Anatomy chapter 6: Bones (as organs) SLCC Eric Green

The skeletal system includes what 3 things?

Organs called bones.

Cartilage

*Ligaments that bind together, support, and stabilize bones.

Connective tissues of a bone:

*Bone CT

*Cartilage

*Red and Yellow bone marrow

Nervous Tissue of bone:

there are neurons that send processes into a bone (which is why it hurts to break a bone).

Epithelial tissues of bones are found where?

Blood vessels inside of bones have and epithelial lining.

Muscle tissue of bones:

Blood vessels inside a bone have a type of muscle called smooth muscle within their walls.

What are the 4 functions of bones?

1.) Support and protection.

2.) Movement support

3.) Hemopoiesis (blood cell production)

4.) Mineral and energy storage

Function: Support and Protection examples:

The cranial bones protect the brain, vertebral bones protect the spinal cord, and ribs protect many thoracic organs.

Function: Movement support:

Most skeletal muscles are attached to bones.

Function: Hemopoiesis (blood cell production):

Blood cells are borne in red bone marrow, a kind of reticular CT.

Most blood cells are born in flat bones of skull, vertebrae, ribs, sternum, os coxae, humerus, and femur.

Where does red bone marrow reside?

Within spongy bone lattices.

Functions: Mineral and energy storage:

*More than 90% of bodies Ca++ and phosphate.

*Yellow bone marrow stores energy in the form of lipids.

Where is yellow bone marrow found?

Medullary cavity of a bone

4 Classifications of Long Bones:

*greater length than width

*Common in appendicular skeleton

*Solid external walls are compact bone.

*Spongy bone inside

Long bone examples:

Humerus, radius, ulna, metacarpals, and phalanges in upper limb. Analogous bones in lower limb.

Classifications of Short bones:

Length and width are about equal.

Examples of Short bones:

Carpals and tarsals, patella.

Classification of Flat bones:

Two outer layers of compact bone, with spongy bone in between.

Flat bone examples:

roof of skull, scapulae, sternum, ribs.

Classification of Irregular bones:

Complex shapes.

Irregular bone examples:

vertebrae, some cranial bones.

Diaphysis =

shaft

Epiphysis=

knobby end

metaphysis=

between diaphysis and epiphysis.

Metaphysis in 1.)children and 2.) adults:

1.) Is the location of lengthwise bone growth in children.

2.) Contains the thin layer of compact bone within otherwise spongy bone called the epiphyseal line.

What is the epiphyseal line?

The remnant of the growth plate where bone growth occured in youth.

Medullary Cavity

Hollow area with yellow bone marrow (in adults).

Yellow bone marrow is made up of what types of CT?

Adipose CT and Reticular CT

Where is articular cartilage found?

At the ends of epiphyses.

What kind of nerves supply bones?

Sensory nerves that signal injuries or pain.

The main artery and vein of bones and function:

Nutrient artery and vein, which enter through nutrient foramen.

Supply the diaphysis of a long bone.

Metaphyseal arteries and veins:

Supply the daphyseal side of the epiphyseal plate.

Epiphyseal arteries and veins:

Supply the epiphyses.

Periosteal arteries and veins:

supply the outer regions of a bone

Periosteum

*analagous to the perichondrium of cartilage.

*tough sheath of dense irregular CT and bone CT

*Found in outer surfaces of bone, except where there is articular cartilage.

*Perforating fibersconnect periosteum to the underlying bone CT

*The layer of bone to which tendons and bones are attached.

Endosteum:

* Lining of cells inside bone cavities.

*Contributes to bone growth and repair.

osteoprogenitor cells

*Stem cells

*Divide to give rise to osteoblasts.

*Live in periosteum and endosteum.

Osteoblasts

*Secrete collagen that is assembled extracellularly into fibers.

* The fibers are then incased in minerals (ECM) in lacunae and become Osteocytes.

Osteocytes

*mature bone cells

*maintain ECM

*detect stresses on bone, and signal osteoblasts to make more bone tissue.

Osteoclasts

*Large multinuclear cells.

*Perform bone resorption:

-Secreted HCl dissolves minerals

-Secreted enzymes dissolve the collagen fibers.

Characteristics of bone CT:

Strong and durable, but not brittle. More solid than cartilage.

Collegen fibers in ECM provide:

Flexibility and tensile strength to resist stretching and twisting forces.

Ground substance of ECM:

Contains minerals, especially calcium and phosphate that'st deposited on protein fibers. This gives the bone CT compressional strength, to resist crushing forces.

How much mass of the bone CT is minerals?

2/3

compact bone organization

*Forms out shell of bones

*solid(but with some canals and spaces in it).

*organized into structures called osteons.

Osteon structure:

*Central canal - blood vessels and nerves

*Lamellae- concentric rings around central canal

*Lacunae- spaces where osteocytes live

*Caniculi- pathways through bone.

Spongy bone organization:

*found in interior bone

*Lattice work- reduces weight but maintains strength

*Crisscrossing trabeculae provide strength in all directions.

*Osteocytes live within lucanae

*Red bone marrow found with in lattice work