Exam 2: Bioarchaeology Potential Questions
#1, 2, 3
1. Describe the general growth and development of from subadult to adult. No need to emphasize
the categorization of age. Outline general health indicators that can interrupt this process.
2. Explain DoHAD, breakdown of osteological paradox, heterogeneity of frailty
3. Outline one to two theoretical approaches that bioarchaeology uses to integrate the social-
environmental context (i.e., life-course, biocultural, mother-nexus, and embodiment).
Question 1:
The following will introduce the general development of the skeletal system, then proceed into a
review of the fundamental concepts and mechanisms that regulate each region's overall development,
followed by the mechanisms and factors that affect these processes and the potential general health
indicators that have been used to assess population health in the past.
Skeletal Development:
Gross Function and Anatomy
Bone is a composite material composed of inorganic material (~60%), organic (~25%), and water
(~15%), and the bone components differ in the various bone types and maturation stages; however, all
bone is composed of the same essential elements: cells (osteoblast, osteoclasts, osteocytes), matrix
(organic & inorganic components), external (periosteum) and internal (endosteum) membranes, and bone
marrow (red- hematopoietic, and yellow-fat storage) (Lynnerup and Klaus, 2019; Cunningham et al.,
2016).
Bone can be understood as tissue and an organ that serves multiple functions. These functions
include protecting soft tissue structures and supporting the architecture of ligaments and muscle
attachments to aid mobility, storage, and the site of RBC production and innate immune system cells
(Lynnerup and Klaus, 2019). The bones of a skeleton can also be classified in terms of shape: (1) Long
bones, (2) Short bones, (3) Flat bones), (4) Irregular bones) (Baker et al., 2005). The type of bone can
provide insight into the type of vascularization, biomechanical properties, and metabolic function of the
element in question, which can frame the microenvironments that potential pathogens may prefer, as well
as the type and duration of patterns of biomechanical influence one could expect (Lynnerup and Klaus,
2019).
The anatomy of the long bone will serve as an example of the different areas of the bone; the long
shaft is called the diaphysis, which is the product of the primary center of ossification; this area is
followed by a growing zone at the proximal and distal ends called the metaphyses, next is the
cartilaginous growth plate that joins the additional bone segments known as the epiphyses which are the
secondary centers of ossification. Once growth is complete, the growth plate will fuse the metaphysis and
epiphysis, starting with forming a mineralization bridge that eventually replaces the cartilaginous growth
plate with bone (Cunningham et al., 2016). This is known as an epiphyseal union, and the timing of
fusion/union is used to signify normal cessation of growth (biological age) or to potentially identify
premature fusion due to pathological disturbance (Cunningham et al., 2016). These unions can occur
anywhere from mid-to-late fetal life to the end of the third decade and are subject to genetic, hormonal,
and environmental variations (Cunningham et al., 2016).
, Also of note is that within the diaphysis, there is a medullary cavity, which is covered by the
endosteum, and the external surface of the bone is covered in the periosteal membrane (periosteal
envelope). The inner layer of the periosteum is the site of appositional (circumferential- expanding in
width/diameter) growth during development, and the outer layer acts as the anchor for fibers that facilitate
muscle attachments (Sharpey's fibers) (Lewis, 2006).
Bone Tissue Type
There are two bone tissue types: compact (cortical) and cancellous (trabeculae or spongy) bone.
Compact bone: forms the smooth surface of all bone and is composed of densely layered lamellar
tissue. The initial formation of compact bone is known as woven bone (primary bone, immature
bone, or fiber bone), which is characterized by its rapid formation and disorganized meshwork
pattern and is comparatively structurally weak to the more mature form known as lamellar bone
(secondary bone and mature bone). The transformation is the result of continuous remodeling of
the initial primary deposition of woven bone into the secondary or mature form (Cunningham et
al., 2016; Lynerup and Klaus, 2019; Lewis, 2006). Woven bone is typically formed during the
growth and development of perinates, infants, and later periods and can be seen as part of a
pathological or healing process (healing process-remodeling) (Lewis, 2018).
Cancellous bone: forms in the space between the external and internal surface of flat bones,
irregular bones, and the epiphyses of long and short bones. It is characterized by a network of thin
bone beams known as trabeculae. The orientation of these trabeculae plays a biomechanical role
in reflecting the transmission of force through the bone.
Types of ossification
Intramembranous ossification results in a bone that is characterized as either compact or diploic,
whereas endochondral ossification results in the bone that can be characterized as trabecular or cancellous
(cranial and postcranial bone) (Cunningham et al., 2016).
Endochondral Ossification
Bone that is derived from hyaline cartilage (via endochondral ossification) is first pre-formed in a
cartilage template(model) that is derived from mesenchyme tissue; each template develops through both
appositional and interstitial (multifocal or longitudinal) growth (Lewis, 2018). This type of ossification is
found in both the cranial and postcranial skeleton. Appositional growth in the initial pre-form model, is
where cartilage is layered on the surface of the model, expanding in width on the periosteal margin. Once
the model is formed, the process begins to ossify the cartilage, allowing the bone to grow in diameter
(Lewis, 2006). Interstitial or longitudinal growth follows this same concept except that it expands the
model in length.
Intramembranous Ossification
Bone derived via intramembranous ossification is characterized by the fact that it does not use the
hyaline cartilage model as an intermediary stage (Lynnerup and Klaus, 2019). Instead, the bone formation
occurs directly in the membranous structure where osteoid (bony matrix) is produced and laid down
radially, projecting outwardly from what will become the center point of the future bone. This type of
formation is seen in most of the flat bones of the cranial vault and facial bones and the initial sections of
the clavicle (Lynnerup and Klaus, 2019).
, General Development
The skeleton development begins around the sixth and seventh week of gestation, utilizing both
intramembranous and endochondral ossification. The number of non-adult bones ranges from 156 to 450,
changing as ossification centers appear and fuse elements. For example, at birth, there is a total of 156
skeletal elements, and as cartilage models begin to ossify, the number of elements more than double to
332 by the age of 6, and as development continues and maturation is reached, epiphyses begin to fuse,
and numbers begin to decrease to a total of 206 elements for the adult (Lewis, 2018).
Throughout the growth, depending on the type of bone in question, both longitudinal and
appositional growth is employed in a process known as bone modeling, where the overall shape and size
are formed. This process is continually edited by a process known as bone remodeling, where the bone is
removed or added as the situation requires. Bone health can be evaluated by the degree of balance
between these mechanisms, and when the equilibrium is disrupted, this is indicative of a potential
pathological insult.
General overview
At birth, much of the basicranium is still composed of the cartilage model, and the bones of the
neurocranium are separated by broad membranous zones (fontanelles). These fontanelles' presence allows
for the brain's rapid expansion during the first few years of life. These cartilaginous membranes gradually
fill in by ossification until an ossified structure remains. The intramembranous cranial bone growth is
highly coordinated with brain growth; therefore, abnormalities (growth disturbances) can result in missing
structures, abnormal expansion in certain areas, and potential premature closure of sutures resulting in
cranial shape abnormalities (Lynnerup and Klaus, 2019). The rest of the skull forms through both
endochondral ossification and a combination of the two. The spine also follows this combination of
intramembranous and endochondral ossification. The long bones are the last to reach adult diameter
proportions, with the completion of growth in the pelvis, scapula, and clavicle following.
Puberty and Growth Spurt influence
During the adolescent growth spurt, secondary sexual characteristics begin to develop, which
correlates with the later developing skeletal elements demonstrating more sexually dimorphic traits
(Lewis, 2006). The sex of an individual also impacts the overall growth velocity, with females first
accelerating and arresting younger, and males' growth spurt happening later and for longer during
puberty. The range for females is tied to the onset of menarche, which varies spatiotemporally (Lewis,
2006). This range has been linked to social conditions, nutrition levels, and potential disease insults, all of
which should be considered when estimating the growth and age of individuals in the past (Lewis, 2006).
- Critique to the concept that “childhood” is a natural period of life (Hoernes et al. 2021)
- varied notions of childhood
- Duration
- social integration points
- cultural significance
- Cultural assumptions vs. assumptions of universality
