Chapter 7: Bone Tissue

Bone Matrix

1/3 organic material: synthesis by osteoblast-made of collagen, Protein-carbohydrate complexes **2/3 inorganic material -mostly hydroxyapeptite( crystalized calcium phosphate) mixed with various minerals

Osteogenesis imperfecta

A defect in collagen deposition that renders bones exceptionally brittle, resulting in fractures present at birth or occurring with extraordinary frequency during childhood; also causing tooth deformity, and hearing loss due to deformity of middle-ear bones.

periosteum

A layer of fibrous connective tissue covering the surface of a bone.

osteocyte

A mature bone cell formed when an osteoblast becomes surrounded by its own matrix and entrapped in a lacuna.

Epiphyseal plate

A plate of hyaline cartilage between the epiphysis and diaphysis of a long bone in a child or adolescent, serving as a growth zone for bone elongation. -region of growth in children and adolescence -separates marrow cavities of of diaphysis and epiphysis

osteon

A structural unit of compact bone consisting of a central canal surrounded by concentric cylindrical lamellae of matrix.

Osteitis deformans

Excessive proliferation of osteoclasts and resorption of excess bone, with osteoblasts attempting to compensate by depositing extra bone. This results in rapid, disorderly bone remodeling and weak, deformed bones. Osteitis deformans usually passes unnoticed, but in some cases it causes pain, disfiguration, and fractures. It is most common in males over the age of 50.

solubility product

Hydroxyapatite crystals form only when the product of calcium and phosphate concentration in the tissue fluids, represented [Ca2+] ∙ [PO43-], reaches a critical value called the ( 3rd thing with bone deposition)

Step 2 eo

In a primary ossification center near the middle of this cartilage, chondrocytes begin to inflate and die, while the thin walls between them calcify. The perichondrium stops producing chondrocytes and begins producing osteoblasts. These deposit a thin collar of bone around the middle of the cartilage model, reinforcing it like a napkin ring. The former perichondrium is now considered to be a periosteum. As chondrocytes in the middle of the model die, their lacunae merge into a single cavity.

Osteomyelitis

Inflammation of osseous tissue and bone marrow as a result of bacterial infection. This disease was often fatal before the discovery of antibiotics and is still very difficult to treat.

interstitial growth

the multiplication of chondrocytes and deposition of new matrix in the interior, is called ( zones 2/3 push reverse cartilage toward end of bone)

nutrient foramina

tiny holes in the bones were blood vessels enter

epiphyseal plate

two transitional zones with hyaline cartilage in between

diploe

in the skull spongy bone is referred to as

interstitial lamella

irregular regions of bone matrix between osteons

mineral deposition

is a crystallization process in which calcium, phosphate, and other ions are taken from the blood plasma and deposited in bone tissue, mainly as needlelike crystals of hydroxyapatite

mineral deposition

is a crystallization process in which calcium, phosphate, and other ions are taken from the blood plasma and deposited in bone tissue, mainly as needlelike crystals of hydroxyapatite. -begins in fetal ossification and con. throughout life

calcitriol

is a form of vitamin D produced by the sequential action of the skin, liver, and kidneys Promotes intestinal absorption of Ca2+ and phosphate; reduces urinary excretion of both; promotes both resorption and mineralization; stimulates osteoclast activity

Perforating Canals (Volkman's)

join central canals; run at 90 degree angle

concentric lamellae

layers of matrix concentrically arranged around a central (haversian15) canal and connected with each other by canaliculi.

endosteum

lines the internal marrow cavity, covers all the honeycombed surfaces of spongy bone, and lines the canal system, described later, in compact bone.

Wolff's Law

the architecture of a bone is determined by the mechanical stresses placed upon it, and the bone thereby adapts to withstand those stresses.

circumference lamellae

osteocytes lay down matrix in layers parallel to the surface, part of thickening

mineral resorption

process of dissolving bone minerals are released into blood for use in other locations hydrogen pumps in ruffled border of osteoclast secret hydrogen ions into extaceullur fluid...

Endochondral Ossification

process where bone develops from pre-existing hyaline cartilage model -begins when fetus is 6 weeks old and continues into a person's 20's-most bones in body

Intramembranous Ossification

produces flat bones of the skull and most of the collarbone

Step 4 eo

secondary ossification center hollows out by the same process as the diaphysis, generating a secondary marrow cavity in the epiphysis. This cavity expands outward from the center, in all directions. At the time of birth, the bone typically looks like step 4 in figure 7.9. In bones with two secondary ossification centers, one center lags behind the other, so at birth there is a secondary marrow cavity at one end while chondrocyte growth has just begun at the other. The joints of the limbs are still cartilaginous at birth, much as they are in the 12-week fetus in figure 7.10.

calcitonin

secreted by clear cells by the thyroid gland when calcium concentration rises too high lowers ca promotes mineralization little effect in adults may prevent bone loss in pregnant and lactating women

articular cartilage

A thin layer of hyaline cartilage covering the articular surface of a bone at a synovial joint, serving to reduce friction and ease joint movement. -covers bone ends to allow smooth motion

trabeculae

A thin plate or layer of tissue, such as the calcified *** of spongy bone or the fibrous *** that subdivide a gland.

pathological fracture

break in a bone weekend by a disease such as osteoporosis or bone cancer

Composite Tissue

Bone is *** that allows for strength (inorganic) and flexibility (organic)

osteoblast

Bone-forming cell that arises from an osteogenic cell, deposits bone matrix, and eventually becomes an osteocyte.

Flat Bones

Broad and think; Protective: Ribs, Sternum(breast bone), Scapula(shoulder blade), ribs, hip bones

step 6 eo

By the late teens to early twenties, all remaining cartilage in the epiphyseal plate is generally consumed and the gap between the epiphysis and diaphysis closes. The primary and secondary marrow cavities then unite into a single cavity.

Step 2 IO

Calcium phosphate and other minerals crystallize on the collagen fibers of the osteoid tissue and harden the matrix. Continued osteoid deposition and mineralization squeeze the blood vessels and future bone marrow into narrower and narrower spaces. As osteoblasts become trapped in their own hardening matrix, they become osteocytes.

step 5 eo

During infancy and childhood, the epiphyses fill with spongy bone. Cartilage is then limited to the articular cartilage covering each joint surface, and to an epiphyseal (EP-ih-FIZ-ee-ul) plate, a thin wall of cartilage separating the primary and secondary marrow cavities at one or both ends of the bone. The plate persists through childhood and adolescence and serves as a growth zone for bone elongation.

Irregular Bones

Elaborate shapes; Vertebrae and three tiny middle ear bones

Long Bones

Longer than wide; Act as levers; Most important in body movement of the limbs. Humerus, radius, ulna of arm, forearm, femur, tibia, fibula of thigh and leg. Metacarpals, metatarsals, and phalanger of hands and feet

osteoclast (bone dissolver)

Macrophage of the bone surface that dissolves the matrix and returns minerals to the extracellular fluid.

Step 1: EO

Mesenchyme develops into a body of hyaline cartilage, covered with a fibrous perichondrium, in the location of a future bone. For a time, the perichondrium produces chondrocytes and the cartilage model grows in thickness.

Step 1 IO

Mesenchyme first condenses into a soft sheet of tissue permeated with blood vessels—the membrane to which intramembranous refers. Mesenchymal cells line up along the blood vessels, become osteoblasts, and secrete a soft collagenous osteoid21 tissue (prebone) (fig. 7.8) in the direction away from the vessel. Osteoid tissue resembles bone but is not yet calcified.

Step 3 eo

Osteoclasts arrive in the blood and digest calcified tissue in the shaft, hollowing it out and creating the primary marrow cavity. Osteoblasts also arrive and deposit layers of bone lining the cavity, thickening the shaft. As the bony collar under the periosteum thickens and elongates, a wave of cartilage death progresses toward the ends of the bone. Osteoclasts in the marrow cavity follow this wave, dissolving calcified cartilage remnants and enlarging the marrow cavity of the diaphysis. The region of transition from cartilage to bone at each end of the primary marrow cavity is called a metaphysis.

calcification/mineralization

The hardening of a tissue due to the deposition of calcium salts.

epiphysis

The head of a long bone. fig. 7.1 2. The pineal gland (epiphysis cerebri). -expanded ends for joint strength also adds surface area for attachment of tendons/ligaments

Osteosarcoma (osteogenic sarcoma)

The most common and deadly form of bone cancer. It occurs most often in the tibia, femur, and humerus of males between the ages of 10 and 25. In 10% of cases, it metastasizes to the lungs or other organs; if untreated, death occurs within 1 year.

metaphysis

The transitional zone, facing the marrow cavity

Step 3 IO

While the foregoing processes are going on, more of the mesenchyme adjacent to the developing bone condenses and forms a fibrous periosteum on each surface. The spongy bone becomes a honeycomb of slender calcified trabeculae.

Step 4 IO

While the foregoing processes are going on, more of the mesenchyme adjacent to the developing bone condenses and forms a fibrous periosteum on each surface. The spongy bone becomes a honeycomb of slender calcified trabeculae.

Medullary Cavity

a space within the center of the diaphysis. Made of compact bone and spongy bone. the medullary cavity in adulates contains yellow marrow (fat)

osteogenic cells

are stem cells that develop from embryonic mesenchymal cells (see p. 142) and then give rise to most other bone cell types. They are found in the endosteum and inner layer of the periosteum, and central canals. They multiply continually, and some go on to become the osteoblasts .

appositional growth

bone continues to grow in width by depositing new material at bone surface

ossification/osteogenesis

bone formation

diaphysis

bone shaft used for leverage;

stress fracture

break caused by abnormal trauma to a bone

Short Bones

comparable length/width; limited motion; Carpals -wrist/ankle have total of 30 short bones (carpal/tarsal) =in length and width -limited gliding movement...Patella is one

Osseous Tissue

connective tissue with mineral hardened matrix (mostly calcium phosphate) -formed by fibroblast

appositional growth

growing in width-teocytes embedded in calcified matrix have little room to spare for the deposition of more matrix internally so then it is limited

interstitial growth

growth in height result of chondrocyte multiplication in zone 2 and hytrophy in zone 3 that pushes the zone of reverse cartilage toward the end of the bone

Red Marrow

hemopoietic tissue that produces blood cells. Found in childern; remains in adult skulls, vertebrae, ribs, sternum, pro heads of femur/humerus, and part of pelvic girdle

parathyroid hormone

hormone secreted by the parathyroid glands that raises blood calcium concentration by stimulating bone resorption by osteoclasts, promoting intestinal absorption of calcium, and inhibiting urinary excretion of calcium. -Indirectly activates osteoclasts, which resorb bone and raise blood Ca2+ concentration; inhibits urinary Ca2+ excretion; promotes calcitriol synthesis

Yellow Marrow

in adults, most red marrow changes to fatty yellow marrow -does not produce blood cells unless it covers back to red bone marrow

bone marrow

soft tissue that fills all bone spaces, occupies marrow cavity of long bone