Lymphocyte
20-40% of WBCs
large round nucleus
exhibit three classes:
t cells: cell mediated immunity
b cells: antibody production
natural killer cells: on patrol
Cardiovascular System
capacitance of a blood vessel =
relationship of volume vs pressure
Veins have a higher capacitance as they are more expandable/distensable
After that first breathe, the foramen ovale closes due to a change in the relative pressure of both atria ensuring the separation of O2 rich and O2 poor blood.
Sometimes, the closure is incomplete or will take a week to several months to close. If the formaen ovale does not close, it is called a patent foramen ovale /PFO.
About 20% of adults have an incomplete closure.
Pressure (P) and Resistance (R) determines blood flow (f).
Flow is directly proportional to pressure and inversely proportional to resistance.
The pressure gradient is the difference in pressure from one end of a vessel to the other. ..think aorta to teeny capillary. The pressure gradient can be adjusted by altering cardiac output and capillary resistance.
The Fetal Heart
Tissue Perfusion The amount of blood flowing through capillary beds must be sufficient to feed adjacent cells with nutrients/O2 and remove CO2 and waste and is measure as Tissue Perfusion.
Tissue perfusion is impacted by:
cardiac output, peripheral resistance and blood pressure. Blood flow must be regulated to ensure that certain tissues receive blood when they need it perhaps at the expense of others...
We have enough blood to fill only about 25% of the vessels in our capillary beds. Here's where regulation of blood flow comes in...
Basophils
small and rare/ <1% of WBCs
release histamine (dilation) and heparin (< blood clotting)
during exercise,
cardiac output (CO) increases from resting 5.8L/min to ...
run forest run...
Locked knees? Oops, no , no muscular compression aiding venous return
Innervation by parasympathetic and
sympathetic autonomic
system via cardiac plexus
Cardiovascular center of medulla
responds to input
from baroreceptors and chemoreceptors.
2. Central Regulation: Neural
cardiovascular center of medulla exhibits:
a. cardiac center : inc/dec cardiac output via
cardioacceleratory center (sympathetic)
cardioinhibitory center (parasympathetic)
b. vasomotor center: inc/dec lumen diameter
vasoconstriction control: most peripheral
vessels vascular via NE release
vasodilation of muscle/brain vessels via
ACh release
Most arterioles exist in a state of partial constriction. Max constriction reduces lumen by half of resting diameter increasing resistance x 80.
Types of WBCs
vein types
large veins:
ex: inf vena cava
thick tunica externa/thin tunica media
lumen diameter: 2cm
medium veins:
ex: peripheral veins
thickish tunica externa/thin tunica media
lumen diameter: 2-9 mm (.2-.9cm)
venules:
ex: capillary bed
no tunica media/resemble capillaries
lumen diameter: 20 micrometers
(.02mm/.002cm)
Blood Flow to the Brain...
12% cardiac output (CO) for 2% body weight!
Feed the brain at all costs!
Control of Blood Flow
Endocrine Control of Homeostasis:
Blood Pressure/Volume
low cardiac output
indicates poor peripheral circulation
Baroreceptors
1. Autoregulation:
vasoconstiction/vasodilation
Endothelial cells in the capillaries are smushed tightly together
forming tight junctions which permits only teeny molecules, lipid-soluble molecules, and select gases to pass freely through the capillary to the brain cells.
changes...
a. foramen ovale becomes fossa ovalis
b. ductus arteriosus becomes
ligamentum arteriosum
hemorrhagic shock
its not just
about blood...
cardiac output = volume of blood pumped by the left ventricle in one minute
Stroke or TIA
Cardiovascular Pressure
types of capillaries
continuous capillaries:
most common
complete endothelium (one to several cells)
permit H2O, small solutes and lipid soluble
molecules to diffuse into interstitial fluid
prevent blood cells and plasma proteins from
exiting circulation
fenestrated capillaries:
endocrine organs, filtration areas of kidney,
absorbtive areas of intestine
exhibit pores in endothelium
permit exchange of H2O and solutes
fenestration size/permeability vary by tissue
sinusoidal capillaries:
liver, spleen, bone marrow
flattened, non-continuous epithelium with
thin/absent basement membrane
permit free exchange of H2O and larger solutes
depolarization/ contraction/ systole
repolarization / relaxation / diastole
Welcome to Dr. Kate Brilakis' Learning Portal
Homeostasis
is maintained using
information such as blood pressure and O2/CO2 levels received via chemo/baroreceptors.
aortic transection
The ductus arteriosus is a teeny blood vessel that connects the pulmonary artery to the aorta in a fetus. This vessel permits O2 rich blood bypass the pulmonary circulation, entering systemic circulation. In newborns, the ductus arteriosus closes and becomes the ligamentum arteriosum. If it does not close, it is called a patent ductus arteriosus.
The placenta secretes prostaglandins which keep the duct open in the fetus. With first breathe, the pulmonary vessels in the alveoli dilate changing the blood flow in the pulmonary circuit. Also, with the placenta no longer attached to the newborn, prostaglandin levels fall.
Leucopoiesis
Pacemaker cells are modified cardiac muscle cells that exhibit weak contractile filaments.
Blood
The Heart
capillary bed
one arteriole to dozens of capillaries to a few venules...exhibits thoroughfare channel and precapillary sphincters
permit exchanges of gasses/nutrients/wastes
more than one artery supplying blood to capillary bed = collateral arteries
two collateral arteries fusing to supply one capillary bed = arterial anastomosis
Blood clotting
Electrocardiogram = EKG/ECG
artery structure
tunica intima:
endothilium, connective tissue w/elastic fibers, elastic internal elastic membrane
tunica media:
smooth muscle with connective tissue cover, external elastic membrane
tunica externa (adventicia):
connective tissue sheath w/ collagen and elastic fibers
venous valves
made of folds in tunica intima
point in the direction of blood flow =
unidirectional
serve to compartmentalize blood and prevent
backflow
if weakened, lead to varicoceles /hemorrhoids
DVT (deep vein thrombosis/clots form =
embolism)
RBCs
btw...Low O2 stimulates erythropoietin/EPO
secretion from the kidney and for atrial natriuretic peptide (ANP) secretion from the heart.
pericardium:
1. stabilizes position of heart
2. reduces friction
contains:
1. outer fibrous pericardium
2. inner serous pericardium:
a.parietal layer
b. visceral (epicardium) layer
c. pericardial cavity with serous
fluid between a and b.
The average heart pumps 2,000 gallons of blood per day without rest and will beat over 2.5 billion times in 70 years.
Neural Control of Homeostasis: O2, CO2, pH
blood flow through the heart
ETC...
review of ABO/Rh compatibility
systemic and pulmonary circulation
Pathology:
Heart Arrhythmias:
abnormal patterns of a heart's electrical activity which
may reduce efficiency of heart
Fetal/placental circulation:
Low O2 blood flows from fetus to placenta via umbilical arteries which arise from fetal internal iliac arteries.
HIgh O2 blood flows from placenta to fetus via single umbilical vein which drains into the ductus venosus, a shunt that allows blood in the umbilical vein to bypass the fetal liver.
The ductus venosus drains into the inf. vena cava.
Resistance:
blood viscosity 5x H2O
vessel length
vessel diameter
turbulance
cardiac physiology
Blood Pressure:
Arterial pressure rises during ventricular systole and falls during ventricular diastole.
systolic/diastolic
The difference between diastolic and systolic pressure = pulse pressure
MAP = mean arterial pressure =
diastolic pressure + pulse pressure/3
So: for BP of 110/80,
MAP = 80 + (110-80)/3 = 80 + 10 = 90
MAP and pulse pressure decrease as the distance from the heart increases.
Stroke volume
More detail...
Pacemaker cells do not require stimulation...they will depolarize/initiate action potentials all by themselves.
Their membrane potential "at rest" is approx. -60mV which is unstable. (Membrane potential is the imbalance of electrical charge between the interior and exterior of the cell...as the inside of the cell becomes less negative, the potential decreases (gets more +) below the resting potential and the cell depolarizes). So, this membrane potential of the pacemaker cell that never fully "rests" is called a pacemaker potential. Pacemaker cells have channels called "funny channels" that are permeable to both Na + and K+. The K+ permeability slowly and spontaneously decreases with time causing a slow depolarization as K+ ions exit the cell. At the same time, there is a slow, continuous, spontaneous inward flow of sodium. These actions are not the result of nerve stimulation hence the term autorhythmic. The influx of Na+ exceeds the efflux of K + so there is a net + movement. As the ion concentrations of these two ions slowly depolarize the cell, it eventually reaches threshhold (-40mV) and an action potential is generated.
Why do cardiac muscle cells contract?
A muscle cell in a state of rest (resting potential) has a sarcolemma that is polarized (- inside/+outside). As the cell depolarizes due to shifting concentrations inside/outside of K+/Na+, Ca 2+ is released from the sarcolemma (and also enters the cell) and binds to troponin. Cross‐bridge binding occurs. Actin filaments slide past myosin filaments. A contraction occurs. Repolarization occurs and membrane potential returns to its original polarization. A refractory period follows. The muscle cell cannot contract again until the cell is restored to its resting potential.
anatomy of a capillary bed
vein structure
exhibit tunica externa, tunica media, tunica intima
thinner wall and larger diameter vs arteries
exposed to lower pressure
may exhibit valves
plasma proteins
Exercise
Pressures affecting blood flow:
1. Blood pressure (BP): arterial pressure measured in mmHg
BP range: 120mm at base of aorta to 35mm at start of capillary bed
2. Capillary Hydrostatic Pressure (CHP): force exerted by blood against capillary wall
CHP range: 35mm to 18mm through capillary bed
3. Venous Pressure (VP) pressure of blood in venous system.
VP range: vena cavae exit at 2mm from venule pressure of 18mm, effective pressure
of venous system = 16mm.
WBCs
Pathology:
coronary artery disease
CAD
formation of atherosclerotic plaque reduces diameter of coronary artery/reducing blood flow= coronary ischemia
reducing cardiac efficiency
angina pectoris often initial symptom
3. Central Regulation/Endocrine Function:
Pressure/volume too high
Capillary Exchange:
*H2O, ions, glucose, aa diffuse between endothelial cells or via channels in membrane
*Large H2O soluable molecules need fenestrations (kidneys, endocrine)
*Lipid soluable molelcules and O2, CO2 diffuse across plasma
(phospholipid) membrane
Neutrophils
most abundant (60%)
segmented nucleus w/2-5 lobes phagocytic first strikers that destroy bacteria by fusing engulfed cell with lysozome containing defensins
release hormones that increase permeability
of vessels and attract other WBCs
short shelf life (30 min to 10 hours)
White blood cells WBCs are also
called leucocytes.
1ml of blood exhibits 5ish x 10*6 RBCs and just 7500 WBCs.
Most WBCs are found in the lymphatic tissue or connective tissue proper.
WBCs that are in circulation are:
1. moved to the site of an infection/injury by + chemotaxis
2. sometimes capable of phagocytosis
3. capable of ameoboid movement
through endothelium into peripheral tissues via diapedesis.
Capillary Exchange:
Filtration / Reabsorbtion
to/from cells .125mm from capillary
heart rate =
heartbeats per minute
platelets
1.5-5 x 10*5/ml blood
shelf life approx 10 days
1/3 found in spleen where they are also
degraded
thrombocytopoiesis occurs via
megakaryocytes; 1 = 4000 platelets
Pressure/volume too low
Speaking of blood pressure....
Pathology:
Artificial Pacemaker
uses electrical signals to prompt the heart to beat at a normal rate. Needed to treat arrhythmias.
vascular phase > platelet phase > coagulation phase
Chemoreceptors
artery types:
elastic: closest to heart
lumen diameter 1-2.5 cm
ex: aorta
tunica media very elastic
high elastic rebound
muscular: most numerous
lumen diameter 4mm (.4cm) ex: brachial
tunica media more muscular
arterioles:smallest of arteries
lumen diameter 30 micrometers (.03mm or .003cm)
poorly formed tunica media
called resistance vessels
exhibit vasocontracition/vasodilation
...lymphatic circulation
(more about this in Section 3!)
artery vs vein
location of heart in
mediastinum of thoracic cavity
Neural Control of Homeostasis: Blood Pressure
Monocyte
2-8% of WBCs
large kidney bean shaped nucleus
become tissue macrophage after 24 hours in circ
release chemicals to attract other WBCs
Blood flow equates to cardiac output... an increase of one increases the other.
myocardium
endocardium
Eosinophils
few in number/approx 3% of WBCs
bilobed nucleus
engulf antibody identified pathogens
release cytotoxic chemicals via exocytosis (can kill large
parasites)
increase in # with allergen presence
reduce inflammation
Coagulation Phase
extrinsic pathway: damaged endothelial cells begin the cascade
intrinsic pathway: activation of proenzymes in the blood begin the cascade
Venous return aided by muscular compression and the respiratory pump
Heart rate is increased/decreased by changing the rate of depolarization in the pacemaker cells.
To decrease heart rate: ACh is released by parasympathetic neurons which alters K+ permeability of SA node cells. This delays the action potential slowing heart rate.
To increase heart rate: Sympathetic neurons release norepinephrine which opens the NA+/Ca+ channels increasing the rate of depolarization.
stroke volume =
volume of blood pumped out of the left ventricle during one contraction.
SV = EDV - ESV
veins
Pathology:
myocardial infarction
MI
heart attacks occur when a coronary vessel is blocked
commonly by plaque formation called coronary thrombus.
Diagnosis by:
pain (not always/silent killers)
ECG/blood tests for cardiac enzymes released by damaged cells
kupffer cells line the sinusoids of the liver. they are phagocytes
that serve to breakdown "used" blood cells...
Arteries gradually change as they get farther away from the heart.
capillary structure
no tunica media or tunica externa
composed of endothilium with thin basement membrane (fibrous matrix secreted by endothium)
diameter : 8 micrometers (.008mm)
(size of one red blood cell)