106: BIM BIOTRANSPORT PHENOMENA
Instructor: Professor Kent Leach
Office: 3321 GBSF
E-mail: [e-mail]
Office hours: Tues 4-5 pm or by appt.
Teaching assistant: Allison Hoch
Grader: Alan Man
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How do surveyed students spend their time?
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http://www.universityofcalifornia.edu/studentsurvey
How do surveyed students spend their time?
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http://www.universityofcalifornia.edu/studentsurvey
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How to excel in BIM 106? 9 simple rules
1. Study.
2. Always come to class (and take notes).
3. Study!
4. Ask ques9ons of your instructor and TAs
U9lize oce hours
5. Study!
6. Understand the HW you turn in.
HW should be suciently detailed and legible.
7. Study!
8. Turn things in ON TIME.
9. STUDY!!
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RESPONSIBILITY OF THE ENGINEER
President Herbert Hoover (1932)
hooverassociation.org
Biomedical engineers have the burden of
being good engineers first, but also learning and
applying these principles to the human body.
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WHY STUDY BIOTRANSPORT?
1. REQUIRED
2.Characterize physiological and cellular processes
3.Design and operate various devices
4.Develop new therapies
DEFINITION OF TRANSPORT PROCESSES
D
Diffusion random motion of molecules due to energy transferred by
molecular collisions. Molecules will move from areas of high
concentration to low concentration (i.e., down the concentration gradient)
as a means to establish an equilibrium.
blobs.org
Ficks 1st Law
dCi
J ix = Dij
dx
Jain and Carmeliet,
Nature (2000)
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DEFINITION OF TRANSPORT PROCESSES
Figure 1.1 500-step random
walk. The walk begins at
coordinates x = 0, y = 0 denoted
by the and ends in the upper
right hand quadrant denoted by
X. The arrow represents the
displacement.
1/ 2
rms = (< x 2 > + < y 2 >)
!
=< r 2 >1 / 2
< x2 > + < y2 >
Dij =
4t
What differences would you expect to observe
between a random walk of a molecule in a gas
and a random walk of! protein molecule in H2O?
a
DEFINITION OF TRANSPORT PROCESSES
Protein diusion within a cell (10 m) occurs in 2.5 sec, but
diusion through a 9ssue only 0.2 cm thick requires 27.7 hrs.
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DEFINITION OF TRANSPORT PROCESSES
Convection mechanism of transport resulting from bulk
motion of fluids.
Intrinsic properties of fluids:
1. Density = mass / volume
H2O=0.999 g/cm3 (15oC)
Blood = 1.06 g/cm3
Air = 1.22x10-3 g/cm3
2. Viscosity = stickiness
3. Compressibility
4. Surface tension
5. Susceptible to forces (e.g.,
gravity, pressure, shear)
DEFINITION OF TRANSPORT PROCESSES
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DEFINITION OF TRANSPORT PROCESSES
Relative importance of convection and diffusion
Given the range of length scales in biological systems (8 orders
of magnitude: Length of proteins are 10-8 m, while the length of
the body is on the order of meters), no single transport process
can function efficiently over all scales. In order to determine
the importance of convection or diffusion, we can calculate the
Peclet number (Pe)
Pe =
mass transport by convection vL
=
mass transport by diffusion
Dij
When Pe << 1, diffusion is more rapid than convection.
When Pe >> 1, convection dominates, which is essential to
transport larger molecules.
TRANSPORT BY BINDING INTERACTIONS
Reddi, J Bone Joint Surg Am (2001)
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WHERE DOES TRANSPORT OCCUR?
1. Within the cell
2. Between cells
HAEC
Obs
ECM
3. Throughout the body
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Figure 1.11 Simplified schematic of the blood flow
distribution throughout the body.
PHYSIOLOGICAL TRANSPORT SYSTEMS
CARDIOVASCULAR SYSTEM consists of the heart,
blood vessels, and blood
EACH HAS A DISTINCT ROLE...
Mt. Auburn Hospital
Arterial system transports blood from heart to tissues
Venous system transports blood from tissues to heart
Microcirculation vessels where solute/solvent
exchange occurs
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PHYSIOLOGICAL TRANSPORT SYSTEMS
Composed of three
layers: intima (1),
media (2), and
adventitia (3)
Various cellular
components present
such as endothelial
cells, cells,
fibroblasts,
collagen, smooth
muscle and elastin
University of Southern California School of Dentistry at
http://www.usc.edu/hsc/dental/ghisto/cv/d_1.html
Figure 1.12 Diagram of the heart showing the four
chambers, valves, and veins leading into and arteries
leading away from the heart.
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PHYSIOLOGICAL TRANSPORT SYSTEMS
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TIDBITS ABOUT THE CARDIOVASCULAR SYSTEM
Cardiovascular disease is the #1 killer in the Western world
(>1 MM/year; 38% of all deaths)
Volume of blood in adult (~75 kg) = 5 liters [~8% of total body weight]
More than 40 billion capillaries in the body
All tissue cells are located within 60-80 um of a capillary
Capillaries provide a surface area of 1000 mi2 for exchanges
between blood and tissue fluid
Cardiac output (CO): blood volume/min that flows from heart (SV x HR)
Stroke volume (SV): volume ejected during each heartbeat
Heart rate (HR): number of beats/minute (60-72 resting bpm)
Hematocrit: the portion of blood volume
composed of blood cells (the rest is basically
water plus plasma proteins)
For men: about 0.45
For women: about 0.4
PHYSIOLOGICAL TRANSPORT SYSTEMS
RESPIRATORY SYSTEM
consists of the nose, larynx,
trachea, lungs, capillary bed,
nervous system, diaphragm
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PHYSIOLOGICAL TRANSPORT SYSTEMS
RESPIRATORY SYSTEM consists of the nose, larynx,
trachea, lungs, capillary bed, nervous system, diaphragm
Justin Hanes, JHU
Adult lung has 300 MM
alveoli that occupy 130 m2,
the area of 2 tennis courts.
Convective transport
O2 to the larynx and the lungs
Movement of O2 through the blood to
tissues
Diffusive transport
Dissociation of O2 from RBCs (bound to
Hg) and moves into cells and tissues to
fuel the conversion of glucose to ATP
Produced CO2 diffuses from tissues into
blood
Convective transport
Movement of CO2 through the blood to
lungs for expiration
CO2 out the mouth/nose
PHYSIOLOGICAL TRANSPORT SYSTEMS
Ficks 1st Law
dCi
J ix = Dij
dx
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PHYSIOLOGICAL TRANSPORT SYSTEMS
KIDNEYS responsible for the removal of waste products
such as urea, for fluid and ion balances, and for the
regulation of blood pressure.
Diffusive transport
Solutes (H2O, urea, O2) can diffuse across
epithelial cells that line the renal tubules
Active/facilitated transport
Reabsorption of ions (Na+, K+)
NIDDK.gov
Dialysis is an example of the major
contributions of biomedical engineers to
medicine!
SOLUTE MASS BALANCE IN KIDNEY
A mass balance summarizes the overall exchange
of solutes and H2O in the kidney.
Cia RPF a Civ RPF v = Ciu Q u
where C is the concentrations of the solute in the
renal artery and vein, RPF is the rate of renal
plasma flow in the artery and vein, and could also
be called Q instead. RPFs are not equal because
some fluid is excreted in the urine. The
difference is the rate of urine formation, Q.
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OTHER SYSTEMS OF IMPORTANCE
Extracorporeal devices
Artificial liver
Artificial kidney
Heart/Lung/Blood machines
Oxygenators
Tissue engineering
Establishing a vasculature to new tissues
Encapsulating islet cells for insulin production
Drug delivery devices
Transdermal systems
Aerosolization
Encapsulation
Figure 1.21 Schematic of drug delivery to tumor cells at four different
levels: (a) the body level (~1 m), (b) the tissue level (~1 cm), (c) the
microvessel level (~0.01 cm), and (d) the cell level (~10 m). The open
circles in (a) represent solid tumors. The solid curves in (b) represent
tumor vessels. There are two concentric cylinders in (c). The inner
cylinder represents a microvessel and the outer cylinder represents the
region in tumor tissues that receives nutrients from this microvessel; (d)
represents a tumor cell with a nucleus.
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Figure 1.22 Schematic of flow circuit for extracorporeal artificial liver.
(Reprinted with permission from Ref. [24]. 2002, AAAS.)
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Homework #1
Due next Wednesday,
1/18, at the start of
class:
Q: 1.6 and 1.13
P: 1.1, 1.4, 1.15, 2.5
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