Week 1 - Study Guide Flashcards
Cardiovascular System
Structures of the blood vessels -
Name the three Tissue Layers
- Tunic Intima
- Tunic Media
- Tunic Externa
Composition & Function of:
Tunic Intima
Structure:
Simple Squamous
Function:
1. Tissue release NITRIC OXIDE
2. to control the diameter
Composition & Function of:
Tunic Media
Structure:
1. Smooth muscle
2. Elastic
3. Collage
Function:
1. Vasoconstriction & Vasodilation
Important for directing blood
Composition & Function of:
Tunic Externa
Structure:
1. Loose Connective Tissue
Function:
1. Strength and Rigidity (stability)
Holds everything in
Name the 3 tissue layers of the blood vessels:
Outer
middle
internal
Outer Layer = Tunica Externa
Middle Layer = Tunica Media
Internal Layer == Tunica Intima
Valves present in
Veins
Sphincters present in
Arterioles, capillaries
Three types of Arteries
- Elastic (conducting arteries)
- Muscular (distributing) Arteries
- Resistance Arteries (Arterioles)
Elastic is located where and an example:
closest to the heart
Aorta
Another name for elastic arteries
Conducting arteries
Structure & Function of
Elastic (conducting) arteries
Changes in systole & diastole to accommodate pressure changes
Large diameter = low resistance
When the blood pressure spikes during systole, the elastic nature of these arteries expands.
Structure & Function of
Muscular (distributing) arteries
Most names arteries
Distributes blood to specific regions - controls blood flow to specific regions according to body needs
EX –> deliver blood to kidney - renal vein
Controls blood flow to organs
Major component is the muscle itself
Exaggerated tunic media - because it is a muscular artery, the key element is the amount of smooth muscle.
- Has the most smooth muscle and the least of endothelium tissue
Muscular has the most smooth muscle
followed by Elastic in the middle, and Arteriole having the least smooth muscle.
Structure & Function of
Resistance Arteries
Resistance arteries help regulate blood pressure from the arterioles.
Resistance arteries are small with smooth muscle. Small, sphincter, smooth muscles
Connection point from the arteries to the capillaries and specifically regulate blood flow to the capillaries
Provides the highest degree of control via sphincters (constriction & dilation)
Structure & Function of
Arterioles - part of the Resistance
Resistance vessels that regulate blood flow to capillaries, neural, hormonal, & local control via chemicals.
Functionality - hormone, ANS, local chemicals, sphincters
Capillaries are all about….
Exchange
Where don’t we find capillaries?
- Cartilage
- Epithelial (poor) blood is in CT
- Cornea & lens
Structure & Function of
Metarteriole vs Thoroughfare channels
Leading to a capillary bed.
10-100 capillaries off of one metarteriole,
exchange at the capillary bed
Vary in size by how many branches off the main capillary and is the major entry into a capillary bed.
1-cell thick tunica intima - capillaries are very thin and facilitates exchange of resources
Sphincters in the arterioles can control blood leaving the metarteriole into the capillary bed through the sphincters
Just because blood enters the metarteriole DOES NOT mean it enters the individual capillary beds.
Because we have sphincters, if blood is limited and cannot enter the capillary bed, because the sphincter is closed, the blood will continue through the metarteriole into the thoroughfare channel. - A shortcut that bypasses the capillary bed
Features of the capillaries
Interconnection between the arterioles and the thoroughfare channels.
Metarterioles and Thoroughfare channels are details of how the system works
Metarteriole vs Thoroughfare channels
Generally, both take blood from arteriole venule
Meta can bypass capillary via sphincters
Thoroughfare channels shunt blood to the venule
Metarterioles have sphincters directing
Thoroughfare channels have NO sphincters - wants to push out - always open
Three types of capillaries
- continuous
- Fenestrated
- Sinusoidal
Order the capillaries from least leaky to most leaky
least leaky - Continuous
midrange leaky - Fenestrated
Most leaky - Sinusoidal
Where are continuous capillaries found?
Found in skin & muscle
Most common because they are all over the body
Continuous capillaries are less leaky because they only have small openings in between endothelial cells.
This is important because has control over how many substances (how large) enter or leave the blood vessel structure
Not found in the CNS because we have the Blood-Brain Barrier. which has its own due to astrocytes.
What is Fenestrated also known as?
Windows
Where are Fenestrated capillaries found?
Pores –> absorption or filtration
Examples:
1. Small intestines - absorption of nutrients
2. Kidneys - filtering solutes and fluids out of bloodstream into urine
3. Endocrine Organs - Facilitates movement of hormones
Midrange leaky - Not thee leakiest but pretty leaky - hence why they are called windowed.
They have Pores that facilitate 2 major processes:
1. Absorption - like in digestion
2. Filtration - like in the kidneys
Where are the Sinusoidal capillaries found?
Liver, bone marrow, spleen, adrenal medulla. – filter and monitor for bacteria
Most leaky, which slow blood flow to modify contents.*
The blood flow wanders through all these openings.
Has TORTUROUS Blood Flow which loops in and out, weaves through these really leaky blood vessels
Not as organized as fenestrated
Bone Marrow - produces more blood cells & blood clotting platelet elements which are produced and then leave the bone marrow.
Liver - Producing, filtering, storage, removal. ALOT of WORK. Filters toxins, breaks down RBCs, Iron storage.
Spleen - lymphatic system - influences immunity - more blood
Adrenal Medulla - internal Adrenal Gland - produces own hormones
Differentiates Elastic arteries
deals with big changes in pressure (near heart) - example Aorta - conducting
Differentiates Muscular arteries
distributing flow to organs - most named vessel
Differentiates Resistance Arteries
Regulates blood flow to capillaries via sphincters (arterioles).
vasodilation
vasoconstriction
Differentiates Continuous capillaries
- Skin and muscle
- small open junctions for exchange
- least leaky
- most common and numerous
Differentiates Fenestrated capillaries
- leaky for absorption and filtration (kidneys, GI , & endocrine)
- Midrange leaky
- windowed
Differentiates Sinusoidal capillaries
- Most leaky
- liver, bone marrow, spleen, & adrenal medulla
Pressure =
exertion of force upon a surface by an object
Shape of the container is not the big factor
P= Force/Area
Meaning - lots of different blood vessels
Force exerted by a liquid depends on height and density of liquid not the containers shape
Pascal’s Law - Charlene’s version
Blood will push against the walls of the tube and at the bottom equally
Water is the main component and will push out equally (the same)
Taking blood pressure:
Cuff pressure = pressure in artery = pressure in column of Hg and we read the height.
Mercurey is the heavy substance needed
Capacitance Vessels
(Venules & Veins)
blood vessels that contain most of the blood and that can readily accommodate changes in the blood volume. They are generally considered to be veins.
Blood reservoir - contains ~65% of all blood volume. 2/3
Venules size is
midsized
- between arteries and veins
Venules cause a lot of….
Edema because they are highly leaky.
Fluids and solutes leak out into the tissues and lead to edema
Venules have the porosity associated with…
capillaries
Is there leakiness in veins?
No
Because they have thicker muscles, not as thick as arteries,
Have a little more muscle, tunic media, and the Tunic Externa is substantial
Capacitance vessels have…
(Venules & Veins)
Have a high capacity of blood volume compared to arteries and capillaries
Meaning - a lot of the blood supply can build up in the veins and venules.
Because they are very stretchy compared to other blood vessel types.
Info on Capacitance Vessels
(Veins & Venules)
- Capillary beds unite…then venules unite
- Porosity –> common origin of Edema
- Low pressure (big issue with veins and venules). Because of all that low blood pressure it needs another mechanism that facilitates blood return back to the heart (venous return.)
3a. Skeletal muscle, valves, & thoracic pump
- Blood reservoir – up to 65% of blood volume
Why do you NOT want excessive amounts of blood sticking around in the venules & veins?
Because it means that cardiac output will not be maintained very well
Thoracic Negative Pressure
- Breathing creates thoracic negative pressure.
When we breathe deeply –
1. Ribcage goes out
2. Diaphragm pushes down which creates low pressure in the thoracic cavity.
But - relatively high pressure in the abdomen.
Because of this pressure dynamic – High on abdomen; Low in the thoracic cavity –
The blood in the abdomen wants to push back towards the heart in the thoracic cavity
Are Veins stretchy
Yes, they are stretchy
Hydrostatic Pressure
Amount of fluid in a space - Blood Pressure
High blood pressure for prolonged periods of time can damage the venules or veins
Special Issues with veins
Problems
- Varicose Veins
- Pregnancy
- Hemmorhoids
Special Issues with veins
Problems:
Varicose veins
- Distended vessels & Incompetent valves. (so much stretching that when the valves try to shut the edges do not connect. Blood will pool in the extremities - expanding the vessels)
- Due to prolonged elevation in hydrostatic pressure (too much fluid - stays too long)
Usually caused by too much standing - lack of movement for long periods of time. Get moving - use that skeletal pump.
Special Issues with veins
Problems:
Pregnancy
Pressure on the abdominal wall.
When pregnant mother breathes - they are not getting the same balance of pressure due to the negative thoracic pressure,
- there is an abnormally high pressure on the abdominal veins
- so the blood returning to the abdomen does not go as easily
- increases the pressure in the legs
Edema - common in ankles (periphery)
swelling in legs common
Special Issues with veins
Problems:
Hemorrhoids
Distended vein in rectal region
Due to dietary issues that cause constipation
Drink water and eat fiber!!
Pressure formula
F = ∆ P/R
F = blood flow (amount per unit of time)
∆ = change
P = pressure
R = Resistance
F = amount per unit of time (ml/min)
∆P = difference in pressure between two points.
(Big change in pressure from artery to venule)
(Small pressure difference between venule to vein)
R = resistance (easily altered via vessel diameter)
Factor to work against to get the blood to flow
Major source of resistance in body is vessel diameter
As Blood vessels more dilated = lower resistance = easier to push blood through the vessels
*More restricted blood vessels are = resistance = harder to push blood flow through the vessels
Pressure does what?
Drives the blood flow
Perfusion
Related to blood flow
Instead of saying one blood vessel
you are looking at an entire VOLUME of tissue
Many blood vessels of that particular volume of tissue
How much blood is delivered to that tissue over time
Systolic & Diastolic Pressure
Pulse pressure = difference between systolic & diastolic pressure
Blood pressure: P=Force/Area
Mean Arterial BP
(MABP)
other ways of calculating pressure
= Diastolic pressure + 1/3 pulse pressure
Because BP varies by location
Importance:
Peripheral Resistance
Arterioles matter
Peripheral Resistance is important in understanding the dynamics of blood flow in the cardiovascular system.
Arterioles matter because they create the control where blood is sent throughout the body.
Sphincters give the ability to vasoconstrict and vasodilate.
Peripheral Resistance =
opposition to flow due to friction of vessels walls (3 mediating factors)
Factors influence, but do NOT control the resistance itself.
What are the three mediating factors of resistance?
- Viscosity
- Vessel Length
- Vessel Radius
factors of resistance
Viscosity
Viscosity- albumin & erythrocytes
- Blood has a degree of thickness
~is it fluid = well hydrated
~is it more viscous = dehydration - due to more molecules passing through the system (sugar, ketones, etc.) - Viscosity = Dynamic
DO NOT VARY QUICKLY
factors of resistance
Vessel length
Vessel Length - cumulative friction of travel - consider growth or weight change
Cannot control vessel length
It does influence overall resistance in how. much flow there is
Change of blood flow and pressure because of increased resistance. Blood pressure may go up.
Will need to lengthen to support body mass for weight gain or growth
DO NOT VARY QUICKLY
factors of resistance
Vessel Radius
Vessel Radius
CAN VARY QUICKLY moment by moment
Embarrassed - face reddens
HUGE – HAVE CONTROL
What aids the regulation of viscosity?
Albumin
Flow is proportional to
(a) = a is called alpha
the 4th power of the radius.
meaning - the focus is blood volume
As radius increases = blood flow increases even faster.
The fourth power makes the big change
What do the proteins Albumin & Eurothrocytes due regarding viscosity?
Proteins help to regulate blood volume and osmotic pressures allowing for the right balance of water to stay in blood vessels or the tissues
Resistance varies inversely with
with the fourth power of the radius
Diameter goes up - flow goes up
Resistance reduces flow
Resistance goes up, flow goes down
Poiseuille’s Law
F = ∆ P π r (4th power)
—————————
8 n L
Components
F = flow
∆ P = pressure gradient
π = pi
r (4th power) = vessel radius
n = viscosity
L = vessel length
8 = constant - will not change
Poiseuille’s Law
How to predict changes
Direct Proportionality
F = ∆ P π r (4th power)
—————————
8 n L
Blood Flow is proportional to pressure gradient & vessel radius –> everything is in the NUMERATOR
∆ P π r (4th power)
If these values go up they vary directly –
Meaning: (go in the same direction)
- if the values P or R go up
F goes up - If the values P or R go down
F goes down
F= Blood flow
Poiseuille’s Law
How to predict changes
Inverse
F = ∆ P π r (4th power)
—————————
8 n L
Blood flow is inversely proportional to vessel length & blood viscosity –> everything in the DENOMINATOR
Meaning: (go in opposite direction)
- if viscosity goes up: n up
blood flow decreases: F down
OR - If length goes up: L up
blood flow decreases: F down - if viscosity goes down: n down
blood flow increases: F up
OR - If length goes down: L down
blood flow increases: F up
F= Blood flow
Applying Poiseuille’s Law
Radius greater =
Radius smaller =
F = ∆ P π r (4th power)
—————————
8 n L
Radius greater = greatest flow
Radius smaller = greatest resistance
Biggest influence = resistance - radius
Artery changes resistance - dilate/constrict
Changing the resistance has what relationship on blood flow
Most dramatic effect
A 19% increase in radius will double the volume flowrate
What percent in radius increase will double the blood flow
A 19% increase in radius will double the volume flowrate
What percent of occlusion will halve the volume flow rate?
19% occlusion
Blood flow examples of Poiseuille’s Law - (describes smooth flow conditions)
- Small vessels are the dominant contributors to flow resistance
- Small amounts of arterial occlusion can have dramatic effects. (Is the largest factor of flow resistance.)
- Flow regulation is accomplished by vasodilation and vasoconstriction in the arterioles
Flow is DIRECTLY proportional to vessel diameter
Flow is DIRECTLY proportional to vessel diameter
Flow is INDIRECTLY proportional to blood viscosity
Flow is INDIRECTLY proportional to blood viscosity
Flow is INDIRECTLY proportional to the vessel length
Flow is INDIRECTLY proportional to the vessel length
Flow is DIRECTLY proportional to the pressure difference
Flow is DIRECTLY proportional to the pressure difference
Bigger gradient = big force
Small gradient = small force
What are the 3 control mechanisms that regulate peripheral resistance?
- Local - in response to blood chemical composition
- Neural
- Hormonal
Regulating peripheral resistance:
Local - in response to blood chemical composition
General Idea - Informational
Think homeostasis
-
Autoregulation -
Adjust flow to allow removal or accumulation of materials.
As normal metabolism occurs you will need to adjust the amount of blood flow to a given region to help remove the accumulation of CO2 & metabolic wastes. -
Local Hypoxia -
–> Metabolic products (CO2, lactic acid, adenosine change pH) inhibit smooth muscle (vasodilator products)
Tissues will monitor the levels of CO2 – (CO2 and O2 are in opposition)
If you have a lot of CO2 - means you do not have much O2 -
Endothelial cells & platelets produce chemicals …
(associated with damage to the tissue)
Vasodilators - nitric oxide & prostacyclin (prostaglandins)
Vasoconstrictors - endothelins, serotonin & thromboxane (clotting) -
Precapillary sphincters = only respond to local stimuli & vasoactive hormones
Help regulate blood flow -
sphincters associated with metarterioles - precapillary sphincter can close off blood supply so that the blood can be routed to the correct places instead of all over at once.
Local control can help with this
Regulating peripheral resistance:
List the FOUR LOCAL types:
- Autoregulation - adjusts the flow to allow for removal or accumulation of materials
- Local Hypoxia - Metabolic products inhibits smooth muscle (vasodilator products)
- Endothelial cells & platelets produce chemicals -
vasodilation - nitric oxide & prostacyclin
vasoconstrictors - thromboxane, endothelins, serotonin - Precapillary sphincters - only respond to local stimuli & vasoactive hormones
Neural
Baroreflex. – pressure
Reflex = if you vasodilate - it reduces blood pressure
GOAL - lower blood pressure
Stimulus: High Blood Pressure
Receptors: Carotid Arteries, Aorta
Control Center: Medulla Oblongata. vasomotor center - inhibitory) meaning if you are inhibiting vasomotor center action it will reduce the amount of muscular contraction. Smooth muscle in blood vessels are going to relax - inhibited- causing vasodilation
Effector: Arterioles & veins. - (Arterioles are a major influence on Resistance.)
Response: Vasodilation
Parasympathetic will cause heart to slow
(rest and digest)
Neural
Chemoreflex
Think chemical (nervous system steps in)
Remember - O2 & CO2 are in opposition of each other
Goal - increase cardiac output and vasodilation = more oxygen
Stimulus: Low pH or O2, high CO2.
(if O2 is low = pH is low)
(if O2 is high = pH is high)
Receptors: Carotid Arteries
Control Center: Medulla Oblongata
Effector: Heart, blood vessels, & more
Response: Increase Cardiac Output, vasoresponses (dilate or constrict)
Neural
Medullary Ischemic reflex
Low Blood Flow in the medulla
Cerebral Ischemic Response safeguards cerebral perfusion
Goal - Get blood to the brain
Stimulus: Low Cerebral Blood FLow
Receptors: Medulla Oblongata measures hypoxia (low O2) & hypercapnia (high CO2)
Control Center: Medulla oblongata vasomotor center (stimulatory). causing vasoconstriction in the extremities to save the brain
Effector:. Extremity blood vessels
Response: Intense vasoconstriction (to bring blood to the brain)
Sympathetic influences blood vessel diameter directly via the vasomotor center of the medulla oblongata.
Inputs from three Autonomic reflex circuits with vasomotor center of the medulla oblongata as the control center are:
- Baroflex
- Chemoreflex
- Medullary ischemic reflex
Hormonal
Renin –> Angiotensin –> Aldosterone
Stimulus: Low BP, BV, Na+, High K+
Receptors: Kidney
Control Center: Kidney
Effector: Kidney - NEPHRONS
Response: Na+/H2O retention, K+ secretion
Hormonal - produced by the heart
(ANP) Atrial Natriuretic Peptide (Factor)
causes a reduction of BP - vasodilation
ANP released by the heart - inhibits Aldosterone to keep aldosterone from increasing BV & BP (by less NA+ and H2O are being absorbed resulting in peeing more leading to reduction of BV & BP)
At the same time ANP stimulates vasomotor center so vasodilation occurs resulting in lower BP & BV)
Stimulus: heart being overworked
Receptors: Heart
Control Center: Heart
Effector: Kidney, Nephrons (don’t make more Renin which leads to Aldosterone)
Response: Reduces BP, BV, & Vasodilation
Hormonal
ADH
Solution to pollution is dilution
ADH produced by posterior pituitary
goes to kidneys
Only impacts WATER reabsorption (increases it)
Does not impact solutes
Pee less - BV, BP goes up
Stimulus: Dehydration - High solutes - Na+, Low BV, BP
Receptors: Hypothalamus
Control Center: Hypothalamus
Effector: Kidney, nephrons
Response: Water retention, increased BP, BV & vasoconstriction
High solutes gets peed out for a more balanced solute level
Hormonal
Epinephrine
Short-term stress causes release of epinephrine
Blood Pressure - coming from adrenal gland - sympathetic NS
Stimulus:. Short term stress
Receptors: Hypothalamus
Control Center: Hypothalamus, Adrenal Gland (releases epinephrine)
Effector: Heart, vessels
Response: Increased cardiac output & Vasoconstriction
Which neural reflexes lead to vasodilation VS vasoconstriction?
Baroreflex
Chemoreflex
Medullary Ischemic Reflex
Baroreflex - vasodilation
Chemoreflex - Both - Vasodilation in metabolic areas - Vasoconstrict to push to the core
Medullary Ischemic Reflex - vasoconstricts
If the heart pumped a drop of blood to the brain, which of the following vessels are NOT an option for a step in the pathway?
- Aorta
- Brachiocephalic artery
- Left subclavian artery
- Left common carotid
- Right common carotid
- Right external jugular
- Left subclavian artery – below clavicle - arm flow
- Right external jugular - back down
Hormonal
Renin –> Angiotensin –> Aldosterone
Hormones always target……..
vascular smooth muscle (vasoconstrict or vasodilate)
and
regulate the activity of the vasomotor center
meaning - the medulla oblongata will be targeted to help dilate or constrict certain blood vessels
Renin is released by
kidneys
Renin leads to the production cascade –
Angiotensin
Renin leads to the production of
Aldosterone
What does Aldosterone do?
It goes back to the kidneys
causing increase absorption of Na+ & H2O
reabsorption of NA+ - water follows it
Resulting in retention of Na+ & H2O
causing secreting of K+
Meaning - you have a retention of fluid
Increasing blood volume
Increasing Blood Pressure
What hormone do you need when you have stress -
low BV
low BP
too much K+
too little Na+
Aldosterone
What raises BV and BP
Aldosterone
ADH
Epinephrine
What lowers BP
ANP
What does Epinpehrine do
Increase blood flow to a variety of areas in body
heart, lungs, brain, skeletal muscle
All about mobilizing resources
Vasoconstrict in the periphery
Which hormonal reflex leads to vasodilation VS vasoconstriction?
Renin
ANP
ADH
Epinephrine
ANP - Vasodilation
VASOCONSTRICTION =
Renin
ADH
Epinephrine
Every space that has fluid has ….
Hydrostatic pressure
Does not mean equal pressure
Just means it has pressure because there is fluid there - P’s law
Hydrostatic pressure
Pressure being exerted in a space
Osmotic Pressure
Solutes in a space creates osmotic pressure
Is all about the driving factor for osmosis and is created by tonicity
All about solutes not water
Tonicity - the solute or concentration gradient
Interstitial fluid is the point of….
connection - connects up the GI tract (ex)
More Hydrostatic pressure on which end?
Arteriole or Venule end?
Arteriole end = more
Venule end = less
Hydrostatic Pressure Capillary =
Blood Pressure (AKA)
HPc
Osmotic Pressure Capillary =
OPc
Creates osmotic pressure
plasma proteins & solutes
Hydrostatic Pressure interstitial fluid =
HPif =
lymph drainage works and maintains this 0 mmHg
Osmotic Pressure interstitial fluid =
OPif =
Solutes
As movement occurs the driving forces changes
HP & OP change upon movement
HP - Hydrostatic Pressure –
resists water entering a space
OP - Osmotic Pressure –
attracts water to enter a space
pulls water towards it
About SOLUTES
HPc & OPif –>
drive water out of a vascular system
towards solute
FAVORING DELIVERY
FAVOR PICKUP
HPif & OPc –>
move fluid into vascular system
BLOODSTREAM
Calculating Net Filtration Pressure
NFP. FORMULA
NFP = (HPc - HPif) - (OPc - OPif)
Alphabetical order
Which end of capillary does hydrostatic pressures dominate
Arterial end of capillary
Which end of capillary does osmotic forces dominate?
Venous end of capillary
In NFP, How does the excess fluid return to blood?
Lymphatic system
HPif = 0 because of
lymphatic drainage
Arterial end of NFP = normal range
10 mmHg
Fluid moves out
Positive values deliver goodies
Venule end of NFP = normal range
— 8 mmHg
Fluid moves in
ALWAYS NEGATIVE
Negative picks up waste
Positive values of NFP =
Fluid leaves capillaries
Moves out
Delivers goodies
Arterial end
Negative values of NFP =
Fluid returns to circulation
Moves in
Picks up waste
Four concepts of Venous return
- Thoracic Pump
- Skeletal muscle pump
- Cardiac Suction
- Gravity
Concepts of Venous return
Thoracic Pump
Pressure & Volume have an inverse relationship
All about breathing to help create appropriate venous return
When we breathe deeply –
1. Ribcage goes out
2. Diaphragm pushes down which creates low pressure in the thoracic cavity.
But - relatively high pressure in the abdomen.
Because of this pressure dynamic – High on abdomen; Low in the thoracic cavity –
The blood in the abdomen wants to push back towards the heart in the thoracic cavity
IN A CLOSED CIRCUIT - IF THE VOLUME INCREASES, WHAT HAPPENS TO THE BLOOD PRESSURE
BLOOD PRESSURE DROPS
Concepts of Venous return
Cardiac Suction
Ventricular systole enlarges atria and decreases pressure
(vena cava VS atrial)
Volume up, pressure down
When ventricle is in systole (contraction) pressure is high
Actually exerts a back pressure against the AV valve which enlarges the atria.
As the volume of the atria increases the pressure drops. Volume goes up, pressure goes down
Means the vena cavae pressure will still be higher (4.6 mmHg) than what the atria has during this phase.
Concepts of Venous return
Skeletal muscle pump
Contraction of muscle compresses the vein
- Helps push blood through the veins
- Valves will shut behind the blood, so blood will not flow backward with gravity back to toes
Where in the body is the lowest place of pressure?
In the atria
Concepts of Venous return
Gravity
Return from above the heart
Benefit of passing out - you will fall
Cardiovascular system does not have to work so hard against gravity - back to heart
Helps return body back to homeostasis
HPif should be ZERO. If it is not and number is up what could that indicate
Edema
Circulatory Shock
Heart function VS return problems
General idea …..Cardiac Output =
insufficient to meet metabolism
Reasons for Cardiac Output being insufficient?
Cardiogenic = heart damage -
(LVR) Low venous return =
Heart can only pump what it receives
Have to get blood back to heart
Hypovolemic Shock
Low volume - hypovolemic
Blood Volume Loss (LVR)
Two causes of Hypovolemic Shock
- Direct
- Indirect
Direct cause of hypovolemic shock -
Bleeding directly:
Hemorrhage, trauma, bleeding ulcer
Indirect cause of hypovolemic shock -
Indirect - Fluid Loss - dehydration
Fluid loss - NOT blood (burn & dehydration)
Two types of Circulatory Shock
- Hypovolemic Shock
- Vascular Shock
4 causes of Vascular shock
- Neurogenic
- Syncope
- Septic shock
- Anaphylactic
Vascular shock –
Volume normal, but accumulates in extremities (LVR) - low venous return
Vascular shock –
Neurogenic - a nervous system disruption that causes
widespread, sudden vasodilation (vast increase in blood volume)
Nervous system stops regulating
Vascular shock –
Syncope – VasoVagal
passing out
Brain perfusion falls…perfusion of medulla oblongata - vasomotor center monitoring oxygen delivery
Vascular shock –
Septic Shock
Bacterial Endotoxins – causes vasodilation in the body
Vascular shock –
Anaphylactic
increase in histamine (allergic reaction), causes massive vasodilation & permeability change shifts fluid in teh interstitial space.
Life threatening
Blocks airways
Edema face and neck
Systemic circuits (4)
- pulmonary circuit
- systemic circuit (body)
- Coronary circuit
- Hepatic-portal circulation
Coronary Circuit
Supplies the heart myocardium
Branch off ascending aorta
then dumps back of heart into venous sinus
Hepatic-portal circulation
Portal circulation is always – one capillary bed that leads to another
This is important for connecting the digestive system to the liver
Spleen, GI tract & accessory organs feed to liver before general circulation
Whole point is to have two capillary beds between arteries and veins
Goal –
as you absorb nutrients from the digestion system, the first place you go is the liver.
You need to detoxify things, store things, break things down (metabolize)
Liver and kidney take care of these functions
What is positive feedback saying?
Increase the outcome
Hypertension is accelerated by two positive feedback loops
Loop 1 - plaque formation blocks arteries & impedes flow
Loop 2 - Renal hypertension - thickening of arterioles in kidney
Hypertension — more…
More:
1. inflammation
2. damage
3. greater risk of hypertension
4. hardening of arteries
5. which is a repair process
Common causes of hypertension
- Chronic High Blood Pressure (140/90)
- loss of flexibility of vessels (atherosclerosis)
Resulting in:
expansion (systole) & recoil (diastole) being reduced and elevates pressure/
Causing the heart to work harder, causing hypotrophy - increase in muscle size of the heart - stress on heart and blood vessels
Like a rubber band - an old - crust-hard rubberband – not flexible. Breaks on you
Loop 1 - plaque formation blocks arteries & impede flow
Mostly inflammation -
Build up repair of damage within blood vessel
Part of natural formation of plaque hardening arteries
Increased risk of blood clots
Artery stretches – damages the endothelium lining – causing exposure to underlying structures (muscles) creating a site of further accumulation.
Inflammatory due to scab in hollow tube making it harder to send blood through.
How a heart attack, stroke, pulmonary embolism could occur - emboli frequently lodge on rough plaque surface
Loop 2 = Renal hypertension thickening of arterioles in kidney
Level of the kidney
- Kidney monitoring - sees not enough blood supply and thinks BV, BP are down
- sends out Renin –>Angiotensin –> Aldosterone Pathway
- Will hold onto Na+ & H2O
- Get rid of K+
== BV & BP go up – causes vasoconstriction
Makes heart work even harder
What holds the placenta in place?
Cotyledons
Umbilical Arteries
takes blood away from the baby - sends waste to mother for disposal
Umbilical Veins
Brings blood from mom to baby delivering the goodies to the baby
Ductus venosus
Bypasses the liver & drains to inferior vena cava
Liver in baby is developing
Cannot detoxify
Ductus arteriosus
Connects pulmonary artery to descending aorta, bypasses the lungs
Lungs are developing
Foramen Ovale
Connects right and left atria, bypasses lungs
Lungs developing
