Ch. 19 The Blood Vessels Flashcards
Blood Vessel Antomy: Arteries
Arteries/arterioles
Function: carries blood away from heart to tissues
Tunica externa: tough connective tissue
Tunica Media: tick, more smooth tissue for vasoconstriction
Tunica intima/interna: endothelium, simple squamous, round lumen
Blood Vessel Anatomy: Capillaries
Function: bridge arteries and veins, site of exchange/permeable
Tunica externa: N/A
Tunica Media: N/A
Tunica intima/interna: simple squamous endothelium
Blood Vessel Anatomy: Veins
Veins/venules
Function: carry blood from tissues to the heart
Tunica externa: tough connective tissue
Tunica Media: thin, less smooth muscle
Tunica intima/interna: endothelium but veins have valve to prevent backflow. large, slit like lumen
Types of Arteries: Elastic, Muscular, and Arterioles (anastamoses)
- Elastic
structure- closest to the heart, large diameter, thick tunica media with tons of elastins
function-pressure resrvoirs, “conducting arteries” - Muscular
structure- further away from heart, very thick tunica media, less elastin
function- preform vasoconstriction, “distributing arteries” - Arterioles
structure- small in diameter, few muscle layers
function- “resistence vessels” controls blood flow into capillary system
anastamoses: union of vessel branches supplies the same region of the body/alternate routes for blood flow
Types of Capillaries: continuous, fenestrated, and sinusoidal (vascular shunts)
- Continuous
Structure: simple squamous endothelium with intercelluar clefts/gaps
Function: most abundant site of exchange - Fenstrated
Structure: simple squamous endothelium with fenstrations/windows with IC clefts
Function: in organs that filter (kidneys) - Sinusoidal
Structure: simple squamous endothelium with large sinuses, very wide IC clefts
Function: allows large particles through as cells (bone marrow)
vascular shunts- “reroutes”, blood can be rerouted where smooth muscles contracts to minimize blood flow and relax to increase blood flow
Capillary Exchange (starlings law of Capillary exchange) OP AND HP
starlings law of Capillary exchange: osmotic Pressure OP and hydrostatic pressure HP drive fluid movement
-net filtration pressure depends on HP and OP
On the arteriole end of capillaries:
1. OP will want to push fluid into capillaries
2. HP within capillaries is higher than OP
3. therefore, fluid is pushed out of capillaries/filtration
On the venule end of capillaries:
1. HP will want to send fluids out of vessel
2. OP within capillaries is higher than HP
3. Therefore, fluids are pushed in to the capillaries/reabsorption
Types of Veins: venules and veins
60% of our blood is sitting in our veins
Venules and veins common function: carry blood from tissue to heart “venous return”
Venules structure:
a. post capillary venules: formed when capillaries merge, look like capillaries (only tunica
interna)
b. large venules: look like small veins- have some smooth muscle
Veins structure: formed when venules merge. look like typical veins with valves too prevent
backflow. “blood resrvoir” low pressure type blood vessels
Venous Return
A. Problem- veins are low pressure vessels and are unable to effectively pump blood back
to the heart
B. Solution-
1. valves prevent backflow
2. External pump 1- respiratory movements, diaphragm (pumps help to work against
gravity)
3. External pump 2- muscular movements, moving squeezes the blood vessels
making them a high pressure
Factors that affect Blood Pressure (Flow, Resistance)
Flow: (F) volume of blood that flows over time (mL/min)
Total blood flow= CO (cardiac output= SVxHR)
a. blood will flow from areas of high HP to low HP.
b. the heart is the pump that generates the pressure to make blood flow
high pressure= high blood flow= constricted blood vessels
c. flow/co and bp are directly proportional to each other
high CO= high BP
Low CO= low BP
Resistance: (R) opposition of flow
a. blood viscosity (hematocrit)
plycythemia: thick blood = poor blood flow = high resistance
anemia: thin blood = high blood flow = low resistance
Factors that affect Blood Pressure (Length and diameter)
Length
1. Long vessels: high amount of friction = high R
2. Short vessels: low amount of friction = low R
Diameter
1. Small diameter: constricted, low flow, high R
2. large diameter: dilated, high flow, low R
R and BP are directly proportional to each other but inversely proportional to diameter.
1. low diameter/constriction= high R = high BP
2. high diameter/dilation = low R = low BP
Maintaining Short-Term BP Regulations (Baroreceptors)
Baroreceptors: located in blood vessels and triggered by fluctuations
Neural controls: Alter CO and R to adjust for ST BP fluctuations
1. Location: Brainstem/Medulla Oblongata’s CV center (cardiovascular)
2. The clusters of neurons responds to…
a. Baroreceptors: pressure receptors
(Negative feedback loop)
-stimulus: when hypertensive, baroreceptors are triggered
-impulse sent to medulla oblongata to stimulate CV center and vasomotor center (muscle)
-lowers HR leading to lowered R and BP
-dilates vessels diameter leading to lower R and BP
-BP is regulated short-term
OPPOSITE WHEN HYPOTENSIVE
Maintaining Short-Term BP Regulations (Chemoreceptors)
Chemoreceptors: chemical receptors located close to the barorceptors (in blood vessels)
Detect the following:
1. elevated CO2 (hypercapnia) no gas exchange
2. Low O2 (hypoxia) no gas exchange
3. Low pH due to build up of carbonic acid due to elevated CO2 (acidosis)
Under these conditions the chemoreceptors…
a. will activate CV center (cardioacceleration) and trigger vasomotor (vasoconstrict) to
raise BP
Chemoreceptors stimulate a raise in BP in order to push more blood to the pulonary curcuit. doing so helps flush the CO2 out of blood stream and more O2.
3. cerebrum and hypothalamus: higher brain center can also alter BP
a. cerebrum: mood, thoughts, emotions
b. hypothalamus: (no control) mediate stress response through the fight-or-flight
mechanism when the body is active or in motion.
Hormone Controls: Short Term (4 different hormones)
Hormonal cues can also alter BP in order to adjust to moment-to-moment fluctuations.
Epinephrine and NE
BP effect: increases BP
Mechanism: increase HR and contractility. Promotes vasoconstriction
Angiotensin II
BP effect: increases BP
Mechanism: stimulates intense casoconstriction and the release of ADH and
aldostrone for long term controle
Anti-diuretic Hormone (ADH)
BP effect: increases BP
Mechanism: causes intense vasoconstriction. Stimulates kidneys to conserve water
Atrial Natriuetic Peptide (ANP)
BP effect: lowers BP
Mechanism: causes generalized vasodilation and antagonizes aldosterone
