Lab 11 - Muscle Histology Flashcards
What can muscle tissue be divided into
Skeletal muscle
Smooth muscle
Cardiac muscle
What is skeletal muscle
Attached to skeleton, involved in such things as limb movement
What is smooth muscle
Located in the hollow organs of the body such as blood vessels, and the ‘tubes’ of the respiratory & digestive system.
What is cardiac muscle
Makes up bulk of walls of the heart ( myocardium )
What does skeletal and cardiac muscle look like under the microscope
Light and dark bands
Are skeletal and cardiac muscle striated or non striated
Striated
What can striated muscles do
Generate a lot of force quickly
Properties of smooth muscle
- Less forceful
- Lacks striations
What muscles innervated by ANS
Smooth and cardiac
Their contractions cannot be consciously controlled.
Invoulantary muscle
What muscle is innervated by Somatic NS
Skeletal
Contractions are under conscious control.
Voluntary
What are muscles composed of
Number of individual muscle cells
What are muscle cells referred to as
Muscle fibres - elongated
Properties of muscle fibres
- Filled with cytoplasm (sarcoplasm) and are enclosed by a plasma membrane (the ‘sarcolemma’).
- Contain all the usual organelles (mitochondria, nucleus etc.
- Much of the cell is filled with the contractile proteins (myofilaments) actin and myosin.
Properties of muscle cells
- Held together by connective tissue elements, which also transmit the blood supply to the muscle cells
- Heavily innervated - so when you look at muscle tissue under the microscope you will see blood vessels, connective and nervous tissue
How many groups of skeletal muscle are associated with the eye
2
6 extraocular muscles
- Attach to the skull posteriorly and insert into the sclera of the eye anteriorly
- They serve to move the eye in various directions
What does skeletal muscle do in terms of the eye
Raising and lowering the eyelids
e. g. orbicularis occuli is a facial muscle that, encircles the eye and its contraction results in eye closure.
e. g. levator palpebrae superioris, raises the eyelid. - located above the eye
What is the advantage of skeletal muscles being striated rather than smooth
Have more forceful contractions
What are the dimensions of skeletal muscle cells
Can be very long (3-4 cm) and relatively wide (up to 150mm).
= LARGE AND MULTINUCLEATE
What is levator palpebrae superioris muscles stained with
Toluidine blue
What are the white spaces shown in extraocular muscle
Blood vessels
What are the blue fragments shown in extraocular muscle
Nuclei
What are other structures in extraocular muscle
Axons
Myelin
What is the bulk of a skeletal muscle cells’ interior occupied by and what does this result in
The contractile proteins, actin and myosin
Consequently the nuclei and other intracellular organelles are pushed to the edge of the cell against the sarcolemma.
Identify the nuclei and the location of the other organelles in skeletal muscle cel
Pushed to the edge of the cells. Straited skeletal muscle - more than one nuclei per cell
Do the fibres branch in skeletal muscle
No
How are microfilaments arranged in skeletal muscle
(actin and myosin) are arranged in an orderly overlapping manner into sarcomeres (
What is a myofibril
Made of series of end to end sarcomeres
What is the relationship between a myofibril and a muscle fibre?
Myofibrils run the entire length of the muscle fiber and many myofibrils are found in a muscle fiber
What is longitudinal axis
Along axis of the cell
What is transverse section
Cross section - fibres coming towards you out of the page
How are fibres of many skeletal muscles such as superior oblique arranged
Bundled together in fascicles
What is epimysium
Surrounds the entire muscle
The interstitial connective tissue of muscle is subdivided into the epimysium
What is perimusium
Sheath of connective tissue that groups muscle fibers into bundles
What is endomysium
Connective tissue that surrounds each muscle fiber
Why does the muscle under higher power no longer appear striated
Transverse section – planar section same orientation as striations – striations no longer perpendicular to planar sections
What are the small holes in the muscle fibres
Blood vessels
Do all muscle fibres look the same in skeletal muscle
- No- have slightly different densities- are in different states, depends where you cut through – straight through plane (Actin or myosin)- every muscle fibre wouldn’t have the same number of myofibrils.
- Nuclei to the edges .
Properties of smooth muscles fibres
- Contain far less actin and myosin, and these contractile proteins are randomly arranged inside the cell, which accounts for its lack of regular striations. - Smooth muscle tissue is found in the walls of glands and of hollow structures within the body (i.e, the digestive, respiratory, urinogenital & vascular systems), the movements of which are not under voluntary control.
- Spindle shaped cells
What is dimension of smooth muscle cells
Much smaller (only 20-500 mm long) and thinner (~5 mm wide)
What is the function of ciliary muscle?
Change the shape of the lens in the eye to help with focusing
Apart from size and the lack of striations, how else does a smooth muscle cell differ morphologically from a skeletal muscle fibre?
Smooth muscle – single nucleus
Skeletal muscle fibres are cylindrical, multinucleated, striated, and under voluntary control.
Smooth muscle cells are spindle shaped, have a single, centrally located nucleus, and lack striations. They are called involuntary muscles.
Physiologically, how does smooth muscle compare to skeletal muscle
Skeletal muscle is under voluntary control whereas smooth muscle is under involuntary control
What advantages does smooth muscle have over skeletal muscle?
- It uses less energy (which is good as smooth muscle is continuously active) - energy efficient
- Ones does not want to generate a lot of force
- It uses less energy (which is good as smooth muscle is continuously active) - energy efficient
- Ones does not want to generate a lot of force
The strong wave-like motions of the smooth muscle in the esophagus carry the food to the stomach, where it is churned into a liquid mixture called chyme
What type of epithelium lines the oesophagus?
Stratified squamous epithelium
What determines amount of artery surrounding smooth muscle
Type of artery
Property of veins
- Generally have less muscle in their tunica media = Walls are usually thinner
Why do arteries have a smooth muscle component?
This is because they have to carry pumped blood away from the heart to all the organs and tissues that need the oxygenated blood. Maintain and control blood pressure
