Skeletal System Overview

Overview of the Skeletal System

• The human body has approximately 206 bones and cartilage, which combine to make the skeleton system.
• The main parts of the skeleton include the axial and appendicular skeleton.

Axial Skeleton

• The bodies longitudinal axis protects underlying organs.
• The skull contains 22 bones; 8 cranial and 14 are facial bones, that encase the brain and form the face.
• The vertebral column is comprised of 33 bones, 24 individual vertebrae protecting the spinal cord; remaining vertebrae fuse, forming the sacrum and coccyx.
• The thoracic cage or rib cage contains 12 pairs of ribs, sternum and part of the vertebral column; encases and protects lungs, heart, and contents of the thoracic cavity.

Appendicular Skeleton

• Consists of bones of the pectoral girdle, upper limb, pelvic girdle and lower limb
• Provides movement, support and muscle attachment.
• The pectoral girdle consists of the clavicle and scapula, which anchors the upper limit to the trunk.
• The upper limb has three parts: the arm (humerus), forearm (radius and ulna) and wrist and hand (carpals, metacarpals and phalanges).
• Pelvic girdle contains two pelvic bones and the sacrum, collectively called the pelvis, which anchors the lower limb to the trunk,
• Lower limb has three parts: thigh (femur), leg (tibia and fibula), and ankle and foot (tarsals, metatarsals, and phalanges).

Bone Markings

• Bones are marked with surface features, demonstrating the structure-function relationship of skeletal muscles.
• Depressions enable pathways for blood vessels and nerves, and points of articulation or joints between bones.
• Openings enclose structures which enable them to travel through bones.
• Projections establish areas where bones articulate, or points of attachment for ligaments and tendons.

Skull Structure

• Contains 22 bones in 2 groups: -Cranial bones (cranium) consists of eight bones: -Four single bones: frontal, occipital, ethmoid, and sphenoid. -Two paired bones: temporal and parietal.

Facial Bones

• Facial bones form the framework of the face. -Six paired bones: maxillary, zygomatic, nasal, lacrimal, palatine, and inferior nasal conchal bones. -Two single bones: mandible and vomer.
• All skull bones are fused to one another at immovable joints (sutures), except for the mandible.
• Several skull bones contain air-filled, membrane-lined spaces called sinuses, and the four bones surrounding the nasal cavity contain large sinuses (paranasal sinuses).

Overview of Skull Structure

• The cranial vault or calvarium constitutes the superior portion of the cranial cavity.
• The cranial base forms the inferior portion and is split into three indentations (anterior, middle and posterior cranial fossa).
• The cranial cavity surrounds the brain and houses special sense organs in small cavities.
• Orbits contain eyeballs.
• The nasal cavity houses sense receptors for smell.
• The oral cavity surrounds the teeth and tongue.

Fetal Skull

• Fetal skull bones are not fused.
• Soft spots (fontanels) are membranous areas between fetal cranial bones; these areas remain until the child's cranial bones complete development at 18-24 months.
• Fontanels and unfused sutures enable greater flexibility; enables skull to fit through the vaginal canal during birth, and allows skull to enlarge with normal brain growth.
• The anterior fontanel is between developing frontal and parietal bones, where coronal and sagittal sutures meet and the metopic suture divides the frontal bone (fuses at birth to form single bone).
• Posterior fontanel exists between the developing parietal and occipital bones at apex of lambdoid suture.
• Sphenoid fontanels are defined on the left and right sides of the temple where the sphenoid bone meets other cranial bones.

The Hyoid Bone

• The hyoid bone groups with the skull because of it's proximity, although it doesn't articulate with any skull bones.
• The hyoid is a C-shaped bone is in the superior neck, it suspends temporal bones and the larynx.
• It provides several points of attachment for muscles involved in swallowing and speech.

Forensic Skull Anatomy

• Forensic investigators can identify human remains from bones using clues from the skull.
• One of the most basic traits that can be determined from the skull is gender.
• Characteristics that can differentiate gender include: -The forehead of a male skull slopes, while a female forehead is straight. -A males ridge above the eye (Supraorbital ridge) is more prominent. -Female mandibular angle is generally greater than 90 degrees.
• Males typically have larger mastoid process.
• Forensic science can determine age and ethnic heritage using sutures.

Vertebral Column

• Vertebral column (spine) has an average of 33 bones (vertebrae)
• Vertebrae are classified by structure and location. Each individual vertebra is given a letter of which region it belongs to and a number position.
• Spaces between vertebrae are called the intervertebral foramen and allow spinal nerve roots to pass through.

Vertebral Classification:

• Vertebral classification of the 7 cervical vertebrae located in the neck, the fourth cervical vertebra is abbreviated C4.
• There are 12 thoracic vertebrae articulate with ribs, and the eleventh thoracic vertebra is abbreviated T11.
• Lumbar vertebrae consist of 5 bones in the lower back.
• Sacrum vertebrae consists of 5 fused bones that articulate with pelvic.
• The coccygeal spine contains 3 to 5 fused bones at the inferior end of vertebral column

Spinal Curvatures

• Spinal curvatures C-shaped vertebral column of newborn develops into arrangement of secondary curvatures.
• Primary curvatures (thoracic and sacral) are present during fetal period of development.
• Secondary curvatures (cervical and lumbar) are developed after after fetal period,
• Secondary developments are critical for the species ability to walk upright. -Cervical curvature enables heads up, lumbar curves shift weight of body onto sacrum. -These curves lend balance and support needed to walk.
• Scoliosis involves abnormal lateral curvatures in vertebral column
• Lordosis (swayback) involves exaggerated cervical and lumbar curvatures. kyphosis involves exaggeration of thoracic curvature resulting in hunchback appearance.

Structure of the Vertebrae

• Vertebrae generally reflect the functions of the spinal cord supporting both the protection and support of the head and neck
• The body and centrum provide the primary weight-bearing surface and most anterior aspect. The intervertebral discs are placed between adjacent bodies.
• Vertebral foramen has an opening in which spinal cord and other associated tissues travel.
• Vertebral foramina aggregate to form vertebral canal.
• Two pedicles along two laminae are on the posterior vertebral foremen.

Vertebral Articulation

• Transverse processes project from the lateral sides of the vertebral arch.
• Spinous processes project from most posterior aspect of vertebral arch.
• Sacrum consists of 5 fused sacral vertebrae.

Sacrum

• The sacrum is a posterior boundary of pelvic cavity.
• The superior surface articulates with the fifth lumbar and the facets of superior articular processes.
• The sacral Promontory is at the anterior margin.
• Alae are two smooth regions lateral to sacral promontory.
• The inferior surface (apex) articulates with coccyx and the anterior exhibits transverse lines where vertebrae fuse together.
• The sacral crest is where the posterior surface for nerve roots and tissues are allowed passage.

Coccyx

• Coccyx contains four fused vertebrae or between three and five vertebrae that form segment of vertebral column.
• Transverse ridges on posterior are remnants of transverse processes and coccygeal cornu is hornlike- projections on each side of superior aspect from coccyx.

Intervertebral Discs

• 23 Intervertebral discs pads of fibrocartilage are between vertebrae and absorb any shocks and vibrations.
• These discs contains different components namely: -Nucleus pulposus: soft, inner jelly substance that helps absorb impact to adjacent bones. -Anulus Fibrosus: Outer ring of fibrocartilage surrounding nucleus joining different vertebrae.

Herniated Disc

Tear can appear on annulus, nucleus pulposus, and compress nerve roots causing inflammation.

• There are many herniated disc treatments such as anti inflammatory medication, exercise, or repair surgery.
• When the nucleus pulposus protrudes, and causes trauma this is known as a slipped disc.
• Anulus Fibrosus tears on posterolater.

Thoracic Cage

• The thoracic cage protects the rib cage as well as the periphereal boundary.
• Flattened sternums the anterior median section of the thoracic cage, and the manubrium superiormost segment.
• Intercostal spaces create gaps between ribs
• There are also costal cartilages to the thoracic vertebrae posteriorly.
• Rib cage- ribs come into C-shape form.
• It is grouped into two classes called True and False.

Ribs

• Ribs 1-7 that attach to the sternum are called vertebrosternal ribs.
• Ribs 8-12 (false ribs) that aren’t directly attached to the sternum: -Vertebrochondral ribs 8–10 attach to cartilage of seventh rib. -Ribs 11 and 12 (floating or vertebral) aren't attached to sternum.

Cardiopulmonary Resuscitation

• Helps people receive breathing assistance.
• CPR helps restore circulation.
• Correct placement of hands on sternum is critical to ensure the sternal body is positioned correctly.
• Compressions done on xiphoid can cause injuries and even break off.