Bone Tissue Composition and Function

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Questions and Answers

What is the primary inorganic component of the extracellular matrix in bone?

Calcium salts (correct)

Osteocalcin

Proteoglycans

Collagen fibers

Which cell type is responsible for bone formation?

Osteoclasts

Chondrocytes

Osteocytes

Osteoblasts (correct)

What is the main function of osteocytes in bone tissue?

Maintain the bone matrix (correct)

Stimulate osteoclast activity

Regulate calcium absorption

Initiate bone formation

Which of the following best describes the organic matrix of bone?

It contains collagen fibers and proteoglycans. Signup and view all the answers

What role do osteoclasts play in bone tissue?

Bone resorption Signup and view all the answers

Which organic component is crucial for recruiting calcium ions in bone tissue?

Proteoglycans Signup and view all the answers

How does the absence of the organic matrix affect bone properties?

Results in brittleness Signup and view all the answers

What are the small cavities where osteocytes reside called?

Lacunae Signup and view all the answers

What is the primary structural unit of compact bone called?

Osteon Signup and view all the answers

Which component of the osteon houses blood vessels and nerves?

Central Canal Signup and view all the answers

How do the collagen fibers in lamellae contribute to bone strength?

They have alternating orientations in adjacent lamellae. Signup and view all the answers

What is the role of canaliculi in the bone structure?

They allow for nutrient and waste exchange. Signup and view all the answers

What describes the structure of spongy bone?

Composed of trabeculae forming a porous structure. Signup and view all the answers

What initiates the intramembranous ossification process?

Differentiation of mesenchymal cells into osteoblasts. Signup and view all the answers

Which of the following bones typically form through intramembranous ossification?

Most of the skull and clavicles. Signup and view all the answers

What characterizes trabeculae in spongy bone?

They create a network that houses marrow. Signup and view all the answers

What primarily drives the process of bone deposition?

Osteoblasts Signup and view all the answers

What is the main function of calcitonin in the body?

Lower blood calcium levels Signup and view all the answers

Which hormone acts to increase calcium levels in the blood?

Parathyroid Hormone (PTH) Signup and view all the answers

What occurs first in the process of bone repair after a fracture?

Hematoma formation Signup and view all the answers

How does vitamin D contribute to bone health?

Facilitates intestinal absorption of calcium Signup and view all the answers

What type of cells are responsible for inhibiting bone resorption?

Osteoblasts Signup and view all the answers

What condition can arise from a deficiency in vitamin D?

Rickets Signup and view all the answers

Which process occurs after soft callus formation during bone healing?

Hard callus formation Signup and view all the answers

What is the primary role of osteoblasts during bone formation?

To secrete osteoid and mineralize it to form bone Signup and view all the answers

Which sequence correctly describes the initial steps of endochondral ossification?

Differentiation of chondroblasts, vascularization, formation of the bone collar Signup and view all the answers

What happens to chondrocytes during the early stages of endochondral ossification?

They lose their nutrient supply and die Signup and view all the answers

What structure is primarily formed by the osteoblasts surrounding the diaphysis of the cartilage model?

Bone collar Signup and view all the answers

What is the significance of the periosteum in bone development?

It differentiates into osteoblasts and lays down compact bone Signup and view all the answers

What does the term 'spongy bone' refer to in the context of bone structure?

The inner network of trabeculae formed during early ossification Signup and view all the answers

What remains of the cartilage model after the completion of ossification?

The growth plates and articular cartilage persists Signup and view all the answers

Which statement accurately reflects a key characteristic of endochondral ossification?

It starts with a cartilage model that is gradually replaced by bone Signup and view all the answers

What type of bone is primarily formed through intramembranous ossification?

Flat bones Signup and view all the answers

Which model is utilized during endochondral ossification?

Hyaline cartilage Signup and view all the answers

In which zone of the epiphyseal plate do chondrocytes enlarge and mature?

Zone of Hypertrophy Signup and view all the answers

What process occurs at the outer surface of the bone during appositional growth?

Bone deposition by osteoblasts Signup and view all the answers

When does longitudinal growth of long bones typically cease?

Late adolescence or early adulthood Signup and view all the answers

What is the first type of bone to form in intramembranous ossification?

Spongy bone Signup and view all the answers

What happens to chondrocytes in the zone of calcification within the epiphyseal plate?

They die and their matrix calcifies Signup and view all the answers

What type of bones are formed through endochondral ossification?

Long and short bones Signup and view all the answers

What is the primary function of appositional growth in bones?

It helps maintain bone strength by adapting to stress. Signup and view all the answers

Which hormone directly promotes appositional growth in bones?

Testosterone Signup and view all the answers

What role do osteoclasts play in bone remodeling?

Breaking down bone tissue Signup and view all the answers

How does growth hormone (GH) influence longitudinal bone growth?

By stimulating chondrocyte division in the epiphyseal plate. Signup and view all the answers

What occurs as a result of appositional growth in the bones?

The medullary cavity enlarges as bone width increases. Signup and view all the answers

Which of the following factors does NOT influence appositional growth?

Medullary cavity size Signup and view all the answers

What is a potential consequence of excess growth hormone production after epiphyseal closure?

Acromegaly Signup and view all the answers

Which statement best describes bone resorption?

It releases calcium ions into the bloodstream. Signup and view all the answers

Study Notes

Inorganic Matrix

Constitutes about 65% of bone weight
Primarily calcium salts (hydroxyapatite)
Other minerals present: phosphorus, bicarbonate, potassium, magnesium, and sodium salts
Provides hardness and strength to bone, crucial for compressive forces

Organic Matrix

Constitutes about 35% of bone weight
Primarily collagen fibers (type I) providing tensile strength and flexibility
Contains: proteoglycans, glycosaminoglycans, glycoproteins, and bone-specific proteins (e.g., osteocalcin)
Proteins and proteoglycans recruit calcium and bind matrix components
Collagen resists twisting and tensile forces
Essential for bone strength; brittle if organic matrix removed; flexible if inorganic matrix lacking

Functions of the Three Main Cell Types in Bone Tissue

1. Osteoblasts

Function: Bone formation
Synthesize and secrete organic components of bone matrix (osteoid) and mineralize
Location: Inner periosteum and endosteum

2. Osteocytes

Function: Maintain bone matrix, regulate mineral content, and communicate with other bone cells
Respond to mechanical stress
Location: Small cavities called lacunae, surrounded by bone matrix

3. Osteoclasts

Function: Bone resorption
Break down bone tissue by secreting hydrogen ions and enzymes
Crucial for bone remodeling and calcium homeostasis
Location: Depressions called Howship's lacunae; originate from mononuclear precursors in the bone marrow

Microscopic Structure of Compact Bone and Osteons

Compact Bone: Organized into structural units (osteons) which are cylindrical and run parallel to the long axis of the bone
Osteon: Each consists of concentric layers (lamellae) surrounding a central canal (Haversian canal), which contains blood vessels and nerves
Collagen fibers within adjacent lamellae have alternating orientations, resisting torsional forces

Components of the Osteon

Central Canal: Contains blood vessels and nerves
Lamellae: Layers of bone matrix, concentrically arranged, enhancing strength
Lacunae: Small cavities in lamellae housing osteocytes
Canaliculi: Tiny channels connecting lacunae, facilitating nutrient and waste exchange between osteocytes and blood vessels

Spongy Bone

Composed of a network of interconnecting trabeculae (branches of bone)
Porous structure, lighter than compact bone
Trabeculae support and house marrow but do not contain osteons
Similar lamellae organization, but parallel or irregular
Osteocytes reside in lacunae within the trabeculae, connected by canaliculi to receive nutrients from the surrounding bone marrow

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Description

Explore the intricate composition of bone tissue, focusing on the inorganic and organic matrices that contribute to its strength and flexibility. Learn about the vital roles played by osteoblasts, osteocytes, and other cells in maintaining bone health and integrity.