Test 6
26. Muscles fibres:
a. have a plasma membrane also known as the sarcolemma 

b. contains sarcoplasm which is rich in potassium, magnesium 
    and phosphate 

c. have invaginations called T-tubules that run parallel to myofibrils 

d. made up of functional units called the sarcomere which lies 
    between 2 successive M-lines

e. are subdivided into myofibrils that contain the filamentous proteins 
    actin and myosin, responsible for muscle contraction 


27. Muscle fibres:

a. can be divided into fast-twitch and slow-twitch fibres dependent 
    on their duration of contraction 

b. of the fast-twitch variety are found in the outer orbital layer 

c. of the slow-twitch variety are found in the outer orbital layer 

d. that are fast-twitch have a larger diameter than slow-twitch fibres 

e. that are fast-twitch derive their energy from aerobic metabolism 
    in the Krebs cycle 

f. that are slow-twitch maintain tonic states of contraction 

g. that are slow twitch are innervated by multiple en grappe nerve 


28. The retina:
a. is divided into the outer pigmented layer and the inner 

b. is embryologically derived from neuroectoderm    

c.  forms the innermost layer of the of the eyeball    

d. is thinnest at the posterior pole and thickens towards the 

e. is related to Bruch’s membrane on its outermost surface   


29. The neural retina:
a. extends from the optic disc periphery posteriorly to the ora 
    serrata anteriorly 

b. is derived from the inner layer of the optic cup 

c. terminates more anteriorly on the temporal side 

d. consists of 8 cellular layers and 2 membranes 

e. is solely supplied with nutrients by the retinal vasculature 


30. With respect to the posterior pole:
a. the macula lutea is 3 disc diameters lateral to the optic disc 

b. the macula lutea is yellow due to beta-carotene, a pigment found 
    in milk and some vegetables 

c. the clivus is the sloping edge of the macula 

d. the ganglion cell layer remains a constant thickness 

e. the foveola is avascular and contains only cone photoreceptors 

f. the fovea remains functional after a central retinal vein occlusion 
   due to its alternative blood supply 

To test 7
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