A&P The Skeletal System

What is the study of the skeletal system called?

Osteology

Are bones organs?

Yes

Bones are made of what 3 things?

Bone tissue, Cartilage, & Dense (collagenous) CT

The Skeletal System is made of what 3 things?

Bones + Cartilage + Ligaments

Bundles of dense regular CT that connect to bone are called...

Ligaments!

How many bones do adults have?

206

How many bones do babies have?

270

What are the 3 parts of the axial skeleton?

-Skull
-Vertebral Column
-Sternum & Rib Cage

What are the 4 parts of the appendicular skeleton?

-Shoulder girdle
-Upper appendages
-Pelvic girdle
-Lower appendages

What are the 6 main bone functions?

-Support
-Protection
-Movement
-Electrolyte balance
-Acid-Base balance
-Blood cell production in red bone marrow

The bone matrix is made of...

Calcium Phosphate (Hydroxyapatite) and other minerals which form crystals around collagen fibers

What protein provides tensile strength?

Collagen

Is bone vascular?

Yes (bones can bleed)

Osseous Tissue is...

Bone tissue

Osteogenic cells are...

Mesenchymal stem cells

Osteogenic cells turn into...

Osteoblasts

Osteogenic cells multiply by...

Mitosis

Osteoblasts _______ bone

Build

Osteoblasts become...

Osteocytes

Osteocytes are found in cavities called...

Lacunae

Small channels that connect lacunae are called...

Canaliculi

What do the canaliculi do?

Connect the osteocytes in the lacunae to each other & connect to the blood supply

Osteoclasts _______ bone

Dissolve

Living bone is constantly being ________

Remodeled

Hydroxyapatite is...

Calcium Phosphate

Trabeculae and red marrow are found in...

Spongy bone

Does spongy bone have osteons?

No

Trabeculae are...

Interconnected strips found in spongy bone

What are Osteons?

Dense cylinders that strengthen COMPACT bone

Spongy bone has strength with ___________ weight

Reduced

Which of these does spongy bone not have?
a) Lacunae
b) Osteocytes
c) Osteons
d) Canaliculi

c) Osteons

Does normal stress over time make bone stronger?

Yes

Compact bone have great _______ strength

Vertical

What are the basic functional units of compact bone?

Osteons

The osteon cylinders run parallel to the ______ axis of bone

long (they're up and down)

The Central Canal is located...

In the center (middle) of the osteon

What does the Central Canal contain?

Blood vessels and nerves

What surround the Central Canal?

Concentric Lamellae (layers)

Concentric means...

One inside the other

Lamellae means...

Layers

Perforating Canals run...

Perpendicular (side to side)

Perforating Canals involve...

The passage of blood vessels, lymphatic vessels, and nerves that run between the Periosteum and the deeper parts in the bone

Rings of bone surrounding a central canal are...

Concentric Lamellae (remember concentric lamellae just means layers wrapping around each other)

What are the 2 types of lamellae?

Circumferential & Interstitial

What type of lamellae is located between osteons and has remnants of broken down osteons?

Interstitial

What type of lamellae is located right underneath the periosteum and encircles the bone's circumference?

Circumferential

The periosteum has ___ layers

2

The OUTER layer of the periosteum is made of...

Fibrous Collagen

The INNER layer of the periosteum is...

Osteogenic

The periosteum covers...

The entire bone surface except the articulating surfaces

True or false: The periosteum is involved in bone growth and repair

True

Does the periosteum have blood vessels and nerves?

Yes

Ligaments connect _______ to _______

Bone to bone

Tendons connect _______ to _______

Muscle to bone

The Endosteum is an incomplete, thin layer of....

Reticular tissue

What lines the medullary (marrow) cavity?

the Endosteum

How many bone shapes?

6

What are the 3 main parts of long bone structure?

-Proximal Epiphysis
-Diaphysis
-Distal Epiphysis

Both Epiphysis's (ends) of long bone have...

Articular cartilage

Which end of the long bone has red bone marrow?

The Proximal Epiphysis

What is in the diaphysis (middle) of long bone?

The shaft and medullary (marrow) cavity with YELLOW bone marrow

What is between the Periosteum and Endosteum of long bone?

The Bony Collar

At the center of long bone there is a...

Medullary Cavity

The bony collar is made of mostly...

Compact bone

The structure of flat bone looks like a...

Sandwich

Compact bone sandwiching spongy bone is found in...

Flat bones

The spongy bone with red marrow is called...

Diploe

Cranial bones are usually what bone shape?

Flat

"Intramembranous" means...

Within/between membranes

Ossification means...

Bone formation

Intramembranous Ossification means

The forming of spongy bone filled with marrow between compact bone

Intramembranous Ossification occurs in...

Flat bones
Mandible
Bone that replaces baby fontanels

The 2 types of Ossification are...

Intramembranous & Endochondral

Ossification begins during the _____ or _____ week of embryonic development

6th or 7th

Endochondral Ossification is when...

Cartilage is replaced by bone

Endochondral Ossification forms ______ ____ the skeleton

Most of

True or False: Cartilage becomes bone

False; Cartilage is REPLACED by bone

There are 6 steps of ______________ Ossification

Endochondral

What happens in step 1 of Endochondral Ossification?

The origin of most bones as Hyaline Cartilage

Ossification begins in step ___ of Endochondral Ossification

2

What happens in Step 2 of Endochondral Ossification?

Perichondrium becomes periosteum & bony collar forms

What 4 things happen in Step 3 of Endochondral Ossification?

-Blood vessels grow into cartilage
-Cartilage calcifies and dies
-Medullary (marrow) cavity forms
-Proximal epiphysis forms

What happens in Step 4 of Endochondral Ossification?

-The Medullary (marrow) cavity enlarges
-The distal epiphysis forms

What happens in Step 5 of Endochondral Ossification?

Bones continue to grow at the Epiphyseal plate

What happens in Step 6 of Endochondral Ossification?

Bones stop growing and the Epiphysial plate closes, leaving an Epiphyseal line

Within the Epiphyseal Plate, bone grows from _________ to _____

Bottom to top

Around what age does the Epiphyseal plate stop growing?

Ages 18-20

Growth in width is...

Appositional Growth

During appositional growth, layers are added to the...

Bony collar

What specifically happens in appositional growth?

Periosteal blood vessels lie inside bony ridges and eventually the ridges fold around the vessels (like a burrito)

During appositional growth, new _______ are formed and the __________ _______ enlarges

Osteons; Medullary Cavity

Do bones have homeostasis?

Yes

Bone homeostasis occurs in response to:

-Physical Activity
-Age
-Nutrition

Bone remodeling allows for...

-Healing after fractures
-Changes in response to mechanical stress
-Acid-base balance
-Maintenance of blood calcium & phosphorus

During bone remodeling, ________ _______ are continually removed and replaced

Calcium salts

The pull of _______ and _______ are important for bone health

Muscles and gravity

Lack of mechanical stress leads to...

Bone atrophy

Weight bearing exercises stimulate...

Bone growth & retention of bone mass

True or False: Exercising at ANY age is beneficial

True!

About what percentage of our calcium is in our bones?

99%