Tissues of the Musculoskeletal System

Question 1

what are the layers of the body (superficial to deep)?

Answer 1

Skin –> Superficial fascia (superficial fatty layer & deep membranous layer) –> Investing layer of deep fascia –> Deeper layer of deep fascia –> Muscle

Question 2

what is fascia?
what 2 categories is it classified into?

Answer 2

Fascia is a fibrous connective tissue containing varying amounts of fat.
It is traditionally classified into two broad categories:
superficial fascia
deep fascia.

Question 3

what is superficial Fascia (hypodermis)?
function and contents

Answer 3

Superficial fascia is the subcutaneous fibrous fatty connective tissue lying beneath and merging with the dermis of the skin.
Its thickness varies from one area of the body to another
Because it is a connective tissue it consists of:
Cells: Fibroblasts, immune cells including macrophages
Aqueous matrix
Fibres: elastin and collagen fibres
Fat
Function:
It attaches the skin to the rest of the body and makes it flexible.
Acts as a conduit for vessels and nerves moving to and from the skin
Serves as a metabolic reservoir.
It allows movement of the skin over deeper areas of the body

Question 4

what are the 2 variants of deep fascia?

Answer 4

Investing Layer of Deep Fascia
Deeper layers of Deep Fascia

Question 5

what is the Investing Layer of Deep Fascia?

Answer 5

Most superficial layer of deep fascia.
It is continuous throughout the body
It wraps the body in a membrane of tough fibrous connective tissue that
Function: separates body from the skin and superficial fascia.
This fascia goes by different names depending on which region of the body it envelopes.
E.g. antebrachial fascia, crural fascia, fascia lata etc… the forearm, thigh and leg

Question 6

what is the Deeper layers of Deep Fascia?

Answer 6

The deeper layers of deep fascia are inward continuations from the investing layer of deep fascia.
In limbs it gives rise to intermuscular septa, interosseous membranes and periosteum.
It therefore leads to the structural partitioning of a limb into distinct muscular compartments.
Muscles of a particular compartment have a:
Common functions
Share common innervation
arterial supply
venous drainage
lymphatics.
If there is a bleed or fluid accumulation within a muscular compartment of a limb it can result in compartment syndrome. This can occur in other parts of the body, including the abdomen.

Question 7

what is a tendon?

Answer 7

Tendons are tough bands of dense regular connective tissue.
They have an abundance of parallel collagen fibres, which allows them resists tensile forces in one direction.
They attach skeletal muscles to the periosteum of bones.

Question 8

where are tendons found?

Answer 8

Tendons are found at the distal and proximal ends of muscles:
Proximal: Binds muscles to their point of origin
Distal: Bind muscles to their point of insertion
As a muscle contract, the tendon transmit the mechanical force to the bone, pulling it and therefore causing movement.

Question 9

what are ligaments?

Answer 9

Ligaments are tough bands made of dense regular connective tissue.
They have an abundance of parallel collagen fibres, which allows them resists tensile forces in one direction.

Question 10

what are the 2 functions of ligaments?

Answer 10

Ligaments connect bone to bone.
Syndesmosis: a type of fibrous joint held together by ligaments or an interosseus membrane. They allow for very little movement.

Ligaments reinforce the joints.
Depending on their position relative to the joint capsule, ligaments are classified into:
Capsular ligaments: thickenings of the joint capsule
Intracapsular ligaments: lie internal to the joint capsule. They reinforce the connection of the articulating surfaces of the joint.
Extracapsular ligaments: lie outside the joint capsule. They provide the most stability to the articulating bones.

Question 11

why do ligaments and tendons have slow healing time?

Answer 11

Ligaments and tendons are poorly vascularised which results in poor healing times.
You will also get scar formation during healing which results in weaker structures.
Therefore, the tendon/ligament will not be as strong as it was pre-injury

Question 12

what is a bursa?
what is bursitis?

Answer 12

A bursa is a small sac lined by a synovial membrane, and filled with synovial fluid.
They are found between moving structures in a joint (e.g., tendons, muscles, bones)
Their function is to reduce friction between these adjacent structures as they slide over each other.
The majority of bursae are located near the large joints of the arms and legs.
They can become inflamed following infection or irritation (over-use of the joint). This is called bursitis.
Symptoms: pain, tenderness, swelling
Cause: over-use/infection

Question 13

what is a tendon sheath?

Answer 13

Tendon Sheaths are full of synovial fluid - wrap around tendons and allow tendon to travel smoothly

Question 14

what is cartilage?
what cartilage does the musculoskeletal system specifically contain?

Answer 14

Cartilage is a flexible connective tissue composed of chondrocytes and chondroblasts, collagen and elastin fibres and abundant ground substance rich in proteoglycan.
The musculoskeletal system specifically contains articular cartilage (predominantly made up of hyaline cartilage), a type of cartilage that lines the articulating surfaces of bones.
The articular cartilage allows articulating bones to bear weight and glide over each other with very little friction & act as shock absorbers.

Question 15

describe the structure of skeletal muscle

Answer 15

Individual muscles are wrapped in Fascia
The Muscle belly - wrapped in connective tissue: epimysium
Fascicle (made up of multiple muscle fibres) - wrapped in connective tissue: perimysium
Muscle fibre (single cell) - wrapped in connective tissue: endomysium
Inside muscle fibres are Myofibrils.
Myofibrils contain myofilaments (actin & myosin)
Muscles are well supplied with nerves and blood vessels – need a lot of oxygen to keep contracting.

Question 16

describe the blood supply of muscles

Answer 16

Blood vessels tend not to bridge between muscles to avoid tearing when muscles contract.
‘Muscle pump’ (e.g. in the calf) is when the muscles acts on intramuscular veins with valves to help pump blood up the veins as blood in veins is at quite low pressure.

Question 17

how does a muscle grow and repair? (including the 2 types of muscle growth)
what is hypertrophy?

Answer 17

There are two Types of Muscle Growth:
Prenatal muscle growth in utero: almost exclusively involves growth in number of muscle fibres
Postnatal muscle growth: almost exclusively involves growth in size of muscle fibres - hypertrophy
Hypertrophy occurs when muscle stem cells (satellite cells) merge into muscle fibres. This is stimulated by:
Normal growth
In response to exercise - Muscle overloading/resistance training.
Protein ingestion can also stimulate muscles fibre growth by mechanism above
Various hormones, eg: IGF-I, growth hormone, testosterone

Question 18

when does muscle atrophy occur?

Answer 18

Muscle atrophy occurs with underuse of muscle (e.g. prolonged period of bed rest), age, chronic inflammation, neuropathies (muscle loses nerve supply as nothing stimulating it anymore so wastes away).

Question 19

how do muscles attach?
via? (4 ways)

Answer 19

Muscles attach - usually to bone - via:
Tendons: collagen-rich cords or straps (lined up parallel fibres)
Aponeuroses: sheet-like tendons (lined up parallel fibres)
Fascia: dense connective tissue (felted appearance of fibres)
Fleshy/direct attachment (epimysium directly attaches to periosteum)

Question 20

what are the 8 different muscle classifications?

Answer 20

A: Circular Muscle
B: Strap Muscle
C: Fusiform Muscle
D: Convergent Muscle
E: Unipennate
F: Bipennate
G: Multipennate
H: Two-bellied

Question 21

what is a circular muscle?
example?

Answer 21

The muscle is ring shaped
The fascicles are arranged in concentric rings.
Example: Orbicularis oris – muscles that surround your mouth and allows you to close your lips.

Question 22

what is a strap muscle?
example?

Answer 22

The muscle has a narrow strap-like belly
The fascicles are arranged in parallel and run along the long axis of the muscle.
Example: Sartorius muscle of the thigh

Question 23

what is a fusiform muscle?
example?

Answer 23

The muscle is spindle-shaped - belly wider than points of origin & insertion
The fascicles are arranged in parallel
Example: The biceps brachii muscle of the arm.

Question 24

what is a convergent muscle?
example?

Answer 24

Muscle is a triangular shape – broad origin and narrow insertion.
Fascicles converge toward a single tendon of insertion.
Allows for very strong contraction
Example: Pectoralis Major Muscle

Question 25

what is a unipennate muscle?
example?

Answer 25

The fascicles insert obliquely into only one side of the tendon
Example: The extensor digitorum longus muscle of the leg

Question 26

what is a bipennate muscle?
example?

Answer 26

The tendon is central giving the muscle a resemblance of a feather.
The fascicles attach obliquely to a central tendon from opposite sides.
Example: The rectus femoris of the thigh

Question 27

what is a multipennate muscle?
example?

Answer 27

A central tendon which branches into two or more tendons
The fascicles attach obliquely into the tendons
Example: The deltoid muscle

Question 28

what is a two- bellied muscle?
example?

Answer 28

Two bellies united by a single tendon

Question 29

what are the 5 different types of bones?

Answer 29

Long bones
Short bones
Flat bones
Sesamoid bones
Irregular bones

Question 30

what is a long bone?
example?

Answer 30

Bone that is longer than it is wide.
Structure:
The marrow cavity is enclosed by the diaphysis which is thick, compact bone.
The epiphysis is mainly spongy bone and is covered by a thin layer of compact bone
Examples of long bones include the humerus, ulna, tibia and clavicle.

Question 31

what is a short bone?
example?

Answer 31

Bones that have a roughly cuboid or round shape
Structure:
Contain a thin layer of compact bone surrounding the spongy bone and marrow
Only Examples include the tarsal and carpal bones.

Question 32

what is a flat bone?
example?

Answer 32

Thin bones that can be curved or flat.
Structure:
Contain two parallel layers of compact bones surrounding a layer of spongy bone and bone marrow.
Examples include most of the skull bones, scapula, sternum and sacrum.

Question 33

what is a sesamoid bone?
example?

Answer 33

Small, rounded bones that are embedded in muscle tendons where the tendon passes over a joint.
Example The patella.

Question 34

what is an irregular bone?
example?

Answer 34

Bones that do not fit into any of the other categories.
Structure
A thin layer of compact bone covers a mass of mostly spongy bone.
Generally, contain foramina through which soft tissue and neurovascular structures pass.
Examples include the vertebrae, hip bone and some bones of the skull.

Question 35

name a common clinical complication that could occur in a tendon

Answer 35

Inflammation or irritation of a tendon
It causes pain and tenderness just outside a joint
Cause: overuses or injury of a tendon
Tendinitis is most common around your shoulders, elbows, wrist, knees and heels

Question 36

what are pressure sores?

Answer 36

Pressure ulcers (pressure sores) are injuries to the skin and underlying tissue, primarily caused by prolonged pressure on the skin.
They can happen to anyone, but usually affect people confined to bed or who sit in a chair or wheelchair for long periods of time.
Pressure ulcers can affect any part of the body that’s put under pressure.
They’re most common on bony parts of the body, such as the heels, elbows, hips and base of the spine.

Question 37

what is compartment syndrome?

Answer 37

A sustained increase in intra-compartmental pressure so that it eventually exceeds arterial perfusion pressure - causing neurovascular compromise within that compartment.

Question 38

what is the aetiology of compartment syndrome?

Answer 38

Fractures/blunt trauma/crush/burns
Restoration of perfusion after an ischaemic limb
Haemorrhage
Intra-arterial injection
NB: the shoulder is a good area to inject into as it is unlikely to cause compartment syndrome.

Question 39

how does compartment syndrome present?

Answer 39

Severe pain on passive extension of the muscle
Key Sign: Pain is often described as out of proportion to severity of injury (pain not relieved with normal analgesia)
Late sign (occur when diagnosis is late):
Neurovascular compromise - damage to nerve and vessels in compartment: 3 P’s
Paraesthesia: a painful prickling or tingling sensation
Paralysis: difficulty moving
Pulselessness: no pulses in lower limb (suggests arterial compromise!) –> ischaemic damage –> necrosis.
If decompression is late there is severe risk of infection as dead muscle is ideal culture medium.
Myoglobin can also leak into circulation and cause renal damage - cause renal failure ( how? Myoglobin breaks down into substances that can damage kidney cells)

Question 40

how to deal with compartment syndrome?

Answer 40

Best way to deal with compartment syndrome is to make an incision in effected compartment to relieve pressure and allow muscles to continue to receive oxygenated blood. This is called a fasciotomy but you need to careful to avoid damaging the bone and the blood vessels.

Question 41

describe the main gross divisions of the human skeleton

Answer 41

The skeleton is divided into:
Axial skeleton which includes the skull, spine, ribs and sternum.
Appendicular skeleton – skeleton of limbs with associated girdles (attachments of limbs to axial skeleton)
E.g. pectoral girdle is comprised of clavicle and scapula and attached to upper limb.
Lower limb is attached to sacrum via pelvic bones (pelvic girdle).

Question 42

what imaging is used when looking at the MSK system?
what is it used to diagnose?
adv?

Answer 42

Ultrasound imaging uses sound waves to produce pictures of muscles, tendons, ligaments, nerves and joints throughout the body.
It is used to help diagnose sprains, strains, tears, trapped nerves, arthritis and other musculoskeletal conditions.
Ultrasound is safe, non-invasive, and does not use ionizing radiation.