ANTHROPOMETRIC COMPARISM OF CEPHALIC INDICES BETWEEN YORUBA AND BENIN ETHNIC GROUPS RESIDING IN OKADA TOWN, EDO STATE

CHAPTER ONE

INTRODUCTION

1.1     BACKGROUND OF STUDY

Anthropometry (from Greek anthropos, “man” andmetron, “measure”) refers to the measurement of the human individual.Anthropometry involves the systematic measurement of the physical properties of the human body, primarily dimensional descriptions of body size and shape,it is the study of the measurement of the human body in terms of the dimensions of bone, muscle, and adipose (fat) tissue. Actual stature, weight, and body measurements (including skinfolds and circumferences) will be collected for purposes of assessing growth, body fat distribution, and for the provision of reference data. Anthropometry is the single most universally applicable, inexpensive, and non-invasive method available to assess the size, proportions, and composition of the human body. Today, anthropometry plays an important role  in industrial design, clothing design, ergonomics and architecture where statistical data about the distribution of body dimensions in the population are used to optimize products. Changes in lifestyles, nutrition, and ethnic composition of populations lead to changes in the distribution of body dimensions (e.g. obesity epidemic), and require regular updating of anthropometric data collections.` Cephalic index is a useful anthropometric parameter utilized in the determination of racial variations.It is also used to determine sexual differences especially in individuals whose identities are unknown. It is one of the clinical anthropometric parameters recognized in the investigation of craniofacial skeletal deformities and brain development because of its validity and practicality.Cephalic index is the most frequently investigated craniofacial parameter as it utilizes the length and breadth of the head which are useful indices in the study of secular trend, it is used to measure the size of the head,cephalic index gives an idea of how genetic characters are transmitted between parents, offspring, and siblings. It is inherited in a unitary fashion,isolated or syndromiccraniosynostosis, primary microcephaly, and hydrocephalus are pathological disorders which manifest with abnormal cephalic indices in addition to other features.Several studies have been carried out to classify head shapes based on cephalic index into four internationally acceptable categories that include DOLICHOCEPHALIC(<74.9),MESOCEPHALIC (75–79.9), BRACHYCEPHALIC (80.0–84.9), and HYPERBRACHYCEPHALIC (85.0–89.9). A study has shown that the people of Gurung community of Nepal of India are brachycephalic with cephalic index of 80.42.Bhils and Barelas are mesocephalic (76.98 & 79.80). The Iranian people are predominantly brachycephalic and hyperbrachycephalic. The research aimed at comparing the cephalic index between the two genders in a selected population and at determining a baseline value of cephalic index which could be vital in forensic, anthropological, and clinical studies. Cephalic index is an important parameter useful in establishing racial and sexual dimorphism, data obtained from such measurements have been very useful in differentiating people of different ethnic backgrounds, nutritional status, and gender. Several measurable anthropometric parameters or variables have been developed over the years for establishing possible differences amongst different groups.Cephalic index is one of such very useful measurable anthropometric variables used in physical anthropology to determine geographical gender, age, and racial and ethnic variations. Comparison of changes in cephalic index between parents, offspring, and siblings gives clues to genetic transmission of inherited characters or traits which play a role in forensic science.

Arguably, Cephalometry continues to be the most versatile technique in the investigation of the craniofacial skeleton because of its validity and practicality.Cephalometry is associated with the morphological study of all the structures present in the human head. Cephalometry is the scientific measurement of the dimensions of the head usually through the use of standardized lateral skull radiographs. Based on the above factors, anthropometric studies are conducted on the age, sex, and social or ethnic groups in certain geographical zones.Several studies have been conducted on the age, sex, and racial or ethnic groups in different geographical zones. These authors have sited various categories of cranium on the basis of head length, breadth, and index and described seven groups of crania.Okupe et al. [20] , in a comparative study of biparietal diameter (BPD) foetuses of some of the Nigerian ethnic groups and Caucasians, showed statistically significant differences until near term when the Nigerian foetuses showed consistently longer BPD.Cussenot et al. (1990) reported that skeletal measurements were made as the basis of foetal anthropometry and age determination. In a related study, cephalic index varied with advancing gestational age with the highest and lowest being 81.5 and 78.0 at weeks 14 and 28, respectively.A study has shown that the people of Gurung community of Nepal of India are brachycephalic with cephalic index of 80.42.Bhils and Barelas are mesocephalic (76.98 & 79.80). The Iranian people are predominantly brachycephalic and hyperbrachycephalic.Besides being a predictor of fetal death, early transvaginal measurement of cephalic index had been used for the determination of Down syndrome foetuses

GROSS ANATOMY OF THE SKULL

Thehuman skull is the bonystructure that forms the head in the human skeleton. It supports the structures of the face and forms a cavity for the brain . Like the skulls of other vertebrates, it protects the brain from injury.The skull consists of two parts, of differentembroyologicalorigin—theneurocranium and the facial skeleton (also called the viscerocranium). The neurocranium (or braincase) forms the protective cranial vault that surrounds and houses the brain andbrainstem. The facial skeleton is formed by the bones supporting the face.Except for the mandible,all of the bones of the skull are joined together by sutures (immovable) joints formed by bony ossification. The neurocranium has a dome-like roof called the Calvaria(skull cap and a floor or cranial base(Basicranium).

The neurocranium in adults is formed by a series of 8 bones;4 singular bones centered on the midline(Frontal,Ethmoidal,Sphenoidal and Occipital) and 2 sets of bones occurring as bilateral pairs(Temporal and Parietal). The bones forming the Calvaria are primarily flat bones (Frontal,Temporal and Parietal) formed by intramemebranous ossification of head mesenchyme from the neural crest. The bones contributing to the cranial base are primarily irregular bones with substantial flat portions (Sphenoidal and Temporal) formed by endochrondial ossification of cartilage (Chrondocranium) or from more than one type of ossification.

The Ethmoid Bone

The ethmoid bone is a singular porous bone that makes up the middle area of the viscerocranium and forms the midfacial region of the skull. It contributes to the moulding of the orbit, nasal cavity, nasal septum and the floor of the anterior cranial fossa.

Anatomy

The bone consists of a perpendicular plate and two ethmoidal labyrinths parts which are all superiorly attached to the cribriform plate. A smaller orbital part extends towards the orbit.

The ethmoid labyrinths lie on both lateral sides and contain numerous little cavities with ethmoidal cells which are referred to as the ethmoidal sinus. The labyrinths form two of the biggest structures in the nasal cavity: the superior and middle nasal concha. The hiatus semilunaris separates the ethmoid bulla and the uncinate process. It constitutes the connection between the frontal and maxillary sinuses to the anterior ethmoidal cells.

The perpendicular plate is a thin lamina which runs horizontally from the cribriform plate. Inferiorly it attaches to the septal cartilage of the nose and hereby forms part of the nasal septum.

The cribriform plate (Latin “cribriform” = perforated) lies within the ethmoidal notch of the frontal bone and forms the roof of the nasal cavity. As the name suggests it comprises numerous openings through which the olfactory fibers from the nasal cavity pass through to the anterior cranial fossa. The falxcerebri is attached to the crista galli (Latin “crista galli” = crest of the cock), a small vertical protrusion on top of the plate. The olfactory bulbs lie on two grooves lateral to the crista galli.

BORDERS

Because of its central location within the skull the ethmoid bone comes in contact with 15 other skull bones. The most important borders are: anteriorly to the frontal bone, posteriorly with the sphenoid bone and inferiorly to the vomer and inferior nasal concha.

Osseous Development

The ethmoid bone ossifies completely by endochondral ossification. In newborns.

SPHENOID BONE

The sphenoid bone is wedged between several other bones in the front of the cranium. It consists of a central part and two wing-like structures that extend sideways toward each side of the skull. This bone helps form the base of the cranium, the sides of the skull, and the floors and sides of the orbits (eye sockets). Along the middle, within the cranial cavity, a portion of the sphenoid bone rises up and forms a saddle-shaped mass called sellaturcica (Turk’s saddle). The depression of this saddle is occupied by the pituitary gland, which hangs from the base of the brain by a stalk. The sphenoid bone also contains two sphenoidal sinuses, which lie side by side and are separated by a bony septum that projects downward into the nasal cavity.

Occipital Bone

The occipital bone joins the parietal bones along the lambdoidal suture. It forms the back of the skull and the base of the cranium. There is a large opening on its lower surface called the foramen magnum, through which nerve fibers from the brain pass and enter the vertebral canal to become part of the spinal cord. Rounded processes called occipital condyles, which are located on each side of the foramen magnum, unite with the first vertebra of the spinal column. The junction of the sagittal and lambdoid sutures is called the lambda.

  1.2    STATEMENT OF RESEARCH PROBLEM

Cephalic Index is the percentile measurement of the length and breadth of the skull of an individual. Syndromiccraniosynostosis, primary microcephaly and hydrocephalus are pathological disorders which manifest with abnormal cephalic indices in addition to other features. Early trans-vaginal measurement of cephalic index used to determine Down syndrome foetuses

1.3 AIMS AND OBJECTIVES OF THE STUDY

1.To determine a baseline value which could be vital in forensic,anthropologicaland clinical studies.

2. To determine sexual differences especially in individuals whose identities are unknown.
3. To give an idea of how genetic characters are transmitted between parents, offspring and siblings.
4. To identify people by facial patterns and ethnic background.

1.4  SIGNIFICANCE OF STUDY

The findings of this study will generate a documented information on the Cephalic indices of the Yorubas and Benin tribe residing in Okada town, Edo state and provide useful data for statistical records. The findings will also serve as reference material for further study on this topic by contributing to the body of existing knowledge.

1.5 RESEARCH QUESTIONS

1.6 SCOPE OF STUDY

This study is carried out in a bid to compare the cephalic indices between 2 tribes(Benin and Yoruba) residing in Okada town, Edo State,using their biparietal and occipitofrontal diameters. Therefore, the spatial scope of study is in Okada town and the time scope which is the period under study is from April 2015-July 2015,though references will be made to earlier dates fro the purpose of recognizing previous research papers. The subjects of this study are Men and Women of the Benin and Yoruba tribes residing in Okada town, Edo state,between the ages of 25-40. The desired population for this research was gotten from visiting various homes and offices in Okada town,Edo state.

1.7   LIMITATION  OF STUDY

In the course of carrying out this research, it was limited by certain factors e.g. access to data from the area of respondents, restrictive nature of people to measurement of their cranial diameters. Notwithstanding the validity of the findings of this research will not be compromised.

1.8   OPERATIONAL DEFINITIONS OF TERMS

BIPARIETAL DIAMETER:The transverse distance between the protuberances of the two parietal bones of the skull.

OCCIPITOFRONTAL DIAMETER:The distance of the head from the external occipital protuberance to the most prominent point of the frontal bone in the midline.

ADULT:This is a person who is fully grown,matured and of age

SKULL:This is the bony structure that forms thehead  in the  human skeleton. It supports the structures of the face and forms a cavity forthe  brain and it protects the brain from injury.

 1.9 ORGANIZATION OF WORK

This research is divided into five chapters:

CHAPTER ONE:

This is the introduction which explains the problem of the research and provides background information to the study. Also, this chapter contains the aims and objectives, and significance of the study.

CHAPTER TWO:

This is literature review which reviews relevant scholarly works that have analysed the concepts of Cephalic indices.

CHAPTER THREE:

This is the methodology of study with data collection and analysis using the sample and technique chosen.

CHAPTER FOUR:

This is the summary of the results obtained from the data analysis

CHAPTER FIVE:

This is the concluding chapter with the discussion of findings, conclusion and recommendations made.