Human Osteology (Axial and Appendicular Skeleton)

Summary

This video revisits human anatomy, focusing on the skeleton's structure and function, essential in biological anthropology. It introduces osteology—the study of bones—and highlights its significance in understanding human evolution, locomotion, and diet. The video explains key anatomical terms and planes, covers the axial and appendicular skeleton, and provides a detailed breakdown of bones in the skull, vertebral column, ribcage, limbs, and pelvis. Additionally, it discusses the evolutionary transition from ancient hominins to modern humans, setting the stage for deeper exploration into the history of human evolution.

Takeaways

• 🦴 Osteology, the study of bones, is crucial to Biological Anthropology, including forensic work and paleoanthropology.
• 🦵 The human skeleton is understood in the anatomical position: upright, with thumbs pointing outward and palms forward.
• 📏 Anatomical planes and directions (transverse, sagittal, coronal) help orient bones in relation to each other.
• 📍 Distal and proximal describe a bone’s position in relation to the trunk; medial and lateral relate to the sagittal midline.
• 🦠 The skull consists of paired and unpaired bones held together by fibrous joints called sutures, which fully close by age two.
• 🧠 The foramen magnum, located at the base of the skull, can indicate the locomotion style (bipedal or quadrupedal) of hominins.
• 🦷 Humans have four types of teeth—incisors, canines, premolars, molars—with a 2:1:2:3 dental formula, shared with other catarrhine primates.
• 🦵 The appendicular skeleton includes the limbs and pelvis, connecting via the pectoral and pelvic girdles for movement and support.
• 🧍‍♂️ The human vertebral column is divided into cervical, thoracic, lumbar, sacral, and coccygeal vertebrae, with specific functions and structures.
• 🦿 As hominins evolved, changes in the skeletal structure (e.g., skull, pelvis, limb bones) reflect adaptations like bipedalism and dietary shifts.

Q & A

What is osteology, and why is it important to biological anthropology?

Osteology is the study of bones, and it is crucial to biological anthropology because it helps in understanding skeletal remains in forensic work, paleoanthropology, and functional morphology of living primates. It provides insights into the structure and function of the human skeleton, and how bones have changed over time in relation to diet and locomotion.

How is the human skeleton divided, and what does each part include?

The human skeleton is divided into two primary parts: the axial skeleton and the appendicular skeleton. The axial skeleton consists of the skull, ribcage, and vertebral column, while the appendicular skeleton includes the limbs and pelvis.

What are the major sutures of the skull, and what do they connect?

The major sutures of the skull include the coronal suture, which joins the frontal bone with the parietal bone, the sagittal suture, which joins the two parietal bones, and the lambdoidal suture, which joins the parietal bone with the occipital bone.

How do anatomical planes and directions help in orienting bones in the human skeleton?

Anatomical planes and directions orient bones by dividing the body into sections. The transverse plane divides the body into top and bottom, the sagittal plane into left and right, and the coronal plane into front and back. Terms like distal, proximal, medial, lateral, anterior, posterior, inferior, and superior refer to specific positional relationships between bones.

What are the different types of vertebrae in the vertebral column, and how are they structured?

The vertebral column consists of cervical, thoracic, lumbar, sacral, and coccygeal vertebrae. There are seven cervical vertebrae, twelve thoracic vertebrae, five lumbar vertebrae, five fused sacral vertebrae (forming the sacrum), and three to five fused coccygeal vertebrae (the tailbone). The cervical vertebrae include the Atlas (C1) and Axis (C2), which allow head movement.

What is the foramen magnum, and what significance does it hold in determining locomotion in ancient hominins?

The foramen magnum is the hole at the base of the skull where the spinal cord exits. Its angle and position are used to determine whether ancient hominins were bipedal or quadrupedal, providing clues about their locomotion.

What bones are involved in the human dental structure, and what is the human dental formula?

The mandible (jaw) and maxilla house the teeth, though teeth are not considered bones. Humans, like all catarrhine primates, have a dental formula of 2:1:2:3, meaning each quadrant of the mouth contains two incisors, one canine, two premolars, and three molars.

What bones make up the pectoral girdle, and how do they function in connecting the upper limbs to the axial skeleton?

The pectoral girdle consists of two scapulae (shoulder blades) and two clavicles (collarbones). These bones connect the upper limbs to the axial skeleton, with the scapula being highly mobile and articulating with the clavicle through the acromion process, as well as with the humerus, the bone of the upper arm.

What is the composition of the pelvis, and which bone connects the pelvis to the femur?

The pelvis consists of two halves, each called an os coxa, composed of three fused bones: the ilium, ischium, and pubis. The femur, the largest bone in the body, connects to the pelvis through the acetabulum, the socket of the hip.

What changes in the human skeleton can we observe as we move through the evolution of hominins?

As hominins evolved, their skeletons changed from a more basal 'ape-like' condition in the Miocene to the familiar large-brained, bipedal structure of modern humans. These changes are observed in features like cranial structure, dentition, and limb proportions, reflecting adaptations to diet, locomotion, and brain development.

Outlines

00:00

🦴 Introduction to Human Anatomy and Osteology in Anthropology

This paragraph introduces the topic of human anatomy, specifically focusing on the human skeleton and its importance in biological anthropology. It touches on osteology, the study of bones, and its significance in understanding human evolution, diet, and locomotion. Key anatomical terms and directional planes (transverse, sagittal, coronal) are explained, along with terms like distal, proximal, medial, lateral, anterior, and posterior. The human skeleton is divided into the axial skeleton (skull, ribcage, vertebral column) and the appendicular skeleton (limbs, pelvis). Detailed information about the skull bones, their sutures, and the position of the foramen magnum is provided, which helps in determining the locomotion of ancient hominins. The paragraph also covers the bones of the face, dental structures, and human teeth.

05:01

🦴 Detailed Breakdown of the Vertebral Column and Limbs

This paragraph delves into the structure of the vertebral column, highlighting the different types of vertebrae: cervical, thoracic, lumbar, sacral, and coccygeal. It explains the function of the Atlas (C1) and Axis (C2) vertebrae, which allow head movement. The distinctions between 'true', 'false', and 'floating' ribs are noted, as well as the composition of the sternum. It moves on to the appendicular skeleton, which includes the limbs and pelvis. The bones of the pectoral girdle (scapulae and clavicles), upper limbs (humerus, radius, ulna), and hands (carpals, metacarpals, phalanges) are discussed, along with the pelvic bones and lower limbs (femur, tibia, fibula). The tarsal bones of the feet are also listed. The paragraph concludes by foreshadowing how these bones change over time as hominins evolve from an ape-like condition to modern humans.

Keywords

💡Osteology

Osteology is the study of bones, which is crucial in Biological Anthropology for understanding human evolution. It focuses on both the structure and function of bones, helping anthropologists analyze skeletal remains to determine things like locomotion and diet. In the video, osteology serves as the foundation for discussing how bones change over time and the importance of bone analysis in different fields like forensic work and paleoanthropology.

💡Anatomical position

The anatomical position refers to a standard posture used as a reference in anatomy: the body is upright, with thumbs pointing outward and palms facing forward. This orientation helps describe the locations and relationships between bones. In the video, the anatomical position is necessary for understanding terms like distal, proximal, medial, and lateral, which describe bone locations relative to each other.

💡Axial skeleton

The axial skeleton consists of the bones along the central axis of the body, including the skull, ribcage, and vertebral column. This part of the skeleton protects vital organs like the brain, heart, and spinal cord. In the context of the video, the axial skeleton's role is discussed when explaining its structure and function in comparison to the appendicular skeleton.

💡Appendicular skeleton

The appendicular skeleton includes the bones of the limbs and the pelvis, responsible for movement and supporting the body's weight. It works with the axial skeleton for overall bodily function. The video highlights its role when describing how the limbs and pelvis contribute to human mobility, a key aspect when studying evolutionary changes in bipedalism.

💡Foramen magnum

The foramen magnum is the large hole at the base of the skull where the spinal cord passes through to connect with the brain. Its angle and position are important for determining whether ancient hominins were bipedal or quadrupedal. In the video, the foramen magnum is mentioned as an indicator of locomotion in human evolution studies.

💡Sagittal suture

The sagittal suture is the fibrous joint that connects the two parietal bones of the skull. This suture is crucial in understanding skull anatomy and is used in osteology to assess age and growth patterns. In the video, the sagittal suture is one of the key sutures discussed in the context of cranial bone structure and development.

💡Phalanges

Phalanges are the bones of the fingers and toes. In humans, they are arranged in proximal, middle, and distal sets that allow for the dexterity of hands and feet. The video references phalanges when explaining the structure of the appendicular skeleton and the distinctions between the bones of the upper and lower limbs.

💡Dental formula

The dental formula refers to the specific arrangement of different types of teeth in primates, including humans. The human dental formula is 2:1:2:3, which means two incisors, one canine, two premolars, and three molars in each quadrant of the mouth. The video uses the dental formula to compare humans with other catarrhine primates and explain evolutionary traits related to diet.

💡Atlas and Axis

The Atlas (C1) and Axis (C2) are the first two cervical vertebrae, responsible for allowing the head to move. The Atlas enables the head to nod, while the Axis allows it to rotate side to side. In the video, these vertebrae are described to explain the vertebral column's role in supporting the head and enabling movement, a key point when discussing human skeletal function.

💡Pelvis

The pelvis is a bony structure made up of three fused bones: the ilium, ischium, and pubis. It connects the axial skeleton to the lower limbs and plays a major role in locomotion and childbirth. The video examines the pelvis in the context of human evolution, particularly how changes in its structure relate to bipedalism and other adaptations.

Highlights

Osteology is a critical field in Biological Anthropology, relevant for forensic work, paleoanthropology, and functional morphology of primates.

Understanding the human skeleton's structure and function helps us analyze human evolution, especially in relation to diet and locomotion.

The anatomical position of the human skeleton is upright, with thumbs pointing outward and palms forward, serving as a basis for anatomical reference.

Anatomical planes, including transverse, sagittal, and coronal, are key to orienting bones in relation to each other.

The human skeleton is divided into the axial skeleton (skull, ribcage, vertebral column) and appendicular skeleton (limbs and pelvis).

The bones of the skull are held together by sutures, which fully close by age two in humans, leaving a 'soft spot' at birth.

The foramen magnum’s angle and position in the skull indicate whether a species was bipedal or quadrupedal.

The human dental formula (2:1:2:3) reflects our evolutionary relationship with other catarrhine primates, indicating the number of each type of tooth.

The vertebral column is divided into cervical, thoracic, lumbar, sacral, and coccygeal vertebrae, each serving distinct functions in human movement and support.

The human ribs are categorized as true, false, or floating ribs based on their connection to the sternum or lack thereof.

The pectoral girdle, including the scapulae and clavicles, provides mobility for the upper limbs and is crucial for human limb movement.

The pelvis is composed of two os coxae, each consisting of three fused bones—ilium, ischium, and pubis—highlighting its importance in bipedal locomotion.

The femur, the largest bone in the body, articulates with the pelvis through the acetabulum, a key feature in bipedal movement.

In humans, the lower leg consists of the tibia and fibula, with the tibia playing a major role in weight-bearing and articulation with the femur.

As humans evolved from ape-like ancestors in the Miocene, significant changes occurred in skeletal structure, including brain size and bipedalism.

Transcripts

With some relevant information on evolution  understood, let’s now review some information  

regarding human anatomy, so that we can dive into  the meat of this anthroplogy series. As we will be  

discussing a wide variety of skeletal remains, we  must recall some things about the human skeleton.  

This was covered in a basic way over in the  Anatomy & Physiology series, but now let’s  

revisit the subject with a little more context. Osteology, the study of bones, is vitally  

important to Biological Anthropology. Whether we  are considering forensic work, paleoanthropology,  

or the functional morphology of other living  primates, knowing the nature of the human  

skeleton is critical. Within the context  of human evolution, we need to see how our  

bones have changed over time, and how this  relates to things like diet and locomotion. 

Osteology generally concerns not just the  structure of the skeleton, but its function as  

a whole, and with consideration to each bone. The  human skeleton is navigated assuming the following  

anatomical position: upright with the thumbs  pointing outward and the palms forward. Anatomical  

planes and directions help orient bones in  relation to one another. The transverse plane cuts  

the skeleton into top and bottom, the sagittal  plane into left and right, and the coronal plane  

into front and back. Distal and proximal refer  to a bone’s position or surface in the limbs with  

relation to the trunk: The phalanges, or fingers,  are distal to the humerus, or upper arm. Likewise,  

the humerus is proximal to the phalanges. Medial  and lateral refer to a bone’s position or surface  

in relation to the sagittal midline of the body:  The ulna, a forearm bone, is medial to the radius.  

Likewise, the radius is lateral to the ulna.  Anterior and posterior refer to a bone’s position  

or surface in relation to the coronal plane:  The sternum, or breast bone, is anterior to  

the vertebral column. Likewise, the vertebral  column is posterior to the sternum. Lastly,  

inferior and superior refer to a bone’s position  or surface as “above” and “below”: The skull  

is superior to the vertebral column. Likewise,  the vertebral column is inferior to the skull. 

The skeleton can also be divided into two  primary parts: the axial skeleton and the  

appendicular skeleton. The axial skeleton contains  the skull, ribcage and the vertebral column, while  

the appendicular skeleton contains the limbs and  pelvis. The skull contains numerous bones, some of  

which are paired in two mirrored parts, and some  of which are not. The bones of the skull are held  

together by fibrous joints, known as the sutures  of the skull. These sutures do not fully close  

until age two in humans, which is why babies have  a “soft spot” on their head, that is effectively  

exposed brain. The largest sutures of the skull  include the coronal suture, which joins the  

frontal bone with the parietal bone, the sagittal  suture, which joins the two parietal bones, and  

the lambdoidal suture, which joins the parietal  bone with the occipital bone. The bones of the  

brain case thus include the non-paired frontal,  occipital, sphenoid, and ethmoid bones, and the  

paired parietal and temporal bones, for a total  of eight cranial bones. At the base of the skull,  

where the spinal cord exits, is a hole called the  foramen magnum. This hole’s angle and position  

can be used to determine the locomotion of ancient  hominins, whether they are bipedal or quadrupedal. 

The bones of the face can also be paired or  unpaired. Unpaired bones include the vomer and  

the mandible, or jaw, and the paired bones include  the nasals, lacrimals, palatines, inferior nasal  

conchae, the maxilla, and the zygomatics,  or cheekbones. The mandible and maxilla  

house the teeth, which are not considered to be  bones but are important to know about. Humans,  

like all primates, have four types of teeth  that are defined by their cusping: incisors,  

canines, premolars, and molars. The human dental  formula is the same as all catarrhine primates:  

2:1:2:3, which indicates that in each  quadrant of the mouth we have two incisors,  

one canine, two premolars and three molars.  The most posterior molars, the wisdom teeth,  

cause crowding in some humans and must be removed. The vertebral column protects the spinal cord,  

which exits the skull via the foramen magnum,  and is composed of several types of vertebrae:  

Cervical, Thoracic, Lumbar, Sacral and Coccygeal.  Within the cervical vertebrae, the Atlas (C1)  

is the first and allows the head to “nod” up and  down, while the Axis (C2) is second and allows the  

head to “shake” left and right. There are seven  cervical vertebrae, twelve thoracic vertebrae,  

five lumbar vertebrae, five fused sacral vertebrae  known collectively as the sacrum, and three  

to five fused coccygeal vertebrae, colloquially  known as the tailbone. Attaching to the thoracic  

vertebrae, humans have 12 paired ribs. “True” ribs  connect directly to the sternum, “False” ribs via  

cartilage, and “Floating” ribs do not connect  at all. The sternum is composed of three smaller  

bones: The manubrium is most superior, then the  body, and the xyphoid process is most inferior. 

Moving on, the appendicular skeleton includes the  limbs and pelvis. The appendicular skeleton is  

symmetrical, so the bones on the right side of the  body have a mirror counterpart on the left side.  

The pectoral girdle connects the upper limbs  to the axial skeleton, and is composed of two  

scapulae, or shoulder blades, and two clavicles,  or collarbones. The scapula in humans is highly  

mobile, and articulates with the clavicle through  the acromion process. Both bones also articulate  

with the humerus; the bone of the upper arm. The  forearm is composed of two bones: the radius and  

the ulna. The proximal end of the ulna creates the  olecranon, or elbow, and in anatomical position is  

medial to the radius. The radius, naturally, is  lateral to the ulna and articulates distally with  

the carpals, or wrist bones, specifically, the  scaphoid and lunate bones. From lateral to medial,  

the other carpal bones include the trapezium,  trapezoid, capitate, hamate, triquetrum,  

and pisiform bones. The carpals articulate  with the metacarpals, or palmar bones,  

which articulate with the phalanges, or finger  bones. A single finger bone is called a phalanx,  

and there are proximal, middle, and distal  phalanxes that are separated by the finger joints. 

The pelvis can be separated into two halves,  which are individually known as os coxae. A  

single os coxa is composed of three fused bones:  the ilium, or blade of the pelvis, the ischium,  

and the pubis. The femur, the largest bone in  the body, articulates with the pelvis by the  

acetabulum, or socket of the hip. The lower leg is  composed of the tibia and the fibula. The tibia,  

or shin bone, articulates proximally with  the femur, while the fibula articulates  

with the tibia instead. The tarsals, or ankle  bones, meet the tibia by way of the talus bone,  

which articulates with the calcaneus, or heel  bone. From medial to lateral, the remaining  

tarsals include the cuneiforms and navicular,  as well as the cuboid bone. The metatarsals make  

up the plantar portion of the toes and they  articulate with the phalanges, or toe bones. 

As we move forward in this series, we will see  how these bones change over time; going from a  

more basal “ape-like” condition in the Miocene, to  the familiar large-brained, bipedal hominins that  

would eventually yield humans. So let’s continue  and dive back into the history of hominins.