BMS10-1018 Muscle Histology Flashcards
Which non-muscle cells make up muscle tissue?
Fibroblasts
Exocrine epithelial
What do myoepithelial muscle cells do?
Secrete milk
What are the precursors?
Myoblasts
What do dorsal medial cells form, with an example?
Myotome muscles e.g. deep back muscles
What do ventral lateral lip cells form with an example?
Hypaxial myotome e.g. body wall muscles
Where do these 2 types of cells originate?
Lips of the dermomyotome
What forms myosin?
Myoblast fusion
When and what does the endo, peri and epimysium fuse?
With dense collagenous connective tissue of the tendon at the myotendinous junction
What does the endomysium of skeletal muscles contain?
Blood vessels
Fibroblasts
What are myofibres?
Skeletal muscle fibres
Sarcomere
Contractile unit of skeletal muscle
Striations
Alternating light and dark bands appearing across the length of the fibre
What makes up thick filaments?
Myosin
M line
Down the middle of the myofibril due to creatine kinase
H zone
Myosin
A band
Overlap of actin and myosin
I band
Actin
Z line
Border of the sarcomere
Costameres
Regions associated with the sarcolemma of skeletal muscles that transfer the force from the sarcomere to the extracellular matrix at the Z line so its transferred to neighbouring sarcomeres
What innervates a myofibre?
One motorneuron
NMJ
Where nerves form synapses on the muscle fibre membrane
How many muscle fibres does a motorneuron have contact with and what is this called?
Many, a motor unit
What does a large muscle unit indicate?
Don’t need a fine degree of control
How many NMJ does a muscle fibre have?
Normally 1
Motor unit
Muscle fibres innervated by the same motor neuron
Where is fast myosin found?
White muscle fibres
Why do fast fibres quickly fatigue?
Have little myoglobin (oxygen binding protein)
Where are slow fibres found?
Red muscle fibres
Which 2 parts of the body don’t have a mix of both fast and slow fibres?
Posture muscles are all slow
Eye muscles are all fast
Where are triads?
Pair at the A I border
T tubules
Allows for propagation of the action potential
What is a triad?
T tubules with the sarcoplasmic reticulum
Terminal cisternae
Enlarged areas of the sarcoplasmic reticulum around T tubules for Ca release
Muscle fibres are specialised…
Post-mitotic cells
Can nuclei of fibres re enter the cell cycle?
No so they cant divide
What is on the surface of muscle fibres?
Satellite cells
Are satellite cells always active?
No mainly they aren’t dividing but they can be activated to enter the cell cycle to become myoblasts
What do myoblasts become?
Fuse to make new myofibres
Specialise to provide myonuclei for existing fibres
What do satellite cells sits on?
Basal lamina
Where are the nuclei in cardiac cells?
Centrally
How do cells connect and what do they form?
Intercalated discs to form a functional syncytium
What are intercalated disks?
Modified Z lines
What allows for transmission of action potentials?
Gap junctions
Why cant we regenerate cardiac muscle?
No satellite cells
What does actin connect to either side of the gap junction?
Desmosome
Fascia adherens
What NS modulate HR?
Para and sym
Why doesn’t the heart rely on neurons?
Uses the muscle cells and purkinje fibres
What are purkinje fibres?
Conductive myocytes
Where is smooth muscle found?
Walls of vessels, respiratory tract, gut and urinary tract
What surrounds smooth muscle?
Basal lamina and connective tissue
What are smooth muscles filled with?
Actin and not a lot of myosin
How does electrical excitation spread?
Gap junctions
Why aren’t smooth muscles striated?
Different composition of actin and myosin
What controls contraction?
Hormones
Sym VS Para
