Chapter 20: Blood Vessels and Circulation Flashcards
What are the 3 types of blood vessels?
arteries, veins, and capillaries
Artery and vein walls are made up of what 3 layers?
- Tunica interna
- Tunica media
- Tunica externa
Which tunica is the thickest?
Tunica Media
Explain the anatomy of the tunica interna.
- endothelium made of Simple Squamous Epithelium
- selectively permeable barrier
- secretes chemicals to attract or repel formed elements
Explain the anatomy of the Tunica media.
- smooth mucle (changes the diameter of the vessel)
- collagen
- elastic tissue in arteries
- provides vasomotion and strength to vessel
Explain the anatomy of the Tunica externa,
- loose CT anchors vessel to tissue
- vasa vasorum supplies large vessel walls
What are the different types of arteries?
- Conducting arteries
- Distributing arteries (“off ramp”)
- Resistance arteries
- Metarterioles
What types of arteries are the largest and the smallest?
largest- conducting arteries
smallest- metarterioles
Conducting arteries are thick enough to require its own blood supply called what?
Vasa vasorum
Why do conducting arteries have elastic tissue?
for stretch and recoil
What type of artery is the common carotid?
conducting artery
another is the aorta!
Elastic tissue, smooth muscle, and collagen are in the tunica media of which type of arteries?
Conducting arteries
Distributing arteries have more muscle then what type of tissue?
elastic tissue
Where do distributing arteries bring blood?
to organs after which they are named. eg. brachial, femoral, renal
Resistance arteries come in 2 sizes, larger and smaller. explain the difference.
Bigger one have lots more muscle
Smaller ones are ARTERIOLES (thin layer of smooth muscle tissue)
Which tunica layer is the smallest in resistance arteries?
tunica externa
What is the function of resistance arteries?
vasomotion
What do metarterioles link?
arterioles and capillary beds
In metarterioles, the tunica media is not continuous, instead there are individual smooth muscle cells from the precapillary sphincter that does what?
encircle entrance to one capillary and control flow of blood to capillaries
What do arterial sense organs do?
regulate HR, vasomotion and respiratory rates.
What are the 2 atrial sense receptors?
baroreceptors and chemoreceptors
What do baroreceptors sense and where are they located?
Blood pressure sensors
located in carotid sinuses and aortic arch
Why do baroreceptors have thin-walled tunica medias?
so that it stretches easily when BP increases
In baroreceptors, the glossopharyngeal nerve fibers in the tunica externa stimulates and sends messages to what?
- Cardioacceleratory or cardioinhibitory centers to change HR
- Vasomotor centers to change vessel diameter (vasomotion)
If BP decreases, baroreceptors will send signals to where?
- cardioacceleratory center to increase HR
- vasomotor centers to vasoconstrict vessels in the digestive, urinary, reproductive systems to increase BP
What do chemoreceptors sense and where are they located?
pH sensors in carotid bodies, aortic bodies, and medulla.
What are capillaries made of?
thin wall of simple squamous epithelium and basement membrane
Capillaries are considered the site of what?
site of exchanging nutrients/wastes, oxygen/carbon dioxide with tissue fluid
What is the average diameter of a capillary?
7um
What are the different types of capillaries?
- continuous capillaries
- fenestrated capillaries
- sinusoids (not a cap. bed)
- capillary beds
What are veins?
Capacitance vessels- 54% of all the blood
What are the different types of veins?
postcapillary venules muscular venules medium veins venous sinus large veins
Where is the site of leukoctye movement into tissues from blood?
postcapillary venules
What is the function postcapillary venules?
receives blood from capillaries
it is very porous so exchange of materials with tissue fluid occurs.
What are venous sinuses?
cavities that collect venous blood
What is a simple pathway circulatory route?
heart –> arteries –> capillaries –> veins –> heart
blood flows thru ONE network of capillaries
What is a portal system circulatory route?
blood flows through 2 consecutive capillary beds
Explain the circulatory route of the hepatic portal system.
Blood to intestines –> capillary bed in intestines –> hepatic portal vein –> capillary bed in the liver –> veins back to heart
What is the arteriovenous anastomosis circulatory route?
blood flows directly into vein- bypasses capillary bed (SHUNT)
eg. hands and feet
What is the atrial or venous anastomosis circulatory route?
one artery to another or one vein to another
provides alternate routes for blood flow
eg. coronary circulation
What is the usual cardiac output (CO)?
5.2L/min
How do you calculate Blood flow and perfusion?
blood flow = volume of blood/min (mL/min)
perfusion = blood flow per g tissue (mL/min/g)
Regional blood flow varies in most tissues except ______.
the brain
Blood flow is determined by the interactions between what 2 things?
pressure and resistance
What is blood pressure?
the force that the blood exerts on a vessel wall
measured in mm Hg
What are the 2 pressures recorded when taking your blood pressure?
Systolic: peak arterial during ventricular contraction (120)
Diastolic: minimum arterial during relaxation (75)
How do you measure Pulse Pressure?
systolic pressure - diastolic pressure
120mm Hg - 75mm Hg = 45mm Hg
What is pulse pressure?
measure of stress exerted on small arteries by the sressure surges generated by the heart
How do you measure the mean arterial pressure?
Diastolic pressure + (Pulse pressure/3)
75mm Hg + (45mm Hg/3) = 90mm Hg
Pulse Pressure=systolic pressure - diastolic pressure
120mm Hg - 75mm Hg = 45mm Hg
What is hypertension?
chronic resting BP higher than 140/90
What is hypotension?
chronically low resting BP
What are the determinants of BP?
1.Cardiac output (CO) -regulated by SV, HR
2.Blood volume- regulated in kidneys
3.Resistance to flow-(friction of blood against walls)
-regulated by blood viscosity, vessel
length and vessel radius
What is peripheral resistance?
the resistance that the blood encounters as it flows away from the heart
What is Afterload?
the pressure in arteries just outside semilunar valves
If the afterload increases then blood has a hard time flowing out of the heart creating what?
increased resistance
What determines the bloods viscosity?
albumin concentration and erythrocytes
If the blood viscosity increases, the resistance increases and flow decreases. what is this an example of?
Dehydration
Why is the aorta have fast flow compared to the slow flow of the capillaries?
River(aorta) dumping into a lake(capillaries)
- increased vessel length (moving further away from heart)
- decreased radius of the vessel
- increased total area of all vessels
- aortic blood is distributed over a greater total area
Why are capillaries blood flow slow compared to the faster flow of veins?
Lake (capillaries) dumping into a river(vein)
- increased radius of the vessel
- decreased total area of all vessels
- large amount of blood forced into smaller channel
What regulates BP and flow?
- local control
- neural control
- hormonal control
What is autoregulation?
ability of tissues to regular their own blood supply
What is reactive hyperemia?
blood supply to tissues is cut off then restored above normal level of flow
What is angiogenesis?
new growth of blood vessels
eg. monthly regrowth of lining of uterus, increased capillaries in muscles of athletes.
Neural control is regulathe ted by what part of the nervous system?
autonomic nervous system
Baroreflex is a homeostatic negative feedback loop. what are the control centers for HR and for peripheral resistance?
HR- cardioacceleratory and cardioinhibitory centers
peripheral resistance- vasomotion center
What are the effectors for HR and peripheral resistance of baroreflexs?
HR- sympathetic or parasympathetic outflow to SA node
Peripheral resistance- smooth muscle of arteries= vasomotion
For the chemoreflex, what is the control centers for HR and peripheral resistance?
HR- respiratory centers
Peripheral resistance- vasomotor centers
What are the 3 types of reflexes within neural control?
baroreflex, chemoreflex, and medullary ischemic reflex
What are the 3 types of capillary exchange?
- diffusion
- transcytosis
- filtration and reabsorption
What can diffuse through plasma membrane of endothelial cells?
O2, CO2, small lipids
How do larger molecules that cant diffuse through plasma membrane get out of endothelial cells?
move through membrane channels, intercellular clefts, or fenestrations
eg. glucose, electrolytes (salt)
What is transcytosis?
droplets that travel through endothelial cell in a vesicle
- pinocytosis on one side, then exocytosis on the other
eg. fatty acids, insulin, albumin
The net filtration of the kidney is due to what?
to high hydrostatic pressure (glomeruli)
The net reabsorption of the lungs is due to what?
to low hydrostatic pressure
-so fluid doesnt fill air spaces
What is edema?
accumulation of excess fluid in a tissue (swelling)
occurs when filtration>reabsorption
Where does systemic and Pulmonary edema occur?
systemic- tissues
pulmonary- lungs
What are the 3 causes of edema?
- increased capillary filtration
- decreased capillary reabsorption
- obstructed lymph drainage
What are the ;mechanisms of venous return>?
- Pressure gradient (*most important mechanism)
- Gravity
- Skeletal muscle pump
- Respiratory pump
- Cardiac suction
What are the 2 types of circulatory shock that occur when CO doesnt meet metabolic needs?
- Cardiogenic shock
- due to decreased pumping of the heart
- Low venous return (LVR) shock
What are the 3 types of low venous return (LVR) shocks?
- hypervolemic shock
- obstructed venous return shock
- venous pooling shock
What are the 2 responses to circulatory shock?
- compensated shock- homeostatic mechanisms return CO to normal
- Decompensated shock-positive feedback loop-life threatening
There are 3 places in which there are special circulatory routes, what are they?
Brain, Lungs, and Skeletal muscles
