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Week 6 Chapter 6 in AP 1

5 major functions of bone SSBPL

Support, protection, movement, mineral storage, hematopoiesis.


"Making red blood cells.

Categories of Bones

Long Bones, Short Bones, Flat Bones, Irregular Bones, Sesamoid Bones, Sutural Bones.

Long Bones

Cylindrical & Narrow. Wider at ends. Ex: Femur, Humerus.

Short Bones

Cube shaped, as broad as they are long. Ex: Carpal, Tarsal.

Flat Bones

Broad, Thin & usually curved. Ex: Ribs, Shoulder Blade

Irregular Bones

Catchall for uncategorized bones Ex: Face, Vertebra

Sesamoid Bones

Bones that grow inside tendons. Ex: Patella. Not present at birth.

Sutural Bones

Connection between bones. Saw tooth connectors. Only on the skull. Island of bone at suture. They are different on every person, and not everyone has them. Genetic tendencies.


Main Shaft-like portion. Hollow and cylindrical, compact bone. Weight bearing strength without being heavy.


Broadened ends. Ends of long bone, large surface area for interaction with other bones. Stability of joints, Spongy/Cancellous Bone. Contains red bone marrow.

Epiphyseal Plate

Growth Plate. Marks separation between epiphysis and diaphysis.

Articular Cartilage

Covers parts of the bones that will be in joints. A layer of hyaline cartilage. Acts as a shock absorber. Compresses and returns to original shape. (What wears out when you need a knee replacement.


Outer covering of the bone. Everywhere but articular surfaces. Dense, white, fibrous membrane. Penetrates underlying bone.(Literally Invade) Contains cells that form bone & cells that destroy bone. (Repair and remodel) Blood vessels in periosteum become incorporated into bone.(Carries Blood into Bone) Essential to bone cell survival as well as repair & remodeling of bone.

Medullary Cavity

Hollow space inside diaphysis. Also called marrow cavity. Yellow bone marrow. (Can contain red bone marrow depending on health and age.

Yellow Bone Marrow

Stores Fat.


Allows for no exposed bone. Thin, fibrous membrane. Lines medullary cavity of long bones. Lines open spaces in spongy bone. Contains different types of bone cells & stem cells.

What 6 things make up a long bone?

Diaphysis, Epiphyses, Articular Cartilage, Periosteum, Medullary Cavity, Endosteum.

Parts of a Flat Bone

Inner and outer tables (Bone Sandwich) Diploe. Covered with periosteum. Lined with Endosteum. Cancellous bone filled with red marrow, even into adulthood. Can be used diagnostically--test for leukemia.Also differ in proportion of 2 different types of bone tissue.Compact Dense & solid looking.


Spongy Bone in middle. (Meat)

Bone Tissue or "Osseous Tissue"

A connective tissue. Most distinctive connective tissue in body. Consists of cells, fibers & extracellular material. Matrix is hard ECM. Hardened & calcified. Much more abundant than bone cells. Contains a lot of collagen. Balance between weight and strength.

Composition of Bone Matrix

2 principle chemical components. Inorganic Salts & Organic Matrix. Components of matrix make bone & cartilage springy & resilient.

Organic Matrix

1/3 of bone matrix
Ground substance. Connective tissue cells secrete. Provides support & adhesion between cellular elements & fibrous elements. Actively involved in metabolic functions needed for growth, repair & remodeling of bone.

Inorganic Salts

Approximately 2/3 of matrix. Hydroxyapatite crystals
Calcium & phosphorus. Calcification 85% hydroxyapatite. 10% of inorganic salts are calcium carbonate. Include magnesium, sodium, sulfate & fluoride. Harmful substances Radium. Strontium-90. Uranium. Plutonium.

Chondroitin sulfate

Large protein
Compressible & elastic


Amino sugar
Important for cartilage formation, maintenance & repair

What are the 4 types of bone cells?

Osteocytes, Osteoblasts, Osteoprogenitor cells, Osteoclasts


TRAPPED CELLS. Mature cells, develop from osteoblasts, control day-to-day activities (each occupies a lacuna, a pocket sandwiched between layers of matrix) Mature non-dividing Osteoblasts. Surrounded by matrix & living inside lacunae.Cytoplasmic processes extend into Canaliculi & connect to other Osteocytes.


MAKE BONE. Make bone; synthesize and secrete the organic constituents of the bone matrix; once surrounded by the matrix they mature into osteocytes. Collagen fibers are framework for secreted material. Make up ECM of bone.

Osteoprogenitor cells

STEM CELLS. Change shape of bone, Mitotically active. Differentiate into osteoblasts.


BREAK DOWN. Giant cells that resorb or break down bone matrix, releasing calcium ions into the blood. Break down bone to change the shape. Multinucleate. Formed by fusion of several cells.

Compact Bone

80% of total adult bone mass.


Cylindrical shaped structural unit. Surrounds central canal that runs lengthwise through bone. Bone cells are cemented into place by matrix of osteon.
AKA: "Haversian systems"

What are the 5 components of an Osteon?

Lamellae, Lacunae, Canaliculi, Central Canal, and Transverse Canals.


Concentric layers of bone in osteon. Interstitial lamellae. Circumferential lamellae.


Small spaces in bone matrix where bone cells are trapped
Filled with tissue fluid & bone cells


Small canals that radiate out of lacunae in all directions
Connect lacunae to one another & to central canal

Central Canal

Also called osteonal or Haversian canal. Extends lengthwise for course of osteon. Lined with Endosteum. Contains blood vessels, lymphatics & nerves. Nutrients & O2 move from central canal to Canaliculi to lacunae to bone cells.

Transverse Canals

Carry nerves & blood & lymph vessels from exterior surface of bone to osteons. AKA: Volkmann canals.

Cancellous OR Spongy Bone

Diploe in flat bones. 20% of total bone mass in adult. Structure different than compact bone. Does not have a high level of organization. No osteons. Has Trabeculae. Canaliculi allow delivery of nutrients & removal of wastes. Usually sandwiched between 2 layers of compact bone. Cells connected to blood supply & each other via canaliculi. Blood supply in bone abundant to support survival of bone cells.


Organization of spongy bone. Placement not random, direction of force/load determines organization.

What are the two types of bone marrow?

Yellow Marrow
Red Marrow

Bone Marrow

Soft, diffuse connective tissue. "Myeloid tissue." Site of production of blood cells. Located in Medullary cavities of some long bones
Some spongy bone areas.

Yellow Marrow

Higher fat content, No blood cell production.

Red Marrow

Almost all bones in infant or child's body. Produces blood cells.
Locations in Adult: Ribs, Bodies of vertebrae, Ends of humerus,
Pelvis, Femur.

What happens when there is a decrease of blood to bone?

Yellow marrow can revert back to red marrow. Examples: Chronic anemia, Radiation exposure, Toxic chemicals, Certain diseases, Transplant as therapeutic device.

How does skeletal formation begin in utero?

Begins with cartilage.


Bone formation. Cartilage/fibrous structures as templates, Bone matrix gradually replaces cartilage, Reshaping, remodeling & conversion to mineralized bone.

What is the bone tissues response to stress or injury?

Sculpting occurs by osteoblasts & osteoclasts. Allows bones to by change size, shape & density.

Endochondral ossification

Bone formation in cartilage. Formation starts at center & moves towards ends. Primary ossification center. Center of bone.Blood vessels grow into bone. Grows toward epiphyses. Interstitial growth. Secondary ossification centers: Form in epiphyses. Growth toward diaphysis. Epiphyseal plate: Layer of cartilage, Growth in length takes place on sides of plate. Epiphyseal fracture. Most bones made this way.

Intramembranous Ossification

Formation of bone within connective tissue membrane. Osteogenic stem cells in membrane differentiate to osteoblasts. Ossification centers
Clusters of osteoblasts. Bone deposited at ossification centers grows together. Appositional growth. Growth only on outer surface of bone. A few flat bones are formed this way.

Types of Blood & Nerve Supply to Bone

Nutrient Artery & Vein
Metaphyseal Vessels
Periosteal Vessels

Periosteal vessels

Provide blood to the superficial osteons of the shaft

Metaphyseal vessels

Supply blood to the inner surface of each epiphyseal cartilage

Nutrient Artery & Vein

Blood vessels that supply the diaphysis form by invading the cartilage model as endochondral ossification begins. Through nurtient foramen.

Bone remodeling

Woven bone replaced by lamellar bone. Much stronger. Has primary and secondary osteons.

What age does bone loss become greater that bone formation?

35 to 40

Parathyroid hormone

Increases blood levels of calcium (stimulates breakdown of bone and rate at which calcium is removed from urine and absorbed from the gastrointestinal tract) Increased activity of osteoclasts. Stimulates Vitamin D Synthesis.


Protein released by thyroid gland when Calcium in high. Stimulates osteoblast activity & inhibits osteoclast activity. Results in Calcium moving from blood to bone. Not as important as PTH.


Parathyroid Hormone

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