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!

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