Human Skeleton Notes

Neurocranium

Frontal

Ectocranial

1. Frontal eminence (original center of ossification)
2. Temporal lines (appear when you grit your teeth)
3. Brow ridge
4. Supraorbital margin
5. Supraorbital foramen or notch (passage for vessels)
6. Glabella (between the eyebrows)
7. Zygomatic process of the frontal (articulates with zygomatic bone)

Endocranial

1. Sagittal sulcus
2. Frontal crest
3. Foramen cecum
4. Meningeal grooves

Inferior view

1. Ethmoidal notch (location of ethmoid bone)
2. Lacrima fossa (location of lacrimal gland)
3. Frontal sinuses

Variations

1. Metopic suture

Compared to the parietals, the minengeal impressions are fainter and the endocranial surface is more undulating.

Parietal

Angles

1. Frontal angle (90 degrees)
2. Sphenoidal angle
3. Occiptal angle (near the occipital bone)
4. Mastoid angle (near the mastoid process)

Ectocranial

1. Parietal boss
2. Parietal foramen (near the sagittal suture)
3. Parietal striae (away from the sagittal suture)
4. Temporal lines (extending from the frontal bone)

Endocranial

1. Sagittal sulcus
2. Sigmoid sulcus (near the mastoid angle)
3. Meningeal grooves

Variations

1. Bregmatic bone
2. Wormian bones

Occipital

Ectocranial

1. External occipital protuberence
2. Highest, superior, and inferior nuchal lines
3. External occipital crest (leading to the foramen magnum)
4. Foramen magnum ("big hole")
5. Occipital condyle (bean-shaped and articulates with C1)
6. Condylar foramen (superior to the condyles)
7. Hypoglossal canal (inferior to the condylar foramen)

Endocranial

1. Cruciform eminence
2. Cerebral fossa (triangular)
3. Cerebellar fossa (quadrangular)
4. Sagittal sulcus (usually swings right)
5. Transverse sulcus (opp. sagittal sulcus)
6. Internal occipital crest (leading to the foramen magnum)
7. Jugular notch (below the foramen magnum)
8. Middle meningeal grooves

Variations

1. Inca bone
2. Apical bone

Temporal

There are four parts of the temporal bone: squama, mastoid (right behind the ear), petrous (pyramid), and tympanic (inside).

Ectocranial

1. Zygomatic process (and articulates with zygomatic bone)
2. Articular eminence (right below the zygomatic process)
3. Mandibular fossa (right next to the articular eminence)
4. Post-glenoid process (small cone behind the mandibular fossa)
5. Suprameatal crest (root of zygomatic process above the EAM)
6. Supramastoid crest (extension of the suprameatal crest)
7. Parietal notch (end of the crest that is level with the zygomatic process)
8. Mastoid process (behind the ear)
9. Mastoid notch (behind the mastoid process)
10. Mastoid foramen
11. External acoustic meatus (EAM)

Endocranial (posterior view)

1. Internal acoustic meatus (biggest hole on the inside)

Endocranial (inferior view)

1. Styloid process (pointed projection)
2. Styloidmastoid foramen (under the styloid process)
3. Jugular fossa (bottom-right of the styloid process)
4. Cartoid canal (above the styloid process)

Splanchnocranium

Auditory Ossicles

1. Stapes
2. Incus
3. Malleus

Sphenoid

The sphenoid is comprised of the body, lesser wings, greater wings, and the pterygoid process.

Posterior View

1. Anterior clinoid process (hooks under the wings)
2. Sella turcica (between the wings)
3. Pituitary fossa (under the Sella turcica)
4. Dorsum sellae (handlebars)
5. Posterior clinoid process (ends of handlebars)
6. Clivus (under the posterior clinoid process)
7. Body (under the dorsum sellae)

Posterior View (OOROS)

1. Optic canal
2. Superior orbital fissures
3. Foramen rotundum (round)
4. Foramen ovale (oval)
5. Foramen spinosum (tiny)

Anterior View

1. Orbital surfaces
2. Sphenoidal crest (middle ridge)
3. Sphenoidal sinus (holes on either side of the crest)
4. Sphenoidal rostrum (under the sphenoidal crest)

Anterior View (Pterygoid process)

1. Medial pterygoid plate
2. Pterygoid hamulus (hook on the medial pterygoid plate)
3. Lateral pterygoid plate
4. Pterygoid fossa (formed by the medial and lateral plates)

Ethmoid

1. Crista galli (projection)
2. Cribriform plate (horizontal plate)
3. Perpendicular plate
4. Lateral mass (labyrinth touching eye sockets)

Inferior Nasal Concha

Can see through the nasal cavity, on the sides. The maxillary process is the part that is hooked onto the side of the nasal aperture. The head is anterior and the long tail inferior. It's like a fish coming out.

Nasal

Makes up the bridge of the nose. The top that articulates with the frontal is thicker. The distal is longer than the medial.

Lacrimal

Inside of the eye socket, near the nose. The hook forms the grooves for the lacrimal glands.

Zygomatic

1. Frontal process
2. Orbital margin
3. Temporal process
4. Maxillary process
5. Masseteric origin (masseter muscle attaches)
6. Zygomaticofacial foramen

The anterior surface is big and flat and will have a zygomaticofacial foramen.

Maxilla

Anterior View

1. Frontal process
2. Zygomatic process
3. Infraorbital foramen (next to zygomatic process)
4. Canine jugum (from the canine root)
5. Canine fossa (posterior to the canine jugum)
6. Anterior nasal spine (near the nasal cavity)
7. Alveolar process (houses the teeth)
8. Alveolar canals (tooth sockets)

Superior view

1. Anterior lacrimal crest (near lacrimals)
2. Infraorbital sulcus (in the orbitals)

Posterior view

1. Maxillary sinus
2. Palatine process (roof of mouth)
3. Incisive foramen (right behind incisors)

Canine root is distinctive to anatomically modern humans. Humans have relatively flat faces; premaxilla fuse with maxilla.

Palatine

Shaped like an L. The shorter part is the horizontal plate and should be oriented medially. The longest part is the vertical plate. The posterior has a ridge sticking out called the pyramidal process.

1. Posterior nasal spine (articulates with the other palatine)
2. Pyramidal process
3. Greater palatine foramen (anterior)
4. Lesser palatine foramen (posterior)

Vomer

Divides the nasal aperture in half. The anterior is thin and the posterior is thick.

Mandible

The mandible is divided into the body (corpus) and the ascending ramus.

External surface

1. Mental eminence (chin)
2. Mental foramen
3. Alveolar process
4. Alveolar canals
5. Gonial angle
6. Masseteric tuberosity (rough)
7. Ascending ramus
8. Mandibular condyle (more posterior than coronoid process)
9. Coronoid process (more anterior than condyle)
10. Condylar neck (between the condyle and the coronoid process)
11. Mandibular notch

Internal surface

1. Mandibular foramen
2. Lingula (sticks up next to mandibular foramen)
3. Pterygoid tuberosity
4. Mylohyoid groove (extends from the lingula)
5. Mylohyoid line (more anterior than the mylohyoid groove)
6. Submandibular fossa (between the groove and the line)
7. Mental spines (near the chin)
8. Digastric fossa (inferior and posterior to mental spines)

The mental eminence is a distinctive feature of anatomically modern humans.

Men tend to have a more 90° gonial angle, while women tend to have a more obtuse gonial angle. Older individuals with tooth loss also tend to have a more obtuse gonial angle.

Dentition

Terms

1. Mesial is toward the midline and distal is away from the midline
2. Labial is toward the lips and buccal is toward the cheek
3. Lingual is toward the tongue
4. Interproximal is where two teeth meet
5. Incisal and occlusal are biting surfaces

Humans are diphyodont, which means that they have two sets of teeth, deciduous (baby) and permanent.

Humans are also heterodonts, which means that we have different types of teeth. Incisors are used for cutting, canines for tearing, premolars for grinding, and molars for crushing.

Teeth Anatomy

Teeth have two parts (crown and root) and three layers (enamel, dentine, and pulp chamber). Connective tissue called cementum holds the teeth in place.

Teeth grow from the cusp to the cemento-enamel junction (CEJ). Roots are the last to form. Ameloblast deposit enamel at the same time as adontoblast deposit dentine.

Enamel is 96% mineral. Dentine is 70% mineral and 30% collagen. The pulp chamber is mostly nerves and blood vessels.

Adults have 32 teeth. There are four quadrants in the mouth, each with 8 teeth: 2 incisors, 1 canine, 2 premolars, and 3 molars. The third molars are the wisdom teeth. Many people have the third molar pulled out because they cause crowding.

Identifying Teeth

Upper incisors are generally larger, broader, and more likely to be shovel-shaped. Upper incisor roots are more circular, while lowers are more compressed. Incisors tend to be more 90 degree mesially and curved distally.

Canines tend to come to a point and tend to be wider than incisors. Upper canines are generally larger, broader, and more likely to have cingulum than the lowers.

Premolars are also called bicuspids because they have two cusps. Lowers have a larger buccal cusp than lingual cusp. Uppers sometimes have two roots (often fused). The first premolar has more asymmetric cusps than the second premolar.

Upper molars usually have 3 roots and 3-4 major cusps. Lower molars generally have 2 roots and 4-5 major cusps. The uppers tend to be square in shape while the lowers tend to be rectangular or oblong. Uppers tend to be more asymmetric around the mesiodistal axis than lowers. This is because uppers have triangular hypocone on the lingual distal end. This hypocone is largest on the first molar and smaller on the second and third.

To side the teeth, note that the roots swing distally.

Spine

Hyoid

1. Body
2. Greater horns
3. Lesser horns

Vertebrae

General Features:

1. Body
2. Pedicle
3. Lamina
4. Spinous process (pointy bit)
5. Superior articular facet
6. Inferior articular facet
7. Transverse process
8. Vertebral foramen (where spinal cord goes through)

Cervical Vertebrae

Cervical vertebrae make up the bones in the neck. They can be distinguished from the other vertebrae by the presence of transverse foramina. They also may have a bifurcated spinous process and a small body. The superior and inferior articular facets are oriented in a horizontal plane.

Superior View

1. Transverse foramen
2. Transverse tubercle
3. Facet for dens (C1, body)
4. Dens (C2, protrusion on body)
5. Facet for atlas (C2)

Specific vertebrae

• C1 (atlas) has no body or spinous process. In place of the body is the facet for the dens, which articulates with the dens of C2. The superior articular facets are large and concave to articulate with the occipital condyles.
• C2 (axis) and has a projection called the dens that articulates with the atlas.

Thoracic Vertebrae

The thoracic vertebrae articulates with the ribs and can be distinguished by the presense of demi-facets on the body and constal facets on the transverse process. Additonally, the superior and inferior articular facets are oriented more vertically.

Features

1. Superior articular process (face posteriorly)
2. Inferior articular process (face anteriorly)
3. Transverse costal facet (on the transverse process, articulates with rib)
4. Superior costal demi-facet (on the body, articulates with rib)
5. Inferior costal demi-facet (on the body, articulates with rib)

Specific vertebrae:

• T10 has a single rib facet and a transverse costal facet.
• T11 has a single rib facet and no transverse costal process.
• T12 has a signle rib facet and no transverse costal process. However, it has inferior articular facets that are oriented like lumbar vertebrae.

Lumbar Vertebrae

Lumbar vertebrae have large bodies and short, blunt spinous processes. They can be distinguished by the lack of transverse foramina and costal facets.

1. Superior articular process
2. Inferior articular process
3. Mammilary process (knob on the superior articular process)

Pelvic Girdle

Os Coxae

The os coxae makes up the pelvis. It is made up of three bones that fuse together in adulthood:

1. Ilium (large flaring part of the hips)
2. Ischium (where you sit on)
3. Pubis (where the pelvis meets in the front)

It also has two landmarks:

1. Obturator foramen (big hole covered by membrane)
2. Acetabulum (hip sockets)

Illium and Ischium (Anterior View)

1. Iliac crest (top of the ilium)
2. Iliac fossa (bowl)
3. Iliac tuberosity (back of ilium, behind the auricular surface)
4. Auricular surface (immovable joint where the sacrum articulates with the ilium)
5. Preauricular sulcus (sulcus below the auricular surface)
6. Arcuate line (coming from base of iliac fossa)
7. Iliac spines (anterior-superior, anterior-inferior, posterior-superior, posterior-inferior)
8. Greater sciatic notch
9. Ischial spine (divides the sciatic notches)
10. Lesser sciatic notch
11. Ischial tuberosity

Pubis (Anterior View)

1. Illiopubic ramus
2. Pubic tubercle
3. Ischiopubic ramus
4. Obturator crest (anterior)
5. Pectineal line (posterior)
6. Pubic symphysis (where the pubic bones articulate)

Acetabulum

1. Lunate surface
2. Acetabular fossa

Posterior View

1. Anterior gluteal line (starts at the top of the iliac crest)
2. Posterior gluteal line (starts at the start of the iliac crest)

Males tend to have a smaller greater sciatic notch. Females tend to have a preauricular sulcus.

Sacrum

The sacrum is made up of five fused vertebrae. It articulates with the ilium at the auricular surface and with the coccyx at the sacral hiatus.

Anterior View

1. Sacral plateau (top of sacrum)
2. Sacral promontory (ridge on plateau)
3. Anterior sacral foramina (holes)
4. Transverse ridges (bridge the holes)

Lateral View

1. Ala (wings on either side)
2. Auricular surface (articulates with the ilium)

Posterior View

1. Sacral canal (houses spinal cord)
2. Superior articular process (juts out)
3. Superior articular facet (similar to the vertebrae)
4. Dorsal wall (back surface)
5. Median sacral crest (midline ridge)
6. Lateral sacral crest (lateral to the holes)
7. Posterior sacral foramina (holes)
8. Sacral hiatus (opening at the of sacral canal)
9. Sacral cornu (horn-like projections at apex)

The coccyx is a triangular bone at the base of the spine consisting of multiple fused vertebrae.

Pectoral Girdle

Clavicle

The clavicle, also known as the collabone, serves as a strut between the scapula and the sternum.

The rounder and thicker end is medial and articulates with the sternum. The flatter end is lateral and articulates with the scapula. The medial end tends to points backward and the lateral end tends to point forward. The superior side is smooth and the inferior side is rough. The inferior side also has a sulcus.

Superior View

1. Articular surface for the manubrium (articulates with the sternum)
2. Rugosities for the deltoid muscle
3. Arcomial facet

Inferior View

1. Costoclavicular impression (connects with the first rib)
2. Rugosities for the pectoralis major muscle
3. Subclavian groove
4. Conoid tubercle

Here are some clearer images of the costoclavicular impression, subclavian groove, and conoid tubercle:

Note that the deltoid muscle attaches to the lateral, superior side of the clavicle, while the pectoralis major muscle attaches to the medial, inferior side near the pecs. The subclavian groove is where the subclavius muscle attaches.

The clavicle is the first bone to start ossification and last bone to finish ossification.

Scapula

The scapula, also known as the shoulder blade, is a flat bone that connects the humerus with the clavicle. It has two surfaces (dorsal and costal) and three borders (superior, medial, and lateral).

General

1. Dorsal surface (has acromion)
2. Costal surface (facing ribs, does not have acromion)
3. Superior border (shortest side of the triangle)
4. Medial border (facing toward the vertebrae)
5. Lateral border (toward the arms)

Dorsal Surface

1. Acromiom (articulates with the clavicle)
2. Articular facet for the clavicle (articulates with the clavicle)
3. Coracoid process (smaller projection, sticks anteriorly)
4. Scapular notch (near the coracoid process)
5. Scapular spine (base of the acronium)
6. Supraspinous fossa
7. Infraspinous fossa
8. Inferior angle (bottom of the triangle)

Costal Surface

1. Subscapular fossa (large area)
2. Oblique ridges (bottom third of scapula)

Lateral View

1. Glenoid fossa (flat area that articulates with the humerus)
2. Supraglenoid tubercle (apex of the glenoid fossa)
3. Infraglenoid tubercle (bottom of the glenoid fossa)

Thorax

Sternum

The sternum is divided into the manubrium and the body, which may fuse later.

To orient the sternum, note that there are demifacets where the manubrium and the sternum meet. There is also a huge gap between costal notches 2 and 3.

Features

1. Jugular notch (top of sternum)
2. Clavicular notch (articulates with the clavicle)
3. Costal notch 1
4. Costal notch 2 (where the manubrium and body meet)
5. Costal notches 3-7 (articulates)
6. Xiphoid process (bottom of sternum)

Variations

1. Sternal foramen
2. Cleft sternum

Note that the sternum articulates with the ribs (costal cartilage) at the costal notches. The first rib articulates with the manubrium, while ribs 2-7 articulate with the body. Ribs 8-10 articulate with the costal cartilages of the ribs above them.

Ribs

The sternal end is flat and blunt, while the vertebral end is round and has a head that articulates with the vertebrae. The costal groove is on the inferior side of the rib.

R1-R7 are called with the true ribs because they articulate directly with the sternum. R8-R10 are called the false ribs because they articulate with sternum via other rib cartilate. R11 and R12 are called floating ribs because they do not articulate with the sternum at all.

R1-R10

1. Head (round and articulates with the vertebrae)
2. Tubercle (inferior, articulates with transverse process of vertebrae)
3. Neck
4. Angle (where the rib starts to curve)
5. Shaft (body of the rib)
6. Costal groove (inferior)
7. Caudal edge (inferior)

R1

1. Scalene tubercle (between the grooves)
2. Groove for subclavian artery (inferior, vertebral end)
3. Groove for subclavian vein (superior, sternal end)

R11 and R12 does not have a flat sternal end. R11 has a slight angle to it, whereas R12 does not.

Bone Biology

Composition and Function

Bone is 70-80% mineral (hydroxyapatite) and 20-30% organic (collagen). The collagen prevents the bone from becoming brittle.

Bone acts as both an organ and a tissue. As an organ, bone protects soft tissues; anchors muscles, tendons, and ligaments; and acts as levers for movement. As a tissue, bone produces blood cells and acts as a reservoir of nutrients (calcium, fat).

Human bones vary widely. There are four main types of variation: ontogeny (development), sexual dimorphism, geography (population), and individual.

The human skeleton is constantly remodeling in response to stress. Wolff's Law states that bone is deposited where needed and resorbed where not needed.

Musculoskeletal System

Joints are the structure between bones. There are three main types of joints:

1. Synovial joints are freely movable. They include ball-and-socket joints (hip), hinge joints (elbow, knee), saddle-shaped joints (thumb), and planar joints (wrist, foot arch).
2. Cartilaginous joints are made of cartilage and allow limited movement. One example are growth plates, which temporarily connect growth centers in a single bone.
3. Fibrous joints are immovable (cranial sutures).

Cartilage is a flexible connective tissue found in joints. It is composed mostly of collagen.

Ligaments connect bone to bone to stabilize joints. Tendons connect muscle to bone to facilitate movement. Both ligaments and tendons are connective tissue made of collagen.

Anatomy

Bones can be categorized based on their shape

1. Long bones include the arms and legs
2. Short bones include metacarpals (hands), phalanges (fingers), and clavicles (collarbones)
3. Flat bones include the cranial vault, scapulae, sternum (breastbone), ribs, and innominate (hipbone)
4. Irregular bones include carpals (wrists), tarsals (ankles), and vertebrae
5. Sesamoid bones are small, round bones embedded in tendons, like the patella (kneecap)

Bones can also be categorized based on their internal structure

1. Compact bone is hard and makes up the outer layer of bones
2. Spongy (cancellous) bone is porous and makes up the inner layer of bones
3. Subchondral bone is covered by cartilage in joints

The long bone has several areas:

1. The epiphysis (end of bone) develops from secondary ossification centers
2. The diaphysis (shaft) develops from the primary ossification center
3. The metaphysis is the area between the epiphysis and diaphysis where growth plates are located
4. The medullary cavity is the hollow center of the diaphysis that contains bone marrow

The periosteum is a membrane that covers the outer surface of bones. It contains blood vessels, nerves, and cells that help with bone growth and repair.

Histology

Histology is the study of tissues at the microscopic level.

The Haversian system (osteon) is the basic structural unit of compact bone. It consists of concentric layers (lamellae) of bone tissue surrounding a central canal (Haversian canal) that contains blood vessels and nerves. Within each lamella, there are small cavities called lacunae that house bone cells (osteocytes).

There are three primary types of bone cells:

1. Osteoblasts lay new bones and become osteocytes
2. Osteocytes live in lacunae and maintain bone tissue
3. Osteoclasts resorb bone

Ossification

There are two types of ossification (bone formation):

1. In intramembranous ossification, mesenchymal tissue is directly converted into bone.
2. In endochondral ossification, a cartilage model is first formed and then replaced by bone. This process is responsible for the formation of most bones in the body.

Primary centers of ossification appear during fetal development and form the diaphysis. Secondary centers of ossification appear after birth and form the epiphyses.

The process of bone growth occurs through two main mechanisms:

1. The bone grows in length at the growth plates located in the metaphysis.
2. The bone grows in width with the help of nutrient foramen, or openings in the bone that allow blood vessels to enter.

As a result of ossification, a child has around 270 bones, while an adult only has around 206 bones,

Non-Human Bone

Human bones tend to be more dense and have less trabeculae in the ends than non-human bones.

Burial Excavation

Steps:

1. Pedestaling (removing dirt)
2. Documentation
3. Lifting (packaging the bones individually)
4. Washing
5. Soft tissue removal (with dermestid beetles)
6. Reassembly (with Arcyloid B-72)
7. Accession (labeling)
8. Inventory

Acryloid B-72 is inorganic, won't degrade over time, and is dissolvable in acetone.

Afterward burial excavation, one can do sex estimation, age estimation, and checking for pathologies.

Sex Estimation

The best way to perform sex estimation is to look at the os coxae, skull and then metrics. However, no method of sex estimation is perfect.

Sex Estimation with the Os Coxae

Sex Estimation with the Skull

Men tend to have more robust facial muscles, affecting the bones at the skeletal-muscular sites (SMS).

Age Estimation

Subadult age estimation is based on stages of growth and development. Adult age estimation is based on stages of degeneration.

Phase systems are based on stages of development or degeneration. Component systems are based on individual features that can be observed and scored.

Subadult Age Estimation

Indicators:

• Dental development
• Appearance of ossification centers
• Suture closure (basilar and metopic)
• Long bone lengths
• Epiphyseal fusion

Malnourishment or ill health can stunt development. Dental development is the most reliable of all techniques.

Adult Age Estimation

Indicators:

• Pubic symphysis
• Auricular surface of the os coxae
• Cranial suture closure
• 4th sternal rib end
• Histology (secondary osteon counting)

The Todd system did age estimation based on the pubic symphysis. It has 10 phases.

The Suchey-Brooks system later modified the Todd system. It has 6 phases:

1. Ridges and furrows, or billowing
2. Billowing breaks down
3. Bone builds up around joint margins
4. The ventral rampart forms and the rim becomes more defined
5. The porosity of the bone increases
6. The rim breaks down

Lovejoy et al. made a phase system based on the auricular surface of the os coxae. It is not a very reliable method because two observers can easily disagree on the phase.

Lovejoy et al. made a component system based on the cranial suture closure. Younger individuals tend to have more open sutures, while older individuals tend to have more closed sutures. It is not a very reliable method because it is impacted by individual variation and environmental factors.

Transition analysis is a component system that uses observations throughout the skeleton. It uses Bayesian statistics to combine the skeletal observations with a prior age distribution. Traditional methods often underestimate the ages of older adults, partly because reference collections are biased.

Mortuary Archaeology

Mortuary archaeology is the study of the treatment of dead bodies in ancient societies.

Placement of the dead

• Cemeteries (Arlington)
• Pyramids
• Tzompantli
• Beneath the home

Body treatment

• Cinnabar (Tomb of the Red Queen)
• Mummification
• Embalming
• Cremation

Grave goods

• Pottery
• Food

Based on funerary treatment, we can make assumptions on socioeconomic status, role in life, and beliefs and traditions.

Bioarchaeology

Bioarchaeology is the application of biological anthropology (osteology) to the study of human remains recovered from archaeology sites. It is like forensic anthropology, but with a focus on the past.

Bioarchaeologists tend to ask demographic questions about

• Quality of life (health, diet, disease, growth and development)
• Behavior and lifestyle (occupational stress, habit-induced arthritis)
• Aesthetics and identity (tooth filing, dental inlays, avulsion, cranial modification)
• Warefare and violence (perimortem trauma)
• Population history (migration, ancestry)

Some analytic methods include:

• Life history (sex, age, ancestry estimation)
• Paleopathology
• Stable isotope analysis (for diet)
• Biodistance analysis
• Ancient DNA analysis

Linear enamel hypoplasia (LEH) is a line in the enamel that can be used to infer periods of stress during childhood.

References

1. Anatomy Standard