Introduction Flashcards by Jess Escobar

The skeleton is a system that…

Supports the body
Gives size and shape
Provides muscle attachment

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The skeleton contains

Bones and joints

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Bones vs joints

Bones support structures (many sizes and shapes)
Joints are between bones and allow movement (many have synovial structures)

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Skelton biochemical functions

Provides shape and support
Uses joints to allow motion
Provides muscle leverage for mechanical advantage in movement
Protects organs (brain, thoracic, abdominal)

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Skeleton tissues are derived from…

Connective tissue

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Non-mineralized versus mineralized

Non-mineralized: lack hydroxyapatite; includes notochord and cartilage

Mineralized: have hydroxyapatite; calcified cartilage and bone

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Components of the notochord

Rod-like, axial support structure
Non-mineralized
Source of developmental signaling
In vertebrate adults, becomes nucleus pulposus in intervertebral disc
Only support system in non-vertebrate chordates

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Cartilage components

Non-mineralized

Composed of: gel matrix, collage or elastic fibers, chondrocytes

No blood supply or innervation

Flexible: stronger under compression versus tension

Easy to injure and difficult to repair (hard to get nutrients to chondrocytes and diffusion must happen through the gel matrix)

A part of growth tissue in fetus and juvenile (grows rapidly due to have both surface and intestinal growth)

In adults: ears, nose, larynx, joints

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Components of calcified cartilage

Mineralized (hydroxyapatite in gel matrix)

Unorganized microstructure (mineral added between cartilage cells)

Stronger than cartilage, but repair is more difficult due to hydroxyapatite blocking mineral diffusion

Found in shark vertebrae, horse larynx, deepest articular cartilage

Transitional tissue: toward endovhondral bone formation

Calcification can be pathogenic

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Bone is a composite tissue made of

Organic and inorganic components

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Organic components of bone

Osteoids (type 1 collage and bone matrix proteins): includes osteocalcin, 20-25% of bone weight

Cells: some derived from mesenchyme (osteocytes and osteoblasts), some derived from hematopoietic tissues (osteoclasts)

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Inorganic components of bone

Hydroxyapatite (bone is mineralized); makes up 60-70% of bone weight

Water

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Is bone active and living

Yes

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How does bone grow

Grows only at the surface, does not grow between Old bone, and grows slower than cartilage it is remodeled throughout life

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Can bone repair injuries

Yes

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Describe bone blood supply

Received 5-10% of cardiac output
Blood vessels are in the Haversian canals

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Does bone have sensory innervation

Yes

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Physiological functions of bone

Mineral reservoir, calcium homeostasis, source of blood cells, hematopoiesis in red marrow, energy source and storage (during growth, red marrow is replaced by fat, becoming yellow marrow)

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Endocrine functions of bone

Release osteocalcin: insulin regulation, bone development and function, testosterone formation and release

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Endochondral Ossification helps establish…

Hematopoietic niche

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Long bones

Cylindrical, act as levers, form from at least 3 centers of ossification (diaphysis and 2 epiphyses)

Limb bones: humerus, radius, u;mA, femur, tibia, fibula

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Short bones

No dimensión greatly exceeding others
Form from single center of ossification
Carpal and tarsal bones

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Flat bones

Expand in 2 directions
Skull bones, scapula, pelvic bones

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What can elevations, depressions, and bumps on the external surface provide

Attachment sites for various soft tissue

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Long bone proximal to distal parts

Epiphysis Growth plate/physis Diaphysis Metaphysis (contains physis) Epiphysis

Diaphysis

Shaft of the bone

Physis

Growth plate Cartilaginous Present while bone is growing

Metaphysis

Contains the growth plate

Epiphysis

Important for stabilizing joints during growth

Compact bone

Structural and dense

Trabecular bone

Spongy and flexible

Medullary cavity

Marrow where blood is formed

Periosteum

On outer surface of bone Living tissue helping build and maintain bones Fibrous outer layer (fibers, elastin, vessels, nerves) Inner osteogenic cell layer

Endosteum

Thin membrane lining marrow cavity Living tissue, helps build and maintain bones

Is bone strong and resilient? Is it strong under compression, even more than concrete and granite?

Yes

Lacunae is occupied by

Osteocytes (bone cells)

Where are osteocytes located

Situated,between lamellar forming concentric bone structures surrounding Haversian canals

What connects adjacent osteocytes

Canaliculi

Mechanoreceptive system is formed by what cells

Osteocytes

Osteons make up

Haversian systems

Osteons are made of ….. and surround ……

Made up of Haversian canals and surround circular lamellae

Haversian systems/Osteons contain …… and …… in compact bone

Vessels and nerves

A large nutrient artery enters the …….. ……… in diaphysis

Nutrient foramen

Smaller vessels supply what bones parts

Metaphysis and epiphysis

Capillaries from …… and …… enter bone

Periosteum and endosteum

Since there are arteries in bones, there are also 3 other things:

Veins, lymphatics, and nerves

Growth p;ate affects how ……. Moves through bone

Blood

Do blood vessels cross physis

No, there is a separate blood supply for growth

Once the physis is closed off during growth, what happens

Epiphyseal artery and main nutrient artery meet up

How does endochondral bone grow

Endochondral ossification

What is the precursor of Endochondral bone

Cartilage precursor

What do Endochondral bones form

Mesenchyme

Ossification begins in utero, meaning:

First in diaphysis, later in epiphysis

2 ways bone is added to the diaphysis

1. Replacement of cartilage 2. Conversion of perichondrium to periosteum

All Endochondral ossification-derived bones have periosteal bone that forms concomitantly via

Intramembranous ossification

Where is Endochondral bone found

Axial skeleton, limb skeleton, ventral braincase

How does dermal bone grow

Intramembranous ossification

Is there a cartilage precursor in dermal bone growth

Where does trabeculae form

Directly in membrane

For dermal bone growth, bones grow…

Outward (growth zone is at the edge of developing bone at suture)

Example of membrane bone

Thin flat bones of skull roof derived from neural crest cells

What is a sesamoid bone

Bones that form within the tendons

Functions of sesamoid bone

Prevents muscle from deforming as it flexes or extends Helps improve muscle leverage (patella helps strengthen knee stifle extension)

Ligaments

Bundles of connective tissue fibers Connect bones at joints Permit motion but also limit motion

Joint capsules

Found at synovial joints

Synovial joints include

Synovial fluid Synovial membrane Fibrous outer layer Capsular ligaments

Meniscus

Cartilage spacer or pad for femur to sit on

Bursa

Protective cushions between bones and tissues Have synovial membrane and fluid Distinct from joint capsules: NOT between bones

Three types of joints

Synovial, fibrous, cartilaginous

Synovial joints are the most …… joints

Mobile

Synovial joints are lubricated by

Synovial fluid, allowing smooth motion

Amount of motion at a joint is restricted by ….

Ligaments

Flat joints

Slide

Barrel-shaped joints (hinge)

Flex and extend

Pivot joints

Allow bone to pivot on long axis (like shaking head)

Ball and socket joints

Allow flexión and extension, abduct and adduct, pivot, and circumduct

Flexion

Reduces the angle of a joint (bending elbow or arching over)

Extension

Increases the angle of a joint (straightening elbow or stretching back)

Pronation

Internal rotation (turning your palm toward the floor)

Supination

External rotation (turning your palm to face upward)

Abduction

Movement away from the midline (spreading fingers or limbs apart)

Adduction

Movement toward the midline (bringing fingers or limbs together)

Overextension

Extension past 180 degrees (horse fetlock bending backward)

Circumduction

Movement along a conical surface (hips and shoulders)

Fibrous joints allow limited motion and are connected by

Connective tissue (NOT SYNOVIAL FLUID)

3 types of fibrous joints

Sutures, syndesmoses, gomphosis

Sutures

Connect membrane bones to each other (bones in the skull roof)

Syndesmoses

Connect Endochondral bones to each other (between ulna/radius and tibia/fibula)

Gomphosis

Connection between a tooth and jaw

Cartilaginous bones are the least

Mobile

Synchondrosis

Connected by cartilage Growth plates in young animals Joints between skull and hyoid or ribs and sternum Cartilaginous joint

Symphysis

Multiple tissues Forms a complex sandwich that connects the bones Bone—cartilage—CT—cartilage—Bone Pelvic, intervertebral, and mandibular symphyses