Bone structure and core MSK histology Flashcards
what are the 3 types of muscle
skeletal or voluntary
cardiac
smooth
describe skeletal muscle cells
striated
unbranched
multinucleated (forms syncytium)
Nuclei are at the periphery of the fibre, just under the cell membrane (in muscle cells is called the sarcolemma)
how are skeletal muscle fibres grouped ?
Into bundles called fascicles. A muscle typically contains several.
what is the connective tissue which surrounds the skeletal muscle as a whole called?
epimysium
what is the connective tissue which surrounds a single fascile called ?
perimysium
what is the connective tissue which surrounds a single muscle fibre called ?
endomysium
what is this microscope pic of?
striated skeletal muscle
what is the smallest contractile elements in skeletal muscles ‘known as unit of contraction’ called?
sarcomeres
what do sarcomeres form when placed end to end ?
myofibrils
how are myofibrils packed together?
packed together like cigarettes in a pack - in the muscle fibres
what is an unusual feature about skeletal muscles ?
they have mutli nuclei
what does a motor unit consist of ?
One motor neurone and all of the muscle fibres that it innervates (anywhere from a few to more than a hundred fibres).
The axon of the motor neurone branches as it nears its termination and each branch ends in a special type of synapse - what is this synapse called ?
neuromuscular junction
the fewer the numebr of muscle fibres in a motor unit the finer the control of movement (T/F)
true
what are the 3 types of skeletal muscle ?
Type I
Type IIA
Type IIB
describe type I skeletal muscle
Relatively slowly contracting fibres that depend on oxidative metabolism. They have abundant mitochondria, are resistant to fatigue and produce relatively less force. Often called ‘red’ fibres.
describe type IIA muscle fibres
They are relatively fast contracting, but are also reasonably resistant to fatigue. These fibres are relatively uncommon.
describe type IIB muscle fibres
Fast contracting fibres that depend on anaerobic metabolism. They have few mitochondria, fatigue relatively easily and produce relatively greater force. Often called ‘white’ fibres.
describe cartilage in general terms
Semi-rigid and Deformable
Permeable
Avascular
Cells nourished by diffusion through the extracellular matrix.
describe bone in general terms
Rigid
Not Permeable
Cells within the bone must be nourished by blood vessels that pervade the tissue.
what are the cells found within cartilage ?
chondrocytes (chondroblasts when immature)
what is the function of chondrocytes and where are they situated within cartilage
Chondrocytes live within a space in the extracellular matrix termed a lacuna. Chondrocytes are active cells which not only secrete, but also maintain the extracellular matrix around them.
what is the extracellular matrix (ECM) in cartilage comprised of ?
75% water
25% organic material of which - 60% is type II collagen and 40% is proteoglycan aggregates made up of GAG’s - (side note)(most commonly keratan sulfate and chondroitin sulfate) bound to a core protein and often linked to hyaluronan.
what are the 3 different types of cartilage
hyaline, elastic and fibrocartliage
describe hyaline cartilage
it is blue-white in colour and translucent. most common form of cartilage
describe elastic cartilage
light yellow in colour, addition of elastic fibres makes it quite flexible
describe fibrocartliage
Hybrid between tendon and hyaline cartilage. It has bands of densely packed type I collagen interleaved with rows of chondrocytes surrounded by small amounts of cartilagenous ECM. Grossly, fibrocartilage appears white.
give some examples of where hyaline cartilage is found
Articular surfaces
Tracheal rings
Costal cartilage
Epiphyseal growth plates
Precursor in fetus to many bones
identify the letters for the synovial joint in the finger
Note that the gap between the articular cartilages (‘C’) is artifactual. ‘CP’ is the joint capsule, ‘S’ the synovial membrane, and ‘E’ the tendon of the extensor muscle.
what are the functions of bone
Support
Levers for effective movement.
Protection of internal organs (e.g. cranium, ribs)
Calcium store
Haemopoiesis (blood cell production)
what is the composition of bone?
describe the outershell of bone i.e. what makes up the shaft and ends of the bone
An outer shell of dense cortical bone makes up the shaft (diaphysis).
Cancellous or trabecular bone occupies the ends of the bone (the epiphyses). Cancellous bone is a fine meshwork of bone that looks a bit like the inside of an Aero bar.
describe the differences between compact and trabecular bone
Main difference is the presence of spaces (marrow cavities) adjacent to trabecular bone.
what are the living cells called that bone contains ?
osteocytes
how does bone gets its blood supply ?
it is penetratedby small canals for the blood vessels
label the features
describe what cement lines are - found in bone
Often visible surrounding the osteon are termed cement lines. These are only found in osteons that have formed during remodelling.
describe trabecular bone
Trabecular bone has osteocytes and is lamellar in nature, but generally lacks Haversian canals. Because the struts are thin, the osteocytes can survive from contact with the marrow spaces.
Note the pink spaces are bone marrow spaces
describe osteoprogenitor cells ?
located on bone surfaces, for example under the periosteum, these cells serve as a pool of reserve osteoblasts
what are osteoblasts ?
Bone forming cells found on the surface of developing bone. They have plentiful RER and prominent mitochondria.
what are osteocytes ?
a bone cell trapped within the bone matrix.
what are osteoclasts and what are they responsible for ?
Large multinucleated cells. They are found on the surface of bone and are responsible for bone resorption. (reabsorbed)
describe the basics of bone remopdelling
In this process, a number of osteoclasts will congregate and begin to ‘drill’ into the bone, forming a tunnel. A blood vessel will grow into the tunnel bringing with it osteoblasts which line the tunnel and begin laying down new lamellar bone.
prcoess continues until only a haversion canal remains
what is the collection of osteoblasts and osteoclasts that participate in bone remodelling called?
the basic multicellular unit (BMU)
what is the collective term for what osteoblasts secrete called ? and also give a few examples of some of the organis materials it is comprised of
it is called osteoid, contains e.g. collagen, glycosaminoglycans (GAGs) etc
during a brake how does the bone laid down differ from normal lamellar bone?
Because rather than having collagen fibres orientated all in one direction, as occurs in lamellar bone, the collagen fibres are laid down in a haphazard fasion. This type of bone is called woven bone. Woven bone is not as strong and is subsequently remodelled into lamellar bone by being broken down by osteoclasts and reformed by new osteoblasts.
