Module 2 Introductory Anatomy and Physiology of Blood Vessels Flashcards
Compare and contrast the three tunics that make up the walls of most blood vessels
a
Distinguish between elastic arteries, muscular arteries, and arterioles on the basis of structure, location, and function
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Explain the structure and function of venous valves in the large veins of the extremities
a
Identify the major structures and subdivisions of the renal corpuscles, renal tubules, and renal capillaries
a
What is the tunica intima
- Innermost layer of a blood vessel
- > direct contact with blood as it flows through lumen
- Includes
- > Endothelial lining
- > -> Active participant in regulating vessel tone, coagulation, inflammation…
- > Basement membrane
- > In many vessels, an internal elastic lamina
What is the tunica media
- Middle layer containing concentric sheets of smooth muscle tissue in a framework of loose CT
- Collagen fibers bind all layers together
- Greatest variation among different vessel types
What is the tunica externa
- Outermost layer forming a CT sheath around the vessel
- Very thick and composed mostly of collagen fibers and some elastic fibers
- Contain numerous nerves and tiny blood vessels (vasa vasorum)
What is the sub-layers in the 3 layers in a blood vessel from internal to external
- Tunica intima (endothelium -> basement membrane -> internal elastic lamina)
- Tunica media (smooth muscle -> external elastic lamina)
- Tunica externa (loose fibrous CT -> epithelial cells)
In traveling from the heart to peripheral capillaries, blood passes through:
- Elastic/conducting
- > Large vessels, diameter up to 2.5 cm
- > Pressure reservoir - Muscular/distributing
- > Medium vessels, diameter around 0.4 cm - Arterioles
- > Smaller vessels, diameter around 30 µm
Fill in the blanks about elastic arteries:
Help ____ blood onward while the ventricles are _______
As blood is ejected from the heart into the elastic _____, their walls ______, easily accommodating the surge of blood.
As they stretch, the elastic fibers momentarily _______ mechanical energy functioning as a ______ reservoir.
Then, the elastic fibers ______ and convert stored (potential energy) in the vessel into _____ energy of the blood. Thus, blood continues to move through the arteries even when the ventricles are ______.
Help PROPEL blood onward while the ventricles are RELAXING
As blood is ejected from the heart into the elastic ARTERIES, their walls STRETCH, easily accommodating the surge of blood.
As they stretch, the elastic fibers momentarily STORE mechanical energy functioning as a PRESSURE reservoir.
Then, the elastic fibers recoil and convert stored (potential energy) in the vessel into kinetic energy of the blood. Thus, blood continues to move through the arteries even when the ventricles are RELAXED.
In Muscular Arteries, the
- > Tunica intima very thin and consists of:
1. _______
2. _________
3. ___________ - > Tunica media is major identifying characteristic:
1. ______________
2. _____________ - > (Thin/thick?) external elastic lamina
- > Tunica adventitia is (not/well?) developed
In Muscular Arteries, the:
- > Tunica intima very thin and consists of:
1. Endothelium
2. Flattened subendothelial layer of COLLAGEN and ELASTIC fibres
3. Internal ELASTIC LAMINA - > Tunica media is major identifying characteristic:
1. THICK SMOOTH MUSCULAR layer
2. very FEW ELASTIC fibres - > THIN external elastic lamina
- > Tunica adventitia is WELL developed
Where is the major site of systemic vascular resistance?
Arterioles
Terminal end (metarteriole) tapers towards capillary junction and forms _____
precapillary sphincter
Describe the 3 layers in arterioles:
- Tunica intima
- > Endothelium, no sub-endothelial layer - Tunica media
- > Composed of 1-3 layers of smooth muscle - Tunica adventitia
-> Fairly prominent
Lots of nerves
Describe venules:
- (Thinner/thicker?) walls than arterial counterparts
- ______ venule
- > Smallest venule - Form part of microcirculatory exchange unit with _____
- Muscular venules have thicker walls with _____ layers of smooth muscle
- THINNER walls than arterial counterparts
- POSTCAPILLARY venule
- > Smallest venule - Form part of microcirculatory exchange unit with CAPILLARIES
- Muscular venules have thicker walls with 1 OR 2 layers of smooth muscle
Fxn of veins
Collect blood from all tissues and organs and return it to the heart
How are veins classified?
- Classified on the basis of their size (3):
- Venules
- > Average diameter 20 µm - Medium sized
- > Diameter of 2 to 9 mm
- > Tunica media thin, thick tunica externa with longitudinal bundles of elastic and collagen fibers - Large
- > Diameter of 10 mm to 3 cm
- > Slender tunica media surrounded by thick tunic externa
Pressure in venules and medium sized veins is too ___ to oppose the force of ____
- LOW
2. GRAVITY
Veins contain ____ to prevent backflow of blood
one way valves
Venous valves fxn to
Compartmentalize the blood within the veins
Describe how pressure changes throughout Systemic system:
- From aorta (____ mmHg) to right atrium (_____mmHg)
- Pressure _____ as does velocity of flow
- Friction on walls (converted to _____, and decreasing pressure) is represented by _____
- Resistance and pressure drop is increased with ____ flow
- From aorta (95 mmHg) to right atrium (0-3 mmHg)
- Pressure DECREASES as does velocity of flow
- Friction on walls (converted to HEAT, and decreasing pressure) is represented by RESISTANCE
- Resistance and pressure drop is increased with TURBULENT flow
Describe how pressure changes throughout CAPILLARY BEDS:
- High as ___ at arteriole end, low as ___ at venous end
- Functional average is __mmHg
- High as 35 at arteriole end, low as 10 at venous end
- Functional average is 17mmHg
In the Theory of Circulatory Function, what are the 3 basic principles that underlie all functions of the system
- Blood flow to each tissue of body is almost always precisely controlled in relation to tissue needs
- CO is controlled mainly by the SUM of all the local tissue flows
- Arterial pressure is controlled independently of either local blood flow control or CO
Discuss the principle “The rate of blood flow to each tissue of the body is almost always precisely controlled in relation to the tissue need.”
- Active tissues can need as much as _____x the amount of blood flow compared to at rest BUT heart can only increase output ______x the resting levels
- Therefore, (it is/it is not?) possible simply to increase blood flow everywhere in the body when a particular tissue demands increased flow
- Instead, the microvessels of each tissue continuously monitor tissue needs, (e.g. availability of ______ and ______ and the accumulation of ____ and other waste products)
- These in turn act directly on the ________, dilating or constricting them, to control local blood flow precisely to that level required for the tissue _____.
- Active tissues can need as much as 20-30x the amount of blood flow compared to at rest BUT heart can only increase output 4-7x the resting levels
- Therefore, IT IS NOT possible simply to increase blood flow everywhere in the body when a particular tissue demands increased flow
- Instead, the microvessels of each tissue continuously monitor tissue needs, (e.g. availability of OXYGEN and NUTRIENTS and the accumulation of CO2 and other waste products)
- These in turn act directly on the LOCAL BLOOD VESSELS, dilating or constricting them, to control local blood flow precisely to that level required for the tissue ACTIVITY.
Discuss the principle “The CO is controlled mainly by the sum of all the local tissue flows.”
- When blood flows through a tissue, it immediately returns by way of the ____ to the heart.
- The heart responds automatically to this increased inflow of blood by pumping it immediately into the ____ from whence it had originally come.
- Thus, the heart responds to the ____ of the tissues.
- When blood flows through a tissue, it immediately returns by way of the VEINS to the heart.
- The heart responds automatically to this increased inflow of blood by pumping it immediately into the ARTERIES from whence it had originally come.
- Thus, the heart responds to the DEMANDS of the tissues.
Discuss the principle “In general the arterial pressure is controlled independently of either local blood flow control or cardiac output control.”
- The circulatory system has an extensive system that controls the ______ BP.
- g. if at any time the pressure falls significantly below the normal level of about ____mmHg, within seconds _____ reflexes will raise the pressure back toward normal.
- The circulatory system has an extensive system that controls the ARTERIAL BP.
- g. if at any time the pressure falls significantly below the normal level of about 40mmHg, within seconds NERVOUS reflexes will raise the pressure back toward normal.
Carotid sinus baroreceptors respond in the range of ____
~40-240mmHg??
Aortic arch baroreceptors are stimulated in the same manner, but tend to fire at about ____mm Hg higher than the carotid sinus receptors
30 mmHg
Baroreceptor response is important for ____-term correction of BP
Short-term
A decrease in arterial pressure _____ the baroreceptors - the terminals of afferent fibers of the _______ and ______ nerves - that are situated in the ______ and ______. This leads to a ______ in the afferent impulses that are relayed from these mechanoreceptors through the glossopharyngeal and vagus nerves to the ______ in the dorsomedial medulla. The reduced baroreceptor afferent activity produces a ______ in vagal nerve input to the sinus node that is mediated by the neuroanatomical connections of the NTS to the _________. There is an _____ in sympathetic efferent activity that is mediated by the NTS projections to the _________ (an excitatory pathway) and from there to the __________ (an inhibitory pathway). The activation of RVLM presympathetic neurons in response to hypotension is thus predominantly due to ________. In response to a sustained fall in blood pressure, _______ release is mediated by projections from the ______ cell group in the ventrolateral medulla. This projection activates vasopressin-synthesizing neurons in the magnocellular portion of the _______ and the ________ of the hypothalamus. Blue denotes sympathetic neurons and green parasympathetic neurons.)
A decrease in arterial pressure UNLOADS the baroreceptors - the terminals of afferent fibers of the GLOSSOPHARYNGEAL and VAGUS nerves - that are situated in the AORTIC ARCH and CAROTID SINUS. This leads to a REDUCTION in the afferent impulses that are relayed from these mechanoreceptors through the glossopharyngeal and vagus nerves to the NUCLEUS OF THE TRACTUS SOLITARIUS (NTS) in the dorsomedial medulla. The reduced baroreceptor afferent activity produces a DECREASE in vagal nerve input to the sinus node that is mediated by the neuroanatomical connections of the NTS to the NUCLEUS AMBIGUUS (NA). There is an INCREASE in sympathetic efferent activity that is mediated by the NTS projections to the CAUDAL VENTROLATERAL MEDULLA (an excitatory pathway) and from there to the ROSTRAL VENTROLATERAL MEDULLA (an inhibitory pathway). The activation of RVLM presympathetic neurons in response to hypotension is thus predominantly due to DISINHIBITION. In response to a sustained fall in blood pressure, VASOPRESSIN release is mediated by projections from the A1 NORADRENERGIC cell group in the ventrolateral medulla. This projection activates vasopressin-synthesizing neurons in the magnocellular portion of the PARAVENTRICULAR NUCLEUS (PVN) and the SUPRAOPTIC NUCLEUS (SON) of the hypothalamus. Blue denotes sympathetic neurons and green parasympathetic neurons.)
What is the myogenic hypothesis?
- Maintains constancy
- Smooth muscle stretching → constriction
- ↓ stretch → dilation
Likely has very little physiologic significance – metabolic autoregulation seems to be much more important
What is the metabolic hypothesis?
O2, CO2, H+, K+, lactate, adenosine, K+ accumulate and lead to vasodilation
How do metabolic byproducts act in neg feedback
- metabolic byproducts leads to vasodilation -> increased blood flow leads to washout of the same metabolites
How can metabolic byproduct lead to REACTIVE HYPEREMIA?
after a period of vasoconstriction, metabolites build up and lead to a period of vasodilation and greatly increased PERFUSION
What hormones cause vasodilation?
- NO (produced by endothelial cells). Shear stress (↑ P) leads to its release → arteriole dilation
- Ach → NO production (erectile tissue)
- Histamine: vasodilates arterioles, constricts venules → edema
- Bradykinin: circulating protein, activated by inflammatory signals
- > Potent vasodilator - Prostaglandin E2 and I2
- ANP (atrial natriuretic protein) – dilates
- Epinephrine, norepinephrine through beta-2 receptors
What hormones cause vasoconstriction
- Epinephrine, norepinephrine through alpha-1 receptors
- Serotonin – released in tissue damage → local vasoconstriction
- > When released by platelets or GI tract, sometimes results in vasodilation - Prostaglandins A2 and F constrict
- Angiotensin II
- ADH constrict (long term water regulation)
- Reaction to damage (platelet plug formation)
Does epinephrine or norepinephrine have a greater effect on a1, a2, b1, and b2 receptors
- Epinephrine has greater effect on B2 receptors than norepinephrine
- they’re ~equal for a1, a2, and b1
Fxn of B2?
causes vasodilation in skeletal muscle, cardiac muscle and liver
Fxn of alpha receptors
cause vasoconstriction in all tissues including muscle
Describe the renin-angiotensin aldosterone system (not examable?)
- a hormone system that regulates blood pressure and fluid balance.
When renal blood flow is reduced, juxtaglomerular cells in the kidneys convert the precursor prorenin (already present in the blood) into renin and secrete it directly into the circulation. Plasma renin then carries out the conversion of angiotensinogen, released by the liver, to angiotensin I.[2] Angiotensin I is subsequently converted to angiotensin II by the angiotensin-converting enzyme (ACE) found on the surface of vascular endothelial cells, predominantly those of the lungs.[3] Angiotensin II is a potent vasoconstrictive peptide that causes blood vessels to narrow, resulting in increased blood pressure.[4] Angiotensin II also stimulates the secretion of the hormone aldosterone[4] from the adrenal cortex. Aldosterone causes the renal tubules to increase the reabsorption of sodium and water into the blood, while at the same time causing the excretion of potassium (to maintain electrolyte balance). This increases the volume of extracellular fluid in the body, which also increases blood pressure.
The rate at which different substances are excreted in the urine represent the sum of WHAT three renal processes
- Glomerular filtration
- Reabsorption of substances from renal tubules into the blood
- Secretion of substances from the blood into the renal tubules
What is the equation for urinary excretion
Excretion = Filtration - Reabsorption + Secretion
What does the renal corpuscle consist of
- Bowman’s capsule (parietal and visceral layers)
- Bowman’s space (between the parietal and visceral layers)
- Glomerular capillary loop
What are 3 key histologic and physiologic features:
- shared basement membrane of the glomerulus and pedicel
- filtration slit
- fenestrations
Blood enters the glomerular capillary via the ______
afferent arteriole
What determines the rate and amount of fluids and small solutes that filter through the fenestrations in the glomerular capillary,
The hydrostatic and osmotic pressure in the glomerular capillary
Fxn of The basement membrane, the fenestrations, and the filtration slits formed by the pedicels
regulate the filtration of larger, charged molecules,
Where does The fluid that collects in Bowman’s space flow
into the proximal convoluted tubule.
