1
Q
What are the characteristics of cardiac muscle fibers?
A
▪ Chain of short cylindrical cells.
▪ Involuntary.
▪ The cardiac muscle fiber is not a syncytium as the individual muscle cell joined together end to end by cell junction (Intercalated disc).
2
Q
What is the site of cardiac muscle fibers?
A
wall of the heart (myocardium).
3
Q
What is the shape of cardiac muscle fibers under LM?
A
(Length - width) - (branching - striation) - (nucleus - sarcoplasm - endomysium)
✓ Small in caliber (25 um).
✓ Variable in length
✓Extensive branching and anastomosing, so, they are cut in various directions.
✓ It is surrounded by C.T. (Endomysium) -» contains blood vessels and lymphatics.
✓ Irregular striation.
✓ Nuclei are large, oval, central, mono or binucleated
✓ Sarcoplasm is Granular, acidophilic
✓ The sarcoplasm contains lipochrome pigment which increases in old age and causes brown atrophy of the heart
4
Q
What does the endomysium contain?
A
contains blood vessels and lymphatics.
5
Q
What is the shape of cardiac muscle fibers under EM?
A
❑ The Sarcoplasm contains:
✓ Glycogen granules
✓ Numerous mitochondria (40% of cell volume).
✓ Golgi saccules.
✓ Lipid droplets (fatty acids are the major fuel of the heart).
✓ Lipofuscin pigment granules (aging pigment), often seen in long-lived cells, are found near the nuclear poles of cardiac muscle cells.
✓ In the atria of the heart, atrial granules are seen in the juxtanuclear cytoplasm. These granules contain hormones known as an atrial natriuretic factor (ANF). This hormone is diuretically affecting the urinary excretion of sodium. (Endocrine effect to reduce BP)
✓ The sarcomeres have an identical banding pattern to that of skeletal muscle.
✓ Traversed by dark staining disc (Intercalated disc).
✓ Rich in myofibrils:
- Branching and anastomosing.
- Less regularly arranged to give less regular striation In L/M.
- Variable in diameter
❑ T-Tubules and sarcoplasmic reticulum:
✓ Less developed than skeletal muscle.
✓ The cardiac muscle fibers have no triad but only dyads formed of:
- T- tubule: Wider in the ventricles than atria and surround the myofibrils at the Z-line.
- Terminal cistern: Smaller and incomplete.
6
Q
What is the major fuel of the heart?
A
Fatty acids
7
Q
What is a diad formed from?
A
- T- tubule: Wider in the ventricles than atria and surround the myofibrils at the Z-line.
- Terminal cistern: Smaller and incomplete.
8
Q
What is the definition of intercalated discs?
A
Transverse lines that cross the cardiac fibers at irregular intervals, joining the adjacent myocardial cells.
9
Q
What do intercalated discs coincide with?
A
Always coincide with the Z lines.
10
Q
What is the shape of intercalated discs under LM?
A
a dark stained linear (straight) structure that is oriented transversely to the muscle fiber or step-like.
11
Q
What are the stains used for intercalated discs?
A
- Iron Hx.
* Silver.
12
Q
What is the shape of intercalated discs under EM?
A
Formed of 3 types of junctions:
A: Fascia adherens
B: Desmosome
C: Gap junction
13
Q
What is the site of fascia adherens?
A
In transverse part
14
Q
What is the function of fascia adherens?
A
- It performs intracellular adhesion.
* Anchoring site for myofibrils (represent half a Z-line).
15
Q
What is the site of desmosomes?
A
In transverse and longitudinal parts.
16
Q
What is the function of desmosomes?
A
It prevents the separation of cells during contraction.
17
Q
What is the site of the gap junction?
A
In longitudinal part (parallel to the myofibrils).
18
Q
What are the characteristics of gap junction?
A
- There is a 2 nm gap between cells.
- This gap is traversed by intercommunicating channels between the cells.
- These channels allow free and rapid transmission of the nerve impulses from one cell to another.
- Thus, the fiber contracts as one unit (act physiologically as one unit)
19
Q
How do cardiac muscles grow?
A
▪ Hypertrophy (increase in the size of cardiac muscle due to new formation of myofibrils).
▪ No cell division.
▪ No regeneration.
20
Q
Do cardiac muscles get repaired?
A
No, When the muscle fibers are lost, they are replaced by fibrous C.T. (It heals by fibrosis), And there are no satellite cells
21
Q
What is the heart formed from grossly?
A
- 2 thin atria.
* 2 thick ventricles.
22
Q
What is the wall of the heart formed from?
A
- The Epicardium.
- The Myocardium.
- The Endocardium.
23
Q
What are the characteristics of muscular tissue?
A
✓ Formed of muscle fibers.
✓ Contractility is the characteristic feature of all muscle types (myofibrils).
✓ The plasma membrane is called the sarcolemma.
✓ The cytoplasm is called sarcoplasm.
24
Q
What are the types of muscles?
A
- skeletal (Striated - Voluntary)
- smooth (Nonstriated - Involuntary)
- cardiac (Striated - Involuntary)
25
What is the epicardium?
Visceral layer of the double-layered pericardium (the membrane surrounding the heart).
26
What does the epicardium invest?
Invests the heart from outside.
27
What is the epicardium formed of? (shape under LM)
✓ Simple squamous epithelium (outer).
✓ A subserous layer of C.T. contains coronary blood vessels and fat cells.
✓ The C.T. blends with the endomysium of the myocardium.
28
What is the myocardium?
Cardiac muscle fibers (Main bulk) that run in various directions.
29
What is the shape of the myocardium under LM?
- Cardiac muscle fibers (Main bulk) which run in various directions.
- Separated by loose C.T. endomysium which contains blood vessels and lymphatics.
- Covered on the outside by (epicardium) and inside by (endocardium)
- Thicker in the wall of the ventricles than atrial walls.
30
What does the endocardium line?
It lines the chambers and covers the valves of the heart
31
What is the shape of the endocardium under LM?
• It is formed of four layers from inside to outside:
1. Simple squamous endothelial layer (most inner). (In contact with blood)
2. Subendothelial dense C.T. layer. (For support)
3. A layer of dense elastic fibers. (For elasticity)
4. A layer of loose C.T (connected with endomysium) which contains blood vessels and Purkinje fibers (outer).
32
What Is the structure of the cardiac skeleton?
Dense CT
33
What is the cardiac skeleton attached to?
Attached to contractile muscle fibers.
34
What does the cardiac skeleton form?
Forms the fibrous part of interventricular and interatrial septa and fibrous ring around valves.
35
What are the functions of the Cardiac skeleton?
✓ Anchoring and supporting the heart valves.
✓ Providing firm points of insertion for cardiac muscles.
✓ Coordinating heartbeat by acting as electrical insulation between atria and ventricles.
36
What are the valves of the heart?
1- Tricuspid valve:
• It is present between the right atrium and the right ventricle.
• It is formed of 3 cusps.
2- Mitral valve:
• It is present between the left atrium and the left ventricle.
• It is formed of 2 cusps.
37
What is the shape of the valves under LM?
• It is a fold of the endocardium.
• It has a middle supporting layer of:
➢ Dense C.T. contains elastic fibers and collagen fibers.
➢ Phagocytic cells.
* It is thickened at the base of the mitral and tricuspid valves forming rings of C.T. around the orifice.
* It contains smooth muscle fibers (for moving) and capillaries at the base.
38
What is the impulse conducting system of the heart?
It is a vascular neuromuscular structure between cardiac muscle fibers.
39
What is the impulse conduction system of the heart formed of?
Formed of modified cardiac muscle cells.
40
What is the function of the impulse conducting system of the heart?
Generates and propagates waves of depolarization, stimulating rhythmic contractions of the myocardium.
41
What are the types of impulse conducting systems of the heart?
• S-A Node—» the pacemaker.
• A-V Node.
“Both S-A and A-V nodes are present in the wall of right atrium”
* A-V bundle of His and 2 branches and their ramification.
* Moderator Band.
42
What is the definition of the moderator band?
A bundle of cardiac muscle fibers through which the right branches of the A-V bundle of His traverse the cavity of the right ventricle to reach the lateral wall of the heart and lie under the endocardium.
43
What is the structure of the moderator band? (Shape under LM)
* Appears as pale area.
* Mainly formed of Purkinje fibers which are separated by loose C.T. endomysium.
* Contains fat cells (for support) and blood capillaries.
44
What are the differences between Purkinje fibers and cardiac muscles?
“DIM CG FPT”
- Larger diameter.
- No intercalary disc but there is: "no contraction"
✓ Numerous gap junctions for rapid conduction.
✓ Desmosomes.
- Myofibrils
• Few.
• Peripheral.
- Cytoplasm
•Granular.
•Vacuolated (glycogen). "For anaerobic glycogenolysis in extreme conditions"
- Grouped into bundles and surrounded by C.T. sheath.
```
- Faster Conduction due to:
• Gap junctions
• No T.T.
• Glycogen
• C.T. sheath
```
- Paler in color due to:
• a Large amount of glycogen that dissolves during preparation.
•Few numbers of myofibrils that are peripheral in position.
- No T. tubules.
45
What is the shape of Purkinje fibers under EM?
“No T.T”
* Thin and irregular sarcolemma.
* Separate, short, elongated cylindrical cells.
* One or two peripheral nuclei.
46
Revise the comparison between skeletal muscle and cardiac muscle
..
47
What is the circulatory system formed of?
- The heart.
- Various types of blood vessels including:
Arteries: (large elastic, medium-sized and arterioles).
Veins: (venules, medium-sized and large veins).
Connecting vessels between arteries and veins:
1- Blood capillaries.
2- Arterio-venous anastomosis.
48
What is the function of the blood vessels?
These vessels distribute blood to every part of the body and return it to the heart for
redistribution.
49
What are the three layers that form any blood vessel?
Tunica intima (the inner most coat)
Tunica media
Tunica adventitia
50
What does the tunica intima consist of?
Endothelial lining:
✓ Formed of simple squamous epithelium with flat nuclei
resting on a basal lamina. "As it is in connection with blood"
✓ Have a turnover rate of 1% per day.
Subendothelial layer:
✓ Consists of loose C.T.
✓ Rich in elastic fibers
Internal elastic lamina
✓It is seen as a wavy pink line just beneath the endothelium in arteries
✓ It is composed of elastic fibers.
51
What is the tunica media formed of?
- Composed of circularly arranged smooth muscle cells.
- Variable amount of elastic fibres.
- Fine collagenous and reticular fibers. "All fibers"
- In large muscular arteries
✓ The outer border of the media is separated from the outer tunica adventitia by the external elastic lamina.
52
What is Tunica adventitia formed of?
- Fine collagenous fibres longitudinally oriented, contain collagen type I.
- Elastic fibers. “But no reticular”
- Tiny blood vessels called vasa vasorum (vessels of vessels) supply the adventitia and may reach the periphery of the media.
- Lymphatics are also present in the adventitia of arteries only but in veins they can penetrate the media.
53
What are the large elastic arteries?
Large elastic arteries include the aorta and its large branches, the pulmonary, the subclavian and the innominate.
54
What are the characters of large arteries?
They have thick walls and wide lumen.
Their media are rich in elastic fibers.
Their structure is more or less the same as the aorta.
55
What is the LM of the intima of the aorta? "Aorta=many elastic fibers"
Forms about 1/6 of the thickness of the wall.
The intima is thicker than the intima of a muscular artery.
The subendothelial layer is thick and rich in elastic fibers.
The internal elastic lamina is present but not be easily discerned, since it is similar to the elastic laminae of next layer.
56
What is the LM of the media of the aorta?
Is very thick and forms the main thickness of the wall.
It contains fenestrated elastic laminae concentrically arranged
In between the elastic laminae smooth muscle cells, reticular fibers, collagenous fibers and ground substance consisting mainly of chondroitin sulfate. "More strength"
57
What is the LM of the adventitia of the aorta?
Relatively thin and contains collagenous and elastic fibres.
C. T. cells, vasa vasorum, lymphatics and nerves.
58
What is the function of large elastic arteries?
Transport blood away from the heart.
| Maintain diastolic pressure.
59
What are the characteristics of the wall and the lumen of medium sized artery?
- Thick "more hemorrhage when damaged"
- Narrow
- rounded "due to elasticity"
- no valve
60
What are the characteristics of the wall and lumen medium sized vein? "Vein=no elasticity"
- Thin
- Wide
- Collapsed
- valve is present
61
What are the characteristics of tunica intima of medium sized artery?
- Thick
| - Internal elastic lamina is well developed
62
What are the characteristics of tunica intima of medium sized vein?
- Thin
| - Internal elastic lamina is absent
63
What are the characteristics of tunica media of medium size artery?
- Thick.
- Formed of smooth muscle fiber and elastic fibers.
- External elastic lamina may be present between the media and adventitia.
64
What are the characteristics of tunica media of medium sized vein?
- Thin.
- Formed of few smooth muscle fibers.
- No external elastic lamina.
65
What are the characteristics of Tunica adventitia of medium size arteries?
- Thinner than media
- contains elastic fibers
- No lymphatic capillaries in its wall
66
What are the characteristics of Tunica adventitia of medium sized veins?
- Thicker than media
- No elastic fibers
- Lymphatic capillaries may be found
67
How does blood flow in medium sized arteries?
Rapid flow of arterial blood
68
How does blood flow in medium size veins?
Slow flow of venous blood
69
What is the function of medium sized arteries?
Distribute blood to the whole body
70
What is the function of medium sized vein?
Carry venous blood from the tissues Withstand venous blood pressure
71
What is the definition of Arterioles?
- Are the small branches of the arteries, Their diameter is less than 0.5 mm.
72
What is the structure of arterioles?
The subendothelial layer is very thin
The elastic laminae may be present or absent "absent in very small arterioles"
Tunica media is formed of 1-2 layers of smooth ms.
Tunica adventitia is very thin "No vasa vasorum as the vessels are nourished by the blood flowing in the lumen"
73
What is the definition of meta-arterioles?
The terminal parts of the arteriole before their connection with the blood capillaries.
74
What is the structure of meta-arterioles?
They have sphincters at their terminal.
| They have a sparse layer "separated" of smooth muscle
75
What is the function of arterioles?
✓ They supply the tissues and organs with arterial blood.
| ✓ They control blood pressure. "Sphincters"
76
What is the definition of veins?
Blood vessels carry venous blood from the tissues and return it to the heart.
77
What do veins start as and what do they end as?
They start as post-capillary venules which are collected to form muscular venules then form large veins.
78
What are veins classified into?
o Venules.
o Medium-sized veins.
o Large veins.
79
What are the types of venules?
Post-capillary venules.
Collecting venules.
Muscular venules.
80
What is the definition of post Capillary venules?
Small venules that collect the capillaries.
81
What is the LM structure of post Capillary venules?
▪ As capillary
▪ Endothelium: simple squamous epithelium.
▪ Basement membrane which supports the endothelium.
▪ Pericytes lie between the endothelium and basement membrane, they can differentiate to smooth muscle cells.
82
What is the shape of postcapillary venues in the thymus gland and lymph nodes?
the post-capillary venules are lined with simple cubical epithelium, which shows wide intercellular spaces allowing migration of the T. lymphocytes.
83
What is the definition of collecting venules?
Are venules that collect the post-capillary ones.
84
What is the structure of collecting venules?
In addition to endothelium and pericytes, they possess an adventitia consisting of fibroblasts and collagen fibers.
85
What is the definition of muscular venules?
Large-sized venules into which the collecting venules empty.
86
What is the structure of muscular venules?
- They have one or two layers of smooth muscle cells in their media. "Like arterioles"
- The adventitia is relatively well developed.
87
What are the characters of large veins and what is an example for them?
Character:
- Has very wide lumen with many valves.
- Collapsed thin and flat wall.
inferior Vena Cava
88
What is the LM structure of large veins?
The intima: Similar to the medium-sized vein.
The media: Thin and contains only smooth muscle fibers.
The adventitia: Very thick layer of loose C.T. contains collagenous fibers, C.T. cells, vasa vasorum, and nerves, Also contains longitudinally arranged bundles of smooth muscle fibers. "Shorten-lengthen the vein to push blood"
89
What is the definition of blood capillaries?
Thin-walled tubular blood channels that conduct the blood from the terminal arterioles to the venules.
Networks of these vessels are known as capillary beds.
90
What is the LM structure of blood capillaries?
Single-layer of endothelial cells is rolled up in the form of a tube.
Rest on a basal lamina.
Pericytes: lie between endothelium and the basal lamina.
91
What is the EM structure of blood capillaries?
Contain all the usual organelles.
Abundant microfilaments and intermediate filaments.
Endothelial cells show pinocytotic vesicles.
The cells are held together by zona occludens and gap junction.
Pericytes with long cytoplasmic processes surround the endothelial cells along capillaries, enclosed in their own basal lamina.
Their cytoplasm contains myosin, actin, and tropomyosin which suggest their contractile function.
92
What happens to pericytes after tissue injury?
pericytes proliferate and differentiate to form new blood vessels and C. T. cells.
93
What are the types of capillaries?
Continuous capillaries
Fenestrated capillaries
Fenestrated without diaphragm
The sinusoid or discontinuous capillary
94
What are the characters of continuous capillaries?
No fenestrae are present in this type.
May have numerous pinocytotic vesicles as in muscle capillaries or few or no pinocytotic vesicles as in nervous system capillaries
Allow regulated exchange of material.
95
What are the sites of continuous capillaries?
Is found in all kinds of muscle tissue, nervous tissue, and exocrine glands
“Nervous-muscular-Exo from prison”
96
What are the characteristics of fenestrated or visceral capillaries?
Large fenestrae are present in the walls of endothelial cells.
The fenestrae are closed by a diaphragm that is thinner than a cell membrane.
A continuous basal lamina is present.
Allow more extensive molecular exchange across the endothelium
97
What are the sites of fenestrated or visceral capillaries?
Present in the kidney, intestine, and endocrine gland.
“KID INSIDE”
98
What are the characteristics of fenestrated capillaries without diaphragms?
Has a very thick basal lamina that separates the endothelium from the overlying epithelial cells.
99
What are the sites of Fenestrated Capillary without diaphragm?
Renal glomerulus capillary
100
What are the characteristics of sinusoids or discontinuous capillaries?
TDM
✓ Has tortuous path.
✓ Enlarged diameter
✓ Macrophages may be present outside the sinusoidal wall, extending their pseudopodia inside the wall to phagocytose any foreign body.
✓ The endothelial cells have large fenestrae without diaphragm forming a discontinuous layer
✓ The basal lamina is discontinuous.
✓ Allow maximal exchange of macromolecules as well as cells between tissues and blood
101
What are the sites and functions of sinusoids or discontinuous capillaries?
1- In bone marrow: Allow migration of blood cells, to the general circulation. - Have slow circulation → low O2 tension → stimulate erythropoiesis.
2- In the spleen: Store and filter the blood.
3- In the liver: Allow the blood to come into contact with the hepatocytes.
4- In endocrine glands: Allow migration of hormones to general circulation
102
What are the functions of capillaries?
Selective exchange of materials from blood to tissue and vice versa.
103
What are the functions of endothelial cells?
Permeability + secretion of VIP
- Act as a permeability barrier.
- Synthesize collagen and proteoglycans for basement membrane maintenance.
- Synthesize and secrete molecules that promote protective thrombus formation, e.g. von Willebrand factor (Factor VIII).
- Secrete vasoactive factors control blood flow, e.g. nitrous oxide, vasoactive peptides such as endothelin.
- Produce molecules that mediate the acute inflammatory reaction, e.g IL 1, 6, and 8, cell adhesion molecules.
104
What is the definition of AV Shaunts?
Are blood channels, which allow the blood to pass directly from the arteries and arterioles to the veins or venules without its having to go through capillaries, metarterioles, or preferential channels.
105
What are the types of AV shunts and their sites?
- Direct connections: Between an arteriole and a venule by side branch as found in the placenta.
- Glomus or complicated side: branch present in skin, ear pinna, toes, and nail bed.
106
What is the structure of AV shunts?
- Are similar to the arterioles on their arterial side and similar to the venules on the venous side.
- The intermediate segment of the A-V shunt
1- The lumen decreases gradually towards the venous side.
2- The internal elastic lamina disappears towards the venous side.
3- The media is well-developed, rich in longitudinal smooth muscles, and contains myoepithelial cells which act as sphincters.
4- The adventitia becomes thicker at the venous side.
107
What are the sites of AV shunts?
Exposed parts as tips of fingers, toes, external ear, nose, lip, and tongue.
Internal organs such as stomach, intestine, liver, endocrine gland, uterus, placenta and
sympathetic ganglia.
108
What is the function of AV shunts?
Conserve the body temperature; dilate in cold weather while constricting in hot weather.
Regulate the blood flow to the organs according to their need.
When dilating the venous return is increased and vice versa.
109
What is the definition of blood?
It is the fluid of life contained in the closed circulatory system.
110
What is the blood composed of?
Contents:
Cells:- 45% of bl. volume
Plasma:- 55% of bl. volume
111
What is the definition of blood cells?
Free C.T cells, produced by hematopoietic tissue, are suspended in blood plasma.
112
What are the types of blood cells?
1. RBCs 2. WBCs 3. Platelets
113
What is the lifespan of red blood cells (erythrocytes)?
120 days (destroyed by macrophage of liver spleen & bone marrow)
114
What is the shape of red blood cells?
Normal shape:
single RBC looks → Rounded biconcave discs.
If in groups → Rouleaux Formation
115
What is the diameter of red blood cells? What happens in case of an increase or decrease in the diameter?
6 – 9 μm (7.5μm):
If < 6 μm → microcytic anemia
if > 9 μm → macrocytic anemia
116
What are the color and the stains of RBCs?
Color:
Single RBC → greenish-yellow
One drop appears red due to the large no. of RBCs
In stained sections: "by Leishman stains" "no blueness due to absence of nuclei"
normal HB appears acidophilic with a pale center.
Less HB pale (hypochromic)
More HB deeply stained periphery with stained center (hyperchromic)
117
What is the number of RBCs and what is the device used to count them?
- It is counted by hemocytometer.
- Males: 5 – 5.5 m/mm
- Females: 4.5 – 5 m/mm
118
What are the abnormalities related to the number of RBCs?
↑ number → polycythemia.
↓number→ anemia "Even if the RBCs are large-sized"
119
What is the structure of RBCs?
Non-nucleated cells.
No organoids but filled with HB.
Surrounded by a cell membrane that is plastic "to allow more permeability" and has selective permeability. "To gases not to HB"
Contain important enzymes: carbonic anhydrase enzyme.
120
How do RBCs adapt to their function?
The cell membrane is highly selective
Highly plastic cell membrane
Absence of a nucleus and all organoids to give more space to HB inside the cell
Biconcave surface of the RBCs hits surface area through which gases exchange takes place
121
What is the definition of white blood cells?
True nucleated cells with organoids and inclusions, but no HB.
122
What is the color of white blood cells?
Single WBC is colorless but aggregated WBCs appear white.
123
What is the number of white blood cells?
❖ Total Leucocytic count:
The total number of leucocytes in the blood (4000-11000/mm3).
"Much less than RBCs"
❖ Differential leucocytic count:
Percentage of each type of leucocyte in blood.
124
What are abnormalities related to the number of white blood cells?
↑ Number → leukocytosis.
↓ Number → leukopenia.
125
What are the causes of anemia?
* deficiency of Fe, VitB12
* Hge: as in hemorrhagic anemia
* Haemolysis: as in hemolytic anemia
* Malfunction of B.M.: as in Aplastic anemia
126
What are the causes of polycythemia?
▪Haemoconcentration as in dehydration
| ▪increased producion from the bone marrow
127
What are the causes of leukocytosis?
Physiological:
```
Pregnancy.
Newborns.
Cold bath & cold wind.
Sun rays.
Heavy meals.
```
Pathological:
Acute and chronic infections
128
What are the causes of leukopenia?
Viral diseases.
Typhoid fever.
Irradiation.
Broad-spectrum antibiotics.
129
What are the types of white blood cells?
❖ Are classified into 2 types according to cytoplasmic granules:
granular (their cytoplasm contains granules)
agranular their cytoplasm contains no granules
130
Describe neutrophils according to percentage, diameter, LM, and functions.
percentage: 60-75 %
diameter: 10-12 μm
LM:
Nucleus: Darkly stained. Segmented (2-5 segments)
Cytoplasm: Fine neutrophilic granules.
functions:
1) Defense against microorganism "by 2"
2) Secrete proteolytic enzymes
3) Stimulate BM during infections to produce more leucocytes (neutrophilia)
4) Attract monocytes to the infected area.
5) Pus formation. "NEUTROPHILS AND MACROPHAGE"
6) Secrete trephone → wound healing. "Help platelets"
131
Describe basophils according to percentage, diameter, LM, and functions.
percentage: 0.5-1 %
diameter: 10-12 μm "like neutrophils"
LM:
- Nucleus: Lightly stained, Irregular, Obscured "masked" by cytoplasmic granules.
- Cytoplasm: large basophilic granules containing Histamine & heparin. "Antagonize eosinophils"
functions:
1) Produce histamine & heparin during allergy. "Inc allergy to stimulate the immune system"
2) Release eosinophil chemotactic factor.
132
Describe eosinophils according to percentage, diameter, LM, and functions.
percentage: 2 -5 %
diameter: 12-15 μm "bigger than neutrophils"
LM:
- Nucleus: Less darkly stained, bilobed, or horse-shoe shaped
- Cytoplasm: large acidophilic refractile "shiny" granules containing Histaminase & sulphatase enzymes. "Anti-allergic cells"
functions:
Attracted to the site of allergy → anti-allergic action through:
1) Phagocytosis of Ag-Ab complex.
2) Histaminase & sulphatase → destroy excess histamine & other substances causing the allergy.
133
What is the percentage of lymphocytes in detail?
Overall: 25-30%
Small: 15-20%
Medium: 5-10%
134
what is the diameter of small and medium lymphocytes respectively?
6-8 microns “similar to RBCs”
10-12 microns “like neutrophils and basophils”
135
What is the Shape of the nucleus of small lymphocytes?
- Small, rounded
| - Deeply stained
136
What is the shape of the nucleus of medium lymphocytes?
- Large, indented
| - Lightly stained
137
What is the shape of the cytoplasm of small lymphocytes?
A little rim around the nucleus
| Pale blue
138
What is the shape of the cytoplasm of medium lymphocytes?
Abundant
| More basophilic
139
Compare between T-lymphocytes and B-lymphocytes
Return to page 7 in L1B2
140
Describe monocytes according to percentage, diameter, LM, functions.
PERCENTAGE: 3-8 %
DIAMETER: 15-20 microns "largest in the blood film"
LM:
- Nucleus: large, horse-shoe "like eosinophils" (kidney) shaped, less condensed chromatin
- Cytoplasm: non-granular pale blue (frosted glass appearance).
FUNCTIONS:
1) Phagocytic.
2) Migrate by amoeboid movement "by pseudopodia" through the wall of capillaries and venules into the surrounding C.T. → macrophages.
141
What is the definition of blood platelets (thrombocytes)?
Fragments of cytoplasm covered with a membrane with no nucleus (not true cells).
142
What is the origin of platelets?
Megakaryocytes "largest cell in blood film"
143
What is the size of platelets?
2 - 4 μm. “Smallest in blood film”
144
What is the lifespan of platelets?
5-10 days.
145
What is the shape of platelets?
oval or rounded discs. “Not biconcave”
146
What is the number of platelets?
150.000 - 400.000 / mm3 “in-between”
147
What Is the LM of platelets? "By leishmaniasis stain"
Oval or rounded, non-nucleated discs.
Outer pale blue transparent part (hyalomere).
Central granular part (granulomere). "Opposite to RBCs"
148
What is the EM structure of platelets?
1) Cell membrane:
Irregular, covered with a thick cell coat. "Glycocalyx"
2) Hyalomere:
Tubules & vesicles.
Actin-like filaments & microtubules.
```
3) Granulomere:
α granules: fibrinogen.
β granules: mitochondria.
δ granules: serotonin, ATP, ADP, and calcium.
λ granules: lysosomes.
Glycogen granules.
```
149
What is the function of platelets?
(Hemostasis)
1) Serotonin → V.C. “Delta granules”
2) Platelet aggregation.
3) Red thrombus (coagulation):
- Thromboplastin changes prothrombin into thrombin → change fibrinogen into fibrin network → attraction of RBCs → closes blood vessels and stops bleeding
150
What is the lymphatic system comprised of?
- lymphatic vessels, which transport interstitial fluid (lymph) back to the blood circulation
- The lymphoid tissue which house lymphocytes and other cells of the body's immune defense system
151
What are the types of organs in the Lymphatic system?
1ry lymphatic organs: Sites where lymphocytes mature and become immunocompetent "has function" (B cells in bone marrow and T cells in the thymus).
2ry lymphatic organs: Mature lymphocytes are distributed via blood Or lymph to secondary lymphoid organs (e.g., lymph nodes, spleen) where they await activation.
152
What is a description of the thymus?
A flattened bilobed organ lying behind the sternum.
153
What are the Steps of development of the thymus?
It continues to enlarge up to puberty but then undergoes a slow involution becoming replaced by adipose tissue.
154
What is the Thymus formed of?
Formed of:
1) Stroma
2) Parenchyma
"Any parenchymal organ (those with no lumen)"
155
What is the structure of the stroma of the thymus?
- Capsule: thin loose C.T.
- Trabeculae: thin, divide gland into 2 lobes then, subdivided into incomplete lobules.
" + reticular fiber network that forms the floor of cells"
156
What is the structure of the parenchyma of the thymus?
Each lobule is formed of:
- Cortex: outer dark part (high content of lymphocytes). "As it is the site of development"
- Medulla: central pale part of the thymus lobule (due to low content of lymphocytes).
157
What are the cells found in the cortex of the thymus?
1. Lymphoblasts (thymocytes): In the outer cortex.
- Have dark nuclei "inactive" and are derived from the CFUs (Colony forming units) in the bone marrow.
2. T- lymphocytes:
- Deep in of the cortex.
- Numerous, derived from the lymphoblasts.
- Migrate to the medulla.
3. Few macrophages:
4. Reticular "has processes" epithelial cells "endothelial characters" : Branched cells with a pale nucleus. "Secrete thymic hormones"
158
What are the cells found in the medulla of the thymus?
1. T- lymphocytes:
- Less numerous
- They have completed their development in the cortex, then migrate to the medulla.
2. Reticular epithelial cells. "Less numerous"
3. Few macrophages "less numerous"
4. Hassall’s corpuscles: A central hyaline acidophilic mass "Remaining of the cytoplasm and cell membrane of T-sales" surrounded by concentric layers of reticular epithelial cells.
159
What is the function of the thymus gland?
- Production of T- lymphocytes: In the cortex, then migrate to the medulla post capillary venule blood circulation the lymph node and the spleen where they settle to produce T- lymphocytes
throughout life.
- It is essential for the normal development of the lymphoid tissue "t-cells" in early life
160
What is the histological structure of the lymphoid follicles or lymphoid nodule “Structural and functional unit of lymphatic system”?
- Spherical basophilic mass of small lymphocytes mainly B lymphocytes and few T lymphocytes with a rich network of reticular fibers supporting the cells.
- It is not encapsulated with connective tissue. "Unlike the thymus"
161
What is the size of lymphoid follicles?
Lymphoid nodules vary widely in size, measuring a few hundred micrometers to one mm in diameter.
162
What are the sites of lymphoid nodules?
- They are found free in many connective tissues in the body.
- They are also present within lymph nodes, spleen, and tonsils, but not in the thymus which contains only T cells.
163
What are the types of lymphoid follicles?
Primary and secondary
164
What is the shape of primary follicles?
Primary follicle without germinal center
165
What is the shape of secondary follicles?
- Has germinal center: Which is a pale central area formed as a result of exposure to infection or antigen, so the small B- lymphocytes (have dark nuclei) develop into activated medium sized lymphocytes (have pale nuclei) which aggregate in the center of the primary follicle forming a pale area called germinal center.
166
What is the definition of the lymph node?
Lymph nodes are bean-shaped, encapsulated structures, generally 2–10 mm in diameter “ Unlike lymphoid follicles which are 1 mm at max” , distributed throughout the body along the course of the lymph
167
What is a lymph node formed of?
- Stroma.
| - Parenchyma.
168
Mention the structure of the stroma of lymph nodes
- Capsule:
✓ Dense fibrous "C.T Like most capsules"
✓ Penetrated by afferent lymphatics at the convex surface of the lymph node.
✓ Thickened at the hilum through which arteries and nerves enter and veins and efferent lymphatics leave the node
- Trabeculae:
✓ They arise from the capsule.
✓ They divide the cortex into cortical compartments and the medulla into irregular areas.
- Reticular fibers:
✓ They form network holding the parenchymal cells in its
meshes.
✓ They appear only with silver stain.
✓ The network is more condensed at the site of lymphoid follicles and the medullary cords.
169
Mention the structure of the parenchyma of lymph nodes
- The cortex:
✓ It is formed of lymphatic follicles (primary or secondary)
surrounded by lymph sinuses.
- Lymph sinuses:
✓ They are spaces surrounding the cortical lymphatic follicles and the medullary cords.
✓ They contain lymph, lymphocytes and macrophages.
- The medulla:
✓ It is formed of irregular medullary cords (as follicles but
arranged in the form of cords) surrounded by lymph sinuses.
170
What is the function of lymph nodes?
- Filtration of lymph by the macrophages of lymph sinuses.
- Humoral immunity by B-lymphocytes which produce antibodies.
- Cell mediated immunity by T-lymphocytes which when activated form killer cells to destroy the antigens.
171
What is the structure of MALT?
Large and diffuse collections of lymphocytes, plasma cells, and lymphoid nodules present in the mucosa of the digestive, respiratory, and genitourinary tracts
172
Give examples for MALT.
As the tonsils, the Peyer patches in the ileum and aggregates of lymphoid follicles in the appendix
173
What is the definition of tonsils?
Masses of lymphatic tissue "Lymphatic follicles + diffuse lymphatic tissue" present in the lamina propria "epithelium + C.T" of a mucous membrane.
174
What are types of tonsils?
According to their location
• Palatine tonsil. "اللوز"
• Pharyngeal tonsil. "اللحمية"
• Lingual tonsil.
175
What is the function of tonsils?
Quick defense mechanism through formation of antibodies against infective agents taken with food or air
176
What is the definition of palatine tonsil?
Two masses of lymphatic tissue embedded in the C.T. under the mucous membrane of oro-pharynx
177
What is the structure of palatine tonsil?
1- Non-keratinized stratified squamous: Cover its surface & dips into the underlying lymphatic tissue forming primary and secondary tonsillar crypts.
2- Lymphatic tissue: types:
- Lymphatic nodules → Primary or secondary.
- Diffuse lymphatic tissue: formed of lymphocytes and plasma cells. It occupies the areas between the lymphatic nodules.
3- Capsule: Dense C.T. separates the tonsils from the muscular wall of the pharynx.
178
What’s the definition of pharyngeal tonsil?
Single mass of lymphatic tissue present in nasopharynx.
179
What is the structure of pharyngeal tonsils?
Covered by pseudo-stratified columnar ciliated epithelium which forms folds. "Small folds not crypts"
180
What does hypertrophied pharyngeal tonsil result from and what is it called?
Hypertrophied pharyngeal tonsils resulting from chronic inflammation are called adenoids.
181
What is the definition of lingual tonsils?
They are small collections of lymphatic tissue in the C.T
182
What is the definition of the spleen?
The spleen is the largest single accumulation of lymphoid tissue in the body.
183
What is the structure of the spleen?
Stroma:
Capsule:
✓ Thick dense fibrous connective tissue capsule, containing smooth muscle fibers "To push blood in case of emergency" and penetrated by afferent lymphatics.
Trabeculae:
✓ Divide the spleen into lobules, containing smooth muscle fibers
Reticular network→ similar to that of lymph node.
Parenchyma: It is formed of splenic lobules.
Each splenic lobule includes:
- White pulp:
• White pulp is a lymphatic follicle with central artery which is eccentric in position.
• The white pulp may contain germinal center.
• They are scattered all over the spleen.
- Red pulp:
• It occupies the areas between the white pulps.
• The red pulp is formed of splenic cords and blood sinusoids.
- Blood sinusoids: Irregular blood channels surrounded by macrophages. "For filtration"
- Splenic cords (Billroth cords): Irregular masses of lymphatic tissue mixed with blood cells (RBCs & WBC), fill spaces between the blood sinusoids.
184
What is the function of the spleen?
Humoral and cell mediated immunity.
The only lymphoid organ involved in filtration of blood.
It is also the main site of destruction of aged erythrocytes.
Storage of blood
185
Compare between the lymph node and spleen according to:
```
Number
Capsules
parenchyma
Sinuses
Function
```
Number: Numerous, widely distributed in the body - Single organ, in the abdomen.
Capsule: Dense C.T. - Dense C.T. with smooth muscles
Parenchyma:
Cortex → lymph follicles (no central artery).
Medulla → medullary cords
-
White pulp →lymph follicles (with central artery)
Red Pulp →blood & diffuse lymph tissue
Sinuses: Lymph sinuses (contain lymph) - Blood sinusoids (contain blood)
Function:
Filtration of lymph
Production of small
-
lymphocyte → humoral & cell mediated immunity
Filtration & storage of blood
Destruction of old RBCs
Y1B3 (CVS & IBL) 📘
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