.
Some circulating large lymphocytes are natural killer cells.

Both medium and large are activated lymphocytes

68
Q

Shape of lymphocytes

A

Shape:
Both B & T lymphocytes are similar in appearance.
The small cells are spherical with large central, rounded and condensed nucleus. A thin rim of pale basophilic cytoplasm is present around the nucleus.

69
Q

Nucleus of lymphocytes

A
  • Nucleus: Small lymphocytes have spherical nuclei occupying most of the cell while the Larger lymphocytes have larger, slightly indented nuclei.
70
Q

Cytoplasm of lymphocytes

A
  • Cytoplasm: Small lymphocyte show thin rim of basophilic cytoplasm surrounding the nucleus, while larger lymphocytes show more slightly basophilic cytoplasm
71
Q

TEM structure of lymphocytes

A

Few mitochondria, rER and small Golgi complex. Many free ribosomes.
Few azurophilic granules as primary lysosomes.
Surface is covered by microvilli

72
Q

Differentiate between small and medium sized lymphocytes

A

Percentage
Small: 92% of circulating lymphocytes
Medium: 8%

Size
Small: 6 - 9 um
Medium: 10 - 15 um

Nucleus
Small: Rounded indented
Medium: Larger indented, lightly stained

Cytoplasm
Small: Thin rim of basophilic cytoplasm surrounding the nucleus medium: More cytoplasm, slightly basophilic

EM

Small
Free ribosomes
Few mitochondria, golgi complex and rER

Medium
Large number of mitochondria,
abundant rER, few polysomes,
well-developed Golgi complex, few azurophilic granules.

73
Q

Differentiate between B and T lymphocytes

A

To differentiate between B and T lymphocytes, labeled antibodies are used to specific surface markers.

74
Q

Monocytes life span

A

From few hours to many years

75
Q

Monocytes microscopic picture LM

A

Shape & size: large rounded cells, 12-20 um in diameter.

Nucleus: Large, highly indented, kidney-shaped or C-shaped and light stained, paler than that of lymphocytes.

Cytoplasm:
Basophilic or bluish gray in color (Frosted glass appearance) containing fine numerous azurophilic granules.

76
Q

TEM structure of monocytes

A

Numerous lysosomes (i.e. azurophilic granules).
Other organelles as: mitochondria, prominent Golgi complex, few rER, SER and ribosomes.

Blood Module (9 decks)

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