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Functional Anatomy and Embryology > Muscle And Bone > Flashcards

Muscle And Bone Flashcards

1
Q

4 classes of muscles

A

Cardiac
Smooth
Skeletal
Myoepithelial

All are intermingled with non muscle cells = muscle tissue

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2
Q

Describe the connective tissue in skeletal muscle

A

Epimysium, tough outer layer, surrounds entire muscle
Perimysium, surrounds muscle fibre bundles = fascicles
Endomysium, surrounds each muscle fibre in fasciculus

Blood vessels, nerves embedded in fascia

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3
Q

Describe the connection between muscles and tendons

A

Endo, peri, epimysium merge with dense collagen opus connective tissue of tendon at myotendinous junction
Tendons transmit muscle force to bone, skeleton moves at joints, made of collagen fibres (strong and stiff)

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4
Q

Formation of myotubes

A

Myoblasts proliferate with a growth factor

Myoblasts differentiate and fuse to form a myotube

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5
Q

Describe satellite cells, resident muscle stem cells

A

Found on muscle fibres, mitotically quiescent
Can self renew, maintain stem cell population, myonuclei can’t

Can be activated to enter the cell cycle => myoblasts
Myoblasts proliferate, differentiate
-Provide new myonuclei for existing muscle
-Fuse together to generate new myofibres

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6
Q

Importance of satellite cells

A

Muscle growth after birth
Muscle maintenance
Hypertrophy
Repair and regeneration

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7
Q

Describe the structure of sarcomeres, the contractile unit of skeletal muscle

A 
Myofibrils consist of
-Thick myosin filaments
-Thin actin filaments
This results in their striated appearance
Many myofibrils form a myofibrils
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8
Q

Describe the organisation of sarcomeric organisation

A 
A band, length of myosin
I band, length of actin only
Z line, attachment site of actin
M line, attachment site of myosin
H zone, length of myosin only
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9
Q

How are muscles innervated

A

Myofibres receive innervation from 1 motor neurone
Neuromusclular junction between muscle fibre membrane and nerve
Motor unit = motor neurone contacts many muscle fibres
Larger the motor unit = smaller degree of control and vice versa

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10
Q

Propagation of action potential from motor neurone

A

Action potential spreads along sarcolemma down T tubules

T tubule depolarisation causes the sarcoplasmic reticulum to release Ca2+ which will bind to troponin

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11
Q

Describe cardiac tisssue
Structure
Innervation

A

In heart, pumps blood
Controlled by ANS
Striated with sarcomeric tissue
Cells connected via intercalated discs, form functional syncytial
Fibrous connective tissue rich in blood vessels

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12
Q

Describe the structure of cardiac myocytes

A

Mono/binucleated cells, nucleus centrally located
Striated with sarcomeric structure with intercalated discs, form functional syncytial
Gap junctions allow AP transmission, many mitochondria
Many blood vessels, increased aerobic resp
No satellite cells, no regeneration

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13
Q

Describe smooth muscle
Structure
Innervation

A

In gut walls, blood vessels, resp tract, urogenital tract
Layers of alternating longitudinal, transverse layers of cells
No striations, ANS
Can stretch, maintain tension for long periods of time

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14
Q

Describe the structure of smooth myocytes

A

Spindle shaped cells, unstriated, form functional syncytial
5um diameter, 20-200um in length
Cells twist when contracted
Central mononucleated, innervated by single nerve ending
Surrounded by basal lamina

Small amounts of connective tissue between cells, nerve and vessel passage
Cytoplasm filled with actin filaments, less myosin
Myofilaments loosely organisation, attached to focal densities in cytoplasm and focal adhesion densities at membrane

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15
Q

What are the 2 types of hard connective tissue

A

Cartilage

Bone

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16
Q

Describe hyaline cartilage

A

Fibroblasts in perichondrium, can give rise to chondrocytes in apposition all growth
Chondrocytes in matrix proliferate in interstitial growth

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17
Q

Composition of cartilage
By volume
Organic components

A

Organic 25%
Water 75%
By volume

Collagen II 60%, provides tensile strength
GAG 40%, coupled to proteins => proteoglycans, gives resistance to compression, electro osmotic

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18
Q

Composition of bone (mineralised connective tissue)
By weight
By volume

A

Inorganic 60%
Organic 25%
Water 15%
By weight

Inorganic 36%
Organic 36%
Water 28%
By volume

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19
Q

Bone composition

Inorganic

A

Many hydroxyapatite (Ca10 (PO4)6 (OH)2)

  • Needle like crystals or thin plates
  • 8nm thick, variable length
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20
Q

Bone composition

Organic

A 
90% T1 collagen
Other proteins (osteocalcin, osteopontin, osteonectin, proteoglycans)
21
Q

Properties of cartilaginous matrix

A

Deformable (semi rigid)

Permeable to water and small molecules

22
Q

Properties of bone matrix

A

Rigid

Impermeable

23
Q

Consequences of cartilaginous properties (deformable, water and small molecule permeable)

A

Cartilage can enlarge by both appositional and interstitial growth
Cartilage does not need blood supply, nutrients via diffusion

24
Q

Consequences of the properties of bone matrix (rigid, impermeable)

A

Bone can only enlarge by appositional growth

Bone requires a blood supply

25
Functions of bone
Support Protection System of levers, transformed into body, movements by muscle action Contains bone marrow -Yellow (fat store) Red (haemopoetic, forms blood cells) Reservoir of Ca, PO4 3-, other ions
26
Describe the structure of bone
Outer layer= cortical/compact bone Interior of epiphysis = trabecular bone Articulate surfaces covered by articulate cartilage, no perichondrium Non articulate surfaces covered by periosteum Internal surfaces lined by endosteum Medullary cavity filled with marrow, between trabeculae
27
Describe the Haversian systems
Constructed around central canal 4-20 concentric lamellar, surrounded by cement line of mineralised matrix Canals connected transversely by Volkman’s canals Interstitial lamella between osteons Lacuna found within the concentric lamellae, canaliculi come off lacunae Lacuna contain osteocytes
28
Structure of compact bone
Lamellar - Collagen laid in sheets (5um), alternate orientations - Between sheets of collagen, give increased strength
29
2 major patterns of compact bone
Circumferential, layers surrounding bony surface at periosteum, endosteal surface Haversian system (osteon), small concentric layers around central vascular canal
30
Describe the structure of cancellous (spongy) bone
Supposed lamellar form trabeculae (50um) | Aligned along stress lines, maximises resistance to force, adding minimally to bone mass
31
Types of bone cells
Osteoprogenitor cells (mesenchymal origin) Osteoblasts Osteocytes Bone lining cells Osteoclasts (from haemopoietic stem cells)
32
Describe osteoprogenitor cells
Mesenchymal fibroblast like, stem cell population In trabecular bone, found near blood vessels In compact bone, found at periosteum and endosteum
33
Describe osteoblasts
On bone surface, responsible for steal deposition (component of bone matrix) Extensive RER, Golgi, mitochondria, vesicles Cells have desmosomes, gap junctions
34
Function of osteoblasts
Induce mineralisation through secretion of matrix vesicles | Contain alkaline phosphatase, neutralises inhibitory effects of pyrophosphate on calcium deposition
35
Describe osteocytes
Cell bodies in lacunae, result of mineralisation occurring around Numerous canaliculi, radiate from lacuna, have osteocytes cell processes Nucleus, thin ring of cytoplasm, few organelles, v little cellular activity Processes joined by gap junctions for communication/coordination Canaliculi allow substance diffusion through bone
36
Function of osteocytes
Role of calcium homeostasis Respond to mechanical forces Mediate mechanically adaptive bone remodelling, act as strain receptors
37
Describe the bone lining cells
Undifferentiated, flat Found at bone surface under quiescence (not being remodelled) May represent inactive osteoblasts and have important functions
38
Describe osteoclasts
Involved in bone reabsorption, highly motile Found in reabsorption cavities (Haversian lacunae) on bone surface Variable size/shape, from small mononuclear cells to large (>100um) multinucleated cells Reabsorption contributes to bone remodelling and calcium homeostasis Directly inhibited by calcitonin Parathyroid hormone stimulates osteoblasts to release induces of osteoclasts differentiation
39
Formation of Haversian systems
Osteoclasts tunnel through pre existing bone Tunnel invaded by blood vessels and osteoprogenitor cells Osteoblasts lay down successive bone lamellae on tunnel walls Interstitial systems are remnants of old osteons
40
Step 1 of endochondral ossification | Bone collar formation
Osteoblasts in bone secrete osteoid against diaphysis walls from the primary ossification centre The hyalin diaphysis=encased in compact bone to form the bone collar
41
Step 2 of endochondral ossification | Cavitation
Chondrocytes enlarge and signal for hyalin to calcify into bone Calcified hyalin=impermeable to nutrient diffusion and die Results in cavities for blood vessels
42
Step 3 of endochondral ossification | Periosteum bud invasion
Bud made up of blood vessels and nerves Allows nutrients and osteoblasts, osteoclasts to enter cavities Osteoblasts=secrete osteoid into remaining hyalin to form spongy bone
43
Step 4 of endochondral ossification | Diaphysis elongation
Diaphysis elongates, powered by dicing cells in primary ossification center Elongated region=medullary cavity, bone marrow forms here
44
Step 5 of endochondral ossification | Epiphyseal ossification
Epiphysis develops own ossification center wtith its own periosteal bud Growth plate is between 2 ossification centres
45
Step 1 of intramembranous ossification | Formation of ossification center
Mesenchymal cells from embryonic skeleton differentiate into osteoblasts Osteoblasts secrete osteoid
46
Step 2 of intramembranous ossification | Formation of osteocytes
Osteoblasts secrete osteoid (uncalcified matrix containing collagen precursors) and other organic products Calcified, trapped osteoblasts => osteocytes Osteopenia cells => osteoblasts at the edges of the growing bone
47
Step 3 of intramembranous ossification | Formation of trabecular matrix
Many osteoid clusters unite around capillaries => trabecular matrix Osteoblasts on the surface = cellular layer of periosteum Periosteum secretes compact bone
48
Step 4 of intramembranous ossification | Formation of red bone marrow
Spongy bone crowds around blood vessels | Blood vessels condense into red bone marrow

Functional Anatomy and Embryology (28 decks)

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