Biology Terms for PNB Exam #2: Key Definitions & Concepts

5 functions of the skeleton system

- support

- protection

- allow movement / lever system

- storage deposit for Calcium & Phosphate

- hematopoiesis

How do muscles and bones move

- muscles form a lever system with 2 different points of a bone

- when it contracts it forms a pully which moves the bone

Hematopoiesis

formation of blood cells

hemopoietic stem cells

Cells found in the bone marrow that produce the cellular components (ex: RBC, WBC)

what 7 cells do hematopoietic stem cells differentiate to

hematopoietic stem cell -> myeloid stem cell -> proerythroblast -> basophilic erythroblast -> orthochromatic erythroblast (nucleolus ejection) -> reticulocyte -> mature erythrocyte

5 classes of bones

- long bones

- short bones

- flat bones

- irregular bones

- sesamoid bones

Long bones

longer than they are wide

(ex: femur, humerus)

Short bones

square shape - as wide as they are long

(ex: wrist (carpals) and ankle (tarsals))

Flat bones

not perfectly flat but flatter than they are round

(ex: bones around the brain)

Irregular bones

hard to describe

(ex: vertebrae)

Sesamoid bones

classified on how they form (form inside a tendon)

- typically, only one in the body (patella)

Where do some people have an additional sesamoid bone?

in the elbow (rare)

4 gross structures of a long bone

- diaphysis

- metaphysis

- epiphysis

- marrow cavity

Different names for red marrow and yellow marrow

red = active

yellow = inactive

What is in the center of the diaphysis

medullary cavity (marrow cavity)

What is the medullary cavity filled with

yellow bone marrow (fat reservoir)

Where can red bone marrow be found

- in the epiphysis

- hollow bubbles of spongey bone filled with RBM

Where are hemopoietic stem cells found

red bone marrow

What do compact bone contain

- osteons with concentric layers of lamellae with a central canal in the middle with vessels and nerves

What does Spongey bone contain

- lattice like network of trabeculae

Why is trabeculae important in bones

- lightens their weight

Periosteum (and 2 layers)

- wraps around the outside of the long bone

(fibrous layer and cellular layer)

Fibrous later of periosteum

very outside (most superficial)

- consists of dense irregular connective tissue which weaves around and provides framework

- helps weave bones into tendons that attach to muscles or ligaments

Cellular layer of periosteum

contains cells that can deposit calcium salts or take them away depending on needs

Endosteum

- inside the medullary cavity

- similar to cellular layer of periosteum

- active layer with osteoblasts and osteoclasts

Metaphysis has either ___ or _____

- epiphyseal plate

-epiphyseal line

epiphyseal plate

growth plate (where bone formation occurs)

what happens to the epiphyseal line as a person gets older

by age of 25 the plate will go away and leave a line

why does the X ray of children give the impression of extra bones

- there are breaks in the bone from the growth plate

- in adult it looks like a continuous 1 bone

what layer of cartilage is found outside of the epiphysis and what is its function

- layer of hyaline cartilage (articular cartilage)

- lines the location of articulation where bones meet to form a joint

- needed for cushion and reducing friction between bones

bone is ___ tissue which means it is ______

- dynamic, always changing

bones are vascular, but how vascular?

VERY VASCULARIZED

What is found in the middle of osteons

- central canals

- tiny blood vessels perforating from it

what are central canals supplied by

volkmann canals that enter via periosteum perpendicularly, then run up and down

what is the fetal skeleton initially formed by

connective tissue called mesenchyme

(also contains hyaline cartilage)

what is mesenchyme

very vascular connective tissue and large amount of collagen fibers for structure

Intramembranous ossification

bone forms from mesenchyme

where does intramembranous ossification mostly occur

in flat bones

what is osteoid

early formation of bones

- not hard and not calcified

process of intramembranous ossification

1) mesenchymal cells differentiate into osteoprogenitor cells which become osteoblasts

2)osteoblasts lay down osteoid

3) calcium salts are added to osteoid to begin hardening process

4) a few osteoid will get trapped in new calcified matrix (lacunae) and then mature into osteocytes

5) the non-trapped osteoblasts will continue around the perimeter and lay down osteoid

6) bone forms around the blood vessels to create spongey bone

7) remodeling areas that need compact bone - fill in extra space

where can intramembranous ossification happen after birth

in the skull

fontanels

large area of dense connective tissue

- gap in babies' skull

why aren't babies skulls fused at birth

- gaps create flexibility during birth and growth

when do fontanelles undergo ossification completely

- before 2 years of age and form sutures

sutures

special type of joints between bones of the skull

endochondral ossification

bones replace hyaline cartilage

- forms most bones of the body

6 steps of endochondral ossification

1) fetal hyaline model develops

2) cartilage calcifies & a periosteal bone collar forms around the diaphysis

3) primary ossification center forms in the diaphysis

4) secondary ossification centers form in epiphysis

5) bone replaces cartilage, except the articular cartilage and epiphyseal plate

6) epiphyseal plate ossifies and forms epiphyseal lines

what is the outside layer of fetal hyaline cartilage

perichondrium

step 2 of endochondral ossification in detail

- chondrocytes mature & enlarge then die which leaves spaces within cartilage matrix

- perichondrium is replaced by bone through the process of blood vessel formation & osteoprogenitor cells maturing into osteoblasts which lays down bone on the outside

step 3 of endochondral ossification in detail

- blood vessels continue to invade the diaphysis filling in the spaces where chondrocytes created spaces

- osteoprogenitor cells come in and lay down osteoid

step 4 of endochondral ossification in detail

- secondary ossification center forms when blood vessels invade on either end

- remodeling of diaphysis sponge bone that's formed around the edges -> compact bone forms

step 5 of endochondral ossification in detail

babies to teens have spongey ends that never get remodeled

step 6 of endochondral ossification in detail

- bone in a person's 20s

- plate becomes line

- bone is set in length

as long as hyaline cartilage remains at the epiphyseal plate ...

the long bone is capable of increasing in length

bone growth in length (simplified)

- cartilage proliferation on epiphyseal side of epiphyseal plate

- ossification occurs on the diaphyseal side of epiphyseal plate

- process continues until chondrocytes stop proliferating and the entire growth plate ossifies

5 zones of epiphyseal plate

1) resting cartilage

2) proliferating cartilage

3) hypertrophic cartilage

4) calcified cartilage

5) zone of ossification

appositional growth is growth in ...

width

- increase in width of bone

appositional growth

adding layers (& remodeling marrow cavities)

- compact bone thickens & strengthens long bone with layers of circumferential lamellae

ex: weight trainors gain stronger bones

steps of appositional growth

- osteoblasts in cellular layer of periosteum lay down calcium and create osteoid that calcifies

- osteoclasts in the endosteum are going to resorb some of the calcified bone matrix

- creates wider medullary cavity (lighter but bigger/stronger)

bone remodeling occurs when ...

occurs in response to changes in demand on bones (force or load)

ex: weight training / prolonged bed rest

Wolff's law

bones remodel in response to compressive force

(ex: can be seen in astronauts as they lose bone density rapidly as spongey bone loses its strucutre)

can bones grow in width throughout life

yes

what happens if calcium plasma level is too high

- thyroid gland releases calcitonin

- calcitonin stimulates calcium and salt uptake and bone deposition

- back to normal calcium concentration range

what happens if calcium plasma is too low

- parathyroid gland releases PTH

- PTH stimulates osteoclast activity and resorption of calcium by kidneys & intestine

- back to normal calcium concentration range

PTH causes ___ in blood calcium

Calcitonin causes ___ in blood calcium

- increase

- decrease

is calcium just used in bones

- not it is also vital for other systems

ex: muscles need for contractions

bones are _____ reservoir that can be _______

- calcium reservoir

- used in times of low calcium availability

(calcium here can be stored and used for later)

what are the two hormones used for regulating calcium through negative feedback looks

- PTH and calcitonin

Do PTH and calcitonin use a positive or negative feedback loop

negative feedback loop

Osteoporosis

- less bone density overall

- as we get older osteoclast activity outpaces osteoblast activity

with osteoporosis the inorganic/organic ratio in matrix is

normal

what can osteoperosis cause

kyphosis

what is kyphosis and what can it cause

compression fractures in vertebrae

- exaggerated curvature of the spine

can cause decrease in lung capacity (not breathing as much air as efficiently)

- can cause a decrease in optimal circulation and compresses nerves

osteoporosis is common in ..

- post menopausal women due to their lack of estrogen

- in ovulating females estrogen is secreted in higher amounts

why is estrogen important to bones

it contributes to the regulation of bone metabolism

what happens in a bad case of osteoporosis

weight of body can cause compressive fractures within vertebrae

- tiny fractures can be painful

- causes shrinkage and change in posture (kyphosis)

does kyphosis only occur cause of osteoporosis

no it can occur due to other reasons

bone repair 3 simple steps

fracture:

1) hematoma

2) soft callus

3) remodeling

step 1 of bone repair

Hematoma

- when bones fracture blood vessels burst

- 1st we need to contain the blood and form a blood clot/ hematoma

step 2 of bone repair

soft callus

- cells from endosteum will start to form from fibrocartilage around the break aka internal soft callus

- simultaneously will have cells from the periosteum forming a hyaline cartilage callus around the bone (looks like a lump)

step 3 of bone repair

remodeling

- osteoclasts are going to start to resorb the dead fragments and osteoblasts are going to start remodeling the two calluses into bony calluses

- get spongey bone in the appropriate places and compact in the more superficial part

8 types of fractures

- closed

- open

- transverse

- spiral

- comminuted

- impacted

- greenstick

- oblique

closed fracture

break contained within the skin

open fracture

- compound

-bone breaks through the skin -> much higher risk of infection

greenstick fracture

bone doesn't break through all the way

- happens in children because bones aren't fully ossified and have more spongey bone than adults

(called because breaking a living stick doesn't break it all the way and just cracks)

what is an articulation

joint - site where two or more bones meet

ex: should joint connects humorous and scapula

range of motion

(ROM) normal extent of mobility for a specific joint movement

ex: ROM for wrist flexion is 70-80 degree and extension is 65-80 degrees

degrees of freedom

(DOF) the number of axes at which movement of a joint occurs

ex: wrist is biaxial with 2 DOF, which means 2 planes of motion (can move side to side and back and forth)

does every human have the same ROM and DOF?

- ROM has a healthy range while DOF should be the same for everyone

mobility comes at the cost of ...

stability

the type of connections of bones in a joint .....

determine the function of that joint

mobility and stability have an ...

inverse relationship

main issue with being more mobile

less stability = more prone to injury

order these from most stable to least stable:

- hip joint, intervertebral joints, sutures, shoulder joint, elbow joint

- sutures

- intervertebral joints

- elbow joint

- hip joint

- shoulder joint

what is an important factor about stable joints

- provide protection

ex: joints in the skull (sutures) have limited mobility but are super stable and protect the brain from injury

ball and socket are mobile because

- not a lot of contact between bones

- connected by ligaments instead which allows for much more movement but less stability

3 joint classification by structure

what is between bones

- fibrous

- cartilaginous

- synovial

3 joint classifications by function

how movable they are

- synarthrosis

- amphiarthrosis

- diarthrosis

synarthrosis

immovable (ex: skull)

amphiarthritis

slightly movable (ex: public synthesis)