What are the 3 layers of a vessel?
Tunica interna Tunica media Tunica externa
What does the tunica interna do?
produces secretions
What does the tunica media do?
contract SM for vasomotor control
Where is the tunica Interna?
vessel lumen
Histology of tunica interna
simple squamous
What composes the tunica media?
SM, collagen, elastin
What composes tunica externa of arteries?
collagen and elastin
What composes tunica externa of veins?
elastin and SM
How is SM regulated?
sympathetic neurons which controls vasomotor
What is the bulkiest arterial layer?
tunica media
What is the bulkiest venous layer?
tunica externa
What does the tunica externa do?
anchors vessels to surrounding tissue
What composes the tunica externa in large veins?
elastin
What do large vessels have within the tunica externa?
network of vessels
What is vasa vasorum?
network of vessels within vessels
What do arteries do?
O2 rich blood away from heart
What do veins do?
O2 poor blood to heart
Blood flow pathway
Heart Arteries Arterioles Capillaries Venules Veins Heart
What are the 3 types of arteries?
Elastic
Muscular
Resistance
What happens to artery diameter as it moves away from heart?
decreases
What are elastic arteries also known as?
conducting
What are muscular arteries also known as?
distributing
What do elastic arteries do?
Shock absorbers that fluctuate with BP changes
What do elastic arteries not fluctuate in response to?
vasomotor control
What do elastic arteries prevent?
pressure surges from damaging artery walls
What are examples of elastic arteries?
aorta subclavians common carotids
What is arteriosclerosis?
narrowing of lumen which decreases artery flexibility
What does arteriosclerosis produce?
aneurysms which can hemorrhage
What does arteriosclerosis more likely affect?
smaller vessels with thin walls
What is an aneurysm?
weakened vessel wall
Which arteries are pressure smoothing to promote steady flow?
elastic
Which artery type is most common?
muscular
Which artery type responds to vasomotor control?
muscular
Which artery type are pulse points?
superficial muscular
What are examples of muscular arteries?
radial, brachial, femoral
Rank arteries from largest to smallest
Elastic Muscular Resistance
How many tunic layers do small resistance arteries have?
Very small?
Small = all 3
Very small = only interna and media
What do resistance arteries respond to?
neural, hormonal, paracrine signals
Why can resistance arteries not handle BP surges?
not elastic
What are resistance arteries control points of?
perfusion
What are the 3 types of capillaries?
continuous
fenestrated
sinusoids
What is the function of capillaries?
gas exchange with tissues
What layers are in capillaries?
only tunica interna
What is a network of capillaries known as?
bed
What is microcirculation?
blood flow through capillaries
also microvasculature
What do continuous capillaries diffuse?
water and small molecules
What do sinusoid capillaries diffuse?
large molecules blood cells
Rank capillaries from least to most permeable
Continuous Fenestrated Sinusoids
What type of capillary prevents protein and blood cell loss?
Continuous
What do continuous capillaries have for extra screening and protection?
specialized tight junctions
Where are continuous capillaries found?
muscles, skin, lungs
What do fenestrated capillaries have?
large lumens and pores
What are examples of fenestrated capillaries?
Kidneys = filter blood Intestines = absorb nutrients Endocrine = hormone uptake and release
What are sinusoid capillaries also known as?
discontinous
What are the characteristics of sinusoid capillaries?
large lumens and irregular shape
What is the speed of flow in sinusoid capillaries?
slow
What are examples of sinusoid capillaries?
Marrow Liver Lymph tissue Endocrine organs
Which has lower BP: veins or arteries
veins
What happens to vein diameter as it gets closer to heart?
increase
What happens at postcapillary venules?
WBC exchange
What are the characteristics of postcapillary venules?
small, porous endothelium
What happens when WBC cling to postcapillary lining and move out of tissue?
inflammation
What layers are present in muscular venules?
all 3 layers
Compare wall thickness for veins and arteries
Thinner walls in veins
Compare lumen size in veins and arteries
Larger lumens in veins
Which BV can accommodate larger volumes of blood?
veins
What are veins also known as?
capacitance vessels blood reservoirs
What do veins not have in their tunica media?
SM and elastin
Why do veins have a low chance of bursting?
low BP
How is vein flow assisted?
valves low resistance large lumen
Where are valves very abundant?
limbs because they can counteract gravity
What are venous sinuses?
Drains
Specialized flattened veins without SM
What are the 5 mechanisms of venous return?
Skeletal muscle pump
Respiratory/thoracic pump
Cardiac suction
Gravity
Valves
How is venous return achieved through the skeletal muscle pump?
Exercises contracts skeletal muscle and pushes flow along
How is venous return achieved through the respiratory/thoracic pump?
Inhalation increases volume and decreases pressure to move blood
How is venous return achieved through cardiac suction?
heartstrings pull AV valves down to create suction and pull blood from IVC/SVC
How is venous return achieved through gravity?
downhill return from upper body
How is venous return achieved through valves?
inward foldings prevent backflow in limbs
What are varicose veins?
superficial veins that bulge and twist in lower limbs
from weak valves and walls
What causes varicose veins?
Heredity Excess weight standing too long strain
What are hemorrhoids?
anal varicose veins
What is anastomoses?
vessel merger
What are the 3 types of anastomoses?
Arterial
Venous
arteriovenous
What are arterial mergers?
alternative routes for arteries to prevent occlusions
Brain heart Abdomen
What are venous mergers?
alternative routes for drainage
What are arteriovenous mergers?
Connect arterioles to venules to bypass capillaries
Fingers toes ears
What is the function of arteriovenous mergers?
thermoregulation
What are portal systems?
specialized routes of flow where blood passes through 2 capillary networks
Kidney Hypothalamus/ant pit
What is perfusion?
blood flow
What is hemodynamics?
principle of flow
What is blood flow based on?
pressure resistance
What is flow?
volume of blood in time (mL/min)
What is perfusion measured in?
flow per tissue mass
mL/g/min
What is total systemic flow equal to?
cardiac output
What is pressure?
force blood exerts on vessel wall
mmHg
How is pressure influenced?
compliance (elasticity)
flow
Pressure is measured with what?
sphygmomanometer
What is peak arterial BP known as?
Systole Ventricular contraction
What is minimal arterial BP?
Diastole Ventricular relaxation
What happens to pressure when compliance decreases?
increases (indirect)