dr. julia b. beltran, fpogs, fpsa

OBJECTIVES:1.Understand the histologic features of the blood vessels a. Name and describe the characteristics of each layer b. Describe the ultrastructure and functions c. Name and describe the different types of blood vessels d. Define portal system, rete mirabile, glomus and valves2. Know the histologic features of the heart a. layers b. types of muscles c. cardiac skeleton3. Comprehend the histology of the lymph vascular system

functions:

1.Transport of oxygen and nutrients, and carbon dioxide *

2. Temperature regulation

3. Distribution of molecules and cells

Functional components:

1.blood vascular system2.lymph vascular system

basic architecture:

1.Tunica intima2.Tunica media3.Tunica adventitia

General composition :1. Tunica intima : endothelium = layer of endothelial cells

subendothelial layer = loose c.t. with smooth muscle cells Internal elastic lamina/membrane or fenestrated membrane of Henle

* scalloped appearance

2. Tunica media : smooth muscles, elastic and collagen fibers, and proteoglycans External elastic lamina/membrane

3. Tunica adventitia : collagenous and elastic fibers , Type III

Endothelial cells:

1.permeability barrier2.Basement membrane maintenance – collagens & proteoglycans3.Fc VIII (Von Willebrand) secretion – thrombus formation

(Weibel-Palade bodies)4.Minimize pathological thrombus – prostacyclin,

thrombomodulin, NO2 (inhibits platelet adhesion )5.Controls blood flow – vasoactive factors (prostacyclin,

peptides as endothelin)6.Mediate acute inflammatory reaction – IL 1,6,8 (cell

adhesion molecules)7. Produce growth factors – fibroblast GF, platelet- derived GF, blood colony stimulating factor

BLOOD VESSELS :

- tubular structures that convey blood away and towards the heart

Arteries : toward organ and tissueCapillaries : anastomosing channels of small caliber vessels providing interchange of substances.Veins : returns blood to the heart

Arteries : 3 walls

1. Large arteries :> called conducting / elastic arteries t. media with elastic tissue in the form of fenestrated elastic

sheets or lamina

2. Medium sized arteries :> also called distributing arteries thicker tunica media with 25 – 40 layers of muscles Fenestrated membrane of Henle> ( + ) vasa vasorum***

3. Arteriole and small arteries : transitional arterioles / procapillary or metaarteriole : with

isolated spirally arranged smooth muscle fibers; no EEL 0.3 mm diameter regulate distribution of blood to the capillary beds Maintain blood pressure

Vasa vasorum: blood supply of blood vessel

Nervi vasorum: nerve supply of blood vessel

Myointimal cells:

-Fibroblasts-Early changes of atherosclerosis

1. Cerebral and dural arteries2. Arteries of the lungs3. Umbilical arteries4. Penile and pudic arteires5. Mixed / hybrid arteries – common and external iliac, external carotid6. Carotid and aortic bodies – chemoreceptor

organs

Capillaries :

- thin walled tubes - 7– 9 um in diameter - layers: tunica intima t.adventitia - microcirculation

- A-V shunts - pericytes – endothelium,

contractile - except: mucous ct, cartilage, epithelial cells, calcareous matrix of bones

Types ( according to wall structure )I. Continuous – complete layer of cytoplasm in each cell - lack of pores in the wall

- in muscle and nervous tissue

2. Fenestrated – with pores or fenestrae** in walls - in kidney, intestine and endocrine glands ** diaphragm

3. Sinusoidal - with tortuous path and greatly enlarged diameter - absence of continuous lining in walls - presence of multiple fenestration - presence of phagocytic activity - absence of continuous basal lamina - found in liver and hematopoietic organs

4. Sinuses - barrel-like arrangement of cells - spleen

The microcirculation: components: - arteriole, pre-capillary sphincters,

- capillaries- postcapillary venules, collecting

venules, muscular venules - arterial capillaries - central/preferential channels - branches channels

networking: control: - arterioles,

metarterioles, pre-capillary sphincters A-V shunts

autoregulation: - oxygen, lactic acid

* microvilli, glycoprotein layer, microfilaments, pinocytic vesicles (caveolae – glycoprotein, site of angiotensin conversion)

Exchange in continuous capillary:

1.Passive diffusion2.Pinocytic vesicles (caveolae) – large pore system3. Intercellular junctions (gap junctions & desmosomes

* Blood-tissue barrier – zonula occludens

Venous system:

Veins : - larger caliber , thinner walls than arteries

3 layers : t. adventitia – collagenous c.t. in large amount

t. media – sparse circular muscle loosely arranged

t. intima – endothelial layer

Post-capillary venules :- smallest, union of capillaries- sluggish flow- entry/exit of WBCs

Collecting venules:- larger, more pericytes

Muscular venules:- larger- smooth muscle layer

* Inflammatory process – histamine, serotonin etc.

The venous system:

Control of flow: 1. pressure gradient 2. skeletal muscles 3. valves (veins >2 mm)

Inferior vena cava – longitudinal smooth muscle

1. No tunica media - cerebral, meningeal, dural sinuses,retina, penile, placenta2. Rich in smooth muscle – gravid uterus, limbs, umbilical, mesenteric3. With cardiac muscle – vena cava, pulmonary

1. Portal system 2. Rete mirabile / arterial portal system3. Valves4. Arterio-venous anastomosis - exposed parts - temperature regulation - glomus

ArteryArtery VeinVeinLumenLumen smallersmaller biggerbigger

Thickness of wallThickness of wall thickerthicker ThinnerThinner

Thickest coatThickest coat Tunica mediaTunica media Tunica adventitiaTunica adventitia

Rigidity of wallRigidity of wall More rigidMore rigid Less rigidLess rigid

Internal elastic Internal elastic membranemembrane

presentpresent absentabsent

ValvesValves absentabsent presentpresent

Muscles & elastic Muscles & elastic tissuestissues

More abundantMore abundant Less abundantLess abundant

Vasa vasorumVasa vasorum Extend up to Extend up to tunica mediatunica media

Extend up to Extend up to tunica intimatunica intima

HEART :

4 chambers

3 layers endocardium : glistening layer , endothelial cells irregularly shaped, polygonal with oval or rounded nucleus subendocardium : loose c.t. , thin layer of collagenous , elastic fibers and b.v.myocardium : cardiac cell arranged in tracts or bundles , with strands of c.t. and vascular network in between cells.

Purkinje fibers : modified cardiac muscle cell located in AV Bundle, reduced number of myofibrils, more sarcoplasm and glycogen, more rounded nuclei in groups of 2 or more, larger diameter, lack transverse tubulesepicardium : vessel layer of pericardium lining of single layer of flat or cuboidal mesothelial cells. subepicardium: contain b.v., nerves, and fat cells.

Walls :

1. Endocardium

2. Myocardium

3. Epicardium

• endothelium – simple squamous• subendocardium – LCT

• cardiac muscle tissue – •striated involuntary muscle•Cylindrical / elongated with branching ends•Mono/binucleated

• visceral layer of pericardium• lined by mesothelial cells• subepicardium

•Purkinje fiber – impulse generating & conducting fibers

LAW

MV

PM

LVW

EpiEn

CT

Endocardium. Human. Paraffin section. x 132. The endocardium, the innermost layer of the heart, is lined by a simple squamous epithelium that is continuous with the endothelia of the various blood vessels entering or exiting the heart. The endocardium is composed of three layers, the innermost of which consists of the endothelium (En) and the subendothelial connective tissue (CT) whose collagenous fibers and connective tissue cell nuclei (N) are readily evident. The middle layer of the endocardium, although composed of dense collagenous and elastic fibers and some smooth muscle cells, is occupied in this photomicrograph by branches of the conducting system of the heart, the Purkinje fibers (PF). The third layer of the endocardium borders the thick myocardium (My) and is composed of looser connective tissue elements housing blood vessels, occasional adipocytes, and additional connective tissue cells.

En

CTPFMy

Purkinje cells of the impulse-conducting system. They are characterized by a reduced number of myofibrils that are present mainly in the periphery of the muscle cell. The light area around the nuclei of the conducting cells is caused by

a local accumulation of glycogen. High magnification. H&E stain.

Purkinje fiber – impulse generating & conducting fibersmodified cardiac muscle cell

located in AV Bundle.reduced number of myofibrils more sarcoplasm and

glycogenmore rounded nucleus in groups of 2 or morelarger diameterlack transverse tubules of cardiac muscle

Cardiac Skeleton :Cardiac Skeleton :

• dense c.t.

1. Septum membranaceum• Fibrous portion of interventricular septum

2. Trigona Fibrosa• Between arterial foramen & AV canals• chondroid

3. Annuli Fibrosi – • Fibrous ring • Attachment of fibers of atria , ventricles & AV valves

Impulse Conducting System :Impulse Conducting System :

1. SA Node - pacemaker of the heart ; sulcus terminalis area

2. AV node – below posterior leaf of aortic valve

3. Bundle of His – trigonum fibrosum dextrus

4. Right and Left branches

5. Subendocardial network of PF

Lymph vascular system:

- Lymph – exits the artery, enters the veins - no RBC

- microcirculation - 2% of plasma exchange

- vessels: more permeable (thin endothelium) no basement membrane no pericytes anchoring filaments valves – reticulin fibers/scanty ground

substance

- two main vessels: thoracic duct right lymphatic duct

- lymph nodes, lymphatic glands, lymphatic tissues

NOT: CNS, bone marrow, eyeball

internal ear, placenta

* Edema – excess tissue fluid

1. Atherosclerosis2. Arteriosclerosis3. Thrombophlebitis4. Varicose veins – hemorrhoids5. Myocardial infarction6. Coronary heart disease7. Rheumatic heart disease

Get ¼ sheet of paper

1. Capillary of the muscle

2. Nerve that supply the blood vessel

3. Thickest coat of the artery

4. Most common component of the lymph

5. One characteristic of the Purkinke fiber

6. Deposition of fatty plaques in the arterial wall

7. The vein has membrane of Henle – True or False

8. Where actual exchange of gases takes place

9. Lining epithelium of the blood vessels

10. Visceral outermost covering of the heart

Submit your papers at

The count of 10

1. Capillary of the muscle – continuous2. Nerve that supply the blood vessel – nervi

vasorum3. Thickest coat of the artery – tunica media4. Most common component of the lymph –

lymphocytes5. One characteristic of the Purkinke fiber –6. Deposition of fatty plaques in the arterial wall – atherosclerosis7. The vein has membrane of Henle – True 8. Where actual exchange of gases takes place – microcirculation or capillary bed9. Lining epithelium of the blood vessels –

endothelium10. Visceral outermost covering of the heart -

epicardium