Histology Of Muscles Flashcards
What is the main function of skeletal muscle?
Locomotion
Joint stability
Heat generation
Posture maintenance and muscle tone
What is the function of smooth muscle?
Vasoconstriction and vasodilation
Peristalsis
What is the function of cardiac muscle?
Caradiac motion and contractility
What are transverse tubules?
Inward folds of the sarcolemma
Well developed in skeletal and cardiac muscle to transport calcium
Absent in smooth muscle
What are intercalated disks?
Specialised intracellular junctions only present in cardiac muscle
What are the sour different types of skeletal muscle?
Parallel muscle
Convergent muscles
Pennate muscles muscles
Circular muscles
What are the different types of parallel muscle?
Parallel muscle e.g bíceps
Parallel with tendinous bands e.g rectus abdominus muscle
Wrapping muscle e.g supinator
What are the different types of convergent muscle?
Convergent muscle is the only subgroup
For example the pectoralis major
What are the different types of pennate muscles?
Unipennate muscle e.g extensor digitorum muscle
Bipennate muscle e.g rectus femoris muscle
Mutlipennate e.g deltoid muscle
In pennate muscles fibres attach obliquely to the tendon, this provides more force but less flexibility.
What are the different types of circular muscle?
Circular muscle is one category
The muscle itself can be contracted or relaxed
Give an overview of the different connective tissues in muscle?
Endomysium surrounds muscle fibres contains nerve axons and blood vessels
Perimysium provides Fibrocolloganous support to the muscle fascicles, contains nerves, lymphatics and blood vessels
Epimysium provides fibrocollagenous support to the whole muscle
All layers are continuous with each other and the muscle tendon, are mainly dense irregular connective tissue
What does skeletal muscle look like in cross section?
Sarcoplasm is eosinophilic in appearance
Each muscle fibre is hexagonal in shape
Have many peripheral nuclei
Finrocollagenous septa between different muscle fascicles contain blood vessels
What does skeletal muscle look like in longitudinal section?
Striations are visible
Flattened and elongated nuclei at the periphery of the fibres
What is a striation?
Repeating dark and light bands, from the A and I band in the sarcomere
Along the length of each myofibrils, evident in longitudinal section
What is a sarcomere?
The region of a myofibrils between two successive Z discs.
Average 2um long and is the smallest contractile unit of a muscle fibre
What is shown in the image?
Electron microscope of longitudinal skeletal muscle
Shows sarcomere se that make up striations
The cytoplasm between each muscle fibre contains mitochondria, SR and glycogen.
What do the cross sections of different skeletal muscle bands look like?
Accessory proteins include myomesin
Where is acetylcholine esterase found?
In the motor endplate
Found in the junction folds of the muscle, bound to the basement membrane
What are y efferent fibres?
Specialised motor axon, terminal axon in the motor endplate can innervated individual muscle spindles fibres
Spindle fibres are intramural muscle cells involved in oroprioceotion.
What is myasthenia gravis?
An autoimmune disease mainly affecting voluntary muscles
Antibodies are produced, binds to nicotinic receptirs preventing ACh from causing depolarisation in the muscle
Causes muscle weakness and fatigue, often struggle to life arms and maintain posture.
Eyes are the most notably affected shown by diplopia and ptosis.
How is myasthenia gravis often treated?
Administer anticholinesterases inhibitors that inhibit the action of the enzyme acetylcholineesterase This increases the action of acetylcholine by allowing it to compete better with the antibody.
What is gowers sign?
Positive gowers sign indicates DMD
Shows how children with DMD get up from a supine position.
Often roll onto belly, then onto elbows and knees, to hands a knees, then uses there hands to walk up their b dog until standing.
Hypertrophy of calf is often seen. As muscle is replaced by fat
What does the histological slide for progressed DMD look like?
Death of muscle cell fibres and replaced with fat cells
Muscle fibres are various diameters
Larger connective tissue between muscle fibres
What does cardiac muscle look like in histológicas slides?
Striated
Single Central nuclei that are elongated
Branched muscle fibres, less organised than skeletal muscle
Capillaries are often in close proximity identified by the erythrocytes
Intercalated disks can be seen in longitudinal section
Muscles fibres are surround by supporting connective tissue septa which contains the nuclei of fibroblasts and smaller endothelial cells
