Blood vessels & circulation

The components that make up the cardiovascular system

The heart - A pump

Blood vessels - A conducting system

Blood - A fluid membrane

Tunica Inima

The inner layer of blood vessel walls

Contains an internal elastic membrane

Tunica Media

Smooth muscle in loose connective tissue

The thickest layer in the arteries

Contains an external elastic membrane

Tunica externa

Anchors the vessel to surrounding tissues

Vasa vasorum

The blood vessels of the blood vessels

How to classify arteries

Thicker walls and higher blood pressure

Collapsed arteries have small, round lumen

Arteries are elastic— will snap back into place

How to classify veins

Thinner walls and lower blood pressure

Collapsed veins have large, flat lumen

Veins have valves

Lumen

The inner, hollow part of blood vessles

Elastic artery

Arteries closest to the heart

Contains internal elastic layer

Thicker endothemium

ex. Aorta, pulmonary trunk

Muscular artery

Middle section of arteries

No internal elastic layer

ex. The majority of arteries throughout the body

Arteriole

Smallest, furthest artery

Does not have tunica externa

Contains basment membrane

Large vein

Largest vein

Closest to the heart

ex. pulmonary artery

Medium sized vein

Middle veins, middle sized

ex. the majority of veins in the body

Venule

Smallest ‘vein’, farthest from heart

Contains no tunica media nor tunica interna

Fenestrated capillary

Contains pores

Contains endothelial cells and basement membrane

Permits rapid exchange of water and large solutes

Fenetre - Window

Continuous capillary

Does not contain pores

Contains endothelial cells and basement membrane

Vasoconstriction

The contraction of arterial smooth muscle

Caused by the sympathetic nervous system

Vasodialation

The relaxation of the smooth muscle

Capillaries

The smallest blood vessels with thin walls to allow diffusion

No tunica externa nor tunica media

The diameter of capillaries is simmilar to RBCs

Capillary blood flow

Determind through pressure and resistance in the cardiovascular system

Under normal circumstances, blood flow through capillaries is equal to the caridac output

Flow (Q) = ΔP/R (Pressure Difference / Resistance)

Capillary hydrostatic pressure (CHP)

The pressure exerted by blood against the walls of capillaries

CHP can decrease from 35 to 18 along the length of the capillary

Vascular resistance

Driven by friction

Effected by vessel length and diameter

Blood viscosity

The resistance caused by interactions between the molecules suspended in the blood

Turbulence

Plaques can cause an increase in resistance

Venous pressure

The amount of blood arriving at the right atrium each minute

Influenced by muscular compression of peripheral veins and the respiratory pump

Tissue perfusion

Flow of blood through the tissues

affected by cardiac output, peripheral resistance and blood pressure

Autoregulation

causes immediate, localized adjustments

Neural mechanisms

Respond quickly to specific sites

Cardiac and vasomotor centers of the medulla and oblongata send stimuli to the cartoid aortic sinuses

Endocrine mechanisms

direct, long-term changes

Antidiuretic hormone (ADH) effect on cardiovascular system

Elevates BP

Reduces water loss at kidneys

Released with low blood volume, and high osmotic concentrations

Angiotensin II effect on cardiovsascular system

Responds to fall in renal BP

stimulates the production of other hormones

increases cardiac output

Erythopoietin (EPO)

Responds to low BP and low O2 sat

Natriuretic peptides (ANP and BNP)

Responds to excessive diastolic stretching

Lower BP and blood volume

Reduces stress on heart