chapter 18: blood vessels

vasculature

also known as blood vessels

"distribution system"

~ carry oxygenated blood away from heart to tissues

capillaries

"exchange system"

~ form capillary beds

~ location of gas exchange

veins

"collection system"

~ drain deoxygenated blood from capillary beds to return to heart

blood vessels are composed of…

1.) lumen

2.) tunica intima

3.) tunica media

4.) tunica externa

lumen

central space of the blood vessels; blood flows through the center

tunica intima

~ innermost layer of the blood vessel wall

~ composed of endothelium; provides space for blood to provide a smooth passage

~ thin layer of unteral elastic lamina (subendothelium) give ability to recoil and stretch

tunica media

~ middle layer of the blood vessel wall

~ composed of smooth muscle cells

~ layer of elastic fibers → external elastic laminate

~ control diameter of blood vessel

~ vasomotor neuron

vasomotor neuron

stimulates extension and contraction of nerves

~ sympathetic nervous system; vasoconstriction (squeeze/contract) and vasodilation (gets bigger/relaxation)

tunica externa

~ outermost layer of the blood vessel wall

~ composed of dense irregular collagenous connective tissue; makes layer strong and prevents from stretching too much

~ prevent rupture of the vessels

~ vaso vasora

vaso vasora

tiny vessels going to the outermost vessels

~ since it is too far from center, it is difficult for diffusion to send oxygen and nutrient

elastic arteries

also known as conducting arteries

~ largest in diameter characterized by extensive elastic laminae

~ DOES NOT change in diameter in response to vasomotor nerves

(ex: aorta and immediate branches)

muscular arteries

also known as distributing arteries

~ intermediate diameter

~ characterized by well developed tunica media with many layers of smooth muscle

~ DOES change in diameter in response to vasomotor nerves

(ex: vasoconstriction and vasodilation)

arterioles

~ smallest arteries

~ metarterioles

~ precapillary

*** VASOCONSTRICTION AND VASODILATION AND PRECAPILLARY SPHINCTERS HAVE A HIGE IMPACT ON BLOOD FLOW TO TISSUES ***

metarterioles

connect to papillary beds and arterioles

~ smallest of arterioles; feed capillary beds of most tissues

precapillary sphincters

confine smooth muscle cells; contract to capillary bed

the artery is structured by…

1.) elastic arteries

2.) muscular arteries

3.) arterioles

atherosclerosis

characterized by buildup of plaque within tunica intimate

~ tend to from in areas where blood flow changes direction

if plaque exposed to blood, clots may form and back flow to an area…

could cause myocardial infarction or stroke

artery function

1.) blood flow

2.) monitoring blood pressure

3.) monitoring chemical concentration of blood

baroreceptors

pressure receptors; monitor and find unwanted changes

~ aorta and carotid artery

chemoreceptors

chemical receptors; aid in stabilizing; detect blood, oxygen, carbon dioxide, hydrogen ion concentration

~ aorta

veins general structure

~ venous arteries

~ extension of tunica intimia

~ thinner walls, fewer elastic fibers, less smooth muscle, larger lumens than arteries

veins outnumber arteries

venules

smallest veins

~ consists of postcapillary arteries

smallest vein

drains blood from capillary beds

postcapillary arteries

composed of only endothelium and connective tissue tunica intima; easily exchange of material with interstitial fluid

venous arteries

extension of tunica intima; overlap to prevent back flow of blood

~ typically found in legs; where gravity opposes blood to return to heart

~ present in many veins

the three types vascular anastomoses are…

1.) arterial anastomoses

2.) venous anastomoses

3.) arteriovenous anastomoses

arterial anastomoses

found in heart, brain, and surround joints

~ oxygen DEPRIVED tissue releases chemicals agents that induce angiogenesis

venous anastomoses

MOST COMMON TYPES of anastomoses in body

~ connects neighboring veins and creates web-like patterns under the skin

arteriovenous anastomoses

enable artery to empty directly into a vein without a capillary bed

~ found in skill + fetal circulation

hemodynamics

physiology of blood flow

blood pressure (BP)

outward force that the blood exerts on the walls of the blood vessels

~ BP highest in systemic arteries

~ BP lowest in systemic veins

blood flow

volume of the blood that flows through a vessel per minute

pressure gradient effects on blood flow…

directly proportional

resistance gradient effects on blood flow…

inversely proportional; working in opposition of blood flow

velocity

flow determined by the cross-sectional area of vessel

~ flow fastest in large arteries; slow flow in capillary (since there are many of them)

resistance

also known as peripheral peripheral resistance; direct relationship with BLOOD PRESSURE

anything that hinders with the blood flow through the vasculature

~ most resistance occurs in vasculature away from the heart

factors in which influence blood pressure…

1.) blood vessel radius

2.) blood viscosity

3.) blood vessel length

4.) obstruction in vessels

blood vessel radius

increase in blood vessel size → lower resistance

blood viscosity

more viscosity (thickness) → more resistance

blood vessel length

more length → more pressure → more resistance

obstruction in vessel

build-up of plaque → blood clots → blockage → more force → more resistance

cardiac output

cardiac output and peripheral resistance determines pressure gradient that drives circulation

~ directly proportional