Transcript Major Concepts of Anatomy and Physiology

The Circulatory
System – The Blood
Vessels
Part 4: Regulation &
Maintenance
Blood Vessels

Blood Vessels: Function as highways for the
transportation system of the body.
 Transports
blood as it is propelled by the beating of
the heart.
 7% of blood volume found in the heart, 7% in the
pulmonary system, 13% in the arteries, and 65% in
the veins.

Types of Blood Vessels:
 Arteries
 Arterioles
 Capillaries
 Venules
 Veins
Blood Vessel Anatomy

Tunics: The three layers that make up the walls of
arteries & veins

Tunica Adventitia: Outer layer composed of loose connective
tissue – keeps the vessels in place.
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
Tunica Media: Middle layer composed of smooth muscles.
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Vasa Vasorum: Supplies nutrients to the larger arteries & veins.
Vasoconstriction: Contraction of this layer that narrows the blood
vessel.
Vasodilation: Relaxation of this layer that widens the blood vessel.
Tunica Interna: Inner layer composed of smooth endothelium –
allows blood to pass through easily without catching on the
walls.
Lumen: The hollow center of the blood vessel through
which blood flows.
Arteries & Arterioles

Arteries: Blood vessels responsible for carrying
blood away from the heart – very strong to
withstand the pressure surges!
 Elastic
Arteries aka Conducting Arteries: The
largest diameter arteries, such as the aorta, that
propel the blood through the vessels & provide a
pressure reservoir to keep the blood flowing.
 Muscular Arteries aka Distributing Arteries:
Contain more smooth muscle & help to control blood
flow – carry blood to all parts of the body.

Arterioles: The smallest blood vessels that
regulate blood flow into capillaries.
 Resistance:
The regulation arterioles uses in
opposition to blood flow to control total blood volume.
Capillaries

Capillaries: The smallest vessels in the body consisting
of a single layer of endothelium.
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Found almost everywhere in the body, but not in tendons,
ligaments, or the cornea & lens of the eye.
Three Types of Capillaries:

Continuous Capillaries: Continuous tubes formed of
endothelial cells – intracellular cleft present for some materials to
pass through.
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
Fenestrated Capillaries: Fenestrations (holes) along the wall to
allow for quicker passage of materials.


Found in most connective tissue, smooth muscle, lungs, & skeleton.
Found in organs that use rapid filtration - small intestine, endocrine
glands, kidneys.
Sinusoids: Large fenestrations (holes) and large intracellular
lefts to allow for easiest passage of materials.
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Found in liver, spleen, some glands, red bone marrow.
Capillary Beds
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Capillary Beds: Organized “tangles” of capillaries that
exchanges materials into body tissue – connect
arterioles & venules.
Thoroughfare Channels: Bypasses the capillaries to
carry blood directly from the arterioles to the venules.
Precapillary Sphincter: The ring of smooth muscle
regulating blood flow into the capillaries.
Vasomotion: The intermittent flow of blood through
capillaries.
Portal Systems: Two separate capillary beds in which
blood flows through before heading toward the heart.
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Portal Vein: Transports blood between the two capillary beds.
Found in kidneys, between the intestines & the liver, between the
hypothalamus & pituitary glands.
Capillary Exchange

Capillary Exchange: The movement of
substances between the blood and interstitial
fluid of the tissue. Mainly exchanges..
 Oxygen
 Carbon
Dioxide
 Glucose
 Amino Acids
 Hormones

Diffusion: The basic rule states that the more
surface area there is for exchange, the faster the
gases and nutrients will transfer into the tissue.
Capillary Exchance

Transcytosis: Materials are enclose in vesicles
to be transported across the cell.
 Typically
used by large molecules, such as insulin,
albumin, & some proteins & fatty acids.
 A form of pinocytosis (where small molecules are
brought across cell walls in small vesicles).

Bulk Flow: The process of a large amount of
materials moving in the same direction.
 Their
movement can’t be accounted for by diffusion.
 Movement is driven by pressure mechanisms.
Capillary Exchange
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Filtration: The movement of materials from
capillaries into the interstitial fluid,.
Reabsorption: The movement of materials from
the interstitial fluid into the capillaries.
Edema: The increase in interstitial fluid volume
caused by filtration rate exceeding reabsorption
rate which results in bloated tissue! Can be
caused…
 Increased
capillary blood pressure
 Increased permeability of the capillaries
 Decreased concentrations of the plasma proteins
Veins & Venules

Veins: Vessels responsible for carrying blood
back toward the heart.
 Store
approximately 65% of the blood volume at any
time – 13% in arteries, 7% in the heart.
 Made up of the same tissue layers as the arteries, but
with less smooth muscle and fewer elastic fibers.
 Blood pressure is lower than in the arteries.
 Internal valves prevent backflow of blood.

Venous Sinuses: Veins with no smooth
muscles and very large lumens found in the
heart and brain.
Venous Return
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Venous Return: The flow of blood back into the heart,
controlled by valves within the veins.
5 Influencing Factors on Venus Return:
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Pressure Gradient: Blood flows from higher pressure (arteries)
to lower pressure (veins).
Respiratory Pump: Breathing muscles help to compress and
decompress veins.
Chordae Tendinae: Tendonlike fibrous cords that connect the
atrioventricular valves of the heart via papillary muscles &
provides suction within the heart.
Gravity: Helps return blood from the higher areas of the body.
Skeletal Muscle Pump: Contraction of the skeletal muscles
contract to push on the veins, causing the blood to flow toward
the heart.
Hemodynamics
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Hemodynamics: The regulation of blood flow
via pressure & resistance.
Blood Flow: The volume of blood that flows
through a given tissue during a given amount of
time, measured in milliliters per minute (mL/min).
 “In
general, blood flows from areas of high pressure
to areas of low pressure.”

Blood Distribution throughout the body is
dependent on pressure differences and
resistance to blood flow within the vessels.
 Distribution/Flow
determines the amounts of nutrients
& oxygen being delivered to the tissue.
 Inadequate blood flow can cause all kinds of trouble!
Blood Pressure
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Blood Pressure: The measure of pressure
inside the main arteries during systole and
diastole.
Pulse Pressure: The difference between
systolic & diastolic pressure.
 Can
be used to measure the stress on the arteries
caused by the contractions of the heart.

Mean Arterial Pressure (MAP): The average
blood pressure in the arteries.
 Measured
as the 1/3 point between diastolic &
systolic pressure.
Blood Pressure
Hypertension: Chronically high resting
blood pressure that can weaken arteries &
cause aneurysms.
 Hypotension: Chronically low resting
blood pressure that can be due to anemia,
dehydration, or blood loss.
 Typical Blood Pressure for a healthy,
resting adult human is approximately
120/80 mmHg (systolic/diastolic).
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Vascular Resistance
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Vascular Resistance: The opposition to normal blood flow within
the vessels that slows the movement of the blood down.
Three factors that affect Vascular Resistance:

Diameter of the Vessels: The size of the lumen can be controlled by
vasoconstriction & vasodilation to control blood flow.
 Length of Vessels: The longer the blood vessel, the greater the
resistance provided.
 Viscosity: The thicker the blood, the greater the resistance to blood
flow & the higher the blood pressure must be to move the blood.
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Viscosity is mainly due to the ratio of red blood cells to plasma, with some
effect from proteins.
Systemic Vascular Resistance (SVR): The measure of the total
resistance offered by all of the systemic blood vessels.
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The smaller the vessel, the more it contributes to the SVR total.
Blood Flow Control
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Autoregulation: The means by which
tissue naturally regulate their own blood
flow in response to metabolic demand.
Blood Flow Control
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Neural Control: The nervous system controls blood flow
& pressure through the cardiovascular center (CV
center) of the medulla oblongata. Controls heart rate,
stroke volume, and blood flow in specific organs.
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Cardiac Accelerator Nerves: Delivers sympathetic control to
speed up heart rate.
Vagus Nerve: Delivers parasympathetic control to slow down
heart rate.
Baroreceptors: Pressure-sensitive receptors in the arteries that
signal the CV center to control the carotid sinus reflex and the
aortic reflex – also regulates the baroreflexes.
Chemoreceptors: Sensors in the aorta and the carotid sinus of
the brain that detect changes in blood oxygen, carbon dioxide
and hydrogen levels – also regulates the chemoreceptor
reflexes.
Blood Flow Control
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Hormonal Control: Several hormones regulate
blood pressure & blood flow!
 Angiotensin
II: Increases vasoconstriction to raise
blood pressure.
 Norepinephrine & Epinephrine: Increases
vasoconstriction & heart rate to increase blood
pressure.
 Artial Natriuretic Factor: Increases vasodilation to
decrease blood pressure.
 Nitric Oxide: Increases vasodilation to decrease
blood pressure.
 Aldosterone & ADh: Increase the amount of blood to
increase blood pressure.
Circulatory Shock
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Circulatory Shock: Occurs when the cardiovascular system fails to
deliver adequate supplies of oxygen & nutrients to the cells via
inadequate blood flow. 4 types!

Cardiogenic Shock: Due to the heart failing to pump adequately,
typically due to heart attack.
 Hypovolemic Shock: Due to hemorrhage (sudden loss of blood), loss
of fluid or inadequate fluid intake (dehydration).
 Vascular Shock: Due to excessive pooling of the blood in the limbs,
which can be caused by brain injury, excessive time spent standing,
allergic reactions (anaphylaxis).
 Obstructed Shock: Due to the path of venous return being blocked,
typically by an embolism (blood clot).
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Response to Shock: The body attempts to return to homeostasis
via hormones, local vasodilators, and sympathetic and autonomic
nervous system activation.
Signs of Shock: Low systolic blood pressure; weak & rapid pulse;
cool, pale, clammy skin; altered mental state; nausea; thirst; low
blood pH.
Pulse Rates – Good to Know!
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Pulse: The traveling wave of pressure created
by the expansion & recoiling of large arteries
after each ventricular systole.
 The
closer the arteries to the heart the stronger the
pulse.
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Pulse Rate: The speed at which the pulse
occurs.
Arterial Pressure Points: Brachial artery,
common carotid artery, facial artery, femoral
artery, popliteal artery, & radial artery are good
places to look for pulse rates!
Major Circulatory Routes
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The ones you need to know:
 Systemic Arteries
 Systemic
Veins
 Hepatic Portal System
 Pulmonary Circulation
 Fetal Circulation

The rest tend to follow the names of the
bones – 2-in-1 for studying!
The Systemic Arteries
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Systemic Circuit: Supplies the cells all
over the body with nutrients & oxygen
while removing metabolic wastes.
The Systemic Arteries
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Ascending Aorta: The biggest blood
vessel starting out the systemic circuit –
leaves the left ventricle of the heart &
extends to the arch of the aorta.
 Right
& Left Coronary Arteries: First
branches of the ascending aorta that supply
the heart muscle with blood.
The Systemic Arteries
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Aortic Arch: Follows the coronary arteries
& has three branches…
 Brachiocephalic
Trunk: Splits into the…
Right Common Carotid Artery to supply the right
side of the head & neck
 Right Subclavian Artery to supply the right upper
limb
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 Left
Common Carotid Artery: Supplies the
left side of the head & neck
 Left Subclavian Artery: Supplies the left
upper limb
The Systemic Arteries
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Descending Aorta: The portion of the aorta after the
arch that descends through the chest and abdomen
before branching into the external and internal iliac
arteries that supply the legs.

Thoracic Aorta: The name of the descending aorta when
serving the organs of the chest. Branches…
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Bronchial arteries that serve the bronchi of the lungs
Arteries serving the pericardium, esophagus, chest muscles, &
diaphragms.
Abdominal Aorta: The portion of the descending aorta that
serves the organs of the abdomen.
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Celiac Trunk: Splits into..
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The common hepatic artery (serving the liver)
The left gastric artery (serving the stomach)
The splenic artery (serving the stomach, pancreas, & spleen)
Also serves the kidneys, gonads, colon, rectum, small intestine, and
pancreas.
The Systemic Arteries
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Right & Left Carotid Arteries: Serve the
head & neck.
 Split
into the internal and external cerebral
arteries, the facial arteries, & the basilar
artery.
The Systemic Arteries
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Upper Limb Arteries:
 Subclavian:
The artery that serves the upper
limbs.
 Subclavian  axillary  brachial  radial &
ulnar  palmer arches  palmer digitals &
metacarpal.
The Systemic Arteries
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Abdominal Arteries:
 Renal
Arteries: Supply the kidneys.
 Gonadal Arteries: Supply the ovaries &
testes.
 Superior & Inferior Mesenteric Arteries:
Split into multiple branches to supply the
pancreas & small & large intestines.
The Systemic Arteries
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Lower Limb Arteries: All begin with the
Common Iliac Arteries, which divide into
the internal & external common iliac.
iliac  femoral  popliteal 
anterior & posterior tibial  fibular  dorsal &
plantar of the foot  metatarsal & digital
 External
The Systemic Veins
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Systemic Veins: The veins that bring the
blood back to the heart!
 Superficial
Veins: Found just underneath the
skin & anastomose (join end to end,
constantly with each other & other deep
veins) – do not run parallel with arteries.
 Deep Veins: Run parallel to arteries of the
same name & usually drain the structure the
artery supplies.
The Systemic Veins
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3 Veins responsible for returning blood to
the heart:
 Coronary
Sinus: The main vein of the heart
that receives all the blood from the
myocardium. 3 veins drain directly into it.
 Superior Vena Cava: SVC drains the veins
from the head, neck, chest, & upper limbs
directly into the right atrium.
 Inferior Vena Cava: IVC is the largest vein –
drains the veins from the abdomen, pelvis,
and lower limbs into the right atrium.
The Systemic Veins
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Some Important Veins:
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Internal & External Jugular Veins: Drain from the sinus veins
in the head – internal serves the brain, external serves the
structures outside the cranium.
Right & Left Brachiocephalic Veins: Formed by the subclavian
& jugular veins uniting on each side & empties directly into the
superior vena cava.
Axygos System: Collects blood from the thorax & abdominal
wall – can bypass the inferior vena cava & empty into the
superior vena cava if the IVC is obstructed.
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Azygos Vein, Hemiazygos Vein, & accessory veins important
here.
Great Saphenous Veins: Superficial veins that are the longest
in the body – travel from the foot to the groin – most likely to
suffer from varicosities due to length & number of valves.
The Hepatic Portal System
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Portal Vein: Any vein that transports blood from one
network of capillaries to another rather than to anther
vein or the heart.
Hepatic Portal Vein: Takes blood from the capillaries of
the organs of the digestive system and transports it to
the sinusoids of the liver.
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Formed by the joining of the splenic vein and superior
mesenteric vein.
Hepatic Portal System: Absorbs blood directly from the
digestive tract and transports it to the liver to convert
some of the rich nutrients into other substances to be
used or stored & detoxifies other substances.

Blood in this system is high in nutrients & low in oxygen content.
Pulmonary Circulation
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Pulmonary Circulation: Takes deoxygenated blood
from the right ventricle, oxygenates it, and returns it to
the left atrium.
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Deoxygenated blood enters the right atrium
Blood flows from the right atrium into the right ventricle & is
forced out into the pulmonary arteries.
Blood travels from the pulmonary arteries to the right & left lungs
& through the capillaries of the alveoli.
Blood drops the carbon dioxide & uptakes oxygen before
heading back to the pulmonary venules and to the right & left
pulmonary veins (the ONLY veins that carry oxygenated blood).
Pulmonary veins then empty into the left atrium where the blood
flows into the left ventricle and out to the body!
Fetal Circulation

Fetal Circulation: The circulatory system of the
fetus.
 Fetus
obtains oxygen & nutrients & elminates carbon
dioxide & other wastes through the umbilical cord &
placenta.
 Wastes travel from the intervillous spaces in the
placenta to the uterine veins to be filtered out by the
mother’s cardiovascular system.
 Nutrients travel from the maternal blood vessels 
intervillous spaces of the placenta  fetal
capiullaries.

Fetal & maternal blood typically do not mix – all
exchanges occur through capillary wall diffusion.