ANTC47H3 Lecture Notes - Synovial Joint, Cartilaginous Joint, Hyaline Cartilage

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13 Sep 2013
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ANTC47 Lecture 2- September 11, 2013
CHAPTER 4: Bone Biology
Introduction
1) Human skeletal variation can be studied on various levels:
Population Level: skeletal variation within-and among populations
oSuch as population variation in stature, or craniometric variation
oMu= population average
oPopulation distribution: Mu 1 and Mu 2 -> so talk about variation
between two populations, or among three populations, etc.
Individual Level: variation between left and right limbs in measures of
robusticity (how strong it is) can tell us something about handedness, or
variation among muscle markings on bone can tell us something about
activity patterns.
Elemental and molecular level: can tell us about genetic relationships
such as paternity and even diet.
2) Bones act as the essential mechanical components of the musculoskeletal system.
They support and protect soft tissue
They anchor muscles, ligaments and tendons
They act as rigid levers upon which muscles act to produce movement
Act as production centers for blood
Storage of fat and calcium
2) The shape or morphology of bones change during growth and development, or
ontogeny, through remodeling, which is the process of laying down depositing
new bone in certain areas while at the same time resorbing, or removing bone in
other areas.
4.1 Variation
1) Humans exhibit variation in skeletal and dental morphology, bone chemistry, and
DNA. This variation is what biological anthropologists are interested in, it allows
the osteologist to identify sex, age and population affinity.
2) There are four factors leading to skeletal variation:
a. Ontogeny: there is a great deal of variation in size and shape during
growth and development.
b. Sex: Humans, like other primates, are sexually dimorphic. There is
variation between males and females in size, shape and size-dependent
shape. This variation allows osteologists to determine the sex of a skeleton
(by looking at the variation of morphology, we can determine it’s sex).
c. Geographic or population based variation: attributes of the human
skeleton can vary from one location to another due to adaptations to
specific environments. Example: crural index varies with latitude.
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Populations also vary in skeletal size and shape (Bergman’s rule: as we go
higher in latitude, body size increases; Allen’s rule: the relative length of
limbs decreases-> as we increase in latitude, it gets colder, so it’s an
adaptation to conserve body heat, or alternatively, those who are near the
equator are taller, which means they can dissipate body heat more easily)
d. Individual or idiosyncratic variation: look at the symmetry of your face.
3) Understanding the normal range of skeletal variation with and among human
populations, as well as with and among closely related species or subspecies is
essential for identifying new species in the fossil record. A typological approach,
one that employs typology (the practice of choosing one individual to characterize
a whole species), without consideration of the normal range of variation can result
in misguided and inaccurate taxonomies, or species identifications.
-> variation is the most important component of learning evolution
4.2 Facts About Bone
1) Bone is a relatively light-weight, yet very strong, material that is a composite
of collagen (which is essentially protein) and mineral (hydroxyapatite-> a form of
calcium phosphate). Bone is living and dynamic tissue which is able to regenerate
itself.
2) The skeleton is subjected daily to mechanical forces such as compression,
bending, shear, and torsion. These forces result in bone remodeling. Bone is
deposited where it is needed and resorbed where it is not (Wolff’s Law). -> laying
down bone and taking bone away where it’s needed (ex. as you walk, you put
mechanical forces on your skeleton, such as on your femur or back)
> axial loading: depends on body weight (greater body weight means larger
mechanical force) ; more axial loading means thicker bones (bone is laid down on
the outside; the shape of the axial changes); it changes faster for males; as long as
the diameter increases, the bone gets stronger
3) The study of these forces and how they affect morphological and structural
change in bone is part of the field of biomechanics.
4.3 Bone as Elements of the Musculoskeletal System
1) A connection between different skeletal elements or bones is called a joint. These
joints are articulations and connect the different bones with ligaments and
cartilage.
2) Muscle attaches to bone by tendons, which are tightly-packed bundles of collagen
fibers (organic component of bone).
3) The most common type of joint is a synovial joint which comprises articular
cartilage (hyaline cartilage). The joint is encapsulated and contains synovial fluid
which serves to reduce friction in the joint and to provide nutrients for the
articular cartilage.
4) There are different types of synovial joints that are defined based on their
geometry and motion, such as a spheroidal, or ball-and-socket joints (e.g., hip),
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