Bones and Cartilage

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The human skeleton which serves as the framework of the body consists of _____ named bones

cartilage and bone

The terms _____ and _____ can refer to either to a tissue or an organ

Cartilage and bone tissues

Are special type of dense regular connective tissue, they have relatively few cells and abundant intercellular substance

Chondrocytes and osteocytes; lacunae

Cartilage and bone differ from dense regular connective tissue because their cells, called ___________ and ______________ that are inside the cavities called ___________

Hyaline cartilage

Is the abundant type of cartilage in the body. It is glistening, smooth, and pearly white in fresh specimens

Hyaline cartilage

Forms the bulk of the skeleton of the fetus in utero. It is strong enough that it serves as a supporting network for the body of the fetus, it has the capability to grow rapidly in conditions of relatively low oxygen tension

Hyaline cartilage

Exist only in limited areas in and around the joints, the sternal ends of ribs, some parts of the respiratory system and external ear, and tendons and ligaments that are pressed on by bone

Chondrocyte (cartilage cell)

In vivo, it fills the lacunae where it resides. In routine histologic preparations, the cytoplasm of the cell usually shrinks a little. They vary in size and shape, when they are young, they are elliptical in shape with their long axes parallel to the cartilage surface. As they mature, they become larger and rounded

Fat droplets and glycogen granules

The cytoplasm is finely granular and basophilic. It also contains inclusion such as _____ and _____

Isogenous cells

When young chondrocytes mitose, the daughter cells, called _____________, tend to stay close to each other. Sometimes, under LM, the isogenous cells may appear to occupy the same lacuna. They are separated from each other by a thin layer of intercellular substance

Chondronectin

The ground substance also contains some non-collagenic proteins and glycoproteins, notably _____ (fibronectin-like substance that promotes adherence of collagen fibers to the cell surface of the chondrocyte)

Territorial matrix

Early histologists refer the intercellular substance which has 50 µm in thickness, as capsule of the chondrocytes but now referred to as?

Interterritorial matrix

The area in between the territorial matrices is called?

Pericellular capsule

The innermost layer of the territorial matrix resembles a basal lamina and sometimes called?

Type II collagen fibers

The extracellular fibers in hyaline cartilage are?

Type II collagen fibers

They account for 40% of the dry weight of the tissue. In H&E preparations, the collagen fibers in hyaline cartilage are not distinguishable because they have the same refractive index as the ground substance

Elastic cartilage

is more flexible than hyaline cartilage and is yellowish in fresh specimens. It is present in the auricle and external acoustic meatus of the ear, auditory tube, epiglottis, and some other parts of the larynx

Collagen type II

Elastic cartilage is morphologically similar to hyaline cartilage except that the former’s matrix is less abundant. It is made up of?

Fibrous cartilage

can withstand greater stress than those mentioned earlier, and it is white in fresh specimens. It is the cartilage type that makes up the intervertebral discs, articular discs, and glenoid and acetabular labra. It can also be found in surface layers of tendons and ligaments that are pressed on by bone

Type I

The collagen fibers in fibrous cartilage are thicker because their collagen content is?

Articular cartilages

All cartilages are enveloped by dense irregular connective tissue, except for?

Perichondrium

Consist of an outer layer (fibrous layer) that blends with the surrounding tissue, and an inner, more cellular layer (chondrogenic layer) that adheres to the cartilage

Bone

Serves as the rigid framework of the body

Bone

Protects the vital organs (e.g., the cranium that protects the brain while the bony thorax which protects the heart, lungs, and other mediastinal structures)

Long Bones – Confined to the extremities. A typical long bone is tubular and consists of a body and a shaft and two ends (proximal and distal epiphyses). The shaft has a hollow core (medullary cavity) while the epiphyses articulate with the other bones and are covered on their articulating surfaces by hyaline cartilage

Short Bones

cuboidal and are confined to the wrist and ankle

Flat Bones

typified by the sternum, scapulae, and many bones of the skull

Irregular Bones

vertebrae, hip bones, bones of the skull

Sesamoid Bones

those that develop in tendons that rub bony surfaces. Patella or knee cap is a typical example for this and most sesamoid bones are in the form of unnamed small nodules

Compact (cortical, dense) and spongy (cancellous)

The two forms of bone tissue are?

20-25; 75-80

In mass, spongy bone accounts for _____% of body’s total skeletal mass while compact bone accounts for _____%

Periosteum

Consists of an outer layer (fibrous layer) that blends with the surrounding tissue, and an inner, more cellular layer (osteogenic layer) that adheres to the bone

Osteoprogenitor cell

The cells of the osteogenic layer of the periosteum that abut the surface of the bone are called?

Sharpey’s fibers

Sometimes, bundles of collagen fibers from the periosteum get trapped within the bone matrix and from distinct structural entities called?

Sharpey’s fibers

Serve to firmly anchor the periosteum to the bone

Endosteum

Lines all the medullary, marrow, and vascular cavities of bones. It is considerably thinner periosteum and often consists simple of a single layer of osteoprogenitor cells

Spongy bone

Consists of numerous small interconnecting bone fragments (spicules; trabeculae) that form the framework of a very complex system of spaces (bone marrow cavities). Each bone spicule is composed of several parallel bone lamellae and their bone marrow cavities occupied by bone marrow

Harversian systems; interstitial lamellae; or circumferential lamellae

In compact bones, instead of forming spicules, the lamellae are organized and arranged in any of the three ways:

Harversian systems

Make up the bulk of compact bones. It consists of several bone lamellae together with their associated lacunae and osteocytes that are arranged concentrically around a tiny, endosteumlined, longitudinal channel (Haversian canal; canal of Havers) that contains blood vessels and nerves

Osteons

Harversian systems are also called?

Volkmann’s canals

The haversian canal of neighboring Haversian systems are connected to each other by transverse channel called?

Interstitial lamellae

In between Haversian systems, the _____ are not arranged around a haversian canal

Circumferential lamellae

In between Haversian systems, the _____ are most developed in long bones

Outer circumferential lamellae

In between Haversian systems, the _____ are some lamellae that encircle the whole bone

Inner circumferential lamellae

In between Haversian systems, the inner aspect of the compact bone is marked off by lamellae that encircle the whole medullary cavity which is referred to as?

Calcium and phosphorus

The inorganic chemicals in the intercellular substance of a bone consists mainly of?

Calcium hydroxyapatite

The inorganic chemicals in the intercellular substance of a bone consists mainly of calcium and phosphorus. These form crystal very similar to those of _____, that are seen lying at regular intervals alongside the collagen fibers under electron micrographs

Osteoprogenitor Cells

These are stem cells with limited potential they can multiply infinitely but they can differentiate only in either osteoblasts or chondroblasts. In bone, they form the layer of cells of the periosteum and the endosteum. In the cartilage, they comprise the layers of cells of the perichondrium that directly adjoins the cartilage

Osteoblast

They are responsible for the synthesis of the precursors of collagen fibers as well as the organic constituents of bone matrix. They are the easiest to find in histologic preparations because they are found on the surface of the developing bones and in tissues where new bone is being formed

Osteoblast

It promotes bone growth and also aids in bone resorption

Osteocyte

these cells occupy the lacunae in the bone tissue. A layer of osteoid tissue (i.e., uncalcified bone matrix) usually separates the osteocyte within a lacuna from the calcified matrix

Osteocytes

Do not divide but they retain enough secretory capability to maintain the bone matrix that surrounds them. In the process of bone resorption, some osteocytes are set free from their imprisonment in the lacunae

Osteoclast

they are large, multinucleated cells seen on surfaces of bones where resorption is taking place. Usually, they are found in concavities (Howship’s lacunae) that represent areas of resorbed bones

Osteoclast

Are the cells primarily responsible for bone resorption