Introduction to Skeletal System and Skull

Question 1

Principal Functions of the Skeletal System

Answer 1

• function of the skeletal system: bone tissues can store minerals (calcium, phosphurus) provide structure support, acts a site of attachment for muscles (part of locomotion or locomotor system) and forms the body, protects vital organs (brain, heart, lungs kidneys etc.), bone tissue contributes to making blood cells
• bone marrow is contained within the body or shaft of the bone which contributes to the formation of blood cells
  ◦ yellow (stores fat) and red bone marrow (active) - under the influence of certain hormones the yellow bone marrow can transform to the red bone marrow and can contribute to making more blood cells

Question 2

Different types of Bones: Classified based on their Shape

Answer 2

long bone: all long bones in our body sit vertically (only clavicle sits horizontal) - mostly found in upper or lower limb

flat bone: sternum - some skull bones are also flat bones

short bone: similar to cube shape - carpus (wrist bone) - carpal bones at the wrist are good examples of short bones - bones of ankle area are known as tarsal bones

irregular bone: do not have a specific shape - good example are vertebrae

sesamoid bone (small but very important): rather small bones that are contained within the tendon of muscles - largest sesamoid bone is the patella - have different functions but some include to protect the tendon of the muscle which contains it against the joint, when you move your knee the quadriceps helps extend the knee where the quadriceps tendon contains the patella, so the patella here is protecting the tendon from being rubbed constantly against your knee joint - patella increases mechanical efficiency of that muscle

Question 3

Axial and Appendicular Skeleton

Answer 3

• all the blue bones are the axial skeletons because they form the axis of the body
• all the other bodies are attached, appended to the axial skeleton so they are called appendicular skeleton (form skeleton of upper and lower limbs)
• for the upper and lower limb there are bones that are bridging between the axial skeleton and skeleton of the upper limb - scapula seen from behind and clavicle from in front - together there are connecting the skeleton of the upper limb to the axial skeleton which together is known as shoulder girdle (clavicle and scapula) - still part of the appendicular skeleton
• hip bone (left and right) which connect skeleton of lower limb to the axial skeleton which together left ad right are called pelvic girdle

Question 4

Skull - Lateral/Side View (what are the two craniums and how are the bones divided?)

Answer 4

• cannot use cranium and skull interchangeably - if you remove the mandible what is left is the cranium but if you include lower jaw that it is the skull
• 22 bones: most of these bones (14) are forming the skeleton of your face and 8 of them form the bony box that contains and holds the brain (neurocranium - holds part of the nervous system) - the remaining 14 that make your face are called viscerocranium
  ◦ some of the bones are paired while some are single

Question 5

What forms part of your upper jaw, lower jaw and cheekbone?

Answer 5

maxilla (paired), mandible (single) and zygomatic bone (paired - there is a suture that creates the border between maxilla and zygomatic bone)

Question 6

What are the three openings in the Orbital Cavity?

Answer 6

• within the large orbital (eye) cavity there are openings for nerves and blood vessels - superior orbital fissure
• bony canal is called the optic canal - circle opening - cranial nerve passes through it
• inferior orbital fissure
• 3 openings serve as passages for different nerves and blood vessels - all visible in the anterior view

Question 7

What connects to form the TMJ joint?

Answer 7

condylar process is easily palpable as it joins with the temporal bone to form the only moveable joint in the skull called temporal mandibular joint (TMJ) which is the only moveable joint - can feel it moving right in front of the ear

Question 8

What is the sagittal suture?

Answer 8

sagittal suture is the suture between parietal bones because it is in the sagittal plane

Question 9

What is the Lambdoid Suture?

Answer 9

lambdoid suture is the one between the parietal bone and occipital bone

Question 10

What is the Coronal Suture?

Answer 10

coronal suture - in that plane (separates the frontal and parietal)

Question 11

What are the two names of the places where sutures meet?

Answer 11

• the point at which the lambdoid joins sagittal is called lambda
• the point at which the coronal suture joints the sagittal suture is called bregma
• bregma is not fully ossified at birth to allow for growth of skull and brain so it is soft - these terms are only used when they are ossified (bregma and lambda)
• fontanel is what it is called when they are not ossified - anterior turns into bregma and posterior turns into lambda

Question 12

Superior View - Fossa (subdivisions of cavities)

Answer 12

fossa: a shallow depression on the bone surface, which may receive an articulating bone or act to support soft tissue structure
- this whole area is the cranial cavity and can be divided into 3 subdivisions
- the anterior cranial fossa is formed by frontal and sphenoid bones (form the floor)
- behind that is the middle cranial fossa where the temporal and sphenoid form it making sphenoid contribute to both fossae
- the posterior cranial fossa is primarily made by occipital bone