Tissues of the Musculoskeletal System Flashcards
what are the layers of the body (superficial to deep)?
Skin –> Superficial fascia (superficial fatty layer & deep membranous layer) –> Investing layer of deep fascia –> Deeper layer of deep fascia –> Muscle
what is fascia?
what 2 categories is it classified into?
Fascia is a fibrous connective tissue containing varying amounts of fat.
It is traditionally classified into two broad categories:
superficial fascia
deep fascia.
what is superficial Fascia (hypodermis)?
function and contents
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
what are the 2 variants of deep fascia?
Investing Layer of Deep Fascia
Deeper layers of Deep Fascia
what is the Investing Layer of Deep Fascia?
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
what is the Deeper layers of Deep Fascia?
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.
what is a tendon?
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.
where are tendons found?
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.
what are ligaments?
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.
what are the 2 functions of ligaments?
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.
why do ligaments and tendons have slow healing time?
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
what is a bursa?
what is bursitis?
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
what is a tendon sheath?
Tendon Sheaths are full of synovial fluid - wrap around tendons and allow tendon to travel smoothly
what is cartilage?
what cartilage does the musculoskeletal system specifically contain?
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.
describe the structure of skeletal muscle
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.
describe the blood supply of muscles
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.
how does a muscle grow and repair? (including the 2 types of muscle growth)
what is hypertrophy?
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
when does muscle atrophy occur?
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).
how do muscles attach?
via? (4 ways)
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)
what are the 8 different muscle classifications?
A: Circular Muscle
B: Strap Muscle
C: Fusiform Muscle
D: Convergent Muscle
E: Unipennate
F: Bipennate
G: Multipennate
H: Two-bellied
what is a circular muscle?
example?
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.
what is a strap muscle?
example?
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
what is a fusiform muscle?
example?
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.
what is a convergent muscle?
example?
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