Chapter 6: The Skeletal System

Practice vocabulary flashcards for Gerard J. Tortora and Bryan H. Derrickson, Introduction to the Human Body, 11th Edition, Chapter 6: The Skeletal System.

Osseous tissue

Another name for bone tissue, which is one of the various tissues that make up a bone organ.

Skeletal system

The entirety of the bones and their cartilage.

Red bone marrow

A connective tissue within certain bones that produces red blood cells, white blood cells, and platelets.

Yellow bone marrow

Bone marrow that consists mainly of adipose cells, which store triglycerides.

Long bones

Bones that have greater length than width and consist of a shaft and a variable number of ends; they are usually somewhat curved for strength.

Short bones

Bones that are somewhat cube-shaped and nearly equal in length and width, such as most wrist and ankle bones.

Flat bones

Thin bones that afford considerable protection and provide extensive surfaces for muscle attachment, including the cranial bones, sternum, ribs, and scapulae.

Irregular bones

Bones with complex shapes that cannot be grouped into categories like long, short, or flat; examples include the vertebrae and some facial bones.

Diaphysis

The bone’s shaft or body.

Epiphyses

The distal and proximal ends of the bone.

Metaphyses

The regions where the diaphysis joins the epiphyses.

Articular cartilage

A thin layer of hyaline cartilage covering the regions of the epiphyses where the bone articulates with other bones.

Periosteum

A sheath of dense irregular connective tissue and blood vessels that surround the parts of the bone outside of the articular cartilage.

Medullary cavity

A hollow space within the diaphysis that contains fatty yellow bone marrow.

Endosteum

The thin membrane that lines the medullary cavity.

Bone extracellular matrix

Composed of approximately $25\%$ water, $25\%$ collagen fibers, and $50\%$ crystallized mineral salts.

Osteoprogenitor cells

Stem cells that develop into osteoblasts.

Osteoblasts

Cells that synthesize and secrete the extracellular matrix that calcifies into bone.

Osteocytes

The most numerous cells in bone tissue that maintain bone tissues.

Osteoclasts

Cells that break down extracellular matrix to release nutrients, help bones grow, and heal.

Compact bone

Denser bone tissue arranged in osteons that makes up $80\%$ of the skeleton; provided for strength and protection.

Osteon

Functional unit of compact bone containing an osteonic canal for blood supply, rings of concentric lamellae, and lacunae.

Spongy bone

Bone tissue arranged irregularly in trabeculae with cavities filled with red bone marrow; makes up $20\%$ of the skeleton for lightness.

Ossification

The process of bone formation, also called osteogenesis.

Intramembranous ossification

A pattern of bone formation where bone forms directly within mesenchyme arranged in sheetlike layers.

Endochondral ossification

A pattern of bone formation where bone forms within hyaline cartilage that develops from mesenchyme.

Bone remodeling

A continuous process where old bone tissue is replaced with new tissue through resorption and deposition.

Bone resorption

The removal of minerals and collagen from bone tissue by osteoclasts.

Bone deposition

The addition of minerals and collagen to bone tissue by osteoblasts.

Open (compound) fracture

A break in the bone where the broken ends of the bone protrude through the skin.

Parathyroid hormone (PTH)

A hormone that increases blood $Ca^{2+}$ levels by stimulating osteoclast activity to break down bone matrix.

Calcitonin (CT)

A hormone secreted by the thyroid gland that inhibits bone resorption by osteoclasts.

Axial skeleton

Consists of the $80$ bones that lie around the longitudinal axis of the human body, including the skull, ribs, and vertebrae.

Appendicular skeleton

Contains $126$ bones of the upper and lower limbs and the girdles that connect them to the axial skeleton.

Fontanels

Soft spots between cranial bones in embryos and infants; the largest is the anterior fontanel which closes $18$ to $24$ months after birth.

Osteoporosis

A condition where bone resorption outpaces bone deposition, leading to a decrease in bone mass and increased risk of fractures.