Bone Tissue and Cells Overview

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which cell type in the skeletal system is involved in the resorption and remodeling of bone tissue?

Osteoblasts

Osteocytes

Osteoclasts (correct)

Osteoprogenitor cells

What constitutes approximately 35% of the dry weight of bone?

Type I collagen (correct)

Hydroxyapatite

Bone marrow

Mineral components

Which characteristic is true for osteoprogenitor cells?

They are derived from embryonic mesenchyme. (correct)

They are multinucleated giant cells.

They cannot undergo mitotic division.

They are found only in matured bone.

Which statement correctly describes the inorganic component of the bone matrix?

It constitutes about 65% of the dry weight of bone. Signup and view all the answers

What is the primary role of osteoblasts in the skeletal system?

To synthesize the organic component of the bone matrix Signup and view all the answers

Where are osteocytes typically found within the bone structure?

In cavities known as lacunae Signup and view all the answers

Which of the following best describes bone tissue's role in metabolism?

It is highly vascularized and metabolically active. Signup and view all the answers

What is the primary reason for the presence of hydroxyapatite crystals in bone tissue?

To serve as a source of calcium and phosphorus Signup and view all the answers

Which type of bone retains its original shape when its organic components are extracted, but becomes extremely brittle?

Mineralized skeleton Signup and view all the answers

What cellular component found in the inner layer of the periosteum has the potential to differentiate into osteoblasts?

Osteoprogenitor cells Signup and view all the answers

What is the primary function of Sharpey's fibers in the periosteum?

To bind the periosteum to the bone Signup and view all the answers

Which of the following structures is found within a typical Harvesian system?

Volkman's canal Signup and view all the answers

What is the primary histological feature distinguishing cancellous (spongy) bone from compact bone?

Interconnecting cavities Signup and view all the answers

What type of marrow is filled within the irregular cavities of cancellous bone?

Red marrow Signup and view all the answers

Which structural feature of bone consists of parallel lamellae containing osteocytes within lacunae?

Trabeculae Signup and view all the answers

What composition primarily makes up the outer layer of the periosteum?

Fibroblasts and collagen fibers Signup and view all the answers

What is the correct sequence of stages in intramembranous osteogenesis?

Mesenchymal cell presence, vascularization, collagen deposition, osteoid calcification Signup and view all the answers

Which artery is primarily responsible for the blood supply to the growing ends of long bones?

Epiphyseal artery Signup and view all the answers

How does the direction of the nutrient foramen relate to the growing ends of long bones?

The growing end is opposite to the direction of the nutrient foramen. Signup and view all the answers

What is a common complication in the healing of fractures?

Delayed union Signup and view all the answers

What misconception might arise regarding the role of osteoblasts in bone formation?

Osteoblasts form new bone by secreting a matrix. Signup and view all the answers

What defines the growing end of a long bone during development?

It forms secondary centers of ossification first. Signup and view all the answers

Which condition is primarily characterized by the softening of bones in children?

Rickets Signup and view all the answers

Which statement about the epiphyses of long bones is true?

Epiphyses at one end always fuse later than the other. Signup and view all the answers

Study Notes

Bone Tissue

Main component of the adult skeleton
Supports fleshy structures and protects internal organs
Site of haematopoiesis (bone marrow production)
Highly vascularized and metabolically active
Reservoir of calcium, phosphate, and other minerals

Bone Cells

Osteoprogenitor cells: Located in the periosteum, haversian canals, and endosteum; derived from embryonic mesenchyme; capable of dividing and differentiating into osteoblasts
Osteoblasts: Formed from osteoprogenitor cells; synthesize the organic component of the bone matrix; possess receptors for parathyroid hormone; found where new bone is forming
Osteocytes: Mature bone cells; transformed from osteoblasts; reside in cavities (lacunae) within the bone matrix; found in mature bone tissue
Osteoclasts: Bone-destroying cells; multinucleated giant cells derived from fused marrow precursors; act as macrophages of bone; involved in bone resorption and remodeling; originate from the fusion of bone marrow-derived mononucleated cells

Bone Matrix

Contains both organic and inorganic components
Extracellular matrix comprises 25% water, 25% fibers, and 50% crystallized minerals
Organic component: Constitutes 35% of the dry weight of bone; primarily composed of type I collagen fibers; type I collagen makes up 80-90% of the organic components
Inorganic component: Constitutes 65% of the dry weight; mainly composed of calcium and phosphorus, along with bicarbonate, citrate, magnesium, sodium, and potassium; calcium and phosphorus exist primarily as hydroxyapatite crystals

Bone Strength

One of the hardest and strongest substances in the body
Decalcified bone (mineral removed) maintains shape but becomes flexible and bendable
Bone without the organic component retains shape but is extremely brittle and easily fractured

Periosteum and Endosteum

Periosteum: Composed of an outer layer of collagen fibers and fibroblasts; Sharpey's fibers (bundles of periosteal collagen) penetrate the bone matrix; inner cellular layer contains osteoprogenitor cells
Endosteum: Covers the internal surfaces of bone; composed of bone-forming cells and connective tissue

Types of Bone Tissue

Compact bone: Dense and solid without cavities
Cancellous bone (spongy bone): Contains numerous interconnecting cavities
Both have the same basic histological structure

Harvesian Canal Systems (Osteon)

Components:
- Central harvesian canal
- Bone lamellae
- Lacunae
- Osteocytes
- Canaliculi
- Volkman's canal (connects two harvesian canals)

Cancellous Bone

Trabeculae: Slender strands of bone tissue forming a framework
Marrow cavities: Filled with hematopoietic tissue (red marrow)
Red marrow consists of developing blood cells, platelets, and adipose cells
Trabeculae composed of parallel lamellae containing lacunae with osteocytes

Differences between Compact and Spongy Bone

Osteogenesis (Ossification)

Intramembranous Osteogenesis:
- Presence of mesenchymal cells at the site of bone formation
- Area becomes highly vascularized
- Mesenchymal cells lay down collagen fibers
- Mesenchymal cells transform into osteoblasts
- Osteoblasts secrete matrix to embed fibers
- Fibres and matrix swell, forming osteoid
- Calcium deposited in osteoid under the influence of osteoblasts
- Osteoid becomes calcified, forming bone lamella
- Additional osteoid layers are laid down, forming more lamellae

Endochondral Osteogenesis

Blood Supply of Bones

Nutrient artery
Periosteal artery
Epiphyseal artery
Metaphyseal artery

Growing End of Long Bones

Epiphyses (ends) fuse at different times in most long bones
The end that fuses later is called the growing end
Secondary centers appear first at the growing end
The growing end is located opposite the direction of the nutrient foramen

Growing End: Direction of Nutrient Foramen

"To the elbow I go and to the knee I flee"
In milking cow position, the direction is always downwards

Clinical Anatomy

Healing of fractures
Osteomalacia/Rickets
Osteoporosis
Osteopetrosis
Bone Tumors/Ganglion

Complications of Healing

Non-union
Mal-union
Delayed union
Osteomyelitis (infection)

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the essential components of bone tissue, including its functions and the types of bone cells. Understand how osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts contribute to the formation and maintenance of bone. This quiz provides insights into the complex structure and functions of the skeletal system.