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28 Cards in this Set

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Circulatory System
blood filtrate: heart--> vessels--> capillaries (diffusion)

Components: heart, arterial system (from heart to tissues), capillaries, venous system (takes blood back to heart)

Size classification: macrovasculature (>0.1mm); microvasculature
Circuits of Circulatory System
Two circuits:
- pulmonary (from heart to lungs)
- systemic (from heart to body tissues)

* Portal system- connects two capillary beds
General features of blood vessels
3 layered walls:
1. tunica intima
2. tunica media (smooth muscle- thick in arteries, thin in veins)
3. tunica adventitia (collagen fibers run along the length- thick in veins, thin in arteries)

*Internal Elastic Lamina- underneath subendothelium (dark-staining structures)
Components of Intima
1. Endothelium
2. Basal Lamina
3. Subendothelium (smooth muscle associated; loose CT)
Vaso Vasorum
-collection of blood vessels running toward big blood vessels (ex: to the aorta)
Nervi Vascularis
collection of nerves
Three Size Classes of Arteries
1. Elastic (large)
2. Muscular (medium)
3. Small arteries and arterioles (which are even smaller)
Elastic (large) arteries
- Tunica Intima: multilayer- endothelial, subendothelial, internal elastic membrane (lamina)

- Tunica Media: thickest area (has elastin, smooth muscle; we get more layers as we get older. Not high diffusion rates, just transport)

- Tunica Adventitia- thin, collagen/elastic network; (vaso vasorum and nervi vascularis = innervate outer area)
Endothelium Activation (general endothelium)
Endothelium functions:
- selective barrier
- nonthrombogenic layer (prevents blood coagulation)
- regulation immune response
- hormone synthesis
Muscular Arteries
-Tunica Intima: variable (gets more thick as we get older)

- Tunica Media: thickest (smooth muscle (more muscular), little elastic)

- Tunica Adventitia: thick with external elastic lamina; vaso vasorum and nervi vascularis
Small Arteries and Arterioles
-Tunica Intima: about the same (endothelial and subendothelial lining; internal elastic lamina)

-Tunica Media: variable (small arteries can be 8 layers thick; arterioles can be 2 layers thick)

- Tunica Adventitia: thin and ill-defined (adventitia thinner to allow diffusion; don't need vaso vasorum, etc)
Precapillary Sphincters
- bands of smooth muscle around ends of arterioles that regulate flow into capillary bed (because they're delicate)
Capillaries
- site of exchange
- single squamous layer (so one cell layer thick) + basal lamina (basal lamina on outside)
- small diameter (could be smaller than diameter of a RBC)
Types of Capillaries
1. Continuous (somatic) capillaries
2. Fenestrated
3. Discontinuous (sinusoids) Capillaries
Pericytes
cells that lie on the outside of capillaries; maintain stability (involved in repair)
Continuous (somatic) Capillaries
- in muscle, lung, and CNS (not a really high gas exchange amount)
- thin cytoplasm associated; pores through basal lamina

- pericytes: cells that lie on outside of capillaries; maintain stability (involved in repair)
Fenestrated Capillaries
- found in sites of metabolic absorption (digestive tract, endocrine, kidney, gallbladder)
- basal lamina on outside- gaps present

- pinocytosis: thought to have created a pore completely through the cell. Allows larger things to pass thru capillary system.
Discontinuous (sinusoids) Capillaries
- found in liver
- gaps (holes) between cells and in basal lamina which allows even larger things to pass through
- highest level of diffusion
Functional aspects of capillaries
- function: regulate amount of fluid/pressure going through; vasodilators/vasoconstrictors
Subclasses of Veins
1. Small veins (venules)- postcapillary or muscular venules
2. Medium veins
3. Large veins

- all three tunicas present
- thinner-walled than arteries
Venules
*Postcapillary (where reabsorption takes place):
- basal lamina and pericytes
- no tunia media

* Muscular:
- < 1 mm diameter
- tunica media (2-3 layers)
Medium Veins
- Tunica intima: thin
- Tunica media: relatively thin
- Tunica adventitia: thickest (larger in veins; collagen and elastin associated)
Artery vs Vein
- artery: internal elastic lamina, large tunica media
- veins: smaller tunica media and larger tunica adventivia
Large Veins
-tunica intima: undefined
-tunica media: thin
-tunica adventitia: thickest, smooth muscle (collagen present as well)
Fibrons Skeleton
- made of dense CT; four rings that hold the four valves in place; also isolates atria from ventricles
Layers of Heart
* Endocardium:
- endothelium
- subendothelial layer

*Myocardium

*Epicardium (on outside):
- mesothelium
- subepicardium
Valves
*Fibrosa- dense CT core
*Spongiosa- loose CT
*Ventricularis- dense CT
Regulation of heart beat
- sinoatrial node (SA node)
- atrioventricular node (AV node)
- AV bundle (aka bundle of his)
- Purkinje fibers

SA node (top of right atrium)--> impulse stops (by fibrons skeleton) and AV node takes over--> impulse goes to bottom--> picked up by Purkinje fibers--> contraction