Chapter 39 Objectives [skeletal]
Friday, February 27, 2009
7:01 PM
1. Provide a general definition of a skeleton
a. General Definition
1. Skeletal system forms the framework of the body. It functions in locomotion
and transmitting and transforming mechanical forces generated by muscle
contraction into the variety of motions that animals make.
2. Name, describe, and give examples of the three types of skeletons found in animals.
AND
3. Describe advantages and disadvantages associated with each type of skeleton.
a. Types of Skeletons
1. Hydrostatic – made of fluid-filled body compartments
a. How it works: - Fluid in a closed compartment of the body is held under
pressure. When muscles in the compartment wall contract, they push
against the tube of fluid. Because fluid cannot be compressed, the force is
transmitted through the fluid, changing the shape and movement of the
body.
b. Location: gastrovascular cavity
c. Advantages and Disadvantages:
i.
Permits only crude mass movements of the body or appendages –
Delicate movements are difficult. Because force travels equally in all
directions. More sophisticated hydrostatic skeletons permit freer
movement because animals like annelids are segmented and each
segment can move independently.
d. Examples: elephant trunk, octopus, cnidarians, annelids, coelem,
pseudocoelem, gastrovascular cavity, membrane bound cuticle.
2. External
a. Definition – an external lifeless shell. Depositied atop the outer epithelial
lining
b. Composition – (Mollusks) – calcium carbonate secreted by mantle;
(Arthropods) – nonliving cuticle that contains the polysaccharide chitin
c. Advantages and disadvantages – provides protection and a retreat.
Transmits forces – provides a place for muscles to attach. However it does
not accommodate growth so arthropods must molt – Ecdysis- (Make a
new exoskeleton that is bigger so they have room to grow) must have
segmentation to allow the abdomen to expand while eating.
3. Internal
a. Definition – living internal skeleton consists of plates or shafts of calcium
impregnated tissue
b. Advantages – grows with the animal, support and protection, some bear
spines for protection, internal vertebrate skeleton provides support and
protection and transmits muscle focus—system of levers that transmit
forces.
i.
Our lever system is not efficient.
c. Examples: echinoderms and chordates
i.
ii.
iii.
Echinoderms have spines and plates of calcium salts embedded in
the body wall beneath the epidermis
Sponges have spicules that are internal skeletons and provide
support.
Deuterostomes have internal skeletons
4. Name and describe the divisions of the tetrapod skeleton
a. Tetrapod skeleton
1. Having four “feet” – limbs
2. Amphibians, birds, reptiles, mammals
3. Major divisions
a. Axial – located along the central axis of the body
i.
Consists of skull, vertebral column, ribs, and sternum
i.
Vertebral column – supports body and bears its weight
1. 24 vertebrae and 2 bones composed of fused
vertebrae (sacrum and coccyx)
2. 7 cervical vertebrae, 12 thoracic vertebrae, 5
lumbar vertebrae, 5 fused vertebrae make up
sacral region and the coccygeal is also made of
fused vertebrae
ii.
Rib cage – bone “basket” formed by the sternum, thoracic
vertebrae, and 12 pairs of ribs
1. Protects internal organs of chest, supports chest
wall preventing it from collapse
2. Each pair of ribs are attached to vertebrae (1st 7
to sternum, next 3 by cartilage, last 2 are
“floating ribs”
b. Appendicular – bones of the limbs and the pectoral and pelvic girdles that
connect limbs to the axial skeleton
i.
Pectoral girdle – 2 collar bones or clavicles, 2 scapulas
ii.
Pelvic girdle – Pair of long bones each composed of three fused
hipbones and is loosely/flexibly fused to the vertebral column by
muscles
i.
Lumbar region is the only fused region with axial and
appendicular skeleton
5. Describe the structural features and functional differences between dense and spongy bone
a. Spongy Bone
1. Location - interior to the thin shell of compact bone
2. Function - provides mechanical strength
3. Structure - network of thin strands of bone a. space filled with bone marrow where blood cells are made
b. Amount of spongy bone varies on location
c. Put together in branches called trabeculae.
b. Dense (compact) bone - smooth outside
1. Location - outer shell, near surface of the bone
2. Structure - interlocking spindle shaped units called osteons
3. Function - provides great strength
a. Has structural organization/form
6. List the anatomical regions of a long bone
a. Regions of a long bone
1. Epiphysis - each expanded end (very ends)
2. Metaphysis - a disc of cartilage between epiphysis and diaphysis
3. Diaphysis - main shaft of a long bone
7. List the types of bones based upon shape
a. Classification
1. Long - longer than they are wide
a. Thin shell of compact bone and a filling of spongy bone that contains marrow
b. Have central canal with yellow marrow (fatty connective tissue)
c. Red Marrow produces red blood cells
i.
Femur
ii.
phalanges
2. Short - more cuboidal
a. Carpal and tarsal bones
3. Flat
a. Sternum and cranial bones
4. Irregular - no defined shape; have spinous projections, foramen, etc.
a. Vertebrae
5. Seasamoid - embedded in tendon or ligament
a. 2 patella and the hyoid bones
8. Name and describe the joints between bones
a. Joints between bones
1. Fibrous joints
a. Synarthrosis - immovable joints
i.
Sutures of the skull
b. Amphiarthrosis - slightly moveable
i.
Ligaments holding adjacent bones together
ii.
Hyaline cartilage at synovial joints
i.
Rib cage
ii.
Prevents "wear and tear"
iii.
Fibrocartilage- found at pubis in the pelvis
2. Diarthrosis - freely moveable
a. Synovial joints - have synovial fluid (lubrication)
i.
Hinge - elbow (limited)
ii.
Ball and socket - good range of motion
i.
Hip more limited than shoulder -- pelvis partly blocks motion as well
as the greater trochanger and the deep socket -- great stability.
9. Distinguish between and give examples of cranial and facial bones
a. Cranial and Facial bones
1. Definition a. Cranial bones house/touch the brain and facial bones do not
b. Together they form the skull
2. Cranial bone examples
a. Frontal - (forehead) - the height considered to distinguish male or female
(females are more rounded.
b. Parietal - above ear
c. Temporal - in front of ear
d. Occipital - back of head - can disconnect brain from attachment point if you hit
it
i.
Men have a pronounced ridge
3. Facial bones
a. Nasal
b. Lacrimal - smaller bones - tear duct goes through edges
c. Mandible and maxilla
i.
Mandible is moveable
ii.
Maxilla is immovable
10. Describe and distinguish between echondral bone formation and intramembranous bone
formation. Give examples of bones formed by each ossification process.
a. Endochondral bone formation (long bones)
1. Cartilage templates
a. A bone begins to ossify in its diaphysis and secondary sites of bone production
develop in the epiphysis.
i.
The part of bone between ossified regions can grow and eventually fuses
ii.
Spongy bone forms first then the compact forms around it
b. Grow blood vessels to cartilage that delivers cells that will form bone (replace
cartilage with actual bone)
i.
Growth: have chondrocytes at epiphyseal plate (growth plate)
i.
Put down cartilage then replace it w/ bone (spongy first then dense)
ii.
When the epiphyseal plate becomes the epiphyseal line you're
done growing
iii.
If you break the growth plate, growth stops.
ii.
Cells:
i.
Osteoblasts - build
ii.
Osteoclasts - cut up, break down/reabsorb bone
iii.
Bones are dynamic -- the skeleton is replaced once every 10 years.