Download Introduction to Biomechanics for engineering students

Biomechanics, LTH, 2013
Introduction to Biomechanics for engineering
students
by
Ingrid Svensson
2013
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Biomechanics, LTH, 2013
Hello and welcome to the course in Biomechanics!
During the next seven weeks you are going to get a glimpse in how the human body works
and get an understanding and training in how this can be expressed in mechanical terms. To
get you faster into the medical sphere of concepts I have put together some pages with “An
Intense Course in Anatomy and Physiology”. You can consider these pages as a framework
for the lectures in anatomy and physiology.
The text is aimed to suit students with different native languages so some key expressions are
given both in English, Latin and Swedish.
I hope that you will find the pages interesting and that you will enjoy the course!
Sources:
Människans anatomi och fysiologi, Bertil Sonesson och Gun Sonesson, Liber 1993.
Människans fysiologi, Olav Sand, Øystein V. Sjaastad, Egil Haug, 2002.
MEDICINE Engelsk-Svensk-Engelsk Fackordbok, P. H. Collin,Norstedts, 2002.
Lund in July 2013
Ingrid
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Biomechanics, LTH, 2013
An Intense Course in Anatomy and Physiology
Physiology is in general the science of the normal function of living creatures. In this course
we will limit our self’s and concentrate on the human body. In order to try to get an overview
of how all the complicated processes interact in the human body it is very useful to divide the
processes into some main groups. The groups often used are the digestion, the respiration, the
circulation, the locomotion, the neural system, the endocrine system, the lymphatic system,
the excretion system and the sexual organs. A principal engineering sketch of how all these
groups work together is presented in figure 1.
air food
matspjälkningsapparaten –
apparatus of digestive
andningsapparaten –
apparatus of respiration
cirkulationsapparaten –
apparatus of circulation
intercellulärt vätskerum –
intercellular room for fluid
kroppscell – body cell
blod plasma – blood plasma
intracellulärt vätskerum –
intracellular room for fluid
urinvägar – paths for urine
Fig. 1. Principal sketch of the functional structure of the human body
The cell is the smallest functional unit in living structures. A human being starts his life as a
unicellular organism in the moment of fertilization when the egg and the sperm melt together.
The fertilized egg carries predisposition to all organ systems that are going to be developed in
the becoming individual in the embryonic stem cells. In the small scale, the life functions of
the cell go on in the cell organs and, in a bigger perspective, in the human body, the different
organ systems take care of this. So, both the single cell as well as the multi cellular organism,
the human being, represents life on earth. The benefit in nature in creating multi-cellular
organisms of high complexity is the possibility to get stable environments for individual cells,
homeostasis. A human being is more capable of adaptation to changes in the environment
than the individual cells are.
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As 65% of the human body consist of water a lot of the cells in the body is surrounded by
water. But, the water appears both within the cells, intracellular, and out of the cells,
extracellular, see figure 1. The extracellular fluid is found in the intercellular room and in the
blood. The composition of this fluid (e.g. the salt content, the pH factor) and its temperature
constitute the inner environment of the body and has a great importance for the possibilities of
surviving for the cell.
Some of the main organ groups will briefly be described here and the intention is to give an
overview of the subject in order to make the mechanical modelling of the biological tissues
easier further on.
The circulatory system
vener – veins
artärer – arteries
kapillärer – capillaries
hjärta - heart
Fig. 2. The circulatory system
The circulatory system is built up by the heart (cor) and a system of arteries and veins and
makes the blood circulate in the body, see figure 2. The blood vessels that carry blood from
the heart are called arteries and the ones carry blood back to the heart are called veins. The
heart works as the pump in the system and makes the blood flow through contractions that
give pressure differences. The primary issue of the circulatory system is to distribute nutritive
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substances and construction elements to the cells in the body and to carry away waste. But the
circulatory system is also responsible for heat control, it transfers pressure changes and it
distributes different signal substances that control and coordinates the function of the different
organ systems in the body.
The blood flow transports oxygen from the lungs and nutrients from the liver through the
elastic parallel-connected arteries and capillaries to the tissues. The exchange of the oxygen
for waste matter, such as carbon dioxide, takes place in the capillaries. The waste is taken
back to the lungs to be expelled (the big circulation). At the same time the blood obtains more
oxygen in the lungs to be taken out to the tissues (the small circulation, pulmonary
circulation).
So, actually, the heart works as two separate pumps and the circulation pattern is as follows:
blood returns through the veins to the right atrium of the heart; from there it is pumped by one
of the pumping functions trough the right ventricle into the pulmonary artery, and then into
the lungs. From the lungs it returns through the pulmonary veins to the left atrium of the heart
and it is pumped, by the other pump mechanism, from here through the left ventricle into the
aorta and from the aorta further on into the other arteries.
In rest, each half of the heart pumps about 5 litres of blood per minute. This corresponds to
the total volume of blood in the system. The importance of the circulatory system as a
transport system can be illustrated by the fact that unconsciousness will set in already 30-40
seconds after the heart stops to beat and there is a risk of permanent damage in the brain
tissues if the heart beat is stopped for more than about 3-4 minutes. But, the circulation of
blood to the brain has the highest priority and in a crisis, the blood flow is redirected through
changed flow resistance in other organs.
In the blood there are white corpuscles (leucocytes, leuko-white) that take part in the
immunodeficiency. Leucocytes are also present in the bone marrow, i.e. the marrow acts as a
storage space for them. The leucocytes defend the body against microorganisms through
antibodies. When the body is threatened by a serious infection, a big number of leucocytes are
released from the bone marrow and they invade the infected area. The red corpuscles
(erythrocytes) contain haemoglobin that carries oxygen to the tissues in one way and carbon
dioxide on the return. The transport capacity will of course decrease if the number of red
corpuscles is reduced from the normal value but if there are too many of them, the viscosity of
the blood increase and the heart has to work harder. Another type of blood cell is the platelet
(thrombocyte). The thrombocytes are involved in the haemostasis, i.e. the mechanisms
stopping the bleeding when blood vessels are ruptured. The thrombocytes form plugs that
mechanically stop the bleeding. But this process can also be destructive. A heart attack or a
stroke might occur if a vein or an artery is blocked by a blood clot (thrombosis). Fibrinogen
is a substance in blood plasma that produces fibrin, a protein, which helps the blood
coagulate.
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The respiratory system
näshålan - the nasal cavity
struphuvudet - the voice box
(larynx)
luftstrupe - the wind pipe
(trachea)
lungorna - the lungs
(pulmo)
Fig. 3. The respiratory system
There has to be a constant flow of oxygen into the body to supply the process of oxidation of
nutrition so energy could be released. In human the exchange between oxygen and carbon
dioxide takes place in thin tissues in the lungs. The total area of these tissues is very big,
about 75-80 m2 for a grown up. The tissues are well protected in the moist environment. It has
to be moist because the gases must be resolved in liquid if they should be able to diffuse from
blood to air in the lungs.
The respiration process takes place in the organs of respiration: the nasal cavity, the throat
(pharynx), the voice box (larynx - struphuvud), the wind pipe (trachea – luftstrupe), the
bronchi (luftrör) and the lungs (pulmo - lunga). The two lungs are situated in the chest cavity,
protected by the rib cage and supported by the diaphragm. The heart is situated between the
lungs. The right lung has three lobes, the left only two. Air goes down into the lungs through
the trachea and bronchi. The cilia (flimmerhår) at the inner walls filtrate and moisture the air
in order to protect the easily damaged mucous membranes (slemhinnor) of the alveoli. The
air passes to the alveolar sacs. The alveolar sacs are made up of clusters of alveoli like grapes
in a bunch. The gas exchange, oxygen-carbon dioxide, occurs in the blood vessels that are
wrapped around each individual alveolus. The oxygen is needed for the metabolism of the
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cells and through the respiration carbon dioxide is ventilated and balance of the pH factor is
obtained in the blood and other body fluids.
The respiratory system is also the base of the speech. Air is pressed from down under through
the narrow slit, the glottis between the cords (plica vocalis - stämband) in the voice box. A
pulsating air stream builds up in the glottis and propagates through longitudinal oscillations
into the resonance areas, i.e. the throat, the oral cavity, the nasal cavity, the sinus and the
chest, where the oscillations are filtered and amplified and the result is speech or song.
The difference in the voice of different people is controlled by the activity of several muscle
groups while speaking. Varying the activity in the respiratory muscles will influence the
volume of the sound. The frequency of the longitudinal oscillations is given by the stresses in
the cords that come from contractions of the muscles in the voice box. The airflow through
glottis makes the cords vibrate almost perpendicular to the airflow and thus the cords open
and close the slit. The slit is closed for a longer period than it is open when sound of low
frequency is created and the opposite goes for high frequencies. On top of that, the cords are
thinner for high frequencies than for low. The spectrum for the human voice goes from about
40 to 2000 Hz.
The apparatus of digestive
The food is processed mechanically and
chemically in the apparatus of digestive in
order to split the food so the nutrients, salts
and water can be assimilated. The process
starts with chewing in the oral cavity
where the food is divided into pieces and
mixed with saliva. The salvia consists of
more than 99% water but also mucin, a
compound of sugars and protein
facilitating the chewing. Enzymes, like
amylase that converts starch into maltose
and lysozyme that in combination with
antibodies reduces the amount of bacteria
in the oral cavity.
The process continues in the throat, in the gullet (oesophagus-matstrupe), in the stomach and
in the guts (intestine – tarmar). The partly digested food comes first to the small intestine
where nutrients are absorbed and continues then to the large intestine where most of the water
is absorbed, (9.9 litres of 10). The digestive tube (from mouth to anus) is about 7 m long.
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In addition there are glands (körtlar) as the liver and the pancreas (bukspottskörtel)
involved in the chemical part of the digestion. Secretion containing different types of enzymes
necessary for the process is produced in the glands. The gall, secreted by the liver, is used to
digest fatty substances and to naturalize acids. The pancreas produces enzymes that convert
fat, carbohydrate and proteins into components that can be absorbed in the guts. The result is
energy released to the body and also distribution of components for heating, growing and
reconstruction. Leftover leaves the body as excrement and urine.
The apparatus of locomotion
The organ system in focus in this course is the apparatus of locomotion and we will go into
detail with the different parts further on in the course. However, in order to give a short
overview, some facts in general of the apparatus of locomotion are given here.
The organs for motions, i.e. the skeleton, joints and muscles, are responsible for more than
half of the body mass, i.e. the skeleton makes about 15 % and the muscles 45 % of the body
mass of an adult human. The skeleton gives stability for the construction of an upright
position and it also provides fixation sites for the soft tissues. The skeleton bones function as
shelter for inner organs, e.g. the brain and the heart, as well as a prerequisite of locomotion,
talk and the performance of outer work. More than 200 individual bones interconnected by
joints build up the skeleton. The bones also serve as depots of minerals (e.g. calcium and
phosphor) and further, the red blood cells are produced and stored in the red bone marrow
within the long skeletal bones.
To provide locomotion the skeletal bones are joined together through the joints that have a
very low friction due to the cartilage covered contact layer and a lubrication system. The
joints are stabilized through systems of supporting ligaments and tendons and the joints have
different amount of freedom of movement. In mechanical terms we can consider them as
friction free joints with a varied number of degrees of freedom.
The muscles are responsible for the posture, the balance and the motion of the body. They
also contribute to keeping the body warm through generating heat when contracting. The
skeletal system and the muscle system are strongly coupled both structurally and functionally.
The muscle tissue continues through the tendons into the bone tissue and ensures secure
fixations. Physiologically, the muscles and the bones are also coupled through the content of
calcium. The contractions in a muscle can only take place if the concentration of calcium is
within quite narrow limitations. Since the most of the calcium depot is in the skeleton,
diseases in the skeleton may also influence the muscle function. On the other hand, the
muscles also influence the skeleton. During hard muscle work, like intensive sport practicing,
the muscles are growing and the skeleton becomes denser, it gets stronger. On the contrary, if
you stay in bed, you will soon notice both smaller muscles and a weaker skeleton.
Some skeletal bones and muscles that we are going to mention often during the course are
given in the next pictures and the related table.
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1.
2.
3.
4.
5.
6.
7.
8.
9.
20.
21.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Fig. 4 Skeletal bones in Swedish, English and “Latin”
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
kranium, skalle
ansiktsskelett
nyckelben
skulderblad
överarmsben
bröstkorg
kotpelare
strålben
armbågsben
bäcken
handrotsben
mellanhandsben
fingerben
lårben
knäskål
vadben
skenben
fotrotsben
tåben
skull
face skeleton
collarbone
shoulder blade
bröstben
breastbone
chest
column
carpal bones
finger bones
kneecap
toe bones
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cranium
viscerocranium
clavicula
scapula
humerus
thorax
columna vertebralis
radius
ulna
pelvis
carpus
metacarpus
phalanges
femur
patella
fibula
tibia
tarsal
phalanges
manubrium
sternum
Biomechanics, LTH, 2013
Anterior view
Posterior view
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Useful expressions in Latin
Bumps in the skeleton:
Capitulum, litet huvud, small round end of a bone
Caput, huvud, the head (in plural: capita)
Facies, yta, surface
Condylus, ledhuvud, rounded end of a bone that articulates with another
Spina, bentagg, bone prickle (spine)
Trochanter, benknöl, bony lumps (e.g. the two lumps on either side of the top
end of the femur where muscles are attached)
“Inverted bumps” in the skeleton:
Alveol, urholkning, hålighet, hollow
Cavum, håla, cavity
Fossa, grop, pit
Sinus, hålighet, hollow
Openings in the skeleton
Apertura, öppning, opening
Fissura, springa, spricka, crack
Porus, öppning, opening
In vivo, levande, alive, an experiment that takes place in the living body
In vitro, död, dead, an experiment that takes place in the lab on isolated tissue
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Planes of reference, motions, and directions
Sagittal plane – Divides body into right and left halves
Frontal plane – Divides body into front and back halves
Transverse plane – Divides body into upper and lower
halves
Terms
Posterior (Dorsal) – in frontal plane, towards the backside
Anterior (Ventral) – in frontal plane, towards the front
Superior (Caudal) – in transverse plane, above
Inferior – in transverse plane, below
Medial – in sagittal plane, towards the midline
Lateral – in sagittal plane, away from the midline
Superficial – towards the surface
Deep – away from the surface
Proximal – towards the trunk
Distal – away from the trunk
Palmar – palm of hand
Plantar – bottom of foot
**Supine (Anatomical) Position – standing erect, facing forforward, hands by side, palms facing forward
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Directions
•
If a motion takes place in the transversal plane along the transversal axis and in
directed inwards the centre of the body it is called medial. If it has the opposite
direction, it is called lateral.
•
A motion in the frontal plane, along the vertical axis, directed upwards is called
superiort and if it is directed downwards inferiort
•
It is possible to move in the sagittal plane, along the sagittal axis, forwards is the
motion called anteriort and backwards it is called posteriort.
•
The part of a skeletal bone that is closest to the heart is called the proximal part while
the part that is most far from the hart is called the distal part.
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Test your skills
Fill in the blank or provide a short answer
1. Groups of cells that have a common function are termed ______________.
2. The larynx is an organ of the _________________ system.
3. The system that has the ability to store minerals, such as calcium, is called the
________________ system.
4. The breakdown of ingested foods into simple molecules that can then be absorbed into
the bloodstream is called _______________.
5. The ____________________ refers to all the chemical reactions in the body.
6. The body’s ability to maintain stable internal conditions is referred to as
____________.
7. The navel is ____________ to the spine.
8. A cut that is made along the midline is called a ______________ section.
9. The function of the ____________system is to control the body functions via
hormones.
Answers:
1. Tissues 2. Respiratory 3. Skeletal 4.Digestion 5. Metabolism 6. Homeostasis
7. Ventral or anterior 8. Mid sagittal or median 9. Endocrine
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