Formed by breakdown of some of the new Spongy Bone(in elongating Shaft) 

Red Bone Marrow develops(from contents carried by Periosteal Bud that invaded)

(will eventually produce all types of Blood Cells)

Remain for future Bone Growth

Eventually harden in mid-late teens(Due to Estrogen)

Remains on the Ends(Epiphyses), resisting friction.

Deterioration of AHC is called: Osteoarthritis

Stack of fibrous membranes change into Bone

- Ex: mostly Flat Bones

- Mesenchyme Cells group as an Ossification Center, produce Osteoblasts, make & release Osteoid, forming Spongy Bone.

A type of undifferentiated Cell, capable of producing other types of Cells

- Ex: Osteoblasts

Produces most of the human body (it is Mesenchyme)

- Ex. Muscles

- Ex. Connective Tissues (includes: Bone/ Cartilage & more )

Growth Plate(Epiphyseal Plate) growth process

- 5 Zones of the Growth Plate

up by Epiphysis:

Zone 0: Resting Zone

We are saying 5 (Text has 4)

Zone # 1: Proliferation Zone: Cartilage Cells dividing (forming new Cart. Cells)

Zone # 2: Hypertrophic Zone: older Cart. Cells enlarging

Zone # 3: Calcification Zone: Cart. Cells die from Calcification - bl. vessels enter

down at Shaft:

Zone # 4: Ossification Zone: new Bone forms, adding to Shaft end 

Circulates in Blood when more blood Calcium is needed

- Action: stimulates Osteoclasts to break down Bone, releasing Calcium into the Blood

- Note: When excess Calcium levels in Blood, Bone formation occurs instead (now, Parathyroid Hormone would not be released).

1) Comminuted: (3 or more pieces)

2) Compression: (crushed bone) Ex: collapsed Vertebrae in Osteoporosis

3) Spiral Fx: (ragged break due to: twisting forces Ex. common in Sports)

4) Epiphyseal Fx: break through Growth Plate(Epiphyseal Plate) (Caution: Bone may then grow abnormally)

5) Depressed Fx: pressed inward Ex: Skull depression Fx

6) Greenstick: young bone with high Osteoid content versus Mineral Salts - incompletely breaks (like green twig)

Hematoma forms - a clotted mass of blood

Fibrocartilage Callus - forms 

Bony Callus - replaces the Fibrocartilage, instead

Bone remodels - the Bony Callus

(remodeled form is like before break, because same forces are still being applied)

Remember: bone continually remodels 

“soft bones”

- Ex. Rickets due to: Vit. D deficiency / or lack of dietary Calcium

disorganized, scattered patches of Bone resorption, replacement by Spongy Bone (weaker)

- cause: unknown 

often accidentally found on X ray 

More bone resorption, rather than Bone building

- seen in older people (weaker bones break easier) 

- more after Menopause in females

Bone Pain

- Note: “algia” (pain)

- Ex. Cephalgia (headache)

- Ex. Fibromyalgia

-Hyaline Cartilage (shiny, glossy, harder )

-Fibrocartilage (alternating layers of : Collagen Fibers & Cartilage Cells ) 

-Elastic Cartilage (flexible Elastic Fibers, Ex: External Ear / Epiglottis)

-Long Bones (Ex. Humerus / Femur)

-Short Bones (Ex. Ankle Bones & Wrist Bones) 

-Flat Bones (Ex: most Cranium Skull Bones, Sternum / Scapula)

-Irregular Bones (Ex. Vertebrae / Coxal Bone)

-Compact Bone: 2 outer layers (like slices of Bread) in between is:

-Spongy Bone /Diploë: The Spongy Bone acts as Sandwich filling

Ex. Periosteal Cells (on: inner surfaces)

Ex. Endosteal Cells (on: outside surfaces)

[flat cells on Bone surfaces]

Double-layered Membrane around Bone

(in Long Bones, only around the Shaft, not around the Ends in Joints) 

- Note: outer fibrous part of Periosteum is: Dense Irregular Connective Tissue. 

- Note: inner Osteogenic part has: Osteogenic Cells , Osteoblasts, & Osteoclasts

1. Epiphysis

2. Diaphysis

3. Epiphyseal Plate

Growth Plate (remaining Hyaline Cartilage between each End & the Shaft) 

Note: When mature, a person stops growing taller because Estrogen causes the Epiphyseal Plate to ossify(harden), thereafter, it is then called: Epiphyseal Line

- In the interior of the Epiphyses (Long Bone Ends)

- A little is around Medullary Cavity (in Shaft)

- When young, filled with Red Bone Marrow (produces all Blood Cells)

- As Adult, red bone marrow turns to Yellow Bone Marrow(fat) [no longer making Blood Cells]

- Ex. RBCs (Red Blood Cells ) ( Erythrocytes)  

- Ex. WBCs (White Blood Cells) ( Leukocytes ) 

- Ex. Platelets (Thrombocytes) 

(All are actually pieces off a huge Megakaryocyte Cells)

May be located as outer part of the Long Bone Shaft (just underneath the Periosteum) + some in Epiphyses

Note: Periosteum attached by: Sharpey’s Perforating Fibers  

Edge is Spongy Bone (Trabeculae + Endosteum membrane coating) 

Note: Blood Vessels(& NN) 

- in Volkmann’s Perforating Canals (run perpendicular to shaft axis) (taking blood vessels into Medullary Cavity region) 

- In Central Haversian Canals (along bone long axis) each of these Canals is the center of an Osteon (Haversian System)  

Hard, white bone between Periosteum & Medullary Cavity (of the Bone Shaft (Diaphysis)) 

- also, small amount in bone Ends (Epiphyses)(singular: Epiphysis)

Compact Bone 

(Spongy Bone - does not have Osteons) 

(Compact Bone - does not have Trabeculae)

The Basic Structural Units of Compact Bones 

(hollow cylinders - when cut, resemble concentric “Onion Rings”, also known as: Haversian Systems)

Each contains one Artery, Vein, Nerve Cell part - Each Osteon has this.

- Volkmann’s Perforating Canals link these to the Medullary Cavity.  

“Onion Ring” cylinder is a _____________

- On its perimeters are little dots called: Lacunae (singular Lacuna) 

- One mature bone cell(Osteocyte) lives in each Lacuna.

1.) Regular - Lamellae within each: Osteon ( Basic Structural Unit of: Compact Bone ) 

2.) Interstitial Lamellae - as filler, in the spaces between Osteons 

3.) Circumferential Lamellae - in concentric rings cylinders, out at the perimeter of Long Bone shaft(Diaphysis)

- Note: Circumferential Lamellae are between the Periosteum & inside where the Osteons are.

The 5 types of Bone Cells(osteoblast, osteoclast, osteocyte, and osteoprogenitor bone cells) + 

Osteoid: The Organic materials of Matrix

(about 1/3 of Matrix)

(Ground Substance + Fibers(specifically Collagen))

contains molecules: Ex. Proteoglycans Ex. Glycoproteins

Bone Composition: Inorganic Materials

(about 2/3 Bone Matrix)  

Mineral Salts (mostly: Calcium Phosphates) 

- Note: Bone has same ability to resist Tension, as does Steel

- Note: This is where the Body stores extra Calcium

When a piece of Hyaline Cartilage changes into Bone

- Note: Some of the Cartilage remains afterwards

... Forms around future Long Bone Shaft 

- Note: Primary Ossification Center is within the future Shaft.