Chapter 7: The Skeletal System

Vocabulary-based flashcards covering the anatomy, classification, cell types, and physiological processes of the skeletal system.

Mesenchyme

The embryonic tissue from which all bone and cartilage (connective tissues) are derived.

Mesenchymal cells

Embryonic stem cells destined to become connective tissue that can divide to replace damaged cells.

Articular Cartilage

A layer of hyaline cartilage covering bone ends at joints to minimize friction and absorb shock.

Medullary Cavity

A hollow space within the diaphysis that contains red bone marrow in children and yellow bone marrow in adults.

Periosteum

A tough outer sheet of dense irregular connective tissue anchored to the bone by perforating fibers.

Endosteum

An incomplete layer of cells that covers all internal bone surfaces, such as the medullary cavity.

Hemopoietic

The process of blood cell formation, which occurs within the red bone marrow.

Red Bone Marrow

Tissue containing reticular connective tissue found in spongy bone and the medullary cavity of children; in adults, restricted to the axial skeleton and proximal epiphyses.

Yellow Bone Marrow

A fatty substance that can convert back to red bone marrow during severe anemia to increase red blood cell production.

Compact Bone

Smooth, solid, white bone tissue that constitutes $80 \, \%$ of total bone mass; also known as dense or cortical bone.

Spongy Bone

Porous, honeycomb-like bone tissue internal to compact bone that constitutes $20 \, \%$ of bone mass; also known as cancellous or trabecular bone.

Osteon

The functional basic unit found only in compact bone.

Trabeculae

Latticework structures found only in spongy bone.

Osteoprogenitor Cells

Stem cells derived from mesenchyme that divide to produce cells that evolve into osteoblasts.

Osteoblasts

"Bone builders"; produce the bone matrix.

Osteocytes

“maintence guy” Maintain the matrix; Mature bone cells that reside in lacunae.

Osteoclasts

"Bone crushers"; large cells that dissolve bone (resorption) to release calcium into the blood.

Bone Remodeling

The constant balance between bone deposition (via osteoblasts) and bone resorption (via osteoclasts).

Ossification

The developmental process by which a hyaline cartilage model is transformed into bone.

Interstitial Growth

Growth in bone length occurring at the epiphyseal plate during childhood and puberty.

Appositional Growth

Growth in bone width or thickness resulting in an increased diameter.

PTH (Parathyroid Hormone)

accelerates the kidney's production of calcitriol

Red bone marrow location in children

spongy bone & medullary cavity

Red bone marrow location in adults

axial skeleton & proximal epiphysis

Resorption

the process by which bone is broken down and its minerals released into the bloodstream.

Calcium 4 Purposes

muscle contraction, blood clotting, bone strength, and nerve signaling.

Diploe

spongy bone layer found between between two layers of compact bone in flat bones, which provides structural support and reduces weight.

osteoid

gel like material, a matrix produced by osteoblasts that forms bone. It consists mainly of collagen and serves as the framework for mineralization.

Organic Components of Bone

osteoid, collagen fibers, ground substance

Inorganic Components of Bone

mineral salts, primarily hydroxyapatite

Proteolytic enzymes

released from lysosomes within osteoclaststo break down osteoid and facilitate bone resorption.

Fill in the blank: Spongy bone doesn’t have ____ but does have ____.

osteons, osteocytes

Calcitriol

active form of Vitamin D; stimulates the small intestine to absorb calcium ions from your food into the blood

Epiphyseal Plate Zone 1

zone of resting cartilage where chondrocytes are inactive and maintain the cartilage structure.

Epiphyseal Plate Zone 2

zone of proliferating cartilage where chondrocytes divide and form stacks, contributing to bone elongation.

Epiphyseal Plate Zone 3

zone of hypertrophic cartilage where chondrocytes mature and hypertrophy, facilitating further bone growth.

Epiphyseal Plate Zone 4

zone of calcified cartilage where minerals are deposited, leading to chondrocyte death and eventual bone formation.

Epiphyseal Plate Zone 5

zone of ossification where new bone is formed as blood vessels invade, replacing cartilage with bone tissue.

first step of Vitamin D activation (in the skin)

Ultraviolet (UV) light converts a steroid precursor into Vitamin D3 (cholecalciferol), which is then released into the blood

liver's role in Vitamin D activation

converts Vitamin D3 into an intermediate molecule called calcidiol

Location of final, active form of Vitamin D created

In the kidneys. They convert calcidiol into calcitriol