CIRCULATORY SYSTEM HISTOLOY JANIQUERS BOOK

Detail notes of circulatory histology

2. CIRCULATORY SYSTEM
By: Lilian B. Rosario, MD, FPPS

3. The Circulatory System:
-2 Connected systems:
-I. Blood Vascular system ( Cardiovascular System)
- A. Heart
- B. Blood Vessels
- 1. Arteries
- a. Elastic
- b. Muscular
- c. Arterioles/ metarterioles
- 2. Capillaries
- 3. Veins
- a. Medium sized
- b. Large
- c. Venules
-II. Lymphatic Vascular System

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5. Blood Vascular System:
-Has 2 Circuits:
- 1. Pulmonary Circuit
- - takes Oxygen-poor blood
to the Lungs to
- become Oxygenated and
returns it to the
- Left side of the Heart.
- 2. Systemic Circuit
- - Oxygen-rich blood is
propelled via this
- circuit distributing it to
the remainder of the
- body to be returned to
the Right side of the
- Heart, completing the
cycle.

6. A. Heart
-Muscular pump
--4 Chambers:
- Atria ( L / R)
- Ventricles (L/ R)
-- 4 Valves:
- Mitral/ Tricuspid
- Aortic/Pulmonic
-- 3 Layers of the wall:
- 1.Epicardium- outer
- most
- 2. Myocardium-
- middle
- 3. Endocardium-
- innermost

7. 3 Layers;: Wall
-EPICARDIUM- outermost
- covered by Simple Squamous meso-
- thelium,deep to which is fibroelas-
- tic tissue. Deepest: Adipose tissue
- (nerves & coronary vessels)
-MYOCARDIUM- occupies most of the
- wall. Bundles of Cardiac muscles
- attached to Collagenous Con tissue
- (skeleton of the heart)
-ENDOCARDIUM- lining of Atria &
- Ventricles. Simple Sq. endothelium
- & Subendothelium Con tissue
- - formation of heart Valves.

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9. Heart: Generation & Conduction of IMPULSE
Some Cardiac m. fibers are specialized to regulate
the sequence of Atrial- Ventricular contractions:
Sinoatrial Node (SA): ‘pace- maker’; juncture of SVC
and R atrium; the impulse cause the contraction
of the atrial muscles; blood from atria enters
ventricles.
Atrioventricular Node (AV) : medial wall of R
ventricle near Tricuspid valve/ atrial myocardium.
receives impulse from Sanode.
Bundle of HIS: arises from AV Node, bifurcates into
septum (septum membranaceum) to both
ventricles
Purkinje Fiber: subendocardium fibers, merge and
become indistinguishable from cells of

10. GENERATION & CONDUCTION of IMPULSE

11. HEART VALVES:
Atrioventricular valves:
ventricles
Semilunar Valves: aorta/
pulmonary
Mitral (Bicuspid) & Tricuspid
valves
Aortic & Pulmonic valves

12. B. Blood Vessels: ARTERIES
3 TYPES:
1.ELASTIC A. – Largest, arise directly from the heart; -subject
to cyclic changes of blood pressure, to compensate for pressure=
Elastic fibers in its walls= assist
assist in maintenance of BP in between heart beats.
2. MUSCULAR A.- comprise most of the named arteries.
- distribute blood to various organs; their Tunica media
composed of many Smooth muscle cells.
*VASA VASORUM- Tunica adventitia, small blood vessels that supply
both Elastic A. and Muscular A. (supply the Tunica media and
adventitia of that vessel)
3. ARTERIOLES – Regulates BP and the distribution of blood to Capillary
beds via Vasoconstriction/ Vasodilatation of
vessel walls.

13. ARTERIES : 3 LAYERS
Tunica Intima – innermost;
simple squamous
endothelial cells lining
the lumen &
subendothelial CT
Tunica Media – thickest;
circularly arranged sm
m. cells & fibroelastic
CT (elastic content
increases with the size
of vessel)
Tunica Adventitia –
outermost layer;
fibroelastic CT; in larger
vessels, houses the
Vasa Vasorum

14. ARTERY: Muscular artery Elastic artery ( AORTA )

15. Blood vessel: ARTERIOLES
-Smallest arteries, regulates BP
METARTELIOLES- terminal ends of arterioles; with
presence of incomplete rings of smooth m.cells (‘
Pre-
capillary sphincters’) that encircle the origins of
the cap.
- form the arterial (proximal) end of a ‘Central
Channel’; delivers blood into capillary bed
-Venous (distal) of the central channel
‘Thoroughfare
-Channel’ : drains blood from the capillary bed-
venules.
-Contraction of Precap. Sph.. shunts blood into

16. ARTERIOLES: 3 Layers:
Arterial vessels: diameter < 100 um
1.T. Intima- Endothelium & variable
amount of subendothelial C.T.
- Internal elastic lamina is present in
larger arterioles, But ABSENT
in Smaller arterioles.
2. T. Media- spirally arranged smooth
m fibers up to 3 layers
- External elastic lamina, present in
larger arterioles, but ABSENT in
smaller ones,
3. T.Adventitia- collagenous & elastic
CT, whose thickness approaches
that of the T. Media

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18. CAPILLARIES:
-Form the thin-walled networks, supplied
by arterioles/ metarterioles
and drained by venules.
-Circumvented by specialized vessels
-‘Arteriovenous anastomoses’ interposed
between Arterial/Venous.
-Composed: Endothelial cells; Basal
laminae & Pericytes
-Has No Smooth m. cells= do not exhibit
Vasomotor activities
-Control of blood flow is at Terminal
arterioles/metarterioles (smooth m.)
-3 TYPES:
-Fenestrated
-Continuous Cap
-Discontinuous ( Sinusoids) cap

19. CAPILLARIES:
Endothelial Cells form a narrow vascular
Channel, surrounded by Basal Lamina &
occasional Pericytes.
-Permeability is dependent on the
Endothelial cells ( thru Fenestrae or gaps in
Intercellular junction ‘Diapedesis’ ) & size,
shape, charge of traversing substance
transported by Carrier proteins.
-Deactivates substances: prostaglandins,
serotonin, bradykinin
-Catabolize lipoproteins
-Convert Angiotensin 1 to 2
-Release prostacyclins, promote fibrinolyss
- Binding sites/ release tissue factors

20. CAPILLARIES : 3 TYPES:
1.Continuous : lack fenestrae
-possess continuous basal lamina;
occ’l pinocytotic vesicles
- periph n.fibers, skeletal m
2. Fenestrated: penetrated by
large diaphragm-covered pores;
-posses pinocytic vesicles w/
cont. basal lamina
- endo glands:pancreas, kidney gl
3. Sinusoidal : much larger than
fenestrated/ continuous cap
- discontinuous basal lamina
- gaps in intercellular junction
- no pinocytic vesicles
- liver, spleen, lymph nodes, BM

21. Blood vessel : VEINS
Conduct blood away from the body tissues and back to the heart.
Diameter are larger than arteries; thinner walled ( do not bear high
blood pressures); low pressure vessels
Many w/‘Valves’ in the lumen= prevents retrograde blood flw
3 concentric layers:
1.Tunica intima- subendothelial CT, valves may be evident
2. Tunica Media- fewer layers of smooth m cells than arteries
with collageous fibers interspersed w/ few elastic fibers
3. Tunica Adventitia- longitudinal smooth m cells, some collagen and
elastic fibers, Vasa Vasorum present
Vasodilator subs: serotonin and histamine act on small venules,
causing them to become ‘leaky’ by increasing intercellular
distances.

22. COMPARISSON LAYERS

23. VEINS: 3 TYPES OF VEINS: Large, Medium, Small
Large Veins:
Tunica Intima- displays thicker
subendothelial CT than the
medium sized veins
- have well defined Valves
Tunica Media-
- Not well defined
- some smooth m cells inters-
persed w/ collagenous/
elastic fibers
Tunica Adventitia – thickest;
- longitudinal smooth m
fibers w/ thick layers of
collagen and elastic fibers.
Vasa Vasorum commonly
present.

24. Veins: MEDIUM SIZED
Tunica Intima- has endothelium
&scant amt subendothelial CT
- occl’y pesent thin elastic lamina.
Valves maybe evident
Tunica Media- thinner than artery,
w/ few layers of smooth m cells
- fibers instead of circularly
disposed are Longitudinally
disposed.
- collagen interspersed w/ few
elastic fibers.
Tunica Adventitia- collagen/ elastic
fibers, some with smooth m cells.
Vasa vasorum noted to penetrate
even the T media

25. Veins: SMALL VEINS ‘’VENULES”
Possess much Larger lumina &
Thinner walls than arterioles
Tunica Intima- endothelium lies
on a very thin subendothelial CT
layer w/c increases w/ the size of
the vessel. Pericytes asso
frequently w/ smaller venules.
Tunica Media- Absent in smaller
venules; Larger venules has 1
or 2 layers of smooth m cells
Tunica Adventitia- collagenous
CT w/ Fibroblasts , some Elastic
fibers

26. General view : BLOOD VESSELS

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28. IIII. LYMPHATIC VESSELS blood vs lymph vessel
Collapsed; not discernable
Filled w/ lymph
Lumina contain No RBC
Lymphocytes present
Endothelium display Valves

29. LYMPHOID TISSUES

30. LYMPHOID TISSUE (LT): basis of Immune system of the body
DIFFUSE LT- occurs thru out
the body; under wet epithelial
membranes, loose CT contains
lymphoid cells: lymphocytes,
plasma cells, macrophages and
reticular cells.
- lymphoid cells are scattered in
pattern
NODULAR LT- lymphoid nodules
present a lighter germinal center
& darker peripheral ‘corona’
- Germinal centers- sites of
lymphocytes production
- Corona- newly formed B lympho-
cytes

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32. IMMUNE SYSTEM (IS) : The CELLS
-Relies on 2 Responses:
1.Cell Mediated Immune R
-interactions of Primary cell
components: Lymphocytes &
Antigen Presenting Cells (APC)
2. Humoral Immune Responses
- release of specific Antibodies
(Ab) against specific Antigens
(Ag)
- Abs (Immunoglobulins: Ig):
glycoproteins produced by
plasma cells
- 5 Classes Ig: G A M D E

33. CELLULAR & HUMORAL Immune Responses

34. IMMUNE SYSTEM (IS) : 2 Components
1. Innate IS or Non- Specific:
- not design to combat a specific Antigen (Ag)
- acts in a rapid fashion in response to pathogen- associated
molecule; has NO Immunologic memory
- consists: Complement; Toll like receptors; Mast cells;
Eosinophils; Neutrophils; Macrophages; NKC
2. Adaptive IS or Specific: 4 characteristics:
- Immunologic memory
- Immunologic specificity
- Immunologic diversity
- Capability to differentiate between Self & Non Self

35. Immune System: Cells ( INNATE)
Complement system- group of protein; flows freely
in the blood & quickly reach the site of invasion
to meet the invaders (Antigens/ pathogens).
When activated:
- attract Macrophages; coat intruders so that
phagocytes
can devour them; kill intruders
Phagocytes- cells specialized in finding invaders
- granulocytes: attacks invaders in large #s and eat
until they die. PUS in infected wound consists
chiefly of dead granulocytes
- Macrophages: slower to respond. Monocytes
(precursor). Monocytes that leave the blood
stream
turn into Macrophages

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37. IMMUNE SYSTEM: Cells : ADAPTIVE IMMUNE RESPONSE

38. Immune System: Adaptive Immune Response
Major Cellular components:
1. T Cells ( Thymus Cells)- Cell mediated immunity
-T helper cells(CD4) : produce cytokines that direct the
immune response
- Cytotoxic T cells (CD8): produces granules that contain
powerful enzymes which induce death of pathogen
infected cell.
2. B Cells ( Bone Marrow or Bursa derivative cells)- Humoral
Immunity : relating to Antibodies (Abs)
3. Natural Killer Cells (NK)
4. Antigen Presenting Cells (APC)

39. ADAPTIVE:

40. B & T cells How a T Cell works?

41. B Cell action: Plasma cells (Abs) & Memory cells

42. from APC to T Cell differentiation to activation of Bcell

43. NATURAL KILLER CELLS
-Distinguish infected cells or
tumors from Normal cells by
recognizing changes of a surface
molecule called
Major Histocompatibility
Complex (MCH) class 1
-Activated in response to a
group of cytokines: Interferons; &
release cyto-
toxic granules w/c destroyed
the altered cells
-NKC bec they don’t require
prior activation in order to kill cells
w/c are missing MHC 1

44. Immune system vs Pathogen cell

45. Histophysiology of the Immune System

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47. Lymphoid Organs:
Primary Lymphoid organs:
Thymus
Bone Marrow

Secondary Lymphoid Organs
1. Lymph Nodes
2. Tonsils
3. Spleen
4. Peyer’s Patches
5. Appendix

48. Primary: THYMUS
Bilobed organ: secretes
hormones( Thymosin &
Thymopoietin)- cause T
Lymphocytes to be immuno-
competent
Varies w/ Age (size)
-Infants: inferior neck &
extends into mediastinum &
partially overlies the heart
-Childhood: Increases in size
and most active
-Adolescence: stops growing
and
gradually atrophies

49. Primary: BONE MARROW
Spongy flexible tissue in the
interior of bones
Contain Stem cells (immture
cells) develop different cells
thru Hematopoiesis
The production of Lymphocytes
gives the key component to
lympahtic system
Function:
Multipotent stem cells that
differentiates into variety of cell
types
Barrier- inhibits immature cells
from leaving the marrow
Red Bone Marrow is the key
element of the lymphatic system
( IMMUNE SYSTEM)

50. BONE MARROW
2 Types:
Red Marrow( Medulla Ossium
Rubra)- hematopoietic
tissues- erythropoietic;
myelopoietic; other cells:
lymphoid lineage
Yellow Marrow (Medulla
Ossium Flava)- adipocytes
- With age more of Red
marrow is converted to
yellow marrow

51. Secondary: LYMPH NODES
Ovoid or Kidney shaped;
thru w/c Lymph is filtered
( elongated processes of
reticular cells) by exposure
to lymphoid cells
Parts:
Convex surface- receives
Afferent lymph vessel (Lv)
Hilum- b.v leave & entered
Effernt Lv & drain lymph
from the organ
Capsule- dense irregular CT

52. Lymph Nodes:
Septa- from Capsule, divides
the cortex to incomplete
compartments
Cortex- capsular & cortical
sinuses (B lympho; APC;
Macrophages; Reticular cells)
Paracortex- bet cortex/ medulla
-T lympho; APC; Macrophages
Medulla- medullary cords &
sinusoids
cords: T/B Cells; plasma cells

53. LYMPH NODES:
Medulla – Sinusoids area:
cont. w/ the capsular &
cortcal sinus; where
T/B Cells enter sinusoids
& leave the LN via
Efferent Lv

54. LYMPH NODES:

55. Secondary: TONSILS
Aggregates of incompletely
encapsulated lymphoid
tissue forming a ring around
the pharynx( oral/ nasal)
Tonsillar Rings:
-Palatine tonsils- either side of
post end of oral cavity
-Lingual Tonsils- lie at the
base of the tongue
-Pharyngeal tonsil- post wall
of nasopharynx
-Tubal Tonsils- surround the
openings of auditory tubes
into the pharynx

56. TONSILS:

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58. Secondary: SPLEEN
Largest accumulation of Lymphoid tissue ( Ab
forming
organ); filters blood
Capsule of dense irregular CT with Trabeculae
dividing pulp incompletely
-White pulp with lymphoid nodules
- Red pulp in between sinusoids, has reticular
fibers
reticular epith cells & macrophages
Abundant phagocytic cells- Go against Ag in
blood

59. SPLEEN : Structure - 2 distinct areas
White pulp – contain
mostly of lymphocytes
suspended on reticular
fibers
- involved in immune
functions
Red pulp- blood sinusoids
concerned with
disposing worn out
RBCs & pathogens

60. Secondary: PEYER’S PATCHES
Small masses of
lymphatic tissue “
Aggregated
lymphoid nodules” at
the Ileum
Similar to LN in structure,
except has No Capsule:
Non encapsulated
lymphatic tissue:
lymphatic Nodules –
tonsils/ appendix

61. PEYER’S patches:
Devoid of villi ; migratory M cells concentrated
w/in the surface of epith, allow selective
uptake of Ags
Special Epith cells: microfold cells line the side of
Pp facing intestinal lumen; while outer side
contains many
lymphoid cells and Lymphatic vessels
Functions:
Analyze and respond to Ags.
Ags are absorbed via endocytosis by Micofold
cells & are passed to the lymphoid tissue & are

62. PEYER’S PATCHES
Immune Response
Histo structure

63. Secondary: APPENDIX
Blind ended tube connected &
hangs from the cecum between
small & large intestines;
Length: 2-20 cm
Arrangement of layers of walls
similar with intestinal layers
except the outer layer of muscle
fibers is Continuous at the
muscularis externa

64. APPENDIX: Structure
Continuous M. externa
Presence of masses of lymphoid tissues
in Mucosa/ Submucosa; follicles w/ Pale
Germinal center

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