A&PII Vessels & Hemodynamics

pulmonary circulation

heart ↔ lungs

• pick up oxygen and get rid of CO2

pulmonary circulation route

right ventricle → pulmonary arteries → lungs → pulmonary veins → left atrium

pulmonary arteries vs veins blood

arteries = deoxygenated

veins = oxygenated

systemic circulation

heart ↔ body

• delivers oxygenated blood to the body and brings deoxygenated blood back to the heart

systemic circulation route

left ventricle → aorta → body tissues → venae cavae → right atrium

arteries vs veins vs capillaries

Arteries = away from heart

vein = toward heart

capillaries = tiny vessels where exchange happens between blood and tissues

vasoconstriction

vessel gets narrower

less blood flow

vasodilation

vessel gets wider

more blood flow

lumen

hollow/open space inside the blood vessel where blood flows

tunics

layers of the vessel wall

tunica intima

innermost layer

• found in every blood vessel

• directly touches the blood

• in large veins, it can form valves

tunica media

middle layer

• contains smooth muscle

  • for vasoconstriction and vasodilation

• prominent in arteries

tunica externa

outermost layer

• connective tissue

• prominent in arteries and veins

why do arteries have thick walls

They receive blood directly from the heart under high pressure

arteries tunic layers

intima: thin

media: very thick

• need lots of smooth muscle to control blood vessel diameter

externa: thick

arterioles tunic layers

intima: small

media: very small amount of smooth muscle

• need to control blood flow into capillaries

externa: almost absent

why do veins have thinner walls/ smaller tunics and less elastic

veins carry blood back to the heart under much lower pressure

veins tunic layers

intima: thin

• large veins can have valves made from tunica intima

media: thin

externa: thick

• for support

venules tunic layers

intima: small

media: little to none

externa: almost absent

why do capillaries have tiny and thin tunic

because blood needs to exchange materials with tissues

capillaries tunic layers

intima only

• one super-thin layer of cells

arterial system starts with the

aorta and pulmonary trunk/arteries

pulmonary artery is the only artery that

carries deoxygenated blood

elastic arteries

• the largest arteries

• receive blood directly from ventricles, so they experience high pressure

• stretch when blood is pumped into them and recoil afterward

muscular arteries

• medium-sized arteries

• control where blood goes by changing their diameter

  • via vasoconstriction and vasodilation

arterioles

• tiny branches of arteries

• lead directly into capillaries

• their smooth muscle can constrict or dilate

  • control how much blood enters capillary beds

capillaries

• most common type of blood vessel

• 65,000 miles throughout the body

• where oxygen exchange occurs between blood and interstitial space

capillary’s role in thermoregulation when temp is high

bringing heat in RBCs closer to skins surface to

induce sweating

↑ Core temperature
→ more blood flow toward skin
→ heat reaches skin surface
→ sweating + heat loss

capillary’s role in thermoregulation when temp is low

shunts blood flow away from skin

↓ Core temperature
→ less blood flow toward skin
→ blood is shunted away from skin
→ less heat escapes

capillary network

• branching of capillaries following the arterioles

  • so blood can get close to lots of different cells

metarterioles

link between arterioles and the capillary network / connection between arterioles and venules

• help control blood flow through the capillary bed

precapillary sphincters

little rings of smooth muscle at the entrances to capillaries

• control whether blood enters individual capillaries

how do capillary sphincters control whether blood enters individual capillaries

when they open:

more blood flow into capillary = more exchange

when they close:

less blood

precapillary sphincters and exercise example

1) glutes need more oxygen

2) sphincters open

3) more blood flows through glute capillaries

4) more oxygen delivered

anastomosis

connection between two blood vessels

glomus

• specialized anastomoses

• direct connection between small arteries and veins

  • so blood can bypass the capillaries

where glomus vessels are most numerous

fingers, toes, palms, soles of feet

• these areas are important for controlling how much heat your body loses

glomus and role in thermoregulation

controls peripheral blood flow

when you’re cold:

• glomus close/constrict

• less blood reaches the skin surface

• less heat is lost

when you’re hot:

• glomus opens

• more blood reaches the skin

• more heat can escape

veins and blood

carry blood toward the heart

• deoxygenated blood

  • except pulmonary veins carry oxygenated blood

    • from the lungs back to the left atrium

venules and blood

basically a tiny vein / small vessels

• carries deoxygenated blood from capillaries to larger veins

Capillaries → venules → larger veins → heart

hepatic portal vein

vein carrying nutrient-rich, deoxygenated blood from digestive organs to the liver for processing

why does the liver need to process

1) after you eat, nutrients are absorbed into your blood from your digestive tract

2) liver needs to process and regulate those nutrients before they enter the general circulation

biotransformation

removes toxic substances by altering structure

Liver takes a substance → chemically changes it → makes it easier for the body to handle/remove

hepatic portal system

Capillaries → hepatic portal vein → liver → another capillary network

valves in veins

• >2mm in diameter

• prevent backflow of blood against gravity

  • blood has to travel from feet to heart

  • gravity is trying to pull the blood back down

  • so veins have one-way valves

aneurysm

weakened area of a blood vessel wall that bulges outward

aneurysm and location

can be lethal if it develops in a major artery, especially the aorta

• it can rupture

• the aorta carries blood under high pressure

ascending aorta

• comes directly out of the left ventricle

• branches into right and left coronary arteries

aortic arch

• supply blood to head + neck + upper limbs

branch into:

1) brachiocephalic trunk

2) left common carotid artery

3) left subclavian artery

brachiocephalic trunk splits into

1) right common carotid artery (right side of head/neck)

2) right subclavian artery (right upper limb)

descending aorta

• longest portion of the aorta

branches into:

1) thoracic aorta

• supplies structures in the thorax and through diaphragm

2) abdominal aorta

• supplies abdominal organs

head/neck arteries

1) brachiocephalic trunk

2) left common carotid

3) left subclavian

brachiocephalic trunk

• first branch off the aortic arch

branches into:

1) right common carotid

• supplies the right side of the head and neck

2) right subclavian

• supplies the right upper limb

left common carotid

• second branch off the aortic arch

• supplies left side of head and neck

left subclavian

• third branch off the aortic arch

• supplies left upper limb

upper limb arteries name/location

• arteries supplying your arm are one continuous artery

• the artery changes name depending on where it is

• No branching until the brachial

upper limb arteries pathway

1) Subclavian (beneath clavicle)

2) Axillary (armpit)

3) Brachial (arm) (divides at elbow)

4) Radial + Ulnar

radial vs ulnar

radial: thumb side

ulnar: pinky side

pelvis

descending aorta reaches the lower abdomen and splits into:

1) right common iliac

2) left common iliac

lower limb artery path

1) femoral (thigh)

2) popliteal (behind the knee)

3) tibial arteries

• anterior and posterior

pelvis + lower limb artery pathway

1) descending aorta

2) common iliac arteries

3) femoral artery

4) popliteal artery

5) anterior + posterior tibial arteries

systemic circulation veins

return trip, major veins that bring blood back to the heart

coronary sinus

collects deoxygenated blood from the heart muscle itself and returns it to the right atrium

superior vena cava

returns blood from region superior to sternal area / right atrium

brings blood back from areas above the diaphragm (head, neck, chest, upper limbs)

inferior vena cava

returns blood from region inferior to sternal area / right atrium

brings blood back from areas below the diaphragm (abdomen, pelvis, lower limbs)

head/neck veins

external and internal jugular veins

• return blood from head and cranial cavity

• drain into subclavian vein

internal jugular + __________ = ?

internal jugular merges with subclavian to form brachiocephalic vein

median cubital vein

vein in the front/inside of your elbow

• used for blood draws

great saphenous vein

• longest vein in the body

• runs along the lower limb

great + small saphenous veins and surgery

• can be used as grafts during CABG and other surgeries

• a section of vein can be taken and used to create a new route for blood flow

major determinants of blood flow

1) pressure difference

2) resistance

pressure difference

blood flows from higher to lower pressure

• the greater the pressure difference, the greater the blood flow

resistance

anything that makes it harder for blood to flow through a vessel

more resistance = less flow

less resistance = more flow

• layer nearest to wall experiences greater resistance to flow compared to at the center of the vessel

• affected by viscosity

viscosity

measure of a liquid’s resistance to flow

• more viscosity = more pressure required to increase flow

laminar flow

smooth, organized blood flow

• moves along in smooth, concentric, parallel paths

turbulent flow

motion that is caused by vortex currents

• moves in nonparallel blood flow

• allows you to hear sounds when taking a blood pressure

when does turbulent flow occue

• when flow is a higher velocity (during exercise or hypertension)

• when fluid passes a constriction (blood pressure)

• sharp turns

• rough surface

blood pressure

force blood exerts against wall of blood vessel

aka blood pushing outward against the inside of the artery

Korotkoff sounds

the sounds you hear through the stethoscope while measuring blood pressure with a cuff

• the cuff temporarily compresses the artery

• as pressure releases, blood starts moving through the artery again

• the blow flow becomes turbulent

  • creates vibrations/sounds called Korotkoff sounds

korotkoff sounds tell you

first sound: systolic BP

• pressure when the first sound appears

last sound: diastolic BP

• when the sounds disappear

vascular compliance

tendency for blood vessel volume to increase as BP increase

• how easily a blood vessel can stretch and hold more blood

vascular compliance + BP

highly compliant: can take in a lot of extra blood without a huge increase in pressure

veins vs arteries compliance

veins are more compliant

veins

• have thinner tunics

• less muscular walls

• they can stretch and hold more blood

arteries

• less stretchable

• pressure rises more when blood enters

pulse

pressure wave produced as blood is ejected from left ventricle then spreads throughout arteries

pulse route

1) left ventricle contracts

2) blood enters aorta

3) aorta’s wall stretches

4) that pressure wave travels through the arteries

pulse pressure

difference between systolic and diastolic pressures

example: 120/80, pulse pressure = 40 mmHg

preload is determined by

volume of blood that enters heart from veins

cardiac output and preload

more volume of blood = more return from veins to heart = increase Q

volume loss = less return from veins = decrease Q

venous tone

partial contraction of veins caused by sympathetic nervous system stimulation

venous tone increase/decrease

↑ SNS stimulation → ↑ venous constriction → ↑ venous tone

↓ SNS stimulation → ↓ venous constriction → ↓ venous tone

gravity affects which vessels more

vessels below the heart

• gravity pulls blood downward

• blood can pool in the legs/feet

• can cause edema/swelling

orthostatic reflex

blood pooling in legs when going from sitting to standing

orthostatic reflex process

1) baroreceptors detect BP is low

2) blood vessels vasoconstrict

• raise BP

• increase venous return

• increase HR/ contractility

helps bring BP back up

orthostatic hypotension

body having a delayed response

• person will eventually pass out

local control

periodic relaxation and contraction of precapillary sphincters

• regulate blood flow through capillary networks in tissue

relax = open = more blood enters capillaries

contract = close = less blood enters capillaries1

local control and active tissues

when muscle acitivty is increased:

• muscles use more O2

• produces more CO2 + wastes

• precapillary sphincters relax

• increased blood flow to that tissue

need more blood for oxygen and removal of waste

long-term blood flow

occurs when a tissue needs extra blood for a long time

1) the tissue needs more blood flow, more oxygen

2) the body grows more blood vessels/capillaries in that tissue

3) more blood can reach the tissue

angiogenesis

growth of new blood vessels

nervous control of blood flow in tissue

responsible for overall blood flow to tissues

regulated by vasomotor center in brain

hormonal control of blood flow in tissues

norepi/epi binds to vascular smooth muscle causing vasoconstriction