Anatomy Chapter 6

osteoclast

Secretes acid, erodes bone matrix crucial for remodeling

Endochondral ossification follows five steps.

(a) Mesenchymal cells differentiate into chondrocytes. (b) The cartilage model of the future bony skeleton and the perichondrium form. (c) Capillaries penetrate cartilage. Perichondrium transforms into periosteum. Periosteal collar develops. Primary ossification center develops. (d) Cartilage and chondrocytes continue to grow at ends of the bone. (e) Secondary ossification centers develop. (f) Cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage.

Intramembranous ossification follows four steps.

(a) Mesenchymal cells group into clusters, and ossification centers form. (b) Secreted osteoid traps osteoblasts, which then become osteocytes. (c) Trabecular matrix and periosteum form. (d) Compact bone develops superficial to the trabecular bone, and crowded blood vessels condense into red marrow.

Fracture and remodeling

1. bleeding, clot = fracture hematoma 2. callus with cartilage and fibers 3. cartilage in callus converted to bone 4. Remodeling recreates original structure.

Functions of bone (5)

1. support of the weight of the body 2. storage of Ca salts 3. blood cell formation in the red marrow of long bones 4. Protection of internal organs (skull, vertebrae, ribs) 5. Leverage structure for muscles to work on

Ramus

angle. forms an angle

Process

any projection on a bone

2/3 of weight is

calcium phosphate

Osteocytes and osteoblasts can communicate with each other and receive nutrients via long cytoplasmic processes that extend through

canaliculi channels within the bone matrix.

1/3 of weight is

collagen fibers

Matrix is like

concrete and steel. Crystals resist compression, while the flexible element prevents shattering.

Bone is what kind of tissue?

connective

spongy bone, also known as cancellous bone

contains osteocytes housed in lacunae, but they are not arranged in concentric circles. Instead, the lacunae and osteocytes are found in a lattice-like network of matrix spikes called trabeculae. In addition, the spaces in some spongy bones contain red marrow, protected by the trabeculae, where hematopoiesis occurs.

The wider section at each end of the bone is called the

epiphysis (plural = epiphyses), which is filled with spongy bone. Red marrow fills the spaces in the spongy bone.

facet

flat surface

Osteogenic

is a stem cell found in periostem and endosteum turn into osteoblasts

osteoblasts

is the bone cell responsible for forming new bone and is found in the growing portions of bone, including the periosteum and endosteum.

The osteocytes are located inside spaces called

lacunae (singular = lacuna), found at the borders of adjacent lamellae (concentric matrix).

Each osteon is composed of concentric rings of calcified matrix called

lamellae (singular = lamella)

Trochanter

large round

line

less prominent ridge

The hollow region in the diaphysis is called the

medullary cavity, which is filled with yellow marrow. The walls of the diaphysis are composed of dense and hard compact bone.

crest

prominent ridge

tuberosity

rough surface

condyle

rounded surface

spine

sharp process

Chambers

sinus or antrum (normally filled with air)

Tubercle

small rounded process

trochlea

smooth, grooved articular process

A long bone has two parts:

the diaphysis and the epiphysis.

osteocyte,

the primary cell of mature bone and the most common type of bone cell. Each osteocyte is located in a space called a lacuna and is surrounded by bone tissue. Osteocytes maintain the mineral concentration of the matrix via the secretion of enzymes. Like osteoblasts, osteocytes lack mitotic activity.

The diaphysis is the

tubular shaft that runs between the proximal and distal ends of the bone.

Openings

Foramen (hole through bone); fissure (slit through bone); canal/meatus (passage through core of bone)

Depressions

Fossa (shallow depression); Sulcus (narrow groove)

Running down the center of each osteon is the central canal, or

Haversian canal, which contains blood vessels, nerves, and lymphatic vessels.

osteon, or Haversian system.

The microscopic structural unit of compact bone