Ch. 6 - Cartilage & Bone

*What are the Functions of Bone?

Support and protection of more delicate organs Movement—attachment site for muscles Hemopoiesis—blood cell production occurs in red bone marrow Storage of mineral and energy reserves

Which statements correctly describe the effects of aging on the skeletal system?

Tensile strength of bone decreases Production of the organic portion of bone matrix decreases

Which statements characterize concentric lamellae of osteons?

Their numbers vary among osteons. They are rings of bone tissue. They contain collagen fibers.

Which statements characterize central canals of osteons?

They are cylindrical channels. They contain nerves. They contain blood vessels.

Which statement(s) characterize osteoclasts?

They are phagocytic. They have ruffled borders. They reabsorb bone matrix. They secrete hydrochloric acid.

Types of fractures

Types named from the cause: stress, trauma, or pathology •Stress fracture: thin break due to increased activity, repetitive loads •Traumatic fracture due to excess stress to bone •Pathologic fracture: occurs in bone weakened by disease Types named after amount of soft tissue damage: simple, compound •Simple fracture: broken bone does not penetrate the skin •Compound fracture: broken bone penetrates the skin

*Which vitamin is required for the normal synthesis of collagen?

Vitamin C

The organic components of bone provide ______.

a resistance to stretching

A(n) _____ is a deep pit or socket in the maxillae or mandible.

alveolus

A thin layer of hyaline cartilage covering an epiphysis of a long bone is called ______.

articular cartilage

In bone, smooth muscle tissue is found in ______.

blood vessels of bone

Vitamin D stimulates

calcium absorption from GI tract into blood so that calcium is available for bone formation

Tiny channels that connect lacunae to other lacunae in an osteon are called ______.

canaliculi

*Patients with osteoporosis often suffer _________ fractures of the vertebral bodies due to loss of bone mass.

compression

Rings of bone connective tissue that surround the central canal of an osteon are called ______.

concentric lamellae

The ______ provides the major weight support of a long bone.

diaphysis

The elongated cylindrical shaft of a long bone is called its ______.

diaphysis

An incomplete layer of cells that lines the medullary cavity of a bone is called ______.

endosteum

*The medullary cavity of a long bone is lined with a thin layer of connective tissue called the

endosteum •Covers most internal surfaces (medullary cavity) of bones •Contains osteoprogenitor cells, osteoblasts, and osteoclasts •Active in bone remodeling, growth, fracture repair

The structure that replaces the epiphyseal plate in adult bone is the ______.

epiphyseal line

The secondary ossification centers form in the ______ of long bones.

epiphyses

The expanded end of a long bone is called the ______.

epiphysis

Passageways or slit-like openings through bones are called _____.

foramina canals fissures

the ___________ substance is the semisolid material that suspends and supports the collagen fibers; it is part of the organic materials in the matrix of bone.

ground

*Endochondral ossification begins with a(n) _________ model.

hyaline cartilage model •Produces most of the rest of the bones in the body, such as the upper and lower limb bones

Calcium phosphate and calcium hydroxide interact to form ______ in the matrix of bone.

hydroxyapatite crystals

When osteoblast activity out paces osteoclast activity, bone mass ______.

increases

Bones of the skeleton function as _____________ that are pulled when skeletal muscles contract.

levers or bars

The metaphysis of mature bone contains a thin layer of compact bone called the epiphyseal

line

Osteoprogenitor cells

mesenchymal stem cells in endosteum and periosteum; can produce more stem cells or osteoblasts

*Where does hemopoiesis occur?

occurs in red bone marrow

Which components of bone matrix provides its tensile strength?

organic compounds

Vitamin A activates

osteoblasts

Osteoblasts function to ______.

produce osteoid

Osteocytes

reside in lacunae; maintain matrix and detect mechanical stress on a bone

*Which structure does not contain cartilage?

stomach

A(n) _____ is a narrow groove on a bone.

sulcus

The basic unit of compact bone is

the tubular units called osteon •Also known as a Haversian system •Cylindrical structures •Run parallel to the diaphysis

A smooth, grooved, pulley-like articular process of a bone is called a(n) _____.

trochlea

*What is stored in bones?

•Calcium and phosphate •Lipids stored in yellow bone marrow

Periosteum

•Covers external surfaces of bones (except where articular cartilage does) •Dense irregular connective tissue •Attached by perforating fibers embedded in the bone matrix •Acts as anchor for blood vessels and nerves •Contains osteoprogenitor cells and osteoblasts •Active in remodeling, growth, fracture repair

Medullary cavity

•Hollow, cylindrical space in diaphysis •In adults, it contains yellow bone marrow

During aging, bone changes in two ways:

•Loses ability to produce organic matrix (mainly collagen) •Loses calcium and other minerals •Osteopenia: insufficient ossification -Can result in a decrease in bone mass called osteoporosis

A typical long bone has four major sets of blood vessels:

•Nutrient artery/vein: supply the diaphysis of a long bone; usually just one nutrient artery and vein per bone •Metaphyseal arteries/veins: supply the diaphyseal side of the epiphyseal plate •Epiphyseal arteries/veins: supply the epiphyses •Periosteal arteries/veins: supply blood to the external circumferential lamellae and superficial osteons

*Spongy bone

•Open lattice of narrow plates called trabeculae •Internal surface of bones •Within flat bones, spongy bone is called diploe Microscopic Anatomy -No osteons -Trabeculae contain parallel lamellae -Network of trabeculae provides resistance to stresses applied in many directions -Its spaces hold red bone marrow. -It is located deep to compact bone. -It forms diploe in the cranial bones. -It is located in the epiphyses of long bones.

*Compact bone

•Solid and relatively dense •External surfaces of long and flat bones

Articular cartilage

•Thin layer of hyaline cartilage covering the epiphysis •Reduces friction and absorbs shock in moveable joints

Appositional Growth

(growth pattern of cartilage along the cartilage periphery) Three major steps: •Mitosis of stem cells deep to perichondrium •Stem cells become chondroblasts at periphery •Chondroblasts produce matrix, become chondrocytes in lacunae Results: •Larger piece of cartilage •Newest cartilage on outside edges

Interstitial growth

(growth pattern of cartilage from within the cartilage) Four major steps: •Mitosis of chondrocytes in lacunae •Forms two chondroblasts per lacuna •Each synthesizes and secretes new matrix; this separates the cells which are then called chondrocytes •Cartilage continues to grow as new matrix is produced from within Results: •Larger piece of cartilage •Newest cartilage on the inside

*How does each hormone affect the skeletal system? -Growth hormone -insulin-like growth factor (IGF) -Thyroid hormone -calcitonin -parathyroid hormone -estrogen -testosterone -glucocorticoid

-Hormones regulate osteoblast and osteoclast activity and regulate calcium levels -Growth hormone and insulin-like growth factor (IGF) stimulate cartilage growth at epiphyseal plate -Thyroid hormone stimulates metabolic rate of osteoblasts, thereby stimulating bone growth -Calcitonin and parathyroid hormone have opposite effects on calcium •Calcitonin promotes calcium deposit from blood to bone and inhibits osteoclast activity •Parathyroid hormone stimulates osteoclasts to resorb bone and increase levels of calcium in the blood -Sex hormones (estrogen and testosterone), secreted in large amounts at puberty, greatly accelerate bone growth -Abnormally high glucocorticoid levels lead to loss of bone mass

What are the effects of exercise on bones?

-Mechanical stress stimulates increase in bone density by increased osteoblast activity -Bones of athletes become thicker and stronger as the result of repetitive and stressful exercise -Bones lose mass with age, but this can be slowed or reversed with weight-bearing exercise

Which statements characterize canaliculi?

-Nutrients pass through them -they extend from lacunae to lacunae -they contain osteocyte cytoplasmic extensions

*Bone remodeling

-Occurs at different rates at different places in body -It occurs throughout life. -It assists in the maintenance of calcium and phosphate levels in the body. -It occurs at both the endosteal and periosteal surfaces of the bone. -It can occur in response to stress on a bone.

*The zones found in an epiphyseal plate are (in correct order beginning with the edge closest to the epiphysis):

-Zone of resting cartilage: farthest from medullary cavity and nearest epiphysis; small chondrocytes in hyaline cartilage -Zone of proliferating cartilage: larger chondrocytes undergoing rapid mitotic cell division; aligned like stacks of coins -Zone of hypertrophic cartilage: chondrocytes cease dividing and become enlarged -Zone of calcified cartilage: deposited minerals kill the chondrocytes and make matrix opaque -Zone of ossification: walls between lacunae break down, forming channels that become invaded with capillaries and osteoprogenitor cells

Elastic cartilage

-named because it contains numerous elastic fibers in its matrix that are extremely resilient and flexible. -found in the epiglottis and in the external ear.

*The process of bone repair includes these steps:

1. A fracture hematoma forms 2. A fibrocartilaginous (soft) callus forms 3. A bony (hard) callus forms 4. The bone is remodeled

Intramembranous Ossification

1. Ossification centers form within thickened regions of mesenchyme 2. Osteoid undergoes calcification 3. Woven bone and surrounding periosteum form 4. Lamellar bone replaces woven bone, as compact bone and spongy bone form

*Which are the functions of cartilage?

1. Supporting tissues. For example, C-shaped hyaline cartilage rings in the trachea support the connective tissue and musculature of the tracheal wall; fibrocartilage provides both toughness and flexibility to the pubic symphysis and intervertebral discs; and flexible elastic cartilage supports the fleshy, external part of the ear called the auricle = ear. 2. Providing a gliding surface at articulations (joints), where two bones meet. 3. Providing a model for the formation of most of the bones in the body. Beginning in the embryonic period, cartilage serves as a "rough draft" form that is later replaced by bone tissue.

Endochondral Ossification

1. The fetal hyaline cartilage model develops 2. Cartilage calcifies, and a periosteal bone collar forms 3. The primary ossification center forms in the diaphysis 4. Secondary ossification centers form in the epiphyses 5. Bone replaces cartilage, except the articular cartilage and epiphyseal plates 6. Epiphyseal plates ossify and form epiphyseal lines

*In compact bone, ___________ connect adjacent lacunae, thereby providing pathways for nutrients and other materials to pass between osteocytes.

Canaliculi

*Appositional growth vs. Interstitial

Appositional - grow in thickness Interstitial - grow in length

*Which is characteristic of cartilage connective tissue?

Cartilage is a semirigid connective tissue that is weaker than bone, but more flexible and resilient. As with all connective tissue types, cartilage contains a population of cells scattered throughout a matrix of protein fibers embedded within a gel-like ground substance. Once they become encased within the matrix they have produced and secreted, the cells are called chondrocytes and occupy small spaces named lacunae. Mature cartilage is avascular

Components of an osteon:

Central canal •Carries vessels and nerves in center of osteon Concentric lamellae •Rings of bone around central canal Osteocytes •Housed in lacunae between lamellae Canaliculi •Tiny, interconnecting channels that extend between lacunae •Allow osteocytes to connect and provide pathways for nutrients and other materials Perforating canals •Run perpendicular to and help connect multiple central canals •Passageways for blood vessels and nerves Circumferential lamellae •Rings of bone immediately internal to the periosteum (external circumferential lamellae) or internal to the endosteum (internal circumferential lamellae) •Run the entire circumference of the bone Interstitial lamellae •Leftover parts of osteons that have been partially resorbed

*During appositional growth of cartilage, the cells that produce the matrix are the

Chondroblasts

*A large, smooth, rounded articulating oval structure is called what?

Condyle

*The shaft of a long bone is called the __________, while the expanded, knobby region at each end is called the __________.

Diaphysis; Epiphysis

Bone markings (surface features)

Each bone in the body has characteristic external and internal features Articulating surfaces -Condyle: Large, smooth, rounded oval structure -Facet: Small, flat, shallow surface -Head: Prominent, rounded epiphysis -Trochlea: Smooth, grooved, pulley-like process Depressions Alveolus (pl., alveoli): Deep pit or socket in the maxillae or mandible -Fossa (pl., fossae): Flattened or shallow depression -Sulcus: Narrow groove Projections for tendon and ligament attachment -Crest: Narrow, prominent, ridge-like projection -Epicondyle: Projection adjacent to a condyle -Line: Low ridge -Process: Any marked bony prominence -Ramus (pl., rami): Angular extension of a bone relative to the rest of the structure -Spine: Pointed, slender process -Trochanter: Massive, rough projection found only on the femur -Tubercle: Small, round projection -Tuberosity: Large, rough projection Openings and spaces -Canal: Passageway through a bone -Fissure: Narrow, slit-like opening through a bone -Foramen (pl., foramina): Rounded passageway through a bone -Meatus: Passageway through a bone -Sinus: Cavity or hollow space in a bone

*Which type of cartilage is found in the intervertebral discs?

Fibrocartilage -has numerous coarse, thick interwoven collagen fibers contribute to the extreme durability of this type of cartilage. It has no perichondrium -found in the intervertebral discs, the pubic symphysis, and the menisci (of the knee joint. In these locations, fibrocartilage acts as a shock absorber and resists compression. extracellular matrix

*Which is the most abundant type of cartilage in the body?

Hyaline cartilage is the most common type of cartilage and also the weakest. It provides its support through flexibility and resilience. Hyaline cartilage is found in many other areas of the body, including the nose, trachea (part of lungs), most of the larynx, costal cartilage, and the articular ends of long bones.

*What, if removed from bone, would cause a bone to lose its compressional strength?

Inorganic components of matrix: •Primarily hydroxyapatite •Calcium phosphate and calcium hydroxide •Ca10 (PO4)6 (OH)

Which statements describe an osteon?

It contains a central canal. It is also called a Haversian system. It is microscopic. It runs parallel to the diaphysis of a long bone.

Which statements describe the inorganic components of the matrix of bone?

It contains hydroxyapatite crystals. It gives the bone its hardness.

Which statements characterize endosteum?

It contains osteoblasts. It lines medullary cavities. It is active during bone repair.

Which statements characterize the microscopic arrangement of spongy bone?

It contains parallel lamellae. It contains no osteons. It contains lacunae and canaliculi.

Which statements correctly describe compact bone?

It forms the external walls of a long bone. It is solid and relatively dense

*Tell whether each bone is a long, short, irregular, or flat bone.

Long bones •Greater length than width •E.g., upper and lower limb bones (femur) Short bones •Nearly equal length and width •E.g., carpals (wrist) and tarsals (ankle) Flat bones •Thin, flat surfaces •E.g., roof of skull, sternum, scapula Irregular bones •Complex shapes •E.g., vertebrae

*Which region of a growing bone contains the epiphyseal plate?

Metaphysis •Region between diaphysis and epiphysis •Contains epiphyseal plate the region of bone growth

*Cells that produce new bone tissue by secreting matrix are called

Osteoblasts: produce new bone by forming bone matrix (secrete as organic osteoid)

*Bone cells called __________ break down bone by secreting hydrochloric acid and enzymes that dissolve the matrix.

Osteoclasts: large, multinuclear cells that break down bone (bone resorption), releasing calcium •Have ruffled border •Often located in a resorption lacuna •Secrete hydrochloric acid and enzymes that dissolve matrix •Release of stored calcium and phosphate from bone is called osteolysis

In a severe protein-deficient diet, which portion of the bone matrix will be reduced?

Osteoid The organic component

*Rami, trochanters, tubercles, and tuberosities are bone markings that serve as

Projections for tendon and ligament attachment