Answers-1, BIO 3220, Introduction to Skeletal System


1. Explain the importance of learning about the skeleton.
The skeleton maintains a body shape, protects vital organs, and provides a system of muscle levers that allow body movement. The skeleton contains bone marrow, the blood-forming tissues of the body. Bone marrow stores needed minerals such as calcium and phosphorus and releases them into the blood. It is important to start learning about bones from an early age, as it is essential to obtaining peak bone mass. It is better to make dietary and lifestyle changes earlier in life and prevent osteoporosis becoming a disease of future generations.

2. Name the hard tissues. Review their embryologic origins.
Enamel – calcium phosphate, calcium hydroxide present; permanent external tissue make from ectoderm; hardest tissue of the body; 3% organic fibers
Dentin(e) – formed from mesoderm; similar to bone in make-up, but harder; ~ 25% organic fibers
Bone – usually occurs internal to dentine; organic fibers; calcium crystals; usually has cells present; derived from mesoderm

3. List the constituents of bone.
Collagen, hydroxyapatite crystals, water and mucopolysaccharides, osteocytes

4. Compare compact, spongy, dentin, acellular, membrane, dermal and replacement bones.
Compact bone – noncancellous portion of bone that consists largely of concentric lamellar osteons and interstitial lamellae; dense
Spongy bone – cancellous Bone in which the spicules form a latticework, with interstices filled with embryonic connective tissue or bone marrow
Dentine – main, calcareous part of a tooth, beneath the enamel and surrounding the pulp chamber and root canals
Acellutlar bone – bone that is not supported by nor contains living cells
Membrane/dermal bone – bone that develops within membranous tissue without previous cartilage formation
Replacement bone – endochondral bone that is ossified internally, by replacement of cartilage

5. Compare hyaline, fibrous, elastic and calcified cartilages.
Hyaline cartilage – most widespread cartilage type, in adults forms articular surfaces of long bones, rib tips, rings of trachea, and parts of skull; mostly collagen; name refers to glassy appearance; in embryo, bones form first as hyaline cartilage, later ossifies
Fibrous cartilage – have lots of collagen fibers; found in intervertebral discs, pubic symphesis; grades into dense tendon and ligament tissue
Elastic cartilage – springy and elastic; found in internal support of external ear and in epiglottis
Calcified cartilage – cartilage in which calcium salts are deposited in the matrix; it occurs prior to replacement by osseous tissue and sometimes in aging cartilage

6. Identify the axial and appendicular skeletons.
Axial skeleton – the part of the skeleton that includes the skull, vertebrae, sternum and ribs
Appendicular skeleton – the part of the skeleton that includes the pectoral girdle, pelvic girdle, and the upper and lower limbs