Skeletal Muscle- Histology Flashcards
Describe the development of muscle?
- Myoblasts align and fuse together to form myotubes.
- Myotubes synthesize the proteins to make myofilaments
- Part of the myoblast population does not fuse and remains mesenchymal cells called satellite cells.
What do satellite cells do?
•Satellite cells proliferate and produce new muscle fibres following muscle injury.
Name the 3 types of tissues?
Skeletal
Cardiac
Smooth
What are the 3 properties that muscles are bases on?
Voluntary or involuntary contractions
Striated
Location
Define Skeletal muscle?
Skeletal muscle (striated) - voluntary muscle. Involved in moving and stabilising bones and other structures.
Define Cardiac muscle?
Cardiac muscle (striated) - involuntary l muscle that forms most of the walls of the heart.
Define smooth muscle?
Smooth muscle (not striated)- involuntary muscle that forms part of the walls of most vessels and hollow organs. Moving substances through them by pulsations or peristaltic contractions.
Define type 1 fibres
rich blood supply and use oxygen to release energy. More resistant to fatigue.
Define type 2 fibres
fast twitch fibres
Whats the difference between Type 2a and Type 2b Fibres?
Type IIa – a hybrid of type I and type II. Respire aerobically, resulting in resistance to fatigue, but can also hydrolyse ATP quickly using aerobic and anaerobic metabolism.
•Type IIb – anaerobic, extracting energy from organic molecules in cells. Lots of energy produced rapidly, but fatigue quickly.
How much mass does skeletal muscle make up?
40%
What is the longest muscle in the body?
Sartorius
What is the smallest muscle in the body?
Stapedius
What os the biggest muscle in the body?
Gluteus maximus
What are the 2 attachments in skeletal muscle?
Origin- attachment that moves the least
Insertion- attachment that moves the most
How are Skeletal muscle joined to bone?
Skeletal muscle are joined to bone by tough connective tissue called tendons.
What are the 4 functions of skeletal muscle?
Skeletal Muscle
Maintenance of posture
Support of soft tissues
Thermoregualtion
Define a prime mover?
Muscle with the major repsonsibilty for certain movement
Define an antagonist?
Muscles that opposes or reverses a prime mover.
Define Synergist?
Muscles that aids a prime mover in a movement.
Describe a flat muscle?
Have parallel fibre often with an aponeurosis
Describe a pennate muscle?
Feather like deltoid
Describe a fusiform muscle?
Spindle shaped with thick belly and tapered end
Describe convergent muscles?
Arise from a broad area and converge to form a single tendon
Describe quadrant muscles?
is equal muscles
Describe circular muscles
Eyelids
Describe Multiheaded muscles?
More than one head like biceps brachaii
What are the large multinucleate cells in skeletal muscle?
They’re fused myoblasts surrounded by loose connective tissue containing collagen and elastin fibres which merge into the tendon at the site of muscle attachment.
Define the structure of a skeletal muscle?
- Endomysium around single muscle fibre
- Perimysium around a fascicle (bundle of fibres)
- Epimysium covers the entire skeletal muscle
- Epimysium blends into a connective tissue attachment
How do neurological impulses work in the skeletal muscle?
Impulses travel from the precentral gyrus nerves that supply muscles by releasing acetylcholine
Explain how the skeletal muscle contracts?
Each muscle fibre contain hundred of myofibrils
Each myofibril is made up of actin and myosin
Myosin filaments use ATP to walk along the actin filaments using cross bridges.
This pulls the actin filaments closer together bringing the Z lines closer together shortening the sarcomere
They contract by pulling never pushing
What filaments are anchored to z lines
Actin
Define reflexive contraction?
Although skeletal muscles are referred to as voluntary, certain aspects are automatic
Define tonic contraction?
Even when relaxed the muscles are slightly contracted.
This slight contraction does not produce movement but gives the muscles firmness. Assisting stability of joints and the maintenance of posture, while keeping the muscle ready to respond to appropriate stimuli.
Define the 2 types of phasic contraction?
Isotonic
Muscle changes length in relationship to production of movement
There are 2 types concentric and eccentric contractions.
Isometric
Muscle length remains the same.
Name some properties of cardiac muscle
Never fatigues Striated in appearance Heart Single Nucleus Regulated intrinsically
How does the heart act as a pacemaker?
An impulse conducting system composed of specialised cardiac muscle fibres.
Name some properties of smooth muscle?
Fatigues slowly
Forms large part of the middle layer of wall blood vessels
Found in the skin forming arrector pilli muscles of hair and eyeball
CVS
Digestive system and urinary tract
Non strained, no sarcomeres and contains actin and myosin
Define myositis
Autoimmune inflammatory disease of muscle skin, lungs and heart.
Breathing and swallowing is effective
What is the primary treatment for myositis?
Steroids and DMARDS and in more severe cases, the biological therapy of rituximab is used.
