Anatomy and Physiology Skeletal System and Articulations Lecture Notes

What are the functions of bone?

• support

• protection

• movement

• mineral storage

• hematopoiesis (forming blood cells)

What is the axial skeleton and what part of the body are included?

It is the vertical body axis which includes the skull, vertebral column and thoracic cage (ribs and sternum)

What is the appendicular skeleton and what part of the body are included?

This skeleton is made of up limb bones and their connection to the axial skeleton

What are the other names for spongy bone?

cancellous and trabecular skeleton

What is another name for compact bone?

dense bone

define: tendon

muscle to bone connection

define: ligament

bone to bone connection

What are the classes of bone?

• long bones

• short bones

• flat bones

• irregular bone

• sesamoid bone

What are long bones and where are they found?

Long bones have a length that is greater than the width. An example of this would be arm or leg bones.

what are short bones and where are they found?

short bones have a length that is about equal to the width so they are circular-ish. They are generally in the wrists and ankles

what are flat bones and where are they found?

They have a very thin surface and the bones can be curved. This most prominent of these bones is the skull, and the sternum

what are irregular bones and where are they found?

these are the bones that are irregular shapes, like vertebral bones

What are sesamoid bones and where are they found?

Sesamoid bones are little bony nodules that are suspended in a joint (floating bones). The biggest sesamoid bone is the knee cap

What are the regions of a long bone?

• diaphysis

• epiphysis

• metaphysis

What is the diaphysis region of a long bone?

• middle region

• has medullary cavity (hollow portion for bone marrow)

What is the epiphysis region of a long bone?

• end bit of a bone

• covered by hyaline cartilage

• epiphyseal line: in adults, fusion line between epiphysis and metaphysis (growth plate)

What is the metaphysis region of a long bone?

the space between the diaphysis and epiphysis

What are the types of bone lining?

• periosteum

• endosteum

Where is the periosteum found?

layer that covers the OUTER surface of bone

Where is the endosteum found?

• a very thin layer that covers internal surface and medullary cavity

• active during bone growth

What are the types of bone marrow?

• red bone marrow

• yellow bone marrow

What is the function of red bone marrow and where is it found?

• hematopoiesis (blood cell formation)

• more widespread in children

• eventually gets replaced with yellow marrow

• in adults, in the axial skeleton and the ends of the humerus and femur

What is the function of yellow bone marrow, and where is it found?

• it’s adipose tissue

• stores triglycerides for energy

• replaced red marrow as children get older

Anemia and red/yellow bone marrow?

Anemia is a lack of red blood cells. When the body senses a decrease in RBC, the yellow marrow converts to red marrow to create more RBC (negative feed back look. When there isn’t enough RBCs, there is a decrease in oxygen in the blood.

What are the types of bone cells?

• osteoprogenitor cells

• osteoblasts

• osteocytes

• osteoclasts

What are the functions of osteoprogenitor cells?

• they are stem cells found in the periosteum and endosteum

• highly mitotic/high replication rate

• matures into osteoblasts

what are the functions of osteoblasts?

• synthesis and secretion of osteoid (semi-solid matrix of calcium and collagen)

• makes new bone during development and remodeling

• some mature to osteocytes

What are the functions of osteocytes?

• maintain bone matrix

• triggers bone formation (signals osteoblasts)

• don’t replicate

What are the functions of osteoclasts?

• reabsorb bone

• found on bone surface

• they are big phagocytic cells

• osteoclasts and osteoblasts work together to break down old bone and replace it with stronger, newer bone

What are the organic components of bone matrix?

• osteoid

• collagen, proteoglycans, glycoproteins

What are the inorganic components of bone matrix?

• salt crystals

What are the types of osteogenesis/ossification?

• intramembranous ossification

• endochondral ossification

What are the steps to intramembrane ossification?

1) ossification centers (clusters of osteoblasts) form in thickened regions of mesenchyme

2) osteoblasts make unmineralized “soup” (osteoid) that calcified

3) spongy bone and periosteum form

4) compact bone develops around spongy bone

Why does the skull rarely break?

it has a oreo-like sandwhich of compact bone and spongy bone. There is one layer of spongy bone sandwhiched between two layers of compact bone which gives it extra strength

What are the steps of endochondral ossification?

1.) fetal hyaline cartilage model of bone forms

2.) primary ossification center forms in diaphysis

3.) vascular invasion of primary center

4.) bone replaces most cartilage (officiation happens throughout childhood and into late 20s)

5.) epiphyseal plate ossifies by mid-late 20s

What is endochondral/ interstitial growth?

• lengthening bone/ growing taller

• happens at epiphyseal plate

• there is an increase in the # of chondrocytes before ossification happens

• 5 zones of ossification (Do I need to know this??)

What is appositional growth?

• increase in bone width

• in periosteum

• increase in width of medullary cavity when osteoclasts reabsorb some bone matrix after compact bone has been laid down

What is bone remodeling?

bone gets worn out with age and with use, so osteoclasts eat away the worn-out bone, while osteoblasts replace it with fresh, stronger bone.

What is parathyroid hormone (PTH) and how is it used?

PTH increases the number and activity of osteoclasts (breakdown of bone) if there is an increase in stress on the bones. Bone acts as calcium storage, so when the bone gets broken down, calcium and phosphates are released. This is used in conjunction with calcitonin in a negative feedback mechanism.

What is calcitonin and how is it used?

Calcitonin increases the number of osteoblasts (making bone) and decreases the number of osteoclasts (bone breakdown). When the body detects that there is an increase in calcium levels, calcitonin is used to decrease this by making new bone. It stops osteoclast activity and stimulates the kidneys to release the excess calcium in pee. This is used in conjunction with PTH in a negative feedback mechanism

What is calcitriol and how is it used?

Calcitriol increases the absorbance of calcium and used in conjunction with calcitonin. It increases the amount of calcium in the body.