|
1997-98 -- 05-06 Academic Years Human Biology |
28 April 1998 Tynetta Stanley [Home Schooling Mother]
She spoke about the meaning of the word physic: a medicine
or remedy,
especially a laxative or cathartic which is completely different
from the
meaning of physics: science dealing with the properties,
changes,
interaction, etc of matter and energy. The two words do come from
the same
Greek root
Also, she spoke of folk remedies for colds and fever, such as the oat and bread water, citrus fruits, and the famous sassafras tea.
Comments by Porter Johnson:
while you are within your constitutional rights in waiving immunization
for
childhood diseases, it is not a good idea to avoid them, or to try to
treat
serious diseases [Hepatitis C, Meningitis, Mumps etc] with folk
remedies. Also,
I read recently in Discover Magazine that half of the people
who have
ever been born died of Malaria -- most before the age of 5. Modern
standards of
sanitation, refrigeration, transport and storage of food, and
agricultural
technology are probably as important as medical miracles in increasing
the
average lifespan.
23 November 1999: Melinda Ross [Hefran Elementary School]
Brain Power: Melinda showed us two lists with letters under
them. We were then challenged to remember them. We were also asked
why we thought we remembered each list, having to do with how we can
remember things. We were then asked to move our right foot in a
clockwise
motion, and simultaneously to move our right hand in a clockwise
motion.
We were then asked to change the motion to up and down, and we became
confused. We were then asked to move our left foot in a
counter-clockwise
motion while our right foot went clockwise, and to move our right hand
in
a clockwise motion.
15 February 2000: Pam Moy (Morgan Park HS)
(handout) had us do several simple tasks such as tie your shoe,
write your name (cursive), zip up a zipper or button a button,
crack open a peanut and eat it. And we timed ourselves (in
seconds). The catch was that we had to do each task twice;
once with our thumbs immobilized (by taping to side of
hand), and once without. We found most tasks were slower
by a factor of 2 to 5 times with thumbs immobilized!
Connected to evolution?! Makes the point simply and
effectively. Elegant!
28 March 2000: Val Williams (Bass School)
showed us the effect
of music on doing delicate tasks. As an example, a task
was picking plastic "bones" out of recesses in a "human
body" with tweezers. Val's subject, a 10-12 year old boy,
wore headphones, and we compared his efficiency at this
task with different kinds of music fed into the
headphones. We saw that the efficiency appeared to be
affected by the type of music. And finally, Val and his
assistant did a "rap" song on Evolution, which most seemed
to enjoy. Interesting stuff, Val!
02 May 2000: Pam Moy (Morgan Park HS)
passed out an article on "How Females Choose Their Mates,"
Scientific American (April 1998) [see the website
http://www.sciam.com] which
she uses for AP Biology class at prom time. An interesting
article, and a neat idea!
24 October 2000: Karlene Joseph (Lane Tech HS)
did Out of Order Hands with us. She had us cross our wrists and
fingers. A
partner then pointed to a finger, and we tried to move it.
There is confusion in our mind because of the "inversion"
of limbs, and it's hard to figure out which one to move.
In order to move the chosen finger, you must think about
it first, and then move the finger you think is on the
opposite side of the one pointed at. Then it works!
Next, she had us stretch out both arms, make fists, and press fists together as hard as possible. A partner then presses sideways on both fists with just his index fingers, and can push our fists apart! Why does this happen? Try it and see!
Last, Karlene showed us the glued finger. We placed our hand on the desk with the first 2 joints of the middle finger tucked under our hand and pressed against the desk surface. Now - she told us to try to lift the other three fingers of that hand. But our ring finger would not move! Try it! The bone and tissue structure of the middle and ring finger are connected, so if one cannot be moved, neither can the other. How could you verify this?
24 October 2000: Zoris Soderberg (Webster School)
shared the lesson she gives her students about the heart. A resource is
American Heart Association
National Center
7320 Greenville Ave
Dallas, TX 75231
http://www.americanheart.org/
This is a lesson that "fits" in around Valentine's Day (14 February). She gives facts about the heart, and even brings in a real heart for kids to see - beef or pork - and cooks it for them. Now for us, she first had us feel our pulse, at the wrist, or in neck under side of chin, or back of the leg by Achilles tendon, or in chest. Next, we listened to our hearts with a stethoscope. Zoris got her stethoscope free, from the above address! Lastly, using an electronic device, Pocket Dop II, which amplifies sound, all of us could hear clearly the sound of a volunteer's heartbeat! Cool!
24 October 2000: Val Williams (Bass School)
appropriately near Halloween season, set up a full-size plastic replica
of a
human skeleton, and posed the question, "Why do we have a
skeleton?" Ideas we put forth: support; shape; protection;
movement; makes blood cells. Val pointed out that 10%
of
body weight lies in the skeleton. He brings math into the
lesson by asking students to calculate the weight of their
skeleton from their actual body weight. He then used lyrics from the
old song: "The toe bone connected to the foot bone, the
foot bone connected to the..." to get kids thinking about
how the bones of the skeleton are actually connected
together. Next, he projected an image of the skeleton onto
the ceiling to get our attention, and played
Dem Bones, Dem Bones, Dem Dry Bones ...
illustrating the connections of the song by pointing to them on the plastic skeleton. This was really fun, as well as informative!
07 November 2000: Marva Anyanwu (Green School)
posed the problem:
What effects does exercise have on respiration? In respiration
Food + O2 ---> CO2 + H2O + energy
which takes place inside cells in mitochondria. Breathing is moving air in and out of the lungs, but respiration is as described in the prior sentence. Marva asked groups of us to do an experiment. We used a bromothymol blue (BTB) indicator to measure respiration rate, and we predicted that exercise would increase the rate that BTB would change its color in response to increased respiration.
Each group had two clear plastic cups containing BTB which was initially blue. A straw was placed in each cup. The idea was that as a volunteer exhaled through the straw and into the liquid, starting at time zero, CO2 was added to the liquid (from the breath of the volunteer), and the pH would decrease (because of formation of carbonic acid, H2CO3), so the color would change from blue to green to yellow. Two trials were run; one with the volunteer at rest, the other after the volunteer ran in place for 3 minutes. The experiment worked pretty much as expected, but there were complicating factors.
We found that CO2 in the the room air caused the BTB solution to turn yellow on its own, without exhalation. As we exercised, we produced more CO2 in each breath, which caused the BTB to turn yellow in a shorter time. But - with more breaths in a given time, wouldn't more CO2 be expected after exercise? Ken Schug suggested adding water from a closed container just before the test, and adding the BTB just before the test. Or, put a cover over the container to slow (but not eliminate) CO2 dissolution. For additional details see the website http://www.sciencebuddies.org/mentoring/project_ideas/Zoo_p013.shtml.
Marva showed us how to put chemistry to work to measure biological a biological process. Beautiful stuff, Marva! Thanks!
20 November 2001:
Frana Allen (Skinner School, grades 1-5) The Nose
Everybody's nose may look different from the outside, but all noses
have essentially the same function and internal structure.
Sat. September 29, 2001 - Sun. January 6, 2002: Grossology. In the name of science we’re inviting you to burp loudly, explore the colorful world of vomit, and yucky body parts—really. In this exhibit, walk into the book by author Sylvia Branzei, and get up close and personal with the functions of your body and its orifices, for example the nose. Walk in, sniff around. Find out what it makes and what you do with it. Animated activity stations bring your bodily functions to life, offer you the chance to participate in them, and then present the science behind it. Source http://www.grossology.org/. Comment by Porter Johnson: You may perhaps also enjoy their (permanent) butterfly exhibit: http://www.chias.org/online/thebutterflylab/index.htm.
This subject is sure to be fascinating for our students!
19 February 2002: Therese Donatello
(St Edwards School)
Handout: Our Bodies
Therese began by talking about the human skeleton, and its
various types
of joints. We first made a model for a "hinge joint", (such as
the ankle) making the
pieces by cutting an index card, and attaching them with a metal
fastener, as
shown:
______This represents the fairly rigid structure provided by bones. Now we attach the more flexible "muscles", which consist of two strands of yarn passing through the holes, and attached at the joint with tape:
| |
|o o | < -- holes
| |
| |
| |
| |
|______|__________
| | |
X= fastener-->| X | |
|______|__________|
______We then extended the process by attaching a knee joint and thigh muscles:
| |
|o o |
|. . |
. |. . |
. = yarn -- > |. . | < -- yarn
. |. . |
|______|__________
|. . | |
H = tape -- > |H X H | |
|______|__________|
______We then made a model of the "pivot joint" in the elbow, which allows you to turn your hand from "palm up" to "palm down" positions, and back. We rolled (xerographic) white paper sheets into cylinders/tubes about 2-3 cm [1 inch] in diameter, in order to construct two long "bones", the radius and ulna. We punched holes in them and taped on yarn "muscles" in the lower arm. Similarly, we made a third bone, the humerus, for the upper arm, and attached a muscle to it. These muscles are held on their respective bones by tendons, for which we used tape, as before. Then we used yarn to make "ligaments" that attach each of the two bottom bones to the top bone [but not to each other!] at the elbow joint.
|o o |
|. . | <-- thigh bone and muscles
|. . |
|. . |
|______|
______ < -- knee fastener
|H H | (a second hinge joint)
|o o |
|. . |
|. . |
|. . |
|. . |
|______|__________
|. . | |
|H X H | |
|______|__________|
She also described making a "ball and socket" joint, such as found in the hips and shoulders, using lengths of paper and a small cup.
For additional information on of making models of joints, see the website Building a Model Arm: http://www.ehow.com/how_5147963_build-model-arm.html, which has been developed in the Iowa State University Science Extension Program, Science is Here: http://www.extension.iastate.edu/e-set/science_is_here/front~1.html
A pretty, phenomenological lesson, Therese!
02 April 2002: Earl Zwicker (IIT Physics) -- Getting a Full
Night's Sleep
Earl passed out copies of a newspaper article describing a study
published
in February 2002 in the Archives of General Psychiatry showing
a
correlation between the amount of sleep per night versus
longevity.
Specifically, sleeping more than 8 hours per night was shown to
correlate with
high mortality. Here is the abstract of that article, take from
the
website http://archpsyc.ama-assn.org/cgi/content/full/59/2/112?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=sleep+vs+mortality&searchid=1088441576152_874&stored_search=&FIRSTINDEX=0&journalcode=archpsyc:
Mortality Associated With Sleep Duration and Insomnia, Daniel F. Kripke, MD; Lawrence Garfinkel, MA; Deborah L.Wingard, PhD; Melville R. Klauber, PhD; Matthew R. Marler, PhD, Arch Gen Psychiatry. 2002;59:131-136We generally discussed whether the "Science Lite" presentation of this and other studies in the media are simplistic. This apparent correlation may be an effect, rather than a cause, of poor health, and it would be hard to separate the effects.Background Patients often complain about insufficient sleep or chronic insomnia in the belief that they need 8 hours of sleep. Treatment strategies may be guided by what sleep durations predict optimal survival and whether insomnia might signal mortality risks.
Methods In 1982, the Cancer Prevention Study II of the American Cancer Society asked participants about their sleep duration and frequency of insomnia. Cox proportional hazards survival models were computed to determine whether sleep duration or frequency of insomnia was associated with excess mortality up to 1988, controlling simultaneously for demographics, habits, health factors, and use of various medications.
Results Participants were more than 1.1 million men and women from 30 to 102 years of age. The best survival was found among those who slept 7 hours per night. Participants who reported sleeping 8 hours or more experienced significantly increased mortality hazard, as did those who slept 6 hours or less. The increased risk exceeded 15% for those reporting more than 8.5 hours sleep or less than 3.5 or 4.5 hours. In contrast, reports of "insomnia" were not associated with excess mortality hazard. As previously described, prescription sleeping pill use was associated with significantly increased mortality after control for reported sleep durations and insomnia.
Conclusions Patients can be reassured that short sleep and insomnia seem associated with little risk distinct from comorbidities. Slight risks associated with 8 or more hours of sleep and sleeping pill use need further study. Causality is unproven.
24 September 2002:
Marva Anyanwu [Worley-Green Elementary School, K-8]
Fingerprints
[handout]
One handout described the basic fingerprint patterns: whorl,
arches,
loop, and composite, as shown on the website
http://www.policensw.com/info/fingerprints/finger07.html,
whereas the other involved a study of the characteristics of
fingerprints and
skin, similar to the website
http://safety-identification-products.com/fingerprint-information.html.
Marva challenged us to explain what fingerprints have in
common with tire treads.
10 December 2002:
Ann Parham [Carver School]
Measuring Stress
Ann described an activity that involved measuring stress
as a
function of level of activity, which involves using home-made stethoscopes,
which are made from toilet paper tubes or the equivalent, with a
diaphragm made
by placing a rubber balloon over one end. The balloon is held
against the
subject's chest, and the doctor's ear is placed at the other, open, end
of the
tube. Pulse rates for the subject were measured following two minutes
of
inactivity, as well as following periods of increasingly more intense
activity
--- walking, jogging, doing jumping jacks, and climbing
stairs.
Several of us made the stethoscopes, but only a few could hear
heartbeats
because of background noise in the room. The complete activity
protocol
was passed out on instruction sheets, as well as a table of typical
student
results.
Good work, Ann!
23 September 2003: Research or Rsceearch?
The paomnnehil pweor of the hmuan mnid.
Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in
waht
oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the
frist and
lsat ltteer be at the rghit pclae.
The rset can be a total mses and you can sitll raed it wouthit
porbelm.
Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef,
but the
wrod as a wlohe. Amzanig huh?
--- [Courtesy of Rudy Keil]:
21 October 2003:
Barbara Lorde [Attucks
School] Make Your Own Lungs
Barbara started with a prelude of how
she creates interest in her classroom using a phenomenological
approach, e.g. by
holding up an envelope and asking questions about it (or its contents).
[Many of us were
surprised to hear that the secret of self-seal envelopes is that the
surface of the
flap is coated with thousands of tiny bubbles. When the flap is
pushed
against the envelope, the bubbles burst, releasing the glue and sealing
the
envelope.] Barbara next asked us about breathing problems
we might have.
We then made our own working model of lungs, using a clear plastic
drinking cup for the
thorax, a plastic straw for the trachea (inserted through a hole in the
bottom of the
cup), small balloons for lungs (attached to the trachea on the inside
of the
cup), and a piece of rubber (cut from larger balloon) stretched
across the top of the cup for the diaphragm. The lungs could be made to
expand and
contract in several ways:
Cellophane tape was used to seal the various openings. Several of us made models with two lungs (and two tracheæ). For more information see A Model of Your Lungs: http://www.sciencenetlinks.com/lessons.cfm?DocID=245.
A great way for students to learn. Thanks, Barbara!
04 November 2003:
Erma Lee [Williams] Salad Advice
Erma Lee (welcome back; we missed you!) then fed both our bodies
and minds with an
activity based on SALAD ADVICE that she recently
received from an expert on human nutrition.
She provided the following salad ingredients: lettuce, three kinds of
dressing, hard
boiled eggs, cucumber, tomato, shredded cheese, bacon bits, croutons,
sunflower seeds,
carrots and asked us to make healthy salads with an estimate of total
calories.
While eating our salads we discussed such varied nutrition topics as
Holiday
Weight Gain, number of calories in a stick of (sugared) chewing
gum, how to reduce
sugar craving, along with good and bad cholesterol. Nice tasteful way
to end the meeting.
Thanks Erma, for your infectious enthusiasm and helping think more
about what we
put in our mouths at meal times (and in between).
23 March 2004:
Don Kanner [Lane Tech HS,
Physics]
Acid Reflux
Don [a visitor from the Math-Physics SMILE class] spoke
about his
recent diagnosis for this condition at Northwestern Memorial
Hospital.
The acid reflux condition, more properly described as esophageal
reflux,
involves leakage of stomach acid back into the esophagus, and can cause
severe
damage to the esophagus. Don's physician does not agree
with the
commonly prescribed anti-acid prescription for reflux disease. He
said,
instead, that people who have heartburn should eat at least 2 - 3
hours
before bedtime. Snacks just before bedtime stimulate the
production of
stomach acid, which has a tendency to "roll down" into the esophagus
when you lie down in bed.
Thanks for the tip; we feel better already, Don!
23 March 2004:
Barbara Lorde [Attucks
School]
The Muscular-Skeletal Systems of Humans
Barbara began this Biology
lesson by having us make various motions with our bodies, paying
special
attention to changes in the positions of vertebrae in our backs.
We made
use of a full-size plastic model of the human skeleton, obtained from a
Biology
Laboratory at IIT, to illustrate the spinal column, the spinal
cord, and the
function of the arm.
Barbara then showed us how to make a model of our spinal system, using a shoe string to represent the spinal cord, and sewing thread spools to represent vertebrae. We also used wooden dowels and rubber bands to make models of the upper arm, including the humerus, radius, ulna, and the elbow joint. The models were extremely instructive!
So that's how we're put together. Very nice, Barbara!
04 May 2004:
Ed Scanlon [Morgan Park HS,
biology]
A Comparison of Hominoid Skulls
Ed passed out several pictures of
hominoid skulls (frontal, profile, and basilar views for the skulls of
Australopithecus africanus, Homo habilis, Homo erectus, Neanderthal,
and Homo
sapiens). Ed obtained the information, along with
explanatory materials,
from Science Kit / Boreal Laboratories: http://sciencekit.com/,
kit number 46973: Hominid Skull Comparison: An
Investigation of
Hominid Evolution. He also distributed a data chart for their
classification, which
contained the following entries:
Each group got one set of drawings (numbered but not named), on which measurements with protractors and metric rules could be made. We discussed common features of the skulls, as well as features most useful in distinguishing the skulls. The goal was to analyze various features and determine their importance in deciphering evolutionary relationships, by measuring and describing various hominoid skulls. Although humans and other primates have many similarities, humans did not evolve from apes. The evidence seems to point to a common ancestor for primates.
Which of these skulls was human?? Very nice, Ed!
28 September 2004: Earl Zwicker called attention to an article by Ronald Kotulak, science reporter for the Chicago Tribune [http://www.chicagotribune.com/], entitled Tiny Battlefield in the War on Disease [http://www.aegis.com/news/ct/2004/CT040907.html] -- which appeared on 14 September 2004. The idea is that, using the techniques of nano-technology, it may be possible to coat tiny nanoparticles of gold with bits of DNA or antibodies that serve as sensors, to identify and destroy cancer cells in the body.
23 November 2004:
Brenda Daniel [Fuller Elementary
School]
The Human Body,
Particularly the Skeleton (Handout)
Brenda passed around a handout describing the Foss Human
Body Module, which was developed at the University of
California, Berkeley and published by Delta Education.
This handout contained sketches of the human skeleton entitled COUNTING
BONES, BONE NAMES, MUSCLE NAMES, and MR. BONES A-C.
Brenda discussed the human skeleton, using X- rays as an example of how to view the skeleton. As an exercise we then taped our fingers together, and then attempted to do normal activities that require the use of our hands. We learned -- firsthand -- of the importance of independent use of all the digits in our fingers. Amazing and informative! Thanks, Brenda!
14 December 2004:
Ron Tuinstra [Illiana Christian HS, chemistry]
Human response times
Ron brought this back from a National Association of Biology
Teachers
convention. It is fast, fun, and yields quantitative data. The
detailed protocol is in the handout. Briefly, a vertical meter stick is
dropped
by one member of a two person team through a space between the
other (catcher) person's thumb and index finger. The "catcher"
grabs the stick by closing his/her thumb and index finger on it.
The distance the stick
falls between the start signal and the catching can then be
easily measured by subtracting the "starting position (which we set at
10 cm, i.e., the initial thumb and index finger position was
always put 10 cm from
the bottom end of the stick) from the position on the stick at which
the grab stopped
the stick. We tried visual, auditory, and tactile signals to alert the catcher
of the simultaneous release of the stick. Note that the data are
collected as distance along the meter
stick (i.e., the distance the meter stick falls from the initial signal
until
the stick is grabbed), which we use as a measure of time. The standard
formula
obtained from Newton's Laws of motion allows a conversion from distance
to
response time.
We predicted before we did the experiment that the response time would be fastest for the visual start signal and slowest for the tactile start signal (with the auditory signal intermediate). This is based on our idea that receipt of the signal should be fastest for light, next fastest for sound, and slowest for transmission along the nerves in the arm from the hand to the brain (for tactile). For all subjects all response times were in the 140 - 300 msec range, but with different averages for males and females. Here are the data:
| Sex | Number | Visual | Auditory | Tactile |
| Female | 2 | 210 msec | 200 msec | 235 msec |
| Male | 4 | 215 msec | 305 msec | 186 msec |
| Sex | Visual | Auditory | Tactile |
| Boys | 184 msec | 230 msec | 216 msec |
| Girls | 192 msec | 235 msec | 205 msec |
Within experimental error there seemed to be no M/F differences, but visual response was faster for the younger subjects than for us older folks! Ron said that in his experience for his students, usually V is fastest, then T, then A.
Ron said that student age and sex would be appropriate parameters for examining average response times. Ed Scanlon suggested left hand versus right hand (or really strong versus weak hand) as another interesting parameter to test.
And Ron, thanks, too, for another great miniteach!
29 March 2005: Roy Coleman [Morgan Park HS,
physics]
Foot - Hand Rotation
Roy asked us to move our right foot in a clockwise circle.
Then, simultaneously try to
write a "6" in the air. Astonishingly, as we wrote the 6
in the air, the right foot reversed its clockwise motion to
counterclockwise. How come? Thanks, Roy!
13 December 2005:
Ron Tuinstra [Illiana Christian
HS]
Virtual Cadaver
Using the projector attached to his laptop computer, Ron
ran a graphics package that does virtual dissections to
display images involving human anatomy. The graphics were
developed from actual dissections of the cadaver of a 68 year old male
who died of
a heart attack -- and a prototype female is under preparation. The
software
package is being marketed mostly for college classes, but Ron
makes very good use of
it for his students. Various functions permit manipulations such as 90o
-
180o - 270o rotations, zoom in and zoom out,
etc. Ron then gave us a more detailed demo using the tissue
selecting function to examine the skeleton. Bones can be identified, or
can be added to or removed from the image. This Virtual
Dissector software package can be ordered for about $500 (site
licenses are
available) for installation from the Touch of Life Technologies
website http://www.toltech.net/.
Ron also ran the Virtual Moon Atlas package, which may
be obtained
free from the NASA website: [http://www.ap-i.net/avl/en/download].
The planetary configuration
could be recovered for any date. Ron displayed them for 29
February
1940, Porter's official non-birthday. The heavens were
portentous on that date!
What powerful visualization tools for understanding human anatomy, as well as for astronomy! Thanks, Ron.
During a lull in the activities during setup, Porter described an actual conversation between a Biologist (B) and a Physicist (P).
P: Please tell me something about the human brain.
B: Well, actually there are several brains functioning more or less independently in the human body, with linkages.
P: Wait, wait! You already told me too much!
Good stuff, Karlene!
07 March 2006: Earl Zwicker (IIT
Physics)
Mr Angry is on the left, and Mrs Calm is on the right
Earl had gotten an e-mail from Rudy Keil, including a
remarkable
image, which is located at The Mindreader website http://www.ianrowland.com/MiscPages/Mrangryandmrscalm.html..
There
are two images of a face next to each other, one with a calm look and
one
with an angry look. The two images seem to switch left to
right depending on whether they are viewed from close in
(about 1 foot away) or far away (about 8 feet). It works
completely!! But no one knew the reason for this! We will
have to look for one!! One way to investigate it would be to
try to find out if there is a consistent distance (for the
members for the class) at which the transition occurs. We
tried this. Fred tried it and the transition (where the
images looked roughly the same) occurred at a distance of
about 6 floor tile widths and the switch was complete at about 10
tiles. Don tried it and got 8 and 10 for the same figures.
Walter got 8 and 10; Ed got 6 and 9. Fairly consistent
results which did not seem to depend upon whether or not the
observer was wearing glasses. For additional discussion see the
website
http://cvcl.mit.edu/gallery.htm#hsflsf,
from which the following has been excerpted:
"This impressive illusion created by Dr. Aude Oliva and Dr. Philippe G. Schyns, illustrates the ability of the visual system to separate information coming from different spatial frequency channels. In the right image, high Spatial Frequencies (HSF) represent a woman with a neutral facial expression, mixed with the low spatial frequency (LSF) information from the face of an angry man. On the left, the face of the angry man is represented in fine details whereas the underlying female face is made of blur only."Thanks, Earl!
18 April 2006:
Ron Tuinstra (Illiana Christian HS, Biology
)
HDN: Hemolytic Disease of the Newborn (handout)
HDN is caused by an attack on the baby's
red blood cells by the mother's immune system (either
newborn or even in utero). The mother is exposed to an
antigen [antigen: A substance that when introduced into the
body stimulates the production of an antibody. For details see
the website
http://www.answers.com/topic/antigen]
foreign to her, which comes from the
baby and is provided through genes from the father. The disease
involves the Rh
factor, which is present on the surface of the red blood cells of
most
people -- for details
see the website http://www.medterms.com/script/main/art.asp?articlekey=5351.
The most common occurrence involves an Rh+ father
(and baby) and an Rh-
mother.
The most common source of the antigens arises after rupture and
delivery of the placenta (which has the same Rh factor as the
baby's tissue).
Abortion or miscarriage can also lead to problems. Normally 5-10 mL
of baby's blood is taken up by the mother
through the uterus. The first baby is usually not affected, because its
birth
produces
the initial exposure. But this exposure will cause anti-Rh
antibodies to be formed in the mother, which can cause
HDN in subsequent pregnancies with an Rh+ baby.
An antibody titer is a test to measure the presence in the blood (and the amount) of antibodies against a particular type of tissue, cell, or substance. For details see the website http://health.allrefer.com/health/antibody-titer-info.html. The titer of an Rh- mother's anti-Rh antibodies is carefully monitored. If that titer is increasing, it indicates that the baby is probably Rh+, and intervention (including complete transfusion of the fetus with Rh- blood or early delivery) is considered.
If the baby's blood test shows HDN, hemolysis [hemolysis: the breaking open of red blood cells and the release of hemoglobin into the surrounding fluid (plasma, in vivo). For details see http://en.wikipedia.org/wiki/Hemolysis] of red cells causes a breakdown of Hemoglobin into Bilirubin [for details see http://en.wikipedia.org/wiki/Bilirubin], which can be removed by the mother's liver while the baby is in utero. However, the baby's own liver usually doesn't work so well at first, and the baby will get jaundiced from the Bilirubin. UV light treatments [for details see http://laser.physics.sunysb.edu/~wise/wise187/2001/reports/sofya/report.html] are usually effective in breaking down the baby's Bilirubin -- this is the common first treatment. In extreme cases the Rh+ baby is transfused completely with Rh-- blood to get rid of the Rh antigen. It is dangerous because the anticoagulant added to the transfused blood chelates calcium [chelation: The process of reversible binding of a ligand to a metal ion, forming a metal complex.. For details see http://en.wikipedia.org/wiki/Chelation], so that calcium levels in the baby's blood have to be monitored carefully. The hemolysis also releases K+, which is dangerous because high K+ levels can lead to cardiac arrest [see hyperkalemia: http://www.nlm.nih.gov/medlineplus/ency/article/001179.htm].
Rhogam [Rh0 immunoglobulin -- for details see the website http://www.medterms.com/script/main/art.asp?articlekey=11961 -- is given to mothers at risk. Rhogam is an antibody to the Rh+ antigen. After the mother delivers the first baby, she immediately gets a Rhogam injection. The Rh+ antibody binds to the baby's red blood cells, initiates their clearance from the mother, and misleads the mother's system into believing that there are no Rh+ antigens in her body. Subsequently, she stops making antibodies to the Rh+ antigen. This treatment was found to be about 98 % effective. It is felt that, for the few mothers for whom this didn't work, violent kicks by the baby during the last 8 weeks of pregnancy could have ruptured the placenta and caused baby's blood to mix with the mother's circulation at an earlier stage. Thus Rhogam is given, starting in the last two months of pregnancy. The effectiveness of the treatment has increased to about 99.5 %!
A beautifully lucid description of the science behind life-saving medical advances! Thanks, Ron.