Bone Structure and Composition

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Questions and Answers

Which tissue is NOT a component of bone?

Muscle tissue (correct)

Epithelial tissue

Cartilage

Adipose tissue

The study of bone structure is called osteology.

True

What is the primary mineral that confers hardness to bone tissue?

hydroxyapatite

The knobby ends of long bones are called __________.

epiphyses Signup and view all the answers

Match the following bone cells with their functions:

Osteoprogenitor cells = Stem cells of bone Osteoblasts = Bone-forming cells Osteocytes = Mature bone cells Osteoclasts = Bone-resorbing cells Signup and view all the answers

Which of the following statements about osteocytes is true?

Osteocytes are responsible for nutrient acquisition. Signup and view all the answers

Spongy bone tissue contains osteons.

False Signup and view all the answers

What is the main structural unit of compact bone?

osteon Signup and view all the answers

The process of bone formation is known as __________.

ossification Signup and view all the answers

Match the following types of bone tissue with their main characteristics:

Compact bone = Densely packed ECM, resistant to mechanical stress Spongy bone = Contains trabeculae, lighter than compact bone Osteoclasts = Cells that catabolize bone Osteoblasts = Cells that secrete collagen and form bone Signup and view all the answers

Which of the following is NOT a step in endochondral ossification?

Formation of trabeculae in spongy bone tissue Signup and view all the answers

Appositional growth only allows bones to grow in length.

False Signup and view all the answers

At what age does the epiphyseal plate typically close in females?

18 years Signup and view all the answers

The _____________ cartilage becomes articular cartilage at joints.

hyaline Signup and view all the answers

Match the following zones of the epiphyseal plate with their characteristics:

Zone of resting cartilage = Anchors epiphyseal plate to bone Zone of proliferating cartilage = Contains actively-dividing chondrocytes Zone of hypertrophic cartilage = Contains large cells arranged in columns Zone of calcified cartilage = Contains layers of dead chondrocytes Signup and view all the answers

Study Notes

Bone Structure and Composition

Bone is an organ composed of osseous tissue, cartilage, dense connective tissue, epithelial tissue, adipose tissue, and nervous tissue.
The study of bone structure is called osteology.
The skeletal system is composed of bones and performs six main functions: support, protection, movement, mineral homeostasis, blood cell production, and triglyceride storage.
Long bones are longer than they are wide and consist of a diaphysis (shaft), epiphyses (ends), metaphyses (connections), articular cartilage, periosteum, medullary cavity, and endosteum.
Bone tissue is a connective tissue composed of sparsely distributed cells in a hard extracellular matrix (ECM).
The ECM of bone consists of water (15%), collagen fibers (30%), and mineral salts (55%).
Mineral salts deposit on collagen fibers, conferring hardness to bone.
Collagen fibers confer tensile strength to bone tissue.
Calcification is the process of mineral salt deposition onto collagen fibers, making bone hard.
The mineral salts of bone ECM include hydroxyapatite, calcium phosphate, calcium hydroxide, and calcium carbonate.
Bone cells make, grow, and remodel bone, comprising only 2% of bone tissue.
Bone cells include osteoprogenitor cells (stem cells), osteoblasts (ECM-secreting), osteocytes (mature bone cells), and osteoclasts (bone-resorbing).

Bone Tissue Types

There are two types of bone tissue: spongy and compact bone tissue.
Compact bone tissue is the strongest, densely packed, and resistant to mechanical stress.
The structural unit of compact bone is the osteon, arranged along lines of stress.
Osteonic canals contain blood vessels, supplying nutrients and hormones.
Concentric lamellae are rings of ECM surrounding the osteonic canal.
Interstitial lamellae are remnants of old concentric lamellae from old osteons, found between existing osteons.
Circumferential lamellae surround the long bone, joined to the periosteum via perforating fibers.
Osteocytes occupy spaces called lacunae in the ECM.
Canaliculi are channels allowing communication between osteocytes, filled with extracellular fluid.
Interosteonic canals provide passage for blood vessels and nerves, penetrating bone from the periosteum to the medullary cavity.

Spongy Bone Tissue

Spongy bone tissue is not made of osteons, but of trabeculae (plates or projections of bone tissue) arranged along areas of stress.
Trabeculae are surrounded by red bone marrow and blood vessels, containing blood stem cells.
Spongy bone tissue is lighter than compact bone, supporting and protecting bone marrow, and handling stress along multiple axes.

Nerve and Blood Supply of Bone

Bone is well vascularized, with periosteal arteries nourishing the periosteum.
Nutrient arteries penetrate the diaphysis, branching into bone marrow and entering through the nutrient foramen.
Epiphyseal and metaphyseal arteries nourish the internal tissues of the epiphyses, branching from the nutrient artery.
Veins exit via the same entrance as the cognate arteries.
Nerves run similar paths to blood vessels through bones.

Ossification

Ossification is the process of bone formation, occurring in four phases: development of the embryonic skeleton, development during childhood and adolescence, bone remodeling, and fracture repair.
The embryonic skeleton is initially composed of mesenchymal tissue.
Ossification proceeds in two patterns: intramembranous ossification (bone develops directly from mesenchymal tissue) and endochondral ossification (bone develops from hyaline cartilage).

Intramembranous Ossification

Intramembranous ossification forms the embryonic cranium and facial bones.
It proceeds in four steps: formation of the ossification center, calcification, formation of trabeculae, and formation of the periosteum.
Bone forms directly from mesenchymal tissue, making both spongy and compact bone tissue.

Endochondral Ossification

Endochondral ossification forms most bones, including long bones.
It proceeds in six steps: mesenchymal cells differentiate into chondroblasts, chondroblasts secrete ECM, penetration of nutrient artery stimulates osteoblast formation, primary ossification extends towards the ends of bones, secondary ossification center forms at birth, and hyaline cartilage at joints becomes articular cartilage.

Bone Growth

Bones can grow interstitially (lengthwise) or appositionally (circumferentially).
Interstitial growth occurs at the epiphyseal plate of long bones, subdivided into four zones: resting cartilage, proliferating cartilage, hypertrophic cartilage, and calcified cartilage.
At maturity, the epiphyseal plate closes, chondrocytes cease to divide, and the ECM calcifies leaving an epiphyseal line.
Appositional growth involves four steps: periosteal cells become osteoblasts, ridges of ECM form around periosteal vessels, ridges fuse, and endosteal osteoblasts secrete ECM.

Factors Affecting Bone Growth

Bone growth is affected by nutrition, hormones, and exercise.
Growth factors, thyroid hormones (T3 and T4), estrogen, and testosterone affect bone growth rates.
Weight-bearing exercise stimulates bone remodeling, while a sedentary lifestyle or injury leads to bone loss.

Bone Remodeling

Bone remodeling is a dynamic, lifelong process involving bone resorption (destruction of ECM) and deposition (building new ECM).
Bone is remodeled during growth, injury, and with changes in exercise and diet.
Osteoclasts resorb bone, releasing minerals into the blood.
Osteoblasts deposit bone along lines of mechanical stress.
Bone remodeling is essential for calcium homeostasis, with bone storing 99% of the body's calcium.
Low calcium levels can lead to heart and respiratory dysfunction.

Fractures and Bone Repair

Fractures are breaks in bones, ranging from microscopic stress fractures to large compound fractures.
Fractures are caused by trauma, repeated stressful activities, and disease.
Fractures are treated by reduction, closed or open, to realign the bone ends and initiate healing.
Bone repair proceeds in three phases: reactive phase (hematoma formation and inflammation), reparative phase (fibrocartilaginous callus formation and bony callus formation), and bone remodeling phase.

Bone Disorders

Osteoporosis is a loss of bone density, leading to increased fracture risk.
Rickets (childhood) and osteomalacia (adult) are caused by vitamin D deficiency, leading to soft and deformed bones.

Summary

Bones are the organs of the skeletal system.
Two types of bone tissue exist: spongy and compact.
Ossification occurs through intramembranous or endochondral processes.
Bone growth is influenced by nutrition, hormones, and exercise.
Bone remodeling is a vital lifelong process for calcium homeostasis and adaptation.

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Description

Explore the intricate anatomy and functions of bones in this quiz. Delve into the various types of tissues that comprise bones and the essential roles they play in the skeletal system. Ideal for students studying osteology and related subjects.