And as much as I love the tv show ‘Bones’ I’m actually going to talk about the skeleton. You can check out the show on your own time, it’s on tonight–Mondays on Fox.
So I am going to assume that you have seen a human skeleton at least once sometime over your lifetime. Could be a mistake on my part, but let’s roll with it. Better yet, here’s a human skeleton:
Now you’ve seen one. I have found quite a few interesting books that have made me geekily (that is a word. Means the geek in me is the part I am talking about) happy like finding a copy of Shirley A Jones Pocket Anatomy & Physiology. I adore this little thing and my step-son (and his girlfriend) have threatened to “steal” this book from me. Well I guess I better get down to some bone stuff instead of gushing about materials I have found and teaching you new “words”.
Speaking of new words, let’s cover some vocab words so you don’t get too lost in this post.
Anatomical position: Person stands erect, face directed forward, upper limbs hanging to the side with palms facing forward.
Supine: Person lies face upward.
Prone: Person lies face downward.
Superior: A structure above or higher than another.
Inferior: A structure below or lower than another.
Anterior: The front of the body.
Posterior: The back of the body.
Ventral: Toward the front of the body (syn. with anterior).
Dorsal: Toward the back of the body (syn. with posterior).
Cephalic: Closer to the head than another structure.
Caudal: Closer to the tail bone than another structure.
Proximal: Closer to the attachment point than another structure.
Distal: Further from the attachment point than another structure.
Midline: Dividing the body into right and left sides.
Lateral: Away from the midline of the body.
Medial: Toward the midline of the body.
Superficial: Towards the surface or on it.
Deep: Away from the surface; internal.
Sole: The inferior (plantar) aspect or bottom of the foot.
Palm: The flat of the hand, excluding the thumb and other fingers.
Planes of the Body
Frontal (coronal): Runs vertically and divides the body into anterior and posterior portions.
Sagittal: Runs vertically through the body and parallel to the median plane.
Median or Midsagittal: Runs sagittally through the midline and divides the body into right and left halves.
Transverse (horizontal): Runs parallel to the ground and divides the body into superior and inferior portions.
Longitudinal: Intersects the long axis of a structure or organ.
Cross-section: Intersects the long axis of a structure or organ at a right angle.
Oblique Section: Intersects the long axis at other than a right angle.
Terms of Movement
Flexion: Decrease in the angle between bones or body parts.
Extension: Increase or straightening of the angle between bones or body parts.
Abduction: Movement of the limbs away from the median plane
Adduction: Movement of the limbs toward the median plane.
For me, visual aides often help me understand words, so here is a visual of most of the words above. Clicking on them will get you larger images (which were found on the Internet using Google) and clearer wording.
We have 206 bones of all different sizes and lengths that make up the structure for which muscles, ligaments tendons and other various connective tissues attach. All bones have names and functions and are grouped together depending on where they are found in the body. I won’t go into detail much on these aspects quite yet as we have just touched upon labeling a few bones so far and won’t be going into such detail as I show in these wonderful pictures I find roaming alone on the internet.
The skull alone is composed of 22 outwardly visible bones and three ear ossicles on each side that cannot be seen easily. All these bones with the exception of the lower jaw, articulate tightly at suture lines so there is very little movement between adjacent bones. There are four topical areas of the cranium, first concerns the bones that make up the cranial skeleton and various prominences and other features visible on the exterior surface. Second deals with the sutures, which separate these bones. The third involves the landmarks on the cranium and finally the fourth, various sinuses within bones of the skull. These deserve consideration because of their value in developing positive identification of individuals.
I know there are a lot of parts labeled on these two skull pictures, but the ones I’ll be focusing on for class are:
For the anterior view of the skull (that’s the one to the left <—); frontal, supraorbital tori, zygomatic (both), maxilla, nasal conchae, nasal, vomer, mandible, and mazilla.
For the lateral view of the skull (that’s the one to the right –>); lacrymal, ethmoid, parietal, occipital, squamous, temporal, external auditory meatus, mastoid process, sphenoid, temporomandibular joint (TMJ).
Hope you manged to find those on the two pictures (remember click for bigger picture!) And for a bit of fun, the mastoid process in males stick out more than the ones in females, this that area of bone that when you wear a head band that is tight it will rub up against and annoy you.
They broke the skeleton it’s self down to two main parts; the skull, the hyroid, the vertebrae (7 cervical, 12 thoracic, and 5 lumbar), the ribs (12 on each side), the sternum, the right and left scapulae and clavicles and the pelvis form the axial skeleton. The shoulders and upper extremities and hips and lower extremities form the appendicular skeleton. And yes, I have a picture! I’m quite visual if you have failed to noticed this.
As I mentioned earlier bones have functions, there are bones that support the body much as a framework of steel girders supports a modern building, bones that are hard bony boxes that enclose and protect delicate structures as like the skull protecting the brain, bones and joints work together as levers. Muscles are anchored firmly to bones as muscles contract and shorten, they pull on bones, producing movement at a joint. Hemopoiesis a term for blood cell formation, is a vital process that is carried out by red bone marrow. In an infant’s or child’s body virtually all bones contain red marrow as the body ages much of the red marrow is transformed into yellow marrow which is an inactive fatty tissue. Main bones in an adult’s body that contain red marrow are those of the chest, spinal column, skull base, upper are and thigh. Red marrow forms blood cells (red blood cells, some white blood cells and platelets). Bones are the major storage depot for calcium, phosphorus and certain other minerals. Homeostasis of blood calcium concentration, essential for healthy survival, depends largely on changes in the rates of calcium movement between blood and bones.
As with bones, there are many types of joints; fibrous, cartilaginous, synovial, gliding to name a few and they have their own type of movements, but I won’t get into those as they are numerous and by the time forensics get to the body, these are generally pretty well gone.
Because of the way bones fuse and change as a person grows using them to determine age can be an easy process given you know what you are look for and at. Juvenile bones are a bit trickier as they are right in the middle of being a child and being an adult. Bones can tell you what sex the person is, if a female has given birth and what type of ancestry the person comes from. They tell what diseases a person had and sometimes even what killed the person. However one must be careful; most of us are quite used to seeing plastic skeletons hanging around labs and biology classes. What those skeletons do not tell you is the fact that bones like the scapula (shoulder) and os coxae (hip bones) can thin with age and might develop small holes in them where muscles attach themselves that can and have been mistaken for small caliber rounds. Never make final assumptions based upon a single glance. I am sure I don’t need to tell many of you of that, but it is a nice reminder not only in forensics, but as a general rule throughout life as well.
Animal or human? Good question! I know there are a few tell-tale signs like on the scapula, the suprascapular notch and the bone that has the coracoid process are mainly human, animals do not have these. The easiest way to show the difference (besides flooding the post with more pictures) is tables. So here are four tables showing the differences between animal and human bones. The first table talks about the differences of the cranium, which generally are much easier to discern than other bones.
Table 1. Differential Skeletal Anatomy of Humans and Animals:Cranium
|Large bulbous vault, small face||Small vault, large face|
|Vault relatively smooth||Pronounced muscle markings, sagittal crest Inferior|
|Inferior Foramen Magnum||Posterior Foramen Magnum|
|Chin present||Chin absent|
|Orbits at front, above nasal aperture||Orbits at sides, posterior to nasal aperture|
|Minimal nasal and midface projection||Significant nasal and midface projection|
|“U”-shaped mandible (no midline separation)||“V”-shaped mandible (separates at midline)|
Table two talks about post-cranium differences, that is the arms, legs, pelvis and vertebra.
Table 2. Differential Skeletal Anatomy of Humans and Animals: Post-cranium
|Upper limbs less robust||Robust upper limbs|
|Radius and unla are separate bones||Radius and ulna often fused|
|Large, flat and broad vertebral bodies with short spinous processes||Small vertebrtal bodies with convex/ concave surfaces and long spinous processes|
|Sacrum with 5 fused vertebrae, short and broad||Sacrum with 3 or 4 fused vertebrae, long and narrow|
|Pelvis is broad and short, bowl-shaped||Pelvis is long and narrow, blade-shaped|
|Femur is longest bone in body, linea aspera is singular feature||Femur is similar length to other limb bones, linea aspera double or plateau|
|Separate tibia and fibula||Tibia and fibula are often fused|
|Foot is long and narrow, weight borne on heel and toes||Foot is broad, weight borne mainly on toes|
Table three is all about the teeth, also known as dentition which I will cover in a different post.
Table 3. Differential Skeletal Anatomy of Humans and Animals: Dentition
|Omnivorous||Carnivorous; Herbivorous; Omnivorous|
|Dental formula 2:1:2:3||Basic dental formula 3:1:4:3|
|Incisors (maxillary) are larger than other mammals||Horse maxillary incisors are larger than human incisors|
|Canines small||Carnivores have large conical canines; Herbivores have small or missing canines|
|Premolars and molars have low, rounded cusps divided by distinct grooves||Carnivores have sharp, pointed cheek teeth; Herbivores have broad, flat cheek teeth with parallel furrows and ridges|
And finally my last table, differences in bone macrostructure, that is looking at the bone under a microscope.
Table 4. Differential Bone Macrostructure of Humans and Animals
|More porous cortical bone||Less porous cortical bone|
|1/4 thickness of diameter of long bone||1/2 thickness of diameter of long bone|
|Diaphyseal trabecula present||Diaphyseal trabecula absent|
|Thick diploe in cranial vault bones||More compact cranial vault bones|
It is a good idea to know these differences and when human bone is found to leave it right where it lays. Be prepared to have various bones shoved under your nose once people find out you study forensics or even anthropology as it is the second thing people do after finding out. First thing is to ask what exactly it is you do as there are not many who know what either profession actually does. For example when I told my mom I was going to major in Anthropology after I get my Associates in Web Technology she asked what it was and sadly the easiest way I could explain it was with two words. Indiana. Jones. Yes, I know all about how Indiana Jones isn’t really an archaeologist, in fact I did a paper on it last term–got full marks on it as well. But if you knew my mother, you would understand how sometimes the simplest explanations are the best. Now on whether she actually understands what it is the character is suppose to do, that is a whole ‘nother story and I am sure that someday I will regret using Indy as an example. But…until then…
I found some great web-sites while looking for the pictures you find in this post. One great one is the Flashcard Exhange; you can find flashcards for almost any subject that you can save and print to use to study. I snagged some of the skeleton ones to print out and use later on. Academic Kellogg has some great information on the skeleton system and perhaps more if you look around their site. Check them out! And as a side link, not used for any information here but because I know people go ape over, well apes, here’s the San Diego Zoo’s Ape Cam. Enjoy!
Until next time, men and women have the same number of ribs. Many people tend to believe that men have one less rib because of Bible/Sunday School teachings; Genesis 2, verses 21 and 22: “So the Lord God caused a deep sleep to fall upon the man, and while he slept took on of his ribs and closed up it’s place with flesh; and the rib which the Lord God had taken from the man he made into a woman and brought her to the man.” Interesting fact about the people who believe this is their lack of examination of the subject. Why is it expected that men would have one fewer rib than women? Why wouldn’t women simply have only one rib, since that is all that was used to make them? Why indeed are women composed of any bones other than that one rib? Was the rib only taken from one side? And if it was, why don’t men have uneven numbers of these bones on the left and right sides?