Chapter 7: Skeletal System Lecture

Vocabulary flashcards covering the key terms, structural organization, cellular types, bone formation processes, anatomical divisions, and joint classifications from Chapter 7: Skeletal System.

Tooth Enamel

The hardest natural substance in the body, which is harder than bone and not classified as bone.

Bone

The second hardest natural substance in the body; a connective tissue composed of cells embedded in a hydroxyapatite crystalline matrix storing calcium, magnesium, and phosphorus.

Osteoblast

An immature, bone-forming cell responsible for secreting and laying down new bone matrix.

Osteocyte

A mature bone cell residing inside a lacuna that carries out metabolic maintenance, brings in nutrients and oxygen, and maintains the surrounding bone tissue.

Osteoclast

A bone cell responsible for breaking down, resorbing, or chewing up old and damaged bone during repair and remodeling.

Ossification

The process of hardening and calcifying the matrix of connective tissue to form bone.

Lacunae

Small spaces or cavities within the ossified bone matrix that house individual osteocytes.

Canaliculi

Tiny tendrils or cytoplasmic channels radiating from lacunae that allow osteocytes to receive nutrients and exchange waste products.

Hematopoiesis

The technical medical term for blood cell formation, which occurs within the bone marrow.

Cancellous Bone

Also called spongy bone; a lighter form of bone containing tiny, deliberately aligned spicules that remodel in response to physical stress and weight loads.

Compact Bone

A heavy, dense type of bone that forms the weight-bearing outer shell of bones and the primary thickness of shafts.

Nutrient Foramina

Openings or holes penetrating through the bone cortex that permit blood vessels from the periosteum to enter the bone.

Volkmann's Canals

Horizontal, lateral channels penetrating the bone matrix at right angles to bring blood vessels from the periosteum into Haversian systems.

Haversian Canals

Longitudinal canals running lengthwise through compact bone that carry blood vessels, lymphatics, and nerves.

Haversian System

The structural unit of compact bone consisting of concentric rings of ossified matrix and osteocytes surrounding a central Haversian canal.

Periosteum

The membrane covering the outer surface of bone, featuring a dense, fibrous outer layer and an osteoblast-rich inner layer that responds to trauma or stress.

Endosteum

The cellular membrane lining the internal hollow surfaces of bone, including the marrow cavity and cancellous bone.

Intramembranous Bone Formation

A bone formation pathway where bone develops directly from a fibrous tissue membrane, occurring primarily in certain flat bones of the skull.

Endochondral Bone Formation

The primary bone formation mechanism in which a pre-existing cartilage template gradually calcifies and is replaced by ossified bone.

Epiphysis

The extremity or end of a long bone, serving as a secondary growth center during endochondral ossification.

Diaphysis

The central shaft of a long bone, which acts as the primary growth center during development.

Epiphyseal Plate

Also called the growth plate; a cartilaginous band located between the epiphysis and diaphysis where cartilage cells continuously proliferate and ossify to lengthen long bones until maturity.

Red Bone Marrow

Metabolically active, hematopoietic marrow that manufactures blood cells, predominant in young, growing animals.

Yellow Bone Marrow

Adipose-rich marrow found primarily in mature animals that can revert to red bone marrow during times of elevated demand for blood cells.

Axial Skeleton

The skeletal division situated along the central midline axis of the body, including the skull, vertebral column, ribs, and sternum.

Appendicular Skeleton

The skeletal division consisting of the appendages, specifically the bones of the thoracic and pelvic limbs.

Visceral Skeleton

Bones that develop within soft tissue organs, such as the heart, penis, or snout in certain species.

Atlas

The first cervical vertebra ($C1$) located directly beneath the skull, named after the mythical figure because it supports the weight of the head.

Axis

The second cervical vertebra ($C2$) featuring the dens process, which serves as a pivot point for the rotation of the atlas.

Thoracic Vertebrae

Vertebrae located dorsal to the chest cavity whose total number corresponds exactly to the number of pairs of ribs in that species.

Lumbar Vertebrae

Bulky vertebrae located dorsal to the abdominal cavity that bear substantial body weight and serve as sites for major muscle attachment.

Sacral Vertebrae

A series of fused vertebrae forming a single solid structure that creates the roof of the pelvic canal and anchors the pelvis at the sacroiliac joint.

Coccygeal Vertebrae

The vertebrae that comprise the tail of an animal, varying significantly in number across species and breeds.

Costochondral Junction

The anatomical junction where the dorsal bony segment of a rib meets its ventral cartilaginous segment.

Manubrium

The most cranial sternebra of the sternum.

Xiphoid Process

The caudalmost bony process or segment of the sternum.

Antebrachium

The forearm region extending between the elbow and the carpus, comprised of the radius and ulna.

Carpus

The joint formed by two rows of carpal bones, anatomically homologous to the human wrist (commonly referred to colloquially as the knee in horses).

Stifle

The anatomical joint in quadrupeds between the femur and tibia/fibula, homologous to the human knee.

Patella

A large sesamoid bone located within the distal tendon of the quadriceps muscle group to protect it as it crosses the stifle joint.

Sesamoid Bone

A bone that develops inside a tendon in response to repetitive mechanical stress, friction, or injury.

Tarsus

Also called the hock; the pelvic limb joint situated between the crus and metatarsals, homologous to the human ankle.

Cannon Bone

The large, weight-bearing third metacarpal or metatarsal bone in equine limbs.

Splint Bones

The smaller second and fourth metacarpal or metatarsal bones running down either side of the cannon bone in horses.

Os Cordis

A visceral bone that develops over time around the atrioventricular valves of the heart in older horses and cattle due to repetitive tissue stress.

Os Penis

A visceral bone located within the erectile tissue of the penis in male dogs.

Os Rostri

A visceral bone located within the snout or nose of pigs.

Articular Cartilage

A thin layer of smooth hyaline cartilage covering the compact bone at articular joint surfaces to reduce friction and cushion movement.

Fibrous Joint

An immovable joint (synarthrosis) firmly held together by fibrous tissue, such as sutures of the skull or the splint bone attachments in horses.

Cartilaginous Joint

A slightly movable joint (amphiarthrosis) united by fibrocartilage allowing slight rocking motion, such as intervertebral discs, the mandibular symphysis, and the pubic symphysis.

Synovial Joint

A freely movable joint (diarthrosis) characterized by a fluid-filled joint cavity, an articular capsule, and hyaline-covered articular surfaces.

Synovial Fluid

A viscous fluid secreted by the synovial membrane that acts as a shock absorber, contains anti-inflammatory antioxidants, and provides nourishment to avascular articular cartilage.

Ligament

A specialized band of connective tissue derived from the periosteum that connects bone to bone across a joint to provide structural stability.

Tendon

A fibrous connective tissue structure that anchors muscle to bone, pulling on bony levers during contraction.

Flexion

A synovial joint movement that decreases the angle between two articulating bones.

Extension

A synovial joint movement that increases the angle between two articulating bones.

Adduction

A movement of an extremity toward the median plane or midline of the body.

Abduction

A movement of an extremity away from the median plane or midline of the body.

Rotation

The twisting or turning of a body part around its own longitudinal axis.

Circumduction

A movement where the distal end of an extremity moves in a circle around a fixed proximal point.

Acetabulum

The deep cup-like depression on the pelvis (etymologically meaning 'vinegar bowl') that accommodates the head of the femur to form the hip joint.