Histology of musculoskeletal system

Question 1

The extracellular matrix of connective tissue

Answer 1

• contains glycoproteins and glycosaminoglycans
• hydrated gel-filling spaces
• reservoir; interstitial fluid

Question 2

Types of connective tissue fibres

Answer 2

• Collagenous fibres; strong and flexible
• Reticular fibres; type III collagen, delicate and branching
• elastic fibres; elastin

Question 3

Skeletal muscle

Answer 3

• voluntary contraction
• attached to bones and sphincters
• entire muscle covered by epimysium
• subdivided into fascicles and myofibres
• fascicles covered by perimysium
• myofibres surrounded by endomysium

Question 4

Myofibre

Answer 4

• a single cellular unit of skeletal muscle
• multiple cells form one long tube
• multinucleated
• sarcolemma= cell membrane
• peripheral nuclei
• strongly eosinophilic sarcoplasm

Question 5

Types of skeletal muscle fibres

Answer 5

Type I; slow twitch. Lots of capillaries and mitochondria; redder in colour less forceful contractions for longer
Type II; fast twitch. Fewer mitochondria; paler colour

Question 6

Z-line

Answer 6

site of attachment of actin fibres

Question 7

M-line

Answer 7

site of attachment of myosin

Question 8

H- band

Answer 8

section where only myosin present
- pale with dark M-line

Question 9

I- band

Answer 9

only actin is present
-pale with dark z-line

Question 10

A-band

Answer 10

overlapping actin and myosin
- dark region

Question 11

Smooth muscle

Answer 11

• involuntary contraction
• myocytes NOT fibres are spindle-shaped
• no striation
• centrally located nuclei & cigar shaped

Question 12

Function of bone

Answer 12

• shape and support
• protection
• mineral storage
• development & storage of blood cells

Question 13

Bone structure

Answer 13

• hardness; matrix of hydroxyapatites
• strength; collagen
• dynamic
• bone structure is unrelated to mode of development

Question 14

Periosteum

Answer 14

• lines outer surface of all bones
• outer fibrous layer
• inner osteogenic layer
• important role in bone remodelling and fracture repair

Question 15

Osteoid

Answer 15

• extracellular matrix
• 25% water, 25% protein, 50% mineral salts
• organic components; glycosaminoglycans
• inorganic components; hydroxyapatite

Question 16

Name different types of bone cells

Answer 16

• Osteogenic cell
• Osteoblast
• Osteocyte
• Osteoclast

Question 17

Osteogenic cells

Answer 17

• stem cells that form osteoblasts
• osteogenic layer in the periosteum

Question 18

Osteoblasts

Answer 18

• produces osteoid (bone matrix)
• flat; inactive
• teardrop shape; active
• cannot divide

Question 19

Osteocyte

Answer 19

• maintains osteoid matrix
• most abundant
• communicate via stellate process
• cannot divide

Question 20

Osteoclasts

Answer 20

• from hematopoietic cells
• monocyte lineage
• recycles osteoid
• multinucleated
• cannot divide

Question 21

Types of bone

Answer 21

1) Woven (immature); more osteocytes, rapid growth and repair
2) Lamellar (mature); less osteocytes, more organised collagen fibres
2a) Compact bone; dense deposits of matrix
2b) Spongy bone; delicate 3D latticeworks
deposits of matrix

Question 22

Compact bone

Answer 22

• found along outer surface especially diaphysis
• structural unit is an osteon; converts mechanical force into biochemical stimuli
• Haversian canal; central canal for nerves & blood vessels
• lamellae; concentric layers around central canal
• lacunae; spaces between lamellae, osteocytes
• canaliculi; small channels, osteocytes stellate processes
• cement layer; outer limit of osteon
• Volkman canal; transverse connection between adjacent canals

Question 23

Trabecular Bone

Answer 23

metaphysis & epiphysis
- transmits forces from joints to compact bone
- reservoir for calcium & other minerals
- lined by endosteum
- similar structure to compact bone but without central canals
- surrounded by marrow

Question 24

Cartilage cells

Answer 24

• perichondrium lines cartilage except at articular surfaces; outer fibrous, inner chondrogenic layers
• chondroblasts; extracellular matrix become chondrocytes in lacunae
• matrix has more sulfated glycosaminoglycans and proteoglycans are bound to collagen fibrils
• chondrocytes can divide in growing cartilage
• 2-3 daughter chondrocytes= isogenic group

Question 25

Hyaline cartilage

Answer 25

- the most common type of cartilage - glassy appearance of matrix - matrix is semi-solid - contains type II collagen fibrils - Hyaluronic acid, chondroitin sulphate, water

Question 26

Where can you find Hyaline cartilage?

Answer 26

developing vertebrate skeleton, epiphyseal discs, articular cartilages, joints, ribs, nose, larynx, trachea, growth plates

Question 27

Elastic cartilage

Answer 27

- matrix contains meshwork of elastic fibres - found in external ear, epiglottis and larynx

Question 28

Fibrocartilage

Answer 28

- layers of hyaline matrix and dense collagen fibres - type I collagen for strength - groupings of chondrocytes - found in intervertebral discs, joint capsules, ligaments, cardiac skeleton, aponeuroses

Question 29

Functions of the growth plate

Answer 29

- bone is vascular but osteoblasts and osteocytes cannot divide - cartilage has no blood vessels but chondrocytes can divide by mitosis - growth of bones via orderly progression from precursor cartilage at physes.

Question 30

Zones and structure of growth plates

Answer 30

- Zone of reserve cartilage; supplies cells to proliferating layer. Small chondrocytes, lots of matrix - Zone of proliferation; flattened dividing chondrocytes forms columns - Zone of hypertrophy; no cell division, cells swell, less matrix. Hypertrophic chondrocytes die due to lack of blood supply - Zone of calcification; matrix mineralises, blood vessels enter it. Osteoblasts use template to produce osteoid