skeleton and bone tissues and types

Axial Skeleton

The part of the skeleton that includes the skull, vertebral column, and rib cage.

Appendicular Skeleton

The part of the skeleton that includes the limbs and girdles (shoulder and pelvic girdles).

Primary ossification center

The first location in a developing bone where ossification (bone formation) occurs.

Secondary ossification center

Locations in bones where ossification occurs after the primary center, usually in the epiphyses.

function of the skeleton

• Protection: Encloses internal organs 

• CNS, Cardio, Resp, Repro... 

• Support: Rigid structural framework 

• Movement: Anchors skeletal muscle 

• Mineral Storage: homeostasis 

• Blood cell production: Red bone marrow 

• Fat (energy storage): Yellow bone marrow 

Blood Cell production and energy storage as a

function of the skeleton

• Bone Marrow is a dynamic semi-solid tissue found within bone

• Red Marrow: high number of haematopoietic stem cells (blood cell formation)

• Erythrocytes, monocytes, neutrophils, etc

• Located in spongy/trabecular bone, in ends of bones or flat bones

 

• Yellow Marrow: high number of adipocytes (fat cells) for energy/fat storage

           > Located in medullary cavity of long bones

Collagen fibers

Organic substances produced by the body that provide strength and flexibility in bone.

bone types

• Describes bone shape and not length

• Long bones in arms or legs

• Short bones mainly in wrist and hands or ankle

• Skull bones and ribs/sternum are flat

• Sesamoid bones form from within tendon, eg is patella

• Irregular is vertebra

 

Long bones

Bones that are longer than they are wide, such as those found in the arms and legs.

Short bones

Bones that are approximately equal in length and width, such as those in the wrist and ankle.

Irregular bones

Bones that have complex shapes, such as vertebrae.

Cortical bone

Also known as compact bone, it's the dense outer layer of bone.

Prominent composition/type in diaphysis (shaft of long bone)

• Contains Osteons (how bone is built)

     > Main unit of compact bone microstructure

• Strength in uniform direction due to being compact

Trabecular bone

Also known as spongy bone, it's characterized by a lattice-like structure.

Prominent composition/type in heads of long bone & other bone structures (flat, irregular, etc)

 • Contains Trabeculae (bony struts)

• Strength in multiple directions bc of latticework and space In/ around it, has red bone marrow which is essential for the making of blood cells (haematopoiesis)

gross anatomy of the long bone

bone as a suppourtive connective tissue/ its composition

Bone extracellular matrix

=

Osteons

The structural unit of compact bone, consisting of a central Haversian canal surrounded by concentric lamellae.

Haversian canal

Central canal in an osteon that contains blood vessels and nerves.

Lacunae

Small cavities in bone tissue that contain osteocytes.

Osteoclast

Bone-resorbing cell responsible for breaking down bone tissue.

Osteoblast

Osteocyte

Mature bone cell that maintains the bone matrix and communicates via canaliculi.

osteoprogenitor cells

 

osteon components

Osteon Components (A.K.A. Haversian System) from compact bone

Trabeculae

Structural units of spongy bone, consisting of thin struts that create a web-like matrix.

Trabeculae is found in spongey/ trabecular bone, in the heads of bones

• Each Trabeculae contains:

• Lamella (layers of bone) arranged in plates or sheets

• Much like interstitial lamella

•  Lacunae & Canaliculi for osteocytes

• Trabeculae do NOT have

• Concentric lamella (layered rings of bone)

• A Haversian (central) canal as the cells can grab on the blood vessels from the surrounding area

  

bone cell nutrition

Osteoprogenitors, Osteoblasts and Osteoclasts

how do osteons forms

Osteons are created during the process of bone formation and maintained or updated during the bone remodelling process

1. 

function of cartilage tissue

• Maintains shape

• Resist compression & absorbs shock

•  Provides smooth surface to minimise friction (articular cartilage in long bone does this and resists compression)

cartilage compositon and cells

types of cartilage- hyaline

Appearance: Clear, glassy, fine collage fibres

Location: Ends of long bones at moveable joints; trachea

Function: Smooth surface prevents friction (thus pain) when joint moves; holds airways open so air can pass through

fibrocartilage

Very fibrous and with lots of collagen bundles, giving it more strength and resistance, so good for areas that need to maintain integrity

elastic cartilage

• Lots of elastic fibres, giving web appearance, have some stretch and recoil back into shape

ossification

intramembranous ossification

•  Bone formation within the embryonic tissue membrane, during first two months of development (primary method of bone formation for these 2 months)

• Mainly takes place for the flat and irregular bones of the skull

 

• 

intramembranous ossification steps

Based on growth factors in area ( a signal sent in area)

endochondral ossification

Bone formation within the Cartilage (-chondral) model

 

 

interstitial vs appositional growth

interstitial growth

(inside tissue at interstitial plate)

• Bone growth in length

• Occurs ‘within bone’

• Occurs at Epiphyseal Plate

• Chondrocytes divide increasing Hyaline cartilage from the inside

• Growth of cartilage pushing epiphysis further from metaphysis

• Hyaline cartilage gradually ossifies (Adulthood)

• Epiphyseal line

s

appositional growth

 Bone growth in width,  Occurs on ‘edges of bone’

• Bony structure is formed

• Osteogenic cells within periosteum differentiated to form osteoblasts

• Osteoblasts lay down new layers of bone (lamellae) on the edges of bone

• Osteoblasts trap themselves TURN INTO osteocytes

bone remodelling

Process of bone cells removing old bone and replacing with new bone

• Osteoclasts removing bone by reabsorbing it at equal rates of Osteoblasts forming new bone (important balance)

• Balance of bone removal and bone formation = repair/maintenance

• Breaking down of the bones releases minerals into the body

• Adeq

bone fracture and repair