skeletal system

How many bones do humans have?

Adults - 206

Kids - 300

What are the several roles of the skeleton?

• Protect organs

• Provide shape

• Aid in movement (with muscle)

• produce red and white blood cells

• maintains homeostasis of stored minerals like calcium

What are the different categories in bones?

Axial - centre, skull, spine (vertebrae), ribs (thoracic rib cage + sternum)

Appendicular - limbs, shoulder girdle and hip girdle

long

flat

irregular bone

sesamoid bone

In depth, what makes up the axial skeleton?

skull = cranium + facial bones

Hyoid = swallow +holds tongue

Ribs + sternum =. 25 bones

Spine = 33 vertebrae

what is the thorax?

between neck and above abdomen

What are the 4 areas in the axial? (based on location)

Cervical

Thoracic

Lumbar

Sacral

How many bones are in the axial skeleton?

80

What makes up the appendicular skeleton?

The shoulder girdle - Scapula (shoulder blade) + Cavicle (collar bone)

The Pelvic girdle - Hip, Sacrum, Coccyx

What are the three different types of bone (describing internal texture)?

Cancellous

Woven

Compact

Describe cancellous bone

Honeycomb-spongy texture

Usually found at the end of long bone

Describe woven bone

irregular arrangement of collagen

Describe compact bone

Dense outer shell of bones

What type of cells in the bone marrow are responsible for RBC and WBC production

The bone marrow contains hematopoietic stem cells which differentiate into red and white blood cells

The bone marrow is responsible for __% of RBC production

100%

The bone marrow is responsible for __% of WBC production

70%, the rest is made in the lymph system

What is the lifespan of RBC?

120 days, approx 1% of rbc replaced per day

What is the lifespan of WBC?

A few hours, approx 1.5 billion per day

What is the majority of bone composition? aka what is it made from?

Calcium and Phosphorus

is 65% of bone composition

The skeleton is the bodies largest storage of minerals

What are calcium and phosphorus used for?

Nerve conduction

Muscle contraction - link why granny needs strength training, more ca means need increase bone density to store it, less likely to break

Hormone regulation - link why exercise is good for mood, more minerals absorbed that aid mood

What are the three main bone cells?

Osteocytes

Osteoblasts

Osteoclasts

What is the role of osteoclasts?

To break down old and damaged bone, this makes space for new bone to be made by osteo___

it does this by releasing enzymes, the nutrients are then releabsorbed into the bloodstream

resorption

What is the role of osteoblasts?

to grow new bone

to heal damaged bone

to reshape bone as you age

builds extracellular matrix

What is an osteocyte?

A bone cell that monitors bone strength and signals to osteoblasts and osteoclasts when to work

They used to be osteoblasts, they been promoted over time

What is woven bone

rapidly formed bone which is weaker and usually replaced by lamellar bone by age 4

Used in: babies, kids, fractured healing

What are the three different types of joints?

Fibrous

Synovial

Cartilaginous

Name where we would find the three different types of joints:

Synovial - between a bone and a ligament/muscle (this one enables movement fr)

Fibrous - in your skull (this is dense and does not aloud movement)

Cartilaginous - Between the vertebrae in your spine, or between your ribs and your sternum (this one allows a little movement) (crucial to inhale and exhale, or full range of spinal movement)

Describe a fibrous joint?

a dense connective joint that prevents movement

What is lamellar bone?

Mature, highly organised strong bone -

A - Cortical Compact (dense outer layer, makes up 80% of skeleton)

B - Cancellous (described as trabecular or spongy, porous and lightweight, makes up 20% of skeleton, in joints to absorb impact)

What is hematopoiesis?

The process of producing new blood cells, continuously

What are some examples of joint names (that describe movement)?

Ball and socket - full range of movement e.g. shoulder

glide - slides past, slight movement, back of hand

hinge - limit to flex and extend e.g. elbow

pivot - elbow

saddle

candyloid - limit to flex and extend e.g. fingers

What is a ligament?

Dense connective tissues fibres made from collagen

bone x bone

allows limited movement

Has good blood supply, nerve supply and ability to heal

provides proprioceptive input

What is proprioceptive input?

Proprioceptive input is baso your bodies internal ability to sense position and movement, it helps your regulate how much force to use when completing an activity, baso coordination but without eyes

point is to to enhance movement and minimse injury

describe cartilage?

Highly specialised tissue made up of high water contents, glossy look

No specific nerve or blood supply x no ability to heal

2 types: hyaline and fibro

Hyaline cartilafge:

Smooths movement, reduce friction, protects joint surfaces, strong

Fibro cartilage:

Shock absorber - spongy, strong

Describe a tendon

Muscle x bone

Contains Golgi-Tendon Organs (GTO) which monitor the amount of force being used in the muscle, this way it can grow proportionately to the muscle to prevent microtears and injury (like if the muscle was way bigger than the tendon)

Contains collagen

limited blood supply, limited healing abilities

What is the level of strength in a bone attributed to?

80% of it is density aka how much calcium and phosphorus

20% is its architectural structure

so baso how many layers, and how it was built infrastructure

What is the relationship between physical activity and bone density?

Strong relationship between exercise and bone mass

Skeleton responds in a site- specific manner to mechanical loading i.e. density ­ in areas where there is greater loading or stress

What is the significance of exercise in relation to bone density in adolescence and childhood

Adolescence/childhood = when bone is actively being built and shaped (osteoblast/clast/cyte at work fr) so exercise at this point in time = more efficient building bone density = reduce likelihood of develop osteoporasis when older

What is Wolff’s Law?

The bones ability to grow, change shape and size due to mechanical demands placed on it

How long does bone remodelling/wolffs law take?

4-8 Months

it is a cyclical process

Define Resorption

The breakdown of bone via osteoclasts releasing enzymes

Releasing minerals e.g. calcium into blood stream

Problem occurs when rate of resorption out does rate of

can be caused by lack of estrogen (post menopause) - effects women more

Lack of exercise

10 days

Describe Bone Matrix Formation:

Osteoblasts secrete organic compounds mainly collagen (90%) which will interact with calcium and phosphorus to rebuild structure

10-20 days

Describe Mineralisation

the depositing of calcium and phosphor into this structure

3-4 months

Describe osteoporosis (in physical stature)

Reduced compact bone

Bigger pores in cancellous bone

Weaker cancellous bone, less minerals (last 2 called pathological)

What age groups may be more at risk of osteoporosis?

Women over 65 (menopause, lack of estrogen, loop of hormone regulation)

Men over 75 (men have more muscle, hence less likely, 1 in. 5 men v 1 in 3 women)

What lifestyle choices may increase risk of developing osteoporosis?

• people with eating disorders (lack of calcium and vit D intake through food)

• People with long term chronic conditions intake steroids

• Smokers/Alcoholics long term

• People w less physical activity

What percent of people with osteoporatic hip fractures will fully recover?

30%

Describe the structure of a bone from joint to joint

Hyaline cartilage - on edge of bone/at joint, protection

Epiphysis - rounder section at end of bones (x2) more cancellous

Diaphysis - Long section (shaft), mainly compact bone

Medullary canal - contains fatty yellow bone marrow aka rbc/wbc prod.

Nutrient artery - supplies the bone shaft, also where nerves are

Describe the periosteum

Membrane of blood vessels and nerves that surrounds bone

This outer shell of the bone

Containing nerve endings and blood supply

It’s job is to supply the bone with blood/nutrients

Where sense of feeling derives from

Also why pain from fractures is so painful

Role: heal fractured bones, it has osteoprogenitors which create osteoblasts

They are most active in kids, then in adults when sum breaks theyre woken up

Thicker in kids

Describe the outer and inner layer of the periosteum:

Outer: Protector, collagen fibres + nerve and blood supply + attach to tendon

Inner: Contains osteoprogenitor cells aka osteoblasts and osteoclasts and blood vessels

What is the effect of menopause on bone resorption?

Estrogen levels drop

Estrogen was a key inhibitor to bone resorption

What is the difference between an osteoblast and a fibroblast?

Osteoblast - produces bone matrix

fibroblasts - produce collagen to maintain general connective tissues

Name somewhere on a bone you would not find a periosteum

where joints are

How does testosterone affect bone growth vs how does oestrogen affect bone growth in puberty?

Adult men tend to be taller than adult women

male puberty happens later than female puberty

aka male bones have more time to grow

Oestrogen is responsible for female wider hip pelvic bone

What is the role of calcitonin and parathyroid hormone?

Calcitonin hormone- increase bone uptake of calcium, reduce ca in blood

Parathyroid hormone - decreases bone uptake of calcium, increase ca in blood

What is an epiphyseal line?

Epihyseal line was an epipypheseal plate as a child, it baso allows the bone to grow in length, once hormones stopped the bone from grrowing in length, all thats left is the line

What is the name of the fibers connecting the periosteum to the bone

Sharpey’s fibers or Perforating fibers

On a microscopic level describe the structure of an osteon

in the centre - blood vessels (Central Canal/ Haversian Canal)

around it is layers of bone tissue called lamellae

Inbetween each lamellae is gaps called LACUNA

These gaps contain osteocytes

coming across from the centre is tiny canals called canaliculus

this transportation system ensures bones are well vascularised and bones heal fast

What is trabeculae?

Rod like tissue forming spongy texture

What is an osteon

The basic structural unit of a bone:

Haversian canal - lamellae - lacunae - osteocyte

What is a perforating/volkmann’s canal

canals w blood vessels from the periosteum to the central/haversian canal

What is bone remodelling and describe how it works?

Bones are constantly regenerating - this process is called remodelling

So how does it work?

When blood calcium levels drop