Monthly Archives: July 2011

Lecture 16 – Survey of Bones (Continued)


What happens after a fracture?

  1. Sever bleeding; a clot forms at the site of the fracture.
  2. Periosteum – surrounding the bone is made of connective tissue cells for fibroblasts that form osteoblasts.  Osteoblasts are bone-forming cells that form fragments of bone within the clot.  The fragment plus the clot equals a CALUS.  The formation of a calus is an essential step in repairing a bone.
  3. Osteoblast formation of periosteum forms bone between the two fragmented ends.  This is called a collar.

Types of Joints

The science of joints is called arthrology.

  1. Fibrous Joints – A small amount of connective tissue between bones.  Example:  Sutures and bones of the calvarium (skull).
  2. Cartilagenous – Fibrocartilage between bones.  Example:  vertebrae –( intervertebral discs); pubic symphysis (between two pubic bones).
  3. Synovial Joints – syn – with; ovial – egg whites in natural state, not the yolk.  Example:  Humerus, which articulates with glenoid fossa; femur with acetabulum, which means vinegar cup.
  4. Hinge joints – Example: elbows.  These joints increase and decrease the angle of the arm.  Make a muscle like Popeye, the sailor man.  Then relax and straighten arm out to the side.  Hing joints are also found in the knee.
  5. Ball and socket joints-  A synovial joint, such as the shoulder or hip joint, in which a spherical knob or knoblike part of one bone fits into a cavity or socket of another.  Some degree of rotary motion is possible in every direction. Also called enarthrosis.

 Characteristics of a Synovial Joint

  1. Articular cartilage
  2. Synovial membrane produces synovial fluid
  3. Heavy connective tissue and joint capsule for stability and protection.  (I have difficulty watching baseball players slide into home plate!  That is stressful to the joints of the knee.  A little bit of learning is truly a dangerous thing, as Pope Alexander said.)
  4. Bursa cushion the joints by reducing friction caused by the surrounding muscles.  Not all synovial joints bursa; Bursa are found in knees and shoulders.
  5. Head and depression joints.  Examples:  Humerus and glenoid cavity; femur and acetabulum.
  6. Pivot joint – Example: radius with head pivot around the ulna.  This is why the anatomical position is important.  Palms must be forward in order for the ulna to be medial to the body.  If you have your palms facing backwards, the radius and ulna will pivot and change positions!
  7. Saddle joint – 1st metacarpal has a convex surface.

Joint Movement

  1. Flexion – biceps – decreasing in angle.
  2. Extension – increasing in angle
  3. Adduction – toward the midline (Adducter)
  4. Abducter – away from the midline.  For example, the deltoid muscle takes the arm away from the body.
  5. Circumduction – circular motion.

Bodies are meant to be in motion.  A sedentary lifestyle causes obesity and other illnesses, especially diabetes mellitus.  Get some form of exercise every day.  Enjoy your day.

 

2 Comments

Filed under The Skeletal System

Lecture 15 – Random Historical Facts in Medicine


We must know our history or we will be doomed to repeat it.  This was said by George Santayana.  Occasionally, I love to include facts that keep us familiar with how much we have accomplished.  As a researcher, I utilize history to keep myself encouraged to continue searching for cures.  Looking back I am happy that the researchers before us did not give up.  My favorite historical figure is Dr. Igna’c Semmelweis of the 1800’s in Europe.  Although his contributions were not recognized until after his untimely death, I am grateful for his existence.  Considered a strange character, he single-handedly determined that the cause of childbed fever arose from an absence of hand washing.  He insisted that physicians and medical students who performed dissections of cadavers, wash with a solution of chlorine and scrub with a brush.  He was never elevated to heroic status.  So I honor his insight now.  We will have a lecture devoted to his contributions to women’s health, anatomy, and microbiology.  Semmelweis trained under Dr. Rokitansky who performed over 30,000 autopsies.

 

  1.  Pathological anatomy – a field of inquiry that lies at the basis of all scientific medicine.  Founded in 1761, it is the study of structural changes that occur in organs and tissues when they become diseased.  Pathological physiology studies abnormalities in function, arose later, but overlaps.
  1.  The stethoscope was invented in 1816 by a Frenchman named Rene’ Laennec.

4 principles of examination-

Inspection

Palpation

Percussion

Auscultation

  1. 20th century – biomedicine – developed in the German-speaking countries.  Germany, Austria, and Switzerland snatched medical leadership from the French.
  2. Erysipelas, a name given since the time of  Hippocrates, which referred to a rapidly spreading inflammation or infection.
  3. 1844 – pathological anatomy became compulsory in Vienna’s medical training programs…’the corpse was now seen as a treasure trove of enlightenment, to be scrutinized without the hurry required by the urgent needs of the sick’.  Within a few decades, microscopy and chemistry would advance to the point where body fluids and tissue samples were added to the sources information.

We will pick up the pace this coming week and move towards the completion of our survey of bones.  There is so much information to cover on the body’s foundation.  For this reason, I give interesting bits of information to keep us all interested.  Have a great weekend.

Leave a comment

Filed under Anatomy Notes

Human Dissection Techniques – Advanced Anatomy Lab #2


THORAX DISSECTION

  1. Lungs and Pleural Sacs
  2. Heart and Pericardial Sacs

Remove lateral and anterior portions of the ribcage, to expose heart and lungs within the thoracic cavity.  Cut through the ribs and the intercostal muscles around the perimeter of the rib cage on each side.  Make your cuts or hole as large as possible by following the margin of the rib cage, and then going down as far laterally as you can along the side.  Essentially, this is along the mid-axillary line; You will have nice exposure for your thoracic organs.  Get your fingers under the rib cage and peel the layer of tissue, the parietal pleura away from its attachment to the under side of the rib cage.  Leave as much of that intact as possible as you remove the bone.  Remove the ribs and the intercostals muscles on each side.  The parietal pleura should be clear.  Cloudiness, opaque, or thick regions could indicate previous infection within the sac.  Visceral pleura are delicate; They are immediately on the surface of the lung to provide a friction-free movement as lungs fill with air and release during exhalation.  Remove sternum from midline.  This may require a saw to cut the superior and inferior ends of the sternum.  A chisel and hammer may work as well.  Be sure to bluntly separate the soft tissue from the deep surface of the sternum.  Keep the vessels intact (internal thoracic or internal mammary arteries), which supply the chest wall and continue to the abdominal wall to provide collateral circulation.

Now we can see the lungs and the heart.  We did preserve the internal thoracic artery and vein on either side.  Remove the lung.  Be careful that you do not cut the phrenic nerve which innervates the diaphragm; It travels between the lung and the heart.  To remove the lung, push it laterally and the heart in medially, so you can see the region of the lung called the hilus.  This is where a variety of structures enter or exit the lung, such as the airway, blood vessels, nerves, and lymphatics.)  Make a clean cut at the hilus of the lung.  Use a knife or a scalpel.

Once the lungs are removed, the right and left lungs can be easily distinguished, because they have different numbers of lobes.  On the right lung the oblique fissure separates the inferior lobe from the superior and middle lobes.  The horizontal fissure separates the superior lobe from the middle lobe.

Lungs tend to be darker on the posterior side of the lung, due to blood collection; the cadaver has been laying on its back and blood has collected in the posterior area due to gravity.  Turn the lung over to look at the hilus and to study some of the structures there.

Pulmonary arteries – of intermediate thickness – provide deoxygenated blood to the lung

Pulmonary veins – thinnest wall

Bronchus – cartilaginous – thickest wall – must remain patent at all times

Hilar lymph nodes –

Bronchial circulation – which supplies a secondary blood supply to the lungs

 

Remember R   A    L    S

On the right lung, the pulmonary artery is anterior to the bronchus.  Pulmonary veins are more inferior structures at the hilus.

Left lung – Separated by an oblique fissure.  Superior lobe has an appendage called the lingula.

On the left lung, the pulmonary artery is superior to the bronchus.  Two pulmonary veins are more inferior.  Hilar lymph nodes are very black.  They contain some of the pollutants that have passed through the lungs.  Tiny vessels around the bronchus are the bronchial vessels.  (A couple of mm in diameter)  There is a dual blood supply to the lung.

Place the left lung back into the chest so that we can discuss the pleural sac that surrounds the lung.  The visceral layer of the pleural sac is immediately on the surface of the organ.  The outer parietal layer has different names depending on which surface it is coating.  The portion of the parietal pleura that is adherent to the inside of the rib cage is called the costal pleura; the diaphragmatic pleura coats the superior surface of the diaphragm.  On the midline, between the lung and the heart, is the mediastinal pleura, which is also a portion of the parietal pleura.

Look at how much of the thoracic cavity the lung occupies.  It doesn’t occupy the entire height of the cavity; It falls a little short.  There are some places where parietal pleura rub against another layer of parietal pleura.  A good example is where the diaphragmatic pleura and the costal pleura rub against each other, in an area called the costodiaphragmatic recess.  This region can be important clinically, as a physician can insert a needle to withdraw fluid that has accumulated in the pleural cavity.  Using this area reduces the risk of puncturing the lung itself.  Now that both lings are removed, we can explore the mediastinum, which includes the heart.  Like the lungs, the heart is surrounded by a sac called the pericardial sac.  This sac reduces the friction as the heart enlarges and contracts again.  We need to cut through the parietal pericardium to expose the heart.  We will see the visceral pericardium right on the heart.  Be careful not to cut the phrenic nerve, which innervates the diaphragm.  Keep the internal thoracic vessels intact as well.

Make and “X” shaped cut within the pericardial sac and flip back the flaps to expose the heart.  You are now looking at the visceral pericardium.  There is a moderate amount of adipose tissue on this layer.  We will have to dissect through that to expose the coronary vasculature of the heart.

Identify two sinuses within the pericardial cavity –

  • These are the structures that form due to the way the pericardium attaches to and reflects off of the surface of the heart.

1)        Oblique sinus – Put your hand behind the heart within the pericardial cavity; You can slide it only a certain distance posterior to the heart and then you reach a dead end.

This is where the visceral and parietal pericardium become continuous with each other at the surface of the heart.  We cannot go any further because of the oblique sinus.

Similarly, at the superior end of the heart and just to the left of it, we can slide fingers through and get through and get to the other side–  to the  — 2)  Tranverse Sinus.

Transverse sinus  – more clinically significant than the oblique sinus.  Surgeons use this transverse sinus to clamp off the outflow vessels surgically; which are the aorta and the pulmonary trunk.

Slide 2 fingers behind the “two vessels” and come out on the opposite side.  (This region is called the transverse sinus.)  Remove heart from the mediastinum by cutting through the great vessels, or major inflow and outflow vessels of the heart.

Start by pulling the heart superiorly and cutting through the IVC, which is bringing the blood back to the heart from the regions inferior to the diaphragm.  There is no real length to the IVC.  It comes through the diaphragm and immediately enters the RA of the heart.

Cut through aorta and pulmonary trunk at the transverse sinus region.  Make all these incisions within the pericardial cavity to ensure that no internal structures are damaged.  We will need to investigate the internal structures in later dissections.

Last large vessel needing to be cut is the superior vena cava, which returns blood from upper limb and head back to the RA.  We have already cut through the PV when we removed the lungs, so we need to bluntly dissect those from their penetration to the pericardial cavity so we can pull the heart out.

Pectinate Muscles –

Left Atrium is on the posterior side of the heart.

Cutting the heart sagitally will expose both ventricles

R —thinner—only pumps next door to the lungs

L—thicker—-pumps all over body

Inside Ventricles –

Structures prevent backflow of blood

Tricuspid valve

Chordi tendonae – prevents valves from flipping inside out

Tribeculae carnae

Bicuspid (aka mitral valve)

Septomarginal Band – aids in proper contraction of right ventricle.

Let’s understand how well the heart is protected by the sternum and the thoracic cage.  The heart is positioned asymmetrically within the chest, so that on the right side it projects appr. 1 inch toward the right from the edge of the sternum.  It is important to be able to predict injury caused by a puncture wound.  In this case the right atrium would be affected by a potential puncture wound, to the anterior chest wall.  On the left side the heart projects appr. 3 inches from the left side of the sternum.  The R and L ventricles could be damaged from a puncture wound.

Landmark used to show boundary between right and left ventricle – anterior interventricular artery

Aka L A D – Left Anterior Descending Artery

In order to see the origin of the CA from the aorta, we need to fold down the pulmonary trunk and pin it out of the way.  We want to see the origin of the coronary arteries from the aorta.  Now, as soon as the aorta exits the left ventricle, we can see that it has 2 major branches heading in either direction —R and L coronary artery.  Dissect these by removing the superficial tissue off the surface of the heart by bluntly dissecting it with forceps or a probe by scraping off the fat.  LCA – very short, bifurcating almost immediately into the AIA (anterior interventricular artery) and the circumflex artery, which will wrap around to reach the posterior side of the heart.  Again, the 2 major branches of the left CA are the anterior interventricular artery, aka LAD – Left Anterior Descending, and the circumflex artery.

The LAD is one of the most commonly obstructed vessels in the coronary circulation, and likely the most commonly by-passed.  Looking at the right coronary artery, multiple branches come off as it wraps around the heart.

For now focus on major branches –

Right Marginal Artery

RCA continues to the posterior surface of the heart, and it sends a branch down called the posterior interventricular artery.  There will be some collateral circulation and anastomoses between the posterior interventricular artery and the anterior interventricular artery branch of the left coronary.  After these CA’s supply the myocardium with its O2 and nutrients, that deoxygenated, nutrient poor blood needs to be returned to the RA.  A set of cardiac veins will be responsible for that.  The vessel called the coronary sinus is going to receive all of the de-oxygenated blood from the cardiac veins.  You can match cardiac veins with the major branches of coronary arteries.

SO, traveling with the posterior interventricular artery, we have the middle cardiac vein, which is passing superiorly, joining the coronary sinus, and then together, empty into the RA.  Returning to the anterior side of the heart, we can see the longest cardiac vein, which travels with the branches of the left coronary artery and carries the deoxygenated blood back around to the posterior side of the heart, into the coronary sinus and then into the right atrium.

Internal anatomy of the heart –

Start with the atria

Right atria with the SVC and the IVC delivering the deoxygenated blood back to the heart.  Using a pair of scissors to cut between the vena cava, you can open the right atria and look at some internal structures.  The inside is smooth.  The fossa ovale is a depression located within the septum, separating the right and left atria from each other.  The fossa ovale represents an opening that was present between the two atria during embryonic development.  Usually, this closes off after birth, so that we establish the normal adult circulation.  Inside the RA are rough areas called pectinate muscles.  (Ridges of muscles).

Flip the heart over to look at the left atria, which is on the posterior side of the heart.  4 pulmonary veins are returning oxygenated blood from the lung back to the heart.  Cutting through the left atrium, there is nothing remarkable to see.  Cut the heart sagitally to investigate the ventricles.  Interventricular artieries will be used as a guide to cut from the apex of the heart up to the base.  (Cut perpendicularly to the interventricular arteries.)  Do not cut into two pieces.  Use forceps to remove blood clots and rinse.

Right ventricle – much thinner because it only has to pump blood next door to the lungs.

Left ventricle – much thicker because it has to pump blood to the entire body.

The interventricular septum, which separates the right and left ventricle has an inferior muscular portion and at the superior edge there is a much thinner membranous portion.

Inside ventricles – the main function of these structures is to prevent backflow while the heart contracts.

Right side – tri-cuspid valve and leaflet—The leaflet has strands attached called chordi tendonae.  (Strands of connective tissue)

These tendons are used by papillary muscles to prevent valves from everting or flipping inside out as the ventricle contracts.  The papillary muscles use the chordi tendonae to prevent eversion of the tri-cuspid valve.  There are additional ridges of muscle in the wall of the ventricle called tribeculae carnae; Similar structures exist in the left ventricle.  Papillary muscles attach to chordi tendonae and are attached to the bicuspid or mitral valve, AV valve that will prevent blood from flowing backwards, from LV into LA during ventricular contraction.

Myocardium is brown.  (No MI)  Problems could affect the conduction system, which cannot be seen grossly or histologically.  The conduction system controls the contraction.

RV only – The septomarginal band extends from the interventricular septum to the papillary muscle.  It does contain a portion of the conduction system.

Leave a comment

Filed under Human Dissection Techniques

Lecture 14 – Skeletal System (Cont’d)


Let’s begin with a bit of mathematical trivia.  Do you know how the search engine Google came up with its name?  Googol is the mathematical term for a 1 followed by 100 zeros.  This term was coined by Milton Sirotta, nephew of American mathematician Edward Kasner.  The term was popularized in the book “Mathematics and the Imagination” by Kasner and James Newman.  Google’s usage of the term reflects the company’s goal of organizing incredible amounts of information on the Internet.  (As organized as the information is, it cannot all be accurate.  Know the credentials of your sources.)  So, a googol of something is a very large quantity, sort of like a gazillion dollars.  You must be very comfortable with numbers in order to enjoy this career.  Learn the language of math.  Once you know the definitions, math becomes much more simplistic.

Maxilla – upper jaw (keystone of the face)

What is a keystone?  Or a cornerstone?  Keystone and cornerstone are used metaphorically to describe a course of action or a unit upon which all others rest.  If the keystone is removed, the entire structure will collapse.  In the Bible, Jesus is described as the cornerstone of spiritual life; all who place trust in him will never be put to shame.  Pennsylvania is considered the Keystone State, as Philadelphia was the capital of the United States before Washington, D.C.  All of the major players lived in Philly in the 1700’s, such as Washington, Jefferson, Franklin, etc.  Pennsylvania was the place of the signing of the declaration of Independence, the home of Betsy Ross, and the liberty bell.  If one was to remove PA from America, the entire historical structure would collapse.What would happen to cheese steaks, hot pretzels, and water ice, if Pennsylvania was obliterated from the earth?   Historically and spiritually, we can identify with a keystone; even if history and religion are not your favorite academic subjects.

Why is the maxilla called the keystone of the face?  All facial bones touch the maxilla, except the mandible.  There are 2 parts to the maxilla.  It has a protusion called the zygomatic process.  The maxilla has a role in forming the roof of the mouth; the anterior roof of the mouth is formed by the maxilla.

Nasal bones – 2 bones form the bridge.  We have a special place for our glasses to sit!

2 – inferior conchae – the –ae makes it plural.  This is the inferior lateral nasal cavity.

1 – vomer – on the medial nasal cavity (commonly called the septum)

Lacrimal bones – 2 of them, also, on the medial portion of the orbit.  (inferior medial orbit)

(Note: Lacrimal glands are responsible for tear formation.  It is OKAY to cry!  That means your lacrimal ducts work!)

Zygomatic bones – Form the middle aspect of the cheek bone.

Let’s review.  The whole cheek is made up of 3 bones –

Zygomatic process of the maxilla

Zygomatic bone

Zygomatic process of the temporal bone

Palatine bones – 2 of them will form the posterior portion of the hard palate (posterior roof of mouth)

Hard palate – Anteriorly – formed by the maxillary bone

Posteriorly – formed by the palatine bone

The mandible forms the only movable joint of the skull.  It is called the keystone of the lower jaw.  I am happy that this joint moves, as most of us love food.  I work very hard and treat myself to a small piece of chocolate every evening.  My motto:  “Chocolate solves everything.”  The statement is grossly incorrect, but that is my silly comforter.  Chocolate does not really solve everything, but the rewarding feeling gives me the boost I need to strategize through my problems.

By now you know that I have devoted my life to a couple of causes that have touched my heart, so to speak.  I am passionate about domestic violence prevention and women’s health.  Being self-sufficient is a great way to end domestic violence.  Many women return to violent situations because the abuser is the financial support system.  This is why I advocate for women to study hard, work diligently, and save for emergencies.  In my lectures on the nose and jaws, I jokingly say that one purpose of these body structures is to provide a nice living for cosmetic surgeons and ENT teams.  My humor can be dry and sarcastic at times.  I feel that sometimes we have to be shamed into doing the right thing.  Although we have excellent surgeons who have superior training, we should not remain in violent relationships of any sort.  It is my duty to constantly air this commercial.  Repetition works.  Pass the information on to others who need to hear my commercial.  As much as I extol the virtues of my dark chocolate comfort food, even chocolate cannot heal the physical and emotional wounds from an abuse.  Protect your body and your mind.  It is the only body that you have.  Make solid and safe choices.  Choices can be life-making or life-taking.  Do well with this new information!

 

 

 

Leave a comment

Filed under The Skeletal System

Lecture 13 – Bones – Axial and Appendicular Skeletons


Hopefully you were not bored with all of the background information.  I read the lectures frequently to search for gaps in knowledge that we need to cover in order to make you successful as a medical or allied health student.  I also re-read so I can make good on promises I have made to cover specific topics.  It may seem that we are lingering on bones and related material, but you will appreciate it once we are covering complex processes of the body.  We could possibly cover the bones in 5 or 6 more sessions.  Before we move on to the intense survey of blood, we will review scientific notation, significant figures rounding, and conversion factors.  We attack and destroy myths that women and people of color are not proficient with math and special orientation.  Once we cover everything that may have been unclear for you in the past, we will move quickly.    

When you put your hands on your hips, you are touching the ‘crest of the ilium.’  That is a great place to get bone marrow, as it is close to the surface of the skin.

The axial skeleton runs through the medial axis of the body.  The axial skeleton consists of the skull; hyoid bone (in neck); sternum/ribs (thorax) – also called thoracic cavity; vertebral column; and the ear occicles within the skull.  The ear occicles are the smallest bones in the body.  The hyoid bone is u-shaped and is found in the anterior portion of the neck.  It is inferior to the mandible and superior to the larynx.  It has no bony attachments, but is held by muscles and ligaments.  (Lay people may call it the Adam’s apple.)

The appendicular skeleton:

Lower extremities and pelvic girdle equals –  ilium, ischium, and pubic bone.  (We sit on the ischium.)

Skull and skull cap equal the calvarium.

Calvarium – 8 bones –

Frontal – (forehead, anterior fossa of base of skull, frontal sinus, 2 parietal walls)

Parietal (2)

Temporal (2)

Occipital – very thick – The spinal cord attaches to the brain through the foramen magnum (large hole).  The occipital bone articulates with the first cervical vertebrae, called the altas.  Silly hint: An atlas holds up the world on a globe, and the altas hold up the brain.  C1 is the 1st cervical vertebra or the atlas.  C1 is just a ring with no body.  C2 looks different because it has a tooth-like process, called the adontoid process.  The bodies of C1 and C2 are fused together and look like a tooth.  This fusion allows us to move our heads laterally (side to side).

Sphenoid – inside

Ethmoid – inside

Facial bones – 14 bones

Sutures – joints between calvarium bones.  At birth we have a thin layer of connective tissue, commonly called the soft spot.  The technical name is fontanelles.  The brain is growing so the sutures cannot be tight.  We have a coronal suture.  Remember the crown?  We also have a mid-saggital suture, and a lamdoidal suture, which is shaped like the Greek letter lamda.  Lamda looks like an upside down “v”.

The temporal bone has 4 parts:

1 – Squamous (flat) – thin and translucent

2 – Mastoid (breast – like) – The mastoid process has a sinus that connects to the middle ear and nasopharynx.  Route of  infections —-sinus—–middle ear—–nasopharynx.

3 – Zygomatic Process – bar – posterior portion of cheek bone (Review anatomic directions if necessary.)

4 – Petrous portion of temporal bone – Hard – houses the inner ear.

The vertebral column has 33 bones.

7 Cervical – neck

12 Thoracic

5 Lumbar – All of these listed above are movable.

5 Sacral

4 Coccygeal – These 9 are fused together and are immovable.

When looking at the vertebral column posteriorly it is a column.  When viewing the vertebral column laterally there is a natural curve.  There are some abnormal curves, as well.  An accentuated thoracic curve is called kyphosis.  The general public may use the term hunchback.  An accentuated lumbar curve is called lordosis.  Some people use the term swayback.  I prefer that we use the proper terms and not use the offensive ones.  An accentuated lateral curve is called scoliosis.  Scoliosis is more common in females and appears in puberty.

Now you need to start memorizing this information.  Read each lecture four or five times aloud until you can recite the contents.  You have to have a firm foundation.  As you can see we cover a plethora of details.  Remember, this is a personal, self-study to accentuate the work given by your professors.  I am really pleased with the parents of middle and high school students who are downloading this information for their future medical careers.  Those fortunate students will be go to the head of the class.  Do well with this information!

Leave a comment

Filed under Anatomy Notes

Lecture 12 – Part 2 of Review Power


Chemistry is an experimental science and is divided into two branches, pure chemistry and applied chemistry.  Pure chemistry is theoretical and predicts results of experiments or observations.  Applied chemistry involves the practical applications of materials and reactions.  How does soap made from ashes and fat get clothes clean?  How do computer chips made of silicone (sand) carry information and electricity?

A hypothesis is a statement or idea that describes or attempts to explain observable information.

An experiment is a controlled testing of the properties of a substance or system through carefully recorded measurements.

Let’s review some key points in the history of science.  Capernicus believed that from the sun outwards, rotated Mercury, Venus, Earth (with the moon rotating around it), Mars, Jupiter, and Saturn.  This strange hypothesis was not received well since everyone knew that the sun revolved around the earth.  In 1609, Galileo used his homemade telescope to test Capernicus’ hypothesis.  Galileo took measurements and recorded data that confirmed Capernicus’ hypothesis.  In doing so he discovered the key to valid research was experimentation.  His scientific curiosity caused him to record observations regarding changing factors, such as time, position of moon, stars, and sun.  These observations and calculations led to the discovery of the four satellites of Jupiter in 1610.  Galileo’s scientific diligence is why we consider him the founder of the scientific method.

Antoine Lavoisier (1743-1794) insisted on accurate measurements and developed a theory of combustion.  He determined that combustion results from a chemical bonding between a burning substance and a component of the air, which he named oxygen.  The bonding of these two forms something new.  Joseph Priestly and Antoine Lavoisier performed experiments together and discovered that the air was composed of several different components, including nitrogen.  Previously it was thought that air was composed of one all-purpose gas.  Lavoisier found that water contained hydrogen and oxygen.  He was the first to arrange chemicals into a family of groups, and the first to attempt to explain why some chemicals form new compounds when mixed.  This is why he is considered the father of modern chemistry.

A theory is the result of thorough testing and confirmation of a hypothesis.  It predicts the outcome of new testing based on previous experimental data.

A law is a hypothesis or theory that is tested time after time with the same resulting data and thought to be without exception.

John Dalton made significant contributions to chemistry by:

Developing the Law of Partial Pressures in 1803;

developing the atomic theory (his most important discovery);

developing the law of multiple proportions;

publishing a list of atomic weights and symbols.  (This gave chemistry its initial formal vocabulary, which we memorize today.)

APPLICATIONS FOR EVERYDAY

In case you are wondering why I am giving such a detailed background in chemistry, I will relieve your mind.  Chemistry is a part of our daily lives, as we cook, clean, breathe, and go about our activities.  NASA, the National Aeronautical and Space Administration is famous for applying basic science in new ways.  NASA uses the scientific method teams with scientists in industry to improve pharmaceuticals, optics, and bioengineering devices.  Dual purpose science and technology brainstorms are called spinoffs.

Examples:

1)      Medical Gas Analyzer – Astronaut physiological monitoring technology; Used to measure operating room anesthetic concentrations, such as oxygen, carbon dioxide, and nitrogen; Ensures precise breathing environments for surgery patients.

2)      Bioreactor-  A cell culture device developed at NASA – Johnson Space Center that brings a new scientific tool to cancer and virus testing without risking harm to patients.  The rotating bioreactor walls allow three-dimensional growth of tissues without limiting pressure points.  It has successfully cultured over 35 cell types.

3)      Low Vision Enhancement System – Provides a video scene via a system of optical mirrors that project video images onto the wearer’s retinas.  The goggle-like headset help counteract the effects of macular degeneration associated with aging, diabetic retinopathy, glaucoma, and tunnel vision.

A wide variety of elements are found in the body.  These elements combine to keep our bodies healthy.

Oxygen                                                 64.6%

Carbon                                                 18%

Hydrogen                                             10%

Nitrogen                                               3.1%

Calcium                                                1.9%

Phosphorus                                          1.1%

Chlorine                                               0.4%

Potassium                                            0.36%

Sulfur                                                    0.25%

Sodium                                                 0.11%

Magnesium                                          0.03%

Iron                                                        0.005%

Copper                                                   0.0004%

Tin                                                          0.0001%

Manganese                                           0.0001%

Iodine                                                  0.0001%

Others Trace Elements Combined        0.14%

Elements Found on Earth

Oxygen (O)                                                   49.2%

Silicon (Si)                                                      25.7%

Aluminum (Al)                                                7.5%

Iron (Fe)                                                           0.005%

Calcium (Ca)                                                    1.9%

Manganese (Mn)                                            0.0001%

Tin (Sn)                                                             0.0001%

Phosphorus (P)                                                1.1%

Chlorine (Cl)                                                     0.4%

Potassium (K)                                                   0.36%

Sulfur (S)                                                           0.25%

Magnesium (Mg)                                             0.03%

Sodium (Na)                                                     0.11%

Iodine                                                                 0.0001%

Zinc (Zn)                                                            0.002%

Copper (Cu)                                                       0.0004%

Others Cumulatively                                        0.47%

So, what do these elements do for us?

Element                                                              Function in the Body

Calcium                                                               Bones, teeth, and body fluids

Phosphorus                                                        Bones and teeth

Magnesium                                                         Bones and body fluids; energy

Sodium                                                                Cellular fluids; transmission of nerve impulses

Chloride                                                               Dissolves salt in extracellular and stomach fluids

Potassium                                                            Cellular fluids and transmission of nerve impulses

Sulfur                                                                    Amino acids and proteins

Iron                                                                       Hemoglobin, muscles, and stored in organs

I hope you are finding the background information helpful.  We all have gaps and inconsistencies in our knowledge.  One of my goals has always been to fill in the educational gaps.  More than ever I am seeing liberal arts majors applying to medical school.  So many have extensive knowledge in other fields.  Intense review of the sciences is extremely important for the student doctor who majored in chemistry as an undergraduate, as well as the English major who decided that medicine is the new art form.  Now we are better equipped to continue our intense survey of human bones.  Make it a great day!

Leave a comment

Filed under Chemistry Review

Human Dissection Techniques – Advanced Anatomy Lab


Locate bony landmarks for dissection.  Palpate on self, skeleton, and cadaver.

Clavicles

Sternal notch – lies between clavicles

Xiphoid Process (end cartilage)

Pelvis – 2 boney prominences – anterior superior iliac spine

1st incision will extend from the sternal notch, down the body of the sternum, to the xiphoid process.  Locate the margin of the ribs.  Extend the incision distally toward the umbilicus.  Make incision around umbilicus, down to a line that connects the two anterior superior iliac spines.  The initial incision runs down along the body of the manubrium of the sternum.  You can press deeply because the bone from will prohibit you from going any further.  Be careful beyond the xiphoid process.  You do not want to puncture the abdominal cavity.

You should have successfully made the incision from the sternal notch to the xiphoid, and cut down to the bone to expose the layers of skin.

1)      Epidermis

2)      Subcutaneous Fascia – consists mostly of fat and connective tissue that extends from the skin all the way down to a dense fascia layer which covers the muscle.

As you extend the incision below the xiphoid process, you need to make sure you are not cutting deeper than the subcutaneous fascia layer.  The thickness of this layer is variable and depends on the relative obesity of the cadaver.

Extend the incision down the midline on the anterior abdominal wall; make another mid-clavicular incision (distally – parallel to midline incision)  This allows us to pull back the flaps of skin to further investigate.

Small cutaneous nerves that are extending through the deeper fascia covering the muscle coming to the skin, and traversing the superficial fascial space.  These nerves extend through the deep fascia to get to the skin.  These nerves innervate both the superficial compartment and the skin.  On the lateral flaps you will notice branches of the same nerves.  (Lateral cutaneous nerves)

Inguinal region —(Look for superficial lymph nodes.)  Use blade of scalpel to make incisions lateral to the penis.  Stroke the inguinal region vigorously.  On the lateral aspect of the scrotum, locate the saphenous vein, which comes up from the leg.  Lymph nodes should be nearby.

Lymph nodes – Size of a pea or larger

Same color as fat

Feel quite firm

Many lymphatic channels  or strands attach to each lymph node.  Multiple channels come into the inferior aspect of the node.  Fewer channels come out of the top.

Lab #2

Muscles of Back and Veterbral Column

On posterior side of cadaver-

Make incision along midline, over spinous processes of vertebra, from the nape of the neck to the sacral region.  Make about six transverse cuts which will allow us to now strip away skinNote the posterior cutaneous nerves.  Some may be stubs.  Also look for vessels that accompany nerves.

OBJECTIVE:   Expose vertebral column and see joints that those muscles move.  Open the vertebral column to expose the spinal cord which is protected within.  Clean away any subcutaneous tissues.  The first muscles you will see are not true back muscles.  (They exit the back and move the upper limb.)

Trapezius – Upon reflecting, you will find additional limb muscles deeper, including the rhomboids and the levator scapulae.  All these muscles will be reflected to see the true back muscles, which move the vertebral column.  Lower in the back, there is a large muscle that moves the upper limb, called the latissimus dorsi.

Reflect all superficial muscles – make an incision along either side of the midline, which is the attachment of all of the primary extrinsic muscles.  By doing that, you can get your hand deep into the muscle; Within a plane of some loose connective tissue, you should be able to separate that muscle from the deeper ones and simply reflect back and out of your way.

Intrinsic back muscles are exposed.  They are responsible for removing the vertebral column.  Several groups of intrinsic back muscles exist with complicated attachments.

A huge mass of muscle exists vertically along either side of the column – erector spinae group, which is particularly well developed in the lower back.

Use a scalpel to cut down either side of the spinous processes of the vertebrae; then use a chisel to scrape that muscle away from its other attachments.  You will be able to reflect that entire group of muscles to expose the vertebral column itself.

Cervical Region- Has additional intrinsic back muscles.  The most superficial is the spleneous capitus, which forms a V on the back of the neck.  The orientation of the muscle fibers of the spleneous capitus, form a V on the back of the neck.  These fibers are angling from the midline, upward and laterally, as they approach and attach to the skull.

By cutting along the midline, through the spleneous group, you can find a deeper group of muscles.  These run more vertically along the column and are called the semi-spinalis capitus.  All these extrinsic back muscles are going to be responsible for extending the spine and also rotational movements of the spine.

Using an articulated vertebral column, we can appreciate some of the surface landmarks that we see on the cadaver.

Spinous processes – right on the midline—are the bony prominences that extend posteriorly, and are for muscle attachments.  Look closely and you will see transverse processes, which also serve as muscular attachment points.  There are some joints between the pairs of vertebrae at each level.  (There is a limited amount of movement at each intervertebral joint.  The vertebral canal protects and houses the spinal cord.  To expose the spinal cord and its branches, you must cut approximately .5 cm on either side of the spinous process.

The part of the bone that is attached to the body extends posteriorly and is called the pedicle.  The portion of the vertebra that forms the roof over the canal is called the lamina.  The lamina meet at the point where the spinous process forms.  The pedicle and the lamina meet at a place that forms the transverse process.  We can also see articular processes form joints between the sequential vertebrae.

The size of the vertebral canal is approximately 1 cm in diameter.

GOAL:             Remove spinous processes and laminae along the entire length of the vertebral column.

After you have cleaned away as much of the soft tissue as possible, the next step is to take a saw and score along the entire length of the vertebral column.  After you have cleaned as much of the soft tissue as possible, the next step is to take a saw and score along the entire length of the vertebral column, just lateral to the spinous processes, cutting to the lamina.  This will insure that you expose the spinal cord and the surrounding tissues, without going too wide.  After you have done that initial saw cut, which should be relatively shallow, you want to finish the removal of the laminae by using a chisel and a hammer.  Angle the chisel in medially and then use the hammer to continue going through the bone and removing the vertebral column incrementally along the entire length.  Expose the spinal cord and the meninges.  You may be able to remove the vertebral column in one piece or in smaller sections.  (You should have just removed the laminae and spinous processes of the vertebral column.

You should also see the dura mater, which is one of the layers of the meninges.  (Dura mater – Medieval Latin, meaning literally “hard mother”.)  Incise the dura mater to see the other two coverings of the spinal cord.  (Slit the dura mater with a probe and separate.)

Arachnoid mater – spider web-like appearance; thin transparent membrane which provides a cushioning affect for the CNS.  Arachnoid and pia mater are sometimes called leptomeninges.  In a cadaver, the arachnoid is collapsed because the fluid is gone.

Pia mater – gentle mother or tender mother – adheres directly to the spinal cord.  Cut and remove dura mater.  Once you see the spinal cord, you will see it is significantly shorter than the vertebral column itself.  The spinal cord ends at approximately at vertebral level L2.  The spinal cord becomes more narrow at its inferior end, forming a structure called the conus medularis, an inferior cone-shaped structure.

Coming directly off of the conus medularisis a strand of tissue called the filum terminale, which is a specialization of the pia mater, which anchors the spinal cord to the coccyx.  It runs inferiorly within the vertebral column to do so.  The cauda equina mingle with the filum terminale.  They are dorsal and ventral nerve rootlets that will form spinal nerves forming at sequential vertebral levels, and exiting the vertebral column.  This is how the entire body receives innervation.

Look at the cranial area:

Focus on each spinal nerve.

Strands branch off of the spinal cord.  (We are at the posterior, dorsal side.)  Dorsal rami – contain sensory nerves and information going back to the spinal cord.  Ventral rami branch from the ventral or anterior side of the spinal cord, carrying motor information.

Denticulate ligament – another specialization of the pia mater, helps to anchor the spinal cord and hold it in position.  The denticulate ligaments come up the lateral edge of the spinal cord and through this space and anchor the spinal cord to the dura mater.  This landmark is helpful because it separates the dorsal or sensory rootlets from the ventral or motor rootlets.  Let’s follow those dorsal and ventral rootlets away from the spinal cord and ultimately, they will come together to form a spinal nerve from this level.  Following them away from the spinal cord, as you get to the position of the intervertebral foramen, there is a swelling that represents the dorsal root ganglion.  This is where the sensory nerve cells are found; For those axons that are traveling within the dorsal root.  Going further away you will find the major branches of the spinal nerve.  The spinal nerve itself is very short where all of the sensory and motor fibers are together.  (About 2 mm long)  Immediately you will find that the spinal nerve branches into a dorsal ramus, which is quite small because it only innervates the deep back muscles or the true back muscles, and provides cutaneous innervation as the posterior cutaneous nerve.

The ventral ramus is much larger because it has a much greater territory to supply.  This nerve wraps completely around the body wall; gives off the lateral cutaneous nerve and also the anterior cutaneous nerve.  The communicating ramus, which will link the spinal nerve to the sympathetic trunk, is part of the autonomic nervous system.

Cut a slice of thoracic cord:  (Less than a dime in diameter)

Gray matter – central, and looks whiter in the embalmed specimen

White matter – on the perimeter – has a darker appearance to it.

LAB #3

Abdominal Wall

Muscles of the anterior body wall –

1st Step – Reflect the pectoralis major muscle

Find the inferior margin of the muscle and run fingers medially.  Cut the muscle from the underlying ribs and from its attachment to the sternum and the clavicle.  This will allow you to reflect the muscle.  Do not be concerned about destroying the nerves or arteries to this muscle because they will all be found on the underside.  You will expose the pectoralis minor, which is attached to the anterior rib cage.  You should cut along its margin of attachment to reflect.  This will reveal the bony thorax showing the ribs and the intercostals spaces, which are filled with the intercostals muscles.

Remove a block of the intercostals muscles; Break a section of three or four ribs (2-3 cm long) and remove the segment.  Find a blood vessel which courses from the subclavian down along the inner surface of the ribs ——internal thoracic artery and internal thoracic vein.  As this artery courses down the underside of the thorax, it is sending slender branches to each of the intercostals spaces; so that arising from the interthoracic artery is the anterior intercostal artery, which will supply each intercostal space.

The next step is to reflect the external and internal transverses abdominal muscle.  Start by finding the upper margin of the external oblique.  The fibers are oriented towards the midline.  We will cut these fibers from the superior aspect to the umbilicus.  Place a pair of scissors into the superior margin, under the surface, to use as a guide.  Reflect the external oblique.  Be careful.  Do not damage the inguinal area; We will study later.

We have separated the external oblique from the internal oblique by doing a blunt dissection.  There is some fine connective tissue between the two.  It is very easy to separate the two once you have found the plane.  Identify the internal oblique by the direction of its fibers.  These fibers are at right angles to each other.

Cut along the margin of the internal oblique.  It is a thin muscle, so do not cut very deeply.  Do a blunt dissection beneath the internal oblique, so that you can reflect it and expose the underlying transversus muscle.  In the fine connective tissue between the second and third layer, we find the intercostal nerves.  They extend down to the abdomen and innervate these muscles.  These will appear in a regular fashion.

Rectus abdominus –

Found within a compartment called the rectus sheath, this thin, CT is really a tendon.  It is contributed to by each of the muscles we just dissected.  As the external oblique, internal oblique, and transversus muscles come toward the midline, the fibers stop.  Their tendon is a very thin, flat tendon.  That tendon splits as the muscles join together at the lateral margin of the rectus muscle.  We will cut the anterior margin of the rectus sheath.  There is an anterior and posterior lamina (or portion of the sheath).  There is another rectus abdominus within a sheath on the other side.  The rectus muscle is composed of several muscles which have come together.  They are really separate muscles which give rise to the tendonous inscriptions that can be seen.  Lay people refer to a “6-pack” as the perfect set of rectus abdominus muscles.  The muscles hypertrophy to cause this effect.  Since the rectus is made up of several muscles, one would expect more than one innervation.  Earlier we saw the nerves traveling between layers 2 and 3, coming around the body.  We should expect the nerves to continue into the rectus on its lateral margin.  During surgery you would not enter the abdomen by making an incision from the inferior to the superior aspect of rectus abdominus, as the nerves would be severed causing paralyses to this muscle.  One technique for entering the abdomen is to cut the anterior portion of the rectus sheath and reflect; Push muscle towards its innervations; Cut the posterior lamina and enter the abdominal cavity.

Another feature of the rectus muscle is its blood supply.  Just as is the case with the pectoralis major, the blood and nerve supply are on the undersurface.  A large artery travels on the underside of r. abdominus.  The internal thoracic artery, giving off the anterior intercostals, continues on below the margin of the rib cage and continues on the undersurface of the rectus muscle.  It then becomes the superior epigastric artery.  (Same vessel – new name).  Likewise, there is another artery that arises from the external iliac, which is the end of the aorta.  It arises and comes up on the under surface of the inferior portion of the rectus muscle.  They meet somewhere in the middle.  The meeting of these muscles introduces the concept of anastomotic connections.  If a blood cell was traveling up in the epigastric artery, it would be possible for that cell to continue into the superior epigastric artery.  The vessels represent a site for collateral circulation.  The upper portion of the rectus can actually receive its blood from the lower stem, or inferior epigastric.

Leave a comment

Filed under Human Dissection Techniques