Week 112 - Injury/trauma to wrist Flashcards
What are Langers lines?
The natural grain of the skin, cut in same direction to reduce scarring.
What do Fibroblasts do?
Fibroblasts make collagen, glycosaminoglycans, glycoproteins, reticular and elastic proteins.
What do Chondrocytes do?
They produce and maintain cartilage through collagen and glycoproteins.
What do Osteoblasts do?
Produce bone.
What do Myoblasts do?
Produce muscle.
What do Tenocytes do?
They are tendon cells, elongated fibroblasts that synthesise tendon fibres.
What does a tendon do?
Links muscle to bone, transmits the force.
What does a ligament do?
Links bone to bone, holds joint in place.
What does the meniscus do?
Acts as a shock absorber.
What is the role of the articular cartilage?
Pressure tolerance, protects bone.
What does the synovium do?
Lubricates the joint.
What are the two types of cell that form tissue?
- Parenchymal cells - produce main function of tissues.
* Support cells - produce structural scaffolding.
Connective tissue is the collective term for what two things?
1) Support cells
2) Extra Cellular Matrix (ECF)
What are the four classes of macromolecules in extra cellular matrix?
Collagen, Elastin, Glycoproteins, Proteoglycans.
What is the most abundant class of proteins in the body and what percentage does it account for?
Collagens, ≈20%
What are the four major families of collagen?
1) Fibrillar Collagens
2) Fibril-Associated Collagens
3) Sheet-forming and anchoring Collagens
4) Transmembrane collagens
What is the function of fibrillar collagen?
Rod-like molecules, provide mechanical strength.
What is the function of fibril-associated collagens (FACIT)?
Link fibrillar collagens to one another or ECM.
What is the purpose of sheet-forming and anchoring collagen?
Connect basal laminae in skin to underlying connective tissue.
What is the function of transmembrane collagen?
Functions as adhesion receptors.
What is the basic structure of collagen?
A triple-helix of 3 polypeptide chains.
Which soft body tissue has the highest tensile strength?
Tendons.
How are tendons organised?
- Collagen fibrils > Collagen Fibres > 1º2º3º Collagen bundles > Tendon.
- The bundles are surrounded by a membrane called endotenon.
- The tendon is surrounded by epitenon.
What weight percentage does water make up in tendons?
55%
What is the biochemical composition of tendons?
- 70-80% of dry weight is collagen.
* <1% proteoglycans
What is the main type of collagen in tendons and what are the minor collagens?
- 95% Type I collagen
* 5% type III and IV
What is the function of proteoglycans in tendons?
Regulate collagen fibril size and bind water to resist compression.
What are the functions of tendons?
- Allows muscle belly to be some distance from the site of action.
- Eliminates the need for muscle for the entire length between origin and insertion.
- Can act as a pulley.
- Enables muscle action to be focused.
- Act as springs - store energy during locomotion.
What is the name of the specialised structure present in the tendon when it inserts into a bone?
Enthesis - made of fibrocartilage.
What is the function of Enthesis fibrocartilage?
Present where tendons insert into bones, helps to dissipate compressive forces, thus reducing wear and tear.
Which part of the composition of tendon increases to form fibrocartilage?
Increased concentration of proteoglycans.
What is the basic structure of proteoglycans?
‘Bottle brush’
Proteo - A protein core.
Glycan - Contains glycosaminglyan chains, that branch off the main core.
What is the major proteoglycan in cartilage?
Aggrecan
What is a ‘wrap-around’ region?
A part of a tendon that wraps around bony pulleys, fibrocartalaginous.
What occurs at the myotendinous junctions that increases mechanical strength?
Muscle fibres split which increases the amount of anchorage available.
Which type of connective tissue provides the majority of proprioception?
Ligaments, as they are more vascular than tendons.
What is the biochemical composition of ligaments?
- Water 60-70% weight.
- Collagen 70-80% dry weight.
- Elastin <5% dry weight.
What is the collagen composition of ligaments?
- 70-80% of dry weight.
- 90% type I
- 10% type III
What are the functions of ligaments aside from stability?
- Provide information to the brain (proprioception, joint stability, pain)
- Attachment point for muscles.
- Tie down soft tissue onto bone.
What does immobilisation do to tendons?
Decreased mechanical strength, decreased proteoglycan content.
What does exercise do for tendons?
Increased collagen fibril size, increased size and stiffness.
What is a motor unit?
A single motor neurone and the muscle fibres it innervates.
What is a motor neuron pool?
All the motor neurones that supply one complete muscle.
What is the name of the region of a muscle fibre directly under the terminal portion of the axon?
Motor end plate.
What receptors are present on the motor end plate?
Nicotinic receptors.
What is the name for a single muscle cell and how is it composed?
Muscle fibre. Formed of myofibrils(formed of myofilaments), in a specialised cytoplasm known as the sarcoplasm, it has many mitochondria and multiple peripheral nuclei. The cell membrane is known as the sarcolemma.
What is the name of a single, repeating, functional unit of a myofibril?
Sarcomere
What is a sarcomere composed of?
Thick and thin filaments
What is the thick filament of a myofibril?
Myosin.
What is the thin filament of a myofibril?
Actin, also contains troponin and tropomyosin which regulate contraction.
How are the filaments arranged in a sacromere?
- A band - composed of the thick filaments
- Z line - the end of the thin filaments
- H zone - The thick filament where the thin filament does not overlap.
- M line - Proteins that link the thick filaments in the centre.
- I band - The thin filament where it is not overlapped by the thick filaments.
What is the A band?
The thick filaments.
What is the Z line?
The end of the thin filaments (lateral edge of the sacromere)
What is the H zone?
The thick filament where the thin filaments don’t overlap.
What is the M line?
The centre of the sacromere, a line of protein that bind the thick filament together.
What is the I band?
The portion of the thin filament where it is not overlapped by the thick filaments.
What is the structure of myosin?
Myosin is the thick filament and has glomerular heads that project out, these heads have binding sites for Actin and ATP.
What is the structure of the thin filament?
- Actin backbone.
- Tropomyosin is a rod-shaped molecule of 2 intertwined peptides.
- Troponin is a small globular protein bound to the actin and tropomyosin.
What is the sliding filament mechanism?
This is how muscle contraction works.
• Ca2+ binds to the troponin which alters the shape of the tropomyosin revealing myosin binding points on the actin.
• The myosin heads bind to the actin.
• The power stroke then occurs with the use of stored energy to slide the actin over the myosin.
• ATP then binds to the myosin head and breaks the cross bridge, allowing the myosin head to bind to the actin at the next ‘notch’.
Which regions of the sacromere decrease in length when contraction occurs?
the I-Band and the H-Zone.
Where is the Ca2+ stored in the muscle fibre?
In the sarcoplasmic reitculum.
What causes the release of Ca2+ leading to muscle contraction?
An AP travels down T-tubules to the sarcoplasmic reticulum and Ca2+ is released.
What are the four sources of ATP in skeletal muscle?
1) Dephosphorylation of phosphocreatine.
2) Aerobic respiration
3) Anaerobic respiration
4) Oxidation of free fatty acids.
Briefly describe dephosphorylation of phophocreatine.
ADP + PC ≈ ATP + C
Very limited stores of PhosphoCreatine.
Briefly describe Aerobic Repiration.
Glucose + 2ATP + O2 > 6CO2 + 6H20 + 36ATP
Briefly describe Anaerobic respiration.
Glycogen + 2ATP > 2 lactic acid + 4ATP
Briefly describe oxidation of free fatty acids.
FFA + O2 > CO2 H20 +nATP
What are the three main mechanisms of muscle contraction?
- Isometric
- Isotonic
- Eccentric
What is Isometric muscle contraction?
This is when a muscle develops tension but does not contract.
When does isometric muscle contraction occur?
When a muscle supports something in a constant position, e.g. lifting a heavy load without actually lifting it.
What is Isotonic muscle contaction?
When the muscle shortens while the load on the muscle remains constant.
What is eccentric muscle contraction?
This is where the muscle extends whilst resisting an opposing force.
Which type of twitch fibre has a high ATPase activity?
Fast twitch (Type II)
What are type I twitch fibres?
Slow twitch, lower ATPase activity.
Which type of twitch fibre has a lower ATPase activity?
Slow twitch (Type I)
What are Type II twitch fibres?
Fast twitch, high ATPase activity.
What are the two main pathways with which muscle fibres produce ATP?
Oxidative and Glycolytic
What are Oxidative muscle fibres also known as?
Red muscle fibres (due to high concentrations of myoglobin).
Describe oxidative muscle fibres.
Also known as red muscle fibres, these have numerous mitochondria and have a high capacity for oxidative phosphorylation.
Which two factors allow oxidative muscle fibres to have a high capacity for oxidative phosphorylation?
- High levels of myoglobin, increases rate of oxygen diffusion and allows for a small store of oxygen.
- Surrounded by small muscle fibres.
What are glycolytic muscle fibres also known as?
White muscle fibres (due to lack of myoglobin).
Describe glycolytic muscle fibres.
White muscle fibres, contain few mitochondria but large stores of glycogen and high levels of glycolytic enzymes.
Three types of muscle fibre can be distinguished by speed of contraction and metabolic activity. What are they?
- Slow twitch fibres (Type I)
- Fast twitch (Type IIa)
- Fast twitch (Type IIb)
Describe slow twitch muscle fibres Type I.
- Low Myosin-ATPase activity
- Very resistant to fatigue.
- Rich in mitochondria and enzymes for OP.
Describe fast twitch (Type IIa) muscle fibres.
- High Myosin-ATPase activity.
- Red muscle fibres.
- Contains many mitochondria and enzymes for oxidative metabolism.
- Also contain glycogen stores and enzymes from glycolytic metabolism.
- Resistant to fatigue.
Describe fast twitch (Type IIb) muscle fibres.
- High myosin-ATPase activity.
- White fibres - poor blood supply, little myoglobin
- Rich in glycogen stores and enzymes for anaerobic glycolysis.
- Fatigue rapidly.
What is the order of recruitment of muscle fibres based on the number of motor units recruited?
1) Type I
2) Type IIa
3) Type IIb
What is the investigation used for neuromuscular disorders?
Electromyography.
