Skeletal System: Bones, Structures, and Markings – Study Notes

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Skull & Facial Bones, and Bony Structures/Markings

Main Bones of the Skull

The human skull is composed of several bones that protect the brain and form the structure of the face. Some bones are paired, while others are single.

Frontal bone (NOT paired): Forms the forehead.
Parietal bones (paired): Form the sides and roof of the cranium.
Temporal bones (paired): Located at the sides and base of the skull.
Occipital bone (NOT paired): Forms the back and base of the skull; contains the foramen magnum for spinal cord passage.
Sphenoid bone (NOT paired): Forms part of the base of the skull and the sides of the orbits.
Ethmoid bone (NOT paired): Located between the eyes; forms part of the nasal cavity.
Maxillae (paired): Upper jaw bones.
Palatine bones (paired): Form part of the hard palate.
Zygomatic bones (paired): Cheekbones.
Lacrimal bones (paired): Small bones forming part of the eye socket.
Nasal bones (paired): Bridge of the nose.
Vomer bone (NOT paired): Forms part of the nasal septum.
Inferior nasal conchae (paired): Thin, curved bones in the nasal cavity.

Cranial Sutures & Fontanelles

Sutures are immovable joints between skull bones. Fontanelles are soft spots in the infant skull where bones have not yet fused.

Coronal suture: Between frontal and parietal bones.
Lambdoidal suture: Between parietal and occipital bones.
Squamous suture: Between parietal and temporal bones.
Sagittal suture: Between the two parietal bones.
Fontanelles: Anterior & posterior; allow for growth of the skull in infants.

Paranasal Sinuses

Paranasal sinuses are air-filled spaces within certain skull bones, lined with mucous membrane.

Frontal sinus: Located in the frontal bone.
Maxillary sinus: Located in the maxillae.

Vertebrae: Types and Numbers

Classification of Vertebrae

The vertebral column consists of different types of vertebrae, each with a specific number and function.

Cervical vertebrae (7): Neck region; includes the atlas (C1) and axis (C2).
Thoracic vertebrae (12): Upper back; articulate with ribs.
Lumbar vertebrae (5): Lower back; largest vertebrae.
Sacrum: 5 fused vertebrae; forms the back of the pelvis.
Coccyx: 4 fused vertebrae; tailbone.

Vertebral Curvatures

The vertebral column has natural curves that help absorb shock and maintain balance.

Kyphosis: Exaggerated thoracic curve (hunchback).
Lordosis: Exaggerated lumbar curve (swayback).
Scoliosis: Lateral curvature of the spine.

Torso & Upper Extremity Bones

Ribs

The rib cage protects vital organs and supports breathing.

True ribs (1-7 pairs): Attach directly to the sternum.
False ribs (8-12 pairs): Do not attach directly to the sternum.
Floating ribs (11-12 pairs): Do not attach to the sternum at all.

Sternum

Manubrium: Upper portion.
Body: Main central part.
Xiphoid process: Small, cartilaginous lower tip.

Shoulder Girdle & Arm Bones

Clavicle: Collarbone.
Scapula: Shoulder blade.
Humerus: Upper arm bone; includes epicondyle and olecranon fossa.
Radius: Lateral forearm bone; includes radial tuberosity.
Ulna: Medial forearm bone; includes olecranon process.
Carpals: Wrist bones.
Metacarpals (1-5): Palm bones.
Phalanges (1-5): Finger bones; each has proximal, middle, and distal segments.

Pelvic Girdle and Lower Extremity

Coxal Bones

The pelvic girdle supports the lower limbs and protects pelvic organs.

Ilium: Largest part; includes iliac crest.
Ischium: Lower, posterior part.
Pubis: Anterior part; includes pubic symphysis.

Femur and Associated Structures

Femur: Thigh bone; includes greater trochanter.
Patella: Kneecap.
Tibia: Larger lower leg bone; includes tibial tuberosity and medial malleolus.
Fibula: Smaller lower leg bone; includes lateral malleolus.

Foot Bones

Tarsals: Ankle bones.
Metatarsals (1-5): Foot bones.
Phalanges (1-5): Toe bones; each has proximal, middle, and distal segments.

Anatomy of a Long Bone

Structure of a Long Bone

Long bones are characterized by a shaft and two ends, and are crucial for movement and support.

Diaphysis: Shaft of the bone; provides strength.
Epiphysis: Proximal and distal ends; involved in joint formation.
Articular cartilage: Covers joint surfaces; reduces friction.
Medullary cavity: Central cavity; contains bone marrow.

Table: Types and Numbers of Vertebrae

Type	Number	Location
Cervical	7	Neck
Thoracic	12	Upper back
Lumbar	5	Lower back
Sacrum	5 (fused)	Pelvis
Coccyx	4 (fused)	Tailbone

Table: Segments of Phalanges

Segment	Description
Proximal	Closest to the body
Middle	Between proximal and distal
Distal	Farthest from the body

Example: The humerus is a long bone of the upper arm, articulating with the scapula at the shoulder and the radius and ulna at the elbow.

Additional info: The above notes expand on the brief list format by providing definitions, anatomical context, and examples for each bone and structure mentioned.