Cardiovascular Lymphatic Systems
I. Blood Vascular (Cardiovascular System)
A. General structure
1. Tunica intima [endocardium in the heart]
§ Innermost , next to lumen
§ Endothelium- simple sqamous lining, flattened nucleus, cells joined by zonula occludens junction
§ Basal lamina of endothelium
§ Subendothelial layer- longitudinal layers of collagen and elastic fibers
§ Separating intima from media is internal elastic lamina
2. Tunica media [myocardium in heart]
§ Middle layer
§ Smooth muscle cwlls spirally arranged perpendicular to long axis of vessel in concentric layers
§ Gap junctions between cells
§ Collagen fibers, elastic fibers and lamellae, proteoglycans
§ External elastic lamina- less distinct less distinct that internal elastic lamina (except in pulmonary arteries)
3. Tunica adventitia [epicardium in heart]
§ Blends into connective tissue surrounding vessles
§ Longitudinal collagen and elastic fibers, fibroblast, some smooth muscle
§ Vasa vasorum- vessels of the vessel
§ Nerves-sympathetic unmyelinated (norepinepherine) nerve fibers; do not extend into vasa vasorum
§ Thickest layer of vessels and venules
B. Components of Cardiovasular System
1. Heart
§ Double muscular pump
§ Right side receives blood from body and pumps it to lungs
§ Left side receives blood from lungs and pumps to body
§ Systole- ventricles eject blood at high pressure
§ Diastole-ventricles relax
2. Elastic arteries (conducting arteries)
§ Large arteries conductin blood from heart
§ Thick intima, multi-layered internal elastic lamina
§ 40-70 elastic laminae in media, stretch in response to bolus of blood (contract during diastole keep pressure up)
§ think adventitia with vasa vasorum
3. Muscular arteries (distributing arteries)
§ Distribute blood to body, flow adjusted by smooth muscle layers of media in response to sympathetic nerve stim.
§ Myoendothelial- junctions may mediate angiotensin regulation of blood pressure
§ Prominent internal elastic lamina, hallmark of vessles
§ 3-40 smooth muscle layers in media, neuromotor terminations
§ adventitia eequal in thickness to media, many elastic fibers visible
4. Arterioles
§ Internal elastic lamina present in arterioles
§ Media as 1-2 smooth muscle layers
§ Major role in regulating blood flow to capillary network by vasoconstriction vasodilation
§ Major site of resistance with vascular system
§ Increased arteriolar tone important mech of hypertension
§ Decreased arteriolar tone important mech in shock
§ Branch into metaarteriole with discontinuous smooth muscle cells, can slow blood flow
§ Precapillary sphincters can stop blood flow into capillaries
§ Control is neural and hormonal
5. Capillaries
§ Flexible and pliable
§ Permeability depends on characteristics of endothelial cells and basal lamina
§ Density dependent on metabolic activity. (high- myocardium and skeletal muscle; low- smooth muscle and dense connective tissue)
§ Pericytes- special longitudinally situated contractile mesenhcymal cells, constituting the “media” of capillaries
§ Few collagen fibers
§ Delivery of blood borne material to tissue and removal of waste products
§ Selective permeability barrier for large polypeptides, lipids and small molecule transport
§ Synthetic and metabolic system (angiotensin I-II, degradation of bradykinin, prostaglandins, norepinephrine, thrombin, lipoproteins, cholestrol)
§ Tremendous surface area in plexuses below epidermis allows for cooling of blood by “radiator effect”
§ 60,000 miles
§ Continuous- typical in brain and muscle, few caveolae and vesiclesin brain, brain blood barrier, continuous with basal lamina
§ Fenestrated-found in endocrine tissue, intestine, fenestrate with diaphragms in endocrine tissue absent in renal glomeruli, endothelially derived basal lamina
§ Sinusoidal- ovvur inliver, bone marrow, and spleen, larger diameter than other capillaries, numerous large fenestrae, no diaphragms, basal laminae discontinuous
6. Venules
§ Media consists of pericytes in postcapillary venules
§ 2-4 layers of smooth muscle
§ longitudinal collagen fibers present
§ low to high permeability for food fluid and cell exchange with surrounding tissue
§ vasoactive amines (serotonin, histamine) increase permeability (important in inflammation)
§ wall is thin as capillary
§ lumen is larger
§ high endothelial venules in lymphatic tissue: lymphocyte exit from blood stream into this tissue
7. Small to medium sized veins
§ One way valves (folds in intima, lined by endothelium) in veins
§ Media consits of 2-4 layers of smooth muscle cell mixed with collagen and elastic fibers.
§ Vasa vasorum penetrate deeply into media of veins
§ Adventitia well developed, thicker than media, some longitudinal smooth muscle cells
8. Large veins
§ Valves in intima
§ Media thin adventitia is thickest layer; large veinshave longitudinal bundles of smooth muscle in adventitia, in addition to collagen and elasti fibers, nerves, and vasa vasorum
§ Venae cavae, innominates, internal jugulars, portal, splenic, azygous, superior mesenteric, enal, adreal, external iliac, and femoral veins.
C. Identification of veins and arteries
|
Artery |
Vein |
|
Thicker, muscular wall |
Thinner wass |
|
Rounder lumen, smaller than that of paired vein |
Lumen larger and squashed |
|
Prominent internal elastic |
Ill-defined lamina |
|
Media > adventitia |
Adventitia>media |
|
No valves |
Valves |
II. Lymphatic Vascular System
A. Function
§ Collection from tissue spaces of fluid which originated from blood vascular system, for return to system
§ Transport of leukocytes from lymphoid tissues to blood vascular system
§ One way…back to heart
B. Structure
§ Lymphatic capillaries-single layer of endothelium forming blind ended vesses, no fenestrae, no zonual occludens, little/no basal lamina
§ Larger lymphatics- formed by convergence of lymphatic capillaries, thin vein-like walls, no clear layered tunic structure, smooth muscle aids in lymph flow toward heart, valves more numerous than veins
§ Lymph nodes- interposed between distal lymphatics and heart
§ Unidirectional flow of lymph towards hear, entering vena cava via thoracic duct and right lymphatic duct. Large ducts have longitudinal and circular smooth muscle bundles in media
§ Lymphocytes reach lymphiod tissue via blood vascular system, exiting via high endothelial venules
C. Identification
§ Look for vessels with acidophilic contents and leuokocytes, no erythrocyts
§ Valves in lamina
§ Near lymph generating organs-villi of small intestine, lonsils, lmphnode
§ Where lymphatics return to heart resemble large veins
III. Heart Histology
A. Anatomical review
§ Skin (epithelium)
§ Connective tissue
§ Parietal pericardium-mesotheium adherent to CT surrounding pericardial cavity
§ Pericardial space-contains pericardialflud
§ Visceral pericardium- mesothelium adherent to epicardium
§ Epicardium-fibrous and adipose CT forming adventitia of heart, with autonomic nerves and vasa vasorum present (tunica media)
§ Myocardium-composed of bundles of cardiac muscle of variable thickness, with strands of vascular CT intermingled (tunica adventitia)
§ Endocardium- subendothial CT layer (collagen fibers, elastic tissue, smooth muscle) of variable thickness (thicker in atria) underlying simple sqamous endothelial lining (tunica intima) branches of purkinje fibers occur in subendocardial layer
B. Places in the Heart
§ Fibrous skeleton- Dense collagenous and elastci CT supporting heart
§ Four Valves
Tricuspid, mitral valves- folds of endocardium covered by endothelium, and a central vascular fibrous CT plate, with scatted smooth muscle bundles extending into endocardial layer on atrial side
Semilunar valves of pulmonary artery and aorta-thinner than AV valves, lacking smooth muscle, blood vessels, lymphatics
§ Impulse-generating and conducting system
SA node located in superior right atrium, inferior to superior vena cava
AV node-point of origin of AV bundle of HIS, located in inferior right atrium adjacent to coronary sinus
AV bundle of His
Located at apex of muscular interventricular septum
Connected with AV node across the fibrous skeleton which separates the atria and ventricles
Composed of purkinje cells, specialized cardiac muscle ells for rapid electrical impulse conduction to ventricular cardiac m.
Prukinje cell-reduced number of myofibrils; paler cytoplasm; clear area forms halo around nuclei, twice diameter of ordinary cardiac m., maybe binucleate
Hundle of His gives rise to right and left ant and post bundle branches, that extend inferiorly in right and left endocardial regions of interventricular septum and extends into subendocaridal CT to ventricles, where purkinje cells communicate via gap junctions with ventricular cardiac muscle cells.
Tags: adreal, azygous, bradykinin, Cardiovascular Lymphatic Systems, cholestrol, enal, endocardium, Endothelium, external iliac veins, Fenestrated, hypertension, innominates, internal jugulars, lipoproteins, lymph nodes, Lymphocytes, media capillaries, mesenhcymal cells, myocardium, Myoendothelial, neuromotor terminations, norepinephrine, portal, prostaglandins, proteoglycans, Sinusoidal, splenic, superior mesenteric, thrombin, Venae cavae
