AP2 Exam 2 Flashcards
Blood composition:
40% blood cells (solid portion); RBC, WBC, PLTs
60% plasma (fluid portion): electrolytes (maintains osmolarity ~300mOsm/L) and proteins (albumins, globulins, fibrinogens)
Structure of arteries and veins (picture)
- Tunica externa aka adventitia: connective tissue, nervi vasorum, and vasa vasorum
- Tunica media: smooth muscle is innervated by SNS only
- arteries: external elastic lamina
- Tunica interna aka intima:
- arteries: internal elastic lamina
- veins: valves (more in lower limbs than upper) present
Tunics: Arteries vs. Veins (table)
Tunica interna/intima
Tunica media
Tunica externa/adventitia
The endothelium of the tunica interna/intima produces the following:
- Endothelin: vasoconstrictor
- Nitric oxide: vasodilator
- Prostacyclin: vasodilator; type of prostaglandin
- Thromboxane: vasoconstrictor
- tPA: promotes fibrinolysis
- vWF: promotes PLT aggregation
Additionally, the endothelium proliferates to form new cells during repair (angiogenesis)
Two types of arteries:
gradual transition from elastic to muscular (no clear demarcating line)
elastic (aka conducting arteries): highest % elastic fibers in tunica media; found closest to heart (aorta thru common carotid and iliacs; pressure reservoir [potential energy of the stretch])
muscular (aka distributing arteries): more muscle in tunica media (still some elastic recoil however relies on musculature to push blood fwd)= more vasodilation/constriction= adjust rate of flow; axillary, brachial, femorals
Anastomoses should only occur between ______ vessels.
like
*collateral circulation: results when blockage or flow slows in small vessels
Neovascularization:
vasculogenesis: occurs mostly in embryonic development; hemangioblasts proliferate
angiogenesis: new vessels from pre-existing vessels (new cap. from post cap. venules); triggered by hypoxia or damage
arteriogenesis: remodeling of existing vasculature>leads to collateral circulation; triggered by exercise or ischemic vascular disease
De novo means:
from the new
Arteriole structure:
aka resistance vessels
Tunica externa: very thin
Tunica media: 1-2 layers of smooth muscle; sympathetic vascular tone
Tunica intima: thin layer
Arterioles:
aka resistance vessels: resistance is due to blood components rubbing against the vessel wall
Metarteriole:
- short vessels that connect arterioles to the capillary networks
- structural characteristics of both an arteriole and capillary:
- arteriole-metarteriole junction: normal tunica media layer allowing for vasodilation/constriction
-
metarteriole-capillary junction: single circumferential smooth muscle cells that can acts as a sphincter (precapillary sphincter)
- thoroughfare channel: when precapillary sphincters are all closed, blood flows from arteriole>metarteriole>thoroughfare channel>venule
Capillaries:
aka exchange vessels; extensive number of cap. increase SA>rapid exchange of materials
exchange of nutrients and waste products can only occur at capillary post AND capillary venule level
very small: blood cells must slow down= buys time for exchange
capillary bed: arise from a single metarteriole
vasomotion: periodic relaxation/constriction of precap. sphincters (ensures blood flow at rest)
Types of capillaries:
- all cap. consists only of single endothelial layer and basement membrane (no tunica interna/externa)
- continuous:
- most common
- endothelium is continuous with small intercellular clefts (exchange of smaller molecules)
- CNS, lungs, muscle, skin
- fenestrated:
- many fenestrations (larger particles) and clefts
- kidneys, endocrine glands, villi of small intestine, choroid plexus, ciliary process of the eyes
- sinusoid:
- least common
- incomplete or absent basement membranes
- unusually, very large fenestrations and intercellular clefts
- may contain specialized cells (e.g. kupffer cells)
- liver, marrow, spleen, lymph nodes (lymph fluid), endocrine glands
Capillary portal systems:
blood passes from one capillary network into another capillary network
e.g. hypophyseal and hepatic portal systems (first pass)
Postcapillary venules:
allow for diapedesis (WBCs moving into tissues) due to porous nature
only other site of metabolic exchange
Muscular venules:
1-2 layers of smoother muscle
no metabolic exchange
most distensible elements of entire vascular system (reservoir for blood prn)
The thin walls of both ______ and ______ venules make them the most distensible elements of the entire vascular system.
postcapillary and muscular
serve as reservoirs of large amounts of blood prn
Veins have high capacitance: explain
capacity to distend to store high volume of blood
*lack internal and external elastic laminae= very inelastic
Most venous walls are ______ layers of smooth muscle with ______ amount of elastic and collagen fibers
thin
small
Low blood pressure in the veins allows blood to flow backwards (to a point): when?
during ventricular diastole
to a point: valves>cusps project into the lumen with the cup portion aiming toward the heart
Vascular sinus
vein with thin endothelial wall
no smooth muscle
dense connective tissue replaces tunica media and externa (provides support)
examples include: coronary sinus
Why do our veins appear blue?
venous blood is deep dark red but their thin walls and tissue of the skin absorbs red light wavelengths
this allows blue light to pass through the surface where we see them as blue
Superficial veins form small connections with deep veins via:
perforating veins
superficial veins lie in the SC layer
deep veins travel between muscles
Upper vs Lower limbs (veins)
- Upper:
- superficial larger than deep
- some superficial dump directly into vena cava (bypass deep veins)
- Lower:
- deep larger than superficial
- serve as the principle return pathway to heart
- one-way valves in perforating vessels allow blood to pass from superficial to deep veins, but prevent reverse flow
Varicose veins
- leaky venous valves cause veins to become dilated and twisted (varicose)
- blood pooling creates pressure that distends vein= fluid leaks into surrounding tissue
- may cause vein and tissue to become inflamed and tender
- valvular defect can occur from congenital, mechanical issues, or aging
- Treatment includes: elastic stockings, sclerotherapy, laser, and stripping (removal)
- most common in: superficial veins of lower limbs (valves fail between deep and superficial veins), anal canal (hemorrhoids), esophagus (varices)
Substances enter and leave capillaries by three basic mechanisms:
- Diffusion: movement down concentration gradient (slow)
- O2 and CO2 diffusion
- Brain:
- most areas have continuous capillaries (prevents crossing BBB)
- certain parts lack BBB (hypothalamus, pineal gland)
- Transcytosis: small quantity of material crosses capillary walls (very slow)
- via both endo or exocytosis
- larger, lipid insoluble molecules (Ab’s such as IgG, insulin)
- Bulk flow: passive process by which large amount of fluid moves into and out of capillaries rapidly
- pressure driven
Bulk flow (pressure driven)
- Filtration: from blood to interstitial
- pressure driven by blood hydrostatic pressure (BHP) and interstitial fluid osmotic pressure (IFOP)
- BHP+IFOP
- Reabsorption: from interstitial to blood
- pressure driven by blood colloid osmotic pressure (albumin)
- BCOP+IFHP (interstitial fluid hydrostatic pressure; near 0mmHg unless pathology)
- Net filtration pressure (NFP)
- measured on the arterial AND venous end of the capillary (2 separate measurements)
- difference between the filtration (positive NFP=net filtration) and reabsorption (negative NFP=net reabsorption)
- NFP=(BHP+IFOP)-(BCOP+IFHP)
- Starling’s law of the capillaries: volume filtered is near volume reabsorbed
Lymphatic drainage (picture):
-
Right lymphatic duct empties into blood at the junction of the right internal jugular vein and the right subclavian vein; drains:
- right side of head and neck
- portion of right thorax
- right arm
-
Thoracic duct (left) empties into blood at the junction of the left internal jugular vein and left subclavian vein; drains:
- left side of head and neck
- left side of thorax
- left arm
- lower portion of the body
Tissues without lymphatic drainage:
- superficial skin
- CNS: uses CSF instead
- Endomysium
- Bones
Virchow’s node
left supraclavicular lymph node is highly suspicious for metastatic cancer from abdomen, pelvis, or left side thorax (these areas of the body drain into the left thoracic duct)
Virchow’s node, a left supraclavicular lymph node, was first described by Virchow as a sign of metastatic malignancy mainly from gastric cancer. The term “Troisier’s sign” describes an enlarged palpable hard left supraclavicular node following Troisier’s work, which is now sometimes used interchangeably with Virchow’s node.
Compliance
aka distensibility
greater compliance minimizes increased resistance (and BP)
arteries allow for higher pressure changes
veins allow for more volume changes
Elasticity
ability of vessel wall to stretch and recoil
arteries have more elastic fibers (internal and external elastic lamina)
Hydrostatic pressure
“intravascular pressure”
pressure generated by the blood on the vessel walls
Radial pressure
the pressure exerted across the walls of the vessels
the difference between the intravascular pressure and the extravascular pressure
Flow
units of volume per (unit of time)
e.g. mL/min
Q= (pressure difference)/resistance
Velocity
units of distance per (unit of time)
e.g. cm/min
Cross sectional area
units of [total surface area] of like vessels
the given area the blood flows through
Cross sectional area is ______ proportional to velocity of flow.
inversely
velocity of flow is slowest in capillaries
velocity of flow is fastest in large vessels
v = F/A relationships
v: velocity
F: flow
A: surface area
There must be a ______ between pressure 1 (initial pressure) and pressure 2 (terminal pressure) for there to be any flow.
difference
What helps aid venous return to the heart?
pressure generated by left ventricular systole
extravascular pressure
skeletal muscles (fights gravity)
respiratory pump (fights gravity)
Poiseuille’s Equation
Q = 𝝅Pr4/8nl relationships
Q: volumetric flow
P: ΔP
r: radius of vessel
n: viscosity
l: length of vessel
Increased volume flow results in ______ velocity.
decreased
think finger over the end of the water hose
Respiratory “pump”
During inhalation, contraction of the diaphragm (moves downward)
abdominal veins are compressed pushing greater volume of blood toward the heart
During exhalation, valves prevent backflow out of the thorax
What fights venous return to the heart?
increased right sided heart pressure
tricuspid valve failure>increased RA pressure>blood backs up
gravity (countered by the skeletal and resp. “pumps”)
Intrinsic control of blood pressure and flow:
- autoregulation: most tissues, blood flow is adjusted by the metabolic activity
- myogenic: when arterial BP changes, the arterioles can adjust to keep a relatively constant flow regardless of systemic pressure
- endothelium mediated:
- prostacyclin: dilates smooth muscle (not sure what triggers release however could be shear force); also prevents PLT adherence to endothelium
- NO: dilates smooth muscle (released when stimulated by Ach, shear stress, other vasodilating substances)
- endothelin: constricts smooth muscle (triggered by various hormones; thought to be involved in pathology such as atherosclerosis)
Extrinsic control of blood pressure and flow:
- primary function is to regulate arterial BP by altering SVR
- several interconnected negative feedback systems
- HR, SV, SVR, blood volume
- some are rapid control (orthostatic)
- others provide long term control
- Cardiovascular center: regulates HR, contractility, and vessel diameter
- located in medulla
- composed of:
- cardio-stimulatory center
- cardio-inhibitory
- vasomotor consists of:
- vasodilator/constrictor center
- sensory input from: proprioceptors, baroreceptors, chemoreceptors
- output:
- sympathetic:
- cardiac accelerator nerves
- vascular tone
- parasympathetic via vagal nerves
- sympathetic:
- Higher brain centers provide sensory input to CV center
- cortex, limbic system, hypothalamus
- neural regulation of BP
- baroreceptor and chemoreceptor reflexes>these work quickly
Chemoreceptor
- Chemoreceptor reflex
- carotid and aortic bodies
- detect changes in blood concentration of O2 (hypoxia), CO2 (hypercapnic), and H+ (acidosis)
- CV center increases sympathetic stimulation to arterioles and veins causing vasoconstriction (increased BP)
Baroreceptor
- carotid sinus reflex
- Carotid sinus: outpouching of R/L internal carotid arteries; just above the branching
- CNIX (sensory portion)
- aortic reflex
- ascending and arch of aorta
- CNX sensory portion
Neurohumoral regulation works ______ vs. baro/chemoreceptors which work ______.
slowly
quickly
Epinephrine
increased HR: beta 1
vasoconstriction: arteries and veins (alphas)
vasodilation: skeletal muscle and liver tissues (beta 2)
can serve a neurotransmitter or hormone
secreted from adrenal medulla from fight or flight only
Norepinephrine
increased HR: beta 1
vasoconstriction: arteries and veins (alphas)
continuously released in low levels= vascular tone
made mostly in neurons and released as overflow
small amounts made in adrenal medulla from fight or flight
Blood pressure:
progressively drops as you get further away from LV
normal pulse pressure: 40-60
normal MAP: 70-100
measurement: bare arm, pump 30mmHg (usually) above normal SBP for PT
CVP waveforme
“a” waves will disappear in A fib
large “a” wave: pulm. HTN, tricuspid valve stenosis
large “v” wave in tricuspid regurgitation
