1. Which bone (yellow) is centrally located and joins with most of the other bones of the skull?
The bone labeled yellow is the sphenoid bone. Since it is centrally located, it joins most of the other bones. Looking at its structure, it has a complex shape. Hence, its name in Greek ‘sphenoeided’, which means wedge-shaped. It also looks like a butterfly or a bat with a central body and two lateral wings on either side, which gives it another name “wasp bone”. The sphenoid bone's primary role is to supply foramina and canals for neurovascular systems to and from the cranium.
2. What are the two mechanisms by which the bones of the body are formed and which bones are formed by each mechanism?
In general, the bone formation or the process that produces new bone tissue is known as Ossification. Digging deeper, there are two types of ossification that have different processes. During embryonic development, there are two methods of bone formation:
a) Intramembranous ossification
- Occurs in many bones of the skull and clavicles; flat bones in the skull
- Occurs on or within fibrous connective tissue membranes
- Bone develops directly from sheets of mesenchymal connective tissue
b) Endochondral ossification
- Occurs in most of the rest of skeleton
- The replacement of cartilage with bone
- The process by which bone tissue is formed in early fetal development
3.1 What are the synovial joints being described in the video?
a) Ball and socket joint
- The spherical head of one bone fits into the round socket in another
- Movement: Multiaxial (all axes); side to side, back and forth, rotation
- Example: Shoulder joint, hip joint
b) Hinge joint
- Angular movement is allowed in just one plane, like a door hinge
- Movement: Uniaxial (around axis only)
- Example: Elbow joint, ankle joint, joints between the phalanges
c) Pivot joint
- The rounded end of one bone fits into a sleeve or ring of bone (or ligaments)
- Movement: Uniaxial (around axis only)
- Example: Proximal joint between the radius and the ulna
d) Condyloid joint
- The egg-shaped articular surface of one bone fits into an oval concavity in another
- Movement: Biaxial (two axes); side to side, back and forth
- Example: Knuckle (metacarpophalangeal) joints
e) Saddle joint
- Each articular surface has both convex and concave areas, like a saddle for a horse
- Movement: Biaxial (two axes); side and side, back and forth
- Example: Carpometacarpal joints in the thumb
f) Plane (gliding) joint
- The articular surfaces are essentially flat, and only short slipping or gliding movements are allowed.
- Movement: Nonaxial (back and forth)
- Example: Intercarpal joints of the wrist
3.2 Which type of synovial joint allows for the widest ranges of motion?
- Ball and socket joints - Since it is the only synovial joint that is multiaxial, it allows for the widest ranges of motion. It can perform side to side, back and forth, and rotation motions.
References:
Cork, A. (2011, January 6). Synovial Joints. [Video file]. Retrieved from https://www.youtube.com/watch?v=VNbrvU7MgY0
Jamil, R. & Callahan, A. (2021, July 29). Anatomy, Sphenoid Bone. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK544308/#:~:text=The%20sphenoid%20is%20just%20one,but%20anterior%20to%20the%20occipital.
Kabi. (2012, April 21). Skeletal System : Bone Formation ( Intramembranous Ossification & Endochondral Ossification)". [Video file]. Retrieved from https://www.youtube.com/watch?v=p-3PuLXp9Wg
Marieb, E. & Keller, S. (2018). Essentials of Human Anatomy & Physiology. New York, NY: Pearson Education
OpenStaxCollege. (2013, March 6). Bone Formation and Development. Retrieved fromhttp://pressbooks-dev.oer.hawaii.edu/anatomyandphysiology/chapter/bone-formation-and-development/
WitmerLab. (2011, August 11). Human skull - exploded skull with bones labelled, based on CT scanning. [Video file]. Retrieved from https://www.youtube.com/watch?v=FrpVzSK23Q0