A&P Skeletal System Study Pack

Comprehensive vocabulary flashcards covering bone anatomy, cell types, classification, axial and appendicular skeletal structures, and joint types.

Compact bone

Dense outer bone tissue that provides strength and support.

Spongy bone

Porous inner bone tissue made of trabeculae; lighter than compact bone and often contains red bone marrow.

Periosteum

Tough connective-tissue membrane covering the external surface of bone, except at articular cartilage.

Endosteum

Thin membrane lining internal bone surfaces.

Osteon

Structural unit of compact bone; concentric lamellae surround a central canal.

Lamellae

Layers/rings of bone matrix.

Lacunae

Small spaces in bone matrix that contain osteocytes.

Canaliculi

Tiny channels connecting lacunae and allowing osteocytes to exchange nutrients and wastes.

Trabeculae

Thin plates/struts that form the framework of spongy bone.

Red bone marrow

Site of blood cell formation (hematopoiesis).

Yellow bone marrow

Primarily stores fat.

Osteoblast

Bone-building cell; secretes new bone matrix.

Osteoclast

Bone-resorbing cell; breaks down bone tissue.

Osteocyte

Mature bone cell that maintains bone matrix.

Bone remodeling

Continuous removal of old bone by osteoclasts and formation of new bone by osteoblasts.

Ossification

Process of bone formation.

Intramembranous ossification

Bone develops directly from mesenchymal tissue; important in many flat bones of the skull.

Endochondral ossification

Bone replaces a cartilage model; forms most bones of the body.

Epiphyseal plate

Growth plate of hyaline cartilage where a long bone grows in length.

Epiphyseal line

Remnant after the growth plate closes.

PTH (Parathyroid hormone)

Raises blood calcium; promotes processes that increase calcium release from bone.

Calcitriol

Active vitamin D; helps increase intestinal calcium absorption.

Fracture healing sequence

Hematoma $\rightarrow$ fibrocartilaginous (soft) callus $\rightarrow$ bony (hard) callus $\rightarrow$ remodeling.

Long bones

Bones longer than wide, consisting of a shaft plus ends; examples include the femur, humerus, radius, ulna, tibia, and fibula.

Short bones

Roughly cube-shaped bones; examples include carpals and tarsals.

Flat bones

Thin, flattened, and often curved bones; examples include the sternum, ribs, scapula, and many skull bones.

Irregular bones

Bones with complex shapes; examples include vertebrae and the sphenoid.

Sesamoid bones

Bones that develop within tendons; the patella is a classic example.

Frontal bone

Cranial bone forming the forehead and anterior skull.

Parietal bones

Paired bones forming the superior and lateral skull.

Temporal bones

Paired bones forming the lateral skull near the ears.

Occipital bone

Posterior/inferior skull bone; contains the foramen magnum.

Sphenoid bone

Butterfly-shaped cranial bone spanning the skull base; contributes to the orbits and houses the pituitary gland in the sella turcica.

Ethmoid bone

Central cranial bone located between the eyes; contributes to the nasal cavity and medial orbit.

Mandible

Lower jaw; the only freely movable skull bone.

Maxillae

Paired bones forming the upper jaw, hard palate, orbit, and nasal cavity.

Zygomatic bones

Paired bones that form the cheekbones and lateral orbit.

Vomer

Unpaired bone forming the inferior/posterior part of the nasal septum.

Foramen magnum

Large opening in the occipital bone for the passage of the spinal cord.

Sella turcica

Depression in the sphenoid bone that houses the pituitary gland.

Cervical vertebrae

The sequence of $7$ vertebrae ($C1-C7$) in the neck, typically characterized by transverse foramina.

Atlas ($C1$)

The first cervical vertebra which supports the skull and lacks a typical body.

Axis ($C2$)

The second cervical vertebra which has a dens (odontoid process) to allow head rotation.

Thoracic vertebrae

The $12$ vertebrae ($T1-T12$) that articulate with the ribs.

Lumbar vertebrae

The $5$ vertebrae ($L1-L5$) with large bodies for weight bearing.

True ribs

Ribs $1-7$; they attach directly to the sternum through their own costal cartilage.

False ribs

Ribs $8-12$; they do not attach directly to the sternum.

Floating ribs

Ribs $11-12$; a subset of false ribs with no anterior attachment to the sternum.

Manubrium

The superior part of the sternum.

Xiphoid process

The small inferior portion of the sternum.

Clavicle

The collarbone; connects the upper limb to the axial skeleton anteriorly.

Scapula

The shoulder blade.

Glenoid cavity

The shallow socket of the scapula that articulates with the head of the humerus.

Radius

The lateral forearm bone in anatomical position, located on the thumb side.

Ulna

The medial forearm bone in anatomical position, located on the pinky side.

Olecranon

The proximal portion of the ulna that forms the point of the elbow.

Hip (coxal) bone

Bone formed by the fusion of the ilium, ischium, and pubis.

Ischium

The posteroinferior portion of the hip bone; the part you bear weight on when sitting.

Acetabulum

The cup-shaped socket of the hip bone receiving the head of the femur.

Tibia

The medial, larger weight-bearing bone of the lower leg.

Fibula

The lateral, slender bone of the lower leg that bears much less weight than the tibia.

Synovial joint

A freely movable joint containing a joint cavity; examples include ball-and-socket, hinge, and pivot joints.