skeletal system - unit 7

unit 7

The Skeleton

Includes approximately 206 bones and associated skeletal cartilages at joints or articulations.

Skull

The skeleton’s most complex structure with 22 bones, including 8 cranial and 14 facial bones.

Vertebral Column

Includes 33 vertebrae; top 24 encase the spinal cord, and the sacrum and coccyx are inferior fused bones.

Thoracic (Rib) Cage

Includes 12 pairs of ribs, the sternum, and part of the vertebral column; protects structures in the thoracic cavity.

Pectoral Girdle

Includes the clavicle and scapula; supports the upper limb and anchors it to the trunk.

Pelvic Girdle

Includes 2 pelvic bones and the sacrum; supports the lower limb and anchors it to the trunk.

Axial Skeleton

The longitudinal axis of the body, structured for protection, including the skull, vertebral column, and thoracic cage.

Appendicular Skeleton

Comprises the bones of the girdles and the upper and lower limbs, structured for motion.

Bone Markings

Surface features of bones, including depressions, openings, and projections.

Facet

A shallow convex or concave surface where two bones articulate.

Fossa

An indentation in a bone into which another structure fits.

Foramen

A hole in a bone that allows blood vessels and nerves to travel through.

Condyle

A rounded end of a bone that articulates with another bone.

Crest

A ridge or projection on a bone.

Tubercle

A small, rounded bony projection.

Tuberosity

A large tubercle.

Epicondyle

A small projection usually proximal to a condyle.

Sutures

Immoveable joints uniting all skull bones in adults, except the mandible.

Cranial Cavity

The space within the skull that surrounds the brain.

Paranasal Sinuses

Air-filled, membrane-lined spaces within the frontal, sphenoid, ethmoid, and maxillary bones that lighten the skull and enhance voice resonance.

Fontanels (Soft Spots)

Membranous areas in a fetal skull where ossification is not complete, providing flexibility during birth.

Anterior Fontanel

A membranous area in the fetal skull located between developing frontal and parietal bones.

Hyoid Bone

A small, C-shaped bone suspended in the superior neck by muscles and ligaments, serving as an attachment point for muscles involved in swallowing and speech.

Cervical Vertebrae

The 7 vertebrae located in the neck, characterized by transverse foramina.

Thoracic Vertebrae

The 12 vertebrae that articulate with the ribs, featuring superior and inferior costal facets.

Lumbar Vertebrae

The 5 largest and heaviest vertebrae located in the lower back, designed to bear the weight of the torso.

Sacrum

Composed of 5 fused sacral vertebrae (S1-S5) that form the posterior wall of the pelvic cavity.

Coccyx

Generally composed of 3–5 fused coccygeal vertebrae, located at the most inferior end of the vertebral column.

Primary Spinal Curvatures

The thoracic and sacral curvatures, which are present during the fetal period.

Secondary Spinal Curvatures

The cervical and lumbar curvatures, which develop after the fetal period.

Scoliosis

Abnormal lateral curvatures of the spine that appear C or S shaped.

Lordosis (Swayback)

Exaggerated cervical and lumbar curvatures of the spine.

Kyphosis (Humpback)

An exaggerated thoracic curvature of the spine.

C1 Atlas

The first cervical vertebra, named for the Greek Titan, which supports the skull.

C2 Axis

The second cervical vertebra, from which the Dens (Odontoid Process) projects, fitting into the atlas’s vertebral foramen.

Dens (Odontoid Process)

A projection from the body of the C2 Axis that fits into the atlas's vertebral foramen, forming the atlantoaxial joint.

C7 (Vertebra Prominens)

The seventh cervical vertebra, characterized by a unique, longer, unforked spinous process that is palpable and used as a clinical landmark.

Vertebral Compression Fracture

A fracture of the vertebral body that reduces the height of the vertebra by more than 20%.

Intervertebral Discs

Pads located between vertebrae, consisting of a jelly-like nucleus pulposus and an outer ring of fibrocartilage (anulus fibrosus).

Nucleus Pulposus

The inner, jelly-like shock absorber portion of an intervertebral disc.

Anulus Fibrosus

The outer ring of fibrocartilage that holds the nucleus pulposus and vertebrae together within an intervertebral disc.

Herniated (Slipped) Disc

A tear in the anulus fibrosus that allows the nucleus pulposus to protrude, often resulting in nerve compression.

Cardiopulmonary Resuscitation (CPR)

A life-saving technique involving repeated compressions to the chest over the sternum to restore circulation.

Xiphoid Process

The inferior tip of the sternum, which should be avoided during CPR to prevent damage to underlying organs.

Clavicle

An S-shaped bone in the pectoral girdle; its medial sternal end articulates with the manubrium, and its lateral acromial end articulates with the scapula.

Sternoclavicular Joint

The joint formed where the medial sternal end of the clavicle articulates with the manubrium.

Acromioclavicular Joint

The joint formed where the lateral acromial end of the clavicle articulates with the acromion process of the scapula.

Pelvis

A structure consisting of two pelvic bones, the sacrum, and the coccyx, forming the Pelvic Inlet and surrounding the Pelvic Brim.

Pelvic Inlet

The oval-shaped opening formed by the sacrum and pelvic bones, surrounded by the pelvic brim.

Greater (False) Pelvis

The region superior to the pelvic brim.

Lesser (True) Pelvis

The region inferior to the pelvic brim.

Pubic Arch

The angle formed by the inferior rami of the pubic bones, typically wider in females (90-100 degrees) and narrower in males (60-70 degrees).

Arches of the Foot

Three arches (medial longitudinal, lateral longitudinal, and transverse) supported by ligaments and muscles that prevent the foot from resting flat on the ground.

Medial Longitudinal Arch

An arch on the medial side of the foot, extending from the calcaneus to the metatarsals.

Lateral Longitudinal Arch

An arch on the lateral side of the foot, extending from the calcaneus to the metatarsals.

Transverse Arch

An arch in the middle of the foot, involving the distal tarsals and bases of all five metatarsals.

Tibia

The thick, inner bone of the leg.

Fibula

The lateral bone of the leg.

Patella

A plate-shaped bone commonly known as the kneecap.