Human Skeletal System: Structure, Divisions, and Bone Markings

What is the primary function of the human skeleton?

To provide protection, locomotion, and manipulation.

What percentage of body weight does the skeletal system account for?

About 20%.

What are the main components of the skeletal system?

Bones, cartilages, joints, and ligaments.

What are the two main divisions of the human skeleton?

The axial skeleton and the appendicular skeleton.

What does the axial skeleton consist of?

Bones of the head and trunk.

What is the primary function of the appendicular skeleton?

To allow mobility.

How many bones are in the axial skeleton?

80 bones.

What are the three major regions of the axial skeleton?

The skull, vertebral column, and thoracic cage.

What does the axial skeleton support and protect?

It supports the head, neck, and trunk, and protects the brain, spinal cord, and thoracic organs.

What are the components of the skull?

22 bones: 8 cranial bones and 14 facial bones.

What is the cranial cavity?

A chamber that supports the brain.

What are the two parts of the cranium?

The cranial vault and the cranial base.

What are the major skull sutures?

Coronal, sagittal, squamous, and lambdoid sutures.

What is the function of sutures in the skull?

To firmly unite the bones of the adult skull.

What is the significance of the cranial vault?

It forms the superior, lateral, and posterior aspects of the skull.

What distinguishes the mandible from other skull bones?

It is connected to the rest of the skull by freely movable joints.

What are the major cavities of the skull?

Cranial cavity, middle and interior ear cavities, orbital cavity, nasal cavity, and oral cavity.

What is the role of the frontal bone in the skull?

It forms the anterior cranium and articulates with the parietal bones via the coronal suture.

What are the parietal bones?

Curved, rectangular bones that form most of the superior and lateral aspects of the skull.

What is the appearance of suture lines in the skull?

They have a saw-toothed or serrated appearance.

How many auditory ossicles are associated with the skull?

6 auditory ossicles.

What is the role of ligaments in the skeletal system?

To connect bones and reinforce joints, allowing required movements while restricting others.

What is the function of joints in the skeletal system?

To provide remarkable mobility.

What are the four largest sutures associated with the parietal bones?

The sutures occur where the parietal bones articulate with other cranial bones.

Which bone forms most of the skull's posterior wall and base?

The occipital bone.

How does the occipital bone articulate with other bones?

It articulates anteriorly with the paired parietal and temporal bones via the lambdoid and occipitomastoid sutures.

Where are the temporal bones located in relation to the parietal bones?

The temporal bones lie inferior to the parietal bones and meet them at the squamous sutures.

What do the temporal bones form in the skull?

They form the inferolateral aspects of the skull and parts of the cranial base.

What role does the sphenoid bone play in the skull?

It forms part of the floor of the cranium, unites the cranial and facial bones, and acts as a cross-brace that strengthens the sides of the skull.

What structures does the ethmoid bone contribute to?

It forms the anteromedial floor of the cranium, the roof of the nasal cavity, part of the nasal septum, and the medial orbital wall.

How many bones make up the facial skeleton?

The facial skeleton is made up of 14 bones.

Which facial bones are unpaired?

The mandible and the vomer.

List some paired facial bones.

Maxillae, palatine bones, nasal bones, inferior nasal conchae, zygomatic bones, lacrimal bones.

What is the function of the muscles attached to the facial bones?

They control facial expressions and manipulate food.

What are foramina in the skull?

Foramina are passageways through the bones of the skull that allow structures of the nervous and circulatory systems to enter and exit.

What are the orbits in relation to the skull?

The orbits are the bony sockets that contain and protect the eyes.

What bones make up the orbital complex?

Frontal, sphenoid, maxilla, zygomatic, palatine, ethmoid, and lacrimal.

What is the role of the facial bones in relation to the digestive and respiratory systems?

They protect and support the openings of these systems and the sense organs for vision and smell.

Which bone forms the roof of the orbit?

The frontal bone.

What forms most of the orbital floor?

The maxilla.

What forms the lateral wall and rim of the orbit?

The zygomatic bone, which articulates with the sphenoid and maxilla.

What does the nasal complex include?

The bones that enclose the nasal cavities and the paranasal sinuses.

What is the function of the nasal complex?

It filters, humidifies, and warms inhaled air, and plays a role in defense against airborne pollutants.

Which bones make up the nasal complex?

Nasal, palatine, maxillary, ethmoid, and vomer bones.

What is the composition of the adult vertebral column?

It consists of 26 bones: 24 vertebrae, 1 sacrum, and 1 coccyx.

What are the functions of the vertebral column?

It provides support, protects the spinal cord, and helps maintain an upright body position.

Is the vertebral column straight and rigid?

No, it is not straight and rigid.

What are the four spinal curves in the vertebral column?

The cervical curve, thoracic curve, lumbar curve, and sacral curve.

What are primary curves and when do they appear?

Primary curves are the thoracic and sacral curves that appear in fetal development and are present at birth.

What is the function of primary curves?

They accommodate the thoracic and abdominopelvic viscera (internal organs).

What are secondary curves and when do they develop?

Secondary curves are the cervical and lumbar curves that develop several months after birth.

What is the purpose of secondary curves?

They help shift weight to permit an upright posture.

When are all four spinal curves fully developed?

By age 10.

How many cervical vertebrae are there and what are their designations?

There are seven cervical vertebrae, designated C1-C7.

What is the role of thoracic vertebrae?

Twelve thoracic vertebrae (T1-T12) form the superior portion of the back and articulate with pairs of ribs.

How many lumbar vertebrae are there and what are their designations?

There are five lumbar vertebrae, designated L1-L5.

What does the vertebral body do?

The vertebral body transfers weight along the axis of the vertebral column.

What forms the anterior and posterior margins of the vertebral foramen?

The vertebral body forms the anterior margin, while the vertebral arch forms the posterior margin.

What are the components of the vertebral arch?

The vertebral arch consists of pedicles and laminae.

What is the function of articular processes?

They articulate with the corresponding processes of adjacent vertebrae.

What is the structure of a spinous process?

A spinous process projects posteriorly from where the vertebral laminae fuse.

What are transverse processes and their function?

Transverse processes project laterally and are sites of muscle attachment; they may also articulate with ribs.

What is unique about the transverse processes of vertebrae T1-T10?

They are relatively thick and contain transverse costal facets for rib articulation.

What is the function of the atlas (C1)?

The atlas holds up the head.

What are the characteristics of the human skeleton?

It is strong, light, and adapted for protective, locomotor, and manipulative functions.

What is the primary function of joints in the skeletal system?

Joints provide remarkable mobility to the skeleton.

What is the significance of the C-shape in infants?

It results from the thoracic and sacral curves, which are primary curves.

What happens to the cervical and lumbar curves as a toddler learns to walk?

They become accentuated.

What is the function of the atlas (C1) vertebra?

The atlas holds up the head and articulates with the occipital condyles of the skull.

Why is the atlas named after a Greek mythological figure?

It is named after Atlas, who holds the world on his shoulders.

What anatomical feature is formed by the fusion of the atlas and axis (C2)?

The prominent dens, or odontoid process, of the axis.

What role does the transverse ligament play in the cervical vertebrae?

It binds the dens to the inner surface of the atlas, forming a pivot for rotation of the atlas and skull.

What is the thoracic cage composed of?

The thoracic cage consists of thoracic vertebrae, ribs, costal cartilages, and the sternum.

What are the main functions of the thoracic cage?

It protects the heart, lungs, thymus, and provides sites for muscle attachment.

How many pairs of ribs do humans have?

Humans have 12 pairs of ribs.

What distinguishes true ribs from false ribs?

True ribs (1-7) attach directly to the sternum, while false ribs (8-12) do not.

What are floating ribs?

Floating ribs (11-12) have no connection with the sternum and are attached only to the vertebrae and muscles.

What are the three parts of the sternum?

The three parts are the manubrium, body, and xiphoid process.

What is the role of the appendicular skeleton?

It includes the bones of the limbs and the girdles that connect them to the trunk.

What bones make up the pectoral girdle?

The pectoral girdle consists of two clavicles and two scapulae.

How do the clavicles and scapulae contribute to arm movement?

Movements of the clavicles and scapulae position the shoulder joints and provide a basis for arm movement.

What is the anatomical term for the proximal portion of the upper limb?

The arm, which extends from the shoulder to the elbow.

What is the distal portion of the upper limb called?

The forearm, which extends from the elbow to the wrist.

What is the significance of the thoracic cage in relation to muscle attachment?

It serves as an attachment point for muscles involved in breathing, maintaining the vertebral column, and moving the pectoral girdles.

What type of ribs are ribs 8-10 known as?

They are called vertebrochondral ribs because their costal cartilages fuse with rib pair 7 before reaching the sternum.

What is the shape and location of the manubrium?

The manubrium is broad and triangular, articulating with the clavicles and the first pair of ribs.

What is the xiphoid process?

The xiphoid process is the smallest part of the sternum, attached to the inferior surface of the body.

What is the primary adaptation of the upper limbs?

The bones of the upper limbs are adapted for free movement.

What is the anatomical term for the shoulder blade?

The scapula.

What is the primary function of the thoracic cage?

To protect vital organs in the thoracic cavity.

What is the role of the thoracic vertebrae in the thoracic cage?

They provide structural support and attachment points for the ribs.

What is the only long bone in the arm (brachium)?

The humerus.

What are the main parts of the humerus from proximal to distal?

Head, shaft, and condyle.

Which bones support the forearm (antebrachium)?

The ulna and radius.

In the anatomical position, which bone lies medial to the other in the forearm?

The ulna lies medial to the radius.

What connects the ulna to the radius?

The interosseous membrane.

What are the three main parts of the radius from proximal to distal?

Head of radius, shaft, and radial styloid process.

With which part of the humerus does the head of the radius articulate?

The capitulum.

What are the three main parts of the ulna from proximal to distal?

Olecranon, shaft, and ulnar head.

What is the olecranon?

The proximal end of the ulna, which is the point of the elbow.