A&P Chapter 6 Quiz

Zone of resting cartilage

Attached to the epiphysis Contains chondrocytes that do not divide rapidly

Woven Bone

Collagen fibers randomly oriented in many different directions. Formed during fetal development or during the repair of a fracture. Remodeled (osteoclasts break down woven bone and osteoblasts build new matrix to for lamellar bone.)

Organic

Collagen provides flexible strength to the matrix. Proteoglycans

Endosteum

Delicate membrane covering internal surfaces of bone, including cancellous bone

Outer layer of perichondrium

Dense irregular connective tissue containing fibroblasts

Outer Fibrous Layer

Dense regular connective tissue, which contains blood vessels and nerves

Red Bone Marrow

Site of blood cell formation. Converted to yellow bone marrow just before birth. Process continues into adulthood. In mature bone, yellow marrow replaces red marrow in the limbs except for some red marrow in the proximal arm and thigh. Elsewhere, varying proportions of red and yellow marrow can be found. Ex. Ilium (hip bone)- 50% red, 50% yellow. This is where red bone marrow is taken for donations.

Epiphyseal Plate

Site of bone growth in length. Becomes the epiphyseal line when all cartilage is replaced with bone.

Growth Factors

Size and shape of bone determined genetically but can be modified and influenced by other factors: Nutrition and Hormones

Storage

Some minerals from the blood are stored within bone (calcium, phosphorus, fats)

Appositional Growth

The addition of new cartilage matrix on the surface of cartilage. Chondroblasts in the inner layer of the perichondrium lay down new matrix on the surface of the cartilage. Once chondroblasts are surrounded by matrix, they become chondrocytes in the new layer of cartilage

Diaphysis

Tubular shaft that forms the axis of long bones. Composed of compact bone that surrounds the medullary cavity. Contains yellow bone marrow. Certain bones also contain red bone marrow.

Growth in Width

1. Appositional bone growth beneath the periosteum increases the diameter of long bones and the size of outer bones. 2. Osteoblasts from the periosteum form ridges with grooves between them 3. The ridges grow together, converting the grooves into tunnels filled with concentric lamellae to form osteons 4. Osteoblasts from the periosteum lay down concentric lamellae, which can be remodeled

Ossification: Endochondral

1. Chondroblasts produce a cartilage model that is surrounded by pericondrium, except where joints will form 2. The perichondrium of the diaphysis becomes the periosteum, and bone collar is produced, internally the chondrocytes hypertrophy, and calcified cartilage forms 3. A primary ossification center forms as blood vessels and osteoblasts invade the calcified cartilage. The osteoblasts lay down bone matrix, forming spongy bone 4. The process of bone collar formation, cartilage calcification, and spongy bone production continues. Calcified cartilage begins to form in the epiphyses. A medullary cavity begins to form in the center of the diaphysis. 5. Secondary ossification centers from in the epiphyses of long bones 6. The original cartilage model is almost completely ossified. Unossified cartilage becomes the epiphyseal plate and the articular cartilage. 7. In a mature bone, the epiphyseal plate has become the epiphyseal line, and all the cartilage in the epiphysis, except the articular cartilage, has become bone

Bone length process

1. Chondrocyte replication and hypertrophy result in interstitial cartilage growth 2. Interstitial cartilage growth increases the length of the bone 3. Ossification of calcified cartilage produces additional bone on the diaphyseal side of the epiphyseal plate 4. The thickness of the epiphyseal plate remains unchanged because the addition of cartilage through interstitial cartilage growth occurs at the same rate as the addition of bone through ossification of calcified cartilage

Bone Repair

1. Hematoma formation: Torn blood vessels hemorrhage. A mass of clotted blood (hematoma) forms at he fracture site. Site becomes swollen, painful, and inflamed. 2. Callus Formation: Granulation tissue (soft callus) forms a few days after the fracture. Capillaries grow into the tissue and phagocytic cells begin cleaning debris. Internal callus forms between the ends of the bones. External callus forms a collar around the fracture. External callus: osteoblasts and fibroblasts migrate to the fracture and being reconstructing the bone. Fibroblasts secrete collagen fibers that connect broken bone to bone ends. Osteoblasts begin forming woven bone. Osteoblasts furthest from capillaries secrete an externally bulging cartilaginous matrix that later calcifies. 3. Callus ossification: The fibers and cartilage of the internal and external calluses are ossified to produce woven, cancellous bone. Cancellous bone formation in the callus is usually complete 4-6 weeks after the injury. 4. Bone Remodeling: Excess material on the bone shaft exterior and in the medullary canal is removed. Compact bone is laid down to reconstruct shaft walls. The remodeling process may take more than a year to complete.

Epiphyseal plate growth

1. Interstitial (within matrix) formation of new cartilage 2. Appositional (on surface) be one growth on the cartilage

Ossification: Intramembranous

1. Osteochondral progenitor cells specialize to become osteoblasts (8th week of development) 2. Osteoblasts lay down bone matrix on collagen fibers of the connective tissue membrane forming the small trabeculae of woven bone 3. Trabeculae enlarge as additional osteoblasts lay down cell matrix on their surface 4. Cancellous bone forms as the trabeculae join together 5. Red bone marrow develops in the spaces within the matrix and the surrounding cells specialize to form the periosteum 6. Beneath the periosteum, osteoblasts lay down bone matrix to form an outer surface of compact bone

Blood Calcium Homeostasis

1. Osteoclasts break bone down and release calcium into the blood. Osteoblasts remove calcium from the blood to make bone. PTH stimulates osteoclast activity. Calcitonin inhibits osteoclast activity. 2. In the kidneys, PTH increases calcium reabsorption from urine 3. In the kidneys, PTH promotes formation of active Vitamin D which increases calcium reabsorption from the small intestine.

Short Bones

About as wide as they are long Bones of the wrist (carpals) and ankle (tarsals)

Osteomalacia

Adult form of rickets

Bone Matrix

Approximatey 35% organic and 65% inorganic material by weight

Centers of ossification

Areas in the membrane where ossification begins. Gradually expands to form bone by ossifying the membrane

Fontanels

Areas of membrane between developing skull bones that have not been ossified at birth (soft spots). Closed by 2 years of age

Basic Multicellular Units (BMUs)

Assemblies of osteoclasts and osteoblasts that travel through or across the surface of bone removing old matrix and replacing it with new matrix. Osteoclasts break down bone matrix, making tunnels in the bone. Osteoblasts move in and lay down a lyre of bone on the tunnel wall, forming concentric lamellae. Interstitial lamellae are remnants of bone not removed by BMUs. BMU activity renews the entire skeleton every 10 years.

Hormones

Can increase bone growth as well as cause closure of the epiphyseal plates

Central Canal

Canal in the center on an osteon that contains blood vessels

Bone length

Bone length increases occurs and the epiphyseal. Epiphyseal plate growth results in an increase in length of the diaphysis and bony processes. Growth in length ceases when the epiphyseal plate becomes ossified and forms the epiphyseal line.

Calcium Homeostasis

Bone: Major storage site for calcium. Blood calcium levels depend on movement of calcium into and out of bone. Osteoblast Activity: Increases bone density. Increase calcium in bone. Osteoclast Activity: Decreases bone density. Decreases calcium in bone.

Components of the skeletal system

Bones Cartilage Tendons Ligaments

Bone Growth

Bones increase in size by appositional growth only (unlike cartilage). Addition of new bone on the surface of older bone or cartilage. Ex. trabeculae grow in size by the deposition of new bone matrix by osteoblasts on the trabecular surface.

Calcitonin stimulates:

Calcium salt deposition in bone by decreasing osteoclast activity

Ossified bone

Calcified cartilage of the diaphyseal side of the plate is replaced by bone

Circulation

Canals within contact bone provide a means for the exchange of gases, nutrients, and waste products

perforating canals

Carry blood vessels to central canals Run perpendicular to the long axis of the bone

Hyaline Cartilage

Chondroblasts Chondrocytes Cartilage matrix Perichondrium

Short and Irregular Bones

Composition similar to the ends of long bones. Compact bone surfaces that surround a cancellous center. Bone center has small spaces filled with marrow. Not elongated, have no diaphyses. Certain regions have epiphyseal growth plates.

Canaliculi

Connect central canal to osteons. Nutrients are transferred to the osteocytes through the canal system.

Trabeculae

Consists of several lamellae. Osteocytes located within lacunae between the lamellae. Each osteocyte is associated with other osteocytes through canaliculi. Osteocytes obtain nutrients through their canaliculi. Trabecular surface is covered with a single layer of cells: mostly osteoblasts with a few osteoclasts.

Cartilage matrix

Contains collagen fibers (for strength) and proteoglycans that trap water (for resilience)

Bone Remodeling

Converts woven bone to lamellar bone. Allows bone to change shape, adjust to stress, repair themselves, and regulate blood calcium levels.

Articular Cartilage

Covers the ends of long bones. Does NOT contain perichondrium, blood vessels, or nerves.

Osteocytes

Derived from osteoblasts. Mature bones cells that maintain in the bone matrix. Located in the lacunae. Osteocyte cell processes are connected to one another through canaliculi. Nutrients and gasses pass through fluid surrounding cells in the canaliculi or lacunae or pass from cell to cell via gap junctions connecting the cell processes.

Osteoclasts

Derived from red bone marrow and white blood cells (monocytes). Responsible for the resorption (breakdown) of bone. Large multi nucleated cells. Release H+ to produce an acidic environment: decalcified the bone matrix Release enzymes that digest the protein components of the matrix. Use endocytosis to take some of the products of resorption into the osteoclast

Irregular Bones

Do not fit into the other three categories. Vertebrae, pelvic girdle and facial bones

Periosteum

Double layer of protective membrane covering the outer surface of the bone.

Perichondrium

Double layered connective tissue sheath. Surrounds most cartilage The outer layer of the perichondrium contains blood vessels, but they do not enter the cartilage matrix.

Epiphyses

Expanded ends of long bones. Exterior is compact bone, and the interior is cancellous bone. Joint surfaces are covered with articular (hyaline) cartilage.

Cartilage

Firm, yet flexible support

Blood Cell Production

Hematopoiesis occurs within the marrow cavities of bones

Support

Form the framework that supports the body and cradles soft organs.

Circumferential Lamellae

Form the outer surface of compact bones

Endochondral ossification

Formation of bone with cartilage. Bones of the base of the skull, part of the mandible, the epiphyses of the clavicles, and most of the remaining skeletal system. Produce woven bone that is later remodeled

Intramembranous ossification

Formation of bone within a connective tissue membrane. Some skull bones, part of the mandible, and the diaphyses of the clavicles. Produce woven bone that is later remodeled

Protection

Hard structure provides a protective case for the organs, brain, and spinal cord

Types of Cartilage

Hyaline Fibrocartilage Elastic Most of the bones in the body develop from hyaline cartilage. Aids in bone growth and repair.

Inorganic (mineral)

Hydroxyapatite (calcium phosphate crystal) provides compression (weight-bearing) strength to the matrix

Nutriton

Inadequate intake of materials necessary to support chondroblasts and osteoblast activities results in decreased cartilage and bone growth. Lack of calcium, protein and other nutrients during growth and development can cause bones to be small.

Growth hormone

Increases bone growth by stimulating interstitial cartilage growth and appositional bone growth

Estrogen and testosterone

Initially stimulate bone growth (burst in growth at puberty when production increases). Also stimulate closure (ossification) of the epiphyseal plates. Females usually stop growing before males because estrogen causes a quicker closure of the epiphyseal plate than testosterone.

Rickets

Insufficient Vitamin D in children a disease resulting from reduced mineralization of the bone matrix. Can result in bowed bones and inflammation of joints

Articular Cartilage Growth

Interstitial cartilage growth followed by apposition bone growth. Results in larger epiphyses and an increase in the size of bones that do not have epiphyseal plates (short). Growth of articular cartilage ceases, when bones reach mature size. Articular cartilage lasts throughout life and does not become ossified.

Cancellous (spongy) bone

Less bone matrix and more space than compact bone. Interna layer is a honeycomb of trabeculae filled with red or yellow bone marrow

Chondrocytes

Located in lacunae within the matrix

Long Bones

Longer than they are wide. Most bones of the upper and lower limbs.

Bone

Major supporting tissue of the body

Zone of calcification

Matrix is calcified, and hypertrophied chondrocytes die

Aging

Matrix: more brittle due to lack of collagen and less hydroxyapatite. Bone Mass: Overall decrease starts around age 30. Slower in males. Can be slowed by adequate nutrition and weight-bearing activity. Cancellous bone loss: thinning and loss of trabeculae. Compact bone loss: less osteon formation. Loss of bone: increases the risk for fractures. Causes deformity. Loss of height. Pain. Stiffness. Loss of teeth.

Lamellar Bone

Mature bone. Arranged in thin sheets or layers call lamellae. Has collagen fibers oriented parallel to one another, but at an angle to collagen fibers in other lamella.

Origin of Bone Cells

Mesenchymal cells can develop into stem cells that give rise to more specialized cell types

Osteon

Modular unit of compact bone

Compact Bone

More bone matrix and less space than cancellous bone. External layer. Consists of organized lamellae.

Inner layer of perichondrium

More delicate (has fewer fibers) and contains chondroblasts

Vitamin D

Necessary for the normal absorption of calcium from the intestines. The body's inability to absorb fats in which Vitamin D is soluble can also result in deficiency.

Zone of proliferation

New cartilage is produced through interstitial cartilage growth. The chondrocytes divide and from columns of cells.

Classification of Bone Fractures

Open or closed fractures Incomplete or complete fractures Comminuted or impacted fractures Linear or transverse fractures

Mechanical stress applied to bone

Osteoblast activity is increased in bone tissues. Increases bone density.

Ossification

Osteoblasts rest on a pre-existing surface, such as cartilage or bone. The cell processes of different osteoblasts join together. Osteoblasts surround themselves with bone matrix. The osteoblasts are new osteocytes.

Inner Osteogenic Layer

Osteoblasts, osteoclasts, and osteochondral progenitor cells.

Mechanical stress is reduced

Osteoclast activity remains normal, while osteoblast activity is reduced. Bone density is decreased at an accelerated rate.

PTH stimulates:

Osteoclasts to degrade bone matrix and release calcium into the blood. Calcium absorption from the small intestines. Reabsorption of calcium from the urine.

Haversian System

Osteon Central canal Lacuna Concentric lamellae Canaliculi

Hormones that regulate calcium levels in the blood

Parathyroid hormone (PTH) and calcitonin

Cancellous Bone

Porous in appearance Consists of thin rods or plates of interconnecting bone called trabeculae. Trabeculae are oriented along lines of stress and provide structural strength. Covered with endosteum. Bone marrow and blood vessels fill spaces between trabeculae

Osteoblasts

Produce new bone matrix. Have an extensive ER, numerous ribosomes, and Golgi apparatus. Produce collagen and proteoglycans that are packaged into vesicles by the Golgi apparatus and released from the cell by exocytosis. Also produce matrix vesicles.

Movement

Provide levers for skeletal muscle

Flat Bones

Relatively thin, flattened shape and are usually curved. Certain bones of the skull, ribs, sternum, and scapulae. Contain an interior framework of cancellous bone sandwiched between two layers of compact bone.

Interstitial Lamellae

Remnants of lamellae left after bone remodeling

Thyroid hormone

Required in adequate amounts for growth of all tissues

Calcitonin

Rising blood calcium levels trigger the thyroid to release calcitonin.

Epiphyseal Line

Separates the diaphysis from the epiphysis

Lacuna

Space within an osteon where osteocytes are located

Chondroblasts

Specialized cells that produce cartilage matrix. When the matrix surrounds a chondroblast, it develops a chondrocyte

Spiral or Oblique fractures

Spiral: helical course around the bone Oblique: run obliquely to the direction of the long axis

Osteochondral progenitor cells (OPCs)

Stem cells that become osteoblasts or chondroblasts. Located in the inner layer of the perichondrium, inner layer of the periosteum, and the endosteum

Concentric Lamellae

Surround central canals, forming osteons

Interstitial Growth

The addition of new cartilage matrix within the cartilage. Chondrocytes within the tissue divide and add more matrix between the cells increasing the thickness of the cartilage

Zone of hypertrophy

The chondrocytes mature and enlarge

Incomplete or complete fractures

The completeness of the break Complete: bone broken into at least 2 fragments Incomplete: fracture does not extend completely across the bone

PTH

The major regulator of blood calcium (crucial for normal muscle and nervous tissue formation). Falling blood calcium levels signal the parathyroid glands to release PTH.

Comminuted or impacted fractures

The position of the bone ends after fracture Comminuted: bone breaks in more than tow places Impacted: one fragment is driven into the cancellous portion of the other fragment

Open or closed fractures

Whether or not the bone ends penetrate skin

Giantism

abnormally increased height that results from abnormal cartilage and bone formation at the epiphyseal plates of long bones

Linear or transverse fractures

the orientation of the bone to the long axis Transverse: Occurs at a right angle to the long axis