Chapter 6- The Skeletal System

Exam- 10/2/2023

What are the 7 functions of the skeletal system?

1. support

2. Protection

3. Movement

4. Mineral and growth factor storage

5. Hematopoesis

6. Triglyceride storage

7. Hormone production

What hormones/minerals does the skeletal system store? (3)

1. Calcium

2. Thyroid hormone

3. Growth hormone

Why must RBC production take place in the skeletal system?

• RBC only live for 120 days so they need to replace themselves

• RBC have no nucleus so they can’t perform mitosis by themselves

Why do children need more RBCs than adults?

because they are growing everyday and have more tissue every day than the day before; adults have a baseline amount because they stop growing and even if tissues regenerate they will be same size as prior

What does triglyceride mean? What color marrow stores it?

Fat; yellow

What population is yellow bone marrow found in ?

Adults; b/c they don’t need as much red marrow

Why must the skeletal system produce hormones?

because bones are living organs, and because they are created using calcium and calcium comes from the diet they must be able to communicate with the rest of the body to know how much calcium is available in the blood stream

How are bones classified?

By shape

What are the 4 types of bone structure?

1. Short bones

2. Flat bones

3. Irregular bones

4. Long bones

what are short bones?

Only as tall as they are wide

What are flat bones?

One side of the bone is very narrow (ex. Sternum)

What are irregular bones?

Combination of short and flat bone characteristics (ex. Thoracic vertebrae)

What are long bones?

Longer than it is wide and has a circular, central shaft

What is a diaphysis?

Central shaft

What is the sandwich model?

Compact bone- bread

Spongy bone - meat

Compact bone -bread

What kinds of bones utilize the sandwich model? (3)

1. Short

2. Flat

3. Irregular

What is trabeculae?

Structural unit of spongy bone

Where is marrow found in long bones?

In the gaps of trabeculae

What is an osteon?

Main structural unit of compact bone

What is a diaphysis? What kind of bone is it found in?

The middle; long bone

What is a proximal epiphysis? What kind of bone is it found in?

On top of long bone

What is a distal epiphysis? What kind of bone is it found in?

On bottom of long bone

What kinds of bone make up a long bone? Where is e

What is found in medullary cavity?

Marrow

When is an epiphyseal line visible? What kind of bone is it found in?

Only when the bone is fully grown and calcified ; long bone

Where is an epiphyseal plate located? What is it made of? Why? Another name? What kind of bone is it found in?

• same location of line

• made of cartilage

• b/c bone is not fully ossified

• AKA growth plate

• Long bone

Why are bones highly vascular?

B/c bones are made of living cells and tissues

What is a periosteum? What kind of bone is it found in?

perimeter + bone + membrane- surrounding membrane of long bone

What is a endosteum? What kind of bone is it found in?

inside + bone + membrane- membrane surrounding inside of long bone

What is the osteon’s central canal responsible for?

Transport of blood and nerve signals

What is a lacuna? What kind of bone is it found in?

Divits in an osteon that hold a living cell; long bone

What is a lamella? What kind of bone is it found in?

layer of an osteon (creates ring structure that makes it look like a tree); long bone

What is a canaliculi? What kind of bone is it found in?

little canals that allow cells to communicate from lacuna to lacuna; Long bone

What is an interstitial lamella? What kind of bone is it found in?

in between tissues + layers= in between area of osteons; long bone

What does the circumferential lamella do? What kind of bone is it found in?

makes bone appear solid, lamella surrounding the diaphysis; long bone

What are the 2 types of bone components?

1. Organic compounds

2. Inorganic compounds

What is an osteoid?

Group of organic compounds that are produced by bone cells that create bony matrix

What is an osteoid made of?

Made of carbon based substance; has hydrogen and oxygen; proteins, ions, nutrients

What cell secretes osteoid?

Osteoblasts

What does the secreted osteoid cause?

a set of chemical reactions that will ossify the matrix into bone

What is hydroxyapatite? How much of the bone mass is made up by it? What is it made of?

Hard, dense, mineralized structure ; makes up more than 65% of bone mass; made of Ca2+ and PO4

What does hydroxyapatite do for the bone?

Helps it withstand compression forces

What are the different types of cells found in the skeletal system? (4) Which 3 are related to one another?

• osteogenic cells

• Osteoblasts

• Osteocytes

• Osteoclasts

All related

What are osteogenic cells? Where are they located? What do they do for the body?

• Stem cells (a cell that hasn’t differentiated yet)

• located in bone area

• Undergo mitosis quickly and frequently which allows them to become many different cells during mitosis; daughter cell gets different signal that makes osteoblasts

What does osteoblast mean? What is the function of osteoblasts? Can they undergo mitosis? What do they become? Why?

• bone + creator

• creates bone, secretes osteoid- bony matrix (fluid, oily substance)

• also mitotically active

• chemical reactions would crush and kill it if not for the transformation into osteocytes

What are osteocytes? What are they made of? What do they do?

• mature bone cell

• made of previously osteoblast cells

• changes shape and function a bit to communicate with other osteocytes and monitors and maintains the mineralized bone matrix

What are osteoclasts? What does it do? How many nuclei? Why? What does the edge look like? Why?

• bone-resorbing cell

• do opposite functions of osteoblasts; spelling matters here!!!

• multiple nuclei to produce many proteins b/c it needs to break down everything osteoblasts and osteocytes make

• fringey edge to attach to bone to start dissolving it

What helps the bone to withstand torsion force? How?

sacrificial bonds that are present in collagen molecule of bone (picture from txtbk of lamallae cut so you can see all layers); opposing directions of collagen allow it to withstand force from different directions

How do bones withstand forces?

absorb as much as you can by arrangement, if exceeded collagen fibers break preferentially so that bone is not harmed

True or false?

Our skeleton is the same from birth to death.

False- bones are not static, they are living organs- we must keep them fresh

What does remodeling do?

have structure but remodeling fixes it and makes it better

How much of bone mass is recycled weekly? When is all of your spongy/compact bone replaced?

• 5-7% of bone mass recycled weekly

• Replace spongy bone every 3-4 years

• Replace compact bone every 10 years (harder to rebuild than spongy bone)

How is bone remodeling executed?

balance of resorption and deposit of boney matrix

(Patterned and necessity to this process)

What are the 2 steps of bone remodeling?

1. Deposit of new boney matrix

2. Resorption

How does the body deposit boney matrix? (2)

1. Osteoblasts secrete osteoid

   A. local Ca2+ and Pi present in correct amount to ossify the osteoid secreted by the osteoblast

   B. proteins in organic matrix find the Ca2+ and Pi and bind to it and concentrate Ca2+ in the area

2. Alklaline Phosphatase causes mineralization (enzyme)

   A. Sudden (just this step occurs suddenly)

What does mineralization mean? What does it create?

• simultaneous deposition of calcium salts (crystalline structure and arrangement)

• hard boney matrix

How does resorption of boney matrix occur? (5 or 8 steps depending on how its stated)

1. osteoclasts forms depression/groove in surface where we need to break down bone

2. Lysosomal enzymes convert calcium salt into soluble form

3. Matrix, growth factors, & materials are brought into the cell through endocytosis

4. Transported across the osteoclast in a vesicle

5. And then secreted outside the other side of the cell (exocytosis)

^^ those 3 are transcytosis

6. calcium now in interstitial fluid

7. Diffused into bloodstream

8. Osteoclast undergoes apoptosis (after doing this process a few times) to save body from lysosomal contents

what is a resorption bay?

depression/groove that osteoclasts attach and create a suction to control lysosomal contents so that it only breaks down what is intended

What are some functions of calcium that make it so important to the human body?

• transmission of nerve impulses- neurons communicating with other neurons or cells (essential for function of nervous system)

• Muscle contraction- needed for this to occur

• Blood coagulation- blood clotting: 3-4 step process that requires calcium at at least 1 step

• Glandular secretion- relies on calcium signaling to secrete substances

• Cell division - mitosis requires calcium, if no calcium mitosis stops

How is the deposit and resorption of matrix controlled?

A negative feedback loop

What are the steps of the deposition and resorption of matrix control? (5)

1. Stimulus- Falling blood Ca2+ levels —> causes imbalance —> initiates feedback loop

2. Parathyroid glands release parathyroid hormone (PTH)

3. Increased levels of PTH in the bloodstream

4. Osteoclasts degrade bone matrix and release Ca2+ into the blood

5. Repeat; if imbalance is still there

What is Wolff’s law? Give an example

• bone grows or remodels according to mechanical demands placed upon it; a bone’s anatomy reflects the stresses placed upon it

• ex. Weightlifters have denser bones b/c they are constantly picking up heavier weights and have more mechanical forces on their bones and need to be denser to withstand it

Structure-function complementarity but make it ✨bones✨