- Occurs in perichondrium - Chondrogenic cells ➡ Chondroblasts ➡ Chondrocytes - These new cells elaborate a new layer of cartilage matrix at the periphery.

- Manufacture the cartilage matrix through which nutrients and waste materials pass to and from the cells - Differentiate into chondrocytes

- Mature cartilage cells that are embedded within lacunae in the matrix - Arise from chondroblasts in the perichondrium

cartilage and bone module Flashcards by Jessica Buddenbaum

fibrocartilage

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characteristics of hyaline cartilage

Type II collagen, chondrocytes usually arranged in groups
perichondrium present except articular surfaces
articular ends of long bones, nose, larynx, trachea, bronchi, ventral ends of ribs, template for endochondral bone formation

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elastic cartilage characteristics

possesses a perichondrium and is nearly identical to hyaline cartilage except for a network of elastic fibers, which impart a yellowish color. Although it contains type II collagen, it is less prone to degeneration than hyaline cartilage and is located in areas where flexible support is required.

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Fibrocartilage characteristics

lacks an identifiable perichondrium. It is characterized by alternating rows of fibroblast-derived chondrocytes surrounded by a scant matrix and thick parallel bundles of type I collagen fibers. Fibrocartilage is located in areas where support and tensile strength are required.

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types of hitiogenesis

interstitial growth

appositional growth

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interstitial growth

[Existing chondrocytes] ➡ [More chondrocytes]

Occurs (1) during the early stages of cartilage formation, (2) in articular cartilage, and (3) in epiphyseal plates of long bones

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Appositional growth

Occurs in perichondrium
Chondrogenic cells ➡ Chondroblasts ➡ Chondrocytes
These new cells elaborate a new layer of cartilage matrix at the periphery.

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osteoclasts arrise from

hematopoetic stem cell- monocyte lineage

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Functions primarily to support soft tissues and assist in the development and growth of long bones.

cartilage

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Has a firm extracellular matrix that is less pliable than that of connective tissue proper

cartilage

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Avascular specialized fibrous connective tissue

cartilage

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matrix of cartilage

Composed of an amorphous ground substance containing proteoglycan aggregates and chondronectin, in which type II collagen is embedded.

has territorial and interterritorial matrix

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collagen matrix

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territorial matrix

Adjacent to chondrocytes

Poor in collagen

Rich in proteoglycans

Stains more deeply

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Region away from chondrocytes

Rich in collagen

interterritorial matrix

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chondroblasts

Manufacture the cartilage matrix through which nutrients and waste materials pass to and from the cells
Differentiate into chondrocytes

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chondrocytes

Mature cartilage cells that are embedded within lacunae in the matrix
Arise from chondroblasts in the perichondrium

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Chondrocytes arise by differentiation of ____ chondrogenic cells and from chondrogenic cells within the inner layer of the perichondrium into _____, which are the earliest cells to produce cartilage matrix.

mesenchymal

chondroblasts

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perichondrium

-A layer of dense, irregular connective tissue that surrounds…

Hyaline cartilage (except at articular surfaces)

Elastic cartilage

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provides the nearest blood supply to the avascular cartilaginous tissue

perichondrium

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degeneration of chondrocytes

Occurs when chondrocytes undergo hypertrophy and die and the matrix becomes calcified, a process that becomes more frequent with age

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Degeneration of hyaline cartilage is a normal part of ______ bone formation.

endochondral

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most abundant cartilage in the body

hyaline

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serves as a temporary skeleton in the fetus until it is replaced by bone

hyaline cartilage

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A specialized type of connective tissue with a calcified extracellular matrix in which osteocytes, osteoblasts, and osteoclasts are embedded

bone

functions of bone

Protect vital organs Support fleshy structures Provide a calcium reserve

Inorganic (calcified) matrix

~65% of the dry weight Composed of calcium, phosphate, bicarbonate, citrate, magnesium, potassium, & sodium

Consists primarily of hydroxyapatite crystals: Ca10(PO4)6(OH)2

inorganic calcified matrix

~35% of the dry weight of bone

organic matrix

type of collagen fibers in organic matrix

type 1

organic matrix has a ground substance that contains ___ and \_\_\_

chondroitin sulfate & keratan sulfate

Located in the periosteum and the endosteum Differentiate into osteoblasts

osteoprogenitor cells

Spindle-shaped cells derived from embryonic mesenchyme

osteoprogenitor cells

osteoblast appearance

Cuboidal when active, flat when inactive (a.k.a., “bone-lining cells”)

osteoblasts

- Responsible for synthesis of organic matrix (e.g., type I collagen, proteoglycans, and glycoproteins) which they secrete as osteoid (uncalcified bone matrix) - Possess receptors for parathyroid hormone (PTH) - Become entrapped in lacunae (small spaces) but maintain contact with other cells via their cytoplasmic processes

entrapped osteoblasts are \_\_\_

osteocytes

Mature bone cells housed in their own lacunae (small spaces)

osteocytes

how do osteocytes communicate

gap junctions

Nourished and maintained by nutrients, metabolites, and signal molecules carried by the extracellular fluid that flows through the lacunae and canaliculi.

osteocytes

calcium released from bone enters the extracellular fluid located within these spaces.

lacuna and canaliculi

osteolysis

osteoclasts

Osteoclasts (O) form and reside in depressions known as \_\_\_\_\_\_, which represent areas of bone resorption.

Howship’s lacunae

Osteoclasts possess cell surface receptors:

colony-stimulating factor-1 receptor, calcitonin receptor, RANK (nuclear factor kappa B).

osteoblasts that have been stimulated by PTH promote

PTH casues osteoblasts to decrease bone formation which releases osteoclast stimulating factor, this leads to increased bone resoprtion, liberation of calcium, in osteoclast formation

osteopontin

secreted by osteoblasts, is used to seal the zone between osteoclasts and the subosteoclastic compartment.

osteoclast zones

basal zone ruffled border clear zone vesicular zone

Contains exocytotic vesicles that transfer lysosomal enzymes to Howship’slacunae and endocytic vesicles that transfer degraded bone products from Howship’s lacunae to the interior of the cell.

vesicular zone of osteoclasts

ruffled border of osteoclast

Site of active bone resorption Composed of irregular fingerlike cytoplasmic projections extending into the subosteoclastic compartment, a slight depression that deepens as the osteoclast resorbs bone, resulting in Howship’s lacuna

steps of bone resorption

1. Osteoclasts secrete acid, which decalcifies the surface layer of bone. 2. Acid hydrolases, collagenases, and other proteolytic enzymes secreted by osteoclasts then degrade the organic portion of the bone. 3. Osteoclasts resorb the organic and inorganic residues of the bone matrix and release them into connective tissue capillaries.

periosteum

A layer of noncalcified connective tissue covering bone on its external surfaces except at synovial articulations and muscle attachments

Composed of an outer dense fibrous collagenous layer and an inner cellular osteoprogenitor (osteogenic) layer.

periosteum

Sharpey fibers

(type I collagen) attach the periosteum to the bone surface

Functions to distribute blood vessels to bone

periosteum

A thin specialized connective tissue that lines the marrow cavities

endosteum

Supplies osteoprogenitor cells and osteoblasts for bone growth and repair

endosteum

spongy bone also called

cancellous or trabecular bone

Trabeculae contain ____ and are lined on both surfaces by a single layer of \_\_\_\_\_.

osteocytes osteoblasts

spongy bone is always surrounded by

compact bone

dense or cortical bone

compact bone

has no trabeculae or bone marrow cavities

primary bone

the first compact bone produced during fetal development and bone repair. It is remodeled and replaced by secondary bone.

contents of primary bone

Many osteocytes Large, irregularly-arranged type I collagen bundles Low mineral content.

places where primary bone remains without replacement

tooth sockets near suture lines in skull bones insertion sites of tendons

mature or lamellar bone

secondary bone

compact bone of adults

seconday bone

bone remodeling

the combination of bone formation and resorption

Intramembranous bone formation produces bone that is ______ to bone produced by endochondral bone formation.

histologically identical

centers of developing bone where osteoblasts become trapped in their own matrix

trabeculae (fused spicules)

Fusion of the bony trabeculae produces spongy bone as blood vessels invade the area and other undifferentiated mesenchymal cells give rise to the

bone marrow

The _____ and _____ develop from portions of the mesenchymal layer that do not undergo ossification.

periosteum endosteum

endochondral formation

Begins in a segment of hyaline cartilage that serves as a small model for the bone Two stages of endochondral bone formation:

Two stages of endochondral bone formation:

Primary center of ossification -Occurs at the midriff (middle of diaphysis, or shaft) Secondary center of ossification -Occurs at the ends of the bones

haversian systems are composed of 4 to 20 _____ surrounding a central Haversian canal, which contains blood vessels and nerves

lamellae (calciied concentric layers)