HA Test 2 prep

Bone shapes, Components and Markings

The skeletal system

Consists of bones and associates cartilage connected to form articulations (joints)

The axial skeleton

80 bones that form the

• Sull

• Vertebral column

• Ribs

• Sternum

Forms the longitudinal axis of the body and protects the brain, spinal cord and organs in the thorax

The appendicular skeleton

Bones of the upper and lower limbs

Bone

Definition: bone is a calcified living connective tissue that forms the majority of the skeleton

Compact = dense bone that forms the outer shell of all bones and surrounds spongy

Bone

Spongy = highly pours (this is the spongy appearance)

Classifications of bones

Bones have 3 landmarks

1. Articular surfaces

• Areas of the bone that will form a joint

• Usually smooth and covered with hyaline cartilage

1. Protrusions

• Boney landmarks that stick out

• Function as bony landmarks for tendons and ligaments to attach to

1. Depressions (holes)

• Boney landmarks that provide space for another structure like blood vessels or nerves

  

Bone Development

Ossification = A process of bone formation

Bone of the skeleton develop in two methods

1. Endochondral ossification

Hyaline cartilage turning into bone

• Long bone, short bones and most irregular bones

1. Intramembranous ossification

Bone develops withing a membrane

• Flat bones

Bones grow in length

Diaphysis is the primary centre of ossification because it begins to ossify before birth

Epiphysis is the secondary centre of ossification because it only starts to ossify after birth

Stages of ossification

Length

• Main growth occurs at the epiphyseal cartilaginous growth plate

In these x-rays you can see the difference in size of the epiphysis

Bones grow in width

To make bones wider we add more osteons

• The formation of new osteons results on bone growth and width

1. Intramembranous ossification

Bone develops withing a membrane

• Flat bones

1. Bone cells form in membrane

2. There is a cologne matrix being laid down

• There needs to be good blood supply to develop this

1. As the flat bones develop you end up with a sandwiched arrangement of cortical and cancellous bone

Bone Remodelling

Bone is continuously being remodelled during our life

• Bone will adapt the loads under which it is placed

Or

• Bone is laid down where its needed and reabsorbed where it is not needed

This image shows bone density increasing in a bone that is placed under more stress than another to make it stronger

Calcium Homeostasis

Bone stores calcium

Osteoclasts

When there is extra calcium in the blood osteoblasts take that calcium and us it to make the bones stronger

Osteoblasts

They break down bone. When the body needs more calcium in the blood osteoclasts break down bone tissue to release more calcium

Periods of inactivity

• Bone is not mechanically loaded

• Activity of osteoclasts remove both the ground substance and the cologne matrix

Periods of increases activity

• Bone is mechanically loaded

• There is increases osteoblasts and osteocytes activity in adding and rebuilding the collagen matrix and adding minerals

  

Bone Fracture and Repair

Bones heal very well because bones have a very good blood supply

1. Bone breaks

2. Blood vessels in the bone get torn and they form a haematoma

3. Disruption of blood flow to the bone causes bone cells around the fracture to die

4. An internal callous forms and an external callous forms (this stabilises the fracture)

5. Osteoclasts reabsorb the dead bone 

6. The osteogenic cells become really active they divide and differentiate into osteoblasts

7. The cartilage in the internal callous is replaced by bone

8. The internal and external callous unite

9. The compact bone replaces spongy bone on the outside of the fracture

10. And the healing [process is complete

The aging skeleton

 Osteoporosis occurs when there is more bone reabsorption than formation

• Can affect any bone

• When density is lost so is its strength

Reducing the risk of osteoporosis

• Marinating calcium levels

• Maintaining vitamin D levels

• Regular exercise

This aims to strengthen existing bone and help reduce the risk of bone fracture

Surface Anatomy - Bones and Bony Landmarks

The mastoid process

A bony landmark behind the ear

Medial aspect of the clavicle (Collar bone)

How to find it

The notch is at the front and bottom of my neck

(anatomical terminology) Palpate the notch at the medial, anterior and inferior aspect of the neck. The medial aspect of the clavicle sits on either side of this notch. 

Medial epicondyle

How to find it

On the inside of the elbow joint

(anatomical terminology) Palpate the distal end of the humerus on the medial side

Anterior superior iliac spine

How to find it

The upper part of the pelvis on the side

(anatomical terminology) Palpate the lateral side of the pelvis to its most anterior point

In-between these landmarks is the appendix

Patella

How to find it

To the outside of the knee cap

(anatomical terminology) Palpate the anterior distal aspect to the thigh. Palpate laterally to the inferior part of the patella. This is the head of the fibula

Or

Proximal aspect of the fibula found laterally

Medial malleolus

How to find it

In the inside of the ankle

(anatomical terminology) Palpate the distal aspect of the tibia on the most medial side

Articulate = When bones join with each other

Articulations = Joints

Movement always occurs at a joint

Joints can be classified by the type of connective tissue that unites them. This will have a direct correlation to how mobile they will be.

1. Immobile

2. Partly mobile

3. Highly Mobile

We have 3 different histological joint classifications

1. Fibrous joints

• Held together by fibrous connective tissue

• Little to no movement 

There are 3 types of fibrous tissue

• Sutures

• Gomphoses

• Syndesmoses

1. Cartilaginous joints

• United by a pad or disc of cartilage

• A little bit of movement

2 types

• Primary cartilaginous joints

United by hyaline cartilage

• Secondary cartilaginous joints

Thin layer of hyaline cartilage over the articulating bone surfaces and then a pad or dics of fibro cartilage in between

1. Synovial joints

Features

• Boney components are indirectly connected to one another by a joint casual that  encapsules the joint

• Lining the inner surface of this casual is the synovial membrane that produces synovial fluid

• The ends of the bones are also covered in hyaline cartilage

Functional joint classifications

Hinge - one plane

Pivot - one plane

Condyloid

Saddle

Plane or gliding

Ball and socket

• The shape of the joint will also determine how many axis the joint can move around

Joints that only move in one plane = uniaxial and include a hinge joint

Joints that move in 2 planes = biaxial and include a condyloid joint

Joints with the most movement = triaxial or Multiaxial

Simple joints

• Function for stability

Complex joints

• Function to achieve mobility

  

Locating joints using surface anatomy

What is it?	Where is it	Photo
Sternoclavicular	The medial end of the clavicle
Acromioclavicular	Lateral end of the clavicle
Elbow superior Radioulnar joint   Inferior radioulnar joint	Feel for the medial and lateral epicondyle Move distally from the lateral epicondyle and there will be a space before another bony prominent (the head of the radius) The head of the radius articulates with the ulnar
Metacarpophalangeal	Metacarpal bones articulate with our phalanges Feel the knuckle while you flex and extend
Hip	The head of the femur articulating with the hip bone (ball and socket joint)   Locate the Anterior superior iliac spine Move inferiorly and locate ethe hip joint     Locate the greater trochanter Move medially and locate the hip joint
Knee	Located between the tibia and the femur   Feel for a gap between the bumpy landmarks of the distal femur and the proximal tibia
Ankle	Locate the lateral malleolus and move medially and feel a gap where the ankle joint is found
1st metatarsal	Find the mesotarsal bone on the medial side of the foot Distally to that there will be a bony landmark and even more distally to that there will be a gap that is the joint
Manubriosternal	Find the manubrial. Inferiorly to that and find a small prominence identifying the Manubriosternal joint
Intervertebral joints	locate the spina's process (posterior bony landmark)

Joint stability

Is what keeps our joints in position while we sleep and rest, it also prevents movement that could cause injury. 

Stability = Bones and ligaments & muscles and Tendons

• Unstable joints will be more susceptible to pain, injury, dislocations or degeneration

Main contributing factors

1. Congruence

How well the bones fits together when forming a specific joint

Congruency varies between different joints

Hip

• Articulating surfaces fit well together

Shoulder

• Shallow socket of the scapula bone and large humorous head. They don’t fit well together

Example:

1. Congruent joint

Hip joint

Advantage = more stable

Disadvantage = less mobile

1. Incongruent joint

Shoulder

Advantage = more mobile

Disadvantage = Less stable

1. Ligaments 

Connect bone to bone

Predominantly located around synovial joints

Position and orientation will determine their function

Ligaments become tight when force is applied to that area

Example

Vertebra ligament on the anterior prevents movement bending backwards

Vertebra ligament on the posterior side prevents the movement of bending over

1. Muscle and tendons

There are 2 parts of a muscle

1. Muscle belly

• Conbtractile component

1. Tendon

• Connects the muscle to bone

Skeletal muscle / Voluntary muscle functions

1. Produce movement

2. Maintain posture

3. Stabilise joints

4. Generate heat

5. Protect organs

Connect bone to bones with tendons and they cross joints to produce movement

• With an exception of facial muscles which attach bones to skin (wrinkles)

2 principles that determine how muscles work

1. A muscle must cross a joint in order to act at that joint

2. The position of a muscle at a joint determines the plane and direction of movement it can produce

• To see what plane a movement will be in you just need to see where the muscle is crossing the joint of interest and then we can work out the action

The muscle compartment rule

• Muscles that have a common function at a joint are usually located together in a muscle compartment, innervated by the same nerve and share the same arterial supply and venous drainage

How to apply this?

Lower limb example:

The anterior muscle compartment od the thigh contains the quadriceps. There are 4 muscles here, they are all innovated by the same nerve and they all travel distally to attach to the anterior tibia. Because all of these muscles travel anteriorly they will pull the tibia anteriorly into and extended position

4 main characteristics of skeletal muscles

1. Excitability

• Ability to receive and respond to stimulus

1. Contractibility

• Ability to shorten when stimulated

1. Extensibility

• Ability to be stretched

1. Elasticity

• Ability to recoil and resume its resting length

  

Muscle Compartments

Upper limb muscle compartments

1. Anterior compartment

1. Posterior compartment

There are medial and lateral intermuscular ceptors that allow us to look at images and identify where the anterior compartment is and where the posterior compartment is.

Skeletal muscles and muscle groups

Where a muscle is running relative to a joint and the action that muscle is producing at that joint

Application of principles

Principle: A muscle must cross a joint in order to act at that joint

What muscle is this?

Answer: Deltoid

What joint does the deltoid muscle cross?

Answer: Shoulder joint

What movement is occurring here?

Answer: Abduction

Application:

A muscle must cross a joint in order to act at that joint

The deltoid attached from the scapula to the humerus and crosses the shoulder joint, thereby producing the movement abduction at this joint. 

Muscle roles

Different muscles have different jobs to make sure that actions are smooth and controlled

Muscles that produce movements against gravity = Primary movers/agonists

Muscles that control movements where gravity is the prime mover = Antagonists

Muscles that hold/maintain position = Fixator

Muscles working together (synergy) = Synergist

Types of muscle contractions

Muscle tension

• Force generated by muscle contracting

• Load does not need to move necessarily

Isotonic contraction

Where tension in the muscle remains constant

What changes

• The length of muscle either shorter or longer

Eccentric = longer

Concentric = shorter

Isometric

When muscles produce tension without changing the length of the joint or the length oof the muscle

Opened and closed chain movements

When we move our bodies our limbs interact with the environment in different ways. Sometimes our hand is free to move through space and other times it is fixed against a surface.

Open chained movements

When the distal part of the body is free to move while the proximal part is fixed

Closed chain movements

When the distal end of a body segment is fixed and the proximal end of the body if free to move

Levers

A lever is a rigid bar that pivots on a fulcrum when force is applied. In the body, joints serve as fulcrums and bones act as levers. Muscles contract to create effort at their insertion points, moving the load—which includes the bone, tissues, and any object being lifted.

First class lever

Arrangement

• Effort applied at one end

• Load at the other end 

• Fulcrum can sit anywhere in-between

Second class lever

Arrangement

• Effort applies at one end

• Fulcrum is at the other end

• Load sits anywhere in between

Third class lever

Arrangement

• Load at one end

• Fulcrum is at the other end

• Effort is applied anywhere in between