Bone Tissue Overview

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Questions and Answers

What is the primary study of bone structure called?

Physiology

Anatomy

Histology

Osteology (correct)

Which of the following is NOT a primary function of the skeletal system?

Protects internal organs

Assists in movement

Supports body

Produces hormones (correct)

What is the hollow part of the diaphysis called?

Periosteum

Endosteum

Medullary cavity (correct)

Cortex

What substance primarily confers hardness to bone tissue?

Mineral salts Signup and view all the answers

What is the term for the process by which mineral salts harden on collagen fibers?

Calcification Signup and view all the answers

What type of tissue does osseous tissue belong to?

Connective tissue Signup and view all the answers

Which of the following describes the epiphyses of long bones?

The knobby ends of bones Signup and view all the answers

Which cells in bone tissue are responsible for making and remodeling bone?

Osteoprogenitor cells Signup and view all the answers

What do osteoblasts secrete as components of bone ECM?

Collagen Signup and view all the answers

Which type of bone cell does not divide or secrete substances?

Osteocytes Signup and view all the answers

What process do osteoclasts utilize to release minerals into the blood?

Bone resorption Signup and view all the answers

What is the structural unit of compact bone?

Osteon Signup and view all the answers

Which lamellae are made of old concentric lamellae from existing osteons?

Interstitial lamellae Signup and view all the answers

What primarily surrounds trabeculae in spongy bone?

Red bone marrow Signup and view all the answers

What is the primary function of nutrient arteries in bone?

Supply oxygen and nutrients Signup and view all the answers

Which of the following best describes ossification?

Transformation of cartilage to bone Signup and view all the answers

What type of ossification develops from mesenchymal tissue directly?

Intramembranous ossification Signup and view all the answers

How does bone tissue adapt to mechanical stress?

Increases its density Signup and view all the answers

What role do nerves play in bone metabolism?

Influence osteoblast and osteoclast activity Signup and view all the answers

What is the significance of canaliculi in bone tissue?

Facilitate cell communication Signup and view all the answers

Where do nutrient arteries enter the bone?

Diaphysis Signup and view all the answers

What is the function of periosteal arteries?

Nourish the periosteum Signup and view all the answers

What type of cells do mesenchymal cells differentiate into first during endochondral ossification?

Chondroblasts Signup and view all the answers

What forms the bulk of the primary ossification center during endochondral ossification?

Hyaline cartilage Signup and view all the answers

Which zone of the epiphyseal plate does NOT undergo cell division?

Zone of resting cartilage Signup and view all the answers

What is the outcome when chondrocytes in the epiphyseal plate cease to divide?

Closure of the epiphyseal plate Signup and view all the answers

Which hormone is known to influence the activity of osteoblasts at the epiphyseal plate during childhood and adolescence?

Thyroid hormones Signup and view all the answers

Which zone of the epiphyseal plate contains layers of dead chondrocytes?

Zone of calcified cartilage Signup and view all the answers

What role do osteoclasts play in bone remodeling?

Catabolizing bone Signup and view all the answers

What is appositional growth related to?

Circumferential growth of bone Signup and view all the answers

Where does interstitial growth primarily occur in long bones?

Epiphyseal plate Signup and view all the answers

What begins the formation of the periosteum during intramembranous ossification?

Condensation of mesenchymal cells Signup and view all the answers

What happens to hyaline cartilage during endochondral ossification?

It becomes bone in the diaphysis Signup and view all the answers

What triggers the maturation of osteoprogenitor cells into osteoblasts?

Nutrient artery penetration Signup and view all the answers

What substance is secreted by osteoblasts to contribute to bone formation?

Collagen and ECM Signup and view all the answers

What marks the close of the epiphyseal plate?

Calcification of extracellular matrix Signup and view all the answers

What is the remodeling frequency of the distal portion of the femur?

Every 4 months Signup and view all the answers

What happens to bone when faced with a sedentary lifestyle?

It loses mass and density Signup and view all the answers

Which hormone is produced when calcium levels are low?

Parathyroid hormone Signup and view all the answers

What type of fracture is characterized by a break that can damage surrounding tissues?

Compound fracture Signup and view all the answers

What occurs during the reactive phase of bone repair?

Clot formation and inflammation Signup and view all the answers

What is a major consequence of misaligned broken bone ends during healing?

Increased risk of malunion or nonunion Signup and view all the answers

How does osteoporosis primarily affect elderly women?

It leads to higher levels of bone resorption. Signup and view all the answers

What is a treatment recommended for osteoporosis?

Increased calcium in the diet Signup and view all the answers

Which vitamin deficiency results in Rickets in children?

Vitamin D Signup and view all the answers

What is the primary role of calcium in the human body?

Nerve and muscle function Signup and view all the answers

Which type of bone tissue comprises the trabeculae?

Spongy bone tissue Signup and view all the answers

What is the first phase of bone repair called?

Reactive phase Signup and view all the answers

What is the tissue that forms a soft collagen bridge between fractured bone ends?

Fibrocartilaginous callus Signup and view all the answers

What is a known effect of weight-bearing exercise on bone?

Promotes bone remodeling Signup and view all the answers

Study Notes

Bone Tissue

Bone tissue is a connective tissue containing sparsely populated cells surrounded by a hard, mineralized extracellular matrix (ECM).
ECM is composed of 15% water, 30% collagen fibers, and 55% mineral salts.
Mineral salts deposit on collagen fibers, hardening the bone tissue.
Collagen fibers give tensile strength to bone tissue.
This process of mineralization is known as calcification.
Mineral salts in the ECM include hydroxyapatite, calcium phosphate, calcium hydroxide, and a smaller proportion of calcium carbonate.
Four types of bone cells:
- Osteoprogenitor cells are stem cells located deep to the periosteum.
- Osteoblasts secrete collagen and other ECM components; they do not divide.
- Osteocytes are mature bone cells that do not divide or secrete; they acquire nutrients and eliminate wastes.
- Osteoclasts catabolize bone; they are formed by the fusion of monocytes and secrete lysosomal enzymes and acids, releasing minerals into the blood. This process is called bone resorption

Two Types of Bone Tissue:

Spongy bone tissue : is not made of osteons.
- Structural unit: trabeculae (plates or projections of bone tissue arranged along lines of stress).
- Surrounded by red bone marrow and blood vessels.
- Lighter than compact bone tissue, fills bones to make them easier to move.
- Supports and protects bone marrow.
- Handles stress along multiple axes better than compact bone tissue.
Compact bone tissue : is the strongest bone tissue.
- Densely packed ECM, resistant to mechanical stress.
- Structural unit: osteon.
- Arrangement of osteons is not random; they occur along lines of stress.
- Osteonic canal: contains blood vessels and surrounds rings of ECM called concentric lamellae.
- Interstitial lamellae: made of old concentric lamellae from old osteons, found between existing osteons.
- Circumferential lamellae: surround long bone (along the circumference); joined to the periosteum via the perforating fibers.
- Osteocytes occupy spaces in the ECM called lacunae.
- Canaliculi: permit communication between osteocytes.
- Interosteonic canals: provide passage for blood vessels and nerves.
- Bone tissue heals relatively fast because of extensive vascularization.

Nerves and Blood Supply of Bone

Bone is well vascularized.
Periosteal arteries nourish the periosteum.
Nutrient arteries penetrate the diaphysis and branch into bone marrow.
Blood vessels enter the bone through the nutrient foramen.
Epiphyseal and metaphyseal arteries nourish the internal tissues of the epiphyses.
Nerves run similar paths to blood vessels through bones.
Functions of the blood supply of bone:
- Nutrient delivery: provides essential nutrients and oxygen to bone cells.
- Waste removal: removes metabolic waste products from bone tissue.
- Bone remodeling: delivers cells involved in bone formation and resorption.
- Hormone transport: transports hormones that regulate bone metabolism.
- Immune function: facilitates the movement of immune cells.
Functions of the nerve supply of bone:
- Pain perception: helps detect pain, signaling injury or disease.
- Regulation of bone metabolism: influences bone remodeling.
- Response to mechanical stimuli: senses mechanical stress on bones.
- Vascular regulation: influences blood flow to bone.
- Communication with other systems: coordinates with the nervous system and other body systems.

Ossification: Bone Formation:

The process of bone formation is called ossification.
Four major phases of life require bone formation:
- Development of the embryonic skeleton.
- Development during childhood and adolescence.
- During bone remodeling.
- During the repair of fractures.
The embryonic skeleton is initially composed of mesenchymal tissue.
Ossification proceeds in two general patterns:
- Intramembranous ossification: bone develops directly from mesenchymal tissue.
- Endochondral ossification: bone develops from a hyaline cartilage intermediate.

Intramembranous Ossification:

This is how the embryonic cranium and facial bones harden; it proceeds in four steps:
1. Formation of the ossification center: Mesenchymal cells differentiate into osteoprogenitor cells, which then differentiate into osteoblasts. Osteoblasts secrete the ECM of bone tissue.
2. Calcification of mineral salts secreted by osteoblasts.
3. Formation of trabeculae in spongy bone tissue: Connective tissue between trabeculae becomes red bone marrow.
4. Formation of the periosteum: Mesenchymal tissue surrounding forming trabeculae compacts and hardens into the periosteum.
Key points of intramembranous ossification:
- Bone forms directly from mesenchymal tissue.
- Makes both spongy and compact bone tissue.
- Starts in the embryo.
- Makes flat cranial and most facial bones.

Endochondral Ossification:

This process forms most bones, including long bones.
Six general steps:
1. Mesenchymal cells differentiate into chondroblasts: secrete collagen and form hyaline cartilage to form the future diaphysis.
2. Chondroblasts secrete ECM: interstitial growth (increase in bone length) and appositional growth (growth in bone circumference) by cells in the perichondrium.
3. Penetration of nutrient artery through the perichondrium: stimulates osteoprogenitor cells to mature into osteoblasts, making trabeculae in the growing diaphysis (primary ossification center). The perichondrium compacts and hardens into the periosteum; hyaline cartilage loses access to nutrients and disintegrates.
4. Primary ossification extends toward the ends of bones: Osteoclasts digest some of the spongy bone, carving out the medullary cavity.
5. Secondary ossification center forms at birth: Begins at birth.
6. Hyaline cartilage at joints becomes articular cartilage: Cartilage remaining at the metaphysis remains cartilage through adolescence and eventually ossifies.

Bone Growth During Childhood and Adolescence:

Bones can grow lengthwise or in circumference.
Interstitial Growth: Growth in length occurs at the epiphyseal plate of long bones.
- Zone of resting cartilage: anchors the epiphyseal plate to bone.
- Zone of proliferating cartilage: actively dividing chondrocytes contribute to interstitial growth.
- Zone of hypertrophic cartilage: contains mature chondrocytes arranged in columns.
- Zone of calcified cartilage: contains layers of dead chondrocytes; can be cleared by osteoclasts during bone remodeling.
At maturity, the epiphyseal plate "closes": chondrocytes cease to divide and the ECM calcifies. This occurs around 18 years in females and 21 years in males, leaving an epiphyseal line.
Appositional Growth: Growth in circumference or thickness occurs in four steps:
1. Periosteal cells become osteoblasts: ridges of ECM form around periosteal vessels.
2. Ridges fuse: former periosteum is now the endosteum.
3. Endosteal osteoblasts secrete ECM: new concentric lamellae are made.
4. New concentric lamellae are made by osteoblasts: increases the diameter of bone; osteoclasts in the endosteum catabolize bone, which allows the medullary cavity to grow.

Factors Affecting Bone Growth:

Nutrition: Proper intake of calcium and vitamin D is essential for healthy bone growth.
Hormones:
- Growth factors stimulate osteoblasts at the epiphyseal plate and periosteum during childhood and adolescence.
- Thyroid hormones (T3 and T4) stimulate osteoblasts.
- Estrogen inhibits or slows bone resorption by promoting apoptosis of osteoclasts.
- Testosterone can alter bone growth rates.
Exercise: weight-bearing exercise exerts mechanical stress on bone, leading to increased bone density. A sedentary lifestyle or injury leads to bone loss.

Bone Remodeling:

A dynamic, lifelong process involving the breakdown and rebuilding of bone tissue.
5% of bone is remodeled at any given time.
Resorption is the destruction of ECM by osteoclasts.
Deposition is the building of new ECM by osteoblasts.
Bone is remodeled during growth, during and after injury, and with changes in exercise and diet.
Osteoclasts suction to bone to be remodeled, secreting enzymes and acids that catabolize bone and release minerals into the blood via transcytosis.
Osteoblasts deposit bone along lines of mechanical stress. Bone remodeling is essential for calcium homeostasis.
Bone stores 99% of the body's calcium, which is important for nerve and muscle cell function, blood clotting, and enzyme catalysis.
Plasma calcium levels are carefully regulated to maintain the balance of mineral levels.

Fractures and Bone Repair:

Fractures are breaks in bones.
Stress fractures are microscopic and may not damage surrounding tissues.
Compound fractures are large and damage surrounding tissues.
Causes include trauma, repeated stressful or vigorous activities, and disease.
Fractures are treated by bringing the broken ends of bones back into alignment (reduction) to facilitate healing.
Closed reductions occur without surgical intervention.
Open reductions occur with surgical intervention, using screws, plates, or other methods.
Healing is facilitated by splints, casts, or other immobilization techniques.
Bone repair proceeds in three phases:
1. Reactive phase: a hematoma (a clot-like structure) stops bleeding from broken blood vessels; inflammation brings immune cells to the site of injury.
2. Reparative phase: formation of a fibrocartilaginous callus: a soft collagen bridge between the fractured ends of bone. Fibroblasts invade the break and secrete collagen; new blood vessels form and penetrate. Simultaneously, osteoprogenitor cells peripheral to the injury secrete ECM and lay down trabeculae of spongy bone tissue, forming a bony callus.
3. Bone remodeling phase: osteoclasts remove dead bone and compact bone replaces the spongy bone tissue around the fracture site, ultimately strengthening the healed area.

Bone Disorders

Osteoporosis: loss of bone density due to higher levels of bone resorption than bone building. Increases the risk of fracture. Disproportionately affects elderly women. Treatments and preventions include increased calcium in the diet, weight-bearing and resistance exercises, and medication.
Rickets and Osteomalacia: different manifestations of the same disease: vitamin D deficiency.
- Rickets is a childhood disease caused by low levels of vitamin D, resulting in inefficient calcium absorption. Bones soften and deform.
- Osteomalacia is the same condition in adults.

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Description

Explore the fundamental aspects of bone tissue in this quiz. Learn about its structure, composition, the process of calcification, and the various types of bone cells involved in its maintenance and health. Test your knowledge on the intricacies of this vital connective tissue.