Question

.Name and describe the structure separating vertebral bodies in the spine. Name three features of the ethmoid bone Describe primary vs secondary curvatures of the spine

Answer 1

1) Intervertebral discs are fibrocartilaginous discs which intervene between the bodies of adjacent vertebrae and bind them together. Their shape corresponds to that of the vertebral bodies between which they are placed. The thickness of the disc varies in different regions of the vertebral column. In the cervical and lumbar regions, the disks are thicker in front than behind, while in the thoracic region, they are of uniform thickness. The discs are thinnest in upper thoracic region and thickest in the lumbar region.

The discs constitute 1/5 of total length of vertebral column. Each disc is made up of following two parts:-

1. Nucleus pulposus is the central part of the disc. It is soft and gelatinous at birth. It is kept under tension and acts as a hydraulic shock absorber. With advancing age the elasticity of the disc is much reduced.
2. Annulus fibrosus forms the peripheral part of the disc. It is made up of a narrower outer zone of collagenous fibres and a wider inner zone of fibrocartilage. The fibres form laminae that are arranged in the form of incomplete rings.

Functions:- they give shape to the vertebral column. They act as a remarkable series of shock absorbers. Because of their elasticity, they allow slight movement of vertebral bodies on each other.

2) Ethmoid bone is a bone present in the head region of the body. It has three parts:-

1. Cribriform plate:- It forms the roof of the nasal cavity. Numerous olfactory Nerve fibres pierce it and give it a sieve like appearance.
2. Perpendicular plate:- It is a median plate like structure arising downwards from the cribriform plate. It forms upper 2/3 of nasal septum.
3. Ethmoidal labyrinth:- They are located on either side of perpendicular plate. They contain ethmoidal air cells (sinuses).

3)

Primary curvatures	Secondary curvatures
Thoracic and sacral	Cervical and lumbar
Convex forwards	Concave forwards
Formed before the birth	formed after birt
Same direction as that of curvature of fetal vertebral column.	counteract and compensate the primary curvatures.