A summary (sort of) of the axial and appendicular skeleton

The axial skeleton consists of the skull, vertebral column and the thoracic cage while the appendicular skeleton consists of the pelvic girdle, the pectoral girdle and the upper and lower extremities.

Starting with the...

The Axial skeleton.

The axial skeleton consists of the skull, which is divided into either a cranial bone or a facial bone. The cranial bone is directly connected to the brain while the facial bone do not make direct contact with the brain.

The Hyoid Bone.

If I were a bone, I would probably be the hyoid bone, because it is the only bone that do not directly interact with other bones! It's kind of anti social, if you ask me.

Some things to remember about the hyoid bone is that it is underneath the mandible or the jaw bone and it is attached to the tongue and the muscles of the larynx for swallowing.

The Auditory Ossicles.

These are so interesting. They are so tiny, I wonder how they can transmit such great sounds to our brain so precisely.

A good way to remember the three muscles is through the word MIST, from lateral to medial position:

M- Malleus
I- Incus
ST - Stapes

The Vertebral Column.

For some reasons, I am having a hard time remembering the parts, specifically the differences and similarities between the different vertebrae.

The vertebrae can either be atypical or typical. The atypical vertebrae consists of the C1 (Atlas), C2 (Axis), Sacrum and Coccyx. What's interesting about the sacrum and the coccyx is that the Sacrum is a result of a fusion from 5 vertebrae while the Coccyx is a combination of 4 vertebrae. The rest is typical vertebrae (C3 - C7, T1 - T12, L1- L5). The curvatures of the vertebrae come from the posterior curves of the thoracic and the sacral region.

Some diseased vertebrae that I should know are Kyphosis, Lordosis and Scoliosis.





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Kyphosis is also known as the "hunchback" and is a  problem in the thoracic region as a result of the compression of fractures.

Lordosis, also known as the "swayback" is a problem in the lumbar region, commonly seen in pregnant women or people with "santa bellies"

Scoliosis or the lateral movement of the vertebral column, seen in the thoracic region as well. This is commonly seen in women.






Now on to the specific parts of the vertebral column (GASPPPPP!)

Let's start with the atypical.

The C1 also known as the Atlas has NO BODY, however it has superior articulating surfaces that, well... articulate with the occipital condyles of the skull. These also have transverse processes as well as transverse foramen.

The C2 also known as the Axis does not have a  body, but has a Dens or an Odontoid process, a superior articular facet, transverse processes, transverse foramen, a lamina, a pedicle and a bifed spinous process.

Now on to the typical vertebrae.

The C3 to C7 cervical vertebrae are small, but what sets them apart are the transverse foramen on each side that houses the vertebral arteries that supply blood to the brain. They also have bifed spinous process and a body.

The T1 to T12 thoracic vertebrae are medium in size. They have all the features - the body, the pointy spinous process, the superior articular facet (smooth surface) , a superior articular process (some sort of protrusion), transverse processes with costal facets and costal demifacets on the inferior side of the body. They also have a vertebral arch consisting of the lamina (beside the transverse process) and the pedicle (with the superior articular process). The vertebral foramen or canal houses the spinal column.

Lastly, the Lumbar vertebrae. The Lumbar vertebrae are large in size and has almost the same features as the thoracic vertebrae except that they have a very blunt spinous process and no costal demifacets.

Moving on to the thoracic cage.

The thoracic cage are fully developed by the age of 40. The three bones include the Manubrium, the body and the Xiphoid process.

The thoracic cage has true ribs (1 to 7), the false ribs (8-12) and the floating ribs (11-12) that are not connected to the costal cartilages.

The ribs are articulated with the vertebrae via the thoracic vertebrae's transverse costal facet and costal demifacets.

The Appendicular Skeleton.

 

 

The appendicular skeleton consists of the pectoral girdle, the upper extremity, the pelvic girdle and the lower extremities.

 

 

The Pectoral Girdle.

The pectoral girdle consists of two bones, the clavicle and the scapula. The clavicle has two ends, one end connecting to the sternum, called the sternal end and the acromial end, connecting to the acromion of the scapula. A personal aside, I think that the scapula is beautiful. It is so "edgy" and "spiney", but really versatile. The only downside is that it sacrifices stability for mobility,  so injuries are common in this part of the skeleton!

The Radius and Ulna.

The Radius and the Ulna are connected by the interosseous membrane made out of dense regular connective tissue.

 

Know all the parts.

 

The hand consists of carpals, metacarpals and phalanges (such a funny sounding word)

The carpals starting from the proximal  row from the radius side (lateral side) is the scaphoid, directly connected to the radius, then the lunate, directly connected to the ulna, the triquetrum on the most medial side, the pisiform which looks like a hook coming out of the triquetrum, the hamate, the capitate (right in the middle distal row), the trapezoid and the trapezium underneath the scaphoid.

 

The metacarpals are numbered from I - V. I as the pollex or the thumb and the pinky as roman numeral number V.

 

The rules for naming the hand bones: the bone number, metacarpal and left or right.

 

The rules for naming the phalanges: the bone number, proximal/middle/distal, phalange and left or right.

 

The Humerus.

 

The funny bone has a head, a greater tubercle, a lesser tubercle, a deltoid tuberosity on the lateral side, a coronoid fossa on the anterior side, a trochlea, epicondyles and an olecranon fossa on the posterior side.

 

 

 

The Pelvis or Os Coxae.

 

The Pelvis is formed by the age of 13 - 15, fusing the ilium, ischium and the pubis. See illustration above. My favorite drawing, by the way. lol

 

The Femur.

 The femur has a head, a greater and lesser trochanter, epicondyles on the sides, condyles and a linea aspera on the posterior side. Femur is the strongest, heaviest bone.

The Tibia and the Fibula.

These are fairly simple. The Tibia has a lateral and a medial condyle. A tibial tuberosity and a medial malleoli. The Tibia is the thickest skeletal bone. The Fibula has a head and a lateral malleoli.

Metatarsal.

The Metatarsals  consists of the medial, intermediate and lateral cuneiform, a cuboid, a talus and a calcaneus.

The Skull.

The fetal skull has a frontal bone, a parietal bone, an occipital bone, a temporal and a sphenoid bone just like an adult's skull. What sets them apart are their fontanelles. The fetal skull has an anterior fontanelle, a sphenoidal fontanelle, a mastoid fontanelle and a posterior fontanelle. They are very cool because they allow flexibility during birth and through the growth of a baby's brain.

I hope you enjoyed some of my sucky illustrations!

Have a great day,
M