AnaPhy Prelims - Skeletal

Osseous Tissue

a complex and dynamic living tissue, continually engages in a process called remodeling

Remodeling

the construction of new bone tissue and breaking down of old bone tissue.

diaphysis

bone’s shaft or body

long, cylindrical, main portion of the bone

Epiphyses

the proximal and distal ends of the bone

Metaphyses

region between the diaphysis and epiphyses

epiphyseal plate

layer of hyaline cartilage that allows diaphysis of the bone to grow length

epiphyseal line

when a bone ceases to grow in length at about ages 14–24, the cartilage in the epiphyseal plate is replaced by bone

articular cartilage

thin layer of hyaline cartilage covering the part of the epiphysis where bone forms articulation with another bone

reduces friction and absorbs shock at freely movable joints

periosteum

tough connective tissue sheath and its associated blood supply that surrounds the bone surface wherever it is not covered by articular cartilage

Sharpey’s fibers

Thick collagen fibers that connect the periosteum firmly to the bone underneath. Think: “anchors the periosteum to the bone.”

Medullary cavity / Marrow cavity

A hollow space inside the shaft (diaphysis) of a long bone. It contains yellow bone marrow and blood vessels in adults.

Yellow bone marrow

Fatty tissue found inside the medullary cavity of adults. It mainly stores fat.

Endosteum

A thin membrane that lines the inside of the medullary cavity. It contains bone-forming cells and a small amount of connective tissue.

hydroxyapatite

Hard mineral crystals made mainly from calcium and phosphate.

They give bone its hardness.

Osteoprogenitor cells

unspecialized bone stem cells that can develop into osteoblast.

only bone cells to divide

found along the inner portion of the periosteum, in the endosteum, and in the canals within bone that contain blood vessels

osteoblasts

bone building cells that produce materials needed to make bone matrix and start calcification - osteocytes

osteocytes

mature bone cells

osteoclasts

huge cells derived from the fusion of as many as 50 monocytes

concentrated in the endosteum

resorption

breakdown of bone extracellular matrix

compact bone tissue

strongest form of bone tissue

found beneath periosteum

Osteon / Haversian system

The basic structural unit of compact bone. It looks like a small cylinder made of several layers.

Concentric lamellae

Circular layers of mineralized bone matrix that surround the central canal. Think of tree rings.

Central canal / Haversian canal

A small canal in the center of an osteon that contains blood vessels and nerves.

Lacunae

Small spaces between the lamellae that contain osteocytes. Think: “little lakes where bone cells live.”

Osteocytes

Mature bone cells that live inside the lacunae and maintain the bone.

Canaliculi

tiny channels connecting the lacunae to each other and to the central canal. Allows nutrients and waste to move through the bone

Extracellular fluid

fluid inside the canaliculi that helps carry nutrients and remove wastes

Gap junctions

connection between neighboring osteocytes that allow them to communicate with each other

Spongy bone tissue

bone tissue found inside bones

lightweight and made of a network of thin bony structures

Trabecular bone

Another name for spongy bone tissue.

Trabeculae

Thin, beam-like structures of spongy bone that support the bone and are arranged along lines of stress.

Red bone marrow

Soft tissue that produces blood cells. It is found in the spaces between trabeculae in certain bones.

Yellow bone marrow

Fat-rich tissue that stores energy as fat. It can fill the spaces between trabeculae in certain bones.

Hemopoiesis

The process of producing blood cells. It occurs in red bone marrow.

Sesamoid bones

Bones that develop within tendons, such as the patella (kneecap).

Intramembranous ossification

bone forms directly within mesenchyme

arranged in sheetlike, resembles membrnaes

endochondral ossification

bone forms within hyaline cartilage that develops from mesenchyme

Ossification center

the site of cluster

Mesenchyme → osteoprogenitor cells → osteoblasts

Development of ossification center

Osteoblasts secrete matrix → osteocytes form → calcium/minerals harden matrix

Calcification

Matrix forms → trabeculae fuse → spongy bone → red bone marrow develops

Formation of Trabeculae

Mesenchyme at the outside condenses → periosteum forms

Development of periosteum

Bone is destroyed and rebuilt → reaches adult size and shape

Remodeling

Mesenchymal cells cluster and differentiate into chondroblasts

development of cartilage model

Cartilage ECM

Chondroblasts produce______, forming a hyaline cartilage model.

The cartilage model grows in length through interstitial growth.

It grows in thickness through appositional growth.

growth of cartilage model

Hypertrophy

When chondrocytes in the middle enlarge

Interstitial growth

endogenous growth

cartilage model grows in length

Appositional growth

exogenous growth

cartilage model grows in thickness

nutrient artery enters the diaphysis

blood vessels and osteoprogenitor cells enter the developing region

perichondrium becomes periosteum

Spongy bone trabeculae form.

Ossification progresses toward both ends of the shaft.

Development of primary ossification center

Osteoclasts resorb some of the newly formed bone.

A medullary cavity develops in the diaphysis.

The shaft wall develops into compact bone.

Development of the medullary (marrow) cavity

Blood vessels enter the epiphyses.

Secondary ossification centers develop, usually around birth.

Bone replaces the cartilage in the epiphyses.

Spongy bone remains inside the epiphyses; a medullary cavity does not normally form there.

Development of the secondary ossification center

hyaline cartilage becomes articular cartilage

hyaline cartilage remains between the diaphysis and epiphysis

Formation of articular cartilage and the epiphyseal (growth) plate.

Chondroblast

cells that produces cartilage ECM

Chondrocyte

mature cartilage cell

Hyaline cartilage model

cartilage structure that serves as the template for the developing bone

Periosteum

connective tissue covering the cartilage model

periosteum

connective tissue covering the outer surface of bone

Bone remodeling

ongoing replacement of old bone tissue by new bone tissue

bone resorption

removal of minerals and collagen fibers from bone by osteoclasts

bone deposition

addition of minerals and collagen fibers to bone by osteoblasts.